Subsidy Project of Decommissioning and Contaminated Water Management
Started From FY2021

Development of Support Technology for Integrated
Management of Decommissioning the Fukushima Daiichi
Nuclear Power Station(Development of Continuous Monitoring System in PCV)

Accomplish Report for FY2021

August 2022
International Research Institute for Nuclear Decommissioning(IRID)All rights reserved.
©International Research Institute for Nuclear Decommissioning (IRID)

0(Contents)
1.
2.
3.

4.
5.
6.

No.1

Background and objectives of the research 6. Implementation details (continued)
Research goals
6.2.4 Risk assessment
Implementation items, their co-relation, and6.2.4.1 Settings for environmental changes
relations with other projects
inside the PCV due to operational
3.1 Implementation items for this projectequipment
3.2 Relevance between implementation items
6.2.4.2 Risk assessment procedures
6.2.4.3 Assessment results
3.3 Relation with other projects
Implementation schedule
6.2.5 Organizing specifications for monitoring
Project organization
requirements
Implementation details
6.3 Implementation details (2) : Study of the
6.1 Objectives and goals for each of
Monitoring Methods
implementation detail6.3.1 Study of diversification of monitoring
6.1.1 Technology Readiness Level(TRL)
methods
6.2 Implementation details (1) : Investigation of
6.4 Summary
Monitoring Items Inside the PCV
6.5 Contributions to the recipients of the results
6.2.1 Prerequisites for the study
6.6 Issues
6.2.2 Procedures for extracting important
6.7 Level of achievement relative to the goals
monitoring items in the PCV
6.8 Future plans
6.2.3 Study of the debris retrieval model
6.2.3.1 Study of the Operational Equipment Model
6.2.3.2 Study of the Safety Equipment Model
6.2.3.3 Creation of the debris retrieval model(Note)• In this document, fuel debris may be abbreviated as “debris,” mainly due to limited space for figures and tables on paper.
©International Research Institute for Nuclear Decommissioning1. Background and purpose of the projectNo.2■ Background ① (Summary of Solicitation Application)•

Further increase in the retrieval scale of fuel debris will require more sophisticated monitoring systems toincrease throughput and to support continuity of safe retrieval overview by providing a comprehensive andcontinuous identification of environmental changes inside the PCV where the retrieval operations are taking
place.

•To secure throughput in remote operations under environmental conditions with uncertain elements,
technology is needed to continuously monitor environmental changes inside the PCV over a long period oftime during retrieval.

•

In addition to the above, the development of technology (integrated management support technology (*1))
using the digital twin will be effective in enabling accurate and prompt on-site response by integrating andsharing the acquired monitoring data and operational data, which includes data on troubles, etc., obtained
through actual operation of remote equipment.
(*1) Integrated management support technology is defined as a technology to grasp, whether or not there is adeviation from the expected conditions which include the achievement of safety requirements, by processing data on
the disturbing ensuring throughput. The digital twin is one of the unique technologies similar to this definition.

•

It is necessary to develop a continuous monitoring system inside the PCV as element
technology for long-term support for safe, efficient, and continuous integrated management of
the decommissioning of the Fukushima Daiichi Nuclear Power Station (hereinafter referred to as
the Fukushima Daiichi).

•The development of this technology will be based on the results of the “Development ofTechnology for Further Increasing the Retrieval Scale of Fuel Debris and Reactor Internals.”©International Research Institute for Nuclear Decommissioning1. Background and purpose of the project■ Background ② (What that method should aim forwith respect to changes in risks over time)

Area of unacceptable risks

Risk level

for the long term future

Area in which to determine if it isLowering the level of riskthat the method should
aim forexamining the difficulties

No.3✓ The method must be
designed and modeled to be
acceptable for the time axis
and risk level axis shown in
the figure on the left.
✓ The method must be capableof monitoring the status of
the task and its progressover time.
✓ The method should complete
the primary task in the
shortest time possible, andthe risk level at that timemust be lower than when thetask began.

Unacceptable area

acceptable or not, while carefully

Increased risk level
due to deteriorationof facility and risk
sourcesWidely accepted area

Time
Source: Technical Strategic Plan 2021 for Decommissioning of the Fukushima Daiichi Nuclear
Power Station of Tokyo Electric Power Company Holdings, Inc.

Note: This drawing represents ageneral concept and should be
examined in accordance with thestatus of progress on-site.

Appendix 5 Changes in risk over time Figure A5-1

Each method must advance to the green area by repeating the check items in
the upper right corner before reaching the red/yellow area
©International Research Institute for Nuclear Decommissioning1. Background and purpose of the projectNo.4■ Background ③ (Role of monitoring technology for changes in risk over time)
Maximum value isincreased by internaland external events(approaching the red
area)

Controlling the increasein safety risks

Unacceptable area

Area of unacceptable risks
If thecountermeasure iseffective, theminimum value
decreases(approaching thegreen area)

Risk level

for the long term future

When work delays arecompounded, but has notplunged into the red area(= When the monitoring
system is inadequate,
etc.)

Area in which to determine if it isacceptable or not, while carefully
examining the difficulties

Ensure throughput

Widely accepted area

Start of task

Termination of primary task

Maintained or shortened
as task progresses

If task accumulates,
it takes longerTime

If monitoring technology is introduced to continue
normal work
(The task proceeds without delay, and the actual
performance of the method can be demonstrated)

The monitoring technology will help ensure that the task should not be delayed and the method
used can maintain its original performance (the solid blue line in the above figure). This contributes
to ensuring safety against changes in risk over©Internationaltime Research Institute for Nuclear Decommissioning1. Background and purpose of the project

No.5[Research Objectives (General Overview)]
•

•

•

•

•

This project aims to support the development of technologies contributing to decommissioning and contaminatedwater management of the Fukushima Daiichi Nuclear Power Station (hereinafter referred to as “Fukushima Daiichi
NPS”) of the Tokyo Electric Power Company Holdings, Incorporated (hereinafter referred to as “TEPCO”) based
upon the “Mid-and-Long-Term Roadmap towards the Decommissioning of TEPCO’s Fukushima Daiichi NPS” and“The Development Plan of Decommissioning Research in FY2021” (The 86th Secretariat Teem Meeting forCountermeasures for Decommissioning and Contaminated Water Treatment), so that the decommissioning andcontaminated water management of the Fukushima Daiichi NPS can be implemented smoothly, and to raise thelevel of Japan’s science and technology standard.
The study of general theories unrelated to the method will proceed in FY2021 in order to continuously monitor theenvironmental changes in the Primary Containment Vessel due to further increasing the scale of fuel debris retrieval
operations.
Specifically, this project focuses on investigation, organization and setup of monitoring items considering safety
requirements and task continuity, and conceptual studies of monitoring methods will be conducted and examinedwith consideration of on-site applicability.
Moreover, these conceptual studies, etc, will be explained to the experts appointed by Nuclear Damage
Compensation and Decommissioning Facilitation Corporation (hereinafter referred to as “NDF”) and relevant parties(Ministry of Economy, Trade and Industry, TEPCO, NDF) and their opinions will be sought(*).
In FY2022, the plan will be reviewed based on the opinions received and the status of progress in decommissioning,and candidates for measuring equipment and monitoring sites will be selected. In addition, the operational policies
for the data obtained from monitoring will be studied.

*: In FY2021, NDF received opinions from the “Fuel Debris Retrieval Expert Committee (37th meeting, December 15, 2021)” established and convened by NDF.

The above objectives are detailed on the following pages©International Research Institute for Nuclear Decommissioning1. Background and purpose of the project

No.6■ Details of research objectives (Considerations in conducting research)••

When fuel debris retrieval operations are conducted on-site, not only operational errors byequipment operators and equipment failures but events specific to the Fukushima Daiichi NPS
are also assumed to occur. Research will be conducted based on the idea that these are
disturbing ensuring throughput.
➢ [Assumed Roles of the Operator]
Operator: A person who operates equipment on a panel or terminal following the operation
manualLeader: The team leader of operators. A person who understands the status of the site
and gives instructions to the operators➢ The keyword “accurate and prompt on-site response” in No. 2, is carried out by equipment
operators who work daily in uncertain elements.
Maintaining nuclear safety and ensuring targeted throughput requires a decision-making
process to determine a reliable response to the site conditions based on monitoring data (FACT
data) obtained in the PCV. This will be taken into account in the research.

[Mission and definition of continuous monitoring system inside the PCV in this project]
A system (hereafter referred to as a monitoring system) that collects monitoring data for operators to
respond accurately and promptly on-site and ensure throughput while maintaining safe conditions[The role of this project]
Research results will be provided for the design of fuel debris retrieval methods to be studied for actual onsite response(Specific recipients are shown in No. 15.) ©International Research Institute for Nuclear Decommissioning2. Research goals

No.7■ Goals
Research goals are to prepare development requirements and specifications for
introducing the monitoring system in the design of fuel debris retrieval methods. The
following two goals were established for this, and action items were established toachieve each of these goals.
Goal 1: The requirements and issues for monitoring inside the PCV will beorganized under this project.
Implemented★ Investigation of important monitoring items inside the PCV
in FY2021

Implemented
in FY2022→ Replaced with action item (1) in No. 10 and TRL in No. 20★ Study of monitoring methods to actualize monitoring→ Replaced with action item (2) in No. 11 and TRL in No. 20

Goal 2: The concept of monitoring data operation (specific information
processing and flow of its application) will be studied under this project.
★ It is assumed that three kinds of support are necessary: “operator
Implemented
in FY2022
support, analysis support, and work plan improvement support”→ Replaced with action item (3) in No. 12 and TRL in No. 20

See the next page for how the monitoring system contributes on-site©International Research Institute for Nuclear Decommissioning2. Research goals

Detailed version: Appendix 2-1■ On-site data usage measures
•
•

No.8

Monitoring data obtained on-site can be used for the three supporting technologies shown in the figure below.
Important monitoring items can be applied in “daily operator support” as monitoring data for on-site facilities tocontinue fuel debris retrieval and transfer work.
The monitoring data may be reused in “work plan improvement support” and “analysis support.”
Other monitoring systems[Daily operator support]
Important monitoring
items for continuing
work

Continuous
monitoring system
inside the PCV
Changes in various
equipment
information
due to changes inthe environment in
the PCV

Monitoring datafor on-siteequipment

Operator support
technology
Operational dataset[Annual workplan
improvement
Mid- and long-term
support]work plan data
Work plan updates

Analysis by the
person in charge of
operation support

Leader’s situationalawareness andjudgment

Operator implementation

Evaluation data to
reduce on-site
uncertainty

Debris retrieval activities
using operational
equipment/safety
equipment

Data on daily
task
performance

Reuse of data that canbe applied outside ofoperator support

Analysis by the
person in charge of
operation support

Evaluation data of the matching
characteristics between the midand long-term work plan and theenvironment inside the PCV[Annual analysis
support]task
performancedata©InternationalOther
Research
Institutefor Nuclear Decommissioning2. Research goals

No.9■ Definition of terminology•

The implementation details of this project pertains to risk management. Various technical terms in thisproject were set as follows as conditions for study by referring to ISO 31000 (Risk Management
Guidelines).

Terminology/
Abbreviation

Description

Defined as conditions of operation for fuel debris retrieval. . Conditions in which the safety requirements of the plant,such as the diffusion of radioactive materials are being met, and the fuel debris retrieval and transfer work are
Planned state of fuelprogressing according to plan. In addition, the fuel debris retrieval and transfer work in this project will be carried out
debris retrieval
for 200 days a year (*)(**) in which 300 kg of fuel debris will be transferred in10 hours a day. Maintenance andreplacement of equipment performed outside of these work hours and working days are not included.
Throughput

Ability pertaining to the total amount of fuel debris retrieved during the period from the start to completion of fueldebris retrieval (Retrieval phase with further increase in scale).

Work delay factors(= throughput
disturbing)

Factors that threaten planned state of fuel debris retrieval and worsen throughput. The two main points are as
follows:
Factor ①: Work is delayed due to deterioration of fuel debris retrieval and transfer functions.
Factor ②: Work is delayed due to deterioration of safety function for radiation risks.

Risk

Risk is the effect of uncertainty on the objective of ensuring throughput where the effect is a deviation from theplanned state of fuel debris retrieval.

Risk assessment

A means of determining if the risk is an important monitoring item in the PCV.
The significance of the risk assessment is to substantiate the decision, and the risk assessment includes acomparison of the results of the risk analysis with the risk criteria to determine where further actions should be taken.

(*) This operating condition is an assumed `value (target value).
(**) Depending on the method, fuel debris may be temporarily stored during the day and transferred in batches at night (so-called batch treatment). In this table, the expression is forwhen there is continuous retrieval and transfer.
©International Research Institute for Nuclear Decommissioning3. Implementation items, their co-relation, and relations with other projectsNo.10
3.1 Implementation items for this project■ Implementation item (1): Investigation of monitoring items inside the PCV① Investigation of important monitoring items• To enable operators to respond accurately and promptly on-site, the PCV monitoring items
that lead to work delays are investigated and risk factors are extracted.
• As a method of extracting risk factors, a fuel debris retrieval and transfer process with added
safety functions will be modeled (hereinafter referred to as a debris retrieval model).
• Extracted risk factors are weighted and evaluated in terms of the degree of deviation from theplanned state of fuel debris retrieval (evaluation items: safety, operators, throughput).
② Organizing specifications for monitoring requirements• Based on the results mentioned in ① above, methods of acquiring the required on-site data
will be studied. This study will verify monitoring items that can be measured currently and in
the future, and verify their excesses and deficiencies. The measurement source, range, andaccuracy required for each measurement will also be studied. Here, if ① is found to be
deficient in order, ① is reviewed.
• Based on ① and ② above, the important monitoring items inside the PCV , necessary forthe operators to respond accurately and promptly on-site on a daily basis, are organized.
This investigation will be coordinated with and reviewed in conjunction with the results of thesubsequent implementation details (2) and (3).

Debris retrieval and transfer operations will be modeled, and the requirements
for acquisition of monitoring data to achieve the objectives will be studied©International Research Institute for Nuclear Decommissioning3. Implementation items, their co-relation, and relations with other projectsNo.11
3.1 Implementation items for this project■ Implementation items (2): Study of the monitoring methods① Study of diversification of monitoring measures• When selecting monitoring sites, assume there will be cases where direct monitoring
will be difficult, and include indirect monitoring methods that combine analysis, in the
study.
② Study of installation methods for measuring equipment• Installation methods of measuring equipment must be studied for on-site application of
the methods considered in ① above.
• The penetration usage plans for monitoring equipment, will be studied, taking into
account the constraints of the penetration and the structure of the reactor building.
③ Organization of technological issues• Basic technological issues and development elements are studied, issues are identified
for installation of each measuring equipment to be extracted, and a plan is developed
to resolve the issues (e.g. avoid interfering with fuel debris retrieval related equipment).
• The requirements for the system to collect the measurement data will also be studied.

Specific monitoring methods will be studied and issues will be organized basedon specifications of monitoring requirements©International Research Institute for Nuclear Decommissioning3. Implementation items, their co-relation, and relations with other projectsNo.12
3.1 Implementation items for this project■ Implementation items (3): Study of operational policies for integrated
management support technology① Study of on-site data usage measures• Based on the results of implementation details (1) and (2), the usage
measures for on-site data will be studied to enable operators to respondaccurately and promptly on-site on a daily basis. In addition, in this study, theoperator's point of view is taken into consideration.
② Study of overall treatment process of on-site data *Collaborate with the study of IRID Head Office• Utilizing the results of the study described in ① above, the on-site data
treatment process that assumes on-site operation at the Fukushima Daiichi
will be studied, and the data treatment process of the monitoring system,
which is a part of the integrated management support technology, will be
studied.

How the acquired monitoring data should be used on-site will be studied©International Research Institute for Nuclear Decommissioning3. Implementation items, their co-relation, and relations with other projects
3.2 Relevance between implementation items■ Two-year flow of development
The following is the flow of development based on each of theimplementation details shown in section 3.1.
See Appendix 3.2-1 for those that take iterations associated withdetermining feasibility into account.
Results of the study of subsidized
projects prior to FY2021

Information other thansubsidized projects

No.13(2) Study of the monitoring methods(2)① Study of diversification of monitoringmeasures(2)② Study of installation methods formeasuring equipment[Input examples]- Definition of primary boundary- Fuel debris properties- Work process, etc.

(2)③ Organizing technological issues(1) Investigation of monitoring items inside the PCVCreating a debris retrieval model(1)① Investigationof importantmonitoring items

Output: requirements andissues for monitoring inside
the PCV↑ Equivalent to Goal 1 in No. 7

Extraction of work delay factors/Risk assessment
Deciding on the important monitoring items inside thePCV(1)② Organizing specifications for monitoring
requirements
Implementation details for
FY2021.
A detailed flow of the study
is shown on the next page.

(3) Study of operational policies for integrated
management support technology(3)① Study of measures for on-site data
usage(3)② Study of overall treatment process of on-site
data

Output: operational concepts for monitoring data
↑ Equivalent to Goal 2 in No. 7©International Research Institute for Nuclear Decommissioning3. Implementation items, their co-relation, and relations with other projects
3.2 Relevance between implementation items■ Flow of the study for FY2021

Results of “Development of Technology for Further Increasing the Retrieval Scale of Fuel Debris and Reactor Internals”

Input

Creation of the debris
retrieval model[Results ofmodel
construction]
No. 50 to 51

No. 27 to 41

No. 42 to 49

Operational
equipment model

Safety equipment model

Definition offunctionsDefinition offunctions

Safetyfunctions

Fuel debris retrieval function
No. 37 to 38

No. 39 to 41

Establishment ofdisturbance elements
for fuel debris
retrieval function (*)(*) No input is provided inthis project for disturbancesin the safety equipment
model that correspond toexternal circumstances,such as tsunamis

Functions involved in “disturbing accurate and prompt on-site response” by operators

Extraction of work delay factors/Risk assessment
No. 45, 51 to 53[Examples ofimportantmonitoring
items]
No. 57 to 60

No.14[Procedures for constructing a risk
assessment table] No. 54 to 59[Risk assessment results] No. 60 to 69

Top events that impede “accurate and prompt on-site response” by operators

No. 56 to 58

Weighting in terms of safety, operators and throughput

Defining mechanisms of disturbing

Three supports
were establishedin FY2021

Deciding on the important monitoring
items inside the PCV

Operator support (No. 8)

Analysis support (No. 8)
No.70

Review if inconsistencies occur in risk
assessment details in the weighted evaluation

Work plan improvement
support(No. 8)[Full
implementation in
FY2022] No. 71(1)② Organization of specifications for monitoring
to 72©International Research Institute for Nuclear Decommissioning

requirements, (2) Study of the monitoring methods

3. Implementation items, their co-relation, and relations with other projects
No.15
3.3 Relation with other projects■ Main collaborations with other projects
ID

1

2

Demand-side
project

Provider-side
project

This project- Work plan for inside the PCV
Debris retrieval - Information on additional
project/
equipment installed inside theUpgrading
PCV and in the reactor building
project/- Safety system operation plan
Fundamental- Work plan in the PCV
project/
atmosphere
Safety project/ - Information on additional
Canister project equipment installed inside the
PCV and in the reactor building- Conditions setting for studying
important monitoring items within theinvestigation of monitoring items
inside the PCV- Requirements setting for the studyof diversification of monitoringmeasures within the study of themonitoring methods- Important monitoring items
and monitoring requirements- Operational policies for
integrated management
support technology (monitoring
system)- Capable of establishing andreviewing important monitoring items
for each method.
- Capable of specifying themonitoring technology necessary foreach method.
Details: See Appendix 3.3-1

Debris retrieval
project
Safety project
Canister project

Debris retrieval project
Upgrading project
Fundamental project
Safety project
Canister projectThis project

Concrete actions

Information use: Development of Technology for Further Increasing the Retrieval Scale of Fuel Debris and Reactor Internals: Advancement of Retrieval Method and System for Fuel Debris and Reactor Internals: Upgrading of Fundamental Technology for Retrieval of Fuel Debris and Reactor Internals: Development of Safety Systems: Development of Technologies for Containing, Transfer and Storage of Fuel Debris©International Research Institute for Nuclear Decommissioning4. Implementation schedule

Implementation items
Planning schedule

Actual results(as of the end of FY2021)

FY2021Jun.

1Investigation ofmonitoring items inside
the PCV

Jul.

Aug.

Sep.

Oct.

Nov.

FY2022
Dec.

Jan.

Feb.

Mar.

Apr.

May

Jun.

Jul.

Aug.

Sep.

Oct.

Nov.

Dec.

Jan.

Feb.

Mar.

Apr.

Investigation of monitoring items inside the PCV↑Review ① to ② as applicable, depending on the details ofother studies① Investigation of importantmonitoring items① Investigation ofimportant monitoring
items② Organizing specifications for monitoring requirements② Organizing
specifications formonitoring
requirements

2

No.16

Study of the monitoring
methods

Study of the monitoring methods↑Review ① to ③ as applicable,① Study of diversification depending on the details of otherof monitoring measures
studies)① Study ofdiversification ofmonitoring measures② Study of installation
methods for measuring
equipment② Study of installation methods formeasuring equipment↑ (*1)③ Organization oftechnological issues③ Organization of technological issues↑ (*1)

3

Study of operational
policies for integrated
management support
technology (*2)

Study of operational policies for integrated
management support technology① Study of on-site data usage measures① Study of on-sitedata usage measures② Study of overall
treatment process of
on-site data

*1: Conduct test preparation as needed② Study of overall treatment process of on-site data

*2 Collaborate with the progress in the study IRID Head Office©International Research Institute for Nuclear Decommissioning5. Project organization

No.17
International Research Institute for Nuclear Decommissioning (IRID)(Head Office)Tokyo Electric Power Company Holdings, Inc.

•Coordination of general planning and overall technology management•Coordinate technological management, such as progress in technologicaldevelopment•Coordination for on-site applicability

Toshiba Energy Systems & Solutions (ESS) Corporation

Hitachi-GE Nuclear Energy, Ltd.

(1) Investigation of monitoring items inside the PCV(Coordinate, investigate monitoring items, and review the
implementation details of other companies)(2) Study of the monitoring methods(Coordinate, study monitoring methods, and review the
implementation details of other companies)(3) Study of operational policies for integrated management
support technology (Note 1)(Coordinate, study operational policies for integrated
management support technology,
review the implementation details of other companies)(1) Investigation of monitoring items inside the PCV(Investigate monitoring items, peer review of implementation
details)(2) Study of the monitoring methods(Study monitoring methods, peer review of implementation
details)(3) Study of operational policies for integrated management
support technology (Note 1)(Study operational policies for integrated management support
technology, peer review of implementation details)[Subcontracting details][Subcontracting details]

Design support for the study of monitoring methods(scheduled for FY2022): TBD
Design support for the study of operational policies for
integrated management support technology(scheduled for FY2022): TBD

Design support for the study of monitoring methods(scheduled for FY2022): TBD

Partner development
project teams
Development of safetysystems
Development ofTechnologies for
Containing, Transfer andStorage of Fuel Debris

Development of Fuel
Debris Retrieval
MethodNote 1: The IRID Head Office also organizes study policies concerning (3)Manufacturers, Hitachi GE and Toshiba ESS, engage in this project.
©International Research Institute for Nuclear Decommissioning6. Implementation details 6.1 Objectives and goals for each of implementation detail
No.18
6.1.1 Technology Readiness Level (TRL)
Implementation
details

Targeted effects(Supplemental) TRL definitions

The items that should be monitored inside the PCV(1) Investigation will be investigated, extracted and organized toof monitoringsatisfy safety requirements, such as maintaining
items inside the the confinement function of the PCV during fueldebris retrieval, and monitoring the sub-criticality
PCV
condition.

(Technology Readiness Level (TRL) is not
set because research and organization ofissues for technological development are
different from development items.)(2) Study of themonitoring
methods

Based on the organized results of implementation
details (1), issues must be extracted for the
installation of each measuring equipment formonitoring inside the PCV, and a plan must be
developed to resolve the issues.
(Target TRL upon termination: Level 2)

Development and engineering work is
performed, and the required specifications
are developed in areas where there isalmost no applicable past experience.

(3) Study ofoperational
policies for
integrated
management
supporttechnology

Support items that contribute to integrated
management at the Fukushima Daiichi must be
extracted, based on the results of implementation
details (1) and (2), and on-site usage measures
must be planned.
(Targeted TRL upon termination: Level 1)

Basic requirements and necessary
technologies are identified for the methods
and systems to be developed andengineered.

The TRL indicates why the proposed monitoring items are necessary and how they canbe useful on-site.
©International Research Institute for Nuclear Decommissioning6. Implementation details 6.2 Implementation details (1) : Investigation of Monitoring
Items Inside the PCV
6.2.1 Prerequisites for the study■ Scope of study on the system
Subsystem
Main system•

The figure on the right shows thecorrelation of the flow of materials
such as gas, liquid, and fuel debris in
the overall configuration of the fueldebris retrieval system (*).
* Upgrading of Fundamental Technology for
Retrieval of Fuel Debris and Reactor Internals
project•

The flow of information (data) during
retrieving and transferring fuel debris,and their correlation (IN/OUT) arestudied each of the systems shown in
the figure on the right.

Fuel debris and waste
storage system
Fuel debris
storagesystemWaste
storagesystemFuel debris

Prior to the above, the approach tothe scope of study for this project isshown on the next page.

Sub-subsystem

Primaryboundary

Secondaryboundary

Pathway formaterials

Emergency pathway
for materials

Pathway for
vessels

Environmental control system

Atmosphere

Leakage

Gas phase system

Waste

Gas phase inside
the secondary
boundary

Discharge when the door is opened

In leakExhaustNitrogen

Criticality control
systemEmergency
boric acidsolution
injection system
Boric acidsolution
injection system

Gas phase inside
the primaryboundary

Nitrogeninjection system

Dust

Fuel debris transfer
cell system

Waste waterGas phase particle
removal system

Recirculate

In-building gas
control system

Negativepressurecontrol system

Waste water

Particle-free
Particles removed
air

Gas phase
waste transfer
systemGas discharge
systemDust

Liquid phase system

Water
circulation
systemFuel debris
collection
systemWaste water

Fuel debris
waste
Waste water

Liquid phaseinside the primaryboundary

Circulated
water
Boric acidsolution

Liquid phaseparticle removal
systemFuel debris
collection system
Fuel debris
waste

Waste water

Atmosphericdischarge

Boric acidsolution•

No.19

S/C, D/W
stagnant
water

Fuel debris
transferring
systemVentilation

Fuel debris
transfer system

Surplus waterContaminatedwater treatment
systemParticle-free water
Stagnant water
Emergency
stagnant waterdrainage system

Stagnant waterdrainagesystemParticles removed

Liquid phasewaste transfer
systemStagnant water in the torus room

Liquid phase inside
the secondary
boundary

Groundwater

Dust©International Research Institute for Nuclear Decommissioning6. Implementation details 6.2 Implementation details (1) : Investigation of Monitoring Items Inside the PCV
No.20
6.2.1 Prerequisites for the study■ Scope of study on the system••
Fuel debris and waste
storage system
Fuel debris
storagesystemWaste
storagesystem
Waste

Fuel debris

The approximate scope of study for this project in terms of system configuration is shown in the blue dash box below.
The work delay factors inside the PCV are extracted to study the monitoring requirements of systems and equipment
associated with these factors.
Environmental control system

Atmosphere

Leakage
Gas phase inside
the secondary
boundary

In leak
Nitrogen

NitrogeninjectionsystemCriticality control system
Emergency boric
acid solution
injection system

Recirculate

In-building gas
control system
Boric acid solution
injection system

Negativepressurecontrol system

Gas discharge
systemExhaustGas phase inside
the primaryboundary
Gas phaseparticle removal
systemParticle-free
airFuel debris transfer
cell system
Fuel debris
Waste watercollection
systemDust

Waste waterGas phase
waste transfer
systemWaste water

Circulated water
Boric acidsolution

Boric
acid
solutionContaminatedwater treatment
system•Water
circulation
systemLiquid phaseparticle removal
systemFuel debris
waste

Waste water

S/C, D/W
stagnantwater

Gas phasesystem (inside
the PCV)

Fuel debris
transferring
systemLiquid phasesystem (inside
the PCV)

Ventilation

Fuel debris
transfer system

Surplus waterwill focus on the phenomenaThis project
Stagnantinsidewaterthat occur
thePCV.
Liquidphase
Stagnant water
waste transfer
Emergency
drainage system• waterSystems
related to thephenomena ofstagnantsystemdrainage systeminterest will be added to the study ifnecessary.Stagnant water in the torus room
Particle-free water↑ Modify expressions using thefigure on the left

Fuel debris
collection
systemWaste water

Liquid phaseinside the primaryboundary

Liquid phase system

Fuel debris retrieval
and transfer system(inside the PCV)

Fuel debris
waste

Particles
removed

Dust
Atmosphericdischarge

Focused systems(Add systems in stages asneeded)Discharge when the door is opened

Gas phase system

Particles
removedLiquid phase inside
the secondary
boundary

Groundwater

The scope of study includes
consideration of static
boundary accompanying
deterioration of the PCV
structure

Dust©International Research Institute for Nuclear Decommissioning6. Implementation details 6.2 Implementation details (1) : Investigation of Monitoring Items Inside the PCV

No.21

6.2.1 Prerequisites for the study ■ Scope of primary boundary••

The scope of the primary boundary that has a direct static confinement function for the risk source (fueldebris) utilizes the results of past projects in the figure below.
Boundary definitions established through the project of upgrading of fundamental technology (*) areutilized, taking the unique environment at the Fukushima Daiichi and the fuel debris retrieval methods into
consideration. In this definition, radiation dose area and contaminated area are setup separately based on
the perspective of whether the workers are allowed to enter or not, and four types of areas (red (two types),yellow, and green) resulting from the combination of these two areas are defined.
Secondary boundary (R/B or new building)

Additional radioactive
materials generated* Pressure: approx. -64 Pa

Primary boundary(PCV + Cell, etc.)

PCV* Pressure: Same pressure
as inside the PCV* Pressure: left section+ approximately several
10 Pa* Pressure: left section+ approximately several
10 Pa

Container

Isolation door for emergency
Fuel debris

Excluded from this project because whether it isadopted or not varies depending on the method(*) Project of Upgrading of Retrieval Method andSystem for Fuel Debris and Reactor Internals(**) This project does not expect worker intervention innormal work. Details are presented on the next page

**

Door

Container (shielding, collection)(Operates in a way it does not open at the same time)**: Workers are expected to enter the area for shortperiods of time under normal circumstances: Workers are not expected to enter the area, including in an: Workers are expected to entree for short periods oftime only in case of the emergency: Workers are not expected to enter this area even in worst
case scenario

emergency, but measures should be devised to allow
workers to enter in worst case scenario.

The definitions shown in this figure are considered in the operational equipment model (No. 26) and ultimately included in the debris retrieval©International Research Institute for Nuclear Decommissioning
model (No. 48).

6. Implementation details
No.22
6.2 Implementation details (1) :Investigation of Monitoring Items Inside the PCV
6.2.1 Prerequisites for the study ■ Prerequisites for each system (1/2)• “Safety system” may be abbreviated as “safety equipment” due to space
limitations. “Fuel debris retrieval and transfer system” may be abbreviated as
operational equipment.
• Both operational equipment and safety equipment must be setup and secured
with the defense in depth level 1 to 3 to ensure nuclear safety, according to pastsubsidized projects and preliminary engineering.
• All normal works (excluding maintenance) at work facilities must be remotely
operated. The green area inside the primary boundary shown on the previous
page is an environment that workers can enter at all times, but because thedegree of worker intervention varies depending on the method, a versatile
impact assessment has been deemed difficult.
Prerequisites were determined with the goal of presenting requirements tomaintain the planned state of fuel debris retrieval.
©International Research Institute for Nuclear Decommissioning6. Implementation details
6.2 Implementation details (1) :Investigation of Monitoring Items Inside the PCV
6.2.1 Prerequisites for the study ■ Prerequisites for each system (2/2)

No.23[Scope of study for monitoring items inside the PCV]
• Throughput must be ensured by continuation of the planned state for fuel debris
retrieval. Thus, in this project, the scope of monitoring inside the PCV will focus
on those involved in sustaining normal work(excluding maintenance).
• See Appendix 6.2.1-1 for the contribution of monitoring in accordance with therisk levels of this project.

[Policies for generalization of each system]• In this project, work procedures and equipment configurations for the fuel debris
retrieval methods to be studied in the subsidized project will be investigated,and equipment and work procedures common to each method will be extracted
and organized.

The results of this project will be made more versatile so that all methods canrefer to the results of this project.
©International Research Institute for Nuclear Decommissioning6. Implementation details
6.2 Implementation details (1) :Investigation of Monitoring Items Inside the PCV
6.2.3 Study of the debris retrieval model

No.24■ Requirements for the debris retrieval model
The following two points must be implemented after achieving versatility that does not depend on
the type of method.
• Work delay factors inside the PCV (factors that threaten the planned state of fuel debris retrieval andworsen throughput) must be extracted.
• Along with the above extractions, the equipment related work delay factors must be identified.
■ Policy for representing the debris retrieval model• The policy indicates only the minimum operational and safety equipment to control the fuel debris
and the environment inside the PCV under normal conditions.
• The above equipment must be simplified to deal only with the minimum amount of informationthat shows how the equipment will physically act against the fuel debris and the environment
inside the PCV. In other words, equipment specifications (output, model number, detailed
configuration, etc.) are not set.
■ Policy for configuring the debris retrieval model• In order to understand the movement of materials inside the PCV including fuel debris, thedebris retrieval model must be equivalent to the schematic system drawing.

Debris retrieval model evaluates the impact of operational equipment activities onsafety equipment and defines the correlation between both equipment©International Research Institute for Nuclear Decommissioning6. Implementation details
No.25
6.2 Implementation details (1) : Investigation of Monitoring Items Inside the PCV
6.2.3 Study of the debris retrieval model 6.2.3.1 Study of the operational equipment model■ Study policies• The versatile flow of retrieving and transferring fuel debris that does not depend on methods isdeveloped based on the existing results.
• From the above flow, those with multiple work modes are organized based on the existing results.
• An equipment configuration block drawing is created to crystallize the above flow and to organize theinformation for integrating with the safety equipment model.
■ Input from other projects• Fuel debris properties - Nuclear safety for the Fukushima Daiichi• Fuel debris retrieval method (mainly processing method that is the basis for throughput evaluation)• Fuel debris transfer method (mainly compositional elements of the primary boundary)■ Input from this project• Prerequisites specified in section 6.2.1■ Output from this project• Daily workflow• Equipment configuration block• Equipment operation mode
• Table of safety functions• Table of operational functions

These correlations are
explained on the next pageResearch
for Nuclearprojects
Decommissioning
The operational equipment model will be created based on the©International
results
ofInstituteother6. Implementation details
6.2 Implementation details (1) : Investigation of Monitoring Items Inside the PCV
6.2.3 Study of the debris retrieval model 6.2.3.1 Study of the operational equipment model■ Correlation of output
Fuel debris retrieval andtransfer processes(A) The work is disturbed =Accurate and prompt on-site
response by operators is disturbed.

Table of operational functions
Daily workflow
Start of debris retrieval

Move

Equipment configuration
block
Fuel debris
retrieval andtransfer equipment

Movingmechanism

Functional
requirements

Configurationof components

Designrequirements

Inside the PCVMovingfunctionMovingmechanism

...

...

...

...

Collection
and transfer(B) Functions
necessary to executethe workflow, and“functions defined inthis table” = “functions
involved in disturbing
accurate and prompt
on-site response by
operators”

Equipment operation mode
Processing
mode

Processing

No.26

Cutting

Fuel

Processing
machineCrushing
U-rich mass offuel debris

Collection
equipment...

...
(C) same as (B)

Cell

Table of safety functions
Termination ofdebris retrieval

Table of required
assignment of functions
from Nuclear Safety

Functional
requirements

Configurationof components

Designrequirements

Confinement
Function

Cell

...

...

...

...

©International Research Institute for Nuclear Decommissioning
The above five outputs are described in the following
pages6. Implementation details 6.2 Implementation details (1) :Investigation of
No.27
Monitoring Items Inside the PCV
6.2.3 Study of the debris retrieval model 6.2.3.1 Study of the operational
equipment model(a) Daily workflow• A generic workflow from the start to the termination of fuel debris
retrieval is shown on the next page. This workflow describes theimplementation details for the operators for the on-site equipment
operators. If the operator's work is disturbed, the work will be delayed.
• In this project, in order to prevent work delays, items to be monitored
are extracted for the debris retrieval model by the workflow describedabove. These monitoring items become important monitoring items
inside the PCV.
• This workflow is a model case of continuous fuel debris retrieval andtransfer.
A common operator workflow in each method is developed(see next page)©International Research Institute for Nuclear Decommissioning6. Implementation details
No.28
6.2 Implementation details (1) : Investigation of Monitoring Items Inside the PCV
6.2.3 Study of the debris retrieval model 6.2.3.1 Study of the operational equipment model(a) Daily workflow
Daily workflow (target of study for continuous monitoring project)••

Among the fuel debris retrieval and transfer processes,
the fuel debris retrieval and transfer work were defined
as within the scope of study for the continuous
monitoring project.
In this project, the important items inside the PCV are
extracted in ID: Sa-1 to Sa-10.

Fuel debris retrieval and transfer processes
ID: Ko-1 Start of debris
retrieval
Changes in theenvironment inside the PCV

ID: Ko-2 Verification of removalof interfering objects

ID: Sa-1 Verification of the overall situation inside thePCV, operational equipment, and safety equipment
ID: Sa-2 Approaching the object to be processed
ID: Sa-3 Work prior to debris processing * In this project, neutron
absorbent is sprayed

ID: Sa-4 Processing of debrisWith equipment
operation mode

ID: Sa-5 Various records following processing work
Removal ofinterfering
objectsnoNo interfering objects

yes
ID: Ko-3 Debris retrieval andtransferno[Supplemental information on the useof the word “transfer”]
The process of moving the processedmaterials from the PCV atmosphere(processing site) to the cell is called“transfer” (in the sense of removal)
and the process of moving from inside
the cell to outside the cell is called“transfer” (in the sense of transport).

ID: Ko-4 Are all thedebris transferred?

yes
ID: Ko-5 Termination of Debris
Retrieval

ID: Sa-6 Cell transfer of debris (processing site →collection equipment in red area)
ID: Sa-7 Transfer of debris ① (Red area → Yellow
area)

ID: Sa-8 Collection of debrisWithequipment
operation
mode

ID: Sa-9 Transfer of debris ② (Yellow area → Green area)
ID: Sa-10 Transfer of Debris (green area → secondary
boundary)©International Research Institute for Nuclear Decommissioning6. Implementation details
No.29
6.2 Implementation details (1) :Investigation of Monitoring Items Inside the PCV
6.2.3 Study of the debris retrieval model 6.2.3.1 Study of the operational equipment model(b) Equipment operation mode (fuel debris processing work)■ Study policies• As for “ID: Sa-4 Processing of debris” on the previous page, various processing methods
have been studied in past the Fukushima Daiichi subsidized projects. Since themechanism for work disturbing vary depending on the processing method, the settings forthe operation mode will be adjusted accordingly.
• Specifically, when processing fuel debris, the operation mode is set from the perspectivesof ① Where will the fuel debris be processed?, ② What properties does the fuel debris
have?, ③ How is it processed?, and ④ What is used for collection?
[Fukushima Daiichi subsidized projects used to gather information]• Advancement of Retrieval Method and System for Fuel Debris and Reactor Internals→ Used to collect information for ① and ③ above• Upgrading of Fundamental Technology for Retrieval of Fuel Debris and Reactor Internals→ Used to collect information for ① above• Development of Technology for Fuel Debris Analysis and Characterization→Used to collect information for ② above• Development of Technology for Further Increasing the Retrieval Scale of Fuel Debris andReactor Internals→ Used to collect information for ④ above
Aiming for versatile settings for the operation mode by collecting a wide range of information on©International Research Institute for Nuclear Decommissioning
other R&D projects

6. Implementation details
6.2 Implementation details (1) :Investigation of Monitoring Items Inside the PCV
6.2.3 Study of the debris retrieval model 6.2.3.1 Study of the operational equipment model(b) Equipment operation mode (fuel debris processing work)

No.30■ Summary of study results / Equipment operation mode settings (1/2)••

The results of the settings for ① to ④ on previous page are shown below. See Appendix 6.2.3.1-1
for the basis for these settings.
Combine ① to ④ below for setting equipment operation modes. These combinations will refer tothe details of the study regarding fuel debris processing procedures in the fuel debris retrieval
project.

① Where is fuel debris processed?
(1) In air(2) Underwater② What properties does the fuel debris have?
(3) Nuclear fuel(4) Existing structures (with surface
contamination)(5) U-rich mass of fuel debris(6) Fe-rich mass of fuel debris(7) MCCI formations(8) Others③ How is fuel debris processed?
(9) Crushing(10) Cutting(11) Chipping(12) Picking up④ What is used for collection?
(13) Inner containers and transfer casks*Inner containers refer to unit cans and canisters©International Research Institute for Nuclear Decommissioning6. Implementation details 6.2 Implementation details (1) : Investigation of Monitoring Items
Inside the PCV
No.31
6.2.3 Study of the debris retrieval model 6.2.3.1 Study of the operational equipment model(b) Equipment operation mode (fuel debris processing work) ■ Summary of study results / Equipment operation
mode settings (2/2)••

In air

① Picking up

Innercontainer/transfer cask

② CuttingInner
container/transfer cask

② CuttingInner
container/transfer cask

③ Grinding

Inner
container/transfer cask

④ CrushingInnercontainer/transfer cask

② CuttingInner
container/transfer cask

③ Grinding

Inner
container/transfer cask

④ CrushingInnercontainer/transfer cask

② CuttingInner
container/transfer cask

③ Grinding

Inner
container/transfer cask

② CuttingInner
container/transfer cask

③ Grinding

Inner
container/transfer cask

④ CrushingInnercontainer/transfer cask

OthersSupported by any of ① to ④
above

Inner
container/transfer cask

Fuel debris containing neutron
absorbent

Same as in air

Innercontainer/transfer cask

Fuel

A list of task modes during fueldebris processing is shown.
U-rich mass of fuel debris

There is a possibility that
underwater processing work
may be processed with theapplication of neutron absorbent
as a prerequisite. Accordingly,
since fuel debris change
properties when it contains
neutron absorbent, it was
decided to take into account thefigure on the right in theprocessing mode.

Fe-rich mass of fuel debris

Existing
structures

MCCI formations•

Since the method of debris
processing and the container inwhich the debris is collectedunderwater is no different fromthat in air, the description isomitted in this figure.

Under
water

©International Research Institute for Nuclear Decommissioning6. Implementation details
No.32
6.2 Implementation details (1) : Investigation of Monitoring Items Inside the PCV
6.2.3 Study of the debris retrieval model 6.2.3.1 Study of the operational equipment model(c) Equipment operation mode (fuel debris collection and transfer work)■ Study policies• For “ID: Sa-6 to Sa-10” in No. 28, various fuel debris transfer methods have beenstudied in the past the Fukushima Daiichi subsidized projects. The operation mode is
set by referencing this.
• Specifically, the equipment operation is set up to realize the procedure for transferfrom the primary boundary shown in No. 21.
[Prerequisites for settings]• Negative pressure maintenance equipment inside the PCV and cell is reflected in thesafety equipment model.
• When transferring transfer casks outside the primary boundary, verify that they meetthe on-site transfer criteria (surface contamination/surface dose rate) for the
Fukushima Daiichi. If they do not meet the criteria, decontaminate or return the casks
to cell (Y). In addition, the legally required verification inspection of on-site transfer
criteria for the Fukushima Daiichi must be conducted at the secondary boundary.
• The decontamination site of the transfer casks is assumed to be cell (G) (*).
* Depending on the operational circumstances of the transfer casks in the cell, decontamination sites may be
more reasonable in the cell (Y).
Information on the outcome of past subsidized projects for the Fukushima Daiichi will be gathered to setup theequipment operation modes©International Research Institute for Nuclear Decommissioning6. Implementation details
6.2 Implementation details (1) : Investigation of Monitoring Items Inside the PCV
No.33
6.2.3 Study of the debris retrieval model 6.2.3.1 Study of the operational equipment model(c) Equipment operation mode (fuel debris collection and transfer work)••

The compositional elements of the equipment that transfer fuel debris outside the primary boundary are organized as shown in the
figure below. See Appendix 6.2.3.1-2 for environmental conditions in the cell.
The inner container directly containing the fuel debris is used in the PCV and cell (R), and the fuel debris is collected into a sealed
canister in cell (Y) and capped.
Secondary boundary
Cell
Cell
PCV and cell
(yellow area)(green area)(red area)

Delivery of empty storage containers
Delivery of empty storage containers
Cell transfer
mechanism

Debris collection
mechanism

Intra-cell transfer
mechanism ①

Debrisprocessing
mechanism

Intra-cell transfer
mechanism ②
Decontamination
mechanismCollection mechanism

Transfer cask
(Unconfined state → Capped state)*1

Refers to unit cans and canisters*2

Components involved other than fuel debris are transcribed as “Moving.”

Verification mechanism
before transferringoutside the cell

Door mechanism G/Outside cell

Moving mechanism inside thePCV (*2)

Door mechanism Y/GInner container (*1)
(unconfined state)

Door mechanism R/YFuel debris

Mechanism for transfer
outside the cell

Transfer cask
(Capped state & shielded)
Decontamination water drainage
mechanism©International Research Institute for Nuclear Decommissioning6. Implementation details
6.2 Implementation details (1) : Investigation of Monitoring Items Inside the PCV
6.2.3 Study of the debris retrieval model 6.2.3.1 Study of the operational equipment model

No.34(d) Equipment configuration block
Fuel debris retrieval and transfer system
Safetyequipment
Operational
equipment

Role: Store theprocessed fuel debris
in the canister(unsealed) andtransfer it to the sealed
collection equipment

Debris processing
equipment

Debris processing mechanism (Operation details: make the object being
processed finer)

Role: Process fuel debris
to enable collection intoa canister

Moving mechanism inside the PCV ① (Operation details: move the debris processing mechanism to theobject being processed)

Debris collection
equipment

Radiation source collection mechanism (Operation details: collect the processed material into the innercontainer)
Cell transfer mechanism (Operation details: transfer the inner container to the sealed collection
equipment of the cell)

Sealed collection ofdebris/transferring
equipment

Role: Seal and collecttemporarily stored fueldebris and transfer it outof the primary boundary

Cell (R)

Door mechanism(R/Y)

Cell (Y)Door mechanism(Y/G)
Intra-cell transfer mechanism ① (Operation details: transfer the sealed canister tocell (G))

Inner
container/sealed
canisterContainer sealing mechanism (Operation details: collect the inner container into asealed canister)

Cell (G)••A block diagram of the equipment
configuration that executes each mode ofoperation and daily workflow is shown.
Each equipment shown in this figure has one
or both of the operational and safety functions.

Door mechanism(G/outside the cell)
Intra-cell transfer mechanism ② (Operation details: transfer the sealed canister outof the cell)
Decontamination mechanism (Operation details: decontaminate the sealed
canister)
Decontamination water drainage mechanism (Operation details: drain thedecontamination aid (water) out of the cell)
Verification mechanism before transferring outside the cell (Operation details: verify
contamination and dose in the sealed canister)

Mechanism for transfer
outside the cell
Empty canister delivery
mechanism

This block diagram depicts the connection between equipment, but it is also necessary to connect the equipment to their functions (safety and operational).
©International Research Institute for Nuclear Decommissioning
Defined on the next page and beyond

6. Implementation details
No.35
6.2 Implementation details (1) : Investigation of Monitoring Items Inside the PCV
6.2.3 Study of the debris retrieval model 6.2.3.1 Study of the operational equipment model(e) Table of operational functions••

Setup the operational functions of each equipment shown on the previous page. If operational functions are
disturbed, it will cause work delays.
As shown in the table below and on the next page, “moving function inside the PCV,” “fuel debris
processing function,” “fuel debris collection function,” ”fuel debris packaging function,” “fuel debris transfer
function,” and “empty container delivery function” are classified into six categories.
Table. Debris Retrieval Model Launch Equipment: Table of Operational Functions (1/2)
ID

Functional
requirements

Configuration of components

1

Moving function
inside the PCVMoving mechanism inside the PCV

Equipment with fuel debris processing function must be moved in and out of the RPV
and the pedestal.

Debris processing mechanism(cutting)- Fuel debris must be processed so that it can be appropriately collected into the innercontainer and transfer cask.
- Visual confirmation is needed during processing.

2

3
4
5

Debris processing mechanism
Fuel debris
processing function (chipping)Debris processing mechanism(crushing)Debris processing mechanism(picking up)

Design requirements

Same as above
Same as above
Same as above
Fuel debris must be collected and transferred out of the primary boundary.

6

Inner container(*), transfer cask

8

Radiation source collection
mechanism
Cell transfer mechanism

9

Cell (R)

7

Fuel debris
collection function(*) Inner container is defined in this project as a general term for unit cans and canisters studied in the
Fukushima Daiichi subsidized projects.

Fuel debris must be collected in the inner container.
The inner container must be moved from the fuel debris processing site to cell (R).
There must be a working environment to receive the inner container from the celltransfer mechanism.
©International Research Institute for Nuclear Decommissioning6. Implementation details
No.36
6.2 Implementation details (1) : Investigation of Monitoring Items Inside the PCV
6.2.3 Study of the debris retrieval model 6.2.3.1 Study of the operational equipment model(e) Table of operational functions
Table. Debris Retrieval Model Launch Equipment: Table of Operational Functions (2/2)
ID

Functional
requirements

1011

Fuel debris
packaging
function

Configuration of components

Design requirements

Cell (Y)- There must be a place to receive the inner container from cell (R).
- There must be a working environment for collecting the inner container
into the transfer cask.

Door mechanism (R/Y)

The inner container must have passage from cell (R) to cell (Y).

12

Intra-cell transfer mechanism ① The inner container must be transferred from cell (R) to cell (Y).

13

Collection mechanism

The inner container must be collected into the transfer cask (lid closing).

14

Cell (G)- There must be a working environment to receive the transfer cask
closed by lid from cell (Y).
- There must be a working environment for inspection anddecontamination necessary for the transfer to the secondary boundary.

15

Fuel debris
transfer function Door mechanism (Y/G)

The transfer cask must have passage from cell (Y) to cell (G).

Intra-cell transfer mechanism ② The transfer cask must be transferred from cell (Y) to cell (G).
16
17
18

Mechanism for transfer outside
the cellEmpty container Empty container delivery
delivery function mechanism

The transfer cask must be transferred from cell (G) to the secondary
boundary.
Empty inner containers and transfer casks must be supplied into the cellor PCV atmosphere.
©International Research Institute for Nuclear Decommissioning6. Implementation details
No.37
6.2 Implementation details (1) : Investigation of Monitoring Items Inside the PCV
6.2.3 Study of the debris retrieval model 6.2.3.1 Study of the operational equipment model(f) Table of safety functions■ Reference for the Fukushima Daiichi nuclear safety and safety
requirements• In the Fukushima Daiichi subsidized project “Upgrading of Retrieval Method
and System for Fuel Debris and Reactor Internals,” nuclear safety and safety
requirements were established based on the circumstances unique to the
Fukushima Daiichi. Furthermore, in the Fukushima Daiichi subsidized project“Upgrading of Fundamental Technology for Retrieval of Fuel Debris andReactor Internals,” safety requirements were established with a focus on fueldebris processing.
• The above knowledge will also be utilized in this continuous monitoring
project. Safety requirements for retrieving and transferring fuel debris must be
shared between operational equipment and safety equipment.
• The result of the sharing is shown on the next page.
©International Research Institute for Nuclear Decommissioning6. Implementation details 6.2 Implementation details (1) : Investigation of Monitoring Items Inside the PCV
6.2.3 Study of the debris retrieval model 6.2.3.1 Study of the operational equipment model
No.38(f) Table of safety functions■ Assignment of nuclear safety requirements (1/2)
General safety rules
Nuclear safety(What should beaccomplished)

Basic safety
requirements

Requirements as a safety function (What should be maintained)(When) At what timings do the requests
occur?
[During environmental control inside thePCV]
Gas phase confinement[During environmental control inside the
PCV]
Liquid phase confinement(How) What are the requirements involving specificmeasures?

(Who) Which systems will
respond?

Dust concentration reduction function

Gas phase system

Static boundary function

Gas phase system

Dynamic boundary function

Gas phase system

Discharge control function

Gas phase system

Static boundary function

Gas phase system

Dynamic boundary function

Liquid phase system

PCV/cell damage prevention function

Fuel debris retrieval system[During Processing]
Dust dispersion prevention function
Fuel debris retrieval system
Confinement of Gas phase confinement
radioactive
Static boundary function
Fuel debris transfer system
materials using
Protection of Protection of Prevention
boundaries
people and the publicof[During Transportation]
Static boundary function
Fuel debris transfer system
Confinement
theand theexcessiveGas
phase
confinement
insidetheprimaryofDynamic boundary function
Gas phase system
environment environment discharge
boundary (fuel debris collection/transfer
radioactive
from
from
of
PCV/cell damage prevention function
Fuel debris transfer system
substances
area)
radiation radiation
radioactive[During Transportation]
risks
risks
materials
Liquid phase confinement during transfer
Contaminated water dispersion prevention function Fuel debris transfer systemcask decontamination (water
decontamination)[During transportation] Confinement ofFuel debris transfer system
gas/liquid phase leakage during on-site
Transfer cask confinement function
transfer[During environmental control inside thePrevention of
PCV]
Criticality prevention function
Liquid phase system
additional
nuclear fission Criticality prevention
reactions[During processing] Criticality prevention Fuel debris shape control function
Fuel debris retrieval system(Re-criticality
Fueldebrisshapemaintenancefunction
Fuel debris transfer system
due to abnormal [During Transportation] Criticality
deformation)
prevention
Debris shape maintenance function of transfer cask Fuel debris transfer system©International Research Institute for Nuclear Decommissioning6. Implementation details
6.2 Implementation details (1) : Investigation of Monitoring Items Inside the PCV
No.39
6.2.3 Study of the debris retrieval model 6.2.3.1 Study of the operational equipment model (f) Tableof safety functions•
Refer to Appendix 6.2.3.1-3 for the results of the allocation of components related■ Assignment of nuclear safety requirements (2/2)
General safety rules
Nuclear safety

Preventionof excessive
discharge ofProtection ofradioactive
the public andmaterials
theenvironment
from radiation
risks

radioactive
substances

Requirements as a safety function (What should be maintained)

Basic safety
requirements(What should be accomplished)

Confinement of

to operational equipment responsible for safety functions

Prevention of abnormal
heatup of fuel debris(Revolatilization of(When) At what timings do the requests occur?
[During environmental control inside the PCV]
Prevention of abnormal heatup[During processing] Prevention of abnormal heatup

radioactive materials due
to temperature rise)[During Transportation] Prevention of abnormal heatup(How) What are the requirements involving(Who) Which systems will
respond?

specific measures?
Fuel debris cooling function

Function to prevent excessive heatup of fueldebrisHeat removal function of transfer cask

Prevention of

Liquid phase system/Recirculating cooling system
Fuel debris retrieval system

Fuel debris retrieval system
Fuel debris retrieval

excessive radiation[During processing] External exposure prevention function Shielding function of the cell

exposuresystem/Fuel debris transfer
systemProtection against radiation from Protection against
inside the reactor

external exposure

Protection against radiation fromProtectionof people
and theenvironment from
radiation
risks
Protection ofworkers from

Prevention of excessive radiation
exposure and internal exposureof workers- Radiation exposure associated

Design for dose
reduction of workers

debris retrieval/transfer

classifications to reduce exposure with remote
maintenance and fuel debris on-site transfer lines must be

Operational control fordose reduction of

The operation method, maintenance plan, and task management must be designed for dose reduction.

[During environmental control inside the PCV]

Prevention of fires andexplosions [1] due to retainedhydrogen[1] Hereafter abbreviatedas fire and explosion.

Entire system

workers

Control of hydrogen

people and therisks

Fuel debris transfer system

Appropriate shielding, contamination and dose

establishedProtection of

Daiichi-specific

Transfer cask decontamination function[During Transportation]with fuel debris retrieval/transfer-other than those related to fuelFukushima

Fuel debris transfer systemtransportation- Exposure of on-site workers

from theShielding function of transfer cask

External exposure protection function

radioactive materials during

radiation risks related work

environment[During Transportation]

Prevention of fire and explosion

Oxygen concentration reduction function

Gas phase system

concentration or oxygen [During Transportation]
concentration toPrevention of fire and explosion inside the primary

maintain the lower limit

boundary (fuel debris collection/transfer area)of hydrogen explosion[During Transportation].

Prevention of fire and explosion during on-site transfer

Fire and explosion prevention function of the cellGas phase system

Fire and explosion prevention function fortransfer cask

Fuel debris transfer system©International Research Institute for Nuclear Decommissioning6. Implementation details
6.2 Implementation details (1) : Investigation of Monitoring Items Inside the PCV No.40
6.2.3 Study of the debris retrieval model 6.2.3.2 Study of the safety equipment model(a) Overview of study policies and model■ Study policies• In this project, in order to evaluate the process leading to deviation from theexpected safety conditions and the normal conditions of the fuel debris retrieval
operations, deviation from the normal conditions are defined as conditions inwhich safety functions have been or may be adversely affected. A safety
equipment model is established to identify disturbances that may lead todeviation from the normal conditions.

• In the above evaluation, out of the fuel debris retrieval/transfer operations(disturbances) assumed in the operational equipment model, theoperations that affect the safety functions configured to achieve eachsafety requirement are determined to be risks, and the risks are extracted.
• Therefore, the basic configuration of the safety equipment model consistsof each safety requirement and each safety function to achieve it.
The safety equipment model must be established to extract operational risks that
affect the safety function.
©International Research Institute for Nuclear Decommissioning6. Implementation details
6.2 Implementation details (1) : Investigation of Monitoring Items Inside the PCV No.41
6.2.3 Study of the debris retrieval model 6.2.3.2 Study of the safety equipment model(a) Overview of study policies and model■ Overview of the model (1/2)• Since the safety function is defined as the role of each part in the system, fuel debris retrieval
operations that affect each safety function are studied. To that end, the following environmental
variables (physical quantities) inside the PCV and system design are both defined as elementsthat realize safety functions.
① Environmental variables (physical quantities) inside the PCV for the conditions to beachieved by the safety functions② System design as a means to achieve the safety functions (countermeasures)•

The environmental variables (physical quantities) inside the PCV and the system design are thespecific objects that affect the safety functions for the operations (disturbances) assumed in theoperational equipment model. The system design referred to here refers to equipment anddesign conditions that constitute the safety functions.

•

In addition, there is a correlation between the design values and design conditions of theequipment that constitutes the safety functions among the environmental variables (physicalquantities) inside the PCV and the system design. This is modeled (physical model of theenvironment inside the PCV) and used to determine the transient effects of the disturbancesfrom the operational equipment model.
The methods of realizing the safety functions are “environmental variables inside the PCV” and “system design”©International Research Institute for Nuclear Decommissioning6. Implementation details
6.2 Implementation details (1) : Investigation of Monitoring Items Inside the PCV No.42
6.2.3 Study of the debris retrieval model 6.2.3.2 Study of the safety equipment model(a) Overview of study policies and model■ Overview of the model (2/2)• It is assumed that the operating conditions of the safety equipment model assumed foreach workflow (see next page) will be different.
• Therefore, in order to extract the disturbances by the operational equipment model,
safety functions to achieve each safety requirement and the proposed countermeasuresto achieve the safety functions are organized for each workflow.
• In this project, it is important to establish a process to extract disturbances that affectsafety functions, and it is assumed that there may be multiple candidates forcountermeasure proposals to achieve safety functions that take the method and the onsite environment between units into consideration. Based on the results of the subsidized
projects up to the previous fiscal year, one countermeasure will be selected to conduct
the study in this project.

The safety functions that constitute the safety equipment model for each workflow
must be defined to set the operating conditions of the safety system.
©International Research Institute for Nuclear Decommissioning6. Implementation details
6.2 Implementation details (1) : Investigation of Monitoring Items Inside the PCV
No.43
6.2.3 Study of the debris retrieval model 6.2.3.2 Study of the safety equipment model(b) Relationship with daily workflow of operational equipment model
Workflow
Information on operational equipment model[Workflow (from No.28)](Sa-3) Work
beforeprocessing(Sa-1) Fueldebris retrieval
starts[Source of Disturbance](Sa-4)
Processing

Fe-rich fuel debris(Sa-5) Various
records following
processing(Sa-6) Celltransfer ofprocessedmaterials
Defined in the operational
equipment model

Information on safety equipment
model[Factors affecting
safety functions][Physical quantities
involved]

Change in shapeof debris

Neutron flux

Physical effects

Defined in the operational
equipment model

Set in the safety
equipment model
Generation of dust

Amount of
Dust/concentration

Generation ofcontaminated water
Concentration ofcontaminated water

Control parameters to be set
in the safety equipment model[Operating conditions of safety
equipment (countermeasures)]

Criticality
Gas phase

Disturbance

Liquid phase©International Research Institute for Nuclear Decommissioning6. Implementation details
6.2 Implementation details (1) : Investigation of Monitoring Items Inside the PCV
6.2.3 Study of the debris retrieval model 6.2.3.2 Study of the safety equipment model(c) Definition of safety functions for operational equipment activities;
•
•

No.44

When extracting important monitoring items, the system configuration with safety requirements andsafety functions are defined based on the safety requirements shown in No. 38 and 39.
If multiple system configurations with a single safety function can be identified when considering thenormal operational policies and the diversity of equipment that ensures the safety functions, not all ofthem will be included, but those most likely to become the main proposal in the future will be selectedusing the results of past subsidized projects as reference.
Safety requirements(confinement (gas phase/liquid phase),
criticality, fire and explosion [1])Safety function 1

Safety function 2

Proposed measure 1

Proposed measure 1[1] Fire and explosion

Safety function 3

Proposed measure 1

Proposed measure 2
If there are multiple candidates
as proposed measures, one will
be selected for consideration
based on the results of theprevious year's subsidized
projects.

Proposed measure 3©International Research Institute for Nuclear Decommissioning6. Implementation details
6.2 Implementation details (1) : Investigation of Monitoring Items Inside the PCV
6.2.3 Study of the debris retrieval model 6.2.3.2 Study of the safety equipment model(d) Model Configuration■ Conceptual diagram of safety
equipment model

Safety requirements

No.45

No. 38 to 39

Safety functions
No.46[System Design]
Components comprising the safety functions[Physical environmental model inside the PCV](a) Method forachieving safetyfunctions[Environmental variables inside thePCV (physical quantities)]= Parameters to verify maintenance ofsafety functions (e.g., dust
concentration)

Equipment design values
that constitute safetyfunctions (e.g. filter
efficiency)(a) Method forachieving safetyfunctionscross reference

cross reference

No.46

No.47

cross
reference

Equipment design
conditions that constitutesafety functions (e.g.
relative humidity)

No.46

The physical environmental model inside the PCV is defined as the correlation
Research Institute for Nuclear Decommissioning
between the environmental variables inside the PCV and ©International
the design
conditions

6. Implementation details
6.2 Implementation details (1) : Investigation of Monitoring Items Inside the PCV
No.46
6.2.3 Study of the debris retrieval model 6.2.3.2 Study of the safety equipment model
Note: The system configuration of the safety equipment was based on preliminary(d) Model Configurationengineering information provided by Tokyo Electric Power Company Holdings, Inc. The
information provided is tentative at this time and has not been finalized. In addition, there
are multiple candidates for the system configuration of safety equipment, and one of themwas selected as a representative case for this project.

■ System design•

A gas-phase system is shown as a typical example for design values and design conditions* for equipment andcomponents comprising the safety functions required for the system design. The same settings were used for otherliquid phase/liquid phase criticality/cooldown as well.
* Design conditions are conditions for maintaining design values
Functional
requirements

Configurationof components

Design value

Design conditions(*)

Filter efficiency: 99.999%

HEPA filter inlet relative humidity:
99% or less

Exhauster

Airflow: 3000 m3/h

In-leakage volume: 1000 m3/h
Nitrogen-charged amount: 1000 m3/h
Recirculation airflow: 1000 m3 /hStaticboundary

PCV (Primary
Boundary)

Size of the opening with less than
1000 m3/h in-leakage volume atdifferential pressure of 400 Pa

Primary boundary leakage volume:
Opening with in-leakage volume of 1000 m3/h
or less at differential pressure of 400 Pa

Differential pressure
between inside andoutside of the PCV

Dynamic
boundary

HEPA filter

Filter differential pressure:approximately several hundred Pa

HEPA filter inlet relative humidity:
99% or less

Exhaust fan

Airflow: 3000 m3/h

PCV negative pressure degree: 100 Pa

Differential pressure
between inside andoutside of the PCVHEPA filter

Filter efficiency: 99.999%

HEPA filter inlet relative humidity:
99% or less

HEPA filter
Reduction of
dust
concentration

Discharge
control

Control parameters

Dust concentration inside
the PCV

Exhaust end dust
concentration©International Research Institute for Nuclear Decommissioning6. Implementation details
No.47
6.2 Implementation details (1) : Investigation of Monitoring Items Inside the PCV
6.2.3 Study of the debris retrieval model 6.2.3.2 Study of the safety equipment model(d) Model Configuration■ Physical environmental model inside the PCV
The physical environmental model inside the PCV is broadly classified into the following two
patterns.
See Appendix 6.2.3.2-1 for specific examples of expressions for each pattern(Pattern A)
The PCV environmental model expresses the correlation between the design values and design
conditions of the components that constitutes the safety functions and the PCV environment
variables (physical quantities) (=control parameters) using mathematical formulas. Operations
that affect this correlation are extracted as risks out of the disturbances in fuel debris retrieval
operations.

(Pattern B)
Pattern A is the basic pattern, but if it is difficult to express by a mathematical formula, factorsthat have an adverse effect on environmental variables (physical quantities) (= control
parameters) inside the PCV are organized, and operations that advance these factors are
extracted as risks out of the disturbances in the fuel debris retrieval operations.
The environmental model inside the PCV is expressed by mathematical formulas. If it is difficult to do so, thefactors that adversely affect the control parameters are listed by qualitative expressions©International Research Institute for Nuclear Decommissioning6. Implementation details
6.2 Implementation details (1) : Investigation of Monitoring Items Inside the PCV
No.48
6.2.3 Study of the debris retrieval model 6.2.3.3 Creation of the debris retrieval model
layout diagram was established based on the settings information of the operational equipment model and the safety(a) Equipment layout diagram • Equipment
equipment model.
The system configuration for the safety equipment was established based on the design information provided by the TEPCO
Holdings, Inc. (Note 1 and Note 2).
Sagyou-SeruSagyou-Seru-3
2
Sagyou-Seru-1

Cell (R)Intra-cell transfer
mechanism ①

See Appendix
6.2.3.3-1 for theenvironmental
conditions inside the
PCV.

Sagyou-6← Sagyou-Seru-4
Transfer cask

Sagyou9b

Secondary boundary Sagyou-9
Decontaminationwater drainage
mechanism
Neutron absorbent supply
equipment for processing
work

Anzen-Rin-1

Anzen-Ki-1

Note 2This model isassociated with the
top-extraction method
for convenience of
expression, but theside-extraction
method is also atarget of study. The
actual evaluation isbased on theconditions common toboth methods.

Nitrogen↑ Purified gas↓ PCV atmosphere

Debris

Debris[Detailed configuration of components]
Pretreatment
facility

Electric
heaterAnzen-Ki-2a
Anzen-Ki-2b

Backwash dry
dust collection
equipment

Anzen-Ki-2a-A1 Anzen-Ki-2a-B1 Anzen-Ki-2a-C1
Anzen-Ki-2b-A2 Anzen-Ki-2b-B2 Anzen-Ki-2b-C2

CharcoalfilterCharcoalfilterAnzen-Ki-5a-A1
Anzen-Ki-5b-A2← Sagyou-Seru-5
Sagyou-10

Verification mechanism
before transferringoutside the cell

Anzen-Ki-7a← Sagyou-Seru-6

Anzen-Ki-8a

HEPA
filterExhauster

HEPA
filterExhausterAnzen-Ki-7b

To exhaust
port

Anzen-Ki-8b

Anzen-Ki-4a

HEPA
filterHEPA
filterCharcoalfilterExhauster

Pretreatment
facility

HEPA
filterHEPA
filterCharcoalfilterExhausterD/W stagnant
water coarse
particles
removalequipment

Anzen-Eki-1

Sagyou-8

Anzen-Ki-3a

Anzen-Ki-2b
D/W stagnant
water transfer
pump A/B

Sagyou11

Decontamination mechanism

Pretreatment
facilityAnzen-Ki-2a

Stagnant water

Demister

Sagyou-7

Collection mechanism

Door mechanism Y/GCooling water

Mechanism for transfer
outside the cell

Intra-cell transfer
mechanism ②

Sagyou-5

Sagyou-1

Secondary boundary

Door mechanism
G/Outside cell

Cell transfer
mechanism
Sagyou-4
Inner container(*2)
Sagyou-9a

Fuel debris
processing
mechanism

Cell (G)Cell (Y)C water (de-fueling)
contaminated•Door mechanism R/Y

Note 1- The design
information provided
is tentative at this time
Debris collection
mechanismand not definitive
Sagyou-3
information.
- There are multiple
Sagyou-2
Movingcandidates for systemmechanism
inside the PCV
configuration of thesafety system, andWell
one of them was
Nitrogenselected out of these
Nitrogen
Nitrogenas the representative
supplysystemcase in this project.

Anzen-Eki-2
Anzen-Ki5aAnzen-Ki5b
HEPA
filterAnzen-Ki-5a-B1
Anzen-Ki-5b-B2

Anzen-Ki-3b

Anzen-Ki-4b

PCV stagnant
water buffertank

PCV stagnant water
injection pumpAnzen-Eki-3

Anzen-Eki-4a
PCV stagnant
water discharge
pumpAnzen-Ki-5a

Anzen-Ki-5b

To watertreatment system

Anzen-Ki-6a
To exhaust
port

Anzen-Ki-6b

CoolerAnzen-Eki-5
To watertreatment
systemAnzen-Eki-4b*1 Boundaries in piping
connected to PCV are not shown*2 General term for unit cans andcanisters

To watertreatment
system[The underlined string of characters refers to the model ID]
Equipment related to fuel debris retrieval and transfer system: Sagyou- Arabic
numerals→ What constitutes the cell body: Sagyou-Seru- Arabic numerals
Gas phase System:Anzen-Ki -Arabic numerals
Liquid phase system/Cooldown system: Anzen-Eki-Arabic Numerals
Sub-criticality maintenance system: Anzen-Rin-Arabic numerals

Flow of air
Flow of liquid
Primary boundary (*1)

Important monitoring items are expressed as physical quantities and detection conditions for©International
detectingwork delay factors (=errors)
Research Institute for Nuclear Decommissioningthat occur in any of the following components

6. Implementation details 6.2 Implementation details (1) : Investigation of Monitoring Items Inside the PCV
6.2.3 Study of the debris retrieval model 6.2.3.3 Creation of the debris retrieval model (b) Roadmap of
No.49
environmental changes inside the PCV
Cell (Y)Container sealingmechanism

Nitrogen

Secondary boundary

Cooling water

Neutron absorbent supply
equipment for processing
work

Nitrogen↑ Purified gas↓ PCV atmosphere

DebrisExhauster

HEPA
filterExhauster
To watertreatment system

HEPA
filterCharcoalfilterExhauster

Pretreatment facility

HEPA
filterHEPA
filterCharcoalfilterExhausterD/W stagnant watercoarse particles
removal equipment

PCV stagnant
water buffertank

To exhaust
port

Cooler

PCV stagnant water injectionpump

To watertreatment system

PCV stagnant water
discharge pump

[Detailed configuration of components]
CharcoalfilterPretreatment
facility

To exhaust port

HEPA
filterStagnant water

D/W stagnant
water transfer
pump A/B

HEPA
filterPretreatme
nt facility

Debris

ID: Sa-2 Approaching the object to be processed

Decontaminati
on mechanism
Verification
mechanism before
transferringoutside the cellContaminated water(de-fueling)

Nitrogen

Secondary boundary
Mechanism for transfer
outside the cell

Door mechanism
G/Outside cell

Well
Nitrogen
supplysystemCell (G)Intra-cell transfer
mechanism ②

Intra-cell transfer
mechanism ①

Cell transfer
mechanism

Door mechanism Y/G

ID: Sa-1 Verification of the overall situation inside the PCV, operational
equipment, and safety equipment

Cell (R)
Debris collection
mechanism

Door mechanism R/Y

The “daily workflow” is applied to the equipment layout diagram shown on the previous pageto predict transitional changes in the environment inside the PCV due to the activities of theoperational equipment by utilizing the roadmap method.

To watertreatment system
Flow of air

Electric
heaterDemister(Spraying neutron absorbent on
submerged debris)

HEPA
filterFlow of liquid
Primary boundary(*)*Boundaries in piping connected to the PCV are not shown

Cell (R)

ID: Sa-4 Processing of debris

Debris collection
mechanism

Secondary boundary

Cooling water

Neutron absorbent
supply equipment forprocessing work

Dust
dispersion- Injection ofprocessing aids
(water, abrasives)- Inject antiscattering agent(water spray)- Throwing heat

Dust migrated into
the gas phasemoves outside thepedestal

DebrisD/W stagnant
water transfer
pump A/B

HEPA
filterHEPA
filterExhauster

HEPA
filterExhauster
To watertreatment
systemHEPA
filter

PCV stagnant
water buffertankCharcoalfilterExhauster

CharcoalfilterExhauster

To exhaust
port

Cooler

PCV stagnant water injectionpump

PCV stagnant
water dischargepump

To water treatment
systemCharcoalfilterPretreatment
facility

To exhaust
port

Some airborne dust
reach

D/W stagnant watercoarse particles
removal equipment

Some of the dust
suspended/dissolved in theliquid reach[Detailed configuration of components]

Decontamination
mechanism
Verification
mechanism before
transferring outside
the cellHEPA
filterHEPA
filterPretreatme
nt facility

Pretreatment facility

DebrisContaminated water that
migrated to the liquid phaseleaks into and out of pedestal

Secondary boundary
Mechanism for transfer
outside the cell

Door mechanism G/Outside cell

Door mechanism Y/GNitrogen

Nitrogen

ID: Sa-6 Cell transfer of debris(Processing site → collection equipment in the red area)

Cell (G)Intra-cell transfer
mechanism ②

Container
sealingmechanism

Door mechanism R/Y

Nitrogen
supplysystem

ID: Sa-5 Various records following processing work

Dust adheresin cell (R)Debris iscollected into theinner container

Nitrogen

Cell (Y)Intra-cell transfer
mechanism ①

Cell transfer
mechanism

Dust migrated into
gas phase moves
to cell (R)Contaminated water(de-fueling)

ID: Sa-3 Work prior to debris processing

Charcoalfilter

Backwash dry
dust collection
equipment

To water treatment
systemFlow of air

Charcoalfilter

Backwash dry
dust collection
equipment

Electric
heaterDemister

HEPA
filterFlow of liquid
Primary boundary(*)*Boundaries in piping connected to the PCV are not shown

Cell (R)Cell (Y)

Well
Nitrogen
Nitrogen
supplysystem

ID: Sa-8 Collection of debris

Nitrogen

Resurfacing andsedimentation of dust
settled on the floor

Cooling water↑ Purified gas↓ PCV atmosphere

Debris

ID: Sa-9 Transfer of debris ② (Yellow area → Green area)
ID: Sa-10 Transfer of Debris (green area → secondary
boundary)*This page shows threetransient changes as
examples, but in the actual
study, all task items arecharted. See Appendix
6.2.3.3.-2 and 6.2.3.3-3.

Unsealed debris:
Hydrogen, dust,
radiation generated

Neutron absorbent supply
equipment for processing
work

NitrogenPretreatment
facility

Stagnant water

Pretreatment facility

DebrisD/W stagnant
water transfer
pump A/B

D/W stagnant watercoarse particles
removal equipment

CharcoalfilterPretreatment
facility

Decontamination
mechanism
Verification
mechanism before
transferring outside
the cellHEPA
filterExhauster

HEPA
filterExhauster

To exhaustport

To watertreatment system

HEPA
filterHEPA
filterCharcoalfilterExhauster

HEPA
filterHEPA
filterCharcoalfilterExhauster

PCV stagnant
water buffertank

PCV stagnant
water injectionpump

PCV stagnant
water discharge
pump[Detailed configuration of components]

Secondary boundary
Mechanism
for transfer
outside thecellIntra-cell transfer
mechanism ②

Door mechanism Y/GInflow of residual
dust in the air

Cell (G)Intra-cell transfer
mechanism ①

Door mechanism
G/Outside cell

Door mechanism R/YCell transfer
mechanism

Debris collection
mechanismContaminated water(de-fueling)

ID: Sa-7 Transfer of debris ①(Red area → Yellow area)

To exhaust
port

Cooler
To watertreatment
systemTo watertreatment
systemFlow of air

DemisterElectric
heater

Backwash dry
dust collection
equipment

CharcoalfilterHEPA
filterFlow of liquid
Primary boundary(*)*Boundaries in piping connected to the PCV are not shown

A change in the environment inside the PCV becomes a disturbance to the safety equipment.
disturbancedetails©InternationalSpecificResearch Institutefor Nuclear Decommissioning6. Implementation details
No.50
6.2 Implementation details (1) : Investigation of Monitoring Items Inside the PCV
6.2.4 Risk assessment 6.2.4.1 Settings for environmental changes inside the PCV due tooperational equipment
See Appendix 6.2.4.1-1 for detailed flow of the study(a) Study policies■ Candidates for physical quantities that cause disturbances to safety equipment
Investigation item ①: Dust properties during processing (particle size, mass balance)
Investigation item ②: Amount of processing aid, anti-scattering agent, and heat energy input during processing
Investigation item ③: Amount of neutron absorbent injected during processing and properties of foreign matter (particlesize) during processing
Investigation item ④: Operational parameters of the jig during processing (e.g., cutter rotation speed, blade thickness,
etc.)
Investigation item ⑤: Dust properties during transfer (particle size, mass balance)
Investigation item ⑥: Amount of hydrogen generated from fuel debris during transfer
Investigation item ⑦: Amount of water used during decontamination■ Subject of investigation (IRID project)• FY2018 Subsidized Project “Development of Technology for Dust Collection System of Fuel Debris”• FY2014, 2015, and 2017 Subsidized Project “Development of Technology for Investigation inside the Reactor Pressure
Vessel (RPV)”• FY2014 Subsidized Project “Development of Fundamental Technology for Retrieval of Fuel Debris and Reactor Internals”• FY2016 Subsidized Project “Upgrading of Fundamental Technology for Retrieval of Fuel Debris and Reactor Internals”• FY2018 Subsidized Project “Development of Technology for Retrieval of Fuel Debris and Reactor Internals”■ Subject of investigation (supplementing lack of data in the IRID project)• FY2006 Ministry of Economy, Trade and Industry commissioned investigation “Technical Investigation on Impact
Assessment of Decommissioning Works for Nuclear Power Reactors (Study on Environmental Impact Assessment
Parameters),” Appendix: Handbook on Environmental Impact Assessment for Decommissioning Work (third edition),Central Research Institute of Electric Power Industry, March 2007
• METI, Decontamination Technology Catalogue
https://www.meti.go.jp/earthquake/nuclear/pdf/120626/120626_01j.pdf (URL validity verification date: 2022.8.3)©International Research Institute for Nuclear Decommissioning
Investigation of physical quantities that can possibly cause disturbances
to safety equipment

6. Implementation details 6.2 Implementation details (1) : Investigation of Monitoring Items Inside the PCV
6.2.4 Risk assessment 6.2.4.1 Settings for environmental changes inside the PCV due to operational
No.51
equipment- See Appendix 6.2.4.1-2 for the method used to estimate total amount of dust generated and a(b) Settings for environmental changes inside the PCV table of other changes- See Appendix 6.2.4.1-3 for impact assessment results of static environmental changes for the
PCV■ Table of environmental changes inside the PCV(typical example)
Fueldebristype

Mass offuel debris

Assumed properties
Compressive
Densitystrength
Primary component[g/cm3][MPa]

11[U Rich]Craft, on(U, Zr)O2-C,
bedrock (upper (Zr, U)O2-T,
section): 2000
Other than
[Fe Rich]above
UO2, Fe, Zry-2,
mentioned:α-Zr(O),
230
SUS/Fe,Fe2(Zr, U),
ZrB2, Fe2B, Zr(O),Fe2Zr

1242.1

Processing Equipment
mode
name

Particle size of dust
Aerial processing (no anti-dispersion agent)

Remarks

Blade diameter:
200 mm
Cutting

Airborne

Blade thickness:
Disc cutter 1 mm

All in range of peak particle
size
2 to 3 (mass concentration
distribution)
0.1 to 0.3 (number
concentration distribution)

All in median diameter
Sedimentation 0.3 (number distribution)
7.9 (sediment distribution)
Peripheral
dispersion

Underwater processing

[μm]

---

Number of
revolutions:1000 rpm

---

[μm]

Airborne

Unknown

Sedimentation

Above 50

Either airborne/sedimentation Floating in water 50 or less

Mass balance and amount of dust migration
Aerial processing
Underwater processing
Amount ofAmount of dust
Mass balance
dust
Mass balance
migration
migration

AerialUnderwater
processing processing[g]Localized
area

Pedestal
inside thePCV(floor/inside/o
utside) drywell

Total amount of dust
generated[g]

Assumed processing methods

Amount of processing aid
injected

---

[%]

[g]

---

[%]

[g]

Input materials

Airborne4

49.7

Airborne

2E-05

0.0

[Aerialprocessing]Water: 1 L/min

Sedimentat
ion

37

459.6

Sedimentati
on

99.5

1235.9Peripheral
dispersion

59

732.9

Floating in
water

0.5

6.2

Amount of anti-scattering
agent injected(Only for aerial processing)

Total
Total amount of
Input materials amount of
input
input

198

L

Mist: 0.05 L/min

9.9

L

1242
↑
(*)

↑
(*)

* Of the 10 hours of work hours during the day, the net processing time is deemed to be 3.3 hours

This information is used as a candidate for disturbance to safety equipment (especially the area indicated by the red dashed line) in©International Research Institute for Nuclear Decommissioning
the risk assessment

6. Implementation details 6.2 Implementation details(1) : Investigation of Monitoring Items Inside the PCV
6.2.4 Risk assessment 6.2.4.2 Risk assessment procedures
General composition of OJTWhat is to beachieved and what
is to be protected

Important monitoring items were extracted
from OJT-style methods (top-down) and
FEMA-style methods (bottom-up).
OJT-style evaluation (*1)

[A] Safety requirements/Work requirements(Incorporating inputs based on the results of past subsidized projects)

Input[B] Settings for safety or operational functions applied to each task detail

Input[C] Error mode
Establishment of issues that could possibly affect the required functions(Ex. Sub-criticality maintenance → Debris approaches critical state)

Input[Fuel debris retrieval model]
Table of operational functions, Table ofsafety functions
Equipment layout diagram (similar to P&ID)

Operational equipment model: daily
workflow
Error extraction table: action group sheet- General theory - Environmental physical model- Table of disturbances caused by operational
equipment- Knowledge gained from past subsidized
projects

FMEA type evaluation (*2)

Mechanisms thatlead to issues[D] The settings of mechanisms that degrade safety or
operational functions linked to top events that can occur
under specific operations(Example: Poor visibility due to fog reduces the sub-criticality
maintenance function (debris shape control) of processing
equipment, and processing work take time.)
The detection requirements are directly replaced as importantmonitoring items. Therefore, in addition to the “physical quantity,”
the monitoring items also have the form of expression “modifier +physical quantity.” (e.g. debris temperature unaffected by darkness)

Countermeasures
to prevent
occurrences ofmechanisms thatlead to issues

No.52

Risk Assessment Procedures in Continuous Monitoring Project(Example: The following functions are required during debris processing:
Safety functions: Prevention of dust dispersion, sub-criticality maintenance,
Operational functions: debris processing, debris collection)

Issues to beaddressed•[G'] Detection requirements for avoiding work delays(= Important monitoring items inside the PCV)

Details of [D] to[H] are on thenext page

In order to specialize in extracting important monitoring
items and evaluating superiority and inferiority basedon the premise of equipment and physical values thatcause work delays, shift to FMEA type examination
procedures that allow relative score evaluations[E] Sorting of direct and indirect factors of the events set in the item D[F] Specification of equipment directly involved in the events in
the item D[G] Detection requirement setting for avoiding top events fromoccurring[H1] Assessment of impact onsafety or operational functions[H2] Assessment of
impact on workers[H3] Assessment of
impact on throughput

Importance evaluation*1: OJT is conventionally a safety assessment method for nuclear safety measures developed for each defense indepth level 1 to 3, but in this project, it will be utilized irregularly in order to focus on normal work.
*2: Although FMEA is a design method for predicting failures of compositional elements (equipment) andevaluating their causes and effects, in this project, it is utilized irregularly to identify detection requirements basedon the component of interest /cause and effect of the error.

[I] Completion of weighted evaluation for items in the important©International
Research Institutemonitoring
items for Nuclear Decommissioning6. Implementation details
6.2 Implementation details (1) : Investigation of Monitoring Items Inside the PCV
6.2.4 Risk assessment 6.2.4.2 Risk assessment procedures

No.53■ Input of weightings in the risk assessment table (1/4)•••

The FMEA type evaluation
shown on the previous pageis presented as a risk
assessment table shown on
the right.
Item [H] (weighted
evaluation) on the previous
page is entered in item 7 in
the table. Details are shownon the next page.
Weighting is decided after
verifying the validity as
shown in the flow in thelower right figure.

Item [F] on theprevious page

Item 1

Item 2Item [D] on theprevious page

Item [E] on theprevious page

Item 3Item 4

Safety functions
or operational
Targetfunctions the Work delay factor
equipment target function(= error)is responsibleforDirect causes oferror

Item [E] on theprevious page

Item [G] on theprevious page

Item [H] on theprevious page

Item 5Item 6Item 7

Indirect causes oferror

Detectionrequirements toavoid work
delays

Evaluation
perspectives incontinuous
monitoring
project

HEPA filter Reduction of Acceleration of The effective flow
Partial blockage of Filter differential
Details of thedust
the deterioration path area of thethe filter element due pressure
evaluation areconcentration of dust
HEPA filter isto accumulation of
explained on theconcentration
reduced and the filter dust migrating fromnext page
reduction function performance cannot the processing point
inside the PCV be maintained
to the HEPA filter

Weighted evaluation by item 7

Are they relatively weighted
monitoring items?

No

Yes

Validation of the weighted
evaluation is performed in action
items (1)② and (2)No(1)② Organizing specifications formonitoring requirements(1)② Organizing specifications formonitoring requirements(2) Study of the monitoring methods

Completion of risk assessment results(deliverables)

Item 6 remains
unchanged

Yes
Completion of risk assessment table (deliverable)©International Research Institute for Nuclear Decommissioning6. Implementation details 6.2 Implementation details (1) : Investigation of Monitoring Items Inside the PCV
6.2.4 Risk assessment 6.2.4.2 Risk assessment procedures
No.54■ Input of weightings in the risk assessment table (2/4)
The detection requirements (=important monitoring items) shown in item 6 in the table below are weighted in terms of
Item [H3] on the
Item [H1] on thesafety/operators/throughput as shown in item 7 series.
Item [H2] on theprevious two pages

Item 1

Item 2

Safety functions
or operational
Targetfunctions theequipment target function is
responsible for

HEPA
filterItem 3Item 4Item 5Item 6previous two pages

Item 7-1

Item 7-2

previous two pages

Item 7-3

Detection
Presence or absence of Impact on accurate
Impact on
requirements
Work delay
Direct causes of Indirect causes
countermeasures for and prompt on-sitethroughput by
to avoid work
factor (=error
of error
disturbing safety or
response bycountermeasuresdelayserror)
operational functions
workers
in item 7-1

Reduction of Acceleration The effective flow Partial blockage Filter
dustof thepath area of the of the filter
differential
concentration deterioration HEPA filter iselement due to pressureof dustreduced and the accumulation ofconcentratio filter performance dust migratingn reduction cannot befrom thefunctionmaintained
processing point
inside theto the HEPA
PCV
filterScored from 1 to 4
points(See table below)

Item 7-4

Estimation
results

Product of
Scored from 1 to 4 Scored from 1 to 4
items 7-1 topointspoints
7-3(See table below) (See table below)*The entry details for items 1 to 6 are the same as those on the previous page
■ Score table for item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still
under development[2 points] Countermeasures exist, but there are no
track records of application at the Fukushima Daiichi[1 point] Countermeasures exist, and have been
applied at the Fukushima Daiichi.

■ Score table for Item 7-2 (for safety systems)[4 points] Requires constant monitoring during task
and predictability is poor
[3 points] Requires constant monitoring during task
but predictability is good
[2 points] Requires regular monitoring andpredictability is poor
[1 point] Requires regular monitoring andpredictability is good

■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is unknown[3 points] Countermeasures exist, but throughput decreases significantly due tosuspension of task
[2 points] Countermeasures exist, but throughput decreases due to workload
limitations[1 point] No impact on throughput, or when 7-1 is 1 point■ Score table for item 7-2 (for fuel debris retrieval and transfer
system)[4 points] Cannot be determined directly and there are issues withintroduction[3 points] Cannot be determined directly and can expect
introduction to be feasible[2 points] Can be determined directly and there are issues withintroduction[1 point] Can be determined directly and can expect introduction
to be feasible- Item 7-2 differs in details between the fuel debris retrieval and transfer
system and the safety system. See next page for the reasons- The meaning and handling of the output scores in the evaluation results(Item 7-4) are explained on the following
pages©International
Research Institute for Nuclear Decommissioning6. Implementation details
6.2 Implementation details (1) : Investigation of Monitoring Items Inside the PCV
6.2.4 Risk assessment 6.2.4.2 Risk assessment procedures■ Input of weightings in the risk assessment table (3/4)

No.55~ Concept of weighting ① (Conditions that result in lower scores) ~(Item 7-1) … If countermeasures have already been considered or technologies have been developed for countermeasures, assign lower
scores(Item 7-2) … If the data (mainly digital values) obtained on-site can be easily determined without the need for workers to be proficient,assign lower scores(Item 7-3) … Assign lower scores if there is no impact on throughput.
~ Concept of weighting ② (Reason why item 7-2 is divided between operational equipment and safety equipment) ~•The fuel debris retrieval and transfer system (operational system) must continue to operate in an unclear environment inside the PCV.
Therefore, the focus was placed on the feasibility of monitoring countermeasures to overcome environmental changes inside the PCV(= Are there any issues with introduction?)•
The safety system must cope with transient environmental changes inside the PCV caused by the operational system and theirimpact on the safety functions. Therefore, the focus was placed on whether the cause of deterioration of safety functions (= whether
the predictability is good) is easy to identify.
•
On the other hand, regarding the definition “there are issues with introduction/can expect introduction to be feasible” for the scoresthat were introduced for the operational equipment, the cases of evaluation were defined as follows to avoid discrepancies ininterpretation among evaluators.
There is a possibility of introduction:
Assuming an instrument to be applied to a detection request, direct determination can be made from the instrument’s output (e.g., digital values). In
addition, there are no development issues in utilizing the instrument. (Example: When the detection requirement is the ambient temperature in the PCV:
Assuming that a sheathed thermocouple is used, if the threshold value is set, the digital value output from thermocouple can directly determine if an event
disturbing work is occurring even if the operator is not proficient. In addition, sheathed thermocouples have a track record of application at the Fukushima
Daiichi and there are no development issues.)
There are issues with introduction:
Assuming an instrument to be applied to a detection request, no direct determination can be made from the instrument's output (e.g., digital values). There
are also development issues in utilizing the instrument.
(Example: When the detection requirement is the dimension of debris inside the RPV: Assuming that camera images are used, the operator cannot
directly determine the dimension from the image output from the camera alone. Mechanical treatment support through image processing will be required.
In addition, cameras generally have low radiation resistance, and there are development issues for use in high-dose radiation environment.)©International Research Institute for Nuclear Decommissioning6. Implementation details
6.2 Implementation details (1) : Investigation of Monitoring Items Inside the PCV
6.2.4 Risk assessment 6.2.4.2 Risk assessment procedures■ Input of weightings in the risk assessment table (4/4)

No.56* This project presents indicators from theperspective of ensuring throughput, but there is aneed to take into account the frequency of
disturbing work in the future.

~ Characteristics of the output of scores in items 7-4 ~(Characteristics as a design indicator)• Low scores do not mean that monitoring is unnecessary. The high or low score is one indicator for determining
the degree of focus for each important monitoring item among limited resources (*).
(Characteristics as monitoring system development)• Those with relatively low scores are those where “ Countermeasures are being developed for disturbing work,”“Study of countermeasures has already begun in conceptual design,” and “There is a track record of past
application at the Fukushima Daiichi. or is expected to be applied.”• In other words, those with relatively high scores are likely to be those that have not been fully studied in thecurrent subsidized projects for the Fukushima Daiichi, etc., and are highly likely to require the development ofmonitoring technology.

~ Treatment of items with high scores in items 7-4 ~(Treatment in this project)• The first thing to note as a candidate for important monitoring items to be focused on in the FY2022 research.
• It is possible that those with high scores may drop in scores depending on the hearings for each method (whether
or not there are countermeasures to prevent disturbing work), so their acceptance or rejection will be determined
in FY2022, including corrections to the scores.
(Treatment in each method)• Each method will be the first input to be focused on for studying the introduction of monitoring systems.
• This project proposes a generic risk assessment method that does not depend on specific methods. Therefore,
each method should reevaluate Item 7-4 after reviewing the debris retrieval model with consideration of thecharacteristics
of itsown
method.
Monitoring
items with
low
scores:Monitoring is necessary, but various countermeasures are being studied when

this project is implemented
Monitoring items with high scores: There is a possibility that countermeasures, including monitoring, areinadequate when this project is implemented ©International Research Institute for Nuclear Decommissioning6. Implementation details 6.2 Implementation details (1) : Investigation of Monitoring Items Inside the PCV
6.2.4 Risk assessment 6.2.4.3 Assessment results (a) Important monitoring items
No.57■ Score table for Item 7-1■ Actual details described (gas phase system)[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still underdevelopment[2 points] Countermeasures exist, but have not been applied at
the Fukushima Daiichi[1 point] Countermeasures exist and have been applied to the
Fukushima Daiichi.

Model ID
Process

Ko-3: Debris retrieval

Work

Sa-9

: Transfer of debris ②*1■ Score table for item 7-2[4 points] Requires constant monitoring during task and predictability ispoor[3 points] Requires constant monitoring during task but predictability isgood[2 points] Requires regular monitoring and predictability is poor
[1 point] Requires regular monitoring and predictability is good

See Appendix 6.2.4.3-2 fordetails on this item

*2

Important monitoring items
Item 1

Item 3Item 4Item 5-1

Item 5-2

Item 6-1

Item 6-2

Item 6-3

Work delay
factor (=error)

Direct causes of
error

Indirectcausesof error

Reasons to be
selected

Detectionrequirements toavoid work delays

Directmonitoring/Indirect
monitoring

Reason for selection of
detection requirements

Item 2■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is unknown[3 points] Countermeasures exist, but throughput decreases significantly due tosuspension of task
[2 points] Countermeasures exist, but throughput decreases due to workload limitations[1 point] No impact on throughput, or when 7-1 is 1 point*3

Weighted evaluation of important monitoring items

Item 7-1

Item 7-3

Item 7-2

Item 7-4(Evaluation
Results)

The

Analysis
numberfunctionTargetequipmentthat theThe analysis number is defined target isby the combination of these tworesponsibl
character strings
e for
HEPA filter

Point

Presence or absence ofcountermeasures for
disturbing functions

Impact on

Effects on accurate
Point

and prompt on-sitePointthroughput due toerror handling

response by workers(indirect causes)

Reduction

Acceleratio

The effective

Partial blockage(a) HEPA filter

DirectSelected because

Functionality is ensured byFilter clogging is due

Because item 7-1 isof dustn offlow path area ofof the filter

differential(Item 4)

accumulation of dust in theswitching filters through 2

to daily accumulation,

1 point

concentrati

deterioratio

the HEPA filter iselement due topressure

HEPA filter increases

series of filters (alreadyso predictability isonn of dust

reduced and theaccumulation ofdifferential pressure, andconcentrati

filterdust migrating

this tendency is affected byon

performancefrom thethe amount and particle size

reductioncannot beprocessing point

distribution of the dust

functionmaintained

to the HEPA filter

flowing in.

An-Ki-1①

1

studied)1good(b) Dust amountIndirect

Functionality is ensured byContinuous

PCVand particle size

(item 5)switching filters through 2

monitoring is required,

1

HEPA filter inlet

Same asSame asSame as

above

above

above

Same as above

An-Ki-2[The numbering rules for analysis numbering]Gas phase equipment: Anzen-Ki-Arabic numerals
Liquid phase equipment: An-Eki-Arabic numerals
Cooling equipment: An-Rei-Arabic numerals
Liquid phase sub-criticality maintenanceequipment: An-Rin-Arabic numerals

1

Point
of
repre
senta
tion

1

3

inside the

distribution at the

Indi
vidu
al

series of filters (already3

but predictability is

studied)good.

Because item 7-1 is
1 point
1

3Partial damage(a) HEPA filter

DirectDeterioration of the filter

Functionality is ensured by

Post-detection is

Because item 7-1 isdue to corrosion

upstream/downstr(Item 4)elements due toswitching filters through 2

possible by constant

1 point

of filter elements

eam dust

accumulation of dust in theseries of filters (alreadymonitoring of the dust

by dust migrating

concentration

HEPA filter causes partialfrom processing

ratio

damage of the filter

downstream side ofpoint to HEPA

elements, resulting in a

the filter, butfilterdecrease in the dust

1

studied)4

concentration on the

14Same as(b) Amount of dust

Indirectconcentration ratio between

Functionality is ensured by

predictability is poor
Continuous

Because item 7-1 isabove

and chemical(item 5)the upstream andswitching filters through 2

monitoring is required,1 point

properties at thedownstream sides. Selected

series of filters (alreadybut predictability is

HEPA filter inlet

because this tendency is(pH, chloride ion

affected by the amount andconcentration,

chemistry (pH, chloride ion

chemicalconcentration, and chemicalcomposition)

composition) of the dust

studied)
1

4

poor.
4

1

4

flowing in the filter.

(*1) The name of item 2 is omitted for layout reasons. Formal name: Safety functions or operational functions the target equipment is responsible for(*2) The name of item 7-1 is omitted for layout reasons. Formal name: presence or absence of countermeasures for disturbing safety or operational
functions(*3) The name of item 7-3 is omitted for layout reasons. Formal name: Impact on throughput by countermeasures in item 7-1©International Research Institute for Nuclear Decommissioning6. Implementation details 6.2 Implementation details (1) : Investigation of Monitoring Items Inside the PCV
6.2.4 Risk assessment 6.2.4.3 Assessment results (a) Important monitoring items■ Actual details described (debris retrieval system)
Model ID
KoProcess: Debris retrieval
3Work
Sa-9 : Transfer of debris ②

See *1 on theprevious page

■ Score table for Item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still under development[2 points] Countermeasures exist, but have not been applied at the
Fukushima Daiichi

Item 2Item 3 (excerpt from

■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is unknown[3 points] Countermeasures exist, but throughput decreases significantly due to suspension of task
[2 points] Countermeasures exist, but throughput decreases due to workload limitations[1 point] No impact on throughput, or when 7-1 is 1 point[1 point] Countermeasures exist and have been applied to the
Fukushima Daiichi.

See *2 on theprevious page

Important monitoring items
Item 1■ Score table for item 7-2[4 points] Cannot be determined directly and there are issues with introduction[3 points] Cannot be determined directly and can expect introduction to befeasible[2 points] Can be determined directly and there are issues with introduction[1 point] Can be determined directly and can expect introduction to be feasible

No.58

Item 4Item 5Item 6

See *3 on theprevious page
Weighted evaluation of important monitoring items

Item 7-1

Item 7-2

Item 7-3

error extraction table)

The properties of the

Delay inprocessing

processing

debris are

determining

mechanism

functionincompatible with the

Effects on accurate andprompt on-site response by

Impact on throughput
due to error handlingworkers(Indirect causes)[Items 4/5]

Debris retrieval project is

There is a problem in that

The workload is limited(a) Fuel debris

studying debris processing

the property data necessaryduring sequential

the optimum

properties

methods according to thefor determining the optimum

testing of theprocessing method

processing(compressive

properties of debris (mainly

processing method forprocessing methods inselected, and time is

methodstrength) in thecompressive strength), anddebris is not specified

required to determine

processing area

3

Work

1

Fuel debris
with various
properties

Presence or absence ofcountermeasures for
disturbing functions

is also studying work

the processing

procedures in which

method.

multiple processing

4

except for the compressive

Individual

Debrisfor
Fuel debris

Detection
Indirect causes requirements toof error
avoid work
delaysPoint

is responsible

Direct causesof error

Point

Work delay factor

Point

Sak
u-B-

that the target

Point ofrepresentation

The function
Targetequipment

Applicable
function

Analysis
numberItem 7-4(Evaluation
Results)

24

24

18

18

18

18

item 7-1.
2

strength.

methods are sequentiallytried on a single piece of1debris.
The following methods of- Direct judgment is possible

The throughput will be(a) Dust

general measures willby setting the threshold forsignificantly reduced

concentration at

maintain safety functions,

dust concentration.

because of theto excessive

the processing

but feasibility has not yet- Technology to measure

heatupsite unaffected[Gas phase]

Excessive heatup of

Volatilization

processing

Equipment todebris in the darkof radioactive

mechanism

prevent(poor visibility) andmaterials due

excessive

volatilization ofheatup ofradioactive materials

debris3

by darkness

been evaluated.

2

dust concentration at thecaused by the- Injection of cooling water

dark and high-dosecountermeasures forradiation environment is

Item 7-1.

(b) Debris

by setting the threshold fortemperaturedebris temperature.

darkness3

suspension of work

debris processing site in a

[Item 5]

unaffected byunknown duration of3- Suspension of workrequired.
- Direct judgment is possible

Safety[The numbering rules for analysis]
Safety function related: Saku-A-Arabic
numeralsOperational function related: Saku-B-Arabic
numerals

Excessive
heatup due todarkness (poorvisibility)

SafetySak
u-A-[Item 4]

DebrisSame as above2- When measuring with athermal camera, there is a3

Same as above

problem with radiation
resistance in a high-doseradiation environment.

©International Research Institute for Nuclear Decommissioning6. Implementation details 6.2 Implementation details (1) : Investigation of Monitoring Items Inside the PCV
6.2.4 Risk assessment 6.2.4.3 Assessment results (a) Important monitoring items

No.59■ Important monitoring items of high interest in safety equipment (1/2)• Based on the risk assessment results, the high-profile important monitoring items that have an impact on
throughput (= 2 or more points for item 7-3) and furthermore are items for which countermeasures for operational(safety) functions are still being developed or have not been sufficiently established (= 3 or more evaluation
points for item 7-1) are shown below.
• In the evaluation of the importance of important monitoring items, among the equipment that make up the safetyfunctions, the PCV, which is an existing equipment and constitutes a static boundary, was extracted as having ahigh degree of importance.
• See Appendix 6.2.4.3-1 for a quick reference table of all important monitoring items, and Appendix 6.2.4.3-2 for a
detailed version.
Table. Important monitoring items for the gas phase confinement system during debris processing work (excerpt)
Sagyou-Seru

Debris collection
mechanism
Sagyou-3

Sagyou-2

Inner container (*2)
Sagyou-9a

Movingmechanism
inside the PCV

Fuelprocessing
mechanism

debrisEquipment name

Well

Work delay factors fromwhich monitoring items areset

Important monitoring items for detecting
work delays

Item 7-1

Item 7-3

Differential pressure between inside andoutside of the PCV

4

3Amount and chemical properties (pH,chloride ion concentration) of mist flying to
the PCV wall near the D/W water surface

4

3

Nitrogen
Nitrogen

Nitrogen
supplysystemCoolingwater

Anzen-Ki-1

NitrogenDebris

Debris[Gas phase
confinement
system]PCV[Analysis number: Sa- 4
An-Ki-14, 15]
As the PCV deteriorates
and the size of the PCV
opening increases, leaks
occur inside, and thedifferential pressure
between inside and outsideof the PCV decreases

Weighted evaluationof risk assessment
table

Other monitoring items, including those not listed above, that should be focused on in
FY2022 will be selected.
©International Research Institute for Nuclear Decommissioning6. Implementation details
6.2 Implementation details (1) : Investigation of Monitoring Items Inside the PCV
6.2.4 Risk assessment 6.2.4.3 Assessment results (a) Important monitoring items■ Important monitoring items of high interest in safety equipment (2/2)
•

No.60

Based on the risk assessment results, the typical examples of high-profile important monitoring items that have an impact on
throughput (= 2 or more points for item 7-3) and furthermore are items for which countermeasures for operational (safety) functions
are still being developed or have not been sufficiently established (= 3 or more evaluation points for item 7-1) are shown below.
These will be candidates for important monitoring items to be focused on in next year's research.
See Appendix 6.2.4.3-1 for a quick reference table of all important monitoring items, and Appendix 6.2.4.3-3 for a detailed version.

•

Table. Important monitoring items for operational system during fuel debris processing (excerpt)Moving mechanism
inside the PCV

Well

Fuel debris
processing
mechanism

Equipment
nameWork delay factors from whichmonitoring items are set

Important monitoring items for
detecting work delays

Nitrogen
Coolingwater

Debris

Debris[Debris retrieval
system]Debrisprocessing
mechanism[Analysis number: Sa-4 Saku-B-3]
Processing jigs wear out quickly,
and frequent replacement makeprocessing time-consuming[ Analysis number: Sa-4 Saku-B-7]
Processing results (whether it wasprocessed to the specified size)
cannot be determined due to fog,
and it is time consuming due tohaving to redo the process

Weighted evaluationof risk assessment
table
Item 7-1

Item 7-3

Degree of wear and tear ofprocessing jigs

32Compressive strength of debris to beprocessed

32

Dimensions of processed debris
unaffected by fog

44[Explanation of “Degree of wear and tear of processing jigs”]•
If the technology for immediate replacement of jigs by a tool changer, which is being developed as a separate subsidized project, is applied
on-site, the impact on throughput can be expected to be minimized. The degree of expectations vary depending on the method.
[ Explanation of “Dimensions of processed debris unaffected by fog” ]•It is possible that alternative countermeasures may be necessary depending on site conditions that impede visual inspection.
•
It is necessary to interview other subsidized projects that are considering each method to see if there are any countermeasures, and to
consider how to handle them in FY2022.
©International Research Institute for Nuclear Decommissioning6. Implementation details
6.2 Implementation details (1) : Investigation of Monitoring Items Inside the PCV
6.2.4 Risk assessment 6.2.4.3 Assessment results (b) Overall trends

No.61■ (Reference) Overall results including safety equipment/operational equipment (1/2)••

The details of the factors that disturbe work (= number of errors) and important monitoring items extracted fromthe results of the risk assessment are shown below.
See Appendix 6.2.4.3-4 for the correlation between the debris retrieval model and the risk assessment table.
Item 1
Targetequipment
HEPA
FilterItem 2Item 3Item 4Item 5Item 6Extraction evaluation of important monitoring items

Safety functions oroperational functions
Work delay factor (=the target function iserror)
responsible for
Reduction of dust
Increased dust
concentration
concentration inside the
PCV

Direct causes of error

Indirect causes of error

Detection requirements toavoid work delays

Dust concentration inside the Partial blockage of the filter(a) Filter differential
PCV increases as the HEPA element due to accumulation pressure
filter deteriorates and theof dust migrating from the(b) Dust amount andHEPA filter efficiency does not processing point to the HEPA particle size distribution atmeet the design value.
filterthe HEPA filter inlet
Number of item 6 =Number of importantmonitoring items
In the case of thistable, 2 items

Number of item 3 =number of errors
In the case of thistable, 1 case

Safetyequipment, 116

Operational
equipment, 77

Total number of factors that impede work (errors) extracted(The number in the graph is the number of errors)

Safetyequipment, 94 Operational
equipment, 107

Total number of important monitoring items extracted (*) *Exclude duplicate(The number in the graph is the number of monitoring items) monitoring items

Total number of errors extracted: 193; total number of important monitoring items extracted: 201©International Research Institute for Nuclear Decommissioning6. Implementation details
6.2 Implementation details (1) : Investigation of Monitoring Items Inside the PCV
6.2.4 Risk assessment 6.2.4.3 Assessment results (b) Overall trends

No.62■ (Reference) Overall results including safety equipment/operational equipment (2/2)
The green hatching in
the diagram on theright (equipmentlayout) indicates themain components
affected by factorsthat impede work.

*The underlined character string indicates the model ID
Sagyou-Seru-1

Cell

Sagyou-Seru-2

Sagyou-Seru-3

Cell (Y)Cell (G)Secondary boundary(R)
Cell transfer
mechanism

Debris collection
mechanism
Sagyou-3

Intra-cell transfer
mechanism ①

Fuel debris
processing
mechanism

Sagyou-1

Well

Container sealingmechanism

Sagyou-6← Sagyou-Seru-4
Sealed canister
Sagyou-9b

Nitrogen
Nitrogen
supplysystemNitrogen

Secondary boundary
Cooling water

Sagyou-9
Decontamination waterdrainage mechanism

Anzen-Rin-1

Anzen-Ki-1

Neutron absorbent supply
equipment for processing
work

Nitrogen↑ Purified gas↓ PCV atmosphere

DebrisAnzen-Ki-2a

Sagyou-11

Decontami
nationmechanism← Sagyou- Sagyou-8
Seru-5
Sagyou-10

Anzen-Ki-7a

Anzen-Ki-8a

HEPA filter

ExhausterExhausterAnzen-Ki-7b

Anzen-Ki-8b

Anzen-Ki-4a

Anzen-Ki-5a

Pretreatment
facility

HEPA
filterHEPA
filterAnzen-Ki-2b

Anzen-Ki-3b

Anzen-Ki-4b

CharcoalfilterAnzen-Ki-5b

D/W stagnant
water transfer
pump A/B

D/W stagnant
water coarse
particles removal
equipment

PCV stagnant
water buffertank

PCV stagnant
water injection
pump

CoolerAnzen-Eki-1

Anzen-Eki-2

Anzen-Eki-3

Anzen-Eki-4a

Anzen-Eki-5

PCV stagnant water
discharge pump

To watertreatment
systemCharcoalfilterAnzen-Ki-5a
Anzen-Ki-5b

To exhaust port

HEPA
filterCharcoalfilter[Detailed configuration of components]← Sagyou-Seru-6

Verification mechanism before
transferring outside the cell

HEPA
filterDebrisAnzen-Ki-2a
Anzen-Ki-2b

Mechanism for transfer
outside the cell

HEPA
filterPretreatment
facility

Stagnant water

Pretreatment
facilityAnzen-Ki-3a

Door mechanism Y/GMovingmechanism
inside the PCVDoor mechanism R/Y

Sagyou-2

Intra-cell transfer
mechanism ②
Sagyou-7

Sagyou-5

Door mechanism
G/Outside cell

Sagyou-4
Innercontainer
Sagyou-9a

Contaminated water(decontamination)•

To watertreatment
systemAnzen-Ki-6a
Exhauster

To exhaust port

ExhausterAnzen-Ki-6b

Anzen-Eki-4b
To watertreatment
systemFlow of air
DemisterAnzen-Ki-2a-A1
Anzen-Ki-2b-A2

Electric
heaterAnzen-Ki-2a-B1
Anzen-Ki-2b-B2

Backwash dry
dust collection
equipment

Anzen-Ki-2a-C1
Anzen-Ki-2b-C2

CharcoalfilterAnzen-Ki-5a-A1
Anzen-Ki-5b-A2

HEPA
filterFlow of liquid
Primary boundary (*1)

Anzen-Ki-5a-B1
Anzen-Ki-5b-B2*Boundaries in piping connected to the PCV are not shown

Detailed descriptions of safety equipment and operational equipment are shown on the©International Research Institute for Nuclear Decommissioning
following pages

6. Implementation details
6.2 Implementation details (1) : Investigation of Monitoring Items Inside the PCV
6.2.4 Risk assessment 6.2.4.3 Assessment results (c) Trends in safety equipment

No.63■ (Reference) Overall trends in safety equipment (1/2)••

The figure below shows the number of work delay factors (= errors) and important monitoring items extracted foreach system. The number of errors is highly dependent on the number of equipment that comprise the safetyfunctions.
The number of important monitoring items including direct monitoring items (process changes due to safety
equipment) and indirect monitoring items (environmental changes due to fuel debris retrieval operations) wereorganized so as not to overlap.
Number of errors
Number of importantmonitoring items

Total number of errors: 116
Total number of important monitoring items: 94

Gas phase confinement

Liquid phase confinement

Cooling

Criticality

Gas phase confinement has the largest number of work delay factors and importantmonitoring items©International Research Institute for Nuclear Decommissioning6. Implementation details
6.2 Implementation details (1) : Investigation of Monitoring Items Inside the PCV
6.2.4 Risk assessment 6.2.4.3 Assessment results (c) Trends in safety equipment

No.64■ (Reference) Overall trends in safety equipment (2/2)•••

The results of the weighted evaluation of work delay factors (= errors) extracted in the risk
assessment table are shown.
Even though it is detected that the risk to the safety function has become actualized, if thefeasibility of procedures to maintain the safety function is low, the impact on the safety function
will be large, and similarly the impact on the throughput will be large as well, resulting in ahigher score in the error weighting.
From the above point of view, the score of gas phase confinement was high.

Safety requirements
Gas phase confinement

Weighted evaluation results of errors
Highest score
48

Lowest score
Monitoring
items shownin No.59

1

Liquid phase confinement

4

Cooling43

Criticality prevention

4

3

3

The highest score in the weighted evaluation results were given to the work delay factors
for the gas phase confinement equipment©International Research Institute for Nuclear Decommissioning6. Implementation details
6.2 Implementation details (1) : Investigation of Monitoring Items Inside the PCV
6.2.4 Risk assessment 6.2.4.3 Assessment results (d) Trends in operational equipment

No.65■ (Reference) Overall trends in operational equipment (1/2)
The following figure shows the trends in the extraction of work delay factors (errors) in the fuel debris retrieval and transfer system(Figure below).
[Pattern verified in the overall trends]•
Direct operation on fuel debris (model ID Sa-4) has the largest number of errors extracted.
→ Reason: Dynamic changes in the environment inside the PCV, such as dust dispersion, are conspicuous. This is because theresults (database) of existing subsidized projects are also substantial.
•
The number of errors extracted in the task of collecting fuel debris in a container and transferring it out (Model ID Sa-6 to 9) has
decreased compared to Sa-4.
→ Reason: Separation from the atmosphere inside the PCV due to the cell. Reducing the impact of fuel debris packaging.
Total number of errors: 77

Model ID

Name of work

(Total number of important monitoring items: 107)
Verification
ofthatthe ofoverall→Not shown because the relationship between the number of errors and the number of monitoring items
is similar tosafetysituationequipment

Sa-1
Sa-2

Number of errors

Sa-3
Sa-4
Sa-5

Sa-1

Sa-2

Sa-3

Sa-4

Sa-5

Sa-6

Sa7

Sa8

Sa-9

Sa10

inside the PCV, operational
equipment, and safety equipment
Approaching the object to beprocessed
Work prior to debris processing(spraying neutron absorbent on
submerged debris)

Processing of debris
Various records following processing
work

Sa-6

Cell transfer of debris(Processing site → collection
equipment in the red area)

Sa-7

Transfer of debris ① (Red area →Yellow area)

Sa-8

Collection of debris

Sa-9

Transfer of debris ② (Yellow area →Green area)

Sa-10

Transfer of debris (green area →secondary boundary)

Daily workflow (model ID)©International Research Institute for Nuclear Decommissioning6. Implementation details
6.2 Implementation details (1) : Investigation of Monitoring Items Inside the PCV
6.2.4 Risk assessment 6.2.4.3 Assessment results (d) Trends in operational equipment■ (Reference) Overall trends in operational equipment (2/2)

No.66

•

The results of the weighted evaluation of work delay factors (= errors) extracted in the risk assessment table
are shown.
• The highest score was for the error “It takes time to confirm the fuel debris processing result (fuel debris
shredding completion)” in “Model ID Sa-4: Processing of debris.”
Evaluation results of error weighting (*1)
Model IDWork Name
Highest score
Lowest score
Verification of the overall situation inside the PCV,
Sa-1
operational equipment, and safety equipment
No.60 table
Approaching the object to be processed
Sa-2
91“Dimensions ofWork prior to debris processing
Sa-3
18
12
processed fuelProcessing of debris
Sa-4
64
9
debris unaffected
by
fog,”
etc.
Various records following processing work
Sa-5
Cell transfer of debris
Sa-6(Processing site → collection equipment in the red
9
3
area)
Transfer of debris ①
Sa-7
62(Red area → Yellow area)
Collection of debris
Sa-8
12
4
Transfer of debris ②
Sa-9
4
1(Yellow area → Green area)
Transfer of debris
Sa-10(Green area → Secondary boundary)*1 Quoted scores for item 7-4 in the risk assessment table

The highest score in the weighted evaluation results were given to the work delays during fuel©International Research Institute for Nuclear Decommissioning
debris processing.

6. Implementation details
6.2 Implementation details (1) : Investigation of Monitoring Items Inside the PCV
6.2.5 Organizing specifications for monitoring requirements

No.67

•

An example setting of monitoring requirement specifications for important monitoring items is shown in thetable below.
• The following items, which are generally considered important in terms of instrument selection, wereindividually set for the activities in item (2) “Study of the monitoring methods.”[Monitoring requirement specifications]
Detection location, number of detection points, physical quantity measured, corrosion resistant environment formeasurement instruments, measurement range (approximate), measurement environmental conditions (air doserate, temperature, pressure, humidity), detection accuracy requirements
Importantmonitoring
items

DebrisretrievalsystemGas phase
confinement
systemDetection
location

Number of
detection points

Unit ofCorrosion resistance
Environmental
Required
Approximate
measurrequired byconditions for thedetectionmeasurement range
ement
instruments
measurement
accuracycm
Corrosion due to the
In the criticality project, RPV: Maximum 5000 Gy/h ±1 cm
following components the processing range Temperature: Maximum 50°C
should be considered
per occasion is limited Pressure (gauge pressure):- Chlorine derived from to 16 cm × 16 cm × 16 -2000 to 500 Pa
Humidity: 100% (withseawater
cm cube, so thecondensation)- Boric acid solution
following will be used.
derived from neutron- 1 cm to 30 cm
absorbent- Condensation[Process conditions]Pa
Corrosion due to-2000 to +500Pa±10 Pa
Dose: high radiation
condensation should be
Temperature: 100°C or lessconsidered

Debrisdimensions(duringdebrisprocessing)Debris during Attached to debris
processing
retrieval equipment(RPV, insideand outside of
the pedestal)

Differential
pressure
betweeninside andoutside of
the PCV

Inside andTwo locations (1outside of the inside the PCV / 1
PCV
outside the PCV)
Whether or not tomeasure multiple
locations instead ofjust the representative
points is to be
determined in the
future design stage

Pressure: Atmosphericpressure ±2000 Pa
Humidity: 100% (withcondensation)[Ambient environmental
conditions]
Dose: high radiation
Temperature: 100°C or less
Humidity: 100% (withcondensation)©International Research Institute for Nuclear Decommissioning6. Implementation details 6.3 Implementation details (2) “Study of the Monitoring Methods”
6.3.1 Study of diversification of monitoring methods
•

No.68

It is necessary to consider some of the detection requirement items ,assuming countermeasures on the operational equipment side for the purpose of
avoiding work delays, and to consider replacement and refinement of detection requirements that can support them. An example of operational
equipment is shown below. An example of safety equipment is shown on the next page.
: Debris retrieval: Processing ofdebrisImportant monitoring items
Item 3(excerpt
Item 1
Item 2from error
Item 4Item 5extraction
Analysistable)

ProcessWork

Fall ofdispersed by approaching

sing

processing

processing[Item 5]structure (b) Structural- A technology to prevent re-criticality- The structural strength of structures must be

During the applicationby spraying neutron absorbent

evaluated based on various parameters such asof the neutron

to criticality

strength of(temporary suspension of work) is

defects, strain, stress, and cracks, making directabsorbent, workload

due to shapestructureunder development in the debris

determination difficult.

is limited according to

the allowable change

leading to fall

retrieval project.

- In general industry, there are non-destructive

the countermeasure

dust

mode

- In the debris retrieval project,inspection equipment (ultrasonic wave counter,

concentratio

3

Safety11function

Debris

Impact on throughput
due to error handling(Indirect causes)

concepts such as a support arm that4etc.) for evaluating the structural strength ofn inside thesupports the processed materials andbridges and concrete tunnels, but there are

PCV

a tray that catches falling objects aretechnological issues such as radiation resistancebeing considered to prevent thein high-dose radiation environment and methods

processing area from becoming brittleof application to complex shapes.

2

in item 7-1.

Item 7-4(Evaluation
Results)

Individual

The dust

proces Debris

Effects on accurate and prompt on-site response
by workers

Item 7-3

Point ofrepresentation

Debris [Criticality]

Presence or absence ofcountermeasures for disturbing
functions

Item 7-2

Point

Detection
Indirectrequirements
causesto avoid workof errordelaysItem 7-1

Point

Work delay Direct causes
factorof errornism-A-

Item 6

The function
Target that theequip target isment responsibleformecha shape control approaches
Saku

Weighted evaluation of important monitoring items

Applicable
function
Point

number

Ko-3
Sa-4

24

24

and falling by gravity.

[For operational equipment Model ID “Sa-4: Processing of debris” detection requirement “Structural strength of structure leading to fall mode”(above table)]•
The purpose of avoiding this work delay is to “ascertain whether or not the surrounding structures are likely to fall.” In the above risk assessment table,“Structural strength of structure leading to fall mode” was established as a detection requirement.
•
In general, to evaluate the strength of structures, it is necessary to assume the stress applied on-site against the allowable stress and determine whether
various failure modes such as fracture and fatigue failures occur. Therefore, the data required to satisfy this detection requirement covers a wide range ofdata such as materials, damage conditions, and dimensions, etc. of the structure on-site.
•
On the other hand, in the actual fuel debris retrieval operations, measures to avoid work delays can be considered through hardware design for operational
equipment, such as, “install dedicated arms to support the structure in order to prevent it from falling,” “provide receiving pans and buffer materials to catch
falling structures,” and “spray neutron absorbent around in places where falls are predicted in advance.”•
Therefore, it is necessary to evaluate in FY2022 whether the detection requirement “Structural strength of structure leading to fall mode” is essential ascountermeasures for hardware design as in the above example, and whether it needs to be more detailed, or whether the objective can be achieved even if
another alternative detection requirement is established.

The important monitoring items established in FY2021 include those that need to be modified to support countermeasures against work delays©International Research Institute for Nuclear Decommissioning
executed by operational equipment

6. Implementation details 6.3 Implementation details (2) “Study of the Monitoring Methods”
6.3.1 Study of diversification of monitoring methods① Particle size and amount of dispersion of dust generated during processing

Process

Ko-3: Debris retrieval

Work

Sa-4

: Processing of debris
Important monitoring items

An-Ki-1

Weighted evaluation of important monitoring items

Impact on
throughput due
to errorhandling(Indirect
causes)Individual

Item 3Item 4Item 5-1

Item 5-2

Item 6-1

Item 6-2

Item 6-3

Targetequipment

The functionthat thetarget is
responsibleforWork delay
factor (= error)

Direct causes of
error

Indirectcausesof error

Reasons to be
selected

Detectionrequirements
to avoid work
delaysDirectmonitoring/Indirect
monitoring

Reason for selection of
detection requirements

HEPA

Reduction

Increased

Dust

Partial(a) HEPA

Direct (item 4)

Selected because

Functionality is

Filter clogging is

Becausefilterof dustdust

concentration

blockage offilteraccumulation of dust

ensured by

due to daily

item 7-1 is 1

concentrat

concentration

inside thethe filter

differential

in the HEPA filter

switching filters

accumulation, so

ion

inside thePCVelement duepressure

increases differential

PCV

increases astopressure, and thisof filters (alreadygood

the HEPA

accumulation

tendency is affectedby the amount andstudied)
Functionality is

Continuous

Becauseparticle size

ensured bymonitoring is

item 7-1 is 1

distribution of theswitching filters

required, but

point

dust flowing in.

through 2 series

predictability isdeteriorates①

of dust(b) Dust

migrating fromamountfilter efficiency

the processing and particle
size
point to thedoes not meet

HEPA filter

and the HEPA

distribution

the design

at thevalue.

HEPA filter

Indirect (item 5)

Point

1

1

Item 7-2

Item 7-4(Evaluation
Results)

Item 2filterItem 7-1

Item 7-3

Item 1Analysis
number

No.69

Presence or absenceof countermeasuresfor disturbing
functionsthrough 2 seriesof filters (already

Point

1

3

Effects on accurate
and prompt on-site
response byworkers

predictability is

good.

Point

1

1

point

Point
of
repre
senta
tion

1

3

3

studied)inlet[For safety equipment model ID “Sa-4: Processing of debris” detection requirement “Dust concentration downstreamside of HEPA filter”]• This work delay is based on the assumption that the filter element is partially damaged due to deterioration of the filter
element caused by dust accumulation in the HEPA filter. This work delay can be detected by a decrease in the dust
concentration ratio upstream and downstream.
• This detection is not aimed at predicting failure (i.e., the goal is to detect consequences of damage).
• The reason why this detection goal can be established is that even if the HEPA filter is damaged, backup measures are being
considered for switching filters through 2 series of filters.
• Due to the above, depending on the method, there is a possibility that it may not be necessary to study algorithms forprediction.
There is a need to evaluate the treatment of important monitoring items with such characteristics in the next fiscal year.

Some of those that have backup measures currently in place against disturbing work do not require resourceintensive predictive detections©International Research Institute for Nuclear Decommissioning6. Implementation Details 6.4 Summary

No.70■ Summary of the implementation details for FY2021[Implementation Details (1): Investigation of monitoring items inside the PCV]
① Investigation of important monitoring items• Monitoring items inside the PCV that lead to work delays were investigated, risk factors(= work delay factors) were extracted, and important monitoring items inside the PCV were
established to detect these factors with the objective of enabling operators to respondaccurately and promptly on-site on a daily basis.
• As a method for extracting risk factors, a fuel debris retrieval and transfer process with theadded safety functions were modeled.
• The extracted risk factors were weighted and evaluated in terms of the degree of deviationfrom the planned state of fuel debris retrieval (evaluation items: safety, operators,
throughput).

② Organizing specifications for monitoring requirements• Required on-site data (= physical quantities to be detected) were established for theimportant monitoring items inside the PCV extracted in ① above.
• In addition, the necessary parameters, range, and accuracy for measurements were studied
for each physical quantity.

[Implementation Details (2): Study of the Monitoring Methods]① Study of diversification of monitoring measures• Looking to the next year's study, an initial analysis of important monitoring items was
conducted. The hardware response on the operational equipment side was assumed, andverified the need to consider replacing or refining detection requirements capable of support.
©International Research Institute for Nuclear Decommissioning6. Implementation details
6.5 Contributions to the recipients of the results

No.71• The planned input destination of the final deliverable is as shown in
No.15, but the results of FY2021 will be contributed as follows.
To whom
To operational
equipment to bestudied for eachmethod,To safety
equipment to bestudied for eachmethod,What

In what form

Important monitoring items tocontinue normal work in
response to the risks caused byenvironmental changes inside
the PCV due to fuel debris
retrieval operations

are entered in the report.

Same as above

Same as above©International Research Institute for Nuclear Decommissioning6. Implementation details
6.6 Issues

No.72• As shown in Section 6.2.4.3, it is necessary to select items thatshould be focused on in FY2022 in response to the importantmonitoring items extracted. This issue will be studied in the
Implementation Details (2) : Study of the Monitoring Methods.
• As shown in Section 6.3.1, among the extracted importantmonitoring items, it is necessary to flexibly review them
depending on the content of countermeasures taken byequipment for each method against work delays. This issue will
be studied in the Implementation Details (2) :Study of theMonitoring Methods.

©International Research Institute for Nuclear Decommissioning6. Implementation details
6.7 Level of achievement relative to the goals

No.73■ TRL (reposted from No.18)
Implementation
details(1) Investigationof monitoring
items inside thePCV(2) Study of themonitoring
methods(3) Study ofoperational
policies for
integrated
management
supporttechnology

Targeted effects
Monitoring items that should be monitored inside
the PCV must be investigated, extracted andorganized to satisfy safety requirements
including maintaining confinement function of thePCV during fuel debris retrieval, and monitoring
the sub-criticality condition.
Based on the organized results ofimplementation details (1), issues must be
extracted for the installation of each measuring
equipment for monitoring inside the PCV, and aplan must be developed to resolve the issues.
(Target TRL upon termination: Level 2)
Support items that contribute to integrated
management at the Fukushima Daiichi must be
extracted, based on the results ofimplementation details (1) and (2), and on-siteusage measures must be planned.
(Targeted TRL upon termination: Level 1)(Supplemental) TRL definitions(Technology Readiness Level (TRL) is not set
because research and organization of issues
for technological development are different
from development items.)

Development and engineering work is
performed, and the required specifications
are developed in areas where there is almost
no applicable past experience.

Basic requirements and necessary
technologies are identified for the methods
and systems to be developed andengineered.

In 2021, important monitoring items inside the PCV were extracted
Of the above TRLs, Implementation Details (1) were accomplished on schedule©International Research Institute for Nuclear Decommissioning6. Implementation details
6.8 Future plans

No.74■ Response for FY2022• Based on the input from the results of the risk assessment conducted in
FY2021, “Implementation Details (2) Study of the Monitoring Methods” and“Implementation Details (3) Study of Operation Policies for Integrated
Management Support Technology” will be undertaken according to theinitial schedule.

©International Research Institute for Nuclear DecommissioningSubsidy Project of R&D Program on Decommissioning andContaminated Water Management started in FY2021
Development of Support Technology for Integrated
Management of Decommissioning Fukushima Daiichi Nuclear
Power Station (Development of Continuous Monitoring
System in Primary Containment Vessel)

Accomplishment Report for FY2021~ Appendix ~August 2022
International Research Institute for Nuclear Decommissioning(IRID)All rights reserved.
©International Research Institute for Nuclear Decommissioning (IRID)

75

Appendix 2-1: Monitoring data operational concept (roles of three supporting technologies)••

An example of operational concept of information based on a monitoring system is shown below. Operational data (FACT data) No.76
obtained from the monitoring system is utilized for operator support, analysis support, and work plan improvement support
respectively. As the operation data is accumulated, analysis to reduce uncertainty will be performed to improve the reliability ofthe various support technologies.
Improvements in support technology can contribute to decision-making based on the actual conditions (operating data) on-site
to ensure throughput and to improve daily task procedures or mid- and long-term- work plans.

[Annual analysis support]
Where to apply the
results of action
items (1) and (2)Operating data of otherequipment outside the
PCVMonitoring system(A)[Output of support
technology] Whenthe dust
concentration is in
the range of 〇〇 to△△, the task of theretrieval equipmentis □□□[Leader's Situational Awareness] Example: The
increase in dust concentration during debris processing
is different from usual. Safety is not an issue, butcannot determine if the current task should continue

Manualprovidedmanual, the increase in dust

Switch to the optimum
operation manual by [theleader's discretion][Operator implementation]
Implement the switched operation
manualExample: After switching the operation

Daily task performance(operation data)

concentration was suppressed
Mid- and long-termwork plan data

[Analysis by the person in charge of operation support]
Example. FACT data pertaining to elevated dust
concentration have been sufficiently collected to replace thehypothetical data. The analysis support system suggests it ispossible that the operating parameters of the current air
conditioning equipment may exceed the control value[Daily operator
support]Monitoring data for on-site equipment

Hypothetical data (uncertainty) tocompensate for missing FACT
data

Dataset for
operatingoperator support
technology

Technology related to measuring
equipment (e.g. Specification ofrequirements, installation technology,
maintenance technology)[Activities to support operators]
Example. Simulations for creating amanual(A)

Data from evaluation results to
reduce uncertainty on-site

Data from the evaluation results of thematching characteristics between the mid-and
long-term work plan and the environment
inside the PCV[Output of support
technology]
Example. Conditions for
simulation to generate moreaccurate manuals[Output of support technology]
Example: Indication that operation ofcurrent air conditioning equipment andsite conditions
do not match

Where to apply
the results ofaction item (3)(examine theconcept of theflow ofinformation andits utilization asshown in thisfigure)Reduced dependence on
hypothetical data inputs
to the simulation[Annual work plan
improvement support][Analysis by the person in charge of operation support]
Example: Desiring to increase the exhaust air flow of airconditioning equipment. The system for work plan
improvement support suggests that if the operation parameteris set to △△, it will not adversely affect other systems.

[Output of support technology]
Renewal of work plans©International Research Institute for Nuclear Decommissioning

Appendix 3.2-1: Flow of development of the study (detailed version)(2) Study of the

No.77

monitoring methods
Example: Debris retrieval model did notreflect an exhaust air motor that could
indirectly monitor filter clogging- Structural information inside and outside of the PCV- Law/implementation plan/safety regulations- Others (current monitoring items inside the PCV, etc. )Input as reference
information to design

Results of system study
for each subsidized
project for the Fukushima
Daiichi

Input as reference
information to
designResults of the study ofsubsidized projects up
to FY2020

Information otherthan subsidized
projects

A(2)① Study of diversification of monitoring measures

No

A

Unable to address
due to modification of
the debris retrieval
model

Fuel debris retrieval andtransfer system (inside the
PCV)

Debris retrieval modelGas phase system(inside the PCV)No

Liquid phase system(inside the PCV)

Was adequate settings
information obtained toconstruct the model?

Yes(2)② Study of installation methods for

Maintenance ofdevelopment
issuesmeasuring equipment

No

No
Output: (Goal 1)
Requirements
and issues inmonitoring
inside the PCV

No on-site maintenance/installation issues
Yes(2)③ Organizing technological issues(3)① Study of on-site data usage measures

Extraction of work delay factors

for deficiencies] Settings
with variations implemented
in this project(1) Does the installation method
satisfy the specifications in ②?

B

No

Risk assessment

Are there any on-site data that islacking?
Yes

Deciding on the important monitoring items inside
the PCV(safety, operators, throughput)A
Needs of plant operatorsfrom the operator's pointof view (first fiscal year)

Consider the accuracy of
required measurement and onsite environmental changes(variation) due to the progress of
on-site operations

B(1)② Organizing specifications for monitoring
requirements(1) Investigation of monitoring items inside the PCVPlan forpenetration
utilizationby plant
operators

Yes

Yes

[Measures to compensate

Input todesignYes

B(1)①
Investigation ofimportantmonitoring
items

No

Diversification ofimportant monitoring
items is possible

Example:Filter clogging
cannot bemonitored
indirectly

Needs ofplant
operators
from theoperator's
point ofview (nextfiscal year)(3)② Study of overall treatment process of on-site data

Maintenanceofdevelopment
issuesNo

There are no development
issues in the overall
treatment process of onsite data
Yes(3) Study of integrated
management support
technology

Output: (Goal 2) Monitoring data operational concept©International
Institute for Nuclear Decommissioning
The decisions from the reviews are setup at various points to ensure output is inline withResearch
the goalAppendix 3.3-1: Relationship between this project and other research■ Details of contributions to other projects (delivery)

No.78

Contributions to each project are as follows.
[Main results for achieving the goals of this project]• Important monitoring items (weighted in terms of safety, operators, and throughput) andtheir implementation methods. Or issues in implementation.
[Contributions to each project based on the above results]• Important monitoring items for each method can be set and reviewed.
• The necessary monitoring technology for each method can be identified.
[Secondary effect]• To maintain normal work of each method,→ Present the evaluation process leading to the determination of monitoring items for the
method(Corresponds to the details of study in Chapter 6)→ Present the process of extracting design conditions for a system that will continue tomaintain a state of safety(Corresponds to the procedure for conducting risk assessments in Section 6.2.4.)→ Present additional details of study necessary to improve the accuracy of the above two
items(Examples. test data, on-site data, physical model, etc.)

In addition to presenting candidates for important monitoring items that should be
adopted for each method, this project presents various design processes to maintainnormal work as a secondary effect.
©International Research Institute for Nuclear Decommissioning

Appendix 6.2.1-1: Prerequisites for the study (contributions of monitoring in accordancewith the level of risk)
•

No.79

This project will study the monitoring items necessary to maintain normal conditions, but the items to be extracted
are thought to contribute to the overall risk level. Specifically, the following A) and B) are noted.
A) Be more specific about safety risks arising from fuel debris retrieval.
B) Not only for monitoring to verify that a safety risk has become a reality under normal conditions and a shift
to an abnormal condition has occurred, but monitoring items are also extracted for taking proactive
approach to detect signs of a shift to an abnormal condition.
Risks based on safety
requirements studied
previously[Input required for continuous monitoring project]
Configuration concepts, equipment control
parameters, and control values for operational andsafety equipment operating under normal conditions[Output from continuous monitoring project]
More specific risks that clarify the causal
relationship between operational equipment
and safety equipment

Input

Input

Risks arising fromfuel debris retrieval
Risk latency

Normal conditions

Input

Monitoring items subject tocontinuous monitoring project
Important monitoring for normal
conditions*

Increased risk level
Loss of normal safetyfunctions
Progression of
eventsRestoration

Duringabnormality/accident

Monitoring for signs of abnormal
conditions[Output from continuous monitoring project]- Monitoring to determine that conditions are normal- Monitoring to predict signs of shift to abnormal
conditions*Inherits some or all of the monitored items*

Monitoring for abnormality
detection*

It is thought that the output of the continuous
monitoring project could be monitored for detecting
abnormalities and for post-accident monitoring.

Post-accident monitoring

The monitoring system monitors abnormalities and signs of safety measures to help
©International Research Institute for Nuclear Decommissioning
ensure throughput

Appendix 6.2.3.1-1: Study of the operational equipment model (equipment operation mode)
No.80
Details of the results of the study of debris processing work (1/4)■ Study results ① “Where will the fuel debris be processed?”• Fuel debris processing methods are planned by the
Fukushima Daiichi subsidized projects “Upgrading ofApproach and Systems for Retrieval of Fuel Debris andReactor Internals” and “Upgrading of Fundamental Technology
for Retrieval of Fuel Debris and Reactor Internals,”:
Processing methods for exposed fuel debris in the air orsubmerged in water.
• As a result, the processing site is either in air or underwater.

©International Research Institute for Nuclear Decommissioning

Appendix 6.2.3.1-1: Study of the operational equipment model (equipment operation mode)
No.81
Details of the results of the study of debris processing work (2/4)■ Study results ② “What properties does the fuel debris have?”•

The properties of the fuel debris organized in the characterization project(*) were sorted into 7 types (including others)
from the viewpoint of work process.
Shape of fuel debris assumed in the characterization projectPrimary component

Molten or damaged structures

Fe

Damaged CRD/CRD housing

B4C, Fe

Damaged core support plate covered with molten debrisFe

Unmolten, damaged fuel pins and structures

UO2, Zry-2

A portion of the fuel assembly that remains without melting down

UO2, Zry-2, (U, Zr)O2-C, (Zr, U)O2-T, Zr(O), Fe

Rapidly cooled molten core material that has broken into small pieces(U, Zr)O2-C, (Zr, U)O2-T

Solidified relatively early near the upper surface of the molten pool

(U, Zr)O2-C, (Zr, U)O2-T, Fe

Slowly cooled down and turned into lumps near the center of themolten pool

(U, Zr)O2-C, (Zr, U)O2-T, Fe

Solidified relatively early near the lower surface of the molten pool

(U, Zr)O2-C, (Zr, U)O2-T, UO2, Fe

Molten debris solidified in the lower head

(U, Zr)O2-C, (Zr, U)O2-T, Zr(O), Fe2Zr

Rapidly cooled molten core material that has broken into small pieces(U, Zr)O2-C, (Zr, U)O2-T

Cooled and solidified relatively early on the upper surface of the molten
pool during MCCI(U, Zr)O2-C, (Zr, U)O2-T, Al-Ca-Si-O

Molten corium slowly cooled down and turned into lumps during MCCI(U, Zr)O2-C, (Zr, U)O2-T, Al-Ca-Si-O

Metallic deposit on each part of MCCIFeBoundary between molten corium pool and concrete(U, Zr)O2-C, (Zr, U)O2-T, SiO2, (Zr, U)SiO4, Al-Ca-Si-O

Not currently defined in the project of Fuel Debris Characterization---

Powdered fuel debris of 0.1 mm or less generated during processing, etc., among the above-mentioned fuel debrisClassifications in thecontinuous monitoring
project

Existing structure (withsurface contamination)

Fuel- U-rich mass of fueldebris- Fe-rich mass of fueldebrisMCCI formations

OthersFuel debris powder(**)(*) Research report on “Development of Analysis and Estimation Technologies for Fuel Debris Characterization” (March,2019)Research Institute for Nuclear Decommissioning©International(**) (**) Among fuel debris powders, those that have the potential of migrating into the gas/liquid phase are referred to as dust

Appendix 6.2.3.1-1: Study of the operational equipment model (equipment operation mode) Details of theresults of the study of debris processing work (3/4)
No.82■ Study results ③ “How is it processed?”•

A precondition is set based on the throughput evaluationthat does not depend on the method by the project ofUpgrading and Method and Systems (*). The same method
is adopted in this project.
(*) Project of Upgrading of Methods and Systems for Retrieval of Fuel
Debris and Reactor Internals
No.

Items

Conditions

1

Fuel debris retrieval timeframe goals

Unit 1: 10 years, Unit 2: 10 years, Unit 3: 10 years

2

Number of fuel debris retrieval days
per year

200 days (days other than working days are considered maintenance days)

3

Fuel debris processing hours per day

Within 10 hours

4

Amount of fuel debris

Assuming Unit 3 which has the largest total volume. (CRD instrumentation tube
adhesion: 6 tons*, inside the pedestal: maximum 222 tons, outside the pedestal:maximum 146 tons, total: 374 tons)

5

Fuel debris processing tools

In the operational equipment model,“crushing, cutting, and picking up” aretreated as a group, but in order to extract
disturbing the normal conditions specificto the processing method, evaluations
are also conducted for items within thedashed lines.

1. MCCI: chisel processing, ultrasonic core boring, etc.
2. CRD with instrumentation tube adhesion: disc cutter, AWJ, laser, etc.
3. Adhesion of metals: Disc cutter, AWJ, laser, etc.

Crushing

Core boring
ChiselCutting

Disc cutter

AWJ
6

8

Fuel debris processing speed

1. Chisel processing, ultrasonic core boring: Based on the results ofelemental tests of this project.
2. Disc cutter, AWJ, Laser: Processing speed similar to removal ofinterfering objects.
3. Core boring: 3.25 kg/h (FY2016 test results)
4. Laser gouging: 4.76 kg/h (FY2016 test results)

Method of collecting fuel debris

Proven collection methods such as grabbing and scooping are applied as an
estimated condition, and the results of elemental tests are also taken into
consideration.

Fuel debris handling speed

Proven handling methods are applied as an estimated condition, and the resultsof elemental tests are also taken into consideration.

Chipping

Laser gouging

Picking up©International Research Institute for Nuclear Decommissioning

Appendix 6.2.3.1-1: Study of the operational equipment model (equipment operation mode)
No.83
Details of the results of the study of debris processing work (4/4)■ Study results ④ What is used for collecting fuel debris?
•
•

•

•
•
•

The fuel debris powder (dust) shown in the study results ② is collected by a filter installed on the gas/liquid
phase treatment systems of the safety equipment, and is not included in the operational equipment model.
In the Fukushima Daiichi subsidized project, “Development of Technology for Further Increasing theRetrieval Scale of Fuel Debris and Reactor Internals,” the following construction methods are being
investigated.
Top-access retrieval method: Plan ①/Plan ②Side-access retrieval method: Plan A, Plan B, and Plan C
For the above five methods, the following applications of containers for collecting fuel debris are being
considered.
Top-access retrieval method: Plan ① → Transfer containers
Top-access retrieval method: Plan ② → Unit cans
Side-access retrieval method: Plans A, B, C → Unit cans (Plans A and C also use canisters)
Any of the above are containers for initially collecting the processed materials in the PCV atmosphere.
These containers may be collected into another container for safety reasons during transfer out of the
primary boundary.
For example, unit cans do not have safety functions (confinement, shielding, heat removal, etc.) other thancriticality prevention function through dimensional control, so collection must be into containers such as
casks.
Therefore, in the operational equipment model, the container where the fuel debris is stored is called the“inner container (general term for unit cans and storage canisters)”. Furthermore, a container that stores theinner container and is safely transferred out of the primary boundary is established as a “transfer cask.”

Fuel debris is directly stored in the inner container and stored in the transfer cask before transferred out of the
primary boundary©International Research Institute for Nuclear Decommissioning

Appendix 6.2.3.1-2: Environmental conditions of cell equipment[1] Debris Retrieval Project (FY2020 Final Report), 4.1.1.1(3)(i)-pp.130 to 131[2] Debris Retrieval Project (FY2020 Final Report), 4.1.1.1(3)(i)-p.3, Table
4.1.1.1(3)(i) – 3[3][9 ]Debris Retrieval Project (FY2020 Final Report), 4.1.2.4(2)-p.2, Table
4.1.2.4(2) – 2[4] Debris Retrieval Project (FY2020 Final Report), 4.1.2.4(3)-p.18, Table
4.1.2.4(3) – 11
[5] METI, Decontamination Technology Catalogue, High-Pressure Water Jet
Removal Method
https://www.meti.go.jp/earthquake/nuclear/pdf/120626/120626_01j.pdf[6] Debris Retrieval Project (FY2020 Final Report), 4.1.1.1(3)(i)-p.2, Table
4.1.1.1(3)(i)-2, Assumes the container surface will become contaminated tothe same degree as the well and RPV inner surface by passage inside thePCV[8] (Container outer surface area x container surface contamination
concentration) x dust dispersion rate x 24 hours ÷ cell spatial volume[9] When there is an upward flow with a velocity of 10 [cm/s] inside the cell

Secondary boundary

PCV and cell
(red area)

Delivery of empty storage containers
Debris collection
mechanism

Cell transfer
mechanism

Intra-cell transfer
mechanism ①

Debrisprocessing
mechanism

Moving mechanism inside thePCV (*2)

Transfer cask
(Unconfined state → Capped state)Container surface
contamination
concentration
Dimension of each cell(assumed in this project)
Amount of increase incontamination
concentration in the cell
due to dust dispersion fromthe container surface
Amount of hydrogengenerated from container
Amount of heat generated
by the container
Contaminated water fromdecontamination

Gamma ray: approx. 1.0E+05[mSv/h] [1]
Neutron radiation: approx. 10[mSv/h] [1]1.0E+08 [Bq/cm2] [6]Cell (R): height 11[m], width 11[m],depth 14[m]Dispersion rate: 1.0E-10 [1/s] [2]Concentration of air contamination(24 hours): 1.7 E-03 [Bq/cm3] [8]Dust particle size [9]: 15 [μm] orless (UO2)
20[μm] or less (Fe), 40[μ m] or less(concrete).
Amount generated per unit time:
0.4 [L/h] [3]
Total amount generated (24hours): 9.6 [L]
68 [W/pc] [9]NoneTransfer cask
(Capped state & shielded)
Decontamination water drainage
mechanism

Cell (Y)Cell (G)Same as that on the left
(Before collection into
inner container)[Gamma rays]
Surface: 2 [mSv/h] [4]1m away from the surface: 0.1[mSv/h][4]0.4 [Bq/cm2] or less [4]Same as that on the left
(Before collection into
inner container)
Same as that on the left

Verification
mechanism before
transferring outside
the cellDoor mechanism G/Outside cell

Inner container (*1)
(unconfined state)

Cell (R)

Decontamination
mechanism

Door mechanism Y/GFuel debris

Mechanism for transfer
outside the cell

Intra-cell transfer
mechanism ②

Collection mechanism

Door mechanism R/YContainer surface dose rate

No.84

Delivery of empty storage containers* 1 Refers to unit cans and canisters*2 “Move” is used for components other than fuel debris.

Parameters

Cell (green area)

Cell (yellow area)

SecondaryboundarySame as thaton the left
Same as thaton the left

Same as that on the left―

Same as that on the left
(Before collection into
inner container)

Dispersion rate: 1.0E-10 [1/s][2]Concentration of air
contamination (24 hours):
6.8 E-12 [Bq/cm3] [8]Dust particle size: Same as left

Same as thaton the left

Same as that on the left
(Before collection into
inner container)

0 [L/h]Same as thaton the left

Same as that on the left

Same as that on the left

None

Same as thaton the left
No

[For high-pressure water jet [5]]Cleaning pressure: 29.4 [MPa],
Cleaning flow rate: 170 [L/min]-> 1700 [L] (1 minute cleaning x 10
times) ©International Research Institute for Nuclear Decommissioning

Appendix 6.2.3.1-3: Table of safety functions performed by components thatmake up the operational equipment (1/2)
•

No.85

The results of the settings of safety functions for operational equipment are shown on the next
page. If the safety functions are disturbed, it is assumed that the operator's accurate and prompt
on-site response will be disturbed.

[Explanation of the table shown on the next page]• For ease of understanding, various requirements are divided into those during processing andthose during transportation.
• Classified because, even if the gas phase confinement is the same, the required functions are
not all the same between the PCV that processes the fuel debris and the cell that handles thecontainer (e.g. See ID 1 to 3 and ID 4 in the table on the next page).
• The fuel debris processing mechanism and inner container are responsible for dust dispersion
and maintaining sub-criticality conditions during fuel debris processing (e.g. ID 2 and 5 in thetable on the next page).
• The cells, door mechanisms and transfer casks are responsible for shielding and confinement of
the fuel debris and PCV atmosphere (e.g. IDs 1, 4, and 6 in the table on the next page).
• The inner containers and transfer casks are responsible for most of the safety requirements
during fuel debris transfer (e.g. IDs 10 to 13 and 15 in the table on the next page).
• Decontamination of the transfer cask is based on the premise of water decontamination, and thecontaminated water dispersion prevention function (ID 9 in the table on the next page) wasestablished because the spent decontaminated water is contaminated and there is a possibility ofdispersion outside the secondary boundary.

©International Research Institute for Nuclear Decommissioning

Appendix 6.2.3.1-3: Table of safety functions performed by components that make up the operational equipment (2/2)

No.86

Note: Inner container refers to unit cans and canisters [1] Fire and explosion
ID
Safety requirements(A) Requirements during processing

PCV/cell damage preventionfunction

12

Functional requirements

Gas phase confinement(inside the PCV)

3

Dust dispersion preventionfunction
Function to prevent excessive
heatup of fuel debris

Configuration of components
Debris processing mechanism
Radiation source collection
mechanism
Debris processing mechanism
Debris processing mechanism

Design requirements
The equipment that maintains the boundary should not exert
external forces (collisions, drops, etc.) that can cause deformation
Do not allow generation of PCV dust concentrations exceeding
control parameters
Avoid re-volatilization of radioactive materials due to abnormal
temperature rise of debris4

Gas phase confinement(Inside debris collection andtransfer area for cells, etc.)

Static boundary function

Cell (R), Cell (Y), Cell (G),Door mechanism (R/Y),
Door mechanism (Y/G),
Door mechanism (Y/G)

5

Criticality prevention

Debris shape control function

Debris processing mechanism , inner Debris processing must maintain the shape that does not cause recontainer
criticality

Shielding function of the cell

Cell (R), Cell (Y),Cell (G),Door mechanism (R/Y),
Door mechanism (Y/G),
Door mechanism (Y/G)

Do not leak excessive radiation to the secondary boundary

Static boundary function

Cell (R), Cell (Y), Cell (G),Door mechanism (R/Y),
Door mechanism (Y/G),
Door mechanism (Y/G)

Avoid excessive release of radioactive materials to the secondary
boundary when handling debris or transfer casks

PCV/cell damage preventionfunction

Cell transfer mechanism
Intra-cell transfer mechanism ①
Intra-cell transfer mechanism ②

The equipment that maintains the boundary should not exert
external forces (collisions, drops, etc.) that can cause deformation

6

Prevention of external exposure

Avoid excessive release of radioactive materials to the secondary
boundary when handling debris or transfer casks(B) Requirements during transportation

7

Gas phase confinement(Inside debris collection andtransfer area for cells, etc.)

810Liquid phase confinement duringtransfer cask decontamination(water decontamination)
Confinement of gas phase/liquid
phase leak during on-site transfer

11

Criticality prevention

12

Prevention of abnormal heatup ofdebris13

Prevention of external exposure

Transfer cask confinement
function
Debris shape maintenancefunction of transfer cask
Heat removal function oftransfer cask
Shielding function of transfer
cask

14

Prevention of internal exposure

Transfer cask decontamination
Decontamination mechanism
function

15

Prevention of fire and explosion [1] Fire and explosion [1]prevention function of transfer
during on-site transfer
casks

9

Contaminated water dispersion Decontamination water drainage
prevention function
mechanism
Transfer cask
Inner container, transfer cask
Inner container, transfer cask
Transfer cask

Transfer cask

Prevent wastewater dispersion from outside the secondary
boundary during decontamination of the transfer cask (water
decontamination)
Prevent excessive leakage of radioactive materials from the debris
inside the container after transfer from the primary boundary
Maintain a shape that prevents debris from reaching re-criticality
during transfer
Avoid abnormal temperature rise of debris and re-volatilization ofradioactive materials during transfer
No excessive exposure to workers should be caused by radiation
after transfer from the primary boundary
No excessive internal exposure to workers should be caused bycontaminated materials dispersion from the surface of the transfer
cask after transfer from the primary boundary
Ensure that hydrogen generated from the debris inside the vessel
does not cause hydrogen combustion, which may damage thevessel or impede other functions©International Research Institute for Nuclear Decommissioning

Appendix 6.2.3.2-1: Study of the safety equipment model/Configurationof physical model of environment inside the PCV (1/4)

No.87

Using a gas phase system as an example, a physical model of theenvironment inside the PCV for each safety function is shown.
Safety function (gas phase system)
Physical model of environment inside the PCV( Environmental
variables inside the PCV (physical quantity) = Dust concentration
inside the PCV)
[Dust concentration reduction function]
Control parameter: Environmental model inside the PCV for dust concentration
inside the PCV (Pattern A)
A (Dust concentration inside the PCV) × V =S
V: Amount of dust generated ( = Amount of fuel debris processed [kg/day] × Dust dispersion rate [-])
: Evaluation volume [m3 ] (Example. PCV, cell, etc.): Dust deposit rate(= Dust terminal velocity [m/s] ÷ PCV height [m]): Dust ventilation rate (= PCV gas management system exhaust airflow [m 3/h] ÷ PCV volume [m3]): Filter removal rate (= recirculated airflow [m3/h] ÷ PCV volume [m3] × HEPA filter efficiency [-])

©International Research Institute for Nuclear Decommissioning

Appendix 6.2.3.2-1: Study of the safety equipment model/Configurationof physical model of environment inside the PCV (2/4)

No.88

Safety function (gas phase system)
Physical model of the environment inside the PCV(Environmental variables inside the PCV (physical quantity = PCV leakage amount)[Static Boundary Function]
Control parameter: Physical model of the environment inside the PCV for PCV
leakage (Pattern B)
In this study, the amount of PCV leakage is assumed to depend on the size of
the PCV opening, and the factors that increase the size of the PCV opening
were organized.
Factors that increase size of the PCV opening- Increase in size of opening due to corrosion- Increase in size of opening due to deterioration of new structures (celldoors, closures of existing openings, welded parts, etc.)- Others©International Research Institute for Nuclear Decommissioning

Appendix 6.2.3.2-1: Study of the safety equipment model/Configuration of
No.89
physical model of environment inside the PCV (3/4)
Safety function (gas phase system)
Physical model of the environment inside the PCV(Environmental variables inside the PCV (physical quantity) = Negative pressure inside
the PCV)[Dynamic Boundary Function]
Control parameter: Physical model of the environment inside the PCV for the degreeof negative pressure inside the PCV (Pattern A)•

Steady condition (negative pressure condition)
F PSA + f (degree of negative pressure inside the PCV) × B + F cell = F ex
Degree of negative pressure inside the PCV = Atmospheric pressure - PCV pressure
FPSA: Nitrogen-charged airflow by PSA [m3/h]
Fex: PCV gas management system exhaust airflow [m3/h]
Fcell: Inflow airflow from adjacent cells [m3/h]f (Degree of negative pressure inside the PCV): Flow velocity due to differential pressure
between inside and outside of the PCV opening [m/s]B: Size of the PCV opening [m2]©International Research Institute for Nuclear Decommissioning

Appendix 6.2.3.2-1: Study of the safety equipment model/Configuration of
No.90
physical model of environment inside the PCV (4/4)
Safety function (gas phase system)
Physical model of the environment inside the PCV(Environmental variables inside the PCV (physical quantity) = Exhaust end dust
concentration)[Emission control function]
Control parameter: Physical model of the environment inside the PCV for exhaustend dust concentration (Pattern A)•

Exhaust end dust concentration C (kg/m 3)
C (exhaust end dust concentration) = A (dust concentration) × DFADF: Dust concentration (Modeled with dust concentration
reduction function [kg/m 3]): Filter efficiency [-]©International Research Institute for Nuclear Decommissioning

Appendix 6.2.3.3-1: Debris retrieval model (environmental conditions inside the PCV)
Cell (R)

Nitrogen
supplysystemContainer
sealingmechanism

Secondary boundary
Cooling water

NitrogenDebris

Debris

Decontamination
mechanism
Verification
mechanism
beforetransferringoutside the cell

[Inside the RPV]
Neutron absorbent
Dose rate: Maximum 5000 Gy/h [4][Cell (R)]
Temperature: Maximum 50°C supply equipment
for
Dose rate ≦ 1 mSv/h [3]processing work
Humidity: 100% (With
Temperature: 25°C
condensation )(consequential)↑ Purified
gas
Pressure(gauge pressure):-2000
Humidity: No condensation↓ PCV atmosphereto 500 Pa
HEPA
HEPA
Pretreatment Pressure (gauge
filter pressure): - filter
facility
2000 to 500 Pa
Stagnant waterContamination
concentration: [3]
HEPA
HEPA
Pretreatment
filter
[Cs-137] ≦3E+04
Bq/cm3filterfacility[Pu-238] ≦7 Bq/cm3
D/W stagnant[Inside the pedestal][Outside the pedestal]water transfer
Dose rate: Maximum 100 Gy/h
Dose rate: Maximumpump
100A/BGy/h[4][4](Reference: the Fukushima(Reference: the Fukushima
Daiichi-2
measuredvalue
8[Detailed configuration of components] Daiichi-2 measured value 43
Gy/h [1])Gy/h [1])Temperature: Maximum
50°C
Temperature: MaximumCharcoal
50°C
Pretreatm
filter(Reference: the Fukushima(Reference: the Fukushima
ent facility
Daiichi-2 measured value 23°C
Daiichi-2 measured value 24°C
[1])
[1])
Backwash dry
Electric
Humidity:
100% (With
Humidity: 100% Charcoal(With
Demisterdust
collection
heaterfilterequipment
condensation )condensation )Pressure (gauge pressure): Pressure (gauge pressure): 2000 to 500 Pa
2000 to 500 Pa

D/W stagnant
water coarse
particles removal
equipment

HEPA
filterMechanism fortransfer outside thecell

PCV stagnant
water
Buffer tank

PCV stagnant
water injection
pump

HEPA
filterHEPA
filter

Door mechanism
G/Outside cell

Well

Nitrogen

Secondary boundary

Intra-cell transfer
mechanism ②

Door mechanism Y/GDoor mechanism R/Y[Cell (R)]
Dose rate > 1 mSv/h [3]Temperature: 25°C
(consequential)
Humidity: No condensation
Pressure (gauge pressure): 2000 to 500 Pa
Contamination concentration: [3][Cs-137]＞3E+04 Bq/cm3[Pu-238]＞7 Bq/cm3
NitrogenIntra-cell transfer
mechanism ①

Cell transfer
mechanismContaminated water(decontamination)

Debris collection
mechanism

Cell (G)Cell (Y)No.91

Exhaustventilator

To exhaust port

Exhaustventilator[Cell (R)]
Dose rate ≦ 0.1 mSv/h [2]Temperature: 25°C
(consequential)
Humidity:
No condensation
Charcoal
ExhaustPressurefilter (gauge pressure): ventilator
2000 to 500 Pa
ExhaustCharcoal
Contamination
concentration:[3]
filter≦3E+03 Bq/cm3 ventilator[Cs-137][Pu-238] ≦7E-01 Bq/cm3

To water treatment
systemTo exhaust port

Cooler[References]
PCV stagnant[1] The 63th Secretariat TeamwaterMeeting
discharge for Countermeasures
To water treatment for Decommissioning and Contaminatedpump
Water Treatment Meeting, Document
3-3, Implementation
system Results of Investigation Inside the PCV for
Unit 2 , February 28, 2019https://www.tepco.co.jp/decommission/information/committee/roadmap_progress/pdf/2019/d190228_08
To water treatment-j.pdfsystem[2] FY2018 Subsidized Project “Development of Technology
for Further Increasing the Retrieval Scale
Flow of airof Fuel Debris and Reactor Internals,” Research Report, April 2021, Figure 4.1.1.1(3)(i)-71
Flowof liquid[3] FY2018 Subsidized Project “Development of Technology for Further Increasing theRetrievalScaleof Fuel Debris and Reactor Internals,” Research Report, April 2021, Table 4.1.1.1(3)(i)-9Primary boundary(*)[4] FY2018 Subsidy Project “Development of Technology for Further Increasing the Retrieval Scale of
Fuel Debris and Reactor Internals,” MRI Final Report, March 2021
* Boundaries in piping connected to the PCV are not shown©International Research Institute for Nuclear Decommissioning

Appendix 6.2.3.3-2: Example of transient changes in environment inside the PCV (1/2)

No.92

・D: Sa-4: An example of transient changes during “processing of debris” is shown on the next page.

Intra-cell transfer
mechanism ①

Cell transfer
mechanism

Nitrogen

Secondary boundary

Cooling water

Neutron absorbent supply
equipment for processing
work

Dust
dispersion

Nitrogen- Injection ofprocessing aid (water,abrasives)- Injection of antiscattering agent for
dust (water spray)- Heat input

Dust migrated into
the gas phasemoves outside thepedestal

Debris

DebrisMechanism for transfer
outside the cell

Decontamination
mechanism

Door mechanism
G/Outside cell

Nitrogen
supplysystemCollection
mechanism

Door mechanism Y/GDust adheresin cell (R)Debris collected
into innercontainer

Nitrogen

Door mechanism R/Y

Dust migrated into
the gas phasemoves to cell (R)Secondary boundary

Intra-cell transfer
mechanism ②

Verification
mechanism
beforetransferringoutside the cellContaminated water(decontamination)

Debris collection
mechanism

Cell (G)Cell (Y)Cell (R)HEPA
filterExhaustventilator

HEPA
filterTo exhaust port

Exhaustventilator
To watertreatment system

Pretreatment
facility

HEPA
filterHEPA
filterCharcoalfilterExhaustventilator

Pretreatment
facility

HEPA
filterHEPA
filterCharcoalfilterExhaustventilator

To exhaust port

Some airborne dust
reach
Contaminated water that
migrated to the liquid phaseleaks into and out of pedestal[Detailed configuration of components]

D/W stagnant
water transfer
pump A/B

D/W stagnant
water coarse
particles removal
equipment

Some of the dust
suspended/dissolved in the liquidreachCharcoalfilterPretreatment
facility

PCV stagnant
water
Buffer tank

PCV stagnant
water injection
pump

Cooler

PCV stagnant
water dischargepump

To watertreatment system

To watertreatment system

Flow of air
DemisterElectric
heater

Backwash dry
dust collection
equipment

CharcoalfilterHEPA
filterFlow of liquid
Primary boundary(*)* Boundaries in piping connected to the PCV are not shown©International Research Institute for Nuclear Decommissioning

Appendix 6.2.3.3-2: Example of transient changes in environment inside the PCV (2/2)

Intra-cell transfer
mechanism ①

Cell transfer
mechanism

Well
Debris collected
into innercontainer

Nitrogen

Mechanism fortransfer outside thecell

Decontamination
mechanism

Door mechanism G/Outside cell

Dust migrated into
the gas phasemoves to cell (R)Intra-cell transfer
mechanism ②

Verification
mechanism
beforetransferringoutside the cell

Nitrogen

Dust adheres incell (R)

Cooling water
Dust
dispersion

Nitrogen- Injection of processing
aids(water , abrasives)

Debris

Debris[During fuel debrisHEPAprocessing]
Decontamination

Contaminated water(decontamination)

Nitrogen supply
systemTo exhaust ventExhausterfilterSome waterof drainage
the dust generated in the fuelmechanism
HEPA
Neutron absorbent
Exhausterfilter reach thedebris processing work
cell
supply equipment
Dust migrated into the gas phase for processing workmoves outside the pedestal
without a door (R), floats in the air andsettles on the floor.

To wastetreatment
systemTo exhaust
port↑ Purified gas

Pretreatment
facility

PCV atmosphere

HEPA
filterHEPA
filterCharcoal

ExhausterSome airborne dust reach

Cell (R)
Debriscollection
mechanism

Cell transfer
mechanism

Cell (G)

Nitrogen

Nitrogen

Mechanism fortransfer outside
the cellDecontamination
mechanism

Unsealed debris:
Hydrogen, dust,
radiation generated

Verification
mechanism before
transferringoutside the cell

HEPA
filter

Door mechanism G/Outside cell

[During cell transfer]
By opening the door, errors embedded
Nitrogen supply
systemin past operations
became apparent, Cooling water Resurfacing and influxof dust settled on thefloor
and inflow of dust occurredSecondary boundary

Intra-cell transfer
mechanism ②

Door mechanism Y/GInflow of residual
dust in the air

Cell (Y)Door mechanism R/Y•

Debriscollection
mechanism

Secondary boundary

Cell (G)Cell (Y)Door mechanism Y/G•Cell (R)

Door mechanism R/Y•

An example of how environmental
changes inside the PCV that occur
during fuel debris processing canadversely affect subsequent work isshown.
The upper right figure depicts thepossibility of some of the dust reachcell (R) due to fuel debris
processing in the PCV. The historyof changes in the environment will
be kept in subsequent roadmaps as
well.
The lower right figure depicts anerror event in which the dust
remaining in cell (R) flows in when
the door for cell (Y) is opened.
It was verified that the roadmap ofenvironmental changes as
described above is an effective
method for extracting risks causedby transient environmental changes
in the PCV.

water
(decontamination)

•

No.93

Exhauster

To exhaust
port

Waste treatment

Roadmap of environmental changes is effective for extracting risks due to transient environmental changes in
the PCV©International Research Institute for Nuclear Decommissioning

Appendix 6.2.3.3-3: Debris retrieval model (roadmap of environmental changes in the PCV) (1/10)
ID: Sa-1 “Verification of the overall situation inside the PCV, and operational/safety equipment”
Cell (Y)Cell (R)Cell transfer
mechanism

Debris collection
mechanism

Mechanism fortransfer outside thecell

Decontamination
mechanism
Verification
mechanism
beforetransferringoutside the cell

Door mechanism
G/Outside cellContainer
sealingmechanism

Door mechanism Y/GDoor mechanism R/Y

Nitrogen

Secondary boundary

Intra-cell transfer
mechanism ②

Intra-cell transfer
mechanism ①

Well
Nitrogen

Secondary boundary

Cooling water

Neutron absorbent
supply equipment forprocessing work

Nitrogen↑ Purified gas↓ PCV atmosphere

DebrisStagnant water

DemisterElectric
heaterCharcoalfilterHEPA
filterExhaustventilator

To exhaustport

To watertreatment system

HEPA
filterCharcoalfilterExhaustventilator

Pretreatment
facility

HEPA
filterHEPA
filterCharcoalfilterExhaustventilator

D/W stagnant
water coarse
particles removal
equipment

PCV stagnant
water
Buffer tank

Charcoalfilter

Backwash dry
dust collection
equipment

Exhaustventilator

HEPA
filter[Detailed configuration of components]
Pretreatment
facility

HEPA
filterPretreatment
facility

DebrisD/W stagnant
water transfer
pump A/B

Contaminated water(decontamination)

Nitrogen
supplysystemCell (G)No.94

PCV stagnant
water injection
pump

Cooler

PCV stagnant
water dischargepump

To watertreatment
systemTo watertreatment
systemHEPA
filterTo exhaust
port

Flow of air
Flow of liquid
Primary boundary(*)* Boundaries in piping connected to the PCV are not shown©International Research Institute for Nuclear Decommissioning

Appendix 6.2.3.3-3: Debris retrieval model (roadmap of environmental changes in the PCV) (2/10)
ID: Sa-2 “Approaching the object to be processed”

No.95
Cell (Y)Cell (R)Cell transfer
mechanism

Debris collection
mechanism

NitrogenContainer
sealingmechanism

Decontamination
mechanism
Verification
mechanism
beforetransferringoutside the cell

Nitrogen

Secondary boundary

Cooling water

Neutron absorbent
supply equipment forprocessing work

Nitrogen↑ Purified gas↓ PCV atmosphere

DebrisMove inside andoutside thepedestal

Demister

To watertreatment system

Exhaustventilator

Pretreatment
facility

HEPA
filterHEPA
filterCharcoalfilterExhaustventilator

D/W stagnant
water coarse
particles removal
equipment

PCV stagnant
water
Buffer tank

PCV stagnant water
injection pump

PCV stagnant water
discharge pumpCharcoalfilterExhaustventilator

CharcoalfilterCharcoalfilter

Backwash dry
dust collection
equipment

HEPA
filterTo exhaust port

HEPA
filter[Detailed configuration of components]

Electric
heaterExhaustventilator

HEPA
filterDebrisPretreatment
facility

HEPA
filterPretreatment
facility

Stagnant water

D/W stagnant
water transfer
pump A/B

Contaminated water(decontamination)

Nitrogen
supplysystemMechanism fortransfer outside thecell

Door mechanism
G/Outside cell

Move to inside
the RPV

Secondary boundary

Intra-cell transfer
mechanism ②
Door mechanism Y/GDoor mechanism R/Y

Well

Intra-cell transfer
mechanism ①

Cell (G)To exhaust port

Cooler

To water treatment
systemTo watertreatment system

HEPA
filterFlow of air
Flow of liquid
Primary boundary(*)* Boundaries in piping connected to the PCV are not shown©International Research Institute for Nuclear Decommissioning

Appendix 6.2.3.3-3: Debris retrieval model (roadmap of environmental changes in the PCV) (3/10)
ID: Sa-3 “Work prior to debris processing” *This diagram shows a typical example of work inside the RPV
Cell (Y)Cell (R)Cell transfer
mechanism

Debris collection
mechanism

Mechanism fortransfer outside thecell

Decontamination
mechanism
Verification
mechanism
beforetransferringoutside the cell

Door mechanism
G/Outside cellContainer
sealingmechanism

Door mechanism Y/GDoor mechanism R/Y

Nitrogen

Secondary boundary

Intra-cell transfer
mechanism ②

Intra-cell transfer
mechanism ①

Well
Nitrogen

Secondary boundary

Cooling water
Neutronabsorbent
spraying

NitrogenNeutron absorbent
supply equipment forprocessing work

↑ Purified gas↓ PCV atmosphere

DebrisPretreatment
facility

HEPA

HEPA

filterfilterPretreatment
facility

HEPA

HEPA

filterfilterD/W stagnant
water coarse
particles removal
equipment

PCV stagnant
water
Buffer tankStagnant water
DebrisNeutron absorbent leaked fromthe processing siteleaks/remains inside/outside thepedestal[Detailed configuration of components]

DemisterSome of theneutron absorbent
reach
CharcoalfilterPretreatment
facility

Electric
heaterD/W stagnant
water transfer
pump A/B

Backwash dry
dust collection
equipment

CharcoalfilterNeutronabsorbent
supplyContaminated water(decontamination)

Nitrogen
supplysystemCell (G)

No.96

HEPA

Exhaustventilator

filterHEPA

To exhaust port

Exhaustventilator

filter

To watertreatment system

CharcoalfilterExhaustventilator

CharcoalfilterExhaustventilator

PCV stagnant water
injection pump

Cooler

PCV stagnant water
discharge pump

To watertreatment system

To exhaust port

To watertreatment system

HEPA

filterFlow of air
Flow of liquid
Primary boundary(*)* Boundaries in piping connected to the PCV are not shown©International Research Institute for Nuclear Decommissioning

Appendix 6.2.3.3-3: Debris retrieval model (roadmap of environmental changes in the PCV) (4/10)
ID: Sa-4 “Processing of debris” *This diagram shows a typical example of work inside the RPV
Cell (Y)Intra-cell transfer
mechanism ①

Cell transfer
mechanism

NitrogenNeutron absorbent
supply equipment forprocessing work

Dust
dispersion

Nitrogen- Injection ofprocessing aid (water,abrasives)- Injection of antiscattering agent for
dust (water spray)- Heat input

Dust migrated into
the gas phasemoves outside thepedestal

Debris

DebrisContaminated water that
migrated to the liquid phaseleaks into and out of pedestal[Detailed configuration of components]

Electric
heaterD/W stagnant
water transfer
pump A/B

Backwash dry
dust collection
equipment

Verification
mechanism
beforetransferringoutside the cell

HEPA
filterExhaustventilator

HEPA
filterExhaustventilator

To exhaust port

To watertreatment system

HEPA
filterHEPA
filterCharcoalfilterExhaustventilator

Pretreatment
facility

HEPA
filterHEPA
filterCharcoalfilterExhaustventilator

D/W stagnant
water coarse
particles removal
equipment

Some of the dust
suspended/dissolved in theliquid reach

CharcoalfilterDecontamination
mechanism

Pretreatment
facility

CharcoalfilterPretreatment
facility

Demister

Secondary boundary

Cooling water

Mechanism fortransfer outside thecell

Door mechanism
G/Outside cell

Dust adheresin cell (R)Container
sealingmechanism

Door mechanism Y/GNitrogen
Nitrogen
supplysystemDebriscollected into
inner container

Door mechanism R/Y

Dust migrated into
the gas phasemoves to cell (R)Secondary boundary

Intra-cell transfer
mechanism ②(decontamination)

Debris collection
mechanism

Cell (G)Contaminated water

Cell (R)No.97

PCV stagnant
water
Buffer tankSome airborne dust
reach
PCV stagnant water
injection pump

PCV stagnant water
discharge pump

Cooler

To watertreatment
systemTo watertreatment
systemHEPA
filterTo exhaust port

Flow of air
Flow of liquid
Primary boundary(*)* Boundaries in piping connected to the PCV are not shown©International Research Institute for Nuclear Decommissioning

Appendix 6.2.3.3-3: Debris retrieval model (roadmap of environmental changes in the PCV) (5/10)
ID: Sa-5 “Various records following processing work”

No.98
Cell (Y)Cell (R)Cell transfer
mechanism

Debris collection
mechanism

Intra-cell transfer
mechanism ①

Secondary boundary
Neutron absorbent
supply equipment forprocessing work

NitrogenPurification gas
PCV atmosphere Pretreatment

DebrisD/W stagnant
water transfer
pump A/B

Verification
mechanism
beforetransferringoutside the cell

Exhauster

HEPA
filterExhauster

To exhaust port

facility

HEPA
filterHEPA
filterCharcoalfilterExhauster

Pretreatment
facility

HEPA
filterHEPA
filterCharcoalfilterExhausterD/W stagnant

PCV stagnant
water buffertankwater coarse
particles removal
equipment

PCV stagnant water
injection pump

PCV stagnant water
discharge pump

[Detailed configuration of components]
CharcoalfilterPretreatment
facility

HEPA
filter

To watertreatment system

Stagnant water
Debris

Decontamination
mechanismContaminated water(decontamination)

Nitrogen

Cooling water

Mechanism for transfer
outside the cell

Door mechanism G/Cell

Nitrogen
supplysystemDoor mechanism Y/GNitrogen

Secondary boundary

Intra-cell transfer
mechanism ②

Collection
mechanism

Door mechanism R/Y

Well

Cell (G)To exhaust port

Cooler

To wastetreatment
systemTo wastetreatment
systemFlow of air
DemisterElectric
heater

Backwash dry
dust collection
equipment

CharcoalfilterHEPA
filterFlow of liquid
Primary boundary(*)*Boundaries in piping connected to the PCV are not shown©International Research Institute for Nuclear Decommissioning

Appendix 6.2.3.3-3: Debris retrieval model (roadmap of environmental changes in the PCV) (6/10)
ID: Sa-6 “Cell transfer of debris”

No.99
Cell (Y)Debris collection
mechanism

Neutron absorbent
supply equipment
for processing work

NitrogenPurification gas
PCV atmosphere Pretreatment

Debrisfacility

Stagnant water

Pretreatment
facility

DebrisD/W stagnant
water transfer
pump A/B

D/W stagnant
water coarse
particles removal
equipment

Decontamination
mechanism
Verification
mechanism
beforetransferringoutside the cell

CharcoalfilterHEPA
filterExhauster

HEPA
filterExhauster

To exhaust port

To watertreatment system

HEPA
filterHEPA
filterCharcoalfilterExhauster

HEPA
filterHEPA
filterCharcoalfilterExhauster

PCV stagnant
water buffertank

PCV stagnant water
injection pump

To exhaust port

Cooler

PCV stagnant water
discharge pump

[Detailed configuration of components]
Pretreatment
facility

Mechanism for transfer
outside the cell

Door mechanism
G/CellSecondary boundary

Cooling water

Door mechanism Y/GNitrogen

Secondary boundary

Intra-cell transfer
mechanism ②

Collection
mechanism

Door mechanism R/Y

Unsealed debris:
Hydrogen, dust,
radiation generated

Nitrogen
Nitrogen
supplysystemIntra-cell transfer
mechanism ①

Cell transfer
mechanism

Cell (G)Contaminated water(decontamination)

Cell (R)

To wastetreatment
systemTo wastetreatment
systemFlow of air
DemisterElectric
heater

Backwash dry
dust collection
equipment

CharcoalfilterHEPA
filterFlow of liquid
Primary boundary(*)*Boundaries in piping connected to the PCV are not shown©International Research Institute for Nuclear Decommissioning

Appendix 6.2.3.3-3: Debris retrieval model (roadmap of environmental changes in the PCV) (7/10)

No.100

ID: Sa-7 “Transfer of Debris ①”

Nitrogen
Resurfacing and influxof dust settled on the
floor

Cooling water

Uncollected debris:
Hydrogen, dust,
radiation generated

Neutron absorbent
supply equipment forprocessing work

NitrogenPurification gas
PCV atmosphere Pretreatment

DebrisVerification
mechanism
beforetransferringoutside the cell

CharcoalfilterExhauster

Pretreatment
facility

HEPA
filterHEPA
filterCharcoalfilterExhausterD/W stagnant
water coarse
particles removal
equipment

PCV stagnant
water buffertankCharcoalfilterDemister

CharcoalfilterExhauster

HEPA
filter

PCV stagnant water
injection pump

PCV stagnant water
discharge pump

Backwash dry
dust collection
equipment

HEPA
filterTo exhaust
port

HEPA
filter[Detailed configuration of components]

Electric
heaterExhausterfacility

DebrisPretreatment
facility

HEPA
filter

To water treatment
systemStagnant water

D/W stagnant
water transfer
pump A/B

Decontamination
mechanismContaminated water(decontamination)

Nitrogen
Nitrogen
supplysystemMechanism for transfer
outside the cell

Intra-cell transfer
mechanism ②

Door mechanism Y/GInflow of residual
dust in the air

Intra-cell transfer
mechanism ①

Secondary boundary

Door mechanism
G/CellDoor mechanism R/YCell transfer
mechanism

Debris collection
mechanism

Cell (G)Cell (Y)Cell (R)To exhaust port

Cooler

To wastetreatment system

To wastetreatment system

HEPA
filterFlow of air
Flow of liquid
Primary boundary(*)*Boundaries in piping connected to the PCV are not shown©International Research Institute for Nuclear Decommissioning

Appendix 6.2.3.3-3: Debris retrieval model (roadmap of environmental changes in the PCV) (8/10)
ID: Sa-8 “Collection of debris”
No.101
Cell (Y)Intra-cell transfer
mechanism ①

Cell transfer
mechanism

Debris collection
mechanism

No radiation, hydrogen, or dust
generated after debris
collection

Cooling water

Neutron absorbent
supply equipment forprocessing work

Nitrogen

PCV atmosphere

Stagnant water
DebrisD/W stagnant
water transfer
pump A/B

Verification
mechanism
beforetransferringoutside the cell

HEPA
filterExhauster

HEPA
filterExhauster

To exhaustport

To watertreatment system

Pretreatment
facility

HEPA
filterHEPA
filterCharcoalfilterExhauster

Pretreatment
facility

HEPA
filterHEPA
filterCharcoalfilterExhausterD/W stagnant
water coarse
particles removal
equipment

PCV stagnant
water buffertankCharcoalfilterPretreatment
facility

Backwash dry
dust collection
equipment

PCV stagnant water
injection pump

PCV stagnant water
discharge pump

[Detailed configuration of components]

Demister

Decontamination
mechanism

Purification gas

DebrisElectric
heaterMechanism for transfer
outside the cell

Door mechanism
G/Outside cell

NitrogenCollection
mechanism

Secondary boundary

Intra-cell transfer
mechanism ②

Door mechanism Y/GDoor mechanism R/Y

Nitrogen
Nitrogen
supplysystemCell (G)Contaminated water(decontamination)

Cell (R)

CharcoalfilterTo exhaust port

Cooler

To wastetreatment
systemTo wastetreatment
systemHEPA
filterFlow of air
Flow of liquid
Primary boundary(*)*Boundaries in piping connected to the PCV are not shown©International Research Institute for Nuclear Decommissioning

Appendix 6.2.3.3-3: Debris retrieval model (roadmap of environmental changes in the PCV) (9/10)

No.102

ID: Sa-9 “Transfer of debris ②”
Cell (Y)Nitrogen

Inflow ofresidual
dust in the
air

Secondary boundary
Cooling water

Drainage ofcontaminated waterby waterdecontamination

Neutron absorbent supply
equipment for processing
work

NitrogenPurification gas
PCV atmosphere Pretreatment

DebrisD/W stagnant
water transfer
pump A/B

Decontaminati
on mechanism
Verification
mechanism
beforetransferringoutside the cell

No surface contamination orradiation disturbance of the sealed
canister after completion ofvoluntary inspection before
transferring outside the cell

HEPA filter

Exhauster

HEPA filter

Exhauster

To exhaust port

To watertreatment system

HEPA
filterHEPA
filterCharcoalfilterExhauster

Pretreatment
facility

HEPA
filterHEPA
filterCharcoalfilterExhausterD/W stagnant
water coarse
particles removal
equipment

PCV stagnant
water buffertank

PCV stagnant
water injectionpump

PCV stagnant
water discharge
pump[Detailed configuration of components]
CharcoalfilterPretreatment
facility

Mechanism for transfer
outside the cell

Intra-cell transfer
mechanism ②

facility

Stagnant water
DebrisSecondary boundary

Door mechanism
G/CellDoor mechanism R/Y

Nitrogen
Nitrogen
supplysystemDoor mechanism Y/GIntra-cell transfer
mechanism ①

Cell transfer
mechanism

Debris collection
mechanism

Cell (G)Contaminated water(decontamination)

Cell (R)To exhaust port

Cooler

To wastetreatment
systemTo wastetreatment
systemFlow of air
DemisterElectric
heater

Backwash dry
dust collection
equipment

CharcoalfilterHEPA
filterFlow of liquid
Primary boundary(*)*Boundaries in piping connected to the PCV are not shown©International Research Institute for Nuclear Decommissioning

Appendix 6.2.3.3-3: Debris retrieval model (roadmap of environmental changes in the PCV) (10/10)
ID: Sa-10 “Transfer of Debris”

No.103Cell (Y)Cell (R)Intra-cell transfer
mechanism ①

Cell transfer
mechanism

Secondary boundary

Cooling water

Neutron absorbent
supply equipment forprocessing work

Nitrogen

PCV atmosphere Pretreatment

Exhauster

HEPA
filterExhauster

To exhaust port

To watertreatment system
HEPA
filterHEPA
filterCharcoalfilterExhausterfacility

Pretreatment
facility

HEPA
filterHEPA
filterCharcoalfilterExhausterD/W stagnant
water coarse
particles removal
equipment

PCV stagnant
water buffertankStagnant water
DebrisD/W stagnant
water transfer
pump A/B

CharcoalfilterPretreatment
facility

Backwash dry
dust collection
equipment

PCV stagnant water
injection pump

PCV stagnant water
discharge pump

[Detailed configuration of components]

Electric
heaterHEPA
filterPurification gas

DebrisDemister

Mechanism for transfer
outside the cell

Verification
mechanism
beforetransferringoutside the cellContaminated water(decontamination)

Nitrogen

Decontamination
mechanism

Door mechanism Y/GNitrogen
supplysystemIntra-cell transfer
mechanism ②

Door mechanism R/Y

Nitrogen

Secondary boundary
Door mechanism
G/CellDebris collection
mechanism

Cell (G)CharcoalfilterCooler

To wastetreatment
systemTo wastetreatment
systemHEPA
filterTo exhaust port

Flow of air
Flow of liquid

Primary boundary(*)*Boundaries in piping connected to the PCV are not shown©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.1-1: Flow of study of environmental changes inside the PCV due to operational
equipment activities
No.104•••The environment inside the PCVchanges with the normal work using
operational equipment. A part of thischange becomes a disturbance tothe safety equipment.
This section quantifies theenvironmental changes inside thePCV that are candidates for
disturbances, as much as possible.
For quantification, knowledge fromdecommissioning of the Fukushima
Daiichi or light-water reactors (i.e.,
evidence data) will be collected andprocessed for application in thedebris retrieval model.
Here, processing refers tosimplification, recalculation basedon assumptions, and curtailingquantitative evidence data, etc.

Study of environmental
changes inside the PCV
due to operational
equipment activities

Safety equipment model:
Physical model of theenvironment inside the PCVSpecification of physical quantities thatare disturbances to safety equipment

Inputs for the
study

No

Does the Fukushima Daiichi
subsidized project have evidence
data that can be used to estimate thephysical quantity required?

Investigation of generalknowledge in the nuclear
power industry

Yes
Evidence data collection completed
Debris retrieval model:
Roadmap of environmental
changes inside the PCV

Settings for environmental
changes inside the PCVInputs forthe study

Can the evidence data
be used as is?

Yes
Completion of the table of environmental
changes inside the PCV

No

Simplification, recalculation
based on assumptions, andcurtailing quantitative evidencedata, etc.

Can this be addressed by adding
one's own assumptions in thecontinuous monitoring project?

Yes
Clearly indicate the data necessaryfor extracting important monitoring
items is insufficient©International Research Institute for Nuclear DecommissioningNoAppendix 6.2.4.1-2: Table of dynamic environmental changes inside the PCV due
No.105to operational equipment activities (1/11)■ Example calculation of environmental changes inside the PCV: When cutting fuel debris lumps (300 kg) with adisc cutter
M_fd = ρ_fd × V_fd = 1242.1[g]M_fd: Total amount of dust generated [g]ρ_fd: Hypothetical debris density [g/cm3] (=11)
V_fd: Deficit volume during processing of hypothetical debris [cm3] (=112.8)[Test data obtained from project of Development ofTechnology for Dust Collection System of Fuel
Debris]Deficit volume of test piece with 50 mm cut: 0.69 cm3→ Deficit volume per 1mm cut: 0.0138 cm3/mm[Total cutting length of
hypothetical debris]
1168 mm × 7 times = 8176 mm

8176 ×0.0138=112.8 [cm3]Hypothetical fuel debris

Cutting line using adisc cutter

Cutting
direction
Cutting length
50 mm

20
1168 (cut five times)[mm]*For the sake of simplification, dimensions shown do not match the scale

Reference: Project of Development of Technology for
Dust Collection System of Fuel Debris©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.1-2: Table of dynamic environmental changes inside the PCV
due to operational equipment activities (2/11)

No.106- The following pages show a table of dynamic environmental changes inside the PCV during fuel debris processing
using the operational equipment.
Abbreviations used in the table are explained below.
[Dust collection]
Direct utilization of data from project of Development of Technology for Dust Collection System of Fuel Debris[Investigation of dust collection]
Direct utilization of research results of other projects by Development of Technology for Dust Collection System ofFuel Debris Project[Dust collection theory]
Utilization of theoretical calculation values from Development of Technology for Dust Collection System of Fuel
Debris Project[CRIEPI: Central Research Institute of Electric Power Industry]
Direct utilization of the knowledge of the Handbook on Environmental Impact Assessment for Decommissioning
Work (third edition), Central Research Institute of Electric Power Industry, March 2007
[Internal investigation]
Direct utilization of knowledge from Development of Technology for Investigation inside the Reactor Pressure Vessel(RPV) Project[Monitoring]
Settings with assumptions made by project of Development of Continuous Monitoring System in PCV[Retrieval]
Direct use of project‘s knowledge in the Development of Technology for Further Increasing the Retrieval Scale of
Fuel Debris and Reactor Internals Project[Note 1]
Due to lack of data, the mass balance for metal processing obtained from [CRIEPI] was applied©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.1-2: Table of dynamic environmental changes inside the PCV due to operational equipment activities (3/11)

No.107
Table of environmental changes inside the PCV due to operational equipment activities (during fuel debris processing) (1/9)* Of the 10 hours of work hours during the day, the net processing time is deemed
to be 3.3 hours

A

B

C

D

E F

[g]

AmountMass balanceof dustmigration

---

T

U

V

Amountof dustmigration

Mass balance

[g]

6

39.3

0.0

651.9

3.3

2.00E
-05

47

307.9

99.5

47

307.9

[Monitoring][%][Central Research Institute ofElectric Power Industry]---

Floating in water---[Central ResearchInstitute of ElectricPower Industry][g]

Sedimentation[%]

Airborne[Dustcollection
theory]Above 50---

0.5

[Dust collection][Dust655. 655.16
collection 16
theory]50 or less[Monitoring]

---

S

W

X Y

Underwater processing[Dust collection]

---

[g]

R

Aerial processing

Peripheral dispersion

---

[μm]

Q

Z

AA AB

AC

AD AE

Mass balance and amount of dust migration

Sedimentation

All in median
diameter[Dust collection]
0.5 (number
distribution)[Dust collection]
32.3 (sediment
distribution)

O P

Airborne

All in range ofpeak particle size
[dust collection] 2
to 3 (massconcentration
distribution)[Dust collection]
0.1 to 0.3 (number
concentration anddistribution)---N

Total amountof dustgenerated

Underwater
processing

5

[μm]

---

Cutting Chipping4---

Sedimentation

3

M

Aerial processing (no Underwater
anti-dispersion agent) processing

Floating in water

2

L

Dust particle size,Bladethicknes
s: 1 mm
Numberofrevolutio
ns: 1000rpm

K

Sedimentation

Disc cutter

Cutting

Inside the RPV

Fuel

Blade
diameter
: 200
mm

J

Airborne[MPa]

11 [Characterizatio [Characten]rization]
Stump fuel: 230 UO2,ZryUnmolten fuel: 2,(U,Zr)O
280
2-C,(Zr,U)O2T,Zr(O),Fe

I

Aerialprocessing

Remarks

Equipment name

Processing mode

Localized area

Primary component

Compressive
strength

Density

Fuel debris type
1

H

Assumed processing
methods

Assumed properties[g/cm3]

G

Amount ofprocessing aid
injected

Amount of antiscattering agent
injected(Only for aerial
processing)

Total
Total
Input materials amount Input materials amount ofof input
input

[Dust
198 L [Dust(*)
collection]collection][Aerial(*)
processing
Mist: 0.05]
L/min
Water: 1
L/min

9.9

Others

Input materials

L [Dust(*)

Total amountof input

102 °C

collection]
Temperatureof fuel debris
duringprocessing

No data

AWJ--Lasergouging

No data---©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.1-2: Table of dynamic environmental changes inside the PCV due to operational equipment activities (4/11)
Table of environmental changes inside the PCV due to operational equipment activities (during fuel debris processing) (2/9)

No.108* Of the 10 hours of work hours during the day, the net processing time is deemed to be
3.3 hours

A

B

C

D

E

Assumed properties

G

H

M

N

O

Total amount of
dust generated

P

Q
R
S T
U
Mass balance and amount of dust migration

Aerial processing

[g]

[g]

---

---

[%]

[g]

All in range ofpeak particle
size
[Dust
collection] 2 to
3 (mass
concentration
distribution)[Dustcollection] 0.1
to 0.3 (number
concentration
anddistribution)

1242.11242.149.7

All in median
diameterEitherairborne/sedim
entation

459.6

59

732.9

Mass balance---

Airborne

Peripheral
dispersion

37[Monitoring]

Sedimentation

Floating in water[Dustcollection
theory]50 or less4

[Dust collection]

Airborne

Sedimentation[Dust
collection
theory]Above 50

Amount of
dust
migration[Dust collection]

Airborne

Sedimentation[Dust collection]
0.3 (number
distribution) [Dustcollection] 7.9(sediment
distribution)

Unknown

X

Y

Amount of processing
aid injected
Amountof dustmigration
Total amountof input

Floating in water[g]

Input materials

0.0[Aerialprocessing]Water: 1
L/min

198

[Base][Both in air
andunderwater
processing]Water: 36
L/min

712
8

2.00E-05

99.5

1235.9

0.5

6.2

0.00
9

0.8

2.00E-03

0.2[Investigation of dust collection]

8938.6

Airborne8938.6[Investigation of dust collection]

Unknown

Airborne[Base] 0.096
to 3.3

Airborne

Laser gouging

[%]

Z

AA AB

AC

Amount of antiscattering agent
injected(Only for aerial
processing)Input
materials

Totalamount of
input

L
[Dust
(*)

Others

Input materials

L ---collection]
Mist: 0.05
L/min

AD AE

Total amountof input---(*)

No data
Airborne

Chipping---[Central ResearchInstitute of ElectricPower Industry][μm]

Mass balance

W

Underwater processing[Monitoring]

Underwater
processing---

Underwater
processing

V[Central Research Institute of ElectricPower Industry]

Aerialprocessing[μm]

Peripheral
dispersion

Cutting

10

L

---

Aerial processing(no anti-dispersion
agent)

Number of
revolutions:1000 rpm

Processing
speed: 2 m/min
Irradiation beam
diameter:approx. Φ5 mm
Processing pitch:
2.5 mmDistance
betweenworkpieces: 40
mm

K

Dust particle size,Bladethickness: 1
mm

AW --J

J

Sedimentation

Blade
diameter:
200 mm8

9I

Airborne

Remarks

Cutting

Equipment name Disc cutter

Processing mode

Pedestal inside the PCV (floor/inside/outside) drywell

11 Craft and [U-rich]on the(U,Zr)O2bedrock
C,(Zr,U)O(uppersection):2 2-T, [Ferich]000
Other than UO2,
above
Fe,Zry-2,
mentioned α-Zr(O),: 230
SUS/Fe,Fe2(Zr,U), ZrB2,Fe2B,
Zr(O),
Fe2Zr

Localized area

[MPa]

Primary
component

Compressive
strength

Mass of fuel debris
7

Density

Fuel debris type6

[g/cm3]F

Assumed processing
methods

L
(*)

---

---

--- [Base][Both in air
andunderwater
processing]
20 kW

396
0

©International Research Institute for Nuclear DecommissioningkJ(*)

Appendix 6.2.4.1-2: Table of dynamic environmental changes inside the PCV due to operational
equipment activities (5/11)
No.109
Table of environmental changes inside the PCV due to operational equipment activities (during fuel debris processing) (3/9)* Of the 10 hours of work hours during the day, the net processing timeis deemed to be 3.3 hours

A

B

C

D

E

F

I

J

R

S

T

U

V

W

X

Y

Z

AA AB

A
AD E

AC

Mass balance and amount of dust migration
Aerial processing

MassbalanceAmount of
dust
migrationMassbalanceAmount of
dust
migration

8205.68143.1[Base]
0.096 to1.1---

Underwater dissolution

91.1

8.2

733.0

[Investigation of dust collection][Base]
8938.6 8938.6
Less than
4 mm,
250 μm to
1 mm ismost
dominant,
followedby less
than 250μm[Investigation of dust collection][g]

Underwater dissolution[%]

Floating in water---[Investigation of dust collection]

---

91.8

Sedimentation

[g]

8.1

724.0

[Investigation of dust collection][%][Investigation of dust collection]---[Investigation of dust collection]---

Distance
betweenworkpieces:
40 mm

Amount of antiscattering agent
injected(Only for aerial
processing)

Underwater processing

Underwater dissolution

---

[g]

Q

Floating in water[Dustcollection
theory]50 or less[g]

P

Sedimentation[Base]
Less than 4
mm, 250 μm to1 mm is mostdominant,
followed by lessthan 250 μm[μm]

Underwater
processing---

O

Floating in water

[μm]

M
N
Total amountof dustgenerated

Sedimentation---

Underwater dissolution

Processing
pitch: 2.5 mm

Aerial processing
Underwater(no anti-dispersion
processing
agent)

Floating in water

Irradiation
beam
diameter:approx. Φ5mm

LDust particle size,

Sedimentation

Laser gouging

Processing
speed: 2
m/min

K

Aerialprocessing

Remarks

Equipment name13

Cutting

12

Processing mode

ZrB2,
Fe2B,
Zr(O),
Fe2Zr

Pedestal inside the PCV (floor/inside/outside) drywell

Craft, on [U-rich]bedrock (U,Zr)O2(upper C,(Zr,U)O2section): T, [Fe-rich]
2000 UO2,
Other Fe,Zry-2, αthan
Zr(O),above
SUS/Fe,mentioned: 230 Fe2(Zr,U),

Localized area

Compressive
strength

Mass of fuel debris

11

Primary component

Density

Fuel debris type
11

[MPa]

H

Assumed processing
methods

Assumed properties[g/cm 3]

G

0.05

4.5

0.04

3.6

Amount ofprocessing aid
injected

Input
materials[Base][Both in air
andunderwater
processing]Water: 36
L/min

Total
Total
Input
amount ofamountmaterials
input
of input

7128

L
(*)

---

OthersInputmaterials--- --- [Base][Both in air
andunderwater
processing]
20 kW

Total amountof input

3960©International Research Institute for Nuclear DecommissioningkJ(*)

Appendix 6.2.4.1-2: Table of dynamic environmental changes inside the PCV due to operational equipment
activities (6/11)
No.110
Table of environmental changes inside the PCV due to operational equipment activities (during fuel debris processing) (4/9)* Of the 10 hours of work hours during the day, the net processing time is deemed tobe 3.3 hours

A

B

C

D

E

Assumed properties

G

I

J

L

M

N

O

P

Q

R

S

T

U

V

W

X

Aerial processing

AA AB

AC

Aerialprocessing

Underwater
processing

---

[μm]

[g]

[g]

---

---

[%]

[g]

---

---

[%]

[g]

Input materials[Dustcollection
theory]40 or less

83922

83922

Airborne

2.4

0.0

[Dust
138
collection]
6[Aerialprocessing]Water: 1
L/min

SUS304; [125μm or more]
125 to 500
μm is
dominant[125 μm or①
less] 1 to 110
μm is
dominant[Investigation of dust collection] [Monitoring]

0.003

Sedimentation
Sedimentation

Amount of antiscattering agent
Amount of processing
injected
aid injected
Amount(Only for aerialof dustprocessing)migration[μm]

Underwater
processing

Z

AD AE

Underwater processing---

Aerial processing(no anti-dispersion
agent)Y

Mass balance and amount of dust migration

Total amount of
dust generated

Airborne

Mass balance

419.6[Monitoring]-

0.5

Sedimentation-[Central Research Institute of ElectricPower Industry]

Sedimentation

Sedimentation---[Dust
collection
theory]50 or less

2.00E-05

Underwater migration

Underwater migration[Dust
collection
theory]50 or less

Mass balance[Central Research Institute ofElectric Power Industry]

UnknownAmount of
dust
migration

Airborne

Floating in waterCore boring

Crushing

Pedestal inside the PCV (floor/inside/outside) drywell

Jig type:
Impregn
ated bits
Numberofrevolutio
ns: 150
to 300rpm
Drilling
speed:
2.86
mm/minDiameter
: Φ66
mm
Feed
pressure: 15 kN

K

Dust particle size,

Aluminumoxide;[125 μm ormore] 125 μm
is dominant[125 μm or②less] 0.3 to 80
μm is
dominant

16

ChiselCrushing

17

H

Remarks

Equipment name

Processing mode

11 Craft, on [U Rich]
bedrock (U,Zr)O2(upper
C,(Zr,U)O
section): 2-T, [Fe2000
rich]
Other
UO2,
than
Fe,Zry-2,above
α-Zr(O),
mentione SUS/Fe,
d: 230Fe2(Zr,U), ZrB2,Fe2B,
Zr(O),
Fe2Zr

Localized area

[MPa]

Primary component

Compressive
strength

Mass of fuel debris

15

Density

Fuel debris type14

[g/cm3]F

Assumed processing
methods

99.99783919.9

---

---

99.5

83502.7

Total amountof input

L

OthersInputmaterials

Totalamount of
input

Input materials

Unknown- ----Total amountof input---(*)

No data©International Research Institute for Nuclear Decommissioning---

Appendix 6.2.4.1-2: Table of dynamic environmental changes inside the PCV due to operational equipment
activities (7/11)
No.111
Table of environmental changes inside the PCV due to operational equipment activities (during fuel debris processing) (5/9)* Of the 10 hours of work hours during the day, the net processing time isdeemed to be 3.3 hours

A

B

C

D

E

H

I

L

M

[g]

AmountMass balance of dust
migration

---

T

U

V

W

X

Y

Mass balance

Amountof dustmigratio
n

---

[%]

[g]

7

113.2

0.0

43

695.1

99.5

1608.4

50

808.2

0.5

8.1

[Dust collection]

2.00E-05[Central Research Institute ofElectric Power Industry]---

Floating in water[g][Monitoring][%]

Sedimentation

---

---

Underwater processing[Central Research Institute of Electric Power
Industry][Monitoring]Above 45

Peripheral dispersion[Dust collection][Monitoring]---S

Airborne[Monitorin 3407. 3407.
g]
9945 or lessSedimentation

Peripheral dispersion

Eitherairborne/sediment
ation

[g]

R

Aerial processing

Airborne

Sedimentation

All in median
diameter[Dust collection]
0.5(number
distribution)[Dust collection]
41.5(sediment
distribution)[μm]

Sedimentation

All in range ofpeak particle size
[Dust collection] 2
or more (massconcentration
distribution)[Dust collection]
0.1 to 0.3(number
concentration anddistribution)

---

Q

Z

AA AB

AC

AD AE

Mass balance and amount of dust migration

Floating in water

[μm]

O P

Underwater
processing

Aerial processing (no Underwater
anti-dispersion agent) processing

---

N

Total
amount ofdust
generated

Dust particle size,

19

20

K

Airborne

Disc cutter

Cutting

Pedestal inside the PCV (floor/inside/outside)

Similarto matrix
1H

J

Aerialprocessing

Remarks

Equipment name

Processing mode

1300
Fe,B4CCore
supportplate

Localized area

Compressive
strength

Existing structures8

Primary component

Density

Fuel debris type
18

[MPa]

G

Assumedprocessing methods

Assumed properties[g/cm 3]

F

Amount of antiscattering agent
injected(Only for aerial
processing)Amount ofprocessing aid
injected

Input
materials

Totalamount of
input

[Dust
198
collection][Aerialprocessing]
Water: 1
L/min

Total
Input
amount ofmaterials
input

L [Dust(*)

collection][Aerialprocessi
ng]
Mist:
0.05
L/min

9.9 L

OthersInputmaterials

---

Total
amount of
input

---

(*)

©International Research Institute for Nuclear Decommissioning---

Appendix 6.2.4.1-2: Table of dynamic environmental changes inside the PCV due to operational equipment
activities (8/11)
No.112
Table of environmental changes inside the PCV due to operational equipment activities (during fuel debris processing) (6/9)* Of the 10 hours of work hours during the day, the net processing timeis deemed to be 3.3 hours

A

B

C

D

E

F

J

K

L

[Dust
collection
theory]Above 20

Floating in water

Unknown

[g]

[g]

Q

R

S

T

U

V

W

Aerial processing

Mass balance

Amountof dustmigration

Mass balance

Amount of
dust
migration

Y

Z

AA AB

AC

AD AE

---

97

2861.5

Particle
size
[mm]:

[Central Research Institute ofElectric Power Industry][Monitoring]
Above 45

2.00E-05[Monitoring]

0.0

97

2861.5

3

88.5

Input
materials

Floating in water

0.0

2.E-05Total
amountof input

Sedimentation[Monitoring] 2950 2950
45 or less

Total
Input
amount ofmaterials
input

Others[Central Research Institute ofElectric Power Industry][g]

Airborne[%][Central Research Institute ofElectric Power Industry]---

Floating in water---[Monitoring][g]

Sedimentation[%][Central Research Institute ofElectric Power Industry]---

Amount of antiscattering agent
injected(Only for aerial
processing)Amount ofprocessing aid
injected

Input
materials

---

---

X

Underwater processing

Airborne[Monitoring]
20 or less

[μm]

P

Mass balance and amount of dust migration

Sedimentation---O

Floating in water[μm]

Underwater
processing

Underwater
processing---

N

Aerialprocessing

Aerial processing(no antidispersion agent)M

Total amountof dustgenerated

Dust particle size,

Sedimentation

Jetpressure: 343
MPa
Cutting
speed:
50
mm/minDistance
betweenworkpieces:
approx.
2 mm
Nozzleangle: 0deg

23

Laser gouging

Chipping

24

I

Airborne

Cutting

Pedestal inside the PCV (floor/inside/outside)

AWJ

Remarks

Equipment name

Processing mode

8 1300
Fe,B4CCore
supportplate

Localized area

Primary component

Compressive
strength

MCCI formations

22

Density

Fuel debris type
21

[MPa]

H

Assumedprocessing
methods

Assumed properties[g/cm 3]

G

3

88.5

Mesh width
0.18 mm(nominal),
less than
0.45 mm[Internal733
investigati
on][Underwat
er
processing]
Water: 3.7
L/min

L
(*)

---

--- --- Internal

Total
amount of
input

99

kg

investigation][Underwat
er
processing]
Garnet:
500 g/minNo dataWith
waterflow asprocessi
ng aid©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.1-2: Table of dynamic environmental changes inside the PCV due to operational equipment
activities (9/11)
No.113
Table of environmental changes inside the PCV due to operational equipment activities (during fuel debris processing) (7/9)* Of the 10 hours of work hours during the day, the net processing
time is deemed to be 3.3 hours

A

B

C

D

E

F

Assumed properties

K

L

Dust particle size,

T

U

V

[g]

6

[Dust
collection
theory]Above 50

Sedimentation[Dust collection]

37

204.5

1260.9

W

X

Y

Z

AA AB

AC

AD AE

[%]

[g]

2.00E05

0.0

99.5

3390.8

0.50

17.0

1

Amount ofprocessing aid
injected

Input
materials

Amount of antiscattering agent
injected(Only for aerial
processing)

Total
Total
Input
amount ofamountmaterials
input
of input[Dust
198 L [Dust
9.9 L
(*)
(*) collectiocollection][Aerialn]processin[Aerialg]
process
Water: 1
ing]
L/min
Mist:
0.05
L/min

OthersInputmaterials

Totalamount of
input

---

--- ---

1

57

1942.5

Floating in water[Monitoring]---

Peripheral dispersion

Peripheral dispersion--- ---[Monitoring] Note[%]

Mass balance[Central Research Institute of ElectricPower Industry] Note--- ---

Amount of
dust
migration

Sedimentation[g]

Underwater processing[Central Research Institute of Electric Power Industry]
Note

[g]

[Dust 3407.9 3407.9
collection]: 0.5(number
distribution)[Dustcollection]: 5.2(volumedistribution)Either--airborne/sedi
mentation

S

Airborne

AmountMass balance of dust
migration[Dust collection]

All in median
diameter[Dustcollection]
0.6(number
distribution)[Dustcollection]
8.4(sediment
distribution)

R

Aerial processing

Airborne

All in rangeof peak
particle size
[Dustcollection] 2
to 3 (massconcentrationdistribution)[Dustcollection]
0.1 to 0.3(number
concentratio
n and
distribution)

Q

Underwater
processing--- [μm]P

Mass balance and amount of dust migration

Aerialprocessing--- [μm]O

Sedimentation

Underwater
processing

M
N
Total amountof dustgenerated

Floating in water

Aerialprocessing (noanti-dispersion
agent)

26

27

J

Sedimentation

Remarks

Disc cutter

Cuttersize,
numberofrevoluti
ons

I

Airborne

Equipment namePedestal floor drywell

Cutting(U,Zr)O
2C,(Zr,U)
O2-T,
Al-CaSiO,Fe,Si
O2,(Zr,U)SiO4

Processing mode

22

Localized area

MCCI formations
25

3.86

Primary component

Compressiv
e strength

Density

Fuel debris type[g/cm 3] [MPa]G
HAssumedprocessing
methods

1©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.1-2: Table of dynamic environmental changes inside the PCV due to operational
equipment activities (10/11)
No.114
Table of environmental changes inside the PCV due to operational equipment activities (during fuel debris processing) (8/9)* Of the 10 hours of work hours during the day, the net processing
time is deemed to be 3.3 hours

A

E

H

I

J

Assumed processing
methods

K

L

Dust particle size,

---

[μm]

---

[μm]

Underwater
processing

Aerialprocessing (no Underwater
anti-dispersion processing
agent)

M
N
Total amountof dustgenerated

Aerialprocessing

Remarks

8 1300 Fe,B
Core 4C
supportplate

Pedestal floor drywell

[MPa]

G

Equipment nameLocalized area[g/cm 3]F

Processing mode

Primary component

[g]

[g]

O

P

Q

R

S

T

Aerial processing
AmountMass balance of dust
migration

Mass balance

---

---

---

[%]

[g]

---

W

X

Y

---

35901.1

961.7

1.07

97.35 35327.7[Monitoring][Monitoring]Less than 10
mm

388.3

2.65

Sedimentation[Dust
36289 36289
collection
theory]150 orless[Monitoring]

Jig type:
Air drive
systemBlows perminute:1250 bpm
Total
Length:480 mmJigarrangem
ent: 2chisels inparalleloperation

Inputmaterials

Airborne

Crushing

Chisel[g][Monitoring]

No dataAmount of
dust
migration

Amount ofprocessing aid
injected[%][Monitoring]---

Sedimentation

CrushingCoreboringAirborne

No data

Sedimentation---

Floating in waterLasergouging

Sedimentation

No data

Airborne---[Monitori
ng]
10 mm
Less
than

V

Underwater processing

AWJ

[Dust
collection theory]
40 or
less

U

Z

AA AB

AC

AD AE

Mass balance and amount of dust migration

Cutting Chipping

31

D

Assumed properties

Compressive
strength

30

Existing structures

29

C

Density

Fuel debris type
28

B

98.93

Amount of antiscattering agent
injected(Only for aerial
processing)

Total
Total
Input
amount ofamountmaterials
input
of input------ Unknown --- ---OthersInputmaterials

---

Total
amount of
input

---

---

32

©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.1-2: Table of dynamic environmental changes inside the PCV due to operational
equipment activities (11/11)
No.115
Table of environmental changes inside the PCV due to operational equipment activities (during fuel debris processing) (9/9)* Of the 10 hours of work hours during the day, the net processing
time is deemed to be 3.3 hours

A

B

C

G

H

I

J

L

Dust particle size,

M
N
Total amountof dustgenerated

O

P

Q

R

S

T

U

V

W

Aerial processing

Underwater
processing

[μm]

---

[μm]

[g]

[g]

---

---

[%]

[g]

---

---

[%]

[g]

Input
materials

---

---

[Retrieval]
0.48 μm*With
neutronabsorbent

---

---

-

-

---

---

-

-

---

---

---

Underwater
processing

Y

Underwater processing---

Aerialprocessing(no antidispersion
agent)

X

Z

AA AB

AC

AD AE

Mass balance and amount of dust migration

Aerialprocessing

Chisel

Jig type:
Electric flat
chisel Width:
32 mm
Impact force:
20 J/time
Full load
blows perK

Floating in water

Remarks

Equipment nameSprayed on fuel debris

Crushing[Neutronabsorbent]
Sodiumsilicate1,
cement,primary
sodiumphosphate,water,
gadolinium
oxide

Processing mode

Localized area

With neutron absorbent (TXMCCI formations

2.1 ---F

Assumed processing
methods

Primary component

Compressive
strength

Density

Fuel debris type
)

10

E

Assumed properties[g/cm 3] [MPa]

33

D

Mass
balanceAmount ofAmount of
dust
Mass balance
dust
migration
migration

Amount ofprocessing aid
injected

Amount of antiscattering agent
injected(Only for aerial
processing)

Total
Total
Input
amount ofamountmaterials
input
of input

---

-

---

OthersInputmaterials

Totalamount of
input--- --- [Retrieval] 3
Amount ofneutronabsorbent
injectedLminute: 2200
bpm
Crushing
depth:
approx. 5 cm

©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.1-3: Impact study on methods due to static environment inside thePCV (1/14)

No.116(i) Static environmental changes inside the PCV➢

The amount of gas and radioactive leakage from the PCV, which is a control parameter for the static
boundary function, depends on the size of the PCV opening. Therefore, an increase in the size of the
PCV opening is extracted as one of the risks in the section of the Study of the safety equipment model.

➢

It is conceivable that deterioration events for PCV under static environment may increase the size of the
opening of existing damaged sections and generate new damaged sections.

➢

Corrosion phenomena are cited as static environmental changes that cause these deterioration events.

➢

Since the inside of the PCV is in a highly humid environment, it is expected that the liquid film will

adhere to the walls in the gas phase and corrosion of the PCV wall surface will occur not only in theliquid phase where stagnant water exists and at the gas-liquid interface, but also in the gas phase.
➢

Therefore, the previous findings on corrosion phenomena assumed inside the PCV will be investigated,and based on the investigation results, whether corrosion phenomena can be extracted as an importantmonitoring item or not will be studied.

©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.1-3: Impact study on methods due to static environment inside
No.117the PCV (2/14)(i) Static environmental changes inside the PCV(a) Investigation results of previous findings (① Corrosion behavior of carbon steel in the liquid phase
section)➢In the liquid phase, 4.4 kGy/h gamma radiation increased the corrosion weight loss of carbon
steel by 1.7 times compared to the non-irradiation condition, and 0.2 kGy/h gamma radiation
was almost the same as the non-irradiated conditions. 1)(Figure 1)*

Figure 1 Effect of gamma radiation on corrosion rate of carbon steel (50°C) 1)(Source) 1) Nakano et al., Corrosion of carbon steel and low-alloy steel in diluted seawater containing hydrazine under gamma-rays irradiation, Journal of JapanesePapers of Japan Atomic Energy Agency (In Japanese), 13, 1, pp.1-6, 2014.
©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.1-3: Impact study on methods due to static environment inside the PCV (3/14)

No.118(i) Static environmental changes inside the PCV(a) Investigation results of previous findings (② Corrosion behavior of carbon steel in the area of liquid film adhesion in
the gas phase section)➢

It was verified that the corrosion rate increases when the liquid film thickness is approximately 10 to 100 μm whenin the gas phase environment with liquid film adhesion. 2)~4)(Figure 2)➢

In a corrosion test in a gamma radiation environment in which a liquid film adhered to the inner surface of acylindrical container, the maximum corrosion depth under the liquid film corrosion environment in the gas phase isapproximately 1.9 times that of the liquid phase. It was verified that the maximum corrosion depth under the liquidfilm corrosion environment in the gas phase is approximately 1.8 times at 4 kGy/h and approximately 1.5 times at
0.2 kGy/h that of the non-irradiated conditions due to the superimposed irradiation. 5)6)

Figure 2 Relationship between corrosion rate and liquid film thickness(a) Data from Hosoya et al. (b) Tomashov's model 2)(Source)2) Hosoya et al., Zairyo-to-Kankyo (Materials and the Environment)(in Japanese), 54, pp.391-395, 2005.
3) Katayama et al., Relationship between corrosion rate of steel and water film thickness under thinlayer of artificial seawater, Journal of Japan Institute of Metals, 65, 4, pp. 298–302, 2001.
4) Yamamoto et al., Continuous Corrosion Rate Measurement of Carbon Steel in Outdoor Environment
Using AC-Impedance Method , Journal of Japan Institute of Metals, 65, 6, pp.465–469, 2001.
5) Tsuchiya et al., “Corrosion evaluation of carbon steel piping in gas-liquid humid environment,” Zairyoto-Kankyo (Materials and the Environment) 2021, A-106, 2021.
6) Tsuchiya et al., “Impact Assessment of Irradiation Effects on Corrosion Behavior of Carbon Steel
Under Atmospheric Humidity,” 68th Symposium on Materials and the Environment 2021, C-112, 2021.
©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.1-3: Impact study on methods due to static environment inside the PCV (4/14)

No.119(i) Static environmental changes inside the PCV(a) Investigation results of previous findings (③ Corrosion behavior of carbon steel at the gas-liquid interface)➢In the semi-immersion test, it was verified that the corrosion rate near the gas-liquid interface was 2.8 to 3.0 times
greater than that in the liquid phase, and the irradiation increased the corrosion rate at the gas-liquid interface by 1.61
times. 7)(Figure 3)

Figure 3 Results of corrosion rate evaluation of the test piece in each region under irradiation (2.11 kGy/h) and non-irradiated conditions after 336h7)(Source) 7) Abe et al., “Corrosion Rate and Long-term Prediction of Carbon Steel at Water Line under Gamma Ray Irradiation,” 67th Symposium on Materials and theEnvironment 2020, A-309, 2020.
©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.1-3: Impact study on methods due to static environment inside the PCV (5/14)

No.120(i) Static environmental changes inside the PCV(a) Investigation results of previous findings (③ Corrosion behavior of carbon steel at gas-liquid interface)➢

In a corrosion test in a gamma radiation environment in which a liquid film
adhered to the inner surface of a cylindrical container, the maximum corrosion
depth of the gas-liquid interface in a non-irradiation environment wasapproximately 5.7 times that of the liquid phase. It was verified that the maximum
corrosion depth at the gas-liquid interface is approximately 1.7 times greater at 4
kGy/h and approximately 1.2 times greater at 0.2 kGy/h due to the superimposed
irradiation. 6)(Figure 4)➢

It was verified that the corrosion rate in air-solution alternating condition is 3 to 5
times greater than that in the liquid phase. In addition, it was verified that thecorrosion rate in air-solution alternating condition does not increase linearly withincreasing oxygen concentration in the air, and that the slope in the low

Figure 4 Relationship between cylindricalcontainer height and maximum erosion depth(gamma radiation, 500h) 6)

concentration range (0 to 5%) is greater than that in the high concentration range(5 to 20.8%). 8)9)(Source)6) Tsuchiya et al., “Impact Assessment of Irradiation Effects on Corrosion Behavior of Carbon Steel Under Atmospheric Humidity,” 68th Symposium on Materials and the Environment 2021, C-112, 2021.
8) Ohtani et al., “Effects of seawater components on corrosion rate of steel in air/solution alternating condition,” Zairyo-to-Kankyo (Materials and the Environment), 69, pp.246-252, 2020.
9) Ohtani et al., “Effect of oxygen concentration on corrosion rate of carbon steel in air/solution alternating condition,” 67th Symposium on Materials and the Environment 2020, A-308, 2020.
©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.1-3: Impact study on methods due to static environment inside the PCV (6/14)

No.121(i) Static environmental changes inside the PCV(b) Summary of investigation results of previous findings and data expansion policy,➢

It was shown that the corrosion rate of the gas phase section under liquid film adhesion increased by approximately 1.9 times that of
the liquid-phase section, and furthermore, there is a possibility that the superimposed irradiation may increase the corrosion rate by
up to approximately 1.8 times. Based on the corrosion rate in the liquid phase, there is a possibility that the corrosion rate may
increase by approximately 3.4 times in an irradiation environment with liquid film adhesion.

➢

It was shown that the corrosion rate at the gas-liquid interface increased by a maximum of approximately 5.7 times that of the liquid
phase, and furthermore, there is a possibility that the superimposed irradiation may increase the corrosion rate by up to 1.7 times.
Based on the corrosion rate in the liquid phase, there is a possibility that the corrosion rate may increase by approximately 9.7 times
at the gas-liquid interface in an irradiation environment.

➢

Considering these increased corrosion rates, it is possible that the PCV wall, which is the boundary, could rapidly erode and thin out,
and the corrosion phenomenon could potentially be a factor that impedes fuel debris retrieval operations.

➢

In this project, some material tests will be conducted for the purpose of verifying the previous findings, and based on the expandedfindings and the results of the investigation of previous findings, corrosion events will be examined to see if they can be extracted asimportant monitoring items.
©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.1-3: Impact study on methods due to static environment inside the PCV(7/14)

No.122(ii) Status of studies related to corrosion evaluation of structures(a) Corrosion test
➢ From the results of the investigation of previous findings in item (i), it wasverified that the corrosion rate increases when there is a liquid film on thesurface.
➢ On the other hand, there are many unclear points about corrosion behavior

in the presence of a thin liquid film in an irradiation environment.
➢ Therefore, in order to evaluate the effect of irradiation dose rate on the
corrosion behavior of carbon steel in the presence of a thin liquid film, a

corrosion test under γ-ray irradiation was conducted on test pieces with aliquid film of a certain thickness formed on the surface.

©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.1-3: Impact study on methods due to static environment inside the PCV (8/14)(ii) Status of studies related to corrosion evaluation of structures

No.123(a) Corrosion test
➢ Test conditions
 Test material: carbon steel (JIS G 3118 SGV480) (Table 1, Figure 5) Temperature: room temperature Time: 50, 100, 500 h
 Dose rate (gamma rays): 0, 0.2, 3 kGy/h Liquid film thickness: 0.4, 4, 30, 40 μm (control method is described below)
 External appearance of test equipment: See Figure 6
Desiccator

Table 1 Chemical composition of test material (wt.%)

Type of
steel

C

Si

Mn

P

S

JIS G 3118
SGV480

≦
0.27

0.15
~0.40

0.85
~1.20

≦
0.020

≦
0.020

test
piece
installation jig
Test piece

Analyzed
value

0.10

0.16

1.43*

0.014

0.003

*: “For every 0.01% decrease in the upper limit of C, the upper limit of Mn
may be increased by 0.06%. However, JIS states, “the maximum value of Mn
is 1.60%,” and this satisfies the standard.

Saturated aqueous solution

Figure 5 Shape of test piece

Figure 6 Illustration of test equipment©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.1-3: Impact study on methods due to static environment inside the PCV(9/14)(ii) Status of studies related to corrosion evaluation of structures

No.124(a) Corrosion test➢

Method of controlling liquid film thickness• Controlled by the amount of sea salt particles adhering to the surface of the test piece and the relative
humidity inside the test container (Figures 7 and 8)• When a saturated aqueous solution of salt is present in a sealed container, it is possible to create an
atmosphere of constant relative humidity depending on the type of salt (Table 2)
Polyimide tape① Before test

② Tape is applied around the perimeter
Surface to be tested: 35 x 35 mm

Solution

Sea salt particles④

The solution is dried and sea
salt particles are precipitatedFigure 8 Sea salt particle adhesion procedure
Table 2 Measured values of various salts at a fixed point of humidity in the test matrix10)

Fig. 7 Evaluation results of liquid film thickness when sea salt
particle adhesion and relative humidity are varied2)(Source) 2) Hosoya et al., Zairyo-to-Kankyo (Materials and the Environment), 54, pp.391-395, 2005.
10) Kitano et al., A Method to Realize Humidity Fixed Points by Saturated Salt Solutions, Transactions of the Society of Instrument and Control Engineers, 23, 12, pp.1246-1253, 1987.
©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.1-3: Impact study on methods due to static environment inside the PCV (10/14)

No.125(ii) Status of studies related to corrosion evaluation of structures(a) Corrosion test
➢ Test matrix
40 mm

4 mm

0.4 mmRelative Sea salt
humidity particle Liquid film Test
Dose rate
Number
No. Test piece Temperature(%)
adhesion thickness duration(kGy/h)of Namount(μm)(h)(g/m2)
1
59
1
0.4
2
84
1
4
50
3
3
75
10
30
4
84
10
40
5
59
1
0.4
0
6
84
1
4
(non100
3
7
75
10
30
irradiated)
8
84
10
40
9
59
1
0.4
10 SGV480
84
1
4
Room
500
3
Slab
temperature
11
75
10
30
12
84
10
40
13
59
1
0.4
14
84
1
4
0.2
500
3
15
75
10
30
16
84
10
40
17
59
1
0.4
18
84
1
4
3
500
3
19
75
10
30
20
84
10
40

30 mm

Table 3 Test matrix

Figure 9 Comparison of target liquid film thickness andprevious findings2)➢

Evaluation on the effect of liquid film
thickness on the amount of corrosion by
setting the liquid film thickness as aparameter (Figure 9)➢

Evaluation on the effect of irradiation doseon the amount of corrosion by setting theirradiation dose as a parameter(Source) 2) Hosoya et al., Zairyo-to-Kankyo (Materials and the Environment), 54, pp.391-395, 2005.

©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.1-3: Impact study on methods due to static environment inside the PCV (11/14)

No.126(ii) Status of studies related to corrosion evaluation of structures(a) Corrosion test
➢ Corrosion test results under non-irradiated conditions

40 μm

30 μm

A37

A44

A41

A47

A51

A56

A53

A60

A03

A07

A05

A11

50h

100h

Amount of corrosion/mg·cm -2

4 μm

0.4 μmTime/hFig. 11 Amount of corrosion over time under non-irradiated conditions
500h➢ The amount of corrosion increased with increasing test
Figure 10 Results of visual observation after corrosion test in non-irradiation
environment (typical example)

time, regardless of the liquid film thickness (Figure 11)➢ The amount of corrosion increased at 4 µm and 30 µm.
©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.1-3: Impact study on methods due to static environment inside the PCV (12/14)

No.127(ii) Status of studies related to corrosion evaluation of structures(a) Corrosion test
➢ Corrosion test results under irradiated conditions

4 μm

0.4 μm
A13

A20

30 μm
A17

40 μm
A22

0.2
kGy/h

A25

A31

A29

Amount of corrosion/mg·cm-2(500h)

A35

Irradiation dose rate /kGy·h-1

Figure 13 Estimated amount of corrosion in irradiation environment(Revised at 25°C)

3 kGy/h➢Figure 12 Results of visual observation after corrosion test in irradiation
environment (typical example)

500h

Comparing dose rates of 0.2 kGy/h and 3 Gy/h, theamount of corrosion at 3 kGy/h is approximately 1.2 to
2 times larger, verifying that corrosion accelerates as
the dose rate increases (Figure 13)©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.1-3: Impact study on methods due to static environment inside the PCV (13/14)

No.128(ii) Status of studies related to corrosion evaluation of structures(b) Corrosion evaluation of structures➢

Comparing the corrosion test results in a non-irradiation environment with previous findings 2), thevalues at 30 μm and 40 μm were lower than the conventional knowledge (Figure14)➢

30 to 40 μm is the thickness of the liquid film near the transition zone where the amount of corrosion

increases in the previous findings. Since the actual measurement of the liquid film thickness was
not verified in this test, it is consideredthat the results were not necessarily
match the previous findings2).
➢

On the other hand, several previous
findings have shown that the corrosion
rate accelerates under the condition
where a thin liquid film adheres, so

The results of this test (0kGy/h)

corrosion in a gas phase environment
with a liquid film adhesion is a subject thatshould be watched carefully.

Figure 14 Relationship between corrosion rate and liquid film thickness(this test result is over plotted)(a) Data from Hosoya et al. (b) Tomashov's model 2)(Source) 2) Hosoya et al., Zairyo-to-Kankyo (Materials and the Environment), 54, pp.391-395, 2005.

©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.1-3: Impact study on methods due to static environment inside the PCV (14/14)

No.129(ii) Status of studies related to corrosion evaluation of structures(b) Corrosion evaluation of structures➢

Regarding the irradiation effect in a gas phase environment with a liquid film adhesion, when the irradiation effect was
examined based on 0.2 kGy/h, it was found that the corrosion rate accelerated by approximately 1.2 to 2 times at 3 kGy/h(See Figure 13 above).
In the liquid phase, it was verified that there was almost no difference in corrosion rate between non-irradiated and 0.2
kGy/h, and a 1.5-fold increase in corrosion rate was observed between 0.2 kGy and 4.4 kGy/h (see Figure 1 above1)).

In the gas-liquid interface, it was verified that an approximately 1.6-fold increase in corrosion rate was observed

between the non-irradiation and 2.11 kGy/h. (see Fig. 3 above7)).
➢

The acceleration magnification by irradiation verified in this test was comparable to the previous findings.

Based on the results of the investigation of previous findings and the results of the corrosion test, it is expected that the corrosion ratein actual PCV will be significant at areas of thin liquid film adhesion in the gas-phase section and at the gas-liquid interface. Therefore,
when verifying the state of corrosion of structures, it is desirable to extract monitoring items focusing on corrosion in these areas.

(Source) 1) Nakano et al., Corrosion of carbon steel and low-alloy steel in diluted seawater containing hydrazine under gamma-rays irradiation, Journal of Japanese Papers of Japan Atomic Energy Agency(In Japanese), 13, 1, pp.1-6, 2014.
7) Abe et al., “Corrosion Rate and Long-term Prediction of Carbon Steel at Water Line under Gamma Ray Irradiation,” 67th Symposium on Materials and the Environment 2020, A-309, 2020.

©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-1: Quick reference table of important monitoring items (1/12)

No.130■ Extraction methods from the risk assessment table
Important monitoring items

Analysis
numberItem 1

Item 2Item 3Item 4Item 5-1

Item 5-2

Item 6-1

Item 6-2

Item 6-3

Targetequipment

The functionthat the target
is responsibleforWork delay
factor (= error)

Direct causes of error

Indirectcauses oferror

Reasons to be
selected

Detection requirements toavoid work delays

Directmonitoring/Indirect
monitoring

Reason for selection of detection
requirements

Reduction of
dust
concentration

Acceleration ofdeterioration of
dust
concentration
reductionfunction inside
the PCVThe effective flow patharea of the HEPA filter isreduced and the filter
performance cannot be
maintained(a) HEPA filter differential
pressureDirect (item 4)Same as above

Same as above(b) Dust amount andparticle size distribution at
the HEPA filter inlet

Indirect (item 5)

HEPA filter

An-Ki-1

Same asabove

Same asabove①■ Safety equipment (gas phase confinement equipment)This number islinked to Appendix
6.2.4.3-2

Partial blockage ofthe filter element
due to accumulationof dust migratingfrom the processing
point to the HEPA
filter

Selected because accumulationof dust in the HEPA filter
increases differential pressure,and this tendency is affected by
the amount and particle size
distribution of the dust flowing in.

Extracted from Item 6 (Detection
requirements) and replace names andimportant monitoring items

Table. Important monitoring items for gas phase confinement equipment in “Model ID Sa-4: Processing of debris” (1/2)

Important monitoring items
Analysis number
An-Ki-1, 4, 6, 8, 31, 33, 48, 51, 53, 55 HEPA filter differential pressure
Amount and particle size distribution of dust at HEPA filter inlet
An-Ki-1,28,48
Dust concentration ratio on upstream/downstream sides of HEPA filter
An-Ki-2,3,29,30,49,50,
Amount and chemical properties of dust at HEPA filter inlet (pH, chloride ion concentration,
An-Ki-2,29,49
chemical composition)
Amount and nuclide composition of dust at HEPA filter inlet
An-Ki-3,10,30,50
An-Ki-4,6,31,33,51,53
Amount of mist at HEPA filter inlet
Relative humidity at HEPA filter inlet
An-Ki-5,7,9,32,34,52,54,56
Amount of mist sprayed at processing point
An-Ki-5,7,32,34
Amount and particle size distribution of abrasives at HEPA filter inlet
An-Ki-8,55
Amount of heat input at processing point
An-Ki-9,13,37,56,60©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-1: Quick reference table of important monitoring items (2/12)■ Safety equipment (gas phase confinement equipment)This number islinked to Appendix
6.2.4.3-2

No.131

Table. Important monitoring items for gas phase confinement equipment in “Model ID Sa-4: Processing of debris” (2/2)

Important monitoring items
Temperature differential before and after the electric heater
Amount of mist at electric heater inlet
Differential pressure between inside and outside of the PCV
An-Ki-14,15
Amount and chemical properties (pH, chloride ion concentration) of mist flying to the PCV wall near the
D/W water surface
An-Ki-16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27 Differential pressure between inside and outside of the PCV + pressure inside the system
Amount and chemical properties of dust (pH, chloride ion concentration, chemical composition) at filter
An-Ki-16casing inlet
Amount and nuclide composition of dust at filter casing inlet
An-Ki-17
Amount of mist at filter casing inlet
An-Ki-18,19
Amount and chemical properties of dust (pH, chloride ion concentration, chemical composition) at
An-Ki-20, 24
exhaust line inlet
Amount and nuclide composition of dust at exhaust line inlet
An-Ki-21,25
Amount of mist at exhaust line inlet
An-Ki-22,23,26,27
HEPA filter differential pressure + differential pressure between inside and outside of the PCV
An-Ki-28
Airflow rate of exhauster
An-Ki-35,36,37
Amount and chemical properties of dust (pH, chloride ion concentration, chemical composition) at
An-Ki-35
exhauster inlet
Amount and nuclide composition of dust at exhauster inlet
An-Ki-36
Demister differential pressure + differential pressure between inside and outside of the PCV
An-Ki-38,39,40,41,42
Amount and particle size distribution of dust at demister inlet
An-Ki-38
Amount and chemical properties of dust (pH, chloride ion concentration, chemical composition) at
An-Ki-39
demister inlet
Amount and nuclide composition of dust at demister inlet
An-Ki-40
Amount of mist at demister inlet
An-Ki-41,42
Differential pressure of dry backwash filter + differential pressure between inside and outside of PCV
An-Ki-43,44,45,46,47
Amount and particle size distribution of dust at dry backwash filter inlet
An-Ki-43
Amount and chemical properties of dust (pH, chloride ion concentration, chemical composition) at dry
An-Ki-44
backwash filter inlet
Amount and nuclide composition of dust at dry backwash filter inlet
An-Ki-45
Amount of mist at dry backwash filter inlet
An-Ki-46,47
Amount of processing aid (mist) sprayed at processing point
An-Ki-52
Amount of anti-dispersion agent (mist) sprayed at processing point
An-Ki-54
Amount and nuclide composition of dust at electric heater inlet
An-Ki-57
Analysis number
An-Ki-10,11,12,13,57,58,59,60
An-Ki-11,12,58,59©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-1: Quick reference table of important monitoring items (3/12)■ Safety equipment (liquid phase confinement equipment)This number islinked to Appendix
6.2.4.3-2

No.132

Table. Important monitoring items for liquid phase confinement equipment in “Model ID Sa-4: Processing of debris”
Important monitoring items

Analysis number

An-Eki-1.2.3.4.5.7
An-Eki-1
An-Eki-2,3
An-Eki-4,5,7
An-Eki-6,13
An-Eki-8,9,10,11,12,14
An-Eki-8
An-Eki-9,10
An-Eki-11,12,14
An-Eki-15

An-Eki-16,19
An-Eki-16
An-Eki-17,24,25
An-Eki-17
An-Eki-18, 20, 21
An-Eki-18, 20, 22
An-Eki-19
An-Eki-21,26
An-Eki-22
An-Eki-23,26
An-Eki-23,24
An-Eki-25

D/W stagnant water transfer pump flow rate
Chemical properties (pH, chloride ion concentration, chemical composition) of the transferring liquid flowing into the D/Wstagnant water transfer pumpAmount, particle size distribution, and particle density of dust in the transferring liquid flowing into the D/W stagnant watertransfer pumpAmount, particle size distribution, and particle density of abrasives in the transferring liquid flowing into the D/W stagnant
water transfer pump
Water temperature inside the PCV

Amount of heat input at processing point
PCV stagnant water discharge pump flow rate
Chemical properties (pH, chloride ion concentration, chemical composition) of the transferring liquid flowing into the PCV
stagnant water discharge pumpAmount, particle size distribution, and particle density of dust in the transferring liquid flowing into the PCV stagnant water
discharge pumpAmount, particle size distribution, and particle density of abrasives in the transferring liquid flowing into the PCV stagnant
water discharge pump
D/W water level
Chemical properties (pH, chloride ion concentration, chemical composition) of D/W wall in liquid phase
Flow rate in the system
Amount, particle size distribution, and particle density of dust in the transferring liquid flowing into the piping
Flow rate in the system + amount of leakage
Amount, particle size distribution, and particle density of dust in the transferring liquid flowing into the liquid system
Flow rate in the system + leak detection
Chemical properties (pH, chloride ion concentration, chemical composition) of the transferring liquid flowing into the liquid
systemAmount, particle size distribution, and particle density of abrasives in the transferring liquid flowing into the piping
Amount, particle size distribution, and particle density of abrasives in the transferring liquid flowing into the liquid system
PCV stagnant water buffer tank water level + leak detection
Flow rate in the system + differential pressure before and after D/W stagnant water coarse particle removal equipment
Amount, particle size distribution, and particle density of dust in the transferring liquid flowing into the D/W stagnant watercoarse particle removal equipment
Chemical properties (pH, chloride ion concentration, chemical composition) of the transferring liquid flowing into the D/Wstagnant water coarse particle removal equipment©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-1: Quick reference table of important monitoring items (4/12)■ Safety equipment (cooling equipment)Thisnumber is
linked toAppendix
6.2.4.3-2

No.133

Table. Important monitoring items for cooling equipment in “Model ID Sa-4: Processing of debris”
Analysis number
An-Rei-1,2,3,4

An-Rei-1
An-Rei-2
An-Rei-3
An-Rei-4
An-Rei-5,11
An-Rei-6,7
An-Rei-6
An-Rei-7
An-Rei-8,9,10,12
An-Rei-8
An-Rei-9

An-Rei-10
An-Rei-12
An-Rei-13
An-Rei-13,16,18
An-Rei-14,17
An-Rei-14
An-Rei-15,16,18,19,21,22
An-Rei-15
An-Rei-17
An-Rei-19,23
An-Rei-20, 23
An-Rei-20, 21
An-Rei-22

Important monitoring items
D/W stagnant water transfer pump flow rate
Chemical properties (pH, chloride ion concentration, chemical composition) of the transferring liquid flowing into the D/W stagnant watertransfer pump inlet
Amount, particle size distribution, and particle density of dust in the transferring liquid flowing into the D/W stagnant water transfer pumpinlet
Amount of abrasives in the transferring liquid flowing into the D/W stagnant water transfer pump inlet
Amount, particle size distribution, and particle density of abrasives in the coolant flowing into the D/W stagnant water transfer pump
Water temperature inside the PCV
Amount of heat input at processing point
Cooler inlet/outlet temperatures
Chemical properties (pH, chloride ion concentration, chemical composition) of the transferring liquid flowing into the cooler inlet
Amount of abrasives flowing into the cooler inlet
PCV stagnant water injection pump flow rate
Chemical properties (pH, chloride ion concentration, chemical composition) of the transferring liquid flowing into the PCV stagnant water
injection pump inlet
Amount, particle size distribution, and particle density of dust in the transferring liquid flowing into the PCV stagnant water injection pumpinlet
Amount, particle size distribution, and particle density of abrasives in the transferring liquid flowing into the PCV stagnant water injection
pump
Amount of abrasives in the transferring liquid flowing into the PCV stagnant water injection pumpAmount of water in the PCV stagnant water buffer tank + amount of leakage
Chemical properties (pH, chloride ion concentration, chemical composition) of the coolant flowing into the liquid system
Flow rate in the system
Amount, particle size distribution, and particle density of dust in the coolant flowing into the piping
Flow rate in the system + amount of leakage
Amount, particle size distribution, and particle density of dust in the coolant flowing into the liquid system
Amount, particle size distribution, and particle density of abrasives in the transferring liquid flowing into the piping
Amount, particle size distribution, and particle density of abrasives in the coolant flowing into the liquid system
Flow rate in the system + differential pressure before and after D/W stagnant water coarse particle removal equipment
Amount, particle size distribution, and particle density of dust in the coolant flowing into the D/W stagnant water coarse particle removal
equipment
Chemical properties (pH, chloride ion concentration, chemical composition) of the coolant flowing into the D/W stagnant water coarse
particle removal equipment©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-1: Quick reference table of important monitoring items (5/12)■ Safety equipment (liquid phase/sub-criticality maintenance equipment)This number islinked to Appendix
6.2.4.3-2

No.134

Table. Important monitoring items for liquid phase/sub-criticality maintenancemonitoring items
equipmentof debris”
Analysis
number in “Model ID Sa-4: Processing Important

An-Rin-1,2,3,4,5,6,7
An-Rin-1
An-Rin-2,4An-Rin-3
An-Rin-5
An-Rin-6,7

Amount and particle size distribution of dust downstream of the D/W stagnant water coarse particle removal
equipment
Amount of dust in the transferring liquid flowing into the D/W stagnant water coarse particle removal
equipment
Amount, particle size distribution, and particle density of dust in the transferring liquid flowing into the D/Wstagnant water coarse particle removal equipment
Chemical properties (pH, chloride ion concentration, chemical composition) of the transferring liquid flowing
into the D/W stagnant water coarse particle removal equipment
Amount of abrasives in the transferring liquid flowing into the D/W stagnant water coarse particle removal
equipment
Amount, particle size distribution, and particle density of abrasives in the transferring liquid flowing into theD/W stagnant water coarse particle removal equipment©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-1: Quick reference table of important monitoring items (6/12)

No.135■ Operational equipment
Table. Important monitoring items for operational equipment in “Model ID Sa-1: Verification of the overall situation inside the PCV, and operational/safety
equipment”
Important monitoring items
Analysis number--No important monitoring items due to the environment inside the PCVThis number islinked to Appendix
6.2.4.3-3

Table. Important monitoring items for operational equipment in “Model ID Sa-2: Approaching the object to be processed”
Analysis number
Saku-A-1
Saku-A-2
Saku-A-3
Saku-A-4
Saku-B-1
Saku-B-2
Saku-B-3
Saku-B-4
Saku-B-5
Saku-B-6
Saku-B-7

Important monitoring items
Presence of interfering objects unaffected by darkness
Presence of interfering objects unaffected by fog
Presence of interfering objects unaffected by dripping water
Presence of interfering objects unaffected by noiseTime to reach destination
Velocity of water flow on the transfer route
Degree of influence of equipment on hot spots (radiation resistance)
Location of hot spot on the transfer routeTransfer route detection unaffected by soaring sediment
Current location detection unaffected by darkness
Current location detection unaffected by fog
Current location detection unaffected by dripping water
Current location detection unaffected by noise©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-1: Quick reference table of important monitoring items (7/12)■ Operational equipment
This number islinked to Appendix
6.2.4.3-3

No.136

Table. Important monitoring items for operational equipment in “Model ID Sa-3:
Important monitoring items
worknumber
prior to debris processing”
Analysis
Saku-A-1
Saku-A-2
Saku-A-3
Saku-A-4
Saku-A-5

Saku-A-6
Saku-A-7
Saku-A-8
Saku-A-9

Submerged debris detection unaffected by darkness
Submerged debris detection unaffected by fog
Submerged debris detection unaffected by dripping water
Submerged debris detection unaffected by noise
Application time for neutron absorbent
Velocity of water flow at the neutron absorbent application area
Detection of neutron absorbent application status unaffected by darkness
Detection of neutron absorbent application status unaffected by fog
Detection of neutron absorbent application status unaffected by dripping water
Detection of neutron absorbent application status unaffected by blind spots due to surrounding structures©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-1: Quick reference table of important monitoring items (8/12)■ Operational equipment
This number islinked toAppendix
6.2.4.3-3

No.137

Table. Important monitoring items for operational equipment in “Model ID Sa-4:
Important monitoring items
Analysis
number of debris” (1/2)
Processing
Saku-B-1

Saku-A-1
Saku-A-2
Saku-A-3, 5
Saku-A-3
Saku-A-4

Saku-A-5
Saku-A-6
Saku-A-7
Saku-A-8
Saku-A-9
Saku-A-10
Saku-A-11

Saku-A-12
Saku-B-2
Saku-B-3

Fuel debris properties (compressive strength) in the processing area
Dust concentration at the processing site unaffected by darkness
Debris temperature unaffected by darkness
Dust concentration at the processing site unaffected by fog
Debris temperature unaffected by fog
Dust concentration at the processing site unaffected by dripping water
Debris temperature unaffected by dripping water
Dust concentration at the processing site unaffected by noise
Debris temperature unaffected by noise
Debris temperature unaffected by dust dispersion
Neutron flux unaffected by darkness
Debris dimensions unaffected by darkness
Neutron flux unaffected by fog
Debris dimensions unaffected by fog
Neutron flux unaffected by dripping water
Debris dimensions unaffected by dripping water
Neutron flux unaffected by dust dispersion
Debris dimensions unaffected by dust dispersion
Neutron flux unaffected by background (noise)
Debris dimensions unaffected by background
Neutron flux around the location of the fall
Structural strength of structure leading to fall mode
Dust concentration at the processing site
Amount of anti-dispersion agent (mist) reaching the processing area
Time to reach the processing area
Three-dimensional shape (dimensions) of structure at the processing site
Degree of wear and tear of processing jigs
Compressive strength of debris to be processed©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-1: Quick reference table of important monitoring items (9/12)■ Operational equipment
This number islinked toAppendix
6.2.4.3-3

No.138

Table. Important monitoring items for operational equipment in “Model ID Sa-4:
Important monitoring items
Processing
Analysis
number of debris” (2/2)
Saku-B-5, 10, 11, 12, 13, 14, 15

Degree of influence of equipment on hot spots (radiation resistance)
Source location of hot spots at the processing site
Amount of debris filling the inner container

Saku-B-5

Velocity and flow rate of cooling water in the debris processing area

Saku-B-6

Dimensions of processed debris unaffected by darkness

Saku-B-7

Dimensions of processed debris unaffected by fog

Saku-B-8

Saku-B-10

Dimensions of processed debris unaffected by dripping water
Dimensions of processed debris unaffected by sediments, powder from cutting (dust), or neutron
absorbers floating in water
Velocity and flow rate of cooling water in the debris collection area

Saku-B-11

Relative position of debris and inner container unaffected by darkness

Saku-B-12

Relative position of debris and inner container unaffected by fog

Saku-B-13

Saku-B-15

Relative position of debris and inner container unaffected by dripping water
Relative position of debris and inner container unaffected by sediments, powder from cutting (dust), or
neutron absorbers floating in water
Relative position of debris and inner container unaffected by noise

Saku-B-16

Amount of debris filling the inner container unaffected by darkness

Saku-B-17

Amount of debris filling the inner container unaffected by fog

Saku-B-18

Amount of debris filling the inner container unaffected by dripping water
Amount of debris filling the inner container unaffected by sediments, powder from cutting (dust), or
neutron absorbers floating in water
Amount of debris filling the inner container unaffected by noise

Saku-B-4

Saku-B-9

Saku-B-14

Saku-B-19

Saku-B-20©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-1: Quick reference table of important monitoring items (10/12)

No.139■ Operational equipment
Table. Important monitoring items for operational equipment in “Model ID Sa-5:
Variousrecords following processing work”Important monitoring items
Analysis number---This number islinked toAppendix
6.2.4.3-3

No important monitoring items due to the environment inside the PCVTable. Important monitoring items for operational equipment in “Model ID Sa-6: Cell
Important monitoring items
transferdebris (PCV → Cell R)”
Analysisof
number
Saku-A-1

Presence of interfering objects unaffected by darkness

Saku-A-2

Presence of interfering objects unaffected by fog

Saku-A-3

Presence of interfering objects unaffected by dripping water

Saku-A-4

Presence of interfering objects unaffected by noise

Saku-B-1
Saku-B-2

Time to reach destination
Velocity of water flow on the transfer route

Degree of influence of equipment on hot spots (radiation resistance)
Location of hot spot on the transfer route

Saku-B-3

Transfer route detection unaffected by soaring sediment

Saku-B-4

Current location of the inner container unaffected by inner container radiation

Saku-B-5

Transfer route detection unaffected by dust

Saku-B-6

Current location of the inner container unaffected by noise©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-1 : Quick reference table of important monitoring items (11/12)

No.140■ Operational equipment
This number
is linked toAppendix
6.2.4.3-3

Table. Important monitoring items for operational equipment in “Model ID Sa-7: Transfer of debris ① (Cell R → Cell Y)”
Saku-B-1

Detection of transfer line interference unaffected by the inner container radiation

Saku-B-2

Detection of transfer line interference unaffected by dust

Saku-A-1
Saku-A-2
Saku-B-3

This number
is linked toAppendix
6.2.4.3-3

Important monitoring items

Analysis number

Dust concentration at cell (Y)Dust concentration at cell (R)Hydrogen concentration/or oxygen concentration in cell (Y)Amount of hydrogen generated in the inner container
Air dose rate of cell (Y)Surface dose rate of inner container

Saku-B-4

Transfer route detection unaffected by soaring dust

Saku-B-5

Current location of the inner container unaffected by soaring dust

Table. Important monitoring items for operational equipment in “Model ID Sa-8: Collection of debris”
Important monitoring items

Analysis number
Saku-B-1
Saku-B-2
Saku-B-3
Saku-B-4

Time to verify whether the contents are protruding from the inner container or not
Presence or absence of contents protruding from the inner container
Time to verify whether the inner container is damaged or not
Presence or absence of damage to the inner container
Time to remove foreign matter (debris powder) from the canister

Amount of foreign matter (debris powder) adhering to the canister
Time to complete the inner container collection
Surface dose rate of inner container©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-1: Quick reference table of important monitoring items (12/12)■ Operational equipment
This number
is linked toAppendix
6.2.4.3-3

No.141

Table. Important monitoring items for operational equipment in “Model ID Sa-9: Transfer of debris ② (Cell Y → Cell G)”
Important monitoring items

Analysis number
Saku-A-1

Dust concentration at cell (G)Dust concentration at cell (Y)Saku-A-2

Flow rate in the system

Saku-A-2,3

Amount, particle size distribution, and particle density of dust in the transferring liquid flowing into the piping

Saku-A-3

Flow rate in the system + amount of leakage

Saku-B-1

Decontamination completion time of transfer container
Inspection items not affected by contaminated water (surface dose rate, pressure discharge characteristics,
surface contamination concentration)

Table. Important monitoring items for operational equipment in “Model ID Sa-10: Transfer of debris (Cell G → Secondary boundary)”
Analysis number---

Important monitoring items
No important monitoring items due to the environment inside the PCV©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-2: Risk assessment table for safety equipment (Detailed version) (1/48)
No.142■ Supplementary information before presentation of evaluation results: Classification ofindirect factors affecting safety functions (1/2)

In conducting the risk assessment, although it is assumed the disturbances (dust/mist generation, fueldebris properties) generated as a result of the fuel debris retrieval operations would degrade thecomponents that constitute safety functions, the characteristics of the disturbances were taken into
consideration and the effects on the components were categorized into the following four categories andextracted as important monitoring items for indirect monitoring.
① Factors in which disturbances directly affect safety functions• Dust and mist generated at the processing point directly accumulate and adhere to the components,
causing adverse effects.
✓ Components are adversely affected due to accumulation of dust (examples of indirect monitoring
items: amount and particle size distribution of dust flowing into components)✓ Components are adversely affected due to accumulation of mist (examples of indirect monitoring
items: amount of mist flowing into components)② Factors in which disturbances indirectly affect safety functions• Dust and other particles generated at the processing point flow into the components, causing adverse
effects due to chemical, radiological changes, and other changes to the parts of the components.
✓ Components are adversely affected as a result of changes in chemical properties (examples ofindirect monitoring items: amount and chemical composition of dust flowing into components)✓ Components are adversely affected as a result of degradation due to irradiation (examples ofindirect monitoring items: amount and nuclide composition of dust flowing into components)©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-2: Risk assessment table for safety equipment (Detailed Version) (2/48)
No.143■ Supplementary information before presentation of evaluation results: Classificationof indirect factors affecting safety functions (2/2)③ Factors in which disturbances affect the design conditions of equipment that
constitute safety system• Disturbances generated at the processing point adversely affect the equipment by affecting
the design conditions of the equipment that constitute safety functions.
✓ Equipment is adversely affected when worsening design conditions (examples ofindirect monitoring items: design conditions of equipment (pressure inside the PCV,
temperature, relative humidity, composition of gas)
④ Others• Not applicable to the above categories, but equipment is adversely affected by equipmentspecific failure modes while retrieving fuel debris.

Based on the characteristics of the disturbances (dust/mist generation, fueldebris properties), four factors are considered to be degradation modes of theequipment.
©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-2: Risk assessment table for safety equipment (Detailed version) (3/48)
No.144■ Procedure for entering the information on disturbances into the risk assessment table (1/2)- For the Table of environmental changes inside the PCV due to operational equipment activities, thedisturbances entered in item 5 of the risk assessment table were classified into disturbances (① to ③) asshown in the table below.
Fueldebristype

Mass offueldebrisAssumed properties
Compressive
DensityPrimary
strengthcomponent
3[g/cm ]
[MPa]

11

Craft, on
bedrock(uppersection):2000
Other thanabove
mentioned:
230

Particle size of dust
Aerial processing
Processing Equipment
Underwater processing
Localized area
Remarks(no anti-dispersion agent)
mode
name
--[μm]--[μm]All in range of peak
particle size
Blade
[U Rich]
2 to 3 (massdiameter:(U, Zr)O2-C,
concentration
Airborne
Airborne
Unknown
200 mm(Zr, U)O2-T,
Pedestal inside
distribution)
the PCV
0.1 to 0.3 (number
Cutting
Blade[Fe Rich](Floor/Interior/concentration
Disc cutter thickness:
UO2, Fe, Zry-2, outside) drywell
distribution)
1 mm
α-Zr(O),All in median diameter
SUS/Fe, Fe2(Zr,
0.3 (number distribution)
Sedimentation Above 50
Number of Sedimentation 7.9 (sedimentU),
revolutions:
ZrB2, Fe2B,
distribution)
1000 rpm
Zr(O), Fe2Zr
Peripheral
EitherFloating in
50 or lessdispersion
airborne/sedimentation water

Total amount of dust
generated
AerialUnderwater
processing processing[g]1242.1Disturbance ①[g]Assumed processing methods

Mass balance and amount of dust migration
Aerial processing
Underwater processing
Amount of processing aid
Amount ofAmount of
injected
Mass balance
Mass balance
dust migration
dust migration
Input
Total amount
--[%]
[g]
--[%]
[g]
materials
of input

Airborne4

49.7

Airborne

2E-05

0.0

Sedimentation

37

459.6

Sedimentation

99.5

1235.9Peripheral
dispersion

59

732.9

Floating in
water

0.5

6.2

1242

[Aerialprocessing]Water: 1
L/min

198

L

↑
(*)

Disturbance ②

Amount of anti-scattering
agent injected(Only for aerial processing)Input
materials

Mist: 0.05
L/min

Total amount of
input

9.9

L

↑
(*)

Disturbance ③©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-2: Risk assessment table for safety equipment (Detailed version) (4/48)
No.145■ Procedure for entering the information on disturbances into the risk assessment table (2/2)
No.

②DisturbanceParticle size and amount of dispersion of dust
generated during processing
Use of processing aid injected onto processing jigs③

Use of anti-dispersion agent for dust①

① to ④ on theprevious page

Others④

Important monitoring
items extracted- Heat input during processing- Abrasive input during processing
Important monitoring items

Item 1

Item 2Item 3Item 4Item 5-1

Item 5-2

Item 6-1

Item 6-2

Item 6-3

Targetequipment

The functionthat thetarget is
responsibleforWork delay factor(= error)

Direct causes of error

Indirectcausesof error

Reasons to be selected

Detection requirements to avoid work
delaysDirectmonitoring/Indire
ct monitoring

Reason for selection of detection
requirements

Reduction of

Increased dust

increases because the HEPA filter

dust

concentration inside

deteriorates and the design value ofPartial blockage of the filter(a) HEPA filter differential pressure

Direct (item 4)concentration

the PCVthe exhaust filter efficiency is notelement due toAnalysis
numberDust concentration inside the PCVHEPA filter

ensured.

An-Ki-1

Same asSame as

above

above

PCV
(Primary
Boundary)Same as above

Decrease in

Staticdifferential pressure

boundary

between inside andoutside of the PCV

An-Ki-14

Same asSame as

above

above

①

dust in the HEPA filter increases

accumulation of dust

differential pressure, and this tendency

migrating from thePredict loss of safetyfunctions due to debrisSame as above
retrieval operations byextracting (a) direct/(b)indirect monitoringprocessing point to the
HEPA filter

is affected by the amount and particle(b) Dust amount and particle size
distribution at the HEPA filter inlet

Indirect (item 5)

As the PCV deteriorates and the size(a) Differential pressure between

occurs and decreases the differential

Partial damage caused bypressure between inside and outside②

of the PCV.

size distribution of the dust flowing in.

Selected because increase in the sizeof the opening increases, inleakage

surface due to accumulation

Same as aboveOrganize the causal

relationship between the
direct cause of the error
and disturbance during
debris retrieval operations

inside and outside of the PCVof the opening caused by the corrosion
Direct (item 4)corrosion of PCV wallof processing aid (mist)
Same as above

Selected because accumulation ofof the PCV wall surface decreases thedifferential pressure between insideand outside of the PCV, and because(b) Amount and chemical properties(pH, chloride ion concentration) of
mist flying to PCV wall surface near
D/W water surface

this trend is affected by the liquid
Indirect (item 5)phase chemical properties on the PCV
wall surface.

Loss of safety function is defined as a factor of throughput reduction (Item 3). Factors affecting the components that constitute safety functions
due to disturbances as a result of fuel debris retrieval operations are analyzed, and detection requirements for avoiding work delays are organized©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-2: Risk assessment table for safety equipment (Detailed version) (5/48)
No.146■ Risk assessment table■ Score table for item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still underdevelopment[2 points] Countermeasures exist, but there are no trackrecords of application at the Fukushima Daiichi[1 point] Countermeasures exist, and have been applied at
the Fukushima Daiichi.

(gas phase confinement equipment)
Model ID
Process

Ko-3: Debris retrieval

Work

Sa-4

: Processing of debris■ Score table for item 7-2[4 points] Requires constant monitoring during task andpredictability is poor
[3 points] Requires constant monitoring during task but
predictability is good
[2 points] Requires regular monitoring and predictability ispoor[1 point] Requires regular monitoring and predictability is
good

Important monitoring items
Item 1Analysis
numberItem 2Item 3Item 4

Targetequipment

The functionthat thetarget is
responsibleforWork delay factor(= error)

Directcauses oferror

HEPA filter

Reduction of

Increased dust

Dust

dust

concentration

concentrati

concentration

inside the PCV

on inside

An-Ki-1

Item 5-1

Item 5-2■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is unknown[3 points] Countermeasures exist, but throughput decreases significantly due tosuspension of task
[2 points] Countermeasures exist, but throughput decreases due to workload
limitations[1 point] No impact on throughput, or when 7-1 is 1 point

Weighted evaluation of important monitoring items
Item 6-1

Item 6-2

Item 6-3

Item 7-1

Item 7-2

Item 7-3

Item 7-4(Evaluation Results)

Impact on
throughput due
to errorhandling(Indirect
causes)Individual

Detectionrequirements toavoid work delays

Directmonitoring/
Indirect
monitoring

Partial blockage of(a) HEPA filter

DirectSelected because accumulation

Functionality is ensured byFilter clogging is due to

Because itemthe filter element

differential pressure(item 4)of dust in the HEPA filter

switching filters through 2

daily accumulation, so

7-1 is 1 pointdue to accumulation

increases differential pressure,series of filters (alreadypredictability is good

the PCVof dust migrating

and this tendency is affected byincreasesfrom the processing

the amount and particle sizeas thepoint to the HEPA

distribution of the dust flowing

HEPA filter

filterdeteriorate

Indirectcauses oferror

Reasons to be
selected

Reason for selection of
detection requirements

Point

1

Presence or absence ofcountermeasures for disturbing
functionsstudied)

Point

Effects on accurate andprompt on-site response byworkers

1

Point

1

Point ofrepresent
ation

1

in.

①

3

s and theHEPA filter(b) Dust amountIndirect

Functionality is ensured byContinuous monitoring is

Because itemand particle size

(item 5)switching filters through 2

required, but predictability

7-1 is 1 point

series of filters (alreadyis good.

distribution at theefficiency

HEPA filter inlet

does not1

studied)3

13

meet thedesignvalue.

Same asSame as

above

above

Same as above

Partial damage(a) HEPA filter

DirectDeterioration of filter elements

Functionality is ensured by

Post-detection is possible

Because item

caused by the

upstream/downstre(item 4)due to accumulation of dust in

switching filters through 2

by constant monitoring of

7-1 is 1 point

Same asdeterioration of filter

am dustthe HEPA filter causes partial

series of filters (alreadythe dust concentration on

above

elements due toconcentration ratio

damage to filter elements anddust migrating fromthe processing point
An-Ki-2

Same asabove

to the HEPA filter

1

studied)4

decreases the ratio of dust

the downstream side of the1

4

filter, but predictability isconcentration between thepoor(b) Amount andIndirect

upstream and downstream

Functionality is ensured byContinuous monitoring is

Because item

chemical properties(item 5)sides. Selected because thisswitching filters through 2

required, but predictability

7-1 is 1 point(pH, chloride ion

trend is affected by the amountconcentration,and chemical properties (pH,chemicalchloride ion concentration,

composition) of dust

chemical composition) of dust

at HEPA filter inlet

flowing into the filter.

series of filters (already1

studied)4is poor.
4

1

4[The numbering rules for analysis ID]
Gas phase equipment: An-Ki-Arabic numerals Liquid phase equipment: An-Eki-Arabic numerals
Cooling equipment: An-Rei-Arabic numerals Liquid phase sub-criticality maintenance equipment: An-Rin-Arabic
numerals©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-2: Risk assessment table for safety equipment (Detailed version) (6/48)
No.147■ Risk assessment table(gas phase confinement equipment)
Model ID
Process

Ko-3: Debris retrieval

Work

Sa-4

: Processing of debris■ Score table for item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still underdevelopment[2 points] Countermeasures exist, but there are no trackrecords of application at the Fukushima Daiichi[1 point] Countermeasures exist, and have been appliedat the Fukushima Daiichi.

■ Score table for item 7-2[4 points] Requires constant monitoring during task andpredictability is poor
[3 points] Requires constant monitoring during task but
predictability is good
[2 points] Requires regular monitoring and predictability
is poor[1 point] Requires regular monitoring and predictability
is good

Important monitoring items■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is
unknown[3 points] Countermeasures exist, but throughput decreases
significantly due to suspension of task
[2 points] Countermeasures exist, but throughput decreases due
to workload limitations[1 point] No impact on throughput, or when 7-1 is 1 point

Weighted evaluation of important monitoring items

Item 1

Item 2Item 3Item 4Item 5-1

Item 5-2

Item 6-1

Item 6-2

Item 6-3

Targetequipment

The function thatthe target is
responsible forWork delay
factor(= error)

Direct causes of
error

Indirectcausesof error

Reasons tobe selected

Detectionrequirements toavoid work delays

Directmonitoring/Ind
irect
monitoring

Reason for selection of
detection requirements

Reduction of

Increased

Dust

Partial(a) HEPA filter

Direct (itemPartial damage to filter

Functionality is

Post-detection is

Because

dust

dust

concentration

damage to

upstream/downs

4)elements due toensured by switchingpossible by constant

item 7-1 isconcentration

concentrat

inside the PCV

filtertream dust

irradiation of dust

filters through 2 series

monitoring of the dust

1 point

ion insideincreases as

elements

concentration

accumulated in theof filters (alreadyconcentration on thethe PCVthe HEPA filter

due toratio

HEPA filter decreases

studied)downstream side of

deteriorates

irradiation of

the ratio of dust

and the HEPA

dust

concentration between

filter efficiency

migratingthe upstream andfrom thedownstream sides.

processing

Selected because thispoint to thetrend is affected by the

HEPA filter

amount and nuclide

Analysis
numberHEPA filter

does not meet
An-Ki-3

the design①

value.

Item 7-1

Point

Presence or absence ofcountermeasures for
disturbing functions

Item 7-2

Point

Effects on accurate andprompt on-site response
by workers

Item 7-3

Point

Impact on
throughput
due to error
handling(Indirect
causes)Item 7-4(Evaluation Results)

Individual

Point ofrepresentation

the filter, but
1

4

predictability is poor

1

4

4

composition of inflowing
dust.
(b) Amount andIndirect (itemFunctionality is

Continuous monitoring

nuclide5)

ensured by switchingis required, but

composition of1

dust at HEPA

above

An-Ki-4

Same as above

Same asabove

Same as above②

4

predictability is poor.

item 7-1 is1

1 point

studied)Partial(a) HEPA filter

Direct (itemSelected because theFunctionality is

Filter clogging is due

Becauseblockage ofdifferential

4)

differential pressure

ensured by installing a

to daily accumulation,item 7-1 isfilterpressure

increases due to partial

demister and electricso predictability is1elements

blockage caused by mist

due tothat accumulates in thestage filter (alreadyadhesion of

HEPA filter, andheater at the first-

studied)

1

good

1

1 point

processing(b) Amount of

Indirect (itembecause this trend is

Functionality is

Continuous monitoring

Becauseaid migrating

mist at HEPA

5)affected by the amountensured by installing a

is required, butitem 7-1 isfrom thefilter inlet

of inflowing mist due todemister and electricpredictability is good.

processing

4of filters (alreadyfilter inlet

Same asfilters through 2 series

Becausethe processing aid.

1

heater at the first-

point to thestage filter (already

HEPA filter

studied)3

1

3

1 point
1

3©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-2: Risk assessment table for safety equipment (Detailed version) (7/48)
No.148■ Risk assessment table(gas phase confinement equipment)
Model ID
Process

Ko-3: Debris retrieval

Work

Sa-4

: Processing of debris■ Score table for item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still underdevelopment[2 points] Countermeasures exist, but there are no trackrecords of application at the Fukushima Daiichi[1 point] Countermeasures exist, and have been applied at the
Fukushima Daiichi.

■ Score table for item 7-2[4 points] Requires constant monitoring during task andpredictability is poor
[3 points] Requires constant monitoring during task but
predictability is good
[2 points] Requires regular monitoring and predictability
is poor[1 point] Requires regular monitoring and predictability is
good

Important monitoring items■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is
unknown[3 points] Countermeasures exist, but throughput decreases
significantly due to suspension of task
[2 points] Countermeasures exist, but throughput decreases due
to workload limitations[1 point] No impact on throughput, or when 7-1 is 1 point

Weighted evaluation of important monitoring items

Item 1

Item 2Item 3Item 4Item 5-1

Item 5-2

Item 6-1

Item 6-2

Item 6-3

Targetequipment

The functionthat the target
is responsibleforWork delay factor(= error)

Direct causesof error

Indirectcauses oferror

Reasons to be
selected

Detectionrequirements toavoid work delays

Directmonitoring/I
ndirectmonitoring

Reason for selection of
detection requirements

HEPA filter

Reduction of

Increased dust

Dust

Performance(a) Relative humidity

Direct (itemSelected because theFunctionality is ensured by

Post-detection is possible

Because item 7-1 isdust

concentration

concentration

degradation of theat HEPA filter inlet

4)

relative humidity of gas

installing a demister and an

by constant monitoring of

1 point

concentration

inside the PCV

inside the PCVHEPA filter caused

flowing into the HEPA

electric heater at the first-

the temperature differential

increases as

by relative humidity

filter was verified to

the HEPA filter

at HEPA filter inlet,

deviate from the design

deteriorates

which is a design

condition, and because

condition, exceeding

this trend is affected by

the design

the amount ofdoes not meetassumption, as aprocessing aid (mist)

the design

result of debris(b) Amount of mist

Indirectsprayed at the

Functionality is ensured byContinuous monitoring isvalue.

retrieval operations

sprayed at(item 5)processing point.

installing a demister and an

required, but predictability

Analysis
numberand the HEPA
An-Ki-5

filter efficiency②

processing point

Item 7-1

Point

Presence or absence ofcountermeasures for
disturbing functions

Item 7-2

Pointstage filter1(already studied)

Effects on accurate andprompt on-site response byworkers

Item 7-3

Point

Impact on
throughput due toerror handling(Indirect causes)

Item 7-4(Evaluation Results)

Individual

Point ofrepresentation

before and after the electric4heater, but predictability is

1

4

poor
4

1

electric heater at the first-

3

is good.

Because item 7-1 is
1 point
13stage filter(already studied)

Same asSame as

above

above

Same as above

Same asabove

Partial blockage due(a) HEPA filter

Direct (itemSelected because theFunctionality is ensured byFilter clogging is due toto adhesion of anti-

differential pressure

4)

mist accumulated in the

installing a demister and an

daily accumulation, so

dispersion agent

HEPA filter increases

migrating from thethe differential pressure

stage filter

processing point to③

An-Ki-6

the HEPA filter

An-Ki-7

Same as

above

above

Same as above

electric heater at the first-

1

predictability is good

1 point
1

1

for the HEPA filter, and(already studied)(b) Amount of mist at

Indirectbecause this trend is

Functionality is ensured byContinuous monitoring is

Because item 7-1 is

HEPA filter inlet(item 5)affected by the amountinstalling a demister and an

required, but predictability

1 pointof mist flowing into filter

Same as1

Because item 7-1 is

1electric heater at the first-

elements due to the anti-

stage filter

3

is good.

dispersion agent.

(already studied)

Performance(a) Relative humidity

Selected because theFunctionality is ensured by

Post-detection is possible

degradation of theat HEPA filter inlet

relative humidity of gas

installing a demister and an

by constant monitoring ofSame asHEPA filter caused

Direct (itemflowing into the HEPA

above

by relative humidity

4)

filter was verified to1electric heater at the firststage filter

4

before and after the electric3

Because item 7-1 is

1 point1

4

at HEPA filter inlet,

deviate from the design

Same aswhich is a design

condition of the HEPA

above

condition, exceeding(b) Amount of mist

filter, and because thisFunctionality is ensured byContinuous monitoring is

Because item 7-1 isthe design

sprayed attrend is affected by the

installing a demister and an

required, but predictability

1 point

assumption, as aprocessing point

result of debris
retrieval operations(already studied)

the temperature differential

1

3

heater, but predictability ispoorelectric heater at the first-

Indirectamount of anti-(item 5)dispersion agent

stage filter(mist) sprayed at the(already studied)1

4

is good.

3

1

3

processing point.

©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-2: Risk assessment table for safety equipment (Detailed version) (8/48)
No.149■ Risk assessment table(gas phase confinement equipment)
Model ID
Process

Ko-3: Debris retrieval

Work

Sa-4

: Processing of debris■ Score table for item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still underdevelopment[2 points] Countermeasures exist, but there are no trackrecords of application at the Fukushima Daiichi[1 point] Countermeasures exist, and have been applied at
the Fukushima Daiichi.

■ Score table for item 7-2[4 points] Requires constant monitoring during task andpredictability is poor
[3 points] Requires constant monitoring during task but
predictability is good
[2 points] Requires regular monitoring and predictability
is poor[1 point] Requires regular monitoring and predictability
is good

Important monitoring items■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is unknown[3 points] Countermeasures exist, but throughput decreases
significantly due to suspension of task
[2 points] Countermeasures exist, but throughput decreases due toworkload limitations[1 point] No impact on throughput, or when 7-1 is 1 point

Weighted evaluation of important monitoring items

Item 1

Item 2Item 3Item 4Item 5-1

Item 5-2

Item 6-1

Item 6-2

Item 6-3

Targetequipment

The functionthat thetarget is
responsibleforWork delay
factor (=error)

Direct causes of
error

Indirectcauses oferror

Reasons to be
selected

Detectionrequirements toavoid work delays

Directmonitoring/
Indirect
monitoring

Reason for selection of
detection requirements

HEPA filter

Reduction of

Increased

Dust concentration

Partial blockage of(a) HEPA filter

Accumulation of abrasives

Functionality is ensured byFilter clogging is due to daily

dust

dust

inside the PCV

filter elements due

differential pressure

flowing into the HEPA filter

switching filters through 2

accumulation, so predictability

concentration

concentration

increases as theto accumulation of

Analysis
numberinside the

HEPA filter

abrasives migrating

PCV

deteriorates andfrom the processing

the HEPA filter

An-Ki-8④

Directpartially clogs the HEPA filter(item 4)and increases the HEPA filter

Item 7-1

Point

Presence or absence ofcountermeasures for disturbing
functions

Item 7-2

Point

series of filters (already1

studied)Effects on accurate and prompt
on-site response by workers

Item 7-3

Point

Impact on throughput
due to error handling(Indirect causes)

Item 7-4(Evaluation
Results)
Point
of
Indiv
represidual
entation

Because item 7-1 is 1
point

is good111differential pressure. Selected

point to the filter

because this trend is affected by

efficiency does not(b) Amount andmeet the design

particle sizevalue.

distribution ofabrasives at HEPA

3

the amount of abrasives flowing

Functionality is ensured byinto the HEPA filter due toIndirect

processing.

(item 5)

Continuous monitoring isswitching filters through 2
1

series of filters (alreadyBecause item 7-1 is 1

required, but predictability is
3

good.

point
1

3

studied)filter inlet

Same asSame asSame as

above

above

above

Same as above

Performance(a) Relative

Selected because the relative

Functionality is ensured by

Post-detection is possible bydegradation of thehumidity at HEPA

humidity at the HEPA filter inlet

installing a demister and an

constant monitoring of the

HEPA filter caused

filter inlet

by the design

Directwas verified to deviate from the(item 4)design condition, and because

condition of relative
humidity at theAn-Ki-91electric heater at the first-stage
filterthis trend is affected by the(already studied) → 2 series

amount of heat input at the

only

processing point.

4

temperature differential before
and after the electric heater, but

Because item 7-1 is 1
point
1

4

predictability is poor

Same asHEPA filter inlet(b) Amount of heat

Functionality is ensured byContinuous monitoring is

Because item 7-1 is 1

above

exceeding the

input at processing

installing a demister and an

required, but predictability ispointassumed design

point

electric heater at the first-stage

good.

condition with

Indirect

evaporation of D/W(item 5)

4

filter1(already studied) → 2 series

3

1

3

only

stagnant water as aresult of heat input
during processing
Electric

Reduction of

Increased

The dust

Performance(a) Temperature

Selected because theFunctionality is ensured by

Post-detection is possible by

Because item 7-1 is 1

heaterdust

dust

concentration

degradation of thedifferential before

temperature differential before

switching between heaters

constant monitoring of thepoint(Pretreatment

concentration

concentration

inside the PCV

electric heaterand after theand after the electric heaterusing 2 series of electric

temperature differential before

inside theincreases because

caused byelectric heater

PCV

the electric heater

irradiation of dust

equipment)

deteriorates andAn-Ki-10

the design value ofthe filter is not
ensured.

①

Directdecreases due to performance(item 4)degradation of the electricmigrating from theheater, and because this trend

processing point tois affected by the amount andthe electric heater

nuclide composition of inflowing(b) Amount and

1

dust.

filter inlet

Indirect(item 5)4

and after the electric heater, but
predictability is poor.

1

4

4

nuclide compositionof dust at HEPA

heaters (already studied)1

Functionality is ensured byContinuous monitoring isswitching between heaters

required, but predictability isusing 2 series of electric

4

poor.

Because item 7-1 is 1
point
1

4

heaters (already studied)©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-2: Risk assessment table for safety equipment (Detailed version) (9/48)
No.150■ Risk assessment table(gas phase confinement equipment)
Model ID
Process

Ko-3: Debris retrieval

Work

Sa-4

: Processing of debris■ Score table for item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still underdevelopment[2 points] Countermeasures exist, but there are no trackrecords of application at the Fukushima Daiichi[1 point] Countermeasures exist, and have been appliedat the Fukushima Daiichi.

■ Score table for item 7-2[4 points] Requires constant monitoring during task andpredictability is poor
[3 points] Requires constant monitoring during task but
predictability is good
[2 points] Requires regular monitoring and predictability
is poor[1 point] Requires regular monitoring and predictability is
good

Important monitoring items■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is unknown[3 points] Countermeasures exist, but throughput decreases significantly due
to suspension of task
[2 points] Countermeasures exist, but throughput decreases due to workload
limitations[1 point] No impact on throughput, or when 7-1 is 1 point

Weighted evaluation of important monitoring items

Item 1

Item 2Item 3Item 4Item 5-1

Item 5-2

Item 6-1

Item 6-2

Item 6-3

Item 7-1

Item 7-2

Targetequipment

The functionthat the target
is responsibleforWork delay factor(= error)

Direct causes of
error

Indirectcauses oferror

Reasons to be
selected

Detectionrequirements to avoid
work delays

Directmonitoring/Indirect
monitoring

Reason for selection of
detection requirements

Electric

Reduction of

Increased dust

The dust

Performance(a) Temperature

DirectSelected because theFunctionality is ensured by

Post-detection is possible byheaterdust

concentration

concentration insidedegradation of thedifferential before and(item 4)temperature differential

switching between heaters using

constant monitoring of the(Pretreatmen

concentration

inside the PCV

the PCV increases

electric heater

after the electric

Item 7-3

Analysis
numbert equipment)

because the electric

caused by adhesion

heater deteriorates

of processing aid

and the design

An-Ki-11②

Point

before and after theheaterelectric heater

Presence or absence ofcountermeasures for disturbing
functions

Point

2 series of electric heaters
1(already studied)Point

and after the electric heater, but

Impact on
throughput
due to error
handling(Indirect
causes)Individual

item 7-1 is 1
point
1

4

predictability is poor.

performancevalue of the filter isprocessing point to(b) Amount of mist at

Indirectdegradation of the

Functionality is ensured byContinuous monitoring is

Becausenot ensured.

the electric heater

electric heater inlet(item 5)electric heater, andswitching between heaters using

required, but predictability isitem 7-1 is 1

because this trend isaffected by the amount

Point ofrepresent
ation

Becausetemperature differential before
4decreases due tomigrating from the

Effects on accurate and prompt
on-site response by workers

Item 7-4(Evaluation Results)

1

2 series of electric heaters(already studied)

3

good.

1

point

4

3

of mist inflow due to theprocessing aid.
(a) Temperature
Same asSame as

above

above

Same as above

Same as above③

An-Ki-12

Selected because theFunctionality is ensured by

Post-detection is possible bytemperature differential

switching between heaters using

constant monitoring of the

Performancedifferential before andDirectbefore and after the

degradation of theafter the electric(item 4)

electric heater

electric heater

heaterperformanceof anti-dispersion

degradation of theagent migrating fromto the electric heater

electric heater inlet

4(already studied)Indirect(item 5)

because this trend istemperature differential before

item 7-1 is 1
1

point

4

and after the electric heater, but
predictability is poor.

electric heater, and(b) Amount of mist at

2 series of electric heaters

decreases due tocaused by adhesion

the processing point

1

BecauseFunctionality is ensured by

Becauseswitching between heaters using

item 7-1 is 1
Continuous monitoring is

2 series of electric heaters
1(already studied)3

affected by the amountrequired, but predictability is

4

point
1

3

good.

of mist inflow due to theanti-dispersion agent.

Same asSame as

above

above

Same as above

Same as above

Performance(a) Temperature

DirectSelected because the

It is assumed that the

Post-detection is possible by

Becausedegradation of thedifferential before and(item 4)temperature differential

processing work will proceed

constant monitoring of theitem 7-1 is 1

electric heater

after the electric

before and after the

without exceeding the PCV

temperature differential before

caused by the rise inheaterelectric heater

PCV temperature④

during processing

design temperature4

decreases due todue to heat input
An-Ki-13

1

and after the electric heater, but

point
1

4

predictability is poor.

performance(b) Amount of heatIndirectdegradation of the

It is assumed that theAdvance detection is possible by

Becauseinput at processing(item 5)electric heater, andprocessing work will proceed

constant monitoring of theitem 7-1 is 1

point

because this trend iswithout exceeding the PCV

affected by the amountof heat input at the1design temperaturetemperature on the upstream side3of the electric heater, and

4

point
1

3

predictability is good

processing point whichraises the temperatureof inflowing gas.

©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-2: Risk assessment table for safety equipment (Detailed version) (10/48)
No.151■ Risk assessment table(gas phase confinement equipment)
Model ID
Process

Ko-3: Debris retrieval

Work

Sa-4

: Processing of debris■ Score table for item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still underdevelopment[2 points] Countermeasures exist, but there are no trackrecords of application at the Fukushima Daiichi[1 point] Countermeasures exist, and have been appliedat the Fukushima Daiichi.

■ Score table for item 7-2[4 points] Requires constant monitoring during task andpredictability is poor
[3 points] Requires constant monitoring during task but
predictability is good
[2 points] Requires regular monitoring and predictability
is poor[1 point] Requires regular monitoring and predictability is
good

Important monitoring items
Item 2Item 3Item 4Item 51

Item 5-2

Item 6-1

Item 6-2

Item 6-3

Targetequipment

The functionthat the target
is responsibleforWork delay
factor (=error)

Direct causesof error

Indirectcausesof error

Reasons to be
selected

Detectionrequirements toavoid work delays

Directmonitoring/I
ndirectmonitoring

Reason for
selection of
detectionrequirements

PCV(Primaryboundary)

Staticboundary

Decrease indifferential
pressure
betweeninside andoutside of
the PCV

An-Ki-14

Same asabove

An-Ki-15

Weighted evaluation of important monitoring items

Item 1Analysis
numberSame asabove

Same asabove

As the PCV
deteriorates
and the sizeof theopening
increases,
inleakageoccurs anddecreasesthedifferential
pressure
betweeninside andoutside of
the PCV.

Partialdamagecaused bycorrosion of
PCV wallsurface due toaccumulationof processingaid (mist)(a) Differential
pressure
between insideand outside of
the PCV

Direct(item 4)②(b) Amount andchemicalproperties (pH,chloride ion
concentration) of
mist flying to PCV
wall surface near
D/W water
surface

Partialdamage due
to corrosion of
PCV wallsurface byantidispersion
agent (mist)

Same asabove③■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is unknown[3 points] Countermeasures exist, but throughput decreases significantly due
to suspension of task
[2 points] Countermeasures exist, but throughput decreases due to workload
limitations[1 point] No impact on throughput, or when 7-1 is 1 point(a) Differential
pressure
between insideand outside of
the PCV(b) Amount andchemicalproperties (pH,chloride ion
concentration) of
mist flying to PCV
wall surface near
D/W water
surface

Indirect(item 5)

Direct(item 4)

Indirect(item 5)

Selected
becauseincrease in thesize of the
opening causedby the corrosionof the PCV wall
surfacedecreases thedifferential
pressure
between insideand outside of
the PCV, andbecause thistrend is affectedby the liquid
phase chemical
properties on
the PCV wall
surface.
Selected
becauseincrease in thesize of the
opening causedby the corrosionof the PCV wall
surfacedecreases thedifferential
pressure
between insideand outside of
the PCV, andbecause thistrend is affectedby the liquid
phase chemical
properties on
the PCV wall
surface.

Item 7-1

Point

4

4

4

4

Presence or absence ofcountermeasures for
disturbing functions

The impact on safetyfunctions is significant.
(Possibility of overspecification in caseof increased airflow
rate of fan; there areproblems with repair
after specifying thelocation of the
opening)
The impact on safetyfunctions is significant.
(Possibility of overspecification in caseof increased airflow
rate of fan; there areproblems with repair
after specifying thelocation of the
opening)
The impact on safetyfunctions is significant.
(Possibility of overspecification in caseof increased airflow
rate of fan; there areproblems with repair
after specifying thelocation of the
opening)
The impact on safetyfunctions is significant.
(Possibility of overspecification in caseof increased airflow
rate of fan; there areproblems with repair
after specifying thelocation of the
opening)

Item 7-2

Point

4

Effects on accurate
and prompt on-site
response by workers

Post-detection ispossible by constantmonitoring of thedifferential pressure
between inside andoutside of the PCV,
but predictability ispoor. It may bedifficult to identify thearea of damage.

Item 7-3

Point

4

Post-detection ispossible by constantmonitoring of thedifferential pressure
between inside andoutside of the PCV,
but predictability ispoor. It may bedifficult to identify thearea of damage.

3

3

The impact onsafety functions is
significant, andwork are shutdown
until PCV repair iscompleted.

48

3

The impact onsafety functions is
significant, andwork are shutdown
until PCV repair iscompleted.

48

3

The impact onsafety functions is
significant, andwork are shutdown
until PCV repair iscompleted.

Continuous
monitoring isrequired, but
predictability is poor.
4

Individual

The impact onsafety functions is
significant, andwork are shutdown
until PCV repair iscompleted.

Continuous
monitoring isrequired, but
predictability is poor.
4

Impact on throughput
due to error handling(Indirect causes)

Item 7-4(Evaluation Results)

Point ofrepresentation

48

48

48

48

©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-2: Risk assessment table for safety equipment (Detailed version) (11/48)
No.152■ Risk assessment table(gas phase confinement equipment)
Model ID
Process

Ko-3: Debris retrieval

Work

Sa-4

: Processing of debris■ Score table for item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still underdevelopment[2 points] Countermeasures exist, but there are no trackrecords of application at the Fukushima Daiichi[1 point] Countermeasures exist, and have been appliedat the Fukushima Daiichi.

■ Score table for item 7-2[4 points] Requires constant monitoring during task andpredictability is poor
[3 points] Requires constant monitoring during task but
predictability is good
[2 points] Requires regular monitoring and predictability
is poor[1 point] Requires regular monitoring and predictability is
good

Important monitoring items
Item 5-1■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is unknown[3 points] Countermeasures exist, but throughput decreases significantly due
to suspension of task
[2 points] Countermeasures exist, but throughput decreases due to workload
limitations[1 point] No impact on throughput, or when 7-1 is 1 point

Weighted evaluation of important monitoring items

Item 1

Item 2Item 3Item 4Item 5-2

Item 6-1

Item 6-2

Item 6-3

Targetequipment

The functionthat the target is
responsible forWork delay
factor (= error)

Directcauses oferror

Reasons to be
selected

Detectionrequirements to avoid
work delays

Directmonitoring/In
directmonitoring

Reason for selection of
detection requirements

Filter casing

Static boundary

Decrease in

As the filter

Partial damage due(a) Differential

Selected because partial

Although there is an

Post-detection is

Because item 7-1

differential

casingto corrosion of dust

pressure between

damage to the filter casing

impact on safety

possible byis 1 point

pressure

deteriorates

migrating from theinside and outside ofcauses an increase in thefunctions, the frequency

constant monitoring

between inside

and the size

processing point to

the PCV + pressure

primary boundary openingof occurrence isof the differential

and outside ofof thethe filter casing

inside the system

which decreases the

expected to be low

the PCV

opening

Analysis
numberIndirect causesof error

Direct(item 4)increases,
inleakage

Point

differential pressure

1

between inside andItem 7-2

Presence or absence ofcountermeasures for
disturbing functions

Point

Effects on accurate
and prompt on-site
response byworkers

4

boundary sections.

poor. It may bedecreases

affected by the amountdifficult to identify

theand chemical properties

the area of damage.
Continuous
monitoring isrequired, but
predictability ispoor.

(b) Amount and(pH, chloride ionpressurechemical properties

concentration, chemical

between(pH, chloride ion

inside andconcentration,

outside ofchemical composition)

the PCV.

of dust at filter casing

Indirect(item 5)

Although there is an
impact on safetyfunctions, the frequencyof occurrence is
expected to be low
compared to otherboundary sections.

composition) of dust
flowing into the filter1

casing.

Impact on
throughput due toerror handling(Indirect causes)

Indiv
idual

Point ofrepresentati
on

1

4

of the PCV, but
predictability isdifferential

Pointinside and outside

because this trend is①

Item 7-4(Evaluation
Results)

Item 7-3

pressure between

compared to otheroutside of the PCV, andoccurs andAn-Ki-16

Item 7-1

4

4

Because item 7-1
is 1 point

1

4

inlet
Partial damage due(a) Differential

Selected because partial

Although there is an

Post-detection is

Because item 7-1

to irradiation of dust

pressure between

damage to the filter casing

impact on safety

possible byis 1 point

migrating from theinside and outside ofcauses an increase in thefunctions, the frequency

constant monitoringprocessing point to

the PCV + pressure

primary boundary openingof occurrence isof the differential

the filter casing

inside the system

which decreases the

expected to be low

Direct(item 4)Same asabove

An-Ki-17

Same as above

Same as above

differential pressure

1

between inside andpressure between

compared to other4boundary sections.

inside and outside

Same asoutside of the PCV, andpredictability is

abovebecause this trend ispoor. It may beaffected by the amountdifficult to identify

Same as above

1

4of the PCV, but

and nuclide composition of4

the area of damage.

(b) Amount anddust flowing into the filter

Although there is an

Continuous

Because item 7-1

nuclide composition ofcasing.

impact on safety

monitoring is

is 1 point

functions, the frequency

required, but

dust at filter casing
inletof occurrence isIndirect(item 5)1

expected to be low

predictability is
4

poor.

1

4

compared to otherboundary sections.

©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-2: Risk assessment table for safety equipment (Detailed version) (12/48)
No.153■ Risk assessment table(gas phase confinement equipment)
Model ID
Process

Ko-3: Debris retrieval

Work

Sa-4

: Processing of debris■ Score table for item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still underdevelopment[2 points] Countermeasures exist, but there are no trackrecords of application at the Fukushima Daiichi[1 point] Countermeasures exist, and have been applied at
the Fukushima Daiichi.

■ Score table for item 7-2[4 points] Requires constant monitoring during task
and predictability is poor
[3 points] Requires constant monitoring during task
but predictability is good
[2 points] Requires regular monitoring andpredictability is poor
[1 point] Requires regular monitoring andpredictability is good

Important monitoring items■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is unknown[3 points] Countermeasures exist, but throughput decreases
significantly due to suspension of task
[2 points] Countermeasures exist, but throughput decreases due toworkload limitations[1 point] No impact on throughput, or when 7-1 is 1 point

Weighted evaluation of important monitoring items

Item 1

Item 2Item 3Item 4Item 5-1

Item 5-2

Item 6-1

Item 6-2

Item 6-3

Targetequipment

The functionthat thetarget is
responsibleforWork delay
factor (=error)

Direct causes of
error

Indirectcauses oferror

Reasons to be
selected

Detectionrequirements toavoid work delays

Directmonitoring/
Indirect
monitoring

Reason for selection of detection
requirements

Filter casing

StaticDecrease in

As the filter casing

Partial damage due(a) Differential

DirectSelected because partial damage

Functionality is ensured by

Post-detection is possible by

Because item 7-1 isboundarydifferential

deteriorates and theto adhesion ofpressure between(item 4)to the filter casing causes an

installing a demister and electric

constant monitoring of the

1 point

pressure

size of the opening

processing aid

inside and outside ofincrease in the primary boundary

heater at the first-stage filter

differential pressure

betweenincreases,

migrating from thethe PCV + pressure

opening which decreases theinside andinleakage occurs

processing point to

inside the systemdifferential pressure betweenof the PCV, but predictability

outside ofand decreases theinside and outside of the PCV,is poor. It may be difficult to

the PCVdifferential pressure

and because this trend is affected

identify the area of damage.

Analysis
number

An-Ki-18

the filter casing②

between inside andoutside of the PCV.

(b) Amount of mist at

Indirectfilter casing inlet(item 5)Item 7-1

Point

1

by the amount of mist flowing into
the filter casing.
1

Presence or absence ofcountermeasures for disturbing
functions(already studied)

Item 7-2

Point

4

Effects on accurate andprompt on-site response byworkers

between inside and outside

Functionality is ensured byContinuous monitoring isinstalling a demister and electric

required, but predictability isheater at the first-stage filter

3

good.

Item 7-3

Point

Impact on throughput
due to error handling(Indirect causes)

1

Item 7-4(Evaluation Results)

Individual

Point ofrepresentation

44
Because item 7-1 is

1 point13(already studied)

Same asSame asSame as

above

above

above

Same as above③

An-Ki-19

Partial damage due(a) Differential

Selected because partial damage

Functionality is ensured by

Post-detection is possible by

Because item 7-1 isto adhesion of anti-pressure between

to the filter casing causes an

installing a demister and electric

constant monitoring of the

1 point

dispersion agent

inside and outside ofincrease in the primary boundary

heater at the first-stage filter

differential pressure

migrating from thethe PCV + pressure

processing point to

inside the system

Direct(item 4)the filter casing

opening which decreases the1(already studied)4of the PCV, but predictability

inside and outside of the PCV,is poor. It may be difficult toand because this trend is affected(b) Amount of mist at
filter casing inlet

Duct

An-Ki-20

4

4Continuous monitoring isinstalling a demister and electric

the filter casing.
1(item 5)1

identify the area of damage.
Functionality is ensured byby the amount of mist flowing into
Indirect

between inside and outside

differential pressure between

heater at the first-stage filter

Because item 7-1 isrequired, but predictability is
3

good.

1 point13(already studied)

StaticDecrease in

As the duct

Partial damage due(a) Differential

Selected because partial damage

Although there is an impact on

Post-detection is possible by

Because item 7-1 isboundarydifferential

deteriorates and theto corrosion of dust

pressure between

to the duct causes an increase insafety functions, the frequency ofconstant monitoring of the

1 point

pressure

size of the opening

migrating from theinside and outside of

the primary boundary opening

occurrence is expected to be low

differential pressure

betweenincreases,

processing point to

the PCV + pressure

inside andinleakage occurs

the duct

inside the systemoutside ofand decreases theoutside of the PCV, and because

the PCVdifferential pressure

this trend is affected by the

between inside andoutside of the PCV.

①

Direct(item 4)

which decreases the differential

1pressure between inside andcompared to other boundary

4

sections.

between inside and outside

1

4of the PCV, but predictability
is poor. It may be difficult to
identify the area of damage.

(b)(b) Amount andamount and chemical properties

Although there is an impact onContinuous monitoring is

Because item 7-1 ischemical properties(pH, chloride ion concentration,

safety functions, the frequency of

required, but predictability is

1 point(pH, chloride ion
concentration,
chemicaloccurrence is expected to be low

and chemical composition) of dust
Indirect(item 5)flowing into the exhaust line.

1

compared to other boundary

4

poor.
4

1

4

sections.

composition) of dust
at exhaust line inlet©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-2: Risk assessment table for safety equipment (Detailed version) (13/48)
No.154■ Risk assessment table(gas phase confinement equipment)
Model ID
Process

Ko-3: Debris retrieval

Work

Sa-4

: Processing of debris■ Score table for item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still underdevelopment[2 points] Countermeasures exist, but there are no trackrecords of application at the Fukushima Daiichi[1 point] Countermeasures exist, and have been appliedat the Fukushima Daiichi.

■ Score table for item 7-2[4 points] Requires constant monitoring during task andpredictability is poor
[3 points] Requires constant monitoring during task but
predictability is good
[2 points] Requires regular monitoring and predictability
is poor[1 point] Requires regular monitoring and predictability is
good

Important monitoring items

Weighted evaluation of important monitoring items

Item 1

Item 2Item 3Item 4Item 5-1

Item 5-2

Item 6-1

Item 6-2

Item 6-3

Targetequipment

The functionthat thetarget is
responsibleforWork delay
factor (=error)

Direct causes of
error

Indirectcauses oferror

Reasons to be
selected

Detectionrequirements toavoid work delays

Directmonitoring/I
ndirectmonitoring

Reason for selection of detection
requirements

Analysis
numberDuct

Staticboundary

An-Ki-21■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is unknown[3 points] Countermeasures exist, but throughput decreases significantly due
to suspension of task
[2 points] Countermeasures exist, but throughput decreases due to workload
limitations[1 point] No impact on throughput, or when 7-1 is 1 point

Item 7-1

Point

Presence or absence ofcountermeasures for disturbing
functions

Item 7-2

Point

Effects on accurate and prompt on-site
response by workers

Item 7-3

Point

Impact on
throughput due toerror handling(Indirect causes)

As the duct

Partial damage due(a) Differential

Selected because partial damage

Although there is an impact on

Post-detection is possible by constantBecause item 7-1

Decrease indeteriorates and theto irradiation of dust

pressure between

to the duct causes an increase insafety functions, the frequency ofmonitoring of the differential pressureis 1 point

differential

size of the opening

migrating from theinside and outside of

the primary boundary opening

occurrence is expected to be low

between inside and outside of thepressure

increases,

processing point to

the PCV + pressure

betweeninleakage occurs

the duct

inside the system

inside andand decreases theoutside ofdifferential pressure

the PCV

between inside andDirect(item 4)

which decreases the differential
pressure between inside andcompared to other boundary
1

sections.

Item 7-4(Evaluation
Results)

Indiv
idual

PCV, but predictability is poor. It may
4outside of the PCV, and because

be difficult to identify the area of

1

4

damage.

this trend is affected by the①

Point ofrepresent
ation

4

amount and nuclide composition

outside of the PCV.

of dust flowing into the exhaust(b) Amount andnuclide compositionof dust at exhaustline inlet

line.
Indirect1(item 5)

Although there is an impact onContinuous monitoring is required, butsafety functions, the frequency of

predictability is poor.

occurrence is expected to be low

4

Because item 7-1

is 1 point
1

4

compared to other boundary
sections.

Same asSame asSame as

above

above

above

Same as above②

An-Ki-22

Partial damage due(a) Differential

Selected because damage to the

Although there is an impact on

Post-detection is possible by constantBecause item 7-1

to adhesion ofpressure between

duct causes an increase in thesafety functions, the frequency ofmonitoring of the differential pressureis 1 point

processing aid

inside and outside of

Directprimary boundary opening which

occurrence is expected to be low

between inside and outside of the

migrating from thethe PCV + pressure(item 4)decreases the differential

processing point to

inside the system

1pressure between inside andthe ductcompared to other boundary

4

sections.

exhaust line inlet

Although there is an impact onamount of mist flowing into theexhaust line.

(item 5)

4

damage.

this trend is affected by the
Indirect1

be difficult to identify the area ofoutside of the PCV, and because(b) Amount of mist at

PCV, but predictability is poor. It may

safety functions, the frequency of1

occurrence is expected to be low

4Continuous monitoring is required, but

Because item 7-1

predictability is good.
3

is 1 point
1

3

compared to other boundary
sections.

An-Ki-23

Same asSame asSame as

above

above

above

Same as above③

Partial damage due(a) Differential

Selected because partial damage

Although there is an impact on

Post-detection is possible by constantto adhesion of anti-pressure between

to the duct causes an increase insafety functions, the frequency ofmonitoring of the differential pressure

dispersion agent

inside and outside ofmigrating from thethe PCV + pressure

processing point to

inside the system

Directthe primary boundary opening(item 4)

which decreases the differential

occurrence is expected to be low
1pressure between inside andthe ductcompared to other boundary
sections.

(item 5)exhaust line.

4

be difficult to identify the area of

Although there is an impact onamount of mist flowing into theIndirect

PCV, but predictability is poor. It may

1

damage.

this trend is affected by theexhaust line inlet

is 1 point

between inside and outside of the4outside of the PCV, and because(b) Amount of mist at

Because item 7-1

safety functions, the frequency of1

occurrence is expected to be low

4Continuous monitoring is required, but

Because item 7-1

predictability is good.
3

is 1 point
1

3

compared to other boundary
sections.

©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-2: Risk assessment table for safety equipment (Detailed version) (14/48)■ Risk assessment table
No.155(gas phase confinement equipment)
Model ID
Process

Ko-3: Debris retrieval

Work

Sa-4

: Processing of debris■ Score table for item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still underdevelopment[2 points] Countermeasures exist, but there are no trackrecords of application at the Fukushima Daiichi[1 point] Countermeasures exist, and have been applied at the
Fukushima Daiichi.

■ Score table for item 7-2[4 points] Requires constant monitoring during task andpredictability is poor
[3 points] Requires constant monitoring during task but
predictability is good
[2 points] Requires regular monitoring and predictability is poor
[1 point] Requires regular monitoring and predictability is good

Important monitoring items
Item 1Analysis
numberItem 2Item 3Item 4

Targetequipment

The functionthat the target
Work delay
Direct causes of error
is responsible factor (= error)
for

Isolation

StaticDecrease in

As the isolation

valve

boundarydifferential

valve deteriorates(Integrationpressureof valvespresent in
the system)

Item 5-1

Item 5-2

Indirectcauses oferror

Reasons to be
selected

Weighted evaluation of important monitoring items
Item 6-1

Item 6-2

Item 6-3

DirectDetection requirements monitoring/In
to avoid work delays
directmonitoring

Reason for selection of detection
requirements

Partial damage due(a) Differential

Selected because partial damage

to corrosion of dust

pressure between

to the isolation valve causes anand the size of the

migrating from theinside and outside ofincrease in the primary boundary

betweenopening increases,

processing point to

the PCV + pressure

inside andinleakage occurs

the isolation valve

inside the systemoutside ofand decreases thethe PCVdifferential pressure
between inside andAn-Ki-24■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is unknown[3 points] Countermeasures exist, but throughput decreases significantly due tosuspension of task
[2 points] Countermeasures exist, but throughput decreases due to workload
limitations[1 point] No impact on throughput, or when 7-1 is 1 point

Direct(item 4)Item 7-1

Point

opening which decreases thedifferential pressure between

Presence or absence ofcountermeasures for disturbing
functions

Item 7-2

Item 7-4(Evaluation
Results)

Effects on accurate and prompt onPointsite response by workers

Impact on throughput due
Point ofIndivito error handling (Indirect
representdual
causes)ation

Although there is an impact on

Post-detection is possible by

Because item 7-1 is 1

safety functions, the frequency ofconstant monitoring of thepoint

occurrence is expected to be low

differential pressure between

Point

compared to other boundary

1

Item 7-3

sections.

inside and outside of the PCV, but

4predictability is poor. It may beinside and outside of the PCV,

difficult to identify the area ofand because this trend is affected

damage.

1

4by the amount and chemical①

outside of the PCV.

concentration, and chemicalchemical properties

composition) of dust flowing into

(pH, chloride ion
concentration,
chemical

4

properties (pH, chloride ion(b)(b) Amount andIndirect

Continuous monitoring is

Because item 7-1 is 1

safety functions, the frequency of

required, but predictability is poor.

pointoccurrence is expected to be low

the exhaust line.
1(item 5)

Although there is an impact oncompared to other boundary

4

1

4

sections.

composition) of dust
at exhaust line inlet

Same asSame asSame as

above

above

above

Same as above

An-Ki-25

Partial damage due(a) Differential

Selected because partial damage

Although there is an impact on

Post-detection is possible by

Because item 7-1 is 1

to irradiation of dust

pressure between

to the isolation valve causes ansafety functions, the frequency ofconstant monitoring of thepoint

migrating from theinside and outside ofincrease in the primary boundary

occurrence is expected to be low

differential pressure between

processing point to

the PCV + pressure

the isolation valve

inside the system

Direct(item 4)

opening which decreases theSame asinside and outside of the PCV,

above

and because this trend is affected(b) Amount andline inlet

Indirect(item 5)

4

inside and outside of the PCV, but

1

4

predictability is poor. It may bedifficult to identify the area of

4damage.
Although there is an impact onContinuous monitoring issafety functions, the frequency ofcomposition of dust flowing into
the exhaust line.

compared to other boundary
sections.

by the amount and nuclide

nuclide compositionof dust at exhaust1

differential pressure between

1occurrence is expected to be low

Because item 7-1 is 1

required, but predictability is poor.
4

point
1

4

compared to other boundary
sections.

An-Ki-26

Same asSame asSame as

above

above

above

Same as above②

Partial damage due(a) Differential

Selected because partial damage

Although there is an impact on

Post-detection is possible by

Because item 7-1 is 1

to adhesion ofpressure between

to the isolation valve causes ansafety functions, the frequency ofconstant monitoring of the

pointprocessing aid

inside and outside ofincrease in the primary boundary

occurrence is expected to be low

differential pressure between

migrating from thethe PCV + pressure

processing point to

inside the system

Direct(item 4)the isolation valve

opening which decreases the1

differential pressure between thecompared to other boundary

4

sections.

(item 5)

4

damage.
Although there is an impact onby the amount of mist flowing into
Indirect4

difficult to identify the area ofand because this trend is affectedexhaust line inlet1

predictability is poor. It may beinside and outside of the PCV,(b) Amount of mist at

inside and outside of the PCV, but

Continuous monitoring issafety functions, the frequency ofthe exhaust line.
1

occurrence is expected to be low

Because item 7-1 is 1

required, but predictability is
3

good.

point
1

3

compared to other boundary
sections.

©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-2: Risk assessment table for safety equipment (Detailed version) (15/48)
No.156■ Risk assessment table(gas phase confinement equipment)
Model ID
Process

Ko-3: Debris retrieval

Work

Sa-4

: Processing of debris■ Score table for item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still underdevelopment[2 points] Countermeasures exist, but there are no trackrecords of application at the Fukushima Daiichi[1 point] Countermeasures exist, and have been applied at the
Fukushima Daiichi.

■ Score table for item 7-2[4 points] Requires constant monitoring during task andpredictability is poor
[3 points] Requires constant monitoring during task but
predictability is good
[2 points] Requires regular monitoring and predictability is poor
[1 point] Requires regular monitoring and predictability is good

Important monitoring items■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is unknown[3 points] Countermeasures exist, but throughput decreases significantly due tosuspension of task
[2 points] Countermeasures exist, but throughput decreases due to workload
limitations[1 point] No impact on throughput, or when 7-1 is 1 point

Weighted evaluation of important monitoring items

Item 1

Item 2Item 3Item 4Item 5-1

Item 5-2

Item 6-1

Item 6-2

Item 6-3

Targetequipment

The functionthat thetarget is
responsibleforWork delay
factor (=error)

Direct causes of
error

Indirectcauses oferror

Reasons to be
selected

Detectionrequirements toavoid work delays

Directmonitoring/I
ndirectmonitoring

Reason for selection of detection
requirements

Isolation

StaticDecrease in

As the isolation

Partial damage due(a) Differential

Selected because partial damage

Although there is an impact on

Post-detection is possible by

Because item 7-1

valve

boundarydifferential

valve deteriorates

to adherence of anti-pressure between

to the isolation valve causes ansafety functions, the frequency

constant monitoring of theis 1 point(Integrationpressure

and the size of thedispersion agent

inside and outside ofincrease in the primary boundaryof occurrence is expected to bedifferential pressure betweenof valves

betweenopening increases,

migrating from thethe PCV + pressure

present in

inside andinleakage occurs

processing point to

inside the system

the system)

outside ofand decreases thethe isolation valve

the PCVdifferential pressure

Analysis
number

An-Ki-27

Direct(item 4)③

differential pressure between the

Presence or absence ofcountermeasures for disturbing
functions

Item 7-2

Point

low compared to other boundary
1

sections.

Effects on accurate and prompt
on-site response by workers

but predictability is poor. It may
be difficult to identify the area ofand because this trend is affected

damage.

outside of the PCV.

the exhaust line.

Indirect1(item 5)

Although there is an impact onContinuous monitoring issafety functions, the frequency

required, but predictability isof occurrence is expected to be

Item 7-4(Evaluation
Results)

Item 7-3

Point

Impact on
throughput due toerror handling(Indirect causes)

Individual

Point ofrepresent
ation

inside and outside of the PCV,
4

inside and outside of the PCV,by the amount of mist flowing into

exhaust line inlet

Point

opening which decreases the

between inside and(b) Amount of mist at

Item 7-1

3

good.

1

4

4

Because item 7-1
is 1 point13

low compared to other boundary
sections.

HEPA filter

Dynamic

Decrease in

As filter elements

Partial blockage of(a) HEPA filter

Selected because dust

Functionality is ensured byFilter clogging is due to dailyboundarydifferential

deteriorate and thethe filter element due

differential pressure

accumulation increases theswitching filters through 2 series

accumulation, so predictability ispressure

design value of theto accumulation of+ differential

Directdifferential pressure, and because

betweenexhauster is notdust migrating frompressure between(item 4)

this trend is affected by theinside andensured, thethe processing point

inside and outside ofamount and particle size

outside of

exhaust airflow rate

to the HEPA filter

the PCV

distribution of dust flowing into thethe PCVdecreases and the(b) Dust amount andHEPA filter.

differential pressure

particle size

between inside anddistribution at theoutside of the PCVHEPA filter inlet

An-Ki-28①

1

of filters (already studied)1

1(item 5)is 1 point1

1

3
Functionality is ensured byContinuous monitoring isswitching filters through 2 series
Indirectgood

Because item 7-1

of filters (already studied)Because item 7-1

required, but predictability is
3

good.

is 1 point
1

3

decreases.

Same asSame asSame as

above

above

above

Same as above

Partial damage(a) HEPA filter

caused by the

upstream/downstrea

deterioration of filterm dust concentration

elements due to dust

ratio

Direct(item 4)migrating from theAn-Ki-29

Same asabove

Deterioration of filter elements

Functionality is ensured by

Post-detection is possible bydue to accumulation of dust in theswitching filters through 2 series

constant monitoring of the dust

HEPA filter causes partial

1of filters (already studied)4

damage to filter elements andconcentration on the downstream

Because item 7-1

is 1 point
1

4

side of the filter, but predictability

decreases the ratio of dust

is poorprocessing point to(b) Amount andconcentration between the

Functionality is ensured byContinuous monitoring is

Because item 7-1

the HEPA filter

chemical properties

upstream and downstream sides.

switching filters through 2 seriesrequired, but predictability is poor.

is 1 point(pH, chloride ion

Selected because this trend isof filters (already studied)concentration,
chemicalIndirectaffected by the amount and(item 5)chemical properties (pH, chloride

composition) of dust

ion concentration, chemical

at HEPA filter inlet

composition) of dust flowing into

1

4

1

4

4

the filter.

©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-2: Risk assessment table for safety equipment (Detailed version) (16/48)
No.157■ Risk assessment table(gas phase confinement equipment)■ Score table for item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still underdevelopment[2 points] Countermeasures exist, but there are no trackrecords of application at the Fukushima Daiichi[1 point] Countermeasures exist, and have been appliedat the Fukushima Daiichi.

Model ID
Process

Ko-3: Debris retrieval

Work

Sa-4

: Processing of debris■ Score table for item 7-2[4 points] Requires constant monitoring during task andpredictability is poor
[3 points] Requires constant monitoring during task but
predictability is good
[2 points] Requires regular monitoring and predictability
is poor[1 point] Requires regular monitoring and predictability is
good

Important monitoring items■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is unknown[3 points] Countermeasures exist, but throughput decreases significantly due
to suspension of task
[2 points] Countermeasures exist, but throughput decreases due to workload
limitations[1 point] No impact on throughput, or when 7-1 is 1 point

Weighted evaluation of important monitoring items

Item 1

Item 2Item 3Item 4Item 5-1

Item 5-2

Item 6-1

Item 6-2

Item 6-3

Targetequipment

The functionthat thetarget is
responsibleforWork delay
factor (=error)

Direct causes of
error

Indirectcauses oferror

Reasons to be
selected

Detectionrequirements toavoid work delays

Directmonitoring/
Indirect
monitoring

Reason for selection of detection
requirements

HEPA filter

Dynamic

Decrease in

As filter elements

Partial damage to(a) HEPA filter

Partial damage to filter elements

Functionality is ensured by

Post-detection is possible by

Because item 7-1 is 1

boundarydifferential

deteriorate and thefilter elements due

upstream/downstrea

due to irradiation of dust

switching filters through 2

constant monitoring of the dust

point

pressure

design value of theto irradiation of dust

m dustaccumulated in the HEPA filter

series of filters (already studied)concentration on the

Analysis
number

An-Ki-30

betweenexhauster is not

migrating from theinside andensured, theprocessing point tooutside of

exhaust airflow

the PCVrate decreases and①

concentration ratio

Direct(item 4)the HEPA filter

decreases the ratio of dust

Item 7-1

Point

Presence or absence ofcountermeasures for disturbing
functions

1

Item 7-2

Point

4

concentration between the

Effects on accurate and prompt
on-site response by workers

downstream side of the filter, but

Item 7-3

Point

Impact on throughput
due to error handling(Indirect causes)

1

Item 7-4(Evaluation
Results)
Indiv
idual

4

predictability is poor

upstream and downstream
4sides. Selected because thisthe differential(b) Amount andpressure between

nuclide composition

inside and outsideof dust at HEPAof the PCVPoint ofrepresentationfilter inlet

trend is affected by the amountFunctionality is ensured by

and nuclide composition ofIndirectinflowing dust.

(item 5)

Continuous monitoring isswitching filters through 2
1

series of filters (already studied)Because item 7-1 is 1

required, but predictability is
4

poor.

point
1

4

decreases.

Same asSame asSame as

above

above

above

Same as above

Partial blockage due(a) HEPA filter

to adhesion ofdifferential pressure

processing aid②

Direct(item 4)migrating from theAn-Ki-31

Selected because dust(b) Amount of mist
at HEPA filter inlet

Same asSame as

above

above

above

Same as above

Indirect1

good

Because item 7-1 is 1
point
1

1

filter (already studied)
Functionality is ensured byinstalling a demister andthe amount of mist flowing into
the HEPA filter due to theContinuous monitoring is

1electric heater at the first-stage

processing aid.

filter (already studied)

good.

Selected because the relative

Functionality is ensured by

Post-detection is possible byat HEPA filter inlet

humidity of gas flowing into theinstalling a demister andconstant monitoring of the

Direct(item 4)

HEPA filter was verified to1

deviate from the design

electric heater at the first-stage

4

filter (already studied)temperature differential before

point
1

3

Because item 7-1 is 1
point
1

4

and after the electric heater, butcondition, and because this trend

predictability is poor

which is a design(b) Amount of mist

is affected by the amount of

Functionality is ensured byContinuous monitoring is

Because item 7-1 is 1

condition, exceeding

sprayed atprocessing aid (mist) sprayed at

installing a demister andrequired, but predictability is

point

the design

processing point

assumption, as a

Indirect(item 5)3

Because item 7-1 is 1

required, but predictability is
3(a) Relative humidity

by relative humidity

aboveelectric heater at the first-stage

degradation of the
HEPA filter caused

Same asaccumulation, so predictability is

Performanceat HEPA filter inlet,
An-Ki-32

increases the HEPA filter

because this trend is affected by(item 5)Same as1

Filter clogging is due to daily

installing a demister anddifferential pressure, andprocessing point to
the HEPA filter

accumulation in the HEPA filter

Functionality is ensured byelectric heater at the first-stage

the processing point.
1

filter (already studied)

4

good.
3

1

3

result of debris
retrieval operations©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-2: Risk assessment table for safety equipment (Detailed version) (17/48)
No.158■ Risk assessment table(gas phase confinement equipment)
Model ID
Process

Ko-3: Debris retrieval

Work

Sa-4

: Processing of debris■ Score table for item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still underdevelopment[2 points] Countermeasures exist, but there are no trackrecords of application at the Fukushima Daiichi[1 point] Countermeasures exist, and have been appliedat the Fukushima Daiichi.

■ Score table for item 7-2[4 points] Requires constant monitoring during task andpredictability is poor
[3 points] Requires constant monitoring during task but
predictability is good
[2 points] Requires regular monitoring and predictability
is poor[1 point] Requires regular monitoring and predictability is
good

Important monitoring items■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is unknown[3 points] Countermeasures exist, but throughput decreases significantly due
to suspension of task
[2 points] Countermeasures exist, but throughput decreases due to workload
limitations[1 point] No impact on throughput, or when 7-1 is 1 point

Weighted evaluation of important monitoring items

Item 1

Item 2Item 3Item 4Item 5-1

Item 5-2

Item 6-1

Item 6-2

Item 6-3

Targetequipment

The functionthat thetarget is
responsibleforWork delay
factor (=error)

Direct causes of
error

Indirectcauses oferror

Reasons to be
selected

Detectionrequirements toavoid work delays

Directmonitoring/
Indirect
monitoring

Reason for selection of detection
requirements

HEPA filter

Dynamic

Decrease in

As filter elements

Partial blockage due(a) HEPA filter

Selected because dust

Functionality is ensured byFilter clogging is due to dailyboundarydifferential

deteriorate and theto dispersion of anti-

differential pressure

accumulation in the HEPA filter

installing a demister and electric

accumulation, so predictability ispressure

design value of thedispersion agent

Directincreases the HEPA filter

betweenexhauster is not

migrating from the(item 4)differential pressure, andinside andensured, theoutside of

exhaust airflow rate

the PCVdecreases and theAnalysis
number

An-Ki-33

processing point to③

the HEPA filter

Item 7-1

Point

1

Presence or absence ofcountermeasures for disturbing
functionsheater at the first-stage filter

Item 7-2

Point

1

Effects on accurate and prompt
on-site response by workers

good

Point

Item 7-3

Item 7-4(Evaluation Results)

Impact on
throughput due toerror handling(Indirect causes)

Individual

Point ofrepresentationBecause item 7-1
is 1 point
11(already studied)because this trend is affected by
the amount of mist flowing into(b) Amount of mist at

the HEPA filter due to the

HEPA filter inlet

differential

processing aid.
Indirectpressure between
inside and outside

Continuous monitoring is

Because item 7-1

installing a demister and electric

required, but predictability is

is 1 point

heater at the first-stage filter
1(item 5)Functionality is ensured by(already studied)

3

good.
3

1

3

of the PCV

decreases.

Same asSame asSame as

above

above

above

Same as above

Performance(a) Relative humidity

Selected because the relative

degradation of theat HEPA filter inlet

humidity of gas flowing into the

HEPA filter caused

DirectHEPA filter was verified toby relative humidity(item 4)

deviate from the design condition,

at HEPA filter inlet,
An-Ki-34

Post-detection is possible by1

and because this trend is affected

Same aswhich is a design

above

condition, exceeding(b) Amount of mist

agent (mist) sprayed at thethe design

sprayed atprocessing point.

assumption, as aprocessing pointtemperature differential before
and after the electric heater, but

is 1 point
1

4

predictability is poor

(already studied)Indirect

Functionality is ensured by1(item 5)installing a demister and electricheater at the first-stage filter

3

Continuous monitoring is

Because item 7-1

required, but predictability is

is 1 point

good.

1

Dynamic

Decrease in

As the exhauster

Partial damage to(a) Airflow rate ofCorrosion of filter elements due toFunctionality is ensured by

Post-detection is possible byboundarydifferential

deteriorates andthe exhauster due toexhauster

dust accumulated in theswitching filters through 2 series

constant monitoring of the dust

pressure

the design value of

corrosion of dust

Directexhauster causes partial damage

betweenthe exhauster is not

migrating from the(item 4)to the exhauster and decreases

side of the filter, but predictability

inside andensured, theprocessing point tothe airflow rate of exhauster.

is pooroutside of

exhaust airflow rate

the exhauster

Selected because this trend is

the PCVdecreases and the3

1of filters (already studied)

4

concentration on the downstream

Because item 7-1
is 1 point
14(b) Amount andaffected by the amount andFunctionality is ensured byContinuous monitoring is

Because item 7-1

differential

chemical properties

chemical properties (pH, chloride

switching filters through 2 seriesrequired, but predictability is

is 1 point

pressure between(pH, chloride ion

inside and outside

concentration,of the PCV

chemicaldecreases.

composition) of dust①

4

(already studied)retrieval operations

An-Ki-35

heater at the first-stage filter4by the amount of anti-dispersion

result of debris

Exhauster

installing a demister and electric

Because item 7-1

constant monitoring of the

Functionality is ensured byIndirect(item 5)of filters (already studied)ion concentration, and chemicalcomposition) of dust flowing into

1

4

poor.
4

1

4

the exhauster.

at exhauster inlet©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-2: Risk assessment table for safety equipment (Detailed version) (18/48)
No.159■ Risk assessment table(gas phase confinement equipment)
Model ID
Process

Ko-3: Debris retrieval

Work

Sa-4

: Processing of debris■ Score table for item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still underdevelopment[2 points] Countermeasures exist, but there are no trackrecords of application at the Fukushima Daiichi[1 point] Countermeasures exist, and have been appliedat the Fukushima Daiichi.

■ Score table for item 7-2[4 points] Requires constant monitoring during task andpredictability is poor
[3 points] Requires constant monitoring during task but
predictability is good
[2 points] Requires regular monitoring and predictability
is poor[1 point] Requires regular monitoring and predictability is
good

Important monitoring items■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is unknown[3 points] Countermeasures exist, but throughput decreases significantly due
to suspension of task
[2 points] Countermeasures exist, but throughput decreases due to workload
limitations[1 point] No impact on throughput, or when 7-1 is 1 point

Weighted evaluation of important monitoring items

Item 1

Item 2Item 3Item 4Item 5-1

Item 5-2

Item 6-1

Item 6-2

Item 6-3

Targetequipment

The functionthat thetarget is
responsibleforWork delay
factor (=error)

Direct causes of
error

Indirectcauses oferror

Reasons to be
selected

Detectionrequirements toavoid work delays

Directmonitoring/I
ndirectmonitoring

Reason for selection of detection
requirements

Exhauster

Dynamic

Decrease in

As the exhauster

Partial damage to(a) Airflow rate of

Irradiation of dust accumulated in

Functionality is ensured by

Post-detection is possible byboundarydifferential

deteriorates andthe exhauster due toexhauster

the exhauster causes partial

switching filters through 2 series

constant monitoring of the dust

pressure

the design value ofirradiation of dust

Directdamage to the exhauster andbetweenthe exhauster is not

migrating from the(item 4)decreases the airflow rate ofinside andensured, theoutside of

exhaust airflow rate

Analysis
number

An-Ki-36

the PCVdecreases and theprocessing point toSame asthe exhauster

above

Presence or absence ofcountermeasures for disturbing
functionsof filters (already studied)

Point

4

inlet

(item 5)

Performance(a) Airflow rate of

Directdegradation of theexhauster(item 4)

Effects on accurate and prompt
on-site response by workers

concentration on the downstream

Point

Item 7-3

Item 7-4(Evaluation Results)

Impact on
throughput due toerror handling(Indirect causes)

Individual

Point ofrepresent
ation

Because item 7-1
is 1 point
1

4

side of the filter, but predictability
is poor
Functionality is ensured by

and nuclide composition ofIndirectoutside of the PCV

1trend is affected by the amountof dust at exhauster

between inside andPoint

Item 7-2

exhauster. Selected because this(b) Amount andnuclide compositiondifferential pressure

Item 7-1

Continuous monitoring isswitching filters through 2 series

inflowing dust.
1of filters (already studied)required, but predictability is poor.
44Because item 7-1
is 1 point
1

4

decreases.

Same asSame asSame as

above

above

above

Same as above

exhauster caused by④

An-Ki-37

heat input during
processing

performance deterioration of the

input at processing
point

Indirect(Item 4)3

1

inflowing gas.

processing work will proceedwithout exceeding the PCV

required, but predictability is

is 1 point
1

3

good.

It is assumed that the

input at the processing point
which raises the temperature ofwithout exceeding the PCVContinuous monitoring isdesign temperature

is affected by the amount of heat(b) Amount of heatprocessing work will proceed3

Advance detection is possible by

Because item 7-1

constant monitoring of theis 1 pointtemperature on the upstream side

1

3

predictability is good

Dynamic

Decrease in

As the demister

Partial blockage due(a) Demister

Selected because the differential

Functionality is ensured by

Post-detection is possible by

Because item 7-1(Pretreatmen

boundarydifferential

deteriorates andto accumulation ofdifferential pressurepressure before and after theswitching between demisters

regular monitoring of the demisteris 1 point

pressure

the design value of

dust migrating from+ differential

demister increases due to partial

using 2 series of demisters

differential pressure and constant

betweenthe exhauster is not

the processing point

pressure between

inside andensured, theto the demister

inside and outside ofoutside of

exhaust airflow rate

the PCVdecreases and thedifferential pressure

the PCV

Direct(item 4)blockage of the demister, andbecause this trend is affected by(already studied)1

3of the exhaust fan, anddesign temperature

Demistert equipment)

An-Ki-38

1

exhauster, and because this trend

the rise in PCV
temperature due toairflow rate decreases due to

Because item 7-1

It is assumed that the

Selected because the exhaust

monitoring of the differential
3

pressure between inside andthe amount and particle size

outside of the PCV, and advance

distribution of inflowing dust.

detection is possible from signs of

①

1

3

3

the differential pressure between

between inside andinside and outside of the PCV.

outside of the PCV(b) Amount andFunctionality is ensured byContinuous monitoring isdecreases.

particle size

switching between demisters

required, but predictability is

distribution of dust atdemister inlet

Indirect(item 5)1

using 2 series of demisters

3

good.

Because item 7-1
is 1 point
13(already studied)©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-2: Risk assessment table for safety equipment (Detailed version) (19/48)
No.160■ Risk assessment table■ Score table for item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still underdevelopment[2 points] Countermeasures exist, but there are no trackrecords of application at the Fukushima Daiichi[1 point] Countermeasures exist, and have been applied at the
Fukushima Daiichi.

(gas phase confinement equipment)
Model ID
Process

Ko-3: Debris retrieval

Work

Sa-4

: Processing of debris■ Score table for item 7-2[4 points] Requires constant monitoring during task andpredictability is poor
[3 points] Requires constant monitoring during task but
predictability is good
[2 points] Requires regular monitoring and predictability is poor
[1 point] Requires regular monitoring and predictability is good

Important monitoring items■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is unknown[3 points] Countermeasures exist, but throughput decreases significantly due tosuspension of task
[2 points] Countermeasures exist, but throughput decreases due to workload
limitations[1 point] No impact on throughput, or when 7-1 is 1 point

Weighted evaluation of important monitoring items

Item 1

Item 2Item 3Item 4Item 5-1

Item 5-2

Item 6-1

Item 6-2

Item 6-3

Targetequipment

The functionthat thetarget is
responsibleforWork delay
factor (=error)

Direct causes of
error

Indirectcauses oferror

Reasons to be
selected

Detectionrequirements toavoid work delays

Directmonitoring/
Indirect
monitoring

Reason for selection of detection
requirements

Demister

Dynamic

Decrease in

As the demister

Partial damage due(a) Demister

Corrosion of dust accumulated in

Functionality is ensured by

Post-detection is possible by

Because item 7-1 is 1

(Pretreatmen

boundarydifferential

deteriorates andto corrosion of dust

differential pressure

the demister causes partial

switching filters through 2 series

constant monitoring of the dust

point

pressure

the design value of

migrating from the+ differential

Directdamage to the demister andof filters (already studied)concentration on the downstream

betweenthe exhauster is notprocessing point topressure between(item 4)increases the differential pressure

inside andensured, thethe demister

inside and outside of

before and after the demister.

outside of

exhaust airflow rate

the PCV

Selected because this trend is

the PCVdecreases and theAnalysis
numbert equipment)

An-Ki-39

differential

Same as(pH, chloride ion

inside and outside

concentration,of the PCV

chemicaldecreases.

composition) of dust flowing into

(item 5)the filter.

Item 7-2

Point

4

Effects on accurate and prompt
on-site response by workers

side of the filter, but predictability

Item 7-3

Point

Impact on throughput
due to error handling(Indirect causes)

1

Item 7-4(Evaluation
Results)
Indiv
idual

Point ofrepresentation4

is poorion concentration, chemical
Indirect

Presence or absence ofcountermeasures for disturbing
functions1chemical properties (pH, chloride

chemical properties

pressure between

Pointaffected by the amount and(b) (b) Amount andabove

Item 7-1

Functionality is ensured byContinuous monitoring is

Because item 7-1 is 1

switching filters through 2 seriesrequired, but predictability is

point

of filters (already studied)
1

4

poor.
4

1

4

composition) of dust
at demister inlet

Same asSame asSame as

above

above

above

Same as above

Same asAn-Ki-40

Partial damage due(a) Demister

Irradiation of dust accumulated in

Functionality is ensured by

Post-detection is possible byto irradiation of dust

differential pressure

the demister causes partial

switching filters through 2 series

constant monitoring of the dust

migrating from the+ differential

Directdamage to the demister andprocessing point topressure between(item 4)increases the differential pressure

the demister

inside and outside of

before and after the demister.

the PCV

Selected because this trend is(b) Amount andaffected by the amount andabove

nuclide compositionof dust at demister

inlet

Same asSame asSame as

above

above

above

Same as above

Indirect(item 5)1

4

side of the filter, but predictability

point
1

4

4
Functionality is ensured byContinuous monitoring isswitching filters through 2 series
1of filters (already studied)Because item 7-1 is 1

required, but predictability is
4

poor.

point
1

4

Partial blockage due(a) Demister

Selected because the differential

Functionality is ensured by

Post-detection is possible by

Because item 7-1 is 1

to adhesion ofdifferential pressurepressure before and after theswitching between demisters

regular monitoring of the

pointprocessing aid+ differential

demister increases due to partial

using 2 series of demisters

demister differential pressure andmigrating from thepressure between

blockage of the demister, and(already studied)

constant monitoring of theprocessing point to

inside and outside of

Directbecause this trend is affected by

the demister

the PCV(item 4)the amount of mist flowing into

1

3

the demister.
An-Ki-41

concentration on the downstream

is poornuclide composition of dust
flowing into the filter.

of filters (already studied)Because item 7-1 is 1

differential pressure between
inside and outside of the PCV,1

3

and advance detection is②

3

possible from signs of thedifferential pressure between
inside and outside of the PCV.
(b) Amount of mist atdemister inlet

Indirect(item 5)1

Functionality is ensured byContinuous monitoring isswitching between demisters

required, but predictability isusing 2 series of demisters

3

good.

Because item 7-1 is 1
point
1

3

(already studied)©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-2: Risk assessment table for safety equipment (Detailed version) (20/48)
No.161■ Risk assessment table(gas phase confinement equipment)
Model ID
Process

Ko-3: Debris retrieval

Work

Sa-4

: Processing of debris■ Score table for item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still underdevelopment[2 points] Countermeasures exist, but there are no trackrecords of application at the Fukushima Daiichi[1 point] Countermeasures exist, and have been appliedat the Fukushima Daiichi.

■ Score table for item 7-2[4 points] Requires constant monitoring during task andpredictability is poor
[3 points] Requires constant monitoring during task but
predictability is good
[2 points] Requires regular monitoring and predictability
is poor[1 point] Requires regular monitoring and predictability is
good

Important monitoring items

Weighted evaluation of important monitoring items

Item 1

Item 2Item 3Item 4Item 5-1

Item 5-2

Item 6-1

Item 6-2

Item 6-3

Targetequipment

The functionthat thetarget is
responsibleforWork delay
factor (=error)

Direct causes of
error

Indirectcauses oferror

Reasons tobe selected

Detectionrequirements toavoid work delays

Directmonitoring/I
ndirectmonitoring

Reason for selection of detection
requirements

Partial(a) Demister

blockagedifferential pressure

due to+ differential

Analysis
numberAs the demister

Demister(Pretreatment equipment)

Dynamic
boundary

An-Ki-42

Decrease indeteriorates anddifferential

the design value ofpressure

the exhauster is not

betweenensured, theinside andexhaust airflow rate

outside of

decreases and thethe PCVdifferential pressure③

between inside andPoint

Selected because the differential

pressure between

anti-

inside and outsidepressure before and after the demister

dispersionof the PCV

increases due to partial blockage of the(item 4)

1

Drybackwash
An-Ki-43

filter(Pretreatmen

differential

Dynamic
boundaryt equipment)pressure
betweeninside andoutside of

the PCV

Same asabove

An-Ki-44

Same asabove

Same as
above

Point

Effects on accurate and prompt on-site
response by workers

Functionality is ensured bypressure and constant monitoring of theswitching between demisters

differential pressure between inside andusing 2 series of demisters

3(already studied)outside of the PCV, and advance detection

demister, and because this trend ispressure between inside and outside of the

migratingaffected by the amount of mist flowing

PCV.

point to theinto the demister.
(b) Amount of mist

Indirectat demister inlet(item 5)switching between demisters

using 2 series of demisters

Continuous monitoring is required, but
predictability is good.

(a) Differential

Partial blockage of the dry backwash

Functionality is ensured byFilter clogging is due to daily accumulation,

blockagepressure of dry

filter increases the differential pressure

switching filters through 2

and predictability is good.

deteriorates anddue tobackwash filter +Directbefore and after the dry backwash filter.

the design value ofaccumulatio

differential pressure(item 4)

Selected because this trend is affected

the exhauster is notn of dust

between inside andby the amount and particle size

migratingoutside of the PCV

distribution of dust flowing into the dry

from the(b) Amount andbackwash filter.

decreases and theprocessing

particle size

differential pressure

point to the

distribution of dust

Indirect

between inside anddry

at dry backwash(item 5)outside of the PCV

backwashfilter inlet

decreases.

filterSame as above

Same
above

as

1

series of filters (alreadystudied)3

1

item 7-1 is

1 point

3

series of filters (already1

studied)to corrosion

backwash filter +of dustdifferential pressure(item 4)

item 7-1 is1

migratingbetween inside andbackwash filter causes partial damage tofrom theoutside of the PCV

filter elements and decreases the1studied)1

3

1 point3

1

3

Becauseitem 7-1 is

Post-detection is possible by constantseries of filters (alreadyCorrosion of dust accumulated in the dry

1 point

item 7-1 isswitching filters through 2
Direct1

BecauseBecauseFunctionality is ensured byfilter3

predictability is good.

pressure of dry

backwash1

Continuous monitoring is required, but(a) Differential

dry

1 point

switching filters through 2

damage due

point to the

Point
of
representationitem 7-1 isFunctionality is ensured byPartialprocessing

Individual(already studied)

Partial①

Impact on
throughput
due to error
handling(Indirect
causes)BecauseItem 7-4(Evaluation
Results)

Because3

backwash filter

exhaust airflow rate

Point

Functionality is ensured by1

As the dry

ensured, theItem 7-3

is possible from signs of the differential

agent

demisterDecrease in

Presence or absence ofcountermeasures for disturbing
functions

Item 7-2

monitoring of the demister differential
Directadhesion ofprocessing

decreases.

Item 7-1

Post-detection is possible by regularfrom theoutside of the PCV■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is unknown[3 points] Countermeasures exist, but throughput decreases significantly due
to suspension of task
[2 points] Countermeasures exist, but throughput decreases due to workload
limitations[1 point] No impact on throughput, or when 7-1 is 1 point4

monitoring of the dust concentration on thedownstream side of the filter, but

1 point
1

4

predictability is poordifferential pressure before and after the(b) Amount anddry backwash filter. Selected because

Functionality is ensured byContinuous monitoring is required, but

Becausechemical properties

this trend is affected by the amount andswitching filters through 2

predictability is poor.

item 7-1 is(pH, chloride ion

series of filters (alreadychemical properties (pH, chloride ion

concentration,

Indirectconcentration, chemical composition) of

chemical(item 5)dust flowing into the dry backwash filter.

1

studied)4

1 point
4

1

4

composition) ofdust at dry
backwash filter inlet©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-2: Risk assessment table for safety equipment (Detailed version) (21/48)
No.162■ Risk assessment table(gas phase confinement equipment)■ Score table for item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still underdevelopment[2 points] Countermeasures exist, but there are no trackrecords of application at the Fukushima Daiichi[1 point] Countermeasures exist, and have been appliedat the Fukushima Daiichi.

Model ID
Process

Ko-3: Debris retrieval

Work

Sa-4

: Processing of debris■ Score table for item 7-2[4 points] Requires constant monitoring during task andpredictability is poor
[3 points] Requires constant monitoring during task but
predictability is good
[2 points] Requires regular monitoring and predictability
is poor[1 point] Requires regular monitoring and predictability is
good

Important monitoring items■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is unknown[3 points] Countermeasures exist, but throughput decreases significantly due
to suspension of task
[2 points] Countermeasures exist, but throughput decreases due to workload
limitations[1 point] No impact on throughput, or when 7-1 is 1 point

Weighted evaluation of important monitoring items

Impact on
throughput due
to errorhandling(Indirect
causes)Individual

Item 3Item 4Item 5-1

Item 5-2

Item 6-1

Item 6-2

Item 6-3

Targetequipment

The functionthat thetarget is
responsibleforWork delay
factor (=error)

Direct causes of
error

Indirectcauses oferror

Reasons to be
selected

Detectionrequirements toavoid work delays

Directmonitoring/
Indirect
monitoring

Reason for selection of detection
requirements

Dry

Dynamic

Decrease in

As the dry

Partial damage due(a) Differential

Irradiation of dust accumulated in

Functionality is ensured by

Post-detection is possible by

Because item

backwashboundarydifferential

backwash filter

to irradiation of dust

pressure of dry

the dry backwash filter causes

switching filters through 2 series

constant monitoring of the dust

7-1 is 1 point

filterpressure

deteriorates andmigrating from the

backwash filter +partial damage to filter elementsof filters (already studied)concentration on the downstream(Pretreatme

betweenthe design value ofprocessing point todifferential pressurent

inside andthe exhauster isthe dry backwash

between inside andpressure before and after the dry

equipment)

outside of

not ensured, thefilteroutside of the PCV

backwash filter. Selected

the PCVexhaust airflow rate

An-Ki-45

item 4)①

and increases the differential

Point

Presence or absence ofcountermeasures for disturbing
functions

1

Item 7-2

Item 7-4(Evaluation Results)

Item 2

DirectItem 7-1

Item 7-3

Item 1Analysis
numberPoint

4

Effects on accurate and prompt
on-site response by workers

side of the filter, but predictability

Point

1

4

is poorbecause this trend is affected by(b) Amount anddecreases and theof dust at dry

pressure between

backwash filter inlet

inside and outside

4
Functionality is ensured by

the amount and nuclide

nuclide compositiondifferential

the dry backwash filter.

(item 5)

Continuous monitoring isswitching filters through 2 series

composition of dust flowing into
Indirect

Point ofrepresentationrequired, but predictability isof filters (already studied)1

Because item
7-1 is 1 point

poor.
4

1

4

of the PCV
decreases.

Same asSame asSame as

above

above

above

Same as above②

An-Ki-46

Partial blockage due(a) Differential

Selected because the differential

Functionality is ensured byFilter clogging is due to daily

to adhesion ofpressure of dry

pressure before and after the dry

installing a demister and electric

accumulation, and predictability

processing aid

backwash filter +Directbackwash filter increases due to(item 4)

partial blockage of the dry

migrating from thedifferential pressure

processing point tobetween inside andbackwash filter, and because thisthe dry backwash

outside of the PCV

trend is affected by the amount offilter(b) Amount of mist

mist flowing into the dryat dry backwash

Indirectfilter inlet(item 5)heater at the first-stage filter1(already studied)Because item
7-1 is 1 pointis good.
1113Functionality is ensured bybackwash filter.
1

installing a demister and electricheater at the first-stage filter

Continuous monitoring is3

required, but predictability is
good.

Because item
17-1 is 1 point3(already studied)

An-Ki-47

Same asSame asSame as

above

above

above

Same as above③

Blockage due to(a) Differential

Selected because the differential

Functionality is ensured byFilter clogging is due to daily

Because item

adhesion of anti-pressure of dry

pressure before and after the dry

installing a demister and electric

accumulation, and predictability

7-1 is 1 point

dispersion agent

backwash filter +Directbackwash filter increases due toheater at the first-stage filter

is good.

migrating from thedifferential pressure(item 4)

partial blockage of the dry

processing point tobetween inside andbackwash filter, and because thisthe dry backwash

outside of the PCV

trend is affected by the amount offilter(b) Amount of mist

inflowing mist.

at dry backwash

Indirectfilter inlet(item 5)1(already studied)

1

1

1

3
Functionality is ensured by1

installing a demister and electricheater at the first-stage filter

Continuous monitoring is3

required, but predictability is
good.

Because item
17-1 is 1 point3(already studied)©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-2: Risk assessment table for safety equipment (Detailed version) (22/48)
No.163■ Risk assessment table(gas phase confinement equipment)■ Score table for item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still underdevelopment[2 points] Countermeasures exist, but there are no trackrecords of application at the Fukushima Daiichi[1 point] Countermeasures exist, and have been appliedat the Fukushima Daiichi.

Model ID

Process

Ko-3: Debris retrieval

Work

Sa-4

: Processing of debris■ Score table for item 7-2[4 points] Requires constant monitoring during task andpredictability is poor
[3 points] Requires constant monitoring during task but
predictability is good
[2 points] Requires regular monitoring and predictability
is poor[1 point] Requires regular monitoring and predictability is
good

Important monitoring items

Weighted evaluation of important monitoring items

Item 1

Item 2Item 3Item 4Item 5-1

Item 5-2

Item 6-1

Item 6-2

Item 6-3

Targetequipment

The functionthat thetarget is
responsibleforWork delay
factor (=error)

Direct causes of
error

Indirectcauses oferror

Reasons to be
selected

Detectionrequirements toavoid work delays

Directmonitoring/
Indirect
monitoring

Reason for selection of detection
requirements

HEPA filter

Discharge

Increase in

As the HEPA filter

Partial blockage of(a) HEPA filter

control

dust

deteriorates andthe filter element due

differential pressure

concentratio

the design value ofto accumulation ofn on

the filter efficiency

dust migrating fromdownstream

is not ensured, theside ofdust concentration

HEPA filter

inside the PCV

distribution at theincreases.

HEPA filter inlet

Analysis
number

An-Ki-48

Same asSame asSame as

above

above

above

①

Same as above

Same asAn-Ki-49

Functionality is ensured byFilter clogging is due to daily

differential pressure increases

switching filters through 2 series

accumulation, so predictability is(item 4)due to partial blockage caused by

An-Ki-50

Same asaboveof filters (already studied)

1

good

Impact on
throughput due toerror handling(Indirect causes)1

is 1 point

filter, and because this trend is

Functionality is ensured byContinuous monitoring is

Because item 7-1

affected by the amount andswitching filters through 2 seriesrequired, but predictability is

is 1 point

Indirect(item 5)

particle size distribution of

Point ofrepresent
ation

1

1

of filters (already studied)

3

good.

1

3

3

inflowing dust.

Partial damage(a) HEPA filter

Deterioration of filter elements

Functionality is ensured by

Post-detection is possible by

Because item 7-1

caused by the

upstream/downstrea

due to dust accumulated in theswitching filters through 2 series

constant monitoring of the dustis 1 point

deterioration of filterm dust concentration

HEPA filter causes partialof filters (already studied)concentration on the downstream

elements due to dust

ratio

Direct(item 4)

damage to filter elements andmigrating from thedecreases the ratio of dust

processing point toconcentration between thethe HEPA filter

Individual

Because item 7-1

particle size

1

Selected because this trend isaffected by the amount andIndirect

chemical properties (pH, chloride(item 5)ion concentration, chemical

4side of the filter, but predictability

14

is poorupstream and downstream sides.

(b) Amount andFunctionality is ensured byContinuous monitoring is

Because item 7-1

switching filters through 2 seriesrequired, but predictability is

is 1 pointof filters (already studied)
1

4

poor.
4

1

4

composition) of dust flowing into
the filter.

at HEPA filter inlet

above

1

Point

(b) Dust amount andcomposition) of dust

above

Effects on accurate and prompt
on-site response by workers

to the HEPA filter

chemical

above

Point

Item 7-4(Evaluation
Results)

Item 7-3

dust accumulation in the HEPA

concentration,

Same as above

Presence or absence ofcountermeasures for disturbing
functions

Selected because the filter(pH, chloride ion

Same as

Point

Item 7-2

Directchemical properties

Same as

Item 7-1

the processing point

above

Same as■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is unknown[3 points] Countermeasures exist, but throughput decreases significantly due
to suspension of task
[2 points] Countermeasures exist, but throughput decreases due to workload
limitations[1 point] No impact on throughput, or when 7-1 is 1 point

Partial damage to(a) HEPA filter

Partial damage to filter elements

Functionality is ensured by

Post-detection is possible byfilter elements due to

upstream/downstrea

due to irradiation of dust

switching filters through 2 series

constant monitoring of the dust

irradiation of dust

m dust concentration

Directaccumulated in the HEPA filter

migrating from theratio(item 4)decreases the ratio of dust

side of the filter, but predictability

processing point toconcentration between theis poorthe HEPA filter

upstream and downstream sides.
(b) Amount and

1of dust at HEPA filter

Indirect

inlet(item 5)concentration on the downstream

is 1 point
1

4

4
Continuous monitoring isswitching filters through 2 seriesaffected by the amount andnuclide composition of inflowing

4

Functionality is ensured by

Selected because this trend is

nuclide compositionof filters (already studied)Because item 7-1

1

of filters (already studied)Because item 7-1

required, but predictability is
4

poor.

is 1 point
1

4

dust.

©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-2: Risk assessment table for safety equipment (Detailed version) (23/48)
No.164■ Risk assessment table(gas phase confinement equipment)
Model ID
Process

Ko-3: Debris retrieval

Work

Sa-4

: Processing of debris■ Score table for item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still underdevelopment[2 points] Countermeasures exist, but there are no trackrecords of application at the Fukushima Daiichi[1 point] Countermeasures exist, and have been appliedat the Fukushima Daiichi.

■ Score table for item 7-2[4 points] Requires constant monitoring during task andpredictability is poor
[3 points] Requires constant monitoring during task but
predictability is good
[2 points] Requires regular monitoring and predictability
is poor[1 point] Requires regular monitoring and predictability is
good

Important monitoring items■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is unknown[3 points] Countermeasures exist, but throughput decreases significantly due
to suspension of task
[2 points] Countermeasures exist, but throughput decreases due to workload
limitations[1 point] No impact on throughput, or when 7-1 is 1 point

Weighted evaluation of important monitoring items

Item 1

Item 2Item 3Item 4Item 5-1

Item 5-2

Item 6-1

Item 6-2

Item 6-3

Targetequipment

The functionthat thetarget is
responsibleforWork delay factor(= error)

Direct causesof error

Indirectcauses oferror

Reasons to be
selected

Detectionrequirements toavoid work delays

Directmonitoring/
Indirect
monitoring

Reason for selection of detection
requirements

HEPA filter

Discharge

Increase in dust

As the HEPA

Partial blockage due(a) HEPA filter

Selected because the HEPA filter

Functionality is ensured byFilter clogging is due to daily

controlconcentration on

filterto adhesion ofdifferential pressure

differential pressure increases

installing a demister and electric

accumulation, so predictability is

downstream side

deteriorates

processing aid

Directdue to partial blockage causedof HEPA filter

and the design

migrating from the(item 4)by mist accumulation in the

Analysis
numbervalue of theAn-Ki-51

filter efficiency

processing point to②

the HEPA filter

is not ensured,

Item 7-1

Point

1

Presence or absence ofcountermeasures for disturbing
functionsheater at the first-stage filter

Item 7-2

Point

1

Effects on accurate and prompt
on-site response by workers

good

Item 7-3

Point

Impact on throughput
due to error handling(Indirect causes)

Item 7-4(Evaluation
Results)

Indiv
idual

Point ofrepresentationBecause item 7-1 is 1
point
1

1

(already studied)

HEPA filter, and because thistrend is affected by the amount of(b) Amount of mist

mist inflow due to the processing

at HEPA filter inlet

the dust

Indirectconcentration(item 5)aid.
1Functionality is ensured byContinuous monitoring is

Because item 7-1 is 1

installing a demister and electric

required, but predictability is

pointheater at the first-stage filter

3

good.

1

3

3

(already studied)inside the PCV
increases.
Performance(a) Relative humidity

Selected because the relative

degradation of theat HEPA filter inlet

humidity of gas flowing into the

HEPA filter caused
Same asSame as

above

above

Same as above

Same asby relative humidity

above

at HEPA filter inlet,

Direct(item 4)above

assumption, as aresult of debris
retrieval operations

deviate from the design1

installing a demister and electricheater at the first-stage filter

4

An-Ki-53

Same as

above

above

Same as above

sprayed atprocessing point(a) HEPA filter
differential pressure

above

migrating from the③

processing point to
the HEPA filter

4

predictability is poor

point

Functionality is ensured byIndirect1(item 5)4Because item 7-1 is 1

the processing point.

processing aid (mist)

to adhesion of antidispersion agent

1

processing aid (mist) sprayed at(b) Amount ofPartial blockage due
Same astemperature differential before
and after the electric heater, but(already studied)installing a demister and electricheater at the first-stage filter

Continuous monitoring is3

required, but predictability is

Selected because the HEPA filter

Functionality is ensured byFilter clogging is due to daily

Directdifferential pressure increases

switching filters through 2 series

accumulation, so predictability is(item 4)due to mist accumulation, and1of filters (already studied)

1

3

good.

(already studied)

Same aspoint

constant monitoring of theis affected by the amount ofcondition, exceeding
the design

HEPA filter was verified tocondition, and because this trend

which is a design
Same asAn-Ki-52

Because item 7-1 is 1

Post-detection is possible by

Functionality is ensured by

1

good

Because item 7-1 is 1
point
1

1

because this trend is affected by
the amount of mist inflow due to(b) Amount of mist
at HEPA filter inlet

the anti-dispersion agent.
Indirect(item 5)1

Functionality is ensured byContinuous monitoring is

Because item 7-1 is 1

switching filters through 2 seriesrequired, but predictability is

point

of filters (already studied)

3

good.

1

3

3

©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-2: Risk assessment table for safety equipment (Detailed version) (24/48)
No.165■ Risk assessment table(gas phase confinement equipment)
Model ID
Process

Ko-3: Debris retrieval

Work

Sa-4

: Processing of debris■ Score table for item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still underdevelopment[2 points] Countermeasures exist, but there are no trackrecords of application at the Fukushima Daiichi[1 point] Countermeasures exist, and have been applied at the
Fukushima Daiichi.

■ Score table for item 7-2[4 points] Requires constant monitoring during task
and predictability is poor
[3 points] Requires constant monitoring during task but
predictability is good
[2 points] Requires regular monitoring andpredictability is poor
[1 point] Requires regular monitoring and predictability
is good

Important monitoring items■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is unknown[3 points] Countermeasures exist, but throughput decreases significantly
due to suspension of task
[2 points] Countermeasures exist, but throughput decreases due toworkload limitations[1 point] No impact on throughput, or when 7-1 is 1 point

Weighted evaluation of important monitoring items

Item 1

Item 2Item 3Item 4Item 5-1

Item 5-2

Item 6-1

Item 6-2

Item 6-3

Targetequipment

The functionthat thetarget is
responsibleforWork delay factor(= error)

Direct causesof error

Indirectcauses oferror

Reasons to be
selected

Detectionrequirements toavoid work delays

Directmonitoring/
Indirect
monitoring

Reason for selection of detection
requirements

HEPA filter

Discharge

Increase in dust

As the HEPA

Performance(a) Relative humidity

Selected because the relative

Functionality is ensured by

Post-detection is possible bycontrolconcentration on

filterdegradation of theat HEPA filter inlet

humidity of gas flowing into theswitching filters through 2 series

constant monitoring of thedownstream side

deteriorates

HEPA filter caused

DirectHEPA filter was verified toof HEPA filter

and theby relative humidity(item 4)

deviate from the design

and after the electric heater, but

design value

at HEPA filter inlet,condition, and because this trend

predictability is poorof the filter

which is a design

is affected by the amount of anti-

Analysis
number

An-Ki-54

efficiency is③

not ensured,condition, exceeding
the design

the dust

assumption, as aconcentration

result of debris

inside theretrieval operations(b) Amount of anti-

Item 7-1

Point1

dispersion agent (mist) sprayeddispersion agent

at the processing point.

(mist) sprayed atprocessing point

Indirect

Presence or absence ofcountermeasures for disturbing
functionsof filters (already studied)

Point

4

Effects on accurate and prompt
on-site response by workers

temperature differential before

Point

Impact on
throughput due toerror handling(Indirect causes)

Individual

Point ofrepresent
ation

Because item 7-1
is 1 point
1

4

Continuous monitoring is

Because item 7-1

switching filters through 2 seriesrequired, but predictability is

is 1 pointof filters (already studied)

good.
3

Item 7-4(Evaluation
Results)

Item 7-3

Functionality is ensured by1(item 5)Item 7-2

1

4

3

PCV
increases.
(a) HEPA filter
Partial blockage ofSame asSame as

above

above

Same as above

Same asthe HEPA filter

above

elements due to④

An-Ki-55

accumulation ofabrasives migratingfrom the processing

point to the HEPA

An-Ki-56

Same as

above

above

Same as above

Accumulation of abrasives
Directflowing into the HEPA filter(item 4)

partially clogs the HEPA filter

Functionality is ensured by1

switching filters through 2 series

Filter clogging is due to daily
1accumulation, so predictability isof filters (already studied)good

differential pressure. Selected

Functionality is ensured byContinuous monitoring is

Because item 7-1

particle size

because this trend is affected byswitching filters through 2 seriesrequired, but predictability is

is 1 point

Indirectthe amount of abrasives flowingof filters (already studied)

good.

(item 5)

into the HEPA filter due to

distribution ofabrasives at HEPA

1

3

1

Performance(a) Relative humidity

Selected because the relative

Functionality is ensured by

Post-detection is possible bydegradation of theat HEPA filter inlet

humidity at the HEPA filter inlet

switching filters through 2 series

constant monitoring of theSame asHEPA filter caused

Directwas verified to deviate from theabove

by the design(item 4)design condition, and because

and after the electric heater, butcondition of relative

this trend is affected by thepredictability is poor

humidity at theamount of heat input at the

HEPA filter inlet

above

exceeding theassumed designis 1 point1

and increases the HEPA filter

processing.

Same as

Because item 7-1
1(b) Amount andfilter inlet

filterSame asdifferential pressure(b) Amount of heat1

of filters (already studied)4

temperature differential before

3

Because item 7-1
is 1 point

1

4

Functionality is ensured byContinuous monitoring is

Because item 7-1

input at processing

switching filters through 2 seriesrequired, but predictability is

is 1 point

point

of filters (already studied)good.

processing point.

condition with

Indirect

evaporation of D/W(item 5)

1

3

3

1

4

3

stagnant water as aresult of heat input
during processing©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-2: Risk assessment table for safety equipment (Detailed version) (25/48)
No.166■ Risk assessment table■ Score table for item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still underdevelopment[2 points] Countermeasures exist, but there are no trackrecords of application at the Fukushima Daiichi[1 point] Countermeasures exist, and have been applied at the
Fukushima Daiichi.

(gas phase confinement equipment)
Model ID
Process

Ko-3: Debris retrieval

Work

Sa-4

: Processing of debris■ Score table for item 7-2[4 points] Requires constant monitoring during task
and predictability is poor
[3 points] Requires constant monitoring during task
but predictability is good
[2 points] Requires regular monitoring andpredictability is poor
[1 point] Requires regular monitoring andpredictability is good

Important monitoring items■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is unknown[3 points] Countermeasures exist, but throughput decreases significantly
due to suspension of task
[2 points] Countermeasures exist, but throughput decreases due toworkload limitations[1 point] No impact on throughput, or when 7-1 is 1 point

Weighted evaluation of important monitoring items

Item 1

Item 2Item 3Item 4Item 5-1

Item 5-2

Item 6-1

Item 6-2

Item 6-3

Targetequipment

The functionthat thetarget is
responsibleforWork delay factor(= error)

Direct causes of
error

Indirectcauses oferror

Reasons to be
selected

Detectionrequirements toavoid work delays

Directmonitoring/
Indirect
monitoring

Reason for selection of
detection requirements

Electric

Discharge

Increase in dust

Due to failure of

Performance(a) Temperature

Selected because theFunctionality is ensured by

Post-detection is possible by

Because item 7-1 is 1

heatercontrolconcentration on

the electric heater,

degradation of thedifferential before

temperature differential

switching between heaters

constant monitoring of thepointelectric heaterand after the

before and after theusing 2 series of electric

temperature differential before

caused by irradiationelectric heater

Analysis
number(Pretreatme

downstream sidentof the filter

equipment)

the relative
humidity does notdecrease and thedesign condition ofof dust migrating

the filter (relativefrom the processing

humidity of 99% orpoint to the electricless) is not

An-Ki-57①

heaterensured, resulting

Directelectric heater decreases(item 4)due to performance

Item 7-1

Point

1

Presence or absence ofcountermeasures for disturbing
functionsheaters (already studied)

Item 7-2

Point

4

Effects on accurate and prompt
on-site response by workers

and after the electric heater, but

Item 7-3

Point

Impact on throughput
due to error handling(Indirect causes)

1

Item 7-4(Evaluation
Results)
Indiv
idual

Point ofrepresentation4

predictability is poor

degradation of the electricheater, and because thistrend is affected by the(b) Amount andin the deterioration

nuclideand damage to thecomposition offilter and an

dust at electricincrease in theheater inlet

amount and nuclide
composition of dust
Indirectflowing into the electric(item 5)heater.

1

Functionality is ensured byContinuous monitoring is

Because item 7-1 is 1

switching between heaters

required, but predictability is

pointusing 2 series of electricpoor.

heaters (already studied)

4

1

4

4

dust concentrationon the downstreamside of the filter.

Same asSame as

above

above

Same as above

Same as above

Performance(a) Temperature

Selected because theFunctionality is ensured by

Post-detection is possible bydegradation of thedifferential before

temperature differential

switching between heaters

constant monitoring of theelectric heaterand after the

Directbefore and after thecaused by adhesion

electric heater(item 4)

electric heater decreasesof processing aid②

An-Ki-58

migrating from theprocessing point to
the electric heater

1

using 2 series of electric4heaters (already studied)

inletheater, and because thisIndirect(item 5)trend is affected by theamount of mist flowing

4

predictability is poor

degradation of the electricat electric heater

point
1

and after the electric heater, but

due to performance(b) Amount of mist

temperature differential before

Because item 7-1 is 1

1

Functionality is ensured byContinuous monitoring is

Because item 7-1 is 1

switching between heaters

required, but predictability is

pointusing 2 series of electric

3

good.

1

4

3

heaters (already studied)into the electric heater due
to the processing aid.

Same asSame as

above

above

Same as above

Same as above

Performance(a) Temperature

Selected because theFunctionality is ensured by

Post-detection is possible bydegradation of thedifferential before

temperature differential

switching between heaters

constant monitoring of theelectric heaterand after the

Directbefore and after thecaused by adhesion

electric heater(item 4)

electric heater decreasesof anti-dispersion
agent migrating from
An-Ki-59③

the processing point
to the electric heater

1

using 2 series of electric4heaters (already studied)

inletheater, and because thistrend is affected by the
Indirectamount of mist flowing(item 5)

into the electric heater due

4predictability is poor

degradation of the electricat electric heater

point
1

and after the electric heater, but

due to performance(b) Amount of mist

temperature differential before

Because item 7-1 is 1

1

Functionality is ensured byContinuous monitoring is

Because item 7-1 is 1

switching between heaters

required, but predictability is

pointusing 2 series of electric

good.

heaters (already studied)

3

1

4

3

to the anti-dispersion
agent.

©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-2: Risk assessment table for safety equipment (Detailed version) (26/48)
No.167■ Risk assessment table(gas phase confinement equipment)
Model ID
Process

Ko-3: Debris retrieval

Work

Sa-4

: Processing of debris■ Score table for item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still underdevelopment[2 points] Countermeasures exist, but there are no trackrecords of application at the Fukushima Daiichi[1 point] Countermeasures exist, and have been appliedat the Fukushima Daiichi.

■ Score table for item 7-2[4 points] Requires constant monitoring during task andpredictability is poor
[3 points] Requires constant monitoring during task but
predictability is good
[2 points] Requires regular monitoring and predictability
is poor[1 point] Requires regular monitoring and predictability is
good

Important monitoring items

Weighted evaluation of important monitoring items

Impact on
throughput due toerror handling(Indirect causes)

IndividualItem 3Item 4Item 5-1

Item 5-2

Item 6-1

Item 6-2

Item 6-3

Targetequipment

Thefunctionthat thetarget is
responsible
for

Work
delay
factor(= error)

Direct causes of
error

Indirectcausesof error

Reasons tobe selected

Detectionrequirements toavoid work
delaysDirectmonitoring/
Indirect
monitoring

Reason for selectionof detection
requirements

Electric

Discharge

Increase

Due to failure

Performanc(a)Selected because

Functionality is

Post-detection is

Because item 7-

heatercontrolin dustof the electriceTemperature

the temperatureensured by switchingpossible by constant

1 is 1 point(Pretreconcentra

heater, thedegradationdifferential

differential before

between heaters using

monitoring of theatmenttion onrelativeof thebefore andequipmdownstre

humidity does

electric

after theent)

am sidenot decrease

heaterelectric heaterof theand the design

caused byfiltercondition of thethe rise in(b) Amount ofelectric heater, andFunctionality is

Continuous monitoring

Because item 7-

filter (relative

PCV

heat input at

because this trend isensured by switchingis required, but

1 is 1 point

humidity oftemperatureprocessing

affected by the

between heaters using

predictability is good.

due to heatpoint

99% or less) is
not ensured,
resulting in the④

Directand after the electric

Point

1

Presence or absence ofcountermeasures for
disturbing functions

2 series of electric

Item 7-2

Item 7-4(Evaluation Results)

Item 2(item 4)Item 7-1

Item 7-3

Item 1Analysis
number

An-Ki-60■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is unknown[3 points] Countermeasures exist, but throughput decreases significantly due
to suspension of task
[2 points] Countermeasures exist, but throughput decreases due to workload
limitations[1 point] No impact on throughput, or when 7-1 is 1 point

Point

4

temperature differential

heater decreases

heaters (alreadybefore and after thedue to performancestudied)electric heater, but

degradation of the

Point

1

Point ofrepresent
ation

4

predictability is poor

amount of heat input

2 series of electric

input during

at the processing

heaters (alreadyprocessing

point which raises

studied)deterioration

Effects on accurate andprompt on-site response
by workers

4

the temperature ofand damage to

Indirectthe filter and an(item 5)inflowing gas.

1

3

1

3

increase in the
dust
concentrationon thedownstreamside of thefilter.

©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-2: Risk assessment table for safety equipment (Detailed version) (27/48)■ Risk assessment table(liquid phase confinement equipment)
Model ID
Process

Ko-3: Debris retrieval

Work

Sa-4

: Processing of debris

No.168■ Score table for item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still underdevelopment[2 points] Countermeasures exist, but there are no trackrecords of application at the Fukushima Daiichi[1 point] Countermeasures exist, and have been appliedat the Fukushima Daiichi.

■ Score table for item 7-2[4 points] Requires constant monitoring during task andpredictability is poor
[3 points] Requires constant monitoring during task but
predictability is good
[2 points] Requires regular monitoring and predictability
is poor[1 point] Requires regular monitoring and predictability is
good

Important monitoring items
Item 2Item 3

Targetequipment

The functionthat thetarget is
responsibleforWork delay
factor(= error)

D/W

Dynamic

Rise in D/W

Due toPartial blockage of(a) D/W stagnant

Selected because theSupported by multiplexing andAlthough constantBecause item 7-1 isstagnant

boundary

water level

deterioration

the pump due towater transfer pump

pump flow rate decreases

sacrificial anodes. In addition, themonitoring is required,1 point

waterof the D/Wdust contamination

flow rate

Directdue to partial blockage

effect of short term functional

detectability is good.

transferstagnant

migrating from the(item 4)caused by dust

pump

water

processing point totransferthe D/W stagnant

pump, thewater transfer(b) Chemical

pump, and because thisSupported by multiplexing andConstant monitoring is

Because item 7-1 isdesign value

pumpproperties (pH,trend is affected by thesacrificial anodes. In addition, therequired because the

1 point

chloride ion

amount and particle size

effect of short term functional

equipment is for D/Wflow rate isconcentration,

distribution of dust in thedeterioration or shutdown iswater level management

not ensured,chemicalIndirecttransferring liquid flowing

resulting incomposition) of(item 5)

into the torus room

the D/Wtransferring liquid

stagnant water transfer

water levelflowing into D/Wpump.

to increasestagnant water

An-Eki-1

Directcauses oferror

for the pump

Item 5-1

Indirectcauses oferror

Item 5-2

Weighted evaluation of important monitoring items

Item 1Analysis
numberItem 4■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is unknown[3 points] Countermeasures exist, but throughput decreases significantly due
to suspension of task
[2 points] Countermeasures exist, but throughput decreases due to workload
limitations[1 point] No impact on throughput, or when 7-1 is 1 point

Reasons to be
selected①

Item 6-1

Detectionrequirements toavoid work

Item 6-2
Directmonitoring/I
ndirectmonitoring

Item 6-3

Reason for selection of
detection requirements

Item 7-1

Point1

contamination in the D/WPresence or absence ofcountermeasures for disturbing
functionsdeterioration or shutdown is

Item 7-2

Point

Effects on accurate andprompt on-site response
by workers

3

Item 7-3

Point

Impact on
throughput due toerror handling(Indirect causes)

1

Item 7-4 (Evaluation
results)

Individual

Point ofrepresentat
ion

3

extremely small

stagnant water transfer

1

extremely small

4

related to confinement, but
predictability is poor.

1

4

4

transfer pumpSame asSame asSame asSame as

above

above

above

above

Partial damage(a) D/W stagnant

due to corrosion

water transfer pumpcaused byflow rate

potential

Direct(item 4)difference

An-Eki-2

Same asabove

Selected because theSupported by multiplexing andAlthough constantpump flow rate decreases

sacrificial anodes. In addition, themonitoring is required,

due to partial damage to1effect of short term functional

the D/W stagnant water

deterioration or shutdown is3

detectability is good.

Because item 7-1 is
1 point
13transfer pump, andextremely small

resulting from(b) Amount, particle

because this trend is

Supported by multiplexing andConstant monitoring is

Because item 7-1 isaccumulation ofsize distribution, andaffected by the amountsacrificial anodes. In addition, therequired because the

1 point

dust migrating

particle density ofand particle size

effect of short term functional

equipment is for D/Wfrom thedust in transferring

Indirect

distribution of dust in theprocessing point toliquid flowing into

(item 5)transferring liquid flowing

the D/W stagnant

D/W stagnant water

into the D/W stagnant

water transfer

transfer pumpwater transfer pump.

deterioration or shutdown is1

extremely small

4water level management
4

related to confinement, but

1

4

predictability is poor.

pump©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-2: Risk assessment table for safety equipment (Detailed version) (28/48)
No.169■ Risk assessment table(liquid phase confinement equipment)
Model ID
Process

Ko-3: Debris retrieval

Work

Sa-4

: Processing of debris■ Score table for item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still underdevelopment[2 points] Countermeasures exist, but there are no trackrecords of application at the Fukushima Daiichi[1 point] Countermeasures exist, and have been appliedat the Fukushima Daiichi.

■ Score table for item 7-2[4 points] Requires constant monitoring during task andpredictability is poor
[3 points] Requires constant monitoring during task but
predictability is good
[2 points] Requires regular monitoring and predictability
is poor[1 point] Requires regular monitoring and predictability is
good

Important monitoring items
Item 5-1

Item 2Item 3Item 4

Targetequipment

The functionthat thetarget is
responsibleforWork delay
factor(= error)

Direct causesof error

D/W

Dynamic

Rise in D/W

Due toPartial damage due(a) D/W stagnant

stagnant

boundary

water level

deterioration of

to corrosion of metalwater transfer pumpwater

the D/W

components such as

flow ratetransferstagnant water

impellers caused bypumptransfer pump,

Indirectcauses oferror

Reasons to be
selectedSame as

above

above

above

Item 6-3

Directmonitoring/
Indirect
monitoring

Reason for selection of detection
requirements

Direct(item 4)Item 7-1

Point

Presence or absence ofcountermeasures for disturbing
functions

Item 7-2

Point

Effects on accurate and prompt
on-site response by workers

Selected because the pump flow

Supported by multiplexing. In

Although constant monitoring israte decreases due to partial

addition, the effect of short term

required, detectability is good.

damage to the D/W stagnant

1water transfer pump, andfunctional deterioration or

3

Item 7-3

Point

Impact on throughput
due to error handling(Indirect causes)

point
1

3

shutdown is extremely small

because this trend is affected by
the chemical properties (pH,Supported by multiplexing. In

Constant monitoring is required

Because item 7-1 is 1

transferring liquidsize distribution, andchloride ion concentration,

addition, the effect of short term

because the equipment is forpoint

pump flow ratemigrating from theparticle density ofchemical composition) offunctional deterioration or

D/W room water levelis not ensured,

processing point todust in transferring

resulting in thethe D/W stagnant

liquid flowing into

D/W water level

water transfer pump

D/W stagnant water

Indirect(item 5)transferring liquid flowing into the1

shutdown is extremely small

4management related totorus room stagnant water

confinement, but predictability istransfer pump.

poor.

1

4

4

transfer pumpSame as above

Partial blockage of(a) D/W stagnant

the pump due towater transfer pumpabrasiveflow ratecontamination

Direct(item 4)migrating from the④

An-Eki-4

Item 7-4(Evaluation
results)
PointofIndivirepresdual
entation

Because item 7-1 is 1(b) Amount, particle①

to increase

Same asDetectionrequirements toavoid work

Item 6-2

properties ofvalue for theSame as

Item 6-1

the chemical

the design
An-Eki-3

Item 5-2

Weighted evaluation of important monitoring items

Item 1Analysis
number■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is unknown[3 points] Countermeasures exist, but throughput decreases significantly due
to suspension of task
[2 points] Countermeasures exist, but throughput decreases due to workload
limitations[1 point] No impact on throughput, or when 7-1 is 1 point

Selected because the pump flow

Supported by multiplexing. In

Although constant monitoring israte decreases due to partial

addition, the effect of short term

required, detectability is good.

blockage caused by abrasive1

contamination in the D/Wfunctional deterioration or

3

Because item 7-1 is 1
point
1

3

shutdown is extremely small

stagnant water transfer pump,processing point to(b) Amount, particle

and because this trend is

Supported by multiplexing. In

Constant monitoring is required

Because item 7-1 is 1

the D/W stagnant

size distribution, andaffected by the amount, particle

addition, the effect of short term

because the equipment is forpointwater transfer pumpparticle density ofsize distribution, and particle

functional deterioration or

D/W water level management

abrasives inIndirectdensity of abrasives in thetransferring liquid(item 5)transferring liquid flowing into theflowing into D/Wtorus room stagnant water

stagnant watertransfer pump.

1

shutdown is extremely small

4

related to confinement, but
predictability is poor.

1

4

4

transfer pumpSame asSame asSame as

above

above

above

Same as above

Partial damage due(a) D/W stagnant

Selected because the pump flow

Supported by multiplexing andAlthough constant monitoring is

to corrosion caused

water transfer pumprate decreases due to partial

sacrificial anodes. In addition,required, detectability is good.

by potential

flow rate

Direct(item 4)difference resulting

from accumulation

An-Eki-5

Same asabove

damage to the D/W stagnant

1

the effect of short termwater transfer pump, andfunctional deterioration or

3

Because item 7-1 is 1
point
1

3

because this trend is affected by

shutdown is extremely smallof abrasives(b) Amount, particle

the amount, particle size

Supported by multiplexing andConstant monitoring is required

Because item 7-1 is 1

migrating from thesize distribution, anddistribution, and particle density

sacrificial anodes. In addition,

because the equipment is for

point

processing point toparticle density ofof abrasives in the transferring

the effect of short term

D/W water level management

the D/W stagnant

abrasives inIndirectliquid flowing into the D/Wwater transfer pumptransferring liquid(item 5)stagnant water transfer pump.

1

functional deterioration or
shutdown is extremely small

4

related to confinement, but
predictability is poor

1

4

4

flowing into D/Wstagnant watertransfer pump©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-2: Risk assessment table for safety equipment (Detailed version) (29/48)
No.170■ Risk assessment table(liquid phase confinement equipment)
Model ID
Process

Ko-3: Debris retrieval

Work

Sa-4

: Processing of debris■ Score table for item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still underdevelopment[2 points] Countermeasures exist, but there are no trackrecords of application at the Fukushima Daiichi[1 point] Countermeasures exist, and have been appliedat the Fukushima Daiichi.

■ Score table for item 7-2[4 points] Requires constant monitoring during task andpredictability is poor
[3 points] Requires constant monitoring during task but
predictability is good
[2 points] Requires regular monitoring and predictability
is poor[1 point] Requires regular monitoring and predictability is
good

Important monitoring items■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is unknown[3 points] Countermeasures exist, but throughput decreases significantly due
to suspension of task
[2 points] Countermeasures exist, but throughput decreases due to workload
limitations[1 point] No impact on throughput, or when 7-1 is 1 point

Weighted evaluation of important monitoring items

Item 1

Item 2Item 3Item 4Item 5-1

Item 5-2

Item 6-1

Item 6-2

Item 6-3

Item 7-1

Item 7-2

Item 7-3

Targetequipment

The functionthat the target is
responsible forWork delay
factor (= error)

Direct causes of error

Indirectcauses oferror

Reasons to be selected

Detection requirements
to avoid work

Directmonitoring/In
directmonitoring

Reason for selection of detection
requirements

Due to deterioration of

Performance(a) Water temperature

Selected because the temperature ofSupported by multiplexing. In addition,

Although constant monitoring is

Because item 7-1 isthe D/W stagnant water

degradation of the pumpinside PCVtransferring liquid flowing into the D/W

the effect of short term functional

required, detectability is good.

1 pointtransfer pump, thecaused by thestagnant water transfer pump wasdeterioration or shutdown is extremely

Analysis
numberD/W stagnant

water transfer
pump

Dynamic

Rise in D/Wboundary

water level

An-Eki-6

Directensured, resulting in

is a design condition,

the D/W water level toexceeding the design

increase

assumption, as a result(b) Amount of heat input

Supported by multiplexing. In addition,

Constant monitoring is required because

Because item 7-1 isof debris retrieval

at processing point

the effect of short term functional

the equipment is for D/W water level

1 point

deterioration or shutdown is extremely

management related to confinement, but④

Same as above

small
1

(a) D/W stagnant water

Selected because the pump flow rate

Supported by multiplexing. In addition,

Although constant monitoring istransfer pump flow rate

decreases due to partial damage caused

the effect of short term functional

required, detectability is good.

Directby abrasive contamination in the D/W(item 4)

stagnant water transfer pump, and

small

3

3

amount, particle size distribution, andparticle density of abrasives in the

Supported by multiplexing. In addition,

Constant monitoring is required because

Because item 7-1 isimpeller and causing the

distribution, and particle

transferring liquid flowing into the torus

the effect of short term functional

the equipment is for D/W water level

1 point

density of abrasives inroom stagnant water transfer pump.

deterioration or shutdown is extremely

management related to confinement, but

small

predictability is poor.

Indirect1(item 5)

4

1

Dynamic

Abnormal

Due to deterioration ofPartial blockage of the(a) PCV stagnant water

Selected because the pump flow rate

Supported by multiplexing. In addition,

Monitoring is required during operation,water discharge

boundarydrainage of

the PCV stagnant water

pump due to dust

discharge pump flow rate

decreases due to partial blockage

the effect of short term functional

but detectability is good.

PCV stagnant

discharge pump, thecontamination migratingwater buffer

design value for thefrom the processing pointtankpump flow rate is notto the PCV stagnant

ensured, resulting inwater discharge pumpincrease

1 point
1

PCV stagnant①

Because item 7-1 is(b) Amount, particle sizetransfer pump

PCV buffer tank to

3because this trend is affected by the

into D/W stagnant water

the water level in the1

into contact with the

impeller to wear out

3

deterioration or shutdown is extremely
1transferring liquid flowing

An-Eki-8

good.

pump due to abrasives

transfer pump coming

above

3

detectability of significant fluctuations is
3

Partial damage to theD/W stagnant water

An-Eki-7

1

Point ofrepresentation

the processing point.

processing point to theSame as3

Individualaffected by the amount of heat input at

migrating from thepump

Impact on
throughput due toerror handling(Indirect causes)

condition, and because this trend is(item 5)Same as above

Point

transferring liquid, which

Indirect

Same as above

Effects on accurate and prompt on-site
response by workers

temperature of the

1

small

Point

pump flow rate is notoperations

Same as above

Presence or absence ofcountermeasures for disturbing
functionsdesign value for the(item 4)verified to deviate from the design

Point

Item 7-4 (Evaluation
results)

Directcaused by dust contamination in the(item 4)

PCV stagnant water discharge pump,4

4

Because item 7-1 is
1 point

deterioration or shutdown is extremely
1

small

1

1

1

and because this trend is affected by theamount and particle size distribution of(b) Chemical properties

dust in the transferring liquid flowing into

Supported by multiplexing. In addition,

The equipment is used to establish

Because item 7-1 is(pH, chloride ion

the torus room stagnant water transfer

the effect of short term functional

circulation cooling by periodically

1 point

concentration, chemical

pump.

deterioration or shutdown is extremely

draining water from the buffer tank, andcomposition) oftransferring liquid flowing
into PCV stagnant watersmall

Indirect(item 5)1

2

requires monitoring during operation,2

but predictability is poor.

12discharge pump©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-2: Risk assessment table for safety equipment (Detailed version) (30/48)
No.171■ Risk assessment table(liquid phase confinement equipment)
Model ID
Process

Ko-3: Debris retrieval

Work

Sa-4

: Processing of debris■ Score table for item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still underdevelopment[2 points] Countermeasures exist, but there are no trackrecords of application at the Fukushima Daiichi[1 point] Countermeasures exist, and have been appliedat the Fukushima Daiichi.

■ Score table for item 7-2[4 points] Requires constant monitoring during task andpredictability is poor
[3 points] Requires constant monitoring during task but
predictability is good
[2 points] Requires regular monitoring and predictability
is poor[1 point] Requires regular monitoring and predictability is
good

Important monitoring items

Weighted evaluation of important monitoring items

Item 1

Item 2Item 3Item 4Item 5-1

Item 5-2

Item 6-1

Item 6-2

Item 6-3

Targetequipment

The functionthat thetarget is
responsibleforWork delay
factor(= error)

Direct causes of
error

Indirectcauses oferror

Reasons to be
selected

Detectionrequirements toavoid work

Directmonitoring/
Indirect
monitoring

Reason for selection of
detection requirements

PCV

Dynamic

Abnormal

Due toPartial damage due(a) PCV stagnant

stagnant

boundarydrainage ofdeterioration of theto corrosion caused

water discharge

Analysis
numberwater

PCV

PCV stagnant

by potential

discharge

stagnant

water discharge

difference resulting

pumpwater buffer

pump, the designfrom accumulationtankvalue for the pumpof dust migrating

flow rate is not

An-Eki-9①

from the processing

ensured, resulting

point to the PCV

in the water level

stagnant waterin the PCV buffer

discharge pumptank to increase■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is unknown[3 points] Countermeasures exist, but throughput decreases significantly due
to suspension of task
[2 points] Countermeasures exist, but throughput decreases due to workload
limitations[1 point] No impact on throughput, or when 7-1 is 1 point

pump flow rate

Item 7-1

Point

Presence or absence ofcountermeasures for disturbing
functionsSupported by multiplexing andAlthough constant monitoring issacrificial anodes. In addition,required, detectability is good.

(item 4)

stagnant water discharge pump,functional deterioration or

and because this trend is

shutdown is extremely small

1

affected by the amount andparticle size distribution of dustin the transferring liquid flowing

and particle densityof dust in

Indirecttransferring liquid(item 5)

Effects on accurate and prompt
on-site response by workers

flow rate decreases due topartial damage to the PCV

size distribution,

Point

Selected because the pump
Direct(b) Amount, particle

Item 7-2

into the PCV stagnant water
discharge pump.

1

the effect of short term

3

Point

Item 7-3

Item 7-4 (Evaluation
results)

Impact on
throughput due
to error handling(Indirect causes)

Individual

Because item 71 is 1 point
1

3

Supported by multiplexing and

The equipment is used to

Because item 7-

sacrificial anodes. In addition,

establish circulation cooling by

1 is 1 point

the effect of short term

periodically draining water fromfunctional deterioration or
shutdown is extremely small

4

flowing into PCV

the buffer tank, and requires
monitoring during operation, but

Point ofrepresentati
on

1

4

4

predictability is poor.

stagnant water
discharge pumpSame asSame asSame as

above

above

above

Same as above

Partial damage due(a) PCV stagnant

Selected because the pumpSupported by multiplexing. In

Monitoring is required during

to corrosion ofwater discharge

flow rate decreases due toaddition, the effect of short

operation, but detectability is

metal components

pump flow rate

such as impellers

Direct(item 4)caused by the
An-Eki-Same as10

abovepartial damage to the PCV

1stagnant water discharge pump,term functional deterioration or

1

good.

Because item 71 is 1 point
1

1

shutdown is extremely small

and because this trend ischemical properties(b) Amount, particle

affected by the chemical

Supported by multiplexing. In

The equipment is used to

Because item 7-of transferring liquidsize distribution,

properties (pH, chloride ion

addition, the effect of shortestablish circulation cooling by

1 is 1 point

migrating from theand particle density

concentration, chemicalterm functional deterioration or

periodically draining water fromprocessing point toof dust in

Indirect

composition) of transferring

the PCV stagnant

transferring liquid(item 5)liquid flowing into the torus roommonitoring during operation, butwater discharge

flowing into PCV

stagnant water transfer pump.

predictability is poor.

pumpstagnant water1

shutdown is extremely small2

the buffer tank, and requires

1

2

2

discharge pumpSame asSame asSame as

above

above

above

Same as above

Partial blockage of(a) PCV stagnant

the pump due towater dischargeabrasivepump flow ratecontamination

Direct(item 4)migrating from theAn-Eki11④

Selected because the pumpSupported by multiplexing. In

Monitoring is required during

flow rate decreases due toaddition, the effect of short

operation, but detectability ispartial blockage caused by1abrasive contamination in theterm functional deterioration or

1

good.

Because item 71 is 1 point
1

1

shutdown is extremely small

PCV stagnant water discharge

processing point to(b) Amount, particle

pump, and because this trend is

Supported by multiplexing. In

The equipment is used to

Because item 7-

the PCV stagnant

size distribution,affected by the amount, particle

addition, the effect of shortestablish circulation cooling by

1 is 1 pointwater discharge

and particle density

size distribution, and particle

term functional deterioration or

periodically draining water frompumpof abrasives inIndirectdensity of abrasives in thetransferring liquid(item 5)transferring liquid flowing into

monitoring during operation, but

flowing into PCV

the torus room stagnant water

predictability is poor.

stagnant watertransfer pump.

1

shutdown is extremely small2

the buffer tank, and requires

1

2

2

discharge pump©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-2: Risk assessment table for safety equipment (Detailed version) (31/48)
No.172■ Risk assessment table(liquid phase confinement equipment)
Model ID
Process

Ko-3: Debris retrieval

Work

Sa-4

: Processing of debris■ Score table for item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still underdevelopment[2 points] Countermeasures exist, but there are no trackrecords of application at the Fukushima Daiichi[1 point] Countermeasures exist, and have been appliedat the Fukushima Daiichi.

■ Score table for item 7-2[4 points] Requires constant monitoring during task andpredictability is poor
[3 points] Requires constant monitoring during task but
predictability is good
[2 points] Requires regular monitoring and predictability
is poor[1 point] Requires regular monitoring and predictability is
good

Important monitoring items■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is unknown[3 points] Countermeasures exist, but throughput decreases significantly due
to suspension of task
[2 points] Countermeasures exist, but throughput decreases due to workload
limitations[1 point] No impact on throughput, or when 7-1 is 1 point

Weighted evaluation of important monitoring items

Item 1

Item 2Item 3Item 4Item 5-1

Item 5-2

Item 6-1

Item 6-2

Item 6-3

Targetequipment

The functionthat thetarget is
responsibleforWork delay
factor(= error)

Direct causes of
error

Indirectcauses oferror

Reasons to be
selected

Detectionrequirements toavoid work

Directmonitoring/
Indirect
monitoring

Reason for selection of detection
requirements

PCV

Dynamic

Abnormal

Due toPartial damage due(a) PCV stagnant

Selected because the pump flow

Supported by multiplexing andAlthough constant monitoring isstagnant

boundarydrainage ofdeterioration of theto corrosion caused

water discharge

rate decreases due to partial

sacrificial anodes. In addition,required, detectability is good.

water

PCV

PCV stagnant

by potential

pump flow rate

discharge

stagnant

water discharge

difference resulting

pumpwater buffer

pump, the designfrom accumulationtankvalue for the pumpof abrasives

Analysis
numberAn-Eki-flow rate is not

12④

migrating from theensured, resulting

processing point toin the water level in

the PCV stagnant

the PCV bufferwater discharge

tank to increasepump

Item 7-1

Point

Presence or absence ofcountermeasures for disturbing
functions

Directdamage to the PCV stagnant(item 4)

water discharge pump, andfunctional deterioration or

because this trend is affected by

shutdown is extremely small

1

the amount, particle size(b) Amount, particle

distribution, and particle density

size distribution, andof abrasives in the transferring

particle density ofabrasives inIndirecttransferring liquid(item 5)liquid flowing into the PCV
stagnant water discharge pump.

1

the effect of short term

Item 7-2

Point

Effects on accurate and prompt
on-site response by workers

3

Item 7-3

Point

Impact on
throughput due toerror handling(Indirect causes)

3

The equipment is used to

Because item 7-1 isestablish circulation cooling by

1 point

the effect of short term

periodically draining water from4

flowing into PCV

the buffer tank, and requires
monitoring during operation, but

Point ofrepresentation

1 point1sacrificial anodes. In addition,

shutdown is extremely small

Individual

Because item 7-1 is

Supported by multiplexing andfunctional deterioration or

Item 7-4(Evaluation
results)

1

4

4

predictability is poor.

stagnant water
discharge pumpSame asSame asSame as

above

above

above

Same as above

Performance(a) Water

Selected because theSupported by multiplexing. In

Monitoring is required during

degradation of thetemperature insidetemperature of transferring liquid

addition, the effect of short term

operation, but detectability ispump caused by the

PCVtemperature of the

Direct(item 4)transferring liquid,

flowing into the PCV stagnant

1water discharge pump wasfunctional deterioration or

1

good.

Because item 7-1 is
1 point
1

1

shutdown is extremely small

verified to deviate from theAn-Eki-Same aswhich is a design(b) Amount of heat

design condition, and because

Supported by multiplexing. In

The equipment is used to

Because item 7-1 is

13

above

condition, exceeding

input at processing

this trend is affected by theaddition, the effect of short term

establish circulation cooling by

1 point

the design

pointamount of heat input at thefunctional deterioration or

periodically draining water fromIndirectassumption, as aprocessing point.

(item 5)

result of debris

1

shutdown is extremely small

2Same asSame as

above

above

above

Same as above

Partial damage to(a) PCV stagnant

the pump due towater dischargeabrasives migrating

pump flow rate

Direct(item 4)point to the PCVSame as

14

above

2

predictability is poor.

from the processing

An-Eki-1monitoring during operation, but

retrieval operations

Same asthe buffer tank, and requires

2

Selected because the pump flow

Supported by multiplexing. In

Monitoring is required during

rate decreases due to partial

addition, the effect of short term

operation, but detectability isdamage caused by abrasive1

contamination in the PCV

functional deterioration or

1

good.

Because item 7-1 is
1 point
1

1

shutdown is extremely small

stagnant water discharge pump,stagnant water(b) Amount, particle

and because this trend is

Supported by multiplexing. In

The equipment is used to

Because item 7-1 isdischarge pumpsize distribution, andaffected by the amount, particle

addition, the effect of short term

establish circulation cooling by

1 point

coming into contact

particle density ofsize distribution, and particle

functional deterioration or

periodically draining water fromwith the impeller

abrasives inIndirectdensity of abrasives in theand causing thetransferring liquid(item 5)transferring liquid flowing into themonitoring during operation, but

impeller to wear out

flowing into PCV

torus room stagnant water

predictability is poor.

stagnant watertransfer pump.

1

shutdown is extremely small2

the buffer tank, and requires

1

2

2

discharge pump©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-2: Risk assessment table for safety equipment (Detailed version) (32/48)
No.173■ Risk assessment table■ Score table for item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still underdevelopment[2 points] Countermeasures exist, but there are no trackrecords of application at the Fukushima Daiichi[1 point] Countermeasures exist, and have been appliedat the Fukushima Daiichi.

(liquid phase confinement equipment)
Model ID
Process

Ko-3: Debris retrieval

Work

Sa-4

: Processing of debris■ Score table for item 7-2[4 points] Requires constant monitoring during task andpredictability is poor
[3 points] Requires constant monitoring during task but
predictability is good
[2 points] Requires regular monitoring and predictability
is poor[1 point] Requires regular monitoring and predictability is
good

Important monitoring items

Weighted evaluation of important monitoring items

Item 1

Item 2Item 3Item 4Item 5-1

Item 5-2

Item 6-1

Item 6-2

Item 6-3

Targetequipment

The functionthat thetarget is
responsibleforWork delay
factor (=error)

Direct causes of
error

Indirectcauses oferror

Reasons to be
selected

Detectionrequirements toavoid work

Directmonitoring/
Indirect
monitoring

Reason for selection of
detection requirements

D/W

StaticDecrease in

As the D/W

Partial damage due(a) D/W water level

Selected because the D/W

The impact on the safety

Post-detection is possible

Because item 7-1

boundary

D/W water

deteriorates andto corrosion caused

water level decreases asfunctions is small.

by constant monitoring ofis 1 pointlevel

the size of theby changes in thethe size of the opening in(When the D/W water

the D/W water level, andopening increases,

water quality ofIndirectthe D/W increases, andthe leakage to thestagnant water(Item 4)

because this trend is

torus room

migrating from theaffected by the conditionsof the D/W stagnant

to identify the area ofincreases and theprocessing point tofor water quality at thewater transfer pump candamage.

D/W water level

the D/W

D/W wall surface.

be adjusted.)

Analysis
numberAn-Eki15①

decreases.

Item 7-1

Point

1

the flow rate
PipingStaticofboundarytransferring
liquid in the16

systemlevel decreases
excessively, the flow rate

Point

3

Effects on accurate andprompt on-site response byworkers

detectability is good.
However, it may be difficult

Item 7-3

Point

Impact on
throughput due toerror handling(Indirect causes)

1

The impact on the safety

Constant monitoring is

Because item 7-1

functions is small.

required because theis 1 point(When the D/W water

concentration,

Indirect

chemical(item 5)1level decreases
excessively, the flow ratecomposition) ofof the D/W stagnant

D/W wall surface inwater transfer pump canconfinement, but
predictability is poor.

1

Point ofrepresent
ation

4

4

be adjusted.)

Partial blockage(a) Flow rate in the

Selected because the flow

If there is a significant

Detection of trends andBecause item 7-1

deterioration of thedue tosystemrate in the systemtrend toward blockage, it

post-detection are possible

is 1 point

piping, the design

accumulation of

decreases due to blockage

can be handled bythrough constantvalue of flow rate

dust migrating fromin the piping, and because

flushing the piping.

monitoring of the flow rate

for the transferring

the processing

liquid in the

point to the piping

Direct(item 4)ensured, resulting
in the water level

Individual

equipment is related to4

Due tosystem is not

Item 7-4 (Evaluation
results)3

properties (pH,liquid phase

Decrease in

Presence or absence ofcountermeasures for
disturbing functions

Item 7-2(b) Chemical

chloride ion

An-Eki-■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is unknown[3 points] Countermeasures exist, but throughput decreases significantly due
to suspension of task
[2 points] Countermeasures exist, but throughput decreases due to workload
limitations[1 point] No impact on throughput, or when 7-1 is 1 point

this trend is affected by theamount, particle sizein the system, and13

detectability is good.

1

3

distribution, and particle
density of dust in the①4transferring liquid flowing

in the connected

into the piping

boundary or tankto increase or(b) Amount, particle

If there is a significant

Constant monitoring isdecrease.

size distribution,

trend toward blockage, it

required because theand particle density

Indirectof dust in the(item 5)transferring liquid1

can be handled byflushing the piping.

4

equipment is related toconfinement, but

Because item 7-1
is 1 point
1

4

predictability is poor.

flowing into piping©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-2: Risk assessment table for safety equipment (Detailed version) (33/48)
No.174■ Risk assessment table(liquid phase confinement equipment)
Model ID
Process

Ko-3: Debris retrieval

Work

Sa-4

: Processing of debris■ Score table for item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still underdevelopment[2 points] Countermeasures exist, but there are no trackrecords of application at the Fukushima Daiichi[1 point] Countermeasures exist, and have been applied at the
Fukushima Daiichi.

■ Score table for item 7-2[4 points] Requires constant monitoring during task andpredictability is poor
[3 points] Requires constant monitoring during task but
predictability is good
[2 points] Requires regular monitoring and predictability is poor
[1 point] Requires regular monitoring and predictability is good

Important monitoring items■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is unknown[3 points] Countermeasures exist, but throughput decreases significantly due tosuspension of task
[2 points] Countermeasures exist, but throughput decreases due to workload
limitations[1 point] No impact on throughput, or when 7-1 is 1 point

Weighted evaluation of important monitoring items

Item 1

Item 2Item 3Item 4Item 5-1

Item 5-2

Item 6-1

Item 6-2

Item 6-3

Targetequipment

The functionthat the target
is responsibleforWork delay
factor (= error)

Direct causes of error

Indirectcauses oferror

Reasons to be selected

Detection requirements
to avoid work

Directmonitoring/In
directmonitoring

Reason for selection of detection
requirements

Static boundary

Decrease in the

As the piping

Partial damage due to(a) Flow rate in theflow rate ofdeteriorates and thecorrosion caused bysystem + amount oftransferring

size of the boundary

potential difference

leakageliquid in the

opening increases, theresulting from

Directresulting from damage to the piping,systemamount of transferring

accumulation of dust

(item 4)and because this trend is affected byliquid decreases.

migrating from theItem 7-1

Item 7-2

Item 7-3

Analysis
numberPipingPresence or absence ofcountermeasures for disturbing
functions

Point

Effects on accurate and prompt on-site
response by workers

Point

Impact on throughput due toerror handling (Indirectcauses)Individual

1Because item 7-1 is 1 point

3

Point ofrepresentationSelected because the flow rate oftransferring liquid in the systemdecreases due to occurrences of leaks

With constant monitoring of the flow

Although there is impact on safety1functions, the frequency of3

occurrence is expected to be low.

rate in the system and leak detection,

post-detection is possible, anddetectability is good.

the amount and particle size distribution

processing point to the①

An-Eki-17

Point

Item 7-4(Evaluation
results)of dust flowing into the piping.

piping(b) Amount, particle size

Although there is impact on safety

Constant monitoring is required

distribution, and particle

functions, the frequency of

because the equipment is related todensity of dust in theoccurrence is expected to be low.

transferring liquid

Indirectflowing into liquid(item 5)1

4Because item 7-1 is 1 point

confinement, but predictability is poor.

4

1

4

systemSame as above

Same as above

Same as above

Same as above

Partial damage due to(a) Flow rate in the

Selected because the flow rate of

Although there is impact on safety

With constant monitoring of the flow

corrosion caused bysystem + leak detection

transferring liquid in the system

functions, the frequency ofrate in the system and leak detection,changes in the water

Directdecreases due to occurrences of leaks

quality of stagnant water(item 4)

resulting from damage to the piping,migrating from thepiping
An-Eki-18

above

post-detection is possible, and3

detectability is good.

13and because this trend is affected byprocessing point to theSame asoccurrence is expected to be low.
1

Because item 7-1 is 1 point

the chemical properties (pH, chloride(b) Chemical properties

ion concentration, and chemical

Although there is impact on safety

Constant monitoring is required(pH, chloride ioncomposition) of dust flowing into thefunctions, the frequency of

because the equipment is related toconcentration, chemical

piping.

occurrence is expected to be low.

confinement, but predictability is poor.

Because item 7-1 is 1 point
4composition) oftransferring liquid
flowing into liquid

Indirect1(item 5)4

14systemPipingStatic boundarySame as above

Due to deterioration ofPartial blockage due to(a) Flow rate in the

Selected because the flow rate in the

If there is a significant trend toward

Detection of trends and post-detection

the piping, the design

accumulation ofsystemsystem decreases due to blockage inblockage, it can be handled byare possible through constantvalue of flow rate forabrasives migrating fromthe piping, and because this trend isflushing the piping.

monitoring of the flow rate in thethe transferring liquid

the processing point toaffected by the amount, particle sizein the system is not

the piping

distribution, and particle density of

Directensured, resulting in(item 4)

the water level in theabrasives in the transferring liquid

Because item 7-1 is 1 point

system, and detectability is good.
1

3

1

3

flowing into the piping

connected boundary ortank to increase or
An-Eki-19

decrease.

④

4(b) Amount, particle size

If there is a significant trend toward

Constant monitoring is required

distribution, and particle

blockage, it can be handled bybecause the equipment is related todensity of abrasives influshing the piping.

the transferring liquid
flowing into piping

Indirect(item 5)1

Because item 7-1 is 1 point

confinement, but predictability is poor.
41

4©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-2: Risk assessment table for safety equipment (Detailed version) (34/48)
No.175■ Risk assessment table(liquid phase confinement equipment)
Model ID
Process

Ko-3: Debris retrieval

Work

Sa-4

: Processing of debris■ Score table for item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still underdevelopment[2 points] Countermeasures exist, but there are no trackrecords of application at the Fukushima Daiichi[1 point] Countermeasures exist, and have been appliedat the Fukushima Daiichi.

■ Score table for item 7-2[4 points] Requires constant monitoring during task andpredictability is poor
[3 points] Requires constant monitoring during task but
predictability is good
[2 points] Requires regular monitoring and predictability
is poor[1 point] Requires regular monitoring and predictability is
good

Important monitoring items■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is unknown[3 points] Countermeasures exist, but throughput decreases significantly due
to suspension of task
[2 points] Countermeasures exist, but throughput decreases due to workload
limitations[1 point] No impact on throughput, or when 7-1 is 1 point

Weighted evaluation of important monitoring items

Item 1

Item 2Item 3Item 4Item 5-1

Item 5-2

Item 6-1

Item 6-2

Item 6-3

Targetequipment

The functionthat the target
is responsibleforWork delay
factor (= error)

Direct causes of error

Indirectcauses oferror

Reasons to be selected

Detection requirements
to avoid work

Directmonitoring/In
directmonitoring

Reason for selection of detection
requirements

Static boundary

Item 7-1

Item 7-2

Item 7-3

Analysis
numberValves

Point

Presence or absence ofcountermeasures for disturbing
functions

Point

Effects on accurate and prompt on-site
response by workers

Decrease in the

As the valve

Partial damage due to(a) Flow rate in the

Selected because the flow rate of

Although there is impact on safety

With constant monitoring of the flow

(Integration offlow rate ofdeteriorates and thecorrosion caused bysystem + leak detection

transferring liquid in the system

functions, the frequency ofrate in the system and leak detection,

valves present

transferring

size of the boundary

dust migrating from thein the system)

liquid in the

opening increases, theprocessing point to thesystemamount of transferring

valve

Directdecreases due to occurrences of leaks(item 4)

resulting from damage to the valve, andImpact on throughput
due to error handling(Indirect causes)

Individual

Point ofrepresentationBecause item 7-1 is 1
pointpost-detection is possible, and3

detectability is good.

1

3

because this trend is affected by theliquid decreases.

chemical properties (pH, chloride ion
concentration, chemical composition) of(b) Chemical properties

dust flowing into the liquid-phase(pH, chloride ion①

An-Eki-20

occurrence is expected to be low.
1

Point

Item 7-4 (Evaluation
results)

system.

concentration, chemical

Although there is impact on safety

Constant monitoring is required

Because item 7-1 is 1

functions, the frequency of

because the equipment is related topoint

occurrence is expected to be low.

confinement, but predictability is poor.

4composition) oftransferring liquid

Indirectflowing into liquid(item 5)

1

4

1

4

systemSame as above

Same as above

Same as above

The valve deteriorates

Adhesion of the valve(a) Flow rate in the

Selected because the flow rate of

Although there is impact on safety

With constant monitoring of the flow

and the amount ofdue to accumulation ofsystem + leak detection

transferring liquid in the system

functions, the frequency ofrate in the system and leak detection,transferring liquidabrasives migrating fromdeviates from thethe processing point tocontrol value.

the valve

Directdecreases due to blockage resulting(item 4)from adhesion of the valve, andoccurrence is expected to be low.
1

Because item 7-1 is 1
pointpost-detection is possible, and3

detectability is good.

1

3

because this trend is affected by thechemical properties (pH, chloride ion④

An-Eki-21(b) Amount, particle size

concentration, chemical composition) of

Although there is impact on safety

Constant monitoring is required

Because item 7-1 is 1

distribution, and particle

dust flowing into the liquid-phasefunctions, the frequency of

because the equipment is related topoint

density of abrasives insystem.

occurrence is expected to be low.

confinement, but predictability is poor.

4

the transferring liquid
flowing into liquid
system

PCV stagnant

An-Eki-22

Static boundary

Indirect1(item 5)4

1

Decrease in the

Due to damage to thePartial damage due to(a) Water level of PCV

Selected because the water level in the

The impact on safety functions isWith constant monitoring of the flow

water buffer

flow rate of

PCV stagnant water

corrosion caused bystagnant water buffer

buffer tank decreases due to damage

small, and the frequency ofrate in the system and leak detection,tanktransferring

buffer tank, the coolant

accumulation andtank + leak detection

liquid in thethroughput is reduced,

adhesion of dust

systemand the site boundary

migrating from theradiation dose/worker

processing point to the

exposure dose

PCV stagnant water

deviates from thecontrol value.

①

buffer tank

Directto the PCV stagnant water buffer tank,(item 4)and this tendency is affected by theoccurrence is expected to be low.
1

4

Because item 7-1 is 1
pointpost-detection is possible, and3

detectability is good.

13chemical properties (pH, chloride ion
concentration, chemical composition) ofdust flowing into the PCV stagnant(b) Chemical properties

water buffer tank.

(pH, chloride ion
concentration, chemical

The impact on safety functions is

Constant monitoring is required

Because item 7-1 is 1

small, and the frequency of

because the equipment is related topoint

occurrence is expected to be low.

confinement, but predictability is poor.

4composition) oftransferring liquid
flowing into liquid

Indirect(item 5)

1

4

1

4

system©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-2: Risk assessment table for safety equipment (Detailed version) (35/48)
No.176■ Risk assessment table(liquid phase confinement equipment)
Model ID
Process

Ko-3: Debris retrieval

Work

Sa-4

: Processing of debris■ Score table for item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still underdevelopment[2 points] Countermeasures exist, but there are no trackrecords of application at the Fukushima Daiichi[1 point] Countermeasures exist, and have been appliedat the Fukushima Daiichi.

■ Score table for item 7-2[4 points] Requires constant monitoring during task andpredictability is poor
[3 points] Requires constant monitoring during task but
predictability is good
[2 points] Requires regular monitoring and predictability
is poor[1 point] Requires regular monitoring and predictability is
good

Important monitoring items■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is unknown[3 points] Countermeasures exist, but throughput decreases significantly due
to suspension of task
[2 points] Countermeasures exist, but throughput decreases due to workload
limitations[1 point] No impact on throughput, or when 7-1 is 1 point

Weighted evaluation of important monitoring items

Item 1

Item 2Item 3Item 4Item 5-1

Item 5-2

Item 6-1

Item 6-2

Item 6-3

Targetequipment

The functionthat thetarget is
responsibleforWork delay
factor (=error)

Direct causes of
error

Indirectcauses oferror

Reasons to be
selected

Detectionrequirements toavoid work

Directmonitoring/
Indirect
monitoring

Reason for selection of
detection requirements

D/W

StaticDecrease in

Due toPartial blockage(a) Flow rate in the

Selected because the flow rate

Because the cyclone is

Detection of trends and post-

Because item 7-1 is 1

stagnant

boundary

the flow rate

deterioration of thedue tosystem + differential

in the system decreases due tostructured so that dust does

detection are possible throughpointwater coarseofD/W stagnant

accumulation ofpressure before andblockage of the D/W stagnant

not easily accumulate, theconstant monitoring of the flow

particles

transferring

water coarse

dust migrating fromafter D/W stagnant

water coarse particle removal

frequency of occurrence israte in the system and theremovalliquid in theparticle removal

the processing

water coarse

equipment, and because thislow, and because the auto-

Analysis
numberequipment

systemequipment, thepoint to the D/Wparticle removal

design value ofstagnant waterequipment

flow rate for thetransferring liquid

An-Eki-in the system is23

not ensured,

Direct(item 4)

trend is affected by the amount,

Item 7-1

Poin
t

1

Presence or absence ofcountermeasures for disturbing
functionsstrainer automatically

Item 7-2

Point

Effects on accurate and prompt
on-site response by workers

Point

Impact on throughput
due to error handling(Indirect causes)

Item 7-4(Evaluation
results)
Point
of
Indiv
represidual
entationdifferential pressure before and3after the D/W stagnant waterparticle size distribution, anddischarges the contaminantscoarse particle removal

coarse particle

particle density of dust in theafter a blockage is detected,

equipment, and detectability isremoval equipment

transferring liquid flowing into

the impact on safety functions

good.

the D/W stagnant water coarse

is considered to be small.

①

Item 7-3

13

4

particle removal equipment

resulting in the(b) Amount, particle

Constant monitoring is required

Because item 7-1 is 1

D/W water level tosize distribution,

because the equipment ispointincreaseand particle density

related to confinement, butof dust in thetransferring liquid
flowing into D/Wpredictability is poor.

Indirect1(item 5)Same as above

4

1

4

stagnant watercoarse particle
removal equipment

An-Eki24

Same asSame asSame as

above

above

above

Due toPartial damage due(a) Flow rate in the

Selected because leaks occur

With constant monitoring of the

Because item 7-1 is 1

deterioration of theto corrosion caused

system + amount ofdue to damage to the D/Wflow rate in the system and leakpoint

D/W stagnant

by potential

leakagestagnant water coarse particle

detection, post-detection iswater coarse

difference resulting

particle removalfrom accumulation

because this trend is affected byequipment,of dust migrating

the chemical properties (pH,leakage occur,from the processing

and the siteboundary radiation

Same asabove

point to the D/Wstagnant water

dose/worker

coarse particle

exposure dose

removal equipment

deviates from thecontrol value.

Direct(item 4)

removal equipment, and1Same as above

3

possible, and detectability is

1

3

good.

chloride ion concentration,(b) Amount, particle

chemical composition) ofsize distribution,transferring liquid flowing intoand particle densityof dust in thetransferring liquid
flowing into D/W(item 5)

Because item 7-1 is 1

because the equipment is

point

4

related to confinement, but

the liquid system
Indirect

Constant monitoring is requiredpredictability is poor.
1

Same as above

4

1

4

stagnant watercoarse particle
removal equipment©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-2: Risk assessment table for safety equipment (Detailed version) (36/48)
No.177■ Risk assessment table(liquid phase confinement equipment)
Model ID
Process

Ko-3: Debris retrieval

Work

Sa-4

: Processing of debris■ Score table for item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still underdevelopment[2 points] Countermeasures exist, but there are no trackrecords of application at the Fukushima Daiichi[1 point] Countermeasures exist, and have been applied at
the Fukushima Daiichi.

■ Score table for item 7-2[4 points] Requires constant monitoring during task andpredictability is poor
[3 points] Requires constant monitoring during task but
predictability is good
[2 points] Requires regular monitoring and predictability ispoor[1 point] Requires regular monitoring and predictability is
good

Important monitoring items■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is unknown[3 points] Countermeasures exist, but throughput decreases
significantly due to suspension of task
[2 points] Countermeasures exist, but throughput decreases due toworkload limitations[1 point] No impact on throughput, or when 7-1 is 1 point

Weighted evaluation of important monitoring items

Item 1

Item 2Item 3Item 4Item 5-1

Item 5-2

Item 6-1

Item 6-2

Item 6-3

Targetequipment

The functionthat thetarget is
responsibleforWork delay
factor (=error)

Direct causes of
error

Indirectcauses oferror

Reasons to be
selected

Detectionrequirements toavoid work

Directmonitoring/
Indirect
monitoring

Reason for selection of
detection requirements

D/W

StaticDecrease in

Due toPartial damage due(a) Flow rate in the

Selected because leaks

The impact on safety

With constant monitoring

stagnant

boundary

the flow rate

deterioration of theto corrosion caused

system + amount of

occur due to damage tofunctions is small, andof the flow rate in thewater coarseofD/W stagnant

by changes in theleakageparticles

transferring

water coarse

water quality ofremovalliquid in theparticle removal

stagnant waterequipment, and because

equipment

systemequipment,

migrating from thethis trend is affected bydetectability is good.

leakage occur,

processing point to(b) Chemical

the chemical properties

Constant monitoring is

Because item 7-1 is 1

and the site

the D/W stagnant

properties (pH,(pH, chloride ion

required because thepointwater coarse

chloride ion

concentration, chemical

equipment is related todose/worker

particle removal

concentration,

composition) ofconfinement, but

exposure dose

equipmentchemicalAnalysis
numberAn-Eki-boundary radiation25①

deviates from thecomposition) of

control value.

transferring liquid

Directthe D/W stagnant water(item 4)coarse particle removal

Indirect(item 5)Item 7-1

Point

1

Presence or absence ofcountermeasures for
disturbing functions

the frequency ofoccurrence is expected

Item 7-2

Point3

to be low.

system and leakdetection, post-detection

Point

Impact on throughput
due to error handling(Indirect causes)

Item 7-4(Evaluation
results)
Point
of
Indiv
represidual
entation

Because item 7-1 is 1
point
1

3

is possible, and4predictability is poor.

transferring liquid flowing
into the liquid system

Effects on accurate andprompt on-site response
by workers

Item 7-3

1Same as above

4

1

4

flowing into D/Wstagnant watercoarse particle
removal equipment

Same asSame asSame as

above

above

above

Due toPartial blockage(a) Flow rate in the

Selected because the flow

Because the cyclone is

Detection of trends andBecause item 7-1 is 1

deterioration of thedue tosystem + differential

rate in the system

structured so that dust

post-detection arepoint

D/W stagnant

accumulation ofpressure before anddecreases due todoes not easily

possible through constantwater coarse

abrasives migrating

after D/W stagnant

blockage of the D/W

accumulate, themonitoring of the flow rateparticle removalfrom the processing

water coarse

stagnant water coarse

frequency of occurrencein the system and theequipment, thepoint to the D/Wparticle removal

particle removal

is low, and because thedesign value ofstagnant waterequipment

flow rate for thecoarse particle

transferring liquid
An-Eki-in the system is26

not ensured,

Direct(item 4)

removal equipment④

resulting in theD/W water level toincreaseequipment, and because1

auto-strainer

differential pressure
3

before and after the D/Wthis trend is affected byautomatically discharges

stagnant water coarse

the amount, particle size

the contaminants after aparticle removal

distribution, and particle

blockage is detected, theequipment, anddensity of dust in theimpact on safety

detectability is good.

transferring liquid flowing

functions is considered tointo the liquid system

be small.

1

34(b) Amount, particle

Constant monitoring is

Because item 7-1 is 1

size distribution,required because thepoint

and particle density

equipment is related toof abrasives in thetransferring liquid

Indirect(item 5)1Same as above

4

confinement, but

1

4

predictability is poor.

flowing into liquid

system©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-2: Risk assessment table for safety equipment (Detailed version) (37/48)
No.178■ Risk assessment table(cooling equipment)■ Score table for item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still underdevelopment[2 points] Countermeasures exist, but there are no trackrecords of application at the Fukushima Daiichi[1 point] Countermeasures exist, and have been appliedat the Fukushima Daiichi.

Model ID
Process

Ko-3: Debris retrieval

Work

Sa-4

: Processing of debris■ Score table for item 7-2[4 points] Requires constant monitoring during task andpredictability is poor
[3 points] Requires constant monitoring during task but
predictability is good
[2 points] Requires regular monitoring and predictability
is poor[1 point] Requires regular monitoring and predictability is
good

Important monitoring items
Item 1

Item 2Item 3Item 4Item 5-1

Targetequipment

The functionthat thetarget is
responsibleforWork delay
factor (=error)

Direct causes of
error

Indirectcauses of
error

D/W

Cooldown of

Increase instagnantdebris

PCV liquidwatertransfer

Analysis
numberItem 5-2■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is unknown[3 points] Countermeasures exist, but throughput decreases significantly due
to suspension of task
[2 points] Countermeasures exist, but throughput decreases due to workload
limitations[1 point] No impact on throughput, or when 7-1 is 1 point

Weighted evaluation of important monitoring items
Item 6-1

Item 6-2

Item 6-3

Directmonitoring/
Indirect
monitoring

Reason for selection of detection
requirements

Item 7-1

Reasons to be
selected

Detectionrequirements toavoid work

Due toPartial damage to(a) D/W stagnant

Selected because partial

Supported by multiplexing andContinuous monitoring isdeterioration of thethe D/W stagnant

water transfer pumpdamage due to corrosion caused

sacrificial anodes. In addition,required, but predictability isphase

D/W stagnant

water transfer pumpflow rate

temperaturewater transfer

due to corrosion ofpump, the design
value for the pump

pump

flow rate is not
An-Rei-1

ensured, resulting

Directby dust in the D/W stagnant(item 4)

water transfer pump reduces thefunctional deterioration or

metal components

pump flow rate, and because this

shutdown is extremely small

such as impellers,trend is affected by the chemicalcaused by dust
①

Point

Presence or absence ofcountermeasures for disturbing
functions

Item 7-2

contained in thein the PCV liquid

coolant migratingphase temperaturefrom the processing

to increase.

point to the D/Wstagnant watertransfer pump(b) Chemical

properties (pH, chloride ion

properties (pH,concentration, chemical

chloride ion
concentration,
chemicalcomposition) of

1

composition) of transferring liquid

Indirectflowing into the D/W stagnant(item 5)water transfer pump.

the effect of short term

Point

4

poor.

Point

Impact on throughput
due to error handling(Indirect causes)

point
1

4

Although the equipment is used

Because item 7-1 is 1

sacrificial anodes. In addition,

for securing the PCV coolingpoint

the effect of short termwater and required to operate

shutdown is extremely small

Item 7-4(Evaluation
Results)
PointofIndivirepresdual
entation

Because item 7-1 is 1

Supported by multiplexing andfunctional deterioration or1

Effects on accurate and prompt
on-site response by workers

Item 7-3

4during retrieval operations,3

detectability for significant

13functional deterioration is goodtransferring liquid at
D/W stagnant watertransfer pump inlet

Same asSame asSame as

above

above

above

Same as above

Partial damage to(a) D/W stagnant

the D/W stagnant

water transfer pumpwater transfer pumpflow rate

due toDirect(item 4)contamination and

An-Rei-2

Same asabove

Selected because the pump flow

Supported by multiplexing. In

Continuous monitoring israte decreases due to theaddition, the effect of short term

required, but predictability isfunctional deterioration of the1

D/W stagnant water transfer

functional deterioration or

4

poor.

Because item 7-1 is 1
point
1

4

shutdown is extremely small

pump, and because this trend isentrapment of dust(b) Amount, particle

affected by the amount andSupported by multiplexing. In

Although the equipment is used

Because item 7-1 is 1

contained in thesize distribution, andparticle size distribution of dust

addition, the effect of short term

for securing the PCV coolingpoint

coolant migrating

particle density ofin the transferring liquid flowing

functional deterioration orwater and required to operatefrom the processing

dust in the

Indirect

into the D/W stagnant water

point to the D/Wtransferring liquid(item 5)transfer pump.

stagnant waterflowing into D/Wtransfer pumpstagnant water1

shutdown is extremely small

3

during retrieval operations,detectability for significant

1

4

3

functional deterioration is goodtransfer pump inlet©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-2: Risk assessment table for safety equipment (Detailed version) (38/48)
No.179■ Risk assessment table■ Score table for item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still underdevelopment[2 points] Countermeasures exist, but there are no trackrecords of application at the Fukushima Daiichi[1 point] Countermeasures exist, and have been applied at the
Fukushima Daiichi.

(cooling equipment)
Model ID

Process

Ko-3: Debris retrieval

Work

Sa-4

: Processing of debris■ Score table for item 7-2[4 points] Requires constant monitoring during task andpredictability is poor
[3 points] Requires constant monitoring during task but
predictability is good
[2 points] Requires regular monitoring and predictability is poor
[1 point] Requires regular monitoring and predictability is good

Important monitoring items
Item 2Item 3

Targetequipment

The functionthat thetarget is
responsibleforWork delay
factor (=error)

Direct causes of
error

D/W stagnant

Cooldown of

Increase in

Due to deterioration

Partial damage to the(a) D/W stagnant

Selected because theSupported by multiplexing. In

Continuous monitoring is

waterdebris

PCV liquidof the D/W stagnant

D/W stagnant water

water transfer pump

pump flow rate decreases

addition, the effect of short term

required, but predictability istransferphasewater transfer

transfer pump due toflow ratepumptemperature

pump, the design

abrasives discharged

value for the pumpduring AWJ

flow rate is notprocessing in the(b) Amount of

pump, and because thisSupported by multiplexing. In

Although the equipment is usedensured, resulting

coolant migratingabrasives in thetrend is affected by theaddition, the effect of short term

for securing the PCV coolingin the PCV liquid

An-Rei-3

Item 5-1

Indirectcauses oferror

Item 5-2

Weighted evaluation of important monitoring items

Item 1Analysis
numberItem 4■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is unknown[3 points] Countermeasures exist, but throughput decreases significantly due tosuspension of task
[2 points] Countermeasures exist, but throughput decreases due to workload
limitations[1 point] No impact on throughput, or when 7-1 is 1 point

Reasons to be
selected

Item 6-1

Detectionrequirements toavoid work

Item 6-2
Directmonitoring/
Indirect
monitoring

Direct (item
4)

Item 6-3

Reason for selection of
detection requirements

due to the functional

Item 7-1

Point1

deterioration of the D/WPresence or absence ofcountermeasures for disturbing
functionsfunctional deterioration or

Item 7-2

Point

4

Effects on accurate and prompt
on-site response by workers

poor.

Point

Impact on throughput due toerror handling (Indirectcauses)Item 7-4(Evaluation
Results)
PointofIndivirepresdual
entation

Because item 7-1 is 1 point

1

4

shutdown is extremely small

stagnant water transferfrom the processing

transferring liquidamount and particle sizefunctional deterioration orwater and required to operate

phase temperaturepoint to the D/Wflowing into D/Wdistribution of abrasives in

shutdown is extremely small

during retrieval operations,to increase.

stagnant water

stagnant water

Indirecttransfer pumptransfer pump inlet(item 5)④

Item 7-3

the transferring liquid
flowing into the D/Wcoming into contact

stagnant water transfer

with the impeller, andpump.

Because item 7-1 is 1 point

4

detectability for significant
13functional deterioration is good1

3

causing the impeller

to wear out
Same asSame asSame as

above

above

above

Same as above

Partial damage to the(a) D/W stagnant

D/W stagnant water

water transfer pumptransfer pump due toflow rate

Direct (item4)

contamination and

An-Rei-4

abrasives contained

abovein the coolant
migrating from theprocessing point to
the D/W stagnant
water transfer pumpSupported by multiplexing. In

Continuous monitoring ispump flow rate decreases

addition, the effect of short term

required, but predictability is

due to the functional

1

deterioration of the D/Wentrapment ofSame asSelected because thefunctional deterioration or

4

poor.

Because item 7-1 is 1 point
1

4

shutdown is extremely small

stagnant water transfer(b) Amount, particle

coolant flowing into

Indirect(item 5)

Supported by multiplexing. In

temperature of coolant
flowing into the liquid4

for securing the PCV cooling

trend is affected by theparticle density ofabrasives in the

Although the equipment is used

pump, and because thissize distribution, and1system.

addition, the effect of short termfunctional deterioration orwater and required to operate
3

D/W stagnant water

during retrieval operations,1

Because item 7-1 is 1 point

3

1

Because item 7-1 is 1 point

4

detectability for significant

shutdown is extremely small

functional deterioration is goodtransfer pumpSame asSame asSame as

above

above

above

Same as above

Performance(a) Water

degradation of thetemperature insidepump caused by the

PCV

Direct (item4)

coolant temperature,

Supported by multiplexing. In

pump flow rate decreases

addition, the effect of short term

due to the functional

1

deterioration of the D/W

which is a design
An-Rei-5

Selected because thefunctional deterioration orContinuous monitoring isrequired, but predictability is
4

poor.

shutdown is extremely small

stagnant water transfer

Same ascondition, exceeding(b) Amount of heatpump inlet, and because

Supported by multiplexing. In

Although the equipment is usedabove

the design

input at processing

this trend is affected by theaddition, the effect of short term

for securing the PCV coolingassumption, as apointtemperature of transferringfunctional deterioration orwater and required to operate

result of debris
retrieval operations

Indirect(item 5)liquid flowing into the D/W

1

shutdown is extremely small

3

during retrieval operations,stagnant water transfer

detectability for significant

pump inlet.

functional deterioration is good

4

1

Because item 7-1 is 1 point

3©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-2: Risk assessment table for safety equipment (Detailed version) (39/48)
No.180■ Risk assessment table(cooling equipment)■ Score table for item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still underdevelopment[2 points] Countermeasures exist, but there are no trackrecords of application at the Fukushima Daiichi[1 point] Countermeasures exist, and have been appliedat the Fukushima Daiichi.

Model ID
Process

Ko-3: Debris retrieval

Work

Sa-4

: Processing of debris■ Score table for item 7-2[4 points] Requires constant monitoring during task andpredictability is poor
[3 points] Requires constant monitoring during task but
predictability is good
[2 points] Requires regular monitoring and predictability
is poor[1 point] Requires regular monitoring and predictability is
good

Important monitoring items
Item 5-1

Work delay
factor (=error)

Direct causes of
error

CoolerCooldown ofDegradation

Attenuation of heat

Performance(a) Cooler inlet/outlet

Selected because it isWhen the circulation cooling

Although the equipment is used

Because item 7-1 isdebrisof coolingremoval due todegradation of thetemperature

possible to detect thesystem shutdown, the external

for reactor water injection

1 pointfunction duechanges in thecooler caused byfunctional deterioration ofwater injection system using

cooldown and required toto reduced

properties of coolerchanges in theamount ofcomponents

properties of metalheat removal

components due toin the cooler①

An-Rei-6

Direct(item 4)

Reason for selection of
detection requirements

Item 7-1

Point

the cooler through thetemperature differential

RO treated water as a water1

cooler, and because thiseffect of short term functional

deterioration is goodcoolant migrating

trend is affected by thedeterioration or shutdown is

above

above

above

extremely smalltransferring liquid flowing

When the circulation coolingContinuous monitoring is

Because item 7-1 isproperties (pH,into the cooler.

system shutdown, the externalrequired, and predictability is

1 point

chloride ionwater injection system using

good.

concentration,

RO treated water as a water

Indirect1(item 5)31effect of short term functional

flowing into cooler

deterioration or shutdown is3

extremely small

Partial damage to(a) Cooler inlet/outlet

Selected because it isWhen the circulation cooling

Although the equipment is used

Because item 7-1 isthe cooler due totemperature

possible to detect thesystem shutdown, the external

for reactor water injection

1 pointfunctional deterioration ofwater injection system using

cooldown and required to

DirectAWJ processing in(item 4)the coolant migrating3(multiplexing). In addition, thetransferring liquid

discharged during

the cooler through thetemperature differential

RO treated water as a water1

source is activatedoperate during retrieval
3

operations, detectability for

before and after the(multiplexing). In addition, thesignificant functionalfrom the processing

cooler, and because thiseffect of short term functional

deterioration is good

point to the cooler

trend is affected by thedeterioration or shutdown iscoming into contact④source is activated

Point ofrepresentation3amount of dust in theabrasives

An-Rei-7

1(b) The chemical

inlet

Same as above

operations, detectability fordust contained in thefrom the processing

Point

operate during retrieval
3

significant functional

composition) ofSame assource is activatedEffects on accurate and prompt
on-site response by workers(multiplexing). In addition, thechemicalSame as

Point

before and after the

point to the cooler

Same asPresence or absence ofcountermeasures for disturbing
functions

Item 7-2

Individual

The functionthat thetarget is
responsibleforDirectmonitoring/
Indirect
monitoring

Item 6-3

Impact on
throughput due toerror handling(Indirect causes)

Targetequipment

Detectionrequirements toavoid work

Item 6-2

Item 7-4(Evaluation Results)

Item 3

Reasons to be
selected

Item 6-1

Item 7-3

Item 2

Indirectcauses oferror

Item 5-2

Weighted evaluation of important monitoring items

Item 1Analysis
numberItem 4■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is unknown[3 points] Countermeasures exist, but throughput decreases significantly due
to suspension of task
[2 points] Countermeasures exist, but throughput decreases due to workload
limitations[1 point] No impact on throughput, or when 7-1 is 1 point1

3

amount of abrasives in theextremely small

with the piping inside(b) Amount oftransferring liquid flowing

When the circulation coolingContinuous monitoring is

Because item 7-1 isthe cooler, andabrasives flowing

into the cooler.

system shutdown, the externalrequired, and predictability is

1 point

causing the piping to

into cooler inlet

water injection system using

good.

3

RO treated water as a water

wear out
Indirect(item 5)1source is activated

3

1

3

(multiplexing). In addition, theeffect of short term functional
deterioration or shutdown isextremely small©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-2: Risk assessment table for safety equipment (Detailed version) (40/48)
No.181■ Risk assessment table■ Score table for item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still underdevelopment[2 points] Countermeasures exist, but there are no trackrecords of application at the Fukushima Daiichi[1 point] Countermeasures exist, and have been applied at the
Fukushima Daiichi.

(cooling equipment)
Model ID
Process

Ko-3: Debris retrieval

Work

Sa-4

: Processing of debris■ Score table for item 7-2[4 points] Requires constant monitoring during task andpredictability is poor
[3 points] Requires constant monitoring during task but
predictability is good
[2 points] Requires regular monitoring and predictability is poor
[1 point] Requires regular monitoring and predictability is good

Important monitoring items■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is unknown[3 points] Countermeasures exist, but throughput decreases significantly due tosuspension of task
[2 points] Countermeasures exist, but throughput decreases due to workload
limitations[1 point] No impact on throughput, or when 7-1 is 1 point

Weighted evaluation of important monitoring items

Item 1

Item 2Item 3Item 4Item 5-1

Item 5-2

Item 6-1

Item 6-2

Item 6-3

Targetequipment

The functionthat the target is
responsible forWork delay
factor (= error)

Direct causes of error

Indirectcauses oferror

Reasons to be selected

Detection requirements toavoid work

Directmonitoring/In
directmonitoring

Reason for selection of detection
requirements

Item 7-1

Item 7-2

Item 7-3

Item 7-4(Evaluation Results)

Impact on throughput
due to error handling(Indirect causes)

Individual

Analysis
numberPoint

Degradation of
PCV stagnant
water injection
pump

Cooldown ofdebriscooling function
due to reduced
coolant

Partial damage to theof the pump(a) PCV stagnant water

Directinjection pump flow rate

(item 4)①

An-Rei-8

Same as above

Selected because the pump flow rate

injection pump due todecreases due to the functional

An-Rei-9

Because item 7-1 is 1

predictability is poor.

point

above

Same as above

4

1

4

injection pump, and because this trend is

Supported by multiplexing and sacrificial

Although the equipment is used for PCV

Because item 7-1 is 1

affected by the chemical properties (pH,anodes. In addition, the effect of shortcooling water injection and required to

pointby dust contained in theconcentration, chemical

chloride ion concentration, chemicalterm functional deterioration oroperate during retrieval operations,

coolant migrating from thecomposition) ofcomposition) of transferring liquid flowing

shutdown is extremely small

detectability for significant functional

processing point to thetransferring liquid flowing

PCV stagnant water

into PCV stagnant water

injection pumpinjection pump inlet

Indirect(item 5)(a) PCV stagnant water

Directinjection pump flow rate

(item 4)deterioration is good

into the PCV stagnant water injection
pump.

4

1

3

1

Supported by multiplexing. In addition,

Continuous monitoring is required, but

the effect of short term functional

predictability is poor.

3

Because item 7-1 is 1
point

deterioration or shutdown is extremely
1

small

4

1

4

Selected because the pump flow rate
decreases due to the functional

entrapment of dust(b) Amount, particle size

contained in the coolant

distribution, and particle

migrating from thedensity of dust in theprocessing point to thetransferring liquid flowing

PCV stagnant water

into PCV stagnant water

injection pumpinjection pump inlet

deterioration of the PCV stagnant water
injection pump, and because this trend isaffected by the amount and particle size
distribution of dust in the transferring
Indirectliquid flowing into the PCV stagnant water(item 5)

injection pump.

Supported by multiplexing. In addition,

Although the equipment is used for PCV

Because item 7-1 is 1

the effect of short term functionalcooling water injection and required topointdeterioration or shutdown is extremely

operate during retrieval operations,small

detectability for significant functional

13

deterioration is goodPartial damage to the

Supported by multiplexing. In addition,

Continuous monitoring is required, but

pump due tothe effect of short term functional

predictability is poor.

entrapment of abrasives(a) PCV stagnant water

Directinjection pump flow rate

(item 4)discharged during AWJ

1

4

3

Because item 7-1 is 1
point

deterioration or shutdown is extremely
1

small

4

1

4

Selected because the pump flow rate

processing in the coolant④

shutdown is extremely small(pH, chloride ion

contamination and

An-Rei-10

Continuous monitoring is required, but

anodes. In addition, the effect of shortsuch as impellers caused

contamination andSame as above

Supported by multiplexing and sacrificial

Point ofrepresentationdeterioration of the PCV stagnant water

pump due toSame as above

Point(b) Chemical properties

Partial damage to theSame as above

Effects on accurate and prompt on-site
response by workers

of metal components

Same as above

Same as1

PCV stagnant water

corrosion and deformation

Same as above

Pointterm functional deterioration or
Functional deterioration

throughput

Same as above

Presence or absence ofcountermeasures for disturbing
functionsdecreases due to the functionalmigrating from the(b) Amount, particle size

deterioration of the PCV stagnant water

Supported by multiplexing. In addition,

Although the equipment is used for PCV

Because item 7-1 is 1

processing point to the

distribution, and particle

injection pump, and because this trend is

the effect of short term functionalcooling water injection and required topoint

PCV stagnant water

density of abrasives in theaffected by the amount of abrasives indeterioration or shutdown is extremely

operate during retrieval operations,injection pumptransferring liquid flowing
into PCV stagnant water
injection pumpsmall

the transferring liquid flowing into theIndirect(item 5)

PCV stagnant water injection pump.

1

4

detectability for significant functional

3

deterioration is good1

3©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-2: Risk assessment table for safety equipment (Detailed version) (41/48)
No.182■ Risk assessment table(cooling equipment)■ Score table for item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still underdevelopment[2 points] Countermeasures exist, but there are no trackrecords of application at the Fukushima Daiichi[1 point] Countermeasures exist, and have been appliedat the Fukushima Daiichi.

Model ID
Process

Ko-3: Debris retrieval

Work

Sa-4

: Processing of debris■ Score table for item 7-2[4 points] Requires constant monitoring during task andpredictability is poor
[3 points] Requires constant monitoring during task but
predictability is good
[2 points] Requires regular monitoring and predictability
is poor[1 point] Requires regular monitoring and predictability is
good

Important monitoring items
Item 2Item 3

Targetequipment

The functionthat thetarget is
responsibleforWork delay
factor (=error)

PCV

Cooldown ofDegradation

Functional

Performance(a) Water

Selected because the pump flow

stagnantdebrisof coolingdeterioration of thedegradation of thetemperature inside

rate decreases due to thefunction due

pump

pump caused by the

PCV

water

Item 4

Direct causes oferror

Item 5-1

Indirectcauses oferror

Item 5-2

Weighted evaluation of important monitoring items

Item 1Analysis
numberReasons to be
selected

Item 6-1

Detectionrequirements toavoid work

Item 6-2

Item 6-3

Directmonitoring/
Indirect
monitoring

Reason for selection of detection
requirements

Direct (itemfunctional deterioration of the

4)

D/W stagnant water transfer

injection

to reduced

coolant temperature,pumpcoolant

which is a design

pump inlet, and because thisthroughput

condition, exceeding

trend is affected by the

An-Rei-④

11

Item 7-1

Point

Presence or absence ofcountermeasures for disturbing
functions

Item 7-2

Point

Continuous monitoring is

1

addition, the effect of short termfunctional deterioration orSame as

above

above

Same as above

above

4

shutdown is extremely small

Although the equipment is used

Because item 7-1

flowing into the D/W stagnant

for PCV cooling water injectionis 1 point

result of debris

point

Supported by multiplexing. In

water transfer pump inlet.
1

Partial damage to(a) PCV stagnant

Selected because the pump flow

the pump due towater injection pumprate decreases due to theabrasives discharged

flow rate

addition, the effect of short termfunctional deterioration or

retrieval operations, detectability

14)

PCV stagnant water injection

functional deterioration or

pump, and because this trend is

shutdown is extremely small

1

addition, the effect of short term3

for significant functional
deterioration is goodContinuous monitoring isfunctional deterioration of the4

and required to operate during3

Supported by multiplexing. In

Direct (itemcoolant migrating12

is 1 point1

temperature of transferring liquid

Indirect

Point ofrepresenta
tion

poor.
4

input at processing

processing in theSame asIndividual(b) Amount of heat

during AWJ

An-Rei-

Impact on
throughput due toerror handling(Indirect causes)
Because item 7-1

required, but predictability is

Supported by multiplexing. In

shutdown is extremely small

Same as

Point

Item 7-4(Evaluation Results)

assumption, as a(item 5)above

Effects on accurate and prompt
on-site response by workers

Item 7-3

the design

retrieval operations

Same as■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is unknown[3 points] Countermeasures exist, but throughput decreases significantly due
to suspension of task
[2 points] Countermeasures exist, but throughput decreases due to workload
limitations[1 point] No impact on throughput, or when 7-1 is 1 point

Because item 7-1

required, but predictability is
4

poor.

is 1 point
1

4

affected by the amount offrom the processing(b) Amount ofabrasives in the transferring liquid

Supported by multiplexing. In

Although the equipment is used

Because item 7-1

point to the D/Wabrasives in theflowing into the PCV stagnant

addition, the effect of short termfor PCV cooling water injectionis 1 point

stagnant watertransferring liquidwater injection pump.

functional deterioration or

and required to operate during

injection pumpflowing into PCV

coming into contact

stagnant waterwith the impeller, andinjection pump

shutdown is extremely small
Indirect(item 5)1

4

retrieval operations, detectability
3

for significant functional

13

deterioration is goodcausing the impeller

to wear out©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-2: Risk assessment table for safety equipment (Detailed version) (42/48)
No.183■ Risk assessment table(cooling equipment)■ Score table for item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still underdevelopment[2 points] Countermeasures exist, but there are no trackrecords of application at the Fukushima Daiichi[1 point] Countermeasures exist, and have been appliedat the Fukushima Daiichi.

Model ID
Process

Ko-3: Debris retrieval

Work

Sa-4

: Processing of debris■ Score table for item 7-2[4 points] Requires constant monitoring during task andpredictability is poor
[3 points] Requires constant monitoring during task but
predictability is good
[2 points] Requires regular monitoring and predictability
is poor[1 point] Requires regular monitoring and predictability is
good

Important monitoring items

Weighted evaluation of important monitoring items

Item 1

Item 2Item 3Item 4Item 5-1

Item 5-2

Item 6-1

Item 6-2

Item 6-3

Targetequipment

The functionthat thetarget is
responsibleforWork delay
factor (= error)

Direct causes of
error

Indirectcauses oferror

Reasons to be
selected

Detectionrequirements toavoid work

Directmonitoring/Indirect
monitoring

Reason for selection of
detection requirements

PCV

Cooldown

Degradation of

Due to damage

stagnantof debriscooling function to the PCV

due towater

due to reduced

stagnant water

corrosion

buffercoolant

buffer tank, thecaused bytankthroughput

coolant

dust

throughput iscontained inAnalysis
numberDeterioration

reduced, and
An-Rei-the temperature13

the cooling(a) Amount of

Selected because

water in the PCV

occurrences of leaks due tostagnant water

Directdamage to the PCV

buffer tank +(item 4)

stagnant water buffer tankamount ofwhich makes it impossible

leakageto secure a water source for(b) Chemical

inside the PCV

migratingproperties (pH,

PipingSame asflow rate ofabove

coolant in thesystemAn-Rei14

Point

1

Presence or absence ofcountermeasures for
disturbing functions

Item 7-2

Point

Effects on accurate andprompt on-site response byworkers

Item 7-3

Point

Impact on
throughput
due to error
handling(Indirect
causes)Although there isWith constant monitoring

Becauseimpact on safetyof the flow rate in theitem 7-1 isfunctions, thesystem and leakfrequency of3detection, post-detection

occurrence isis possible, andexpected to be low.

detectability is good.

deviates fromfrom thechloride ion

the control

processing

concentration,

value.

point to thechemicalPCV

composition) ofstagnant

coolant flowing

water buffer

into liquid system

the coolant throughput inthe system, and because
this trend is affected by the
Indirect

chemical properties (pH,(item 5)chloride ion concentration,

Constant monitoring is

Becauserequired because theitem 7-1 isequipment is related to

1 point

1

Same as above

4

predictability is poor.

1

4

dust flowing into the PCV
stagnant water buffer tank.
Detection of trends andBecausetrend toward

post-detection are

item 7-1 isblockage, it can be

possible throughblockagethe flow rate ofdue tocoolant in theaccumulatio

system is notn of dust

ensured,①(a) Flow rate in

DirectSelected because the flow

the system(item 4)rate in the system

1

handled by flushing3

the piping.

from theparticle size

temperatureprocessing

distribution, andinside the PCV

point to theparticle density of

to deviate frompipingdust in thethe control

coolant flowing

value.

into piping

4
Becauseamount and particle size
Constant monitoring is

distribution of dust in the
Indirect

coolant flowing into the(item 5)piping3

is good.

this trend is affected by the

resulting in the

1 point1

system, and detectability

in the piping, and because(b) Amount,

constant monitoring of
the flow rate in thedecreases due to blockage

migrating4

confinement, but

If there is a significant

design value for

Point ofrepresentation

3

deterioration ofPartialIndividual

1 point1

Due tothe piping, theItem 7-4(Evaluation Results)

chemical composition) oftank

Decrease in the

Item 7-1

the cooling system, reduces

water

①

■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is unknown[3 points] Countermeasures exist, but throughput decreases significantly due
to suspension of task
[2 points] Countermeasures exist, but throughput decreases due to workload
limitations[1 point] No impact on throughput, or when 7-1 is 1 point

item 7-1 isrequired because the1Same as above4

equipment is related to

1 point
14cooling, but predictability
is poor.

©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-2: Risk assessment table for safety equipment (Detailed version) (43/48)
No.184■ Risk assessment table(cooling equipment)■ Score table for item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still underdevelopment[2 points] Countermeasures exist, but there are no trackrecords of application at the Fukushima Daiichi[1 point] Countermeasures exist, and have been applied at the
Fukushima Daiichi.

Model ID
Process

Ko-3: Debris retrieval

Work

Sa-4

: Processing of debris■ Score table for item 7-2[4 points] Requires constant monitoring during task andpredictability is poor
[3 points] Requires constant monitoring during task but
predictability is good
[2 points] Requires regular monitoring and predictability is poor
[1 point] Requires regular monitoring and predictability is good

Important monitoring items

Weighted evaluation of important monitoring items

Item 1

Item 2Item 3Item 4Item 5-1

Item 5-2

Item 6-1

Item 6-2

Item 6-3

Targetequipment

The functionthat thetarget is
responsibleforWork delay
factor (=error)

Direct causes of
error

Indirectcauses oferror

Reasons to be
selected

Detectionrequirements toavoid work

Directmonitoring/
Indirect
monitoring

Reason for selection of detection
requirements

PipingCooldown of

Decrease in

Due to leakage

debristhe flow ratecaused byof coolant indeterioration of thePartial damage due

the systempiping, the coolant

to corrosion caused

throughput isby potential

Analysis
number

An-Rei-reduced, and the15①(a) Flow rate in thesystem + amount ofleakage

Item 7-1

Point

Presence or absence ofcountermeasures for
disturbing functions

Item 7-2

Point

DirectSelected because occurrences of(item 4)leaks due to damage to the1piping reduces the flow rate ofdifference resulting

on safety functions, thefrequency of occurrence isthe PCV deviates

dust migrating fromsize distribution, andfrom the control

the processing point

particle density ofIndirect

distribution of dust flowing intovalue.

to the piping

dust in the coolant(item 5)the piping.

Point

Impact on throughput due toerror handling (Indirectcauses)1

Because item 7-1 is 1 point

Item 7-4(Evaluation
Results)
PointofIndivirepresdual
entationflow rate in the system and leak3

detection, post-detection is3

possible, and detectability is

expected to be low.

good.

coolant in the system, andfrom accumulation of

Effects on accurate and prompt
on-site response by workers

Item 7-3

With constant monitoring of the

Although there is impact(b) Amount, particle

temperature inside■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is unknown[3 points] Countermeasures exist, but throughput decreases significantly due tosuspension of task
[2 points] Countermeasures exist, but throughput decreases due to workload
limitations[1 point] No impact on throughput, or when 7-1 is 1 point

4

because this trend is affected byConstant monitoring is required

the amount and particle size
1Same as above

4

flowing into liquidbecause the equipment is related
to cooling, but predictability is

1

Because item 7-1 is 1 point

4

1

Because item 7-1 is 1 point

3

poor.

system(a) Flow rate in theSame asSame asSame as

above

above

above

system + amount ofSame as above

Partial damage due

leakage

Direct(item 4)to corrosion caused
An-Rei-Same as16

aboveWith constant monitoring of the

Although there is impact
Selected because occurrences of1

leaks due to damage to theon safety functions, thefrequency of occurrence isflow rate in the system and leak3

piping reduces the flow rate ofdetection, post-detection ispossible, and detectability is

expected to be low.

good.

by changes in the(b) Chemicalcoolant in the system, andwater quality of theproperties (pH,because this trend is affected bycoolant migrating

chloride ion

the chemical properties (pH,from the processing

concentration,

Indirectchloride ion concentration, andpoint to the piping

chemical(item 5)chemical composition) of dust

to cooling, but predictability is

flowing into the piping.

poor.

composition) of

Because item 7-1 is 1 point
4
Constant monitoring is required
1

Same as above4

because the equipment is related

1

4

coolant flowing into
liquid system
Due topiping, the design
PipingStaticboundarySame asabove

value for the flowrate of coolant inensured, resulting

17

in the temperatureinside the PCV todeviate from thecontrol value.

Directsystem(item 4)

Partial blockage due

the system is not
An-Rei-(a) Flow rate in the④

1

can be handled by flushing

the system decreases due tothe piping.

to accumulation of(b) Amount, particle

blockage in the piping, andabrasives migrating

size distribution, andbecause this trend is affected byfrom the processing

particle density of

the amount and particle size

point to the piping

abrasives in thetransferring liquid
flowing into piping

trend toward blockage, it

Selected because the flow rate indetection are possible through3(item 5)transferring liquid flowing into thepipingconstant monitoring of the flow

1

3

rate in the system, anddetectability is good.
Because item 7-1 is 1 point
4
Constant monitoring is required

distribution of abrasives in the
Indirect

Because item 7-1 is 1 point

Detection of trends and post-

If there is a significant

deterioration of the

1

Same as above4

because the equipment is related
to cooling, but predictability is

1

4

poor.

©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-2: Risk assessment table for safety equipment (Detailed version) (44/48)
No.185■ Risk assessment table■ Score table for item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still underdevelopment[2 points] Countermeasures exist, but there are no trackrecords of application at the Fukushima Daiichi[1 point] Countermeasures exist, and have been applied at the
Fukushima Daiichi.

(cooling equipment)
Model ID
Process

Ko-3: Debris retrieval

Work

Sa-4

: Processing of debris■ Score table for item 7-2[4 points] Requires constant monitoring during task andpredictability is poor
[3 points] Requires constant monitoring during task but
predictability is good
[2 points] Requires regular monitoring and predictability is poor
[1 point] Requires regular monitoring and predictability is good

Important monitoring items■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is unknown[3 points] Countermeasures exist, but throughput decreases significantly due tosuspension of task
[2 points] Countermeasures exist, but throughput decreases due to workload
limitations[1 point] No impact on throughput, or when 7-1 is 1 point
Weighted evaluation of important monitoring items

Item 1

Item 2Item 3Item 4Item 5-1

Item 5-2

Item 6-1

Item 6-2

Item 6-3

Targetequipment

The function thatthe target is
responsible forWork delay
factor (= error)

Direct causes of error

Indirectcauses oferror

Reasons to be selected

Detection requirements toavoid work

Directmonitoring/Ind
irect
monitoring

Reason for selection of detection
requirements

Static boundary

Item 7-1

Item 7-2

Item 7-4(Evaluation
Results)

Item 7-3

Analysis
numberValvesDecrease in the

Due to leakage caused(Integration offlow rate of

by deterioration of thevalves present

coolant in thevalve, the coolant

in the system)

systemthroughput is reduced,(a) Flow rate in theand the temperaturesystem + amount of

inside the PCV deviates

leakagemigrating from theprocessing point to thevalve

Same as above

because this trend is affected by thedetection is possible, and detectability is

1

3

4

concentration, chemical composition) ofconcentration, chemical

dust flowing into the liquid-phase system.

composition) of coolant

Indirectflowing into liquid system(item 5)throughput is reduced,(a) Flow rate in theand the temperaturesystem + amount of

inside the PCV deviates

leakage4

Because item 7-1 is 1 point

chemical properties (pH, chloride ion(pH, chloride ion

Constant monitoring is required because
1Same as above

the equipment is related to cooling, but

Direct3

4

Because item 7-1 is 1 point

With constant monitoring of the flow ratein the system and leak detection, post-

1(item 4)detection is possible, and detectability is

Selected because the flow rate of coolant

Adhesion of the valve due

1predictability is poor.

expected to be low.

1

3

good.

in the system decreases due to blockage

to accumulation ofvalve

Point ofrepresentationflow rate of coolant in the system, and(b) Chemical propertiesfunctions, the frequency of occurrence isthe processing point to theIndividual

due to damage to the valve reduces the

Although there is impact on safetyabrasives migrating from

Impact on throughput due toerror handling (Indirectcauses)good.

valve, the coolant④

resulting from adhesion of the valve, andbecause this trend is affected by the(b) Amount, particle size

44Because item 7-1 is 1 point

chemical properties (pH, chloride ion

distribution, and particle

concentration, chemical composition) of

density of abrasives in the

dust flowing into the liquid-phase system.

coolant flowing into liquid

Indirect

system(item 5)Constant monitoring is required because
1Same as above

the equipment is related to cooling, but

Decrease in the

Due to deterioration ofPartial blockage due to(a) Flow rate in the

Select because the flow rate in the system

Because the cyclone is structured so

flow rate of

the D/W stagnant water

accumulation of dust

system + differential

decreases due to blockage of the D/Wthat dust does not easily accumulate, theare possible through constant monitoring

particles

coolant in thecoarse particle removal

migrating from thepressure before and after

stagnant water coarse particle removal

frequency of occurrence is low, andof the flow rate in the system and theremovalsystemequipment, the design

processing point to theD/W stagnant waterequipment, and because this trend isbecause the auto-strainer automaticallydifferential pressure before and after thevalue for the flow rate of

D/W stagnant watercoarse particle removal

affected by the amount and particle size

discharges the contaminants after a

D/W stagnant water coarse particle

coolant in the system iscoarse particle removal

equipment

distribution of dust in the coolant flowing

blockage is detected, the impact onremoval equipment, and detectability is

not ensured, resulting inequipment

safety functions is considered to be

good.

Direct(item 4)the temperature inside

1

4

predictability is poor.

water coarse

equipment

Point

Because item 7-1 is 1 pointin the system and leak detection, post-

expected to be low.

Selected because occurrences of leaks

by deterioration of thefrom the control value.

Static boundary

Effects on accurate and prompt on-site
response by workers

With constant monitoring of the flow ratefunctions, the frequency of occurrence is

Due to adhesion caused

An-Rei-19

D/W stagnant

1(item 4)

corrosion caused by dustSame as above

Point

Although there is impact on safety

DirectPartial damage due to①

Same as above

Presence or absence ofcountermeasures for disturbing functions

3

from the control value.
An-Rei-18

Point

into the D/W stagnant water coarse

1

particle removal equipment3

Detection of trends and post-detection

Because item 7-1 is 1 point

1

3

small.

the PCV to deviate fromthe control value.
An-Rei-20①

4(b) Amount, particle size

4

Constant monitoring is required because

distribution, and particle

the equipment is related to confinement,

density of dust in thebut predictability is poor.

coolant flowing into D/WIndirectstagnant water coarse(item 5)1Same as above

Because item 7-1 is 1 point

1

4

particle removal
equipment©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-2: Risk assessment table for safety equipment (Detailed version) (45/48)
No.186■ Risk assessment table■ Score table for item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still underdevelopment[2 points] Countermeasures exist, but there are no trackrecords of application at the Fukushima Daiichi[1 point] Countermeasures exist, and have been applied at the
Fukushima Daiichi.

(cooling equipment)
Model ID
Process

Ko-3: Debris retrieval

Work

Sa-4

: Processing of debris■ Score table for item 7-2[4 points] Requires constant monitoring during task andpredictability is poor
[3 points] Requires constant monitoring during task but
predictability is good
[2 points] Requires regular monitoring and predictability is poor
[1 point] Requires regular monitoring and predictability is good

Important monitoring items■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is unknown[3 points] Countermeasures exist, but throughput decreases significantly due tosuspension of task
[2 points] Countermeasures exist, but throughput decreases due to workload
limitations[1 point] No impact on throughput, or when 7-1 is 1 point

Weighted evaluation of important monitoring items

Item 1

Item 2Item 3Item 4Item 5-1

Item 5-2

Item 6-1

Item 6-2

Item 6-3

Targetequipment

The function thatthe target is
responsible forWork delay
factor (= error)

Direct causes of error

Indirectcauses oferror

Reasons to be selected

Detection requirements toavoid work

Directmonitoring/Ind
irect
monitoring

Reason for selection of detection
requirements

D/W stagnant

Static boundary

Analysis
numberItem 7-1

Point

Presence or absence ofcountermeasures for disturbing functions

Item 7-2

Point

Effects on accurate and prompt on-site
response by workers

Decrease in the

Due to deterioration ofPartial damage due to(a) Flow rate in the

Selected because leaks occur due to

Because the cyclone is structured soWith constant monitoring of the flow ratewater coarse

flow rate of

the D/W stagnant water

corrosion caused bysystem + amount ofdamage to the D/W stagnant waterthat dust does not easily accumulate, thein the system and leak detection, post-

particles

coolant in thecoarse particle removal

potential difference

leakagecoarse particle removal equipment, andfrequency of occurrence is low, anddetection is possible, and detectability isremovalsystemequipment, leaks occur,

resulting frombecause this trend is affected by the

because the auto-strainer automaticallygood.

and the temperatureaccumulation of dust

chemical properties (pH, chloride ion

discharges the contaminants after ainside the PCV deviates

migrating from theconcentration, and chemical composition)

blockage is detected, the impact on

from the control value.

processing point to theequipment

Direct(item 4)1of coolant flowing into the liquid system

3

Item 7-3

Point

Impact on throughput due toerror handling (Indirectcauses)Item 7-4(Evaluation
Results)
Individual

Point ofrepresentationBecause item 7-1 is 1 point

1

3

safety functions is considered to be

D/W stagnant water

small.

coarse particle removal①

An-Rei-21

4equipment(b) Amount, particle size

Constant monitoring is required because

distribution, and particle

the equipment is related to confinement,

density of dust in the

Because item 7-1 is 1 point

but predictability is poor.

coolant flowing into D/WIndirectstagnant water coarse(item 5)1Same as above

4

1

4

particle removal
equipment

Same as above

Same as above

Same as above

Same as above

Partial damage due to(a) Flow rate in the

corrosion caused bysystem + amount ofchanges in the waterleakagequality of stagnant water

Selected because leaks occur due to
Direct(item 4)migrating from theAn-Rei-22

The impact on safety functions is small,damage to the D/W stagnant watercoarse particle removal equipment, andWith constant monitoring of the flow rate

and the frequency of occurrence is1

expected to be low.

Because item 7-1 is 1 pointin the system and leak detection, post3

because this trend is affected by thedetection is possible, and detectability is

1

3

good.

chemical properties (pH, chloride ionprocessing point to the(b) Chemical properties

concentration, and chemical composition)

Constant monitoring is required because

Same asD/W stagnant water(pH, chloride ionof coolant flowing into the liquid system

the equipment is related to confinement,

abovecoarse particle removal

concentration, chemical

equipment

composition) of coolant
flowing into D/W stagnant

Because item 7-1 is 1 point4

but predictability is poor.

Indirect1(item 5)Same as above

4

1

4

water coarse particle

removal equipment

Same as above

Same as above

Same as above

Due to deterioration ofPartial blockage due to(a) Flow rate in the

Selected because the flow rate in the

Because the cyclone is structured so

Detection of trends and post-detection

the D/W stagnant water

accumulation of abrasives

system + differential

system decreases due to blockage of thethat dust does not easily accumulate, theare possible through constant monitoringcoarse particle removal

migrating from thepressure before and after

D/W stagnant water coarse particle

frequency of occurrence is low, andof the flow rate in the system and theequipment, the design

processing point to theD/W stagnant water

removal equipment, and because thisbecause the auto-strainer automaticallydifferential pressure before and after thevalue for the flow rate of

D/W stagnant watercoarse particle removal

trend is affected by the amount anddischarges the contaminants after acoolant in the system iscoarse particle removal

not ensured, resulting inequipment

Direct(item 4)equipment

particle size distribution of dust in the1

coolant flowing into the liquid system

blockage is detected, the impact on

D/W stagnant water coarse particle
3

safety functions is considered to be

the temperature inside

Because item 7-1 is 1 point

removal equipment, and detectability is

1

3

good.

small.

the PCV to deviate from
An-Rei-23

the control value.

④

4(b) Amount, particle size

Constant monitoring is required because

distribution, and particle

the equipment is related to confinement,

density of abrasives in the

Because item 7-1 is 1 point

but predictability is poor.

coolant flowing into liquid

Indirect

system(item 5)1Same as above

4

1

4

©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-2: Risk assessment table for safety equipment (Detailed version) (46/48)
No.187■ Risk assessment table(liquid phase/sub-criticality maintenance equipment)■ Score table for item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still
under development[2 points] Countermeasures exist, but there are no trackrecords of application at the Fukushima Daiichi[1 point] Countermeasures exist, and have been
applied at the Fukushima Daiichi.

Model ID
Process

Ko-3: Debris retrieval

Work

Sa-4

: Processing of debris■ Score table for item 7-2[4 points] Requires constant monitoring
during task and predictability is poor
[3 points] Requires constant monitoring
during task but predictability is good
[2 points] Requires regular monitoring andpredictability is poor
[1 point] Requires regular monitoring andpredictability is good

Important monitoring items■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is
unknown[3 points] Countermeasures exist, but throughput decreases
significantly due to suspension of task
[2 points] Countermeasures exist, but throughput decreases
due to workload limitations[1 point] No impact on throughput, or when 7-1 is 1 point

Weighted evaluation of important monitoring items

Item 1

Item 2Item 3Item 4Item 5-1

Item 5-2

Item 6-1

Item 6-2

Item 6-3

Targetequipment

The functionthat thetarget is
responsibleforWork delay
factor (=error)

Direct causes of
error

Indirectcauses oferror

Reasons to be
selected

Detectionrequirements toavoid work

Directmonitoring/Indirect
monitoring

Reason for selection of
detection requirements

D/W

Criticality

Approaching

Due toPartial damage to(a) Amount andSelected because large

The impact on safety functions

Post-detection is possible from

Because item 7-1 is 1

stagnant

prevention

Criticality

deterioration of thethe mesh of the filter

particle size

particles pass through the D/W

is small, and the frequency of

the amount and particle size

point

water

D/W stagnant

section in the

distribution of dust

stagnant water coarse particle

occurrence is expected to be

distribution of dust downstreamcoarsewater coarse

equipment due todownstream of D/Wparticles

particle removal

contact with dust

stagnant water

removalequipment, themigrating from theequipment

design value forprocessing point toremoved particle

Analysis
numberAn-Rin-1

Direct(item 4)

removal equipment due to

Item 7-1

Poin
t

1

Presence or absence ofcountermeasures for disturbing
functionslow.

Item 7-2

Poin
t

4

Effects on accurate and prompt
on-site response by workersof the D/W stagnant water

Item 7-3

Point

Impact on throughput
due to error handling(Indirect causes)

1

4

damage to the equipment, andcoarse particle removal

coarse particle

because this trend is affected byequipment, but detectability isremoval equipment

the amount and particle size

poor.

the D/W stagnant(b) Amount of dust

distribution of dust in theConstant monitoring is required

Because item 7-1 is 1

water coarse

in the transferringtransferring liquid flowing into

because the equipment ispoint

ensured, and theparticle removal

liquid flowing into

the D/W stagnant water coarse

related to criticality prevention,

accumulation ofequipment (in theD/W stagnant waterparticles in thecase of an auto-coarse particle

PCV stagnant

strainer)removal equipment

Partial damage to(a) Amount andSelected because large

The impact on safety functions

Post-detection is possible from

Because item 7-1 is 1

the mesh of the filter

particle size

particles pass through the D/W

is small, and the frequency of

the amount and particle size

point

section in the

distribution of dust

stagnant water coarse particle

occurrence is expected to be

distribution of dust downstream

equipment due todownstream of D/W

corrosion caused bystagnant water

the potential
difference resulting

Same asabove

size is not①1(item 5)4

but predictability is poor.

particle removal equipment
Indirect

Item 7-4(Evaluation
results)
Point
of
Indiv
represidual
entationSame as above

4

1

4

water buffer tankincreases,
approaching
criticality.

An-Rin-2Same asSame asSame as

above

above

above

Same as above

Direct(item 4)

removal equipment due to

1

low.

4

of the D/W stagnant water

1

4

damage to the equipment, andcoarse particle removal

coarse particle

because this trend is affected byequipment, but detectability isremoval equipment

the amount and particle size

poor.

from accumulation(b) Amount, particle

distribution of dust in theConstant monitoring is required

Because item 7-1 is 1of dust migrating

size distribution,transferring liquid flowing into

because the equipment is

pointfrom the processing

and particle density

the D/W stagnant water coarse

related to criticality prevention,

point to the D/Wof dust in thestagnant watertransferring liquidcoarse particle

flowing into D/Wremoval equipment

stagnant water(in the case of ancoarse particle

auto-strainer)

removal equipment

Indirect(item 5)4

but predictability is poor.

particle removal equipment
1

Same as above

4

1

4

©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-2: Risk assessment table for safety equipment (Detailed version) (47/48)■ Risk assessment table (liquid phase/subNo.188■ Score table for item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still under development[2 points] Countermeasures exist, but there are no track records of application
at the Fukushima Daiichi[1 point] Countermeasures exist, and have been applied at the Fukushima
Daiichi.

criticality maintenance equipment)
Model ID
Process

Ko-3: Debris retrieval

Work

Sa-4

: Processing of debris■ Score table for item 7-2[4 points] Requires constant monitoring during task andpredictability is poor
[3 points] Requires constant monitoring during task but
predictability is good
[2 points] Requires regular monitoring and predictability is poor
[1 point] Requires regular monitoring and predictability is good

Important monitoring items
Item 1Analysis
numberItem 2Item 3Item 4Item 5-1

Item 5-2■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is unknown[3 points] Countermeasures exist, but throughput decreases
significantly due to suspension of task
[2 points] Countermeasures exist, but throughput decreases due toworkload limitations[1 point] No impact on throughput, or when 7-1 is 1 point

Weighted evaluation of important monitoring items
Item 6-1

Item 6-2

Item 6-3

Item 7-1

Item 7-2

Thefunctionthat thetarget is
responsi
ble forWork delay
factor (=error)

Direct causes of error

D/W

Criticali

Approachin

Due to deterioration of thePartial damage to the(a) Amount and particle

Selected because large particles

The impact on safety functions is

Post-detection is possible from thestagnanttyg Criticality

D/W stagnant water coarse

mesh of the filter section

size distribution of dust

pass through the D/W stagnant

small, and the frequency ofamount and particle size

water coarse

prevent

particle removal equipment,in the equipment due todownstream of D/W

Directwater coarse particle removal

particlesion

the design value forcorrosion caused bystagnant water coarse(item 4)equipment due to damage to theremovalremoved particle size is notchanges in the waterparticle removal equipment

equipment

ensured, and theTargetequipment

An-Rin-3

Indirectcauses oferror

Reasons to be selected

Detection requirements to avoid
work

Directmonitoring/
Indirect
monitoring

Point

1

Presence or absence of countermeasuresfor disturbing functions

occurrence is expected to be low.

Point

4

Effects on accurate and prompt on-site
response by workers

distribution of dust downstream of
the D/W stagnant water coarse

equipment, and because this trend

particle removal equipment, but

Point

Impact on
throughput
due to error
handling(Indirect
causes)1 point

is affected by the chemical

detectability is poor.

properties (pH, chloride ion

Constant monitoring is required

Becausethe PCV stagnant water

processing point to the(pH, chloride ion

concentration, chemical

because the equipment is related

item 7-1 isbuffer tank increases,

D/W stagnant water

concentration, chemical

approaching criticality.

coarse particle removal

composition) of transferring

equipment (in the case of

liquid flowing into D/W

an auto-strainer)

stagnant water coarse

Indirect(item 5)to criticality prevention, but

composition) of transferring liquid
flowing into the D/W stagnant water

1

Same as above

4

predictability is poor.

Individual

Point ofrepresentationitem 7-1 is
1(b) Chemical properties①

Item 7-4(Evaluation
results)

Becausewater migrating from theaccumulation of particles inquality of the stagnant

Reason for selection of detection
requirements

Item 7-3

4

4

1 point
1

4coarse particle removal equipment

particle removal equipment

Same as
above

Same
as
above

Same asabove

Same as above

Same asAn-Rin-4

above

Decrease in the efficiency(a) Amount and particle

Selected because large particles

The impact on safety functions is

Post-detection is possible from the

Becauseof centrifugal removal

size distribution of dust

pass through the D/W stagnant

small, and the frequency ofamount and particle size

item 7-1 isresulting from insufficient

downstream of D/W

Directwater coarse particle removal

occurrence is expected to be low.

distribution of dust downstream offlow rate in the equipment

stagnant water coarse(item 4)equipment due to damage to thecaused by increased

particle removal equipment

density of the transferring

1

4

the D/W stagnant water coarse

equipment, and because this trend

particle removal equipment, but

1

1 point

is affected by the amount anddetectability is poor.

liquid due to dust(b) Amount, particle size

particle size distribution of dust inConstant monitoring is required

Becausemigrating from the

distribution, and particle

the transferring liquid flowing into

because the equipment is related

item 7-1 isprocessing point to thedensity of dust in theD/W stagnant watertransferring liquid flowing

coarse particle removal

into D/W stagnant waterequipmentcoarse particle removal

Indirect(item 5)to criticality prevention, but

the D/W stagnant water coarse
particle removal equipment

1

Same as above

4

predictability is poor.

4

4

1 point14equipment

Same asabove

An-Rin-5

Same
as

above

Same asabove

Same as above

Partial damage to the(a) Amount and particle

Selected because large particles

Because the cyclone is structured

Detection of trends and post-

Becausemesh of the filter section

size distribution of dust

pass through the D/W stagnant

so that dust does not easily

detection are possible throughitem 7-1 isin the equipment due todownstream of D/Wwater coarse particle removal

accumulate, the frequency ofconstant monitoring of the flow rate

1 point

contact with abrasives

stagnant water coarse

equipment due to damage to theoccurrence is low, and because

in the system and the differential

migrating from theparticle removal equipment

Directequipment, and because this trend(item 4)

is affected by the amount anddischarges the contaminants after

stagnant water coarse particle

D/W stagnant waterparticle size distribution ofa blockage is detected, the impact

removal equipment, andcoarse particle removal

abrasives in the transferring liquidon safety functions is considered

detectability is good.

equipment (in the case offlowing into the D/W stagnant water

to be small.

processing point to the④

1

the auto-strainer automatically3

pressure before and after the D/W

1

3

4

Constant monitoring is required

Because(b) Amount of abrasives inbecause the equipment is related

item 7-1 isthe transferring liquid

to criticality prevention, but

an auto-strainer)coarse particle removal equipment

flowing into D/W stagnant

Indirectwater coarse particle(item 5)1Same as above

4

predictability is poor.

1 point
1

4

removal equipment©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-2: Risk assessment table for safety equipment (Detailed version) (48/48)■ Risk assessment table
No.189(liquid phase/sub-criticality maintenance equipment)■ Score table for item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still underdevelopment[2 points] Countermeasures exist, but there are no trackrecords of application at the Fukushima Daiichi[1 point] Countermeasures exist, and have been applied at the
Fukushima Daiichi.

Model ID
Process

Ko-3: Debris retrieval

Work

Sa-4

: Processing of debris■ Score table for item 7-2[4 points] Requires constant monitoring during task andpredictability is poor
[3 points] Requires constant monitoring during task but
predictability is good
[2 points] Requires regular monitoring and predictability is poor
[1 point] Requires regular monitoring and predictability is good

Important monitoring items
Item 1

Item 2Item 3Item 4

Targetequipment

The functionthat the target Work
delay Direct
is responsible factor (= error) error
for

Item 5-1■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is unknown[3 points] Countermeasures exist, but throughput decreases significantly due tosuspension of task
[2 points] Countermeasures exist, but throughput decreases due to workload
limitations[1 point] No impact on throughput, or when 7-1 is 1 point
Weighted evaluation of important monitoring items

Item 5-2

Item 6-1

Item 6-2

Item 6-3

Item 7-1

Item 7-2

Item 7-3

Analysis
numbercausesofIndirectcauseserror

ofReasons
selectedtobeDirectDetection
monitoring/I
requirements to avoidndirect
work
monitoring

Reason for selection of detection
Point
requirements

Presence or absence ofcountermeasures for disturbing
functions

Point

Impact on throughput
Point ofEffects on accurate and prompt onIndivid
Point due to error handling
represesite response by workers
ual(Indirect causes)
ntationD/W stagnant Criticality

Approaching

Due to deterioration

Partial damage to the(a) Amount andSelected because large particles

The impact on safety functions is

Post-detection is possible from the

Because item 7-1 is 1

water coarse

Criticalityof the D/W stagnant

mesh of the filter

particle size

pass through the D/W stagnant

small, and the frequency ofamount and particle size

pointparticles

water coarse particle

section in the

distribution of dust

water coarse particle removal

occurrence is expected to be low.

distribution of dust downstream ofremovalremoval equipment,

equipment due todownstream of D/Wequipment

the design value forcorrosion caused bystagnant water coarse 4)

removed particle size
is not ensured, andprevention

the accumulation ofparticles in the PCV

An-Rin-6

1

4

the D/W stagnant water coarse
particle removal equipment, but

the potential difference particle removal

is affected by the amount anddetectability is poor.

resulting fromparticle size distribution ofabrasives migrating

stagnant water bufferfrom the processing

tank increases,

point to the D/W

approachingstagnant water coarse

criticality.

equipment due to damage to theequipment, and because this trend

accumulation of④

Direct (itemparticle removal
equipment (in the caseof an auto-strainer)

equipmentabrasives in the transferring liquid(b) Amount, particle

flowing into the D/W stagnant

size distribution, andwater coarse particle removal

particle density oftransferring liquid

Indirectflowing into D/W(item 5)1

4Constant monitoring is required

Because item 7-1 is 1

because the equipment is related

point

4

to criticality prevention, but

equipmentabrasives in the

Item 7-4(Evaluation
results)

predictability is poor.
1

Same as above

4

1

4

stagnant water coarse
particle removal
equipment

Same asSame asSame as

above

above

above

Decrease in the(a) Amount andSelected because large particles

The impact on safety functions is

Post-detection is possible from the

Because item 7-1 is 1

efficiency ofparticle size

pass through the D/W stagnant

small,

amount and particle size

point

centrifugal removal

distribution of dust

water coarse particle removal

occurrence is expected to be low.

frequencyof

distribution of dust downstream ofequipment due to damage to theequipment, and because this trend

particle removal equipment, but

the equipment caused particle removal

is affected by the amount anddetectability is poor.

by increased density

particle size distribution ofof the transferring
An-Rin-7

theDirect (itemdownstream of D/W
insufficient flow rate in stagnant water coarse 4)
resulting from

Same as above

andSame asliquid due to abrasives

above

migrating from theprocessing point to theD/W stagnant watercoarse particle
removal equipment

equipment

1

4abrasives in the transferring liquid(b) Amount, particle

flowing into the D/W stagnant

size distribution, andwater coarse particle removal

particle density oftransferring liquid

Indirectflowing into D/W(item 5)1

4Constant monitoring is required

Because item 7-1 is 1

because the equipment is related

point

4

to criticality prevention, but

equipmentabrasives in thethe D/W stagnant water coarse

predictability is poor.
1

Same as above

4

1

4

stagnant water coarse
particle removal
equipment©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-3: Risk assessment table for operational equipment (Detailed version) (1/59)

No.190■ Supplemental information prior to presentation of assessment results: Additional procedures specific towork equipment prior to risk assessment• Unlike safety equipment, work equipment combines multiple actions to perform work within the PCV. For example, thework of "processing fuel debris" consists of repetition of check and action operations (operation group) as shown in
STEP 2 below.
• Check items are defined as determining the nature of the next action (e.g. whether to use a disk cutter or AWJ for fueldebris processing) or execution/non-execution (e.g. whether to process with a disk cutter, etc.) do.
• Work equipment risk assessments are performed separately for groups of actions. Therefore, as a pre-stage of risk
assessment, it is necessary to define a group of actions for each task (so-called task separation).
• The procedure for performing work separation and risk assessment is shown below. See the following pages for
specific work methods.

Classification of work steps
STEP 1: Work step definition

ID

Work Name
Verification of the overallsituation andSa-1
operational/safety
equipment inside the PCVApproaching the object toSa-2
be processed
Work prior to debris
Sa-3
processing
Sa-4 Processing of debris
Various records following
Sa-5
processing work
Sa-6 Cell transfer of debris
Sa-7 Transfer of debris ①
Sa-8 Collection of debris
Sa-9 Transfer of debris ②
SaTransfer of debris
10

Risk assessment

STEP 2: Action group definitionIDi (check)ii (action)iii (check)

Step 3:
Step 4:
Setting work delay factors (=errors) Entry into the risk assessment table

Action group
Determine the method for debris
processing
Debris processing(cutting/chipping/crushing/picking
up)
Verify if the debris has beenprocessed as expectediv (action)

Debris is stored in the innercontainerv (check)

Check whether debris is safely
stored in the inner container
Input for action group definition

Equipment configuration block diagram, table ofoperational functions, table of safety functions[Error analysis table]
Set factors that delay
work for each action[Risk evaluationtable]
From STEP4
onwards, the flow is
the same as for risk
assessment ofsafety equipment.

Input for work delay factor extraction

List of disturbances to work equipment©International Research Institute for Nuclear DecommissioningAttachment 6.2.4.3-3: Risk assessment table for work equipment (detailed version) (2/59)

No.191■ Risk assessment procedures specific to operational equipment• The execution procedure of STEP 1 and 2 shown on the previous page is shown.
〇Step 1 of work

〇 Work detail sheet to determine the attributes of theaction group in STEP2(2) Enter ID items a to k
based on the debris retrieval
model information.

Work Name
Verification of the overall
Sa-1 situation and operational/safety
equipment inside the PCVApproaching the object to be
Sa-2
processed

ID attributea Goalb Environment

Sa-3 Work prior to debris processinge Targetf preceding workg Work start condition

Debris (fuel, fuel debris mass (U-rich, Fe-rich), existing structures, MCCI formations)h Action group

Refer to action group sheetiCompletion of debris storage in the inner vesselID

C Safetyd Components

Sa-4 Processing of debris
Various records following
Sa-5
processing work
Sa-6 Cell transfer of debris
Sa-7 Transfer of debris ①
Sa-8 Collection of debris

End of work condition

Concrete actions
Debris is finely divided and stored in the inner container
Inside the PCV[Gas phase] Dust scattering prevention function, PCV damage prevention function, debris overheating
prevention function, [Criticality] Debris shape control function[Debris processing equipment] Debris processing mechanism, [Debris sealed storage/transfer equipment]
Radiation source storage mechanism
ID: Sa3
Condition 1: Successful completion of preceding work

j Takeover next work

Delivery of the inner container containing debris (*Refer to item k)k Others

Debris stored in the inner container maintains a subcritical state

Sa-9 Transfer of debris ②(3) Set a group of actions toachieve the contents
described in ID a and i

Sa-10 Transfer of debris(1) Select one work to beanalyzed from the work steps.

〇 Operation group sheet for STEP2
ID Movementi (check)

Remarks
Determine the processing method for <target>ii (action)

Processing (cutting/cracking/crushing/picking up) of<target> by <equipment: debris processing mechanism>iii (check)

Confirm the processing result of <target>iv (action)

Store <target> in <equipment: inner container> with<equipment: radiation source storage mechanism>v (check)

Safety confirmation of <target: debris> stored in the innercontainer

Confirmation of processing results: Refers to confirming
whether the debris has been subdivided to a size thatfits in the inner container.

Safety confirmation: Refers to confirmation that debris is
not spilled from the inner container and that the
subcritical state is maintained.
©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-3: Risk assessment table for operational equipment (Detailed version) (3/59)

No.192■ Risk assessment procedures specific to operational equipment•
The procedures for executing STEP 2 to 3 shown on page 1/59 of this Appendix is described.
•
The word “error” used in this document is synonymous with work delay factor.
〇 STEP2 Action group (reprint of previous page)

Deploy the error analysis sheet
for each defined action

ID Movement
Determine the processing method of the <Target >i (check)ii(action)Processing (cutting/chipping/crushing/picking up) of <Target>by < Equipment: Debris processing mechanism>iii(check)Verify the processing results of <target>

by processing
andsolidification<Equipment: Radiation source storage mechanism> stores<Target> to <Equipment: Inner container> >iv (Action)v〇 STEP3 Table of disturbances to operational equipment
Remarks

Verify the safety of the <Target: Debris> stored in the innercontainer(check)① Enter top events that
impede defined actions
and delay work

Safety ofchipped state

Analysis
ID

Classification

Locations

Gairan-1

Static element

PCV

Inside the PCV is in a state of darkness

Gairan-2Static element

PCV

Fog is generated inside the PCVGairan-3

Static element

PCV

Airflow is occurring inside the PCV due to heat generated by the debris

Gairan-4Static element

PCV

Airflow is occurring inside the PCV due to inleakage from existing openings

Gairan-5

Static element

PCV

Airflow is occurring inside the PCV due to nitrogen injection

Gairan-6

Static element

PCV

Water is dripping inside the PCV due to the injection of cooling waterDisturbance candidate② Enter the functions involved in the actionof interest. Candidate entries are thoserelated to either ID c (related to safetyfunction) or d (related to operational function)on the task detail sheet〇 STEP3 Error analysis table
ID

1

Action group
Error mode that stagnates work
sheet I Di

Deciding how to process debris takes time

Featuredfeatures

Disturbance of DisturbanceError generating mechanisms
interestof interest

Work

Disturbance-22

Supplementary
information

The properties of debris and the selected processing method are incompatible, and it takes
time to determine the processing method.

2ii

Debris processing takes time

Gas phase

Gairan-1Gairan-20

3iiSame as above

Gas phase

Gairan-2Gairan-20

4iiSame as above

Gas phase

Gairan-6Gairan-20

5iiSame as above

Gas phase

Gairan-24

Gairan-20

6iiSame as above

Gas phase

Gairan-19

Gairan-20

7iiSame as above

Criticality

Gairan-1Gairan-21

8iiSame as above

Criticality

Gairan-2Gairan-21

9iiGairan-6Gairan-21

10iiGairan-18

Gairan-21③ Extract the error generating
related to the function ofCriticality
Same as mechanisms
aboveinterest in the form of an object tree.
Same as above
Use the “Table of disturbances to Criticality
operational equipment” for extraction.

Excessive heatup of debris in the dark (poor visibility) and volatilization of radioactive
materials
Excessive heatup of debris due to fog (poor visibility) causing volatilization of radioactive
materials
Debris is excessively heated by dripping water (poor visibility), and radioactive materials
volatilize
Excessive heating of debris with high background (noise) and volatilization of radioactive
materials
Dust scattering (poor visibility) overheats debris and volatilizes radioactive materials
Debris is processed into an inappropriate shape in the dark (with poor visibility), and thedebris approaches a critical state.
Debris is processed into an inappropriate shape by fog (poor visibility), and the debris
approaches a critical state.
Debris is processed into an inappropriate shape by dripping water (poor visibility), and thedebris approaches a critical state.

Debris is processed into an inappropriate shape due to dust scattering ( poor visibility ), andthe debris approaches a critical state .

©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-3: Risk assessment table for operational equipment (Detailed version) (4/59)

No.193■ Risk assessment procedures specific to operational equipment•
The procedure for executing STEP 4 shown on page 1/59 of this Appendix is described.
〇 STEP3 error analysis table (reprint of previous page)
ID

Action group
Error mode that causes stoppage of work
sheet I D

1

i

2
3

ii

ii

Functions ofinterest

It takes time to determine the method ofDisturbancesof interest

Supplement
ary
information

Disturbances
Error generating mechanisms
of interest

The properties of debris are incompatible with the processing method selected,and it takes timeWork

Gairan-22

Debris processing takes time

Gas phase

Gairan-1Gairan-20

Excessive heatup of debris in the dark (poor visibility) and volatilization of radioactive materials

Same as above

Gas phase

Gairan-2Gairan-20

Excessive heatup of debris due to fog (poor visibility) causing volatilization of radioactive materials

processing debris

to determine the processing method.

The dust dispersed by processing approaches the allowable dust concentration
inside the PCV

13

ii

Same as above

Gas phase Gairan-23

14

ii

Same as above

Work

Gairan-13

15

ii
ii

Same as above
Same as above

Work
Work

Gairan-16
Gairan-15

Processing jigs wear out quickly, and frequent replacement make processing time-consuming

16
17

ii

Same as above

Work

Gairan-7

No external mechanical/thermal forces are transferred to the debris due to obstruction caused by waterflow

It takes time to allow the processing jig to access the area where application of external
force is desired
Hot spots appear and it takes time to assess the impact on equipment〇 SETP4 risk assessment table
Item 1

Item 2

Targetequipment

The function thatthe target is
responsible for

Debrisprocessing
mechanism

Important monitoring items
Item 3(Extracted from the error
Item 4extraction table)
Analysis
ID

Fuel debris processing
function

15① Enter theequipment and thefunctionof interest
Same asenteredin theSame
erroras above
above
analysis table (taskdetail sheet)

15② Enter the error
generating
mechanisms set in theerror analysis table

Work delay
factorItem 5

Direct causes of Indirect causes
error
of error

Processing jigs Excessive wear
wear out
and tear ofquickly, and processing jigs
frequent
replacement
makeprocessing
timeconsuming

Same asabove

Weighted evaluation of important monitoring items

Same asabove

Fuel debris

Item 6Detectionrequirements toavoid work delays[Item 4](a) Degree of wear
and tear ofprocessing jigs

Item 7-1

Point

3

Same asabove

Applicable
functionWork

Impact on function
Technology forremotely exchanging
processing jigs onsite, such as a toolchanger, is underdevelopment in thefuel debris retrieval
project.

Item 7-2

Point

3[Item 5](b) Compressive
strength of fueldebris③ Break down the mechanisms in Item 3
into straightforward physical phenomena

3

Work

Same as above

3

Effects on accurate and prompt on-site
response by workers
・ It is difficult to directly determine the wear
and tear of processing jigs. For visualverification, training for operators in sensory
inspection is required. For cases other thanvisual verification, multiple data, such as jig
vibration and motor output, must be obtained
to make a determination.
・ General industrial technology can beutilized for all of the above.
・ It is difficult to directly determine thecompressive strength, as it is necessary tocollect a sample and conduct a tensile test,
etc.
・ Since the existing technology requires
sample collection + hot lab testing, not being
performed at the processing site, there is aproblem when measurement is required on
site.

Item 7-4(Evaluation
Results)
Impact on throughput
Point of
Poi
Indiviby addressing errors
representati
ntdual(indirect causes)on
The task is assumed
to be temporarily
restricted due to themeasures in Item 72 1.
18
Item 7-3

182

Same as above

18④ Implement risk assessment based on theinformation inherited from the error analysis table©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-3: Risk assessment table for operational equipment (Detailed version) (5/59)

No.194■ Risk assessment table■ Score table for Item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still underdevelopment [2 points] Countermeasures exist, butthere are no track records of application at the
Fukushima Daiichi [1 point] Countermeasures exist, andhave been applied at the Fukushima Daiichi.

■ Score table for item 7-2[4 points] Cannot be determined directly and there are issues
with introduction[3 points] Cannot be determined directly and can expect
introduction to be feasible[2 points] Can be determined directly, but there are issues
with introduction[1 point] Can be determined directly and can expect
introduction to be feasible

Model ID

■ Score table for Item 7-3[4 points] No countermeasures, and impact on throughput is unknown[3 points] Countermeasures exist, but throughput decreases significantly due tosuspension of task
[2 points] Countermeasures exist, but the throughput decreases due to task load
limitations[1 point] No impact on throughput, or when 7-1 is 1 point

Daily workflow

Process

Ko-3 : Debris retrieval

Work

Sa-2 operational/safety equipment inside the PCV: Verification of the overall situation andImportant monitoring items
Item 3 (excerpt
from error
extraction table)

Presence or absenceof countermeasuresfor disturbing
functions

Item 7-2

Item 7-3

Item 7-4(Evaluation
results)

Effects on
accurate andprompt on-site
response byworkers

Impact on
throughput
byaddressing
errors(indirect
causes)Point ofrepresentation

Detectionrequirements toavoid work delays

Item 7-1

Point

Indirectcauses oferror

Item 6

Point

Directcauses oferror

Item 5

Applicable
functionThefunctionWork
that theAnalysisdelay
equipment target isID
factorresponsiblefor

Item 4

Individual

Item 2Point

Item 1Risk
assessment
table
analysisTargetnumber

Weighted evaluation of important monitoring items

No environmental changes inside the PCV

No task disturbing

*1

*4

*2

*3

(*1) The name of item 2 is omitted for layout reasons. Formal name: Safety functions or operational functions the target
equipment is responsible for(*2) The name of item 7-1 is omitted for layout reasons. Formal name: presence or absence of countermeasures for disturbing
safety or operational functions(*3) The name of item 7-3 is omitted for layout reasons. Formal name: Impact on throughput by countermeasures in item 7-1(*4) For layout reasons, analysis IDs are abbreviated from this page onward.

©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-3: Risk assessment table for operational equipment (Detailed version) (6/59)■ Risk assessment table
No.195■ Score table for item 7-1■ Score table for item 7-2[4 points] No countermeasures have been determined

Model ID

[3 points] Countermeasures exist, but they are still under development[2 points] Countermeasures exist, but there are no track records of application at
the Fukushima Daiichi[1 point] Countermeasures exist, and have been applied at the Fukushima Daiichi.

Process[The numbering rules for analysis ID]
Safety function related: Saku-A-Arabic numerals
Operational function related: Saku-B-Arabic numerals[Items 4/5](a) Presenceof interfering
objects
unaffectedby darkness
Darkness

Fog

Dripping
water[Items 4/5](a) Presenceof interfering
objects
unaffectedby fog[Item 4/5] (a)Presence ofinterfering
objects
unaffectedby drippingwater

Presence or absenceof countermeasuresfor disturbing functions

1

Investigation inside the
Fukushima Daiichi-2
PCV shows theeffectiveness of themethod that confirms
the presence orabsence of interfering
objects on the taskroute in advance using
dedicated equipment,
and application of asimilar method isassumed.

1

Same as above

1

Same as above

Point

1

1

1

Effects on accurate andprompt on-site response byworkers

Item 7-3
Impact on
throughput byaddressing
errors (indirectcauses)Item 7-4(Evaluation
results)

Point ofrepresentation

MovingMovingPresence orDelay inmechanism function inside absence ofascertaining
inside thethe PCV
interfering objects the presence or
PCV
cannot beabsence ofdetermined due to interfering
fog, andobjectsverification ofsafety on thetransfer routetakes time
MovingMovingPresence orDelay inmechanism function inside absence ofascertaining
inside thethe PCV
interfering objects the presence or
PCV
cannot beabsence ofdetermined due to interfering
dripping water, and objects
verification ofsafety on thetransfer routetakes time

Detectionrequirements
to avoid work
Point
delaysItem 7-2

Individual

Saku3
A-

2

Delay inascertaining
the presence orabsence ofinterfering
objects

Item 7-1

SafetySakuA-

1

Indirectcauses oferror

Item 6

SafetySakuA-

MovingMovingPresence ormechanism function inside absence ofinside thethe PCV
interfering objects
PCV
cannot be
determined due todarkness, andverification ofsafety on thetransfer routetakes time

Item 5

SafetyThe analysis
number is definedby the combinationof these two
character strings[4 points] No countermeasures, and impact on throughput is unknown[3 points] Countermeasures exist, but throughput decreases significantly due tosuspension of task
[2 points] Countermeasures exist, but throughput decreases due to workload limitations[1 point] No impact on throughput, or when 7-1 is 1 point

Weighted evaluation of important monitoring items

Applicable
function

Ko-3 : Debris retrieval: Approaching the object to
Work
Sa-2
be processed
Important monitoring items
Item 3 (Extracted
Item 1
Item 2from the error
Item 4
Risk
extraction table)
assessment
Direct causes
tableof error
The function
analysisTargetthat the target
numberWork delay factor
equipment is responsiblefor■ Score table for item 7-3[4 points] Cannot be determined directly, and there are issues
with introduction[3 points] Cannot be determined directly and can expect
introduction to be feasible[2 points] Can be determined directly and there are issues withintroduction[1 point] Can be determined directly and can expect
introduction to be feasible

1

Because item
7-1 is 1 point

11Same as above

1

Same as
above

1

1

Same as above

1

Same as
above

1

1

・ Direct determination ispossible if 3D scans orother dimensional
acquisitions are made・ Detailed investigation
inside the Fukushima
Daiichi-2 PCV shows theapplication of laser
scanning technology toobtain maintenanceinformation on interfering
objects.

Point©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-3: Risk assessment table for operational equipment (Detailed version) (7/59)■ Risk assessment table■ Score table for item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still underdevelopment[2 points] Countermeasures exist, but there are no trackrecords of application at the Fukushima Daiichi[1 point] Countermeasures exist, and have been applied at
the Fukushima Daiichi.
Process

Ko-3

Work

Sa-2

No.196■ Score table for item 7-2[4 points] Cannot be determined directly, and there are issues
with introduction[3 points] Cannot be determined directly and can expect
introduction to be feasible[2 points] Can be determined directly and there are issues withintroduction[1 point] Can be determined directly and can expect
introduction to be feasible

1

Work

[Item 5](b) Velocity ofwater flow on thetransfer route

Point ofrepresentation

Water
flow

Impact on
throughput byaddressing
errors(indirect
causes)Individual

Work

Movingmechanism
inside the
PCV

Item 7-4(Evaluation
results)

Point

SafetySaku1
B-

Item 7-3

1

Because Item
7-1 is 1 point

1

1

1

Because Item
7-1 is 1 point

1

2

Same as
above

2

2

Item 7-2
Effects on accurate and prompt
on-site response by workers

Point

Applicable
function

Point: Debris retrieval: Approaching the object tobe processed
Important monitoring items
Weighted evaluation of important monitoring items
Risk
Item 3 (excerpt
Assesfrom error
Item 1
Item 2Item 4Item 5Item 6Item 7-1
sment
Risk
extraction
assessment Table
table)
Analystable
Detection
Presence or absence ofThe
analysisrequirements tocountermeasures for disturbing
isfunctionIndirect avoid work
numberfunctionsTargetthat theWork delay Direct causes
Numbcauses of delays
equipment
target isfactorof errorer
error
responsibleforMovingMovingPresence orDelay in
[Items 4/5]
Investigation inside the Fukushimamechanism function
absence ofascertaining(a) Presence ofDaiichi-2 PCV shows the effectivenessinside theinside the interfering
the presence
interferingof the method that confirms the
PCV
PCV
objects cannot or absence ofobjectspresence or absence of interfering
be determined interfering
unaffected by
objects on the task route in advance
Sakudue to highobjectsnoise
using dedicated equipment, and
1
4
Noise
Abackgroundapplication of a similar method is
noise, andassumed.
verification ofsafety on thetransfer routetakes time
MovingTransfer takes Low[Item 4]・ Records from underwater ROV
functiontime due totransferring(a) Time to reach
injection exist in the investigation
inside the water flow
speed
destination
inside thethe Fukushima Daiichi-3
PCV
PCV, and since the flow of water istaken into consideration in thedesigned measures, similar response
will be necessary.
1■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is unknown[3 points] Countermeasures exist, but throughput decreases significantly
due to suspension of task
[2 points] Countermeasures exist, but throughput decreases due toworkload limitations[1 point] No impact on throughput, or when 7-1 is 1 point

・ Direct determination ispossible if 3D scans or otherdimensional acquisitions aremade1・ Detailed investigation
inside the Fukushima Daiichi-2
PCV shows the application oflaser scanning technology toobtain maintenance information
on interfering objects.
・ Can be determined directly
by acquiring the actual transfer
time

1・ Can be executed throughcontrol, and there are no issues
with introduction

・ Heavy machinery with
underwater specifications exists forgeneral work, and it is assumed that it
is possible to formulate
countermeasures that resist the flowof water.

Same as above

2

When using a Price current
meter, it is possible to directly
determine the flow velocity, butthere are problems because it
requires assessing the radiation
resistance of the flow meter in ahigh-dose radiation environment

1©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-3: Risk assessment table for operational equipment (Detailed version) (8/59)■ Risk assessment table

No.197■ Score table for item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still
under development[2 points] Countermeasures exist, but there are no
track records of application at the Fukushima Daiichi[1 point] Countermeasures exist, and have been
applied at the Fukushima Daiichi.

Model ID
Process

Ko-3 : Debris retrieval

Work

Sa-2 : Approaching the object to be processed

Detectionrequirements
Indirect to avoid work
causes of delays
error

Hot spot

Item 7-1[Item 4](a) Degree ofeffects onequipment
against hot
spots (radiation
resistance)
1

Saku
2
-B-

1

Work

[Item 5](b) Location of
hot spots on
the transfer
route

Item 7-2

Presence orabsence ofcountermeasuresfor disturbing
functions

Effects on accurate andprompt on-site response byworkers

The operational
procedure of
temporaryevacuation fromthe area when a
hot spot is verified
has been
incorporated in theinvestigation
inside the
Fukushima
Daiichi-2 PCV, so
a similar response
will be necessary.

1・ When using a dosimeter,a direct determination can bemade by setting the thresholddose based on the cumulative
exposure dose of theoperational equipment.

Same as above

Item 7-3

3・ The dosimeter has been
introduced in the on-site
demonstration testing of the
project of investigation inside
the PCV.

3・ When using a dosimeter,
the specific location of thesource cannot be determined
directly due to the surrounding
background.
・ Development oftechnology to identify hot spots
in a high-dose radiation
environment is required.

3

Impact on
throughput
byaddressing
errors(indirect
causes)Throughput
is assumed
to besignificantly
reduced dueto theunknown
duration of
temporaryevacuation
due tomeasurestaken forItem 7-1.

Same asabove

Item 7-4(Evaluation
results)

Point ofrepresentation

Delay inascertaining
effects onradiation

Item 6Work

Transfer takes
time due toassessment of
impact on
equipment
caused byappearance of
hot spots

Direct causesof error

Item 5

IndividualMoving function
inside the PCVWork delay
factor

Weighted evaluation of important monitoring items

Point

The function that thetarget is responsiblefor

Item 4■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is unknown[3 points] Countermeasures exist, but throughput decreases significantly
due to suspension of task
[Point 2] Countermeasures exist, but the throughput decreases due totask load limitations[1 point] No impact on throughput, or when 7-1 is 1 point

Point

Movingmechanism
inside the
PCV

Item 2Item 3 (excerpt
from error
extraction table)

Applicable function

equipment

Important monitoring items

Point

Risk
Asses
sment
TableItem 1
Risk
Analysassessment
is
table
Numb
analysisTargetnumber er■ Score table for Item 7-2[4 points] Cannot be determined directly, and there are issues withintroduction[3 points] Cannot be determined directly, but can expect introduction to befeasible[2 points] Can be determined directly, but there are issues with introduction[1 point] Can be determined directly, and can expect introduction to befeasible

3

9

9

9

©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-3: Risk assessment table for operational equipment (Detailed version) (9/59)

No.198■ Risk assessment table

Model ID

■ Score table for item 7-1■ Score table for item 7-2■ Score table for item 7-3[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still underdevelopment[2 points] Countermeasures exist, but there are no track records ofapplication at the Fukushima Daiichi[1 point] Countermeasures exist, and have been applied at the
Fukushima Daiichi.

[4 points] Cannot be determined directly, and there are issues withintroduction[3 points] Cannot be determined directly and can expect introduction to befeasible[2 points] Can be determined directly, but there are issues with introduction[1 point] Can be determined directly, and can expect introduction to befeasible[4 points] No countermeasures, and impact on throughput is unknown[3 points] Countermeasures exist, but throughput decreases significantly due tosuspension of task
[2 points] Countermeasures exist, but throughput decreases due to workload limitations

Process

Ko-3 : Debris retrieval

Work

Sa-2 : Approaching the object to be processed

Item 2

Cannot detect thetransfer route due tosediment soaring
during transfer, andtransfer takes time

Detectionrequirements
Indirectto avoid
Direct causes ofcauseswork delays
error
of error
Delay inascertaining thetransfer route

Saku3
B-

Movingmechanism
inside the
PCV

Saku4
B-

Movingmechanism
inside the
PCV

Item 6[Items 4/5](a) Transfer
route
detection
unaffected
Soaring by soaring
sediment sediment

Verification of current Delay inlocation takes time due ascertaining theto darkness
current locationof the moving
mechanism
inside the PCVItem 7-1

3Work[Items 4/5](a) Current
location
detection
unaffectedby darkness

Darkness

3

Work

Presence or absence ofcountermeasures for disturbing
functions

The detailed investigation inside
the Fukushima Daiichi-2 PCV iscurrently developing a technologythat enables equipment to be
moved even in the PCV
environment by obtaining
information on the maintenance ofinterfering objects in advancethrough laser scanning.

・In the investigation inside the
Fukushima Daiichi-2 PCV, selflocation was estimated based on
the amount of equipment
movement and information fromthe drawings.
・In the Fukushima Daiichi-3
underwater ROV investigation,
self-location was estimated basedon surrounding structures andinformation from the drawings.
・During debris retrieval, thelayout of surrounding structures
will change due to removal ofinterfering objects, etc., soadditional measures arenecessary.

Item 7-2

Point

3

2

Effects on accurate andprompt on-site response
by workers

Sampling equipment to be
deployed during theexperimental fuel debris
retrieval phase will beequipped with technology
for acquiring informationon the layout of structuresusing laser scanning, andthe on-site demonstration
testing is scheduled.

・ Workers can directly
determine their selflocation by the method
applied in the past
investigation inside thePCV shown in Item 7-1.
・ However, as theconstruction progresses,
there is a high possibility
that the landmarks willchange, so task isnecessary to update theinformation on the layoutof structures inside thePCV, which presents
problems.

Item 7-3(indirect
causes)
Impact on
throughput due
to errorPointhandling(Indirect
causes)There is no
impact on
throughput with
the introductionof thetechnology
1shown in Item
7-1

1Same as above

Item 7-4(Evaluation
Results)

Point ofrepresentation

Movingfunction
inside the
PCVWork delay factor

Item 5

Individual

The functionthat thetarget is
responsiblefor

Item 4Weighted evaluation of important monitoring items

Corresponding
functionMovingmechanism
inside the
PCV

Important monitoring items
Item 3 (excerpt fromerror extraction table)

Point

Risk
Asses
sment
Item 1
Risk
Table
assessment
Analystable
isanalysisTargetNumb
numbererequipment[1 point] No impact on throughput, or when 7-1 is 1 point

9

9

6

6

©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-3: Risk assessment table for operational equipment (Detailed version) (10/59)

No.199■ Risk assessment table■ Score table for item 7-1

Model ID
Process
Work

Fog

6

Movingmechanism
inside the
PCVMovingfunction
inside the
PCV

Verification of current Delay in ascertaining
location takes time the current location
due to dripping water of the moving
mechanism inside
the PCV

7

Movingmechanism
inside the
PCVMovingfunction
inside the
PCV

Verification of current Delay in ascertaining
location takes time the current location
due to the highof the moving
background noisemechanism inside
the PCV

3

Dripping
water

Noise

[Items 4/5](a) Current
location
detection
unaffected bydripping water

3

Same as above[Items 4/5](a) Current
location
detection
unaffected by
noise

3

Same as above

2・ Workers candirectly determine theirself-location by themethod applied in thepast investigation
inside the PCV shownin Item 7-1.
・ However, as theconstruction
progresses, there is ahigh possibility that thelandmarks will change,
so task is necessary to
update the informationon the layout ofstructures inside thePCV, which presents
problems.

12Same as above

1

2

Same as above

1

Impact on
throughput due toerror handling(Indirect causes)

Item 7-4(Evaluation
Results)

Point ofrepresentation

5・ In the investigation inside
the Fukushima Daiichi-2 PCV,
self-location was estimatedbased on the amount ofequipment movement andinformation from the drawings.
・ In the Fukushima Daiichi3 underwater ROV
investigation, self-location was
estimated based onsurrounding structures andinformation from the drawings.
・ During debris retrieval,
the layout of surrounding
structures will change due toremoval of interfering objects,
etc., so additional measures
are necessary.

[Items 4/5](a) Current
location
detection
unaffected byfog

Effects on accurate
and prompt on-site
response by workers

Item 7-3

Individual

Verification of current Delay in ascertaining
location takes time the current location
due to fog
of the moving
mechanism inside
the PCV

Presence or absence ofcountermeasures for
disturbing functions

Item 7-2

Point

Indirect Detection
causes of requirements toerror
avoid work
delaysItem 7-1

Point

Movingfunction
inside the
PCV

Direct causes oferror

Item 6Work

Movingmechanism
inside the
PCVWork delay factor

Item 5Work

The functionthat the target
is responsiblefor[1 point] No impact on throughput, or when 7-1 is 1 point

Work

Table
Analysis Target
equipment
Number

Item 4[4 points] No countermeasures, and impact on throughput is unknown[3 points] Countermeasures exist, but throughput decreases significantly due tosuspension of task
[2 points] Countermeasures exist, but throughput decreases due to workload limitations

Weighted evaluation of important monitoring items

Corresponding
function

SakuB-

Item 2Item 3 (excerpt fromerror extraction
table)

Point

SakuB-[4 points] Cannot be determined directly, and there are issues withintroduction[3 points] Cannot be determined directly and can expect introduction to befeasible[2 points] Can be determined directly, but there are issues with introduction[1 point] Can be determined directly and can expect introduction to befeasible

Ko-3 : Debris retrieval
Sa-2 : Approaching the object to beprocessed
Important monitoring items

Risk
assessment
Risk
table
Item 1Asses
analysis
sment
numberSaku-B-■ Score table for item 7-3■ Score table for item 7-2[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still underdevelopment[2 points] Countermeasures exist, but there are no track records ofapplication at the Fukushima Daiichi[1 point] Countermeasures exist, and have been applied at the
Fukushima Daiichi.

66Same as above

6

6

Same as above

6

6

There
is
no
impacton
throughput with
the introductionof the technology
shown in Item 7-1©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-3: Risk assessment table for operational equipment (Detailed version) (11/59)■ Risk assessment table■ Score table for item 7-2[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still underdevelopment[2 points] Countermeasures exist, but there are no track records ofapplication at the Fukushima Daiichi[1 point] Countermeasures exist, and have been applied at the
Fukushima Daiichi.

[4 points] Cannot be determined directly, and there are issues withintroduction[3 points] Cannot be determined directly and can expect introduction to befeasible[2 points] Can be determined directly, but there are issues with introduction[1 point] Can be determined directly and can expect introduction to befeasible

Process

Ko-3 : Debris retrieval

Work

Sa-3 : Work Prior to processing

Risk
assessment
table analysis
numberItem 1

Delay inascertaining
whether thedebris is
submerged ornot

Due to fog, ittakes time toverify if thedebris is
submerged ornotDelay inascertaining
whether thedebris is
submerged ornot

Item 7-2

Item 7-3(Evaluation
Results)

Indirect Detection
Direct causes ofcauses of requirements to
error
error
avoid work delays

Due to thedarkness, ittakes time toverify if thedebris is
submerged ornot

Item 7-1

Item 6Point[Item4/5]

3

It is necessary to takecountermeasures against therisk of making the wrong
decision not to apply the neutron
absorbent in spite of being
submerged in water. It isnecessary to utilize the neutron
detector under development in
the 1 F subsidized project, andto have an action policy for
immediately spraying neutronmaterial when criticality isapproached.

3

Same as above(a) Submergeddebris detection unaffected bydarkness
Darkness

Presence or absence ofcountermeasures for disturbing
functions

Impact on
throughput by
Point addressing
errors (indirectcauses)

Effects on accurate
and prompt on-site
response by workers

3

Although sensory
determination (=direct determination)
may be possible withcamera images,
there are cases inwhich wrong
determinations may
be made dependingon the conditions forphotography, andcertainty cannot be
guaranteed.

2

3

Same as above

2

Point ofrepresentation

Debris
Saku2 processing
Amechanism[Criticality]
Neutronabsorbent
application
function

Item 7-4
Item 5

Individual

Saku1
A-

Weighted evaluation of important monitoring items

Safety[Criticality]
Neutronabsorbent
application
function[1 point] No impact on throughput, or when 7-1 is 1 point

Point

Functions thattarget is
responsible for Work delay
factor[4 points] No countermeasures, and impact on throughput is unknown[3 points] Countermeasures exist, but throughput decreases significantly due tosuspension of task
[2 points] Countermeasures exist, but throughput decreases due to workload limitations

SafetyDebrisprocessing
mechanism

Item 2

Important monitoring items
Item 3(Extracted
from the error
Item 4extraction
table)■ Score table for item 7-3

Applicable
functionTargetequipment

No.200■ Score table for item 7-1

18

18

18

18

Addressing
Item 7-1 limits
the workload.

[Item4/5](a) Submergeddebris detection
unaffected by fog
Fog

Same asabove©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-3: Risk assessment table for operational equipment (Detailed version) (12/59)

No.201■ Risk assessment table■ Score table for item 7-2[4 points] Cannot be determined directly and there are issues
with introduction[3 points] Cannot be determined directly and can expect
introduction to be feasible[2 points] Can be determined directly, but there are issues withintroduction[1 point] Can be determined directly and can expect
introduction to be feasible■ Score table for item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still
under development[2 points] Countermeasures exist, but there are no
track records of application at the Fukushima Daiichi[1 point] Countermeasures exist, and have been
applied at the Fukushima Daiichi.

Model ID
Process

Ko-3: Debris retrieval

Work

Sa-3

: Work Prior to processing
Important monitoring items

Item 1

Item 6Item 7-1

requirements
to avoid work
delaysPoint of representation

Indirectcausesof error

Item 7-4(Evaluation
Results)

18

18

18

18

Impact on
Presence or absence ofcountermeasures for disturbing
functions

Effects on accurate andprompt on-site response bythroughput

Point

Directcauses oferror

Item 7-3

Individual

DetectionWork delay
factorItem 7-2

Point

The functionthat the target
is responsiblefor

Item 5

Applicable function

Targetequipment

Item 4Weighted evaluation of important monitoring items

Point

Risk
assessme
nt
table
analysis
numberItem 2Item 3 (excerpt
from error
extraction table)■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is unknown[3 points] Countermeasures exist, but throughput decreases significantly
due to suspension of task
[2 points] Countermeasures exist, but throughput decreases due toworkload limitations[1 point] No impact on throughput, or when 7-1 is 1 point

workers

due to error
handling(Indirect
causes)

DebrisSaku-A-

3[Criticality]

Due to dripping

Delay in

[Items 4/5]

It is necessary to take

Neutronwater, it takes

ascertaining(a) Submerged

absorbenttime to verify ifwhether theapplication

the debris isfunctionsubmerged ornotor notprocessing

3

Although sensory

Addressing

countermeasures against the risk ofdetermination (= direct

Item 7-1

debrismaking the wrong decision not to apply

determination) may belimits thedebris is

detection

the neutron absorbent in spite of being

possible with camera

workload.

submerged

unaffected bysubmerged in water. It is necessary toimages, there are cases inDripping
water

dripping water3

Safety utilize the neutron detector undermechanism

which wrong determinations

development in the Fukushima Daiichi

may be made depending on

subsidized project, and to have an

the conditions foraction policy for immediately spraying

photography, and certainty

neutron material when criticality iscannot be guaranteed.

2

approached.

DebrisSaku-A-

4

processing
mechanism[Criticality]

Due to high

Delay in

[Items 4/5]

Neutronbackgroundascertaining(a) Submerged

absorbent

noise, it takes

whether thedebrisapplication

time to verify ifdebris isfunction

the debris issubmerged

unaffected bysubmerged oror not

noise

Noise

detection

3

SafetySame as above

3

Same as above

2

Same asabove

not©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-3: Risk assessment table for operational equipment (Detailed version) (13/59)

No.202■ Risk assessment table■ Score table for item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still
under development[2 points] Countermeasures exist, but there are no
track records of application at the Fukushima Daiichi[1 point] Countermeasures exist, and have been
applied at the Fukushima Daiichi.

Model ID
Process

Ko-3: Debris retrieval

Work

Sa-3

: Work Prior to processing■ Score table for item 7-2[4 points] Cannot be determined directly and there are issues
with introduction[3 points] Cannot be determined directly and can expect
introduction to be feasible[2 points] Can be determined directly, but there are issues withintroduction[1 point] Can be determined directly and can expect
introduction to be feasible

Important monitoring items
Item 3■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is unknown[3 points] Countermeasures exist, but throughput decreases significantly
due to suspension of task
[2 points] Countermeasures exist, but throughput decreases due toworkload limitations[1 point] No impact on throughput, or when 7-1 is 1 point

Weighted evaluation of important monitoring items(excerpt from
Item 1

Item 7-4
Item 4Item 5Item 6Item 7-1

Item 7-2

Item 7-3(Evaluation
Results)

table)

of error

avoid work
delaysPresence or absence ofcountermeasures for
disturbing functions

Effects on accurate andprompt on-site response bythroughput

workers

due to error
handling- The density of the neutron- Can be determined- Based oncooling water

application of(a) Application

absorbent developed in the

directly by obtaining actual

thedisperses theneutrontime for neutron

debris retrieval project istask hours

evaluation ofneutronabsorbent

high, and it is thought that it- Can be executed in theabsorbent,

Safety[Item 4]

3

and

12

12

12

causes)Insufficientabsorbent

12(Indirect

The flow of

Water
flow

Point of representation

causesrequirements to

Individual

mechanismof error

Indirect

Point

processing[Criticality]
Neutronabsorbent
application
function

Direct causes

Impact on

Point

DebrisWork delay
factor

Applicable function

equipment

The functionthat the target
is responsibleforDetection

Point

Target5

error
extraction

Risk
assessment
table
analysis
numberSaku-A-

Item 22

2

Item 7-1, thewill overcome the Marangoni

control room, and there are

impact on

convection and sink.

no issues with introduction

throughput isapplicationconsidered totakes time

be limited.
[Item 5]

When using a Price current(b) Water flow

meter, it is possible tovelocity at thedirectly determine the flow

absorbent
application area

3

Safetyneutronvelocity, but there areSame as above

2 problems because it

2

Same asabove

requires assessing theradiation resistance of theflow meter in a high-doseradiation environment©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-3: Risk assessment table for operational equipment (Detailed version) (14/59)■ Risk assessment table■ Score table for item 7-1[4 points] No countermeasures have been
determined[3 points] Countermeasures exist, but they
are still under development[2 points] Countermeasures exist, but there
are no track records of application at the
Fukushima Daiichi[1 point] Countermeasures exist, and havebeen applied at the Fukushima Daiichi.

Model ID
Process: Debris retrieval
Ko-3

Work

Sa-3

Item 7-3

Item 7-4(Evaluation
Results)

factorerror

causes of requirements to avoid

error

work delays

Presence or absence ofcountermeasures for disturbing
functions

Effects on accurate
and prompt on-sitethroughput due toerror handling

response by workers(Indirect causes)

Due toDelay in

[Items 4/5]

It is necessary to take

Although sensory

Addressing Item 7-

darkness,

ascertaining the(a) Detection ofcountermeasures against thedetermination (= direct

1 limits theverification

neutronneutron absorbent

risk of making the wrong

determination) may beworkload.

of theabsorbent

application statusdecision not to start processing

possible with camera

results ofapplication

unaffected bywork despite inadequate

images, there areneutronstatusdarknessapplication of neutroncases in which wrong

3

Darknesstakes timeabsorbent. By utilizing the3

determinations may beneutron detector being

made depending on

developed in the Fukushima

the conditions forDaiichi subsidized project, thephotography, andproject is advocating an

certainty cannot be

operational procedure to verify

guaranteed.

2

Point ofrepresentation

Direct causes ofDetection

Individual

Work delay

Indirectapplication

mechanism

Item 7-2

Impact on

absorbent

processing

Item 7-1

SafetyDebrisItem 6

Point[Criticality]
Neutronabsorbent
application
function

Item 5

Point

Target

The functionthat thetarget is
responsiblefor

Weighted evaluation of important monitoring items

Applicable
function

Item 2

Important monitoring items
Item 3(excerpt
from error
Item 4extraction
table)

Point

Item 1equipment

6

No.203■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is
unknown[3 points] Countermeasures exist, but throughput decreases
significantly due to suspension of task
[2 points] Countermeasures exist, but throughput decreases
due to workload limitations[1 point] No impact on throughput, or when 7-1 is 1 point: Work Prior toprocessing

Risk
assessment
table analysis
numberSaku-A-■ Score table for item 7-2[4 points] Cannot be determined directly and there are issues
with introduction[3 points] Cannot be determined directly and can expect
introduction to be feasible[2 points] Can be determined directly, but there are issues withintroduction[1 point] Can be determined directly and can expect
introduction to be feasible

18

18

18

18

the effectiveness after
spraying.

7

processing
mechanism

Due to fog,

Delay in

[Items 4/5]

verification

ascertaining the(a) Detection ofof theneutronneutron absorbent

results ofabsorbent

neutronapplication

absorbent

statusFogapplication status
unaffected by fog

3

SafetyDebrisSaku-A-[Criticality]
Neutronabsorbent
application
function

Same as above

3

Same as above

2

Same as above

application
takes time

©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-3: Risk assessment table for operational equipment (Detailed version) (15/59)

No.204■ Risk assessment table■ Score table for item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still underdevelopment[2 points] Countermeasures exist, but there are no trackrecords of application at the Fukushima Daiichi[1 point] Countermeasures exist, and have been applied at
the Fukushima Daiichi.

Model ID
Process

Ko-3: Debris retrieval

Work

Sa-3

: Work Prior to processing■ Score table for item 7-2[4 points] Cannot be determined directly and there are issues
with introduction[3 points] Cannot be determined directly and can expect
introduction to be feasible[2 points] Can be determined directly, but there are issues withintroduction[1 point] Can be determined directly and can expect
introduction to be feasible

Important monitoring items
Item 1

Weighted evaluation of important monitoring items
Item 7-4

Item 4Item 5Item 6Item 7-1

Item 7-2

Item 7-3(Evaluation
Results)

Due to dripping water,

Delay in

[Items 4/5]

It is necessary to take

Although sensory

Addressing

Neutronverification of theascertaining(a) Detection ofcountermeasures against thedetermination (= direct

Item 7-1 limits

absorbent

results of neutron

the neutron

neutron absorbent

risk of making the wrong

determination) may be

the workload.

application

absorbent application

absorbent

application statusdecision not to start processing

possible with camera

functiontakes time

application

unaffected bywork despite inadequate

images, there are cases

statusdripping water

application of neutron

requirements toavoid work delays

Presence or absence ofcountermeasures for disturbing
functions

Effects on accurate andprompt on-site response

throughput due

Point

Detection

Point of representation[Criticality]

Indirectcauses of
error

Point

Work delay factor

Direct causesof error

Individual

Applicable function

Targetequipment

18

18

18

18

Impact on

Thefunctionthat thetarget is
responsible
for

Point

Risk
assessment
table
analysis
numberItem 2Item 3 (excerpt fromerror extraction table)■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is unknown[3 points] Countermeasures exist, but throughput decreases significantly
due to suspension of task
[2 points] Countermeasures exist, but throughput decreases due toworkload limitations[1 point] No impact on throughput, or when 7-1 is 1 pointby workers

to errorhandling(Indirect
causes)

Saku
8
-A-

Dripping
water

processing

3

SafetyDebrismechanism

absorbent. By utilizing thein which wrong
3

determinations may beneutron detector being

made depending on thedeveloped in the Fukushima

conditions forDaiichi subsidized project, thephotography, andproject is advocating an

certainty cannot be

operational procedure to verify

guaranteed.

2

the effectiveness after spraying.

Saku
9
-A-

processing
mechanism

There are many blind

Delay in

[Items 4/5]

Neutronspots in the spraying

ascertaining(a) Detection ofabsorbent

area and verification

the neutron

neutron absorbent

applicationof the results ofabsorbent

function

neutron absorbent

application

Surrounding application status
structures unaffected by blindapplication takes time

status3

SafetyDebris[Criticality]

Same as above

3

Same as above

2

Same asabove

spots due tosurrounding
structures©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-3: Risk assessment table for operational equipment (Detailed version) (16/59)

No.205■ Risk assessment table■ Score table for item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still under development[2 points] Countermeasures exist, but there are no track records ofapplication at the Fukushima Daiichi[1 point] Countermeasures exist, and have been applied at the
Fukushima Daiichi.

Model ID
Process

Ko-3 : Debris retrieval

Work

Sa-4

■ Score table for item 7-2[4 points] Cannot be determined directly and there are issues withintroduction[3 points] Cannot be determined directly and can expect
introduction to be feasible[2 points] Can be determined directly, but there are issues withintroduction[1 point] Can be determined directly and can expect introduction to
be feasible

Item 1

Item 2Item 3 (excerpt
from error
extraction table)

Weighted evaluation of important monitoring items

Item 4Item 5Item 6Item 7-1

Indirectcauses ofcauses of

error

error

requirements
to avoid work
delaysfor2(Indirect causes)

The properties of

Delay inFuel debris[Items 4/5]

The debris retrieval project is

There is a problem in that theprocessing

the debris are

determining

with(a) Fuel debris

studying debris processing

property data necessary for

during sequential

mechanism

functionincompatible withthe optimum

variousproperties

methods based on thedetermining the optimum

testing of thethe processing

processing

properties(compressive

properties of debris (mainly

processing method for debris isprocessing methods inmethod selected,

methodcompressive strength), and is

not specified except for theitem 7-1.

and time isthe processing

required to

area

3

Work

Fuel debris

14also considering operational

24

24

18

18

18

18

The workload is limited

compressive strength.

procedures where multiple

determine theprocessing methods areprocessing

sequentially tried on a single
piece of debris.
3

Debris[Gas

Excessive heatup

Volatilization

Excessive[Item 4]

The following methods of- Direct judgment is possible byprocessing

phase]of debris due toofheatup due(a) Dust

general measures will maintainsetting the threshold for dust

significantly reduced

mechanism

Equipment

darkness (poorradioactive

toconcentration

safety functions, but feasibility

concentration.

because of theto prevent

visibility) causesmaterials

darknessat thehas not yet been evaluated.

- Technology to measure dust

unknown duration ofexcessive

volatilization of

due to(poor

processing- Suspension of work

concentration at the debris

suspension of work

heatup ofradioactive

excessive

visibility)

site unaffected- Injection of cooling water

processing site in a dark andcaused by thedebrismaterials

heatuphigh-dose radiation environment

countermeasures for

3

Safety1

due to error handling
Effects on accurate and prompt
on-site response by workers

processing

method.

Saku-A-Presence or absence ofcountermeasures for disturbing
functions

Debrisstrength) in

Item 7-4(Evaluation
Results)

Point ofrepresentation

target is

DirectPoint

equipment

Work delay factor

Item 7-3

Impact on throughput

Pointthat thePoint

TargetDetection

Item 7-2

Individualfunction

Applicable functionThe

responsible

Saku
-B-

[4 points] No countermeasures, and impact on throughput is unknown[3 points] Countermeasures exist, but throughput decreases significantly due tosuspension of task
[2 points] Countermeasures exist, but throughput decreases due to workload limitations[1 point] No impact on throughput, or when 7-1 is 1 point: Processing of debris
Important monitoring items

Risk
assessment
table analysis
number■ Score table for item 7-3

2

by darkness

is required.
[Item 5]

- Direct judgment is possible by(b) Debris

setting the threshold for debris

unaffected bydarkness

3

Safetytemperature

The throughput will be

Item 7-1.
3

temperature.
Same as above2- When measuring with a thermal

Same as above

camera, there is a problem withradiation resistance in a high-dose radiation environment.

©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-3: Risk assessment table for operational equipment (Detailed version) (17/59)

No.206■ Risk assessment table■ Score table for item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still
under development[2 points] Countermeasures exist, but there are no
track records of application at the Fukushima Daiichi[1 point] Countermeasures exist, and have been
applied at the Fukushima Daiichi.

Model ID
ProcessWork

Ko-3 : Debris retrieval: Processing of
Sa-4
debris■ Score table for item 7-2[4 points] Cannot be determined directly and there are issues
with introduction[3 points] Cannot be determined directly and can expect
introduction to be feasible[2 points] Can be determined directly, but there are issues withintroduction[1 point] Can be determined directly and can expect
introduction to be feasible

Important monitoring items
Item 3■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput
is unknown[3 points] Countermeasures exist, but throughput
decreases significantly due to suspension of task
[2 points] Countermeasures exist, but throughput
decreases due to workload limitations[1 point] No impact on throughput, or when 7-1 is 1 point

Weighted evaluation of important monitoring items
Item 7-4(excerpt fromerror

Item 4Item 5Item 6Item 7-1

Item 7-2

Item 7-3(Evaluation
Results)

extraction
table)

of errorcauses oferror

Excessive

Volatilization

Excessive

heatup ofof radioactive

debris due toDetectionrequirements toavoid work
delays

Impact on

Presence or absence ofcountermeasures for
disturbing functions

Effects on accurate andprompt on-site response byworkers

throughput due toerror handling- Direct judgment is possible

The throughput

heatup due (a) Dust

general measures willby setting the threshold forwill bematerials due

to fogconcentration at

maintain safety functions,

dust concentration.

significantly

fog (poor

to excessive(poor

the processing

but feasibility has not yet- Technology is required toreduced because

visibility)

heatupvisibility)

site unaffectedbeen evaluated.

measure dust concentration at

by fog

18

18

18

18

(Indirect causes)[Item 4]

The following methods ofcausesPoint ofrepresentation

factorIndirect

Individual

Direct causes

Point

Work delay

Point

The functionthat theTargettarget isequipment responsiblefor[Gas phase]
DebrisEquipment toprocessing prevent
mechanis excessive
heatup ofmdebris3

volatilization

Safety2

Item 2

Point

Sak
u-A-

Item 1

Applicable
functionRisk
assessment
table
analysis
numberof radioactive- Suspension of work2

the debris processing site in aof the unknown
3

duration of- Injection of coolingfoggy, high-dose radiationsuspension ofwater

environment.

work caused bymaterials

thecountermeasuresfor Item 7-1.

[Item 5]

- Direct judgment is possible(b) Debris

by setting the threshold fortemperaturedebris temperature.

fog

3

Safetyunaffected bySame as above2- When measuring with a3

Same as above

thermal camera, there is aproblem with radiation
resistance in a high-doseradiation environment.

©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-3: Risk assessment table for operational equipment (Detailed version) (18/59)

No.207■ Risk assessment table■ Score table for item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still
under development[2 points] Countermeasures exist, but there are no
track records of application at the Fukushima Daiichi[1 point] Countermeasures exist, and have been
applied at the Fukushima Daiichi.

Model ID
Process
Work

Ko-3
Sa-4

: Debris retrieval: Processing ofdebris■ Score table for item 7-2[4 points] Cannot be determined directly and there are issues
with introduction[3 points] Cannot be determined directly and can expect
introduction to be feasible[2 points] Can be determined directly, but there are issues withintroduction[1 point] Can be determined directly and can expect
introduction to be feasible

Important monitoring items

Item 1

Item 3 (excerpt
from error
extraction
table)

Item 4Item 6Item 7-1

equipment

target isfactorDirect causesof error

Indirect

Detection

causes of requirements toerror

avoid work delays

Presence or absenceof countermeasuresfor disturbing
functions

Effects on accurate andprompt on-site response bythroughput due toworkers

error handling(Indirect causes)

for
[Gas

Excessive

Volatilization

Excessive [Item 4]

The following- Direct judgment is possible

The throughput willprocessing

phase]

heatup ofof radioactive

heatup(a) Dust

methods of generalby setting the threshold forbe significantly

mechanism

Equipment

debris due tomaterials due

due toconcentration at themeasures will

dust concentration.

reduced because of

to prevent

dripping water

to excessive

dripping

processing site

maintain safety- Technology is required tothe unknown

excessive(poor visibility)

heatupwater

unaffected byfunctions, but

measure dust concentration

heatup ofcauses(poor

dripping water

debrisvolatilization ofvisibility)

SafetyDebris3

radioactive
materials

Item 7-4(Evaluation
Results)

2

3

duration offeasibility has not yetat the debris processing site

suspension of work

been evaluated.

in a dripping water and high-caused by the- Suspension of work

dose radiation environment.

countermeasures- Injection of cooling

Point ofrepresentation

Work delay

Point

that theItem 7-3

Impact on

Point

TargetItem 7-2

Individualfunction

Point

3

Item 5The

responsible

Saku
-A-

Weighted evaluation of important monitoring items

Applicable function

Risk
assessment
table
analysis
numberItem 2■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput
is unknown[3 points] Countermeasures exist, but throughput
decreases significantly due to suspension of task
[2 points] Countermeasures exist, but throughput
decreases due to workload limitations[1 point] No impact on throughput, or when 7-1 is 1 point

18

18

18

18

for Item 7-1.

water
[Item 5]

- Direct judgment is possible(b) Debris

by setting the threshold fortemperaturedebris temperature.

unaffected by- When measuring with a3

Safetydripping water

Same as above2

thermal camera, there are3

Same as above

problems with interference
from dripping water andradiation resistance in ahigh-dose radiation
environment.

©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-3: Risk assessment table for operational equipment (Detailed version) (19/59)■ Risk assessment table■ Score table for item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still underdevelopment[2 points] Countermeasures exist, but there are no trackrecords of application at the Fukushima Daiichi[1 point] Countermeasures exist, and have been applied at
the Fukushima Daiichi.

■ Score table for item 7-2[4 points] Cannot be determined directly and there are issues
with introduction[3 points] Cannot be determined directly and can expect
introduction to be feasible[2 points] Can be determined directly, but there are issues withintroduction[1 point] Can be determined directly and can expect
introduction to be feasible

No.208■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is unknown[3 points] Countermeasures exist, but throughput decreases significantly due tosuspension of task
[2 points] Countermeasures exist, but throughput decreases due to workload
limitations[1 point] No impact on throughput, or when 7-1 is 1 point

Model ID
Process

Ko-3

Work

Sa-4

: Debris retrieval: Processing ofdebrisItem 1

Weighted evaluation of important monitoring items

Item 5factorof error

Indirectcauses of
error

for

4

to avoid work
delaysof countermeasuresfor disturbing

Effects on accurate andprompt on-site response by

due to error handling(Indirect causes)

workersfunctions

Debris[Gas phase]

Excessive

Volatilization

Excessive[Item 4]

The following- Direct judgment is possible by

The throughput willprocessing

Prevention

heatup of debrisof radioactive

heatup due(a) Dust

methods of general

setting the threshold for dust

be significantly

mechanism

function of

due to highmaterials due

to highconcentration

measures willconcentration.

reduced because ofexcessive

backgroundto excessive

backgroundat themaintain safety- Technology is required tothe unknown duration

heatup of(noise) causes

heatup(noise)processing

functions, but

measure dust concentration atfuel debris

volatilization ofsiteradioactive

unaffected bymaterials

noise

3

SafetySaku-A-requirements

Impact on throughput
Presence or absence

feasibility has not yet

2the debris processing site

Point ofrepresentation

responsible

Direct causes

Item 7-4(Evaluation
Results)

Individual

target is

Work delay

Item 7-3

Point

equipmentthat theDetection

Item 7-2

Point

TargetItem 7-1
Applicable function

The function

Item 6Point

Risk
assessment
table
analysis
numberItem 2

Important monitoring items
Item 3 (excerpt
from error
Item 4extraction table)

18

18

18

18

of suspension of work3

caused by the

been evaluated.

where radioactive noise iscountermeasures for- Suspension of work

generated in a high-dose

Item 7-1.

- Injection of coolingradiation environment.

water[Item 5]

- Direct judgment is possible by(b) Debris

setting the threshold for debris

temperaturetemperature.

noise

3

Safetyunaffected by- When measuring with aSame as above2

thermal camera, there are3

Same as above

problems with interference
from dripping water andradiation resistance in a highdose radiation environment.

©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-3: Risk assessment table for operational equipment (Detailed version) (20/59)

No.209■ Risk assessment table■ Score table for item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still
under development[2 points] Countermeasures exist, but there are no
track records of application at the Fukushima Daiichi[1 point] Countermeasures exist, and have been
applied at the Fukushima Daiichi.

Model ID
Process
Work

Ko-3
Sa-4

Item 15Detection

causes ofrequirements toerror

avoid work delays

Presence or absence ofcountermeasures for
disturbing functions

Item 7-2

Effects on accurate andItem 7-3

Impact on throughput
due to error handlingWork delay

Direct causes

factorof error

Excessive

Volatilization

Excessive[Item 4]

The following methods- Direct judgment is

The throughput will beheatup ofof radioactive

heatup(a) Dust

of general measures will

possible by setting thesignificantly reduced

debris due to materials due

due toconcentration at

maintain safety

threshold for dust

because of the

dust

to excessive

dust

the processing

functions, but feasibility

concentration.

unknown duration ofdispersion

heatupdispersion site unaffected by

has not yet been

- Technology is required

(poor

(poor

visibility)

visibility)

dripping water3

SafetySaku-A-

Indirect

Item 7-1

causesvolatilization

prompt on-site response
by workers

2

3(Indirect causes)

suspension of work

evaluated.

to measure dust

caused by the- Suspension of work

concentration at thecountermeasures for- Injection of coolingdebris processing site in

Item 7-1.

water

a high-dose radiationof

Item 7-4(Evaluation
Results)

Point ofrepresentation

mechanism

Item 6

Individual

processing[Gas phase]
Equipment toprevent
excessive
heatup ofdebrisItem 5

Point

Debris

The functionthat the target
is responsiblefor

Weighted evaluation of important monitoring items

Point

equipment

Item 2

Important monitoring items
Item 3(excerpt
from error
Item 4extraction
table)

Applicable
functionTarget

of

Point

Risk
assessment
table
analysis
number: Debris retrieval:
Processing
debris■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is unknown[3 points] Countermeasures exist, but throughput decreases significantly
due to suspension of task
[2 points] Countermeasures exist, but throughput decreases due toworkload limitations[1 point] No impact on throughput, or when 7-1 is 1 point■ Score table for item 7-2[4 points] Cannot be determined directly and there are issues
with introduction[3 points] Cannot be determined directly and can expect
introduction to be feasible[2 points] Can be determined directly, but there are issues withintroduction[1 point] Can be determined directly and can expect
introduction to be feasible

1
8

18

1
8

18

environment.

radioactive[Item 5]

- Direct judgment ismaterials(b) Debris

possible by setting thetemperaturethreshold for debris

unaffected bytemperature.
3

Safetydust dispersion- When measuring with aSame as above2

thermal camera, there

3

Same as above

are problems withinterference from dust
and radiation resistancein a high-dose radiation
environment.

©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-3: Risk assessment table for operational equipment (Detailed version) (21/59)

No.210■ Risk assessment table■ Score table for item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still
under development[2 points] Countermeasures exist, but there are no
track records of application at the Fukushima Daiichi[1 point] Countermeasures exist, and have been
applied at the Fukushima Daiichi.

■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is unknown[3 points] Countermeasures exist, but throughput decreases significantly
due to suspension of task
[2 points] Countermeasures exist, but throughput decreases due toworkload limitations[1 point] No impact on throughput, or when 7-1 is 1 point■ Score table for item 7-2[4 points] Cannot be determined directly and there are issues
with introduction[3 points] Cannot be determined directly and can expect
introduction to be feasible[2 points] Can be determined directly, but there are issues withintroduction[1 point] Can be determined directly and can expect
introduction to be feasible

Model ID
Process

Ko-3

Work

Sa-4

: Debris retrieval: Processing ofdebrisItem 1

causes of

error

error

Impact on

Detectionrequirements
to avoid work
delaysPresence or absence ofcountermeasures for
disturbing functions

Effects on accurate andprompt on-site response bythroughput due toerror handlingworkers(Indirect causes)

Debris is

DebrisInappropriate[Item 4]

Recriticality prevention- When using a neutron

During theprocessing

Debrisprocessed

approachingprocessing(a) Neutron flux

technology based on

detector, a direct

application of themechanismprocessing

into anto criticality

due tounaffected byneutron absorbent

determination can be madeneutron absorbent,

shape control

inappropriat

due to shapedarknessdarknessapplication (temporary

by setting the neutron flux

functione shapechange(poor

3visibility)

SafetyDebrisfor[Criticality]

due toItem 7-4(Evaluation
Results)suspension of task) is2

threshold.

according to the- The neutron detector iscountermeasure in

darkness

Fukushima Daiichi

under development in theitem 7-1.

(poor

subsidized project.

Fukushima Daiichi subsidized[Item 5]project.
- When using camera images,debris(b) Debris

it is difficult to directly

approaches

dimensions

determine the dimension of

the state of

unaffected bydebris, and image processing

criticality

darkness

3

Safetyand theSame as above4

is required.

12

24

24

24

workload is limited
2

being developed in thevisibility),

Point ofrepresentation

factorcauses of

Item 7-3

Individual

responsible

Work delay

Indirect

Item 7-2

Pointtarget is

DirectItem 7-1

Pointthat theItem 6Point

equipment

6

Item 5

The function
TargetSaku-A-

Weighted evaluation of important monitoring items

Applicable
functionRisk
assessment
table analysis
numberItem 2

Important monitoring items
Item 3(excerpt
from error
Item 4extraction
table)

2

Same as above- General cameras have low
radiation resistance in a highdose radiation environment,
and there are development
problems.

©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-3: Risk assessment table for operational equipment (Detailed version) (22/59)

No.211■ Risk assessment table■ Score table for item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still
under development[2 points] Countermeasures exist, but there are no
track records of application at the Fukushima Daiichi[1 point] Countermeasures exist, and have been
applied at the Fukushima Daiichi.

Model ID
Process
Work

Ko-3
Sa-4

■ Score table for item 7-2[4 points] Cannot be determined directly and there areissues with introduction[3 points] Cannot be determined directly and can expect
introduction to be feasible[2 points] Can be determined directly, but there are issues
with introduction[1 point] Can be determined directly and can expect
introduction to be feasible: Debris retrieval: Processing of debris
Important monitoring items

Item 17

DetectionWork delay
factorItem 7-2

Item 7-3

Direct causesof error

Indirectrequirement

causes of error s to avoid

Presence or absenceof countermeasuresfor disturbing functions

Effects on accurate and prompt on-site
response by workers

work delays
Debris isprocessed into
an inappropriate
shape due tofog (poor
visibility), andthe debris
approaches thestate ofcriticality(Evaluation
Results)

Impact on
throughput due
to errorhandling(Indirect
causes)

DebrisInappropriate[Item 4]

Recriticality prevention- When using a neutron detector, a direct

During theapproaching toprocessing(a) Neutron

technology based ondetermination can be made by setting theapplication ofcriticality due to due to fog

flux

neutron absorbent

neutron flux threshold.

the neutron

shape change

unaffected

application (temporary- The neutron detector is underabsorbent,

by fogsuspension of task) is(poor visibility)

3

SafetySaku-A-

Item 7-1

being developed in the2development in the Fukushima Daiichi

2

subsidized project.

workload is

Point ofrepresentation

mechanism

Item 6

Individual

processing

Item 5

Point

DebrisItem 7-4
Item 4Point

equipmentThefunctionthat thetarget is
responsiblefor[Criticality]
Debrisprocessing
shapecontrolfunction

Weighted evaluation of important monitoring items

Point

TargetItem 2Item 3 (excerpt
from error
extraction table)

Applicable
functionRisk
assessment
table analysis
number■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is unknown[3 points] Countermeasures exist, but throughput decreases significantly
due to suspension of task
[2 points] Countermeasures exist, but throughput decreases due toworkload limitations[1 point] No impact on throughput, or when 7-1 is 1 point

12

24

24

24

limitedFukushima Daiichi

according to

subsidized project.

thecountermeasur
e in item 7-1.
[Item 5]- When using camera images, it is difficult(b) Debris

to directly determine the dimension ofdimensions

debris, and image processing is required.

unaffected- Image processing for countermeasures
3

Safetyby fogSame as above

4

against fog and halation suppression withlighting are required.

2

Same asabove- General cameras have low radiation
resistance in a high-dose radiation
environment, and there are development
problems.

©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-3: Risk assessment table for operational equipment (Detailed version) (23/59)■ Risk assessment table■ Score table for item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still
under development[2 points] Countermeasures exist, but there are no
track records of application at the Fukushima Daiichi
Ko-3: Debris retrieval[1 point] Countermeasures exist, and have been
Sa-4
: Processing of debris
applied at the Fukushima Daiichi.
Important monitoring items
Item 3 (excerpt
Item 2Item 5Item 6from error
Item 1
Item 4Model ID
ProcessWork■ Score table for item 7-2[4 points] Cannot be determined directly andthere are issues with introduction[3 points] Cannot be determined directly and can
expect introduction to be feasible[2 points] Can be determined directly, but there
are issues with introduction[1 point] Can be determined directly and can
expect introduction to be feasible

No.212■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is
unknown[3 points] Countermeasures exist, but throughput decreases
significantly due to suspension of task
[2 points] Countermeasures exist, but throughput decreases
due to workload limitations[1 point] No impact on throughput, or when 7-1 is 1 point

Weighted evaluation of important monitoring items
Item 7-1

Item 7-2

Item 7-3

extraction table)

8

error

Effects on accurate and prompt onsite response by workers

throughput due toerror handling

Inappropriate[Item 4]

Recriticality prevention- When using a neutron detector, aDuring theprocessing(a) Neutron

technology based on

direct determination can be made byapplication of theinappropriate

to criticality

due toflux

neutron absorbent

setting the neutron flux threshold.

neutronshape due todue to shapedripping

unaffected

application (temporary- The neutron detector is underdripping waterchangewater (poorby dripping

visibility)

water

3

12

24

24

24

(Indirect causes)

processed into an approaching(poor visibility),

DebrisdelaysSafetySaku-A-

Debris iserror

to avoid work

Impact on
Presence or absence ofcountermeasures for
disturbing functions

Point of representation

mechanism[Criticality]
Debrisprocessing
shapecontrolfunctioncauses ofrequirements

Individual

processing

causes of

Detection

Point

DebrisWork delay factor

IndirectPoint

equipment

DirectApplicable function

TargetThe
functionthat thetarget is
responsible
for

Point

Risk
assessment
table analysis
numberItem 7-4(Evaluation
Results)suspension of task) is

2

being developed in thedevelopment in the Fukushima Daiichi

absorbent,
2

subsidized project.

workload islimited according

and the debris

Fukushima Daiichi

to theapproaches thesubsidized project.

countermeasurestate of criticality

in item 7-1.
[Item 5]- When using camera images, it is(b) Debris

difficult to directly determine thedimensions

dimension of debris, and image

unaffected

processing is required.

by dripping- Droplets adhering to the camera

water

lens need to be blown off by gas or

Safety3Same as above

4other means (being developed in the2Same as above

project of investigation inside theRPV) or be treated to prevent

fogging.
- General cameras have low radiation
resistance in a high-dose radiation
environment, and there aredevelopment problems.

©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-3: Risk assessment table for operational equipment (Detailed version) (24/59)

No.213■ Risk assessment table■ Score table for item 7-1[4 points] No countermeasures have been
determined[3 points] Countermeasures exist, but they are still
under development[2 points] Countermeasures exist, but there are no
track records of application at the Fukushima Daiichi[1 point] Countermeasures exist, and have been
applied at the Fukushima Daiichi.

Model ID
Process
Work

Ko-3
Sa-4

: Debris retrieval:
Processing
debrisof■ Score table for item 7-2[4 points] Cannot be determined directly and there are issues withintroduction[3 points] Cannot be determined directly and can expect
introduction to be feasible[2 points] Can be determined directly, but there are issues withintroduction[1 point] Can be determined directly and can expect introduction to
be feasible

Important monitoring items
Item 1

Weighted evaluation of important monitoring items
Item 7-4

Item 4Item 5error

of errorto avoid work

delaysPresence or absence ofcountermeasures for
disturbing functions

Effects on accurate and prompt on-site
response by workers

Debris[Criticality]

Debris is

DebrisInappropriate

Recriticality prevention- When using a neutron detector, aprocessing

Debrisprocessed into

approachingprocessing due (a) Neutron

technology based on

direct determination can be made bymechanismprocessinganto criticality

to dustflux

neutron absorbent

setting the neutron flux threshold.

shapeinappropriate

due to shapedispersion

unaffected bycontrolshape due tochange(poor visibility)

dust

functiondust dispersion[Item 4]3

dispersion(poor visibility),

state ofcriticality

2- The neutron detector is undersuspension of task) isdevelopment in the Fukushima Daiichi

being developed in thesubsidized project.

2

During theapplication of theneutron absorbent,
workload is limited
according to thecountermeasure in
item 7-1.

12

24

24

24

Fukushima Daiichi

and the debris
approaches theapplication (temporary

Impact on
throughput due toerror handling(Indirect causes)

Point of representation

causes of

Detection
Indirect causes requirements

Safety9(Evaluation

Individual

Direct

for

Saku
-A-

Item 7-3

Pointfactorresponsible

Item 7-2

Pointtarget is

Work delay

Point

equipmentthat theItem 7-1

Results)

The function
TargetItem 6

Applicable function

Risk
assessment
table analysis
numberItem 2Item 3 (excerpt
from error
extraction table)■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is
unknown[3 points] Countermeasures exist, but throughput decreases
significantly due to suspension of task
[2 points] Countermeasures exist, but throughput decreases due toworkload limitations[1 point] No impact on throughput, or when 7-1 is 1 point

subsidized project.
[Item 5]- When using camera images, it is(b) Debris

difficult to directly determine thedimensions

dimension of debris, and image

unaffected byprocessing is required.

dust- Visibility evaluation of debris

dispersion

processing status for dust dispersion

Safety3Same as above4

has been studied in the dust collection

2

Same as above

project for the disc cutter, but otherprocessing methods have not been
evaluated.
- General cameras have low radiation
resistance in a high-dose radiation
environment, and there aredevelopment problems.

©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-3: Risk assessment table for operational equipment (Detailed version) (25/59)

No.214■ Risk assessment table■ Score table for item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still underdevelopment[2 points] Countermeasures exist, but there are no trackrecords of application at the Fukushima Daiichi[1 point] Countermeasures exist, and have been applied at the
Fukushima Daiichi.

Model ID
Process
Work

Ko-3
Sa-4

■ Score table for item 7-2[4 points] Cannot be determined directly and there are issues
with introduction[3 points] Cannot be determined directly and can expect
introduction to be feasible[2 points] Can be determined directly, but there are issues withintroduction[1 point] Can be determined directly and can expect
introduction to be feasible: Debris retrieval: Processing of debris
Important monitoring items

Item 1Risk
assessment
table
analysis
numberItem 2Item 3(Extracted
from the error
extraction
table )

Item 4Weighted evaluation of important monitoring items

Item 5Item 7-1

Item 7-2

Item 7-3

Item 7-4(Evaluation
results)of error

avoid work
delaysfor
Debris[Criticality]

Debris is

Debrisprocessing

Debrisprocessed

approaching processing due (a) Neutron flux

mechanismprocessing

into anto criticality

shape

inappropriate

due to shape ( poor visibility ) backgroundshape due tochangefunction

to noise[Item 4]
unaffected by

3

Safetycontrol

Inappropriate( noise )high

Effects on accurate and prompt on-site
response by workers( indirect causes )- When using a neutron detector, a direct

During thetechnology based on neutron

determination can be made by setting theapplication of theabsorbent application(temporary

neutron flux threshold.

suspension of task) is being

2

2

neutron absorbent,- The neutron detector is underaccording to thedeveloped in the Fukushima

development in the Fukushima Daiichi

measures in Item

Daiichi subsidized project.

subsidized project.

7-1.
Same as above[ Item 5]- When using camera images, it is difficult( noise ), and(b) Debris

to directly determine the shape andthe debris

dimensions

dimension of debris, and image

approaches

unaffected byprocessing is required.

the state of

background- Although camera noise caused by

Safety3

addressing errors

Recriticality prevention

background

criticality

Point of representation

error

Indirect causes requirements to

Individual

factorresponsible

causes of

12

24

24

24

throughput by
Presence or absence ofcountermeasures for disturbing
functions

Point

Work delay

Detection

Pointtarget is

DirectPointthat theApplicable function

equipment

10

Item 6

Impact on
The function

TargetSakuA-■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is unknown[3 points] Countermeasures exist, but throughput decreases significantly
due to suspension of task
[2 points] Countermeasures exist, but throughput decreases due toworkload limitations[1 point] No impact on throughput, or when 7-1 is 1 point

radiation from the PCV environment has
Same as above

4 also occurred in the project ofinvestigation inside the PCV, no major

2adverse effects have been reported in thevisual survey.
- The camera has low radiation resistancein a high-dose radiation environment, andthere are development problems.

©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-3: Risk assessment table for operational equipment (Detailed version) (26/59)■ Risk assessment table■ Score table for item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still underdevelopment[2 points] Countermeasures exist, but there are no trackrecords of application at the Fukushima Daiichi[1 point] Countermeasures exist, and have been appliedat the Fukushima Daiichi.

Model ID
ProcessWork- When using a neutron detector, a(Indirect causes)
During theby spraying neutron absorbent

direct determination can be madeapplication of the(temporary suspension of work) isby setting the neutron flux

neutron absorbent,

location of theunder development in the debris

threshold.

workload is limited

fall

retrieval project.

- The neutron detector is underaccording to the- In the debris retrieval project,

development in the Fukushima

concepts such as a support arm that

Daiichi subsidized project.

functions- A technology to prevent re-criticality

Debrisfall fromapproaching structure(a) Neutron flux

theto criticality

around theprocessing due to shapesite andcollide with3

the debris,causing the

supports the processed materials and adebris totray that catches falling objects areapproachbeing considered to prevent thethe state ofprocessing area from becoming brittle

criticality

site response by workers

2

throughput due toerror handlingcountermeasure in
item 7-1.

Point of2

countermeasures for disturbing

delays[Item 4]StructureschangeFall ofavoid work

representation

error

Impact on
Effects on accurate and prompt on-

requirements to

Item 7-4(Evaluation
Results)

Individual

error

Item 7-3

Point

11

causes ofPresence or absence of

Item 7-2

Point

A-

causes of

Detection

SafetySaku-

Indirect

Item 7-1

function[Criticality]
Debrisprocessing processing
mechanism shapecontrolfunction
DebrisDirectItem 6Point

The functionthat theWork delay
target isequipment responsible
factorfor
TargetNo.215■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is unknown[3 points] Countermeasures exist, but throughput decreases
significantly due to suspension of task
[2 points] Countermeasures exist, but throughput decreases due toworkload limitations[1 point] No impact on throughput, or when 7-1 is 1 point

Weighted evaluation of important monitoring items

ApplicableRisk
assessment
table analysis
number

Ko-3 : Debris retrieval
Sa-4 : Processing of debris
Important monitoring items
Item 3(excerpt
Item 2Item 1from error
Item 4Item 5extraction
table)■ Score table for item 7-2[4 points] Cannot be determined directly and there are issues
with introduction[3 points] Cannot be determined directly and can expect
introduction to be feasible[2 points] Can be determined directly, but there are issues
with introduction[1 point] Can be determined directly and can expect
introduction to be feasible

12

24

24

24

and falling by gravity.
[Item 5]

4

- The structural strength of(b) Structural

structures must be evaluated basedstrength ofon various parameters such as

structuredefects, strain, stress, and cracks,

leading to fall

making direct determination difficult.

mode- In general industry, there are non-

Safety3

destructive inspection equipment

Same as above(ultrasonic wave counter, etc.) for2

Same as above

evaluating the structural strength ofbridges and concrete tunnels, butthere are technological issues suchas radiation resistance in high-doseradiation environment and methodsof application to complex shapes.

©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-3: Risk assessment table for operational equipment (Detailed version) (27/59)

No.216■ Risk assessment table■ Score table for item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still
under development[2 points] Countermeasures exist, but there are no
track records of application at the Fukushima Daiichi[1 point] Countermeasures exist, and have been
applied at the Fukushima Daiichi.

Model ID
ProcessWork

responsible

Indirectcauses ofcauses of

error

error

requirements
to avoid work
delaysfor
Debris12

Excessive

error handling (Indirect
Presence or absence ofcountermeasures for
disturbing functions

Effects on accurate and prompt
on-site response by workers

causes)

Debris[Item 4]

Temporary suspension of*If it is difficult to use the- Addressing Item 7-1 will

dispersed by dust

processing(a) Dust

processing work eliminates

monitoring data of the safety

not be given 1 point since itmechanism dispersion

processing

beyondconcentration

excessive dust dispersion.

equipment in gas phase, theis contingent on a temporary

prevention

approaches

dust

at theExample measures exist forfollowing measures are required.

suspension of task.

function

the allowabledispersion

processing site

similar events in the- When using a dust sampler,- Throughput is assumed todust

prevention

concentration

function

dispersion

1

Item 7-4(Evaluation
Results)

Impact on throughput due toprocessing Dust

SafetySakuA-[Gas phase] The dust

Item 7-3

construction of the accessroute for the investigation

2 dust concentration can be
determined directly.

3

be significantly reduced due

Point ofrepresentation

factorDirectDetection

Item 7-2

Point

equipment target is

Work delay

Item 7-1

Pointthat theItem 6

Point

Target[4 points] No countermeasures, and impact on throughput is unknown[3 points] Countermeasures exist, but throughput decreases significantly due tosuspension of task
[2 points] Countermeasures exist, but throughput decreases due to workload
limitations[1 point] No impact on throughput, or when 7-1 is 1 point

Individualfunction■ Score table for item 7-3

Weighted evaluation of important monitoring items

Applicable function

Risk
assessment
table analysis
number

Ko-3 : Debris retrieval
Sa-4 : Processing ofdebrisImportant monitoring items
Item 3(excerpt from
Item 1
Item 2error
Item 4Item 5extraction
table)
The■ Score table for item 7-2[4 points] Cannot be determined directly and there are issues
with introduction[3 points] Cannot be determined directly and can expect
introduction to be feasible[2 points] Can be determined directly, but there are issues withintroduction[1 point] Can be determined directly and can expect
introduction to be feasible

6

12

12

12

to the unknown duration of

inside theinside the Fukushima Daiichi-- Technology is required totemporary suspension of

PCV

1 PCV.

measure dust concentration attask caused by addressing

the debris processing site in a

Item 7-1.

high-dose radiation environment.
[Item 5]- When using camera images, it is(b) Amount ofdifficult to directly determine theanti-dispersion

amount of mist reaching thereaching the1

Safetyagent (mist)

Same as above

4

processing area.

3

Same as above- The camera has low radiation

processing

resistance in a high-dosearearadiation environment, and there
are development problems.

©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-3: Risk assessment table for operational equipment (Detailed version) (28/59)

No.217■ Risk assessment table ■ Score table for item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still
under development[2 points] Countermeasures exist, but there are no
track records of application at the Fukushima Daiichi[1 point] Countermeasures exist, and have been
applied at the Fukushima Daiichi.

Model ID
Process

Ko-3

Work

Sa-4

■ Score table for item 7-2[4 points] Cannot be determined directly and there are issues
with introduction[3 points] Cannot be determined directly and can expect
introduction to be feasible[2 points] Can be determined directly, but there are issues withintroduction[1 point] Can be determined directly and can expect
introduction to be feasible: Debris retrieval:
Processing
debrisof
Important monitoring items

Item 1

Item 7-2

Item 7-3(Evaluation

Results)

Work delay

Direct causes

factorof error

Indirectcauses oferror

Detectionrequirements
to avoid work
delays

Impact on
Presence or absence ofcountermeasures for
disturbing functions

Effects on accurate and prompt on-site
response by workers

throughput byaddressing
errors (indirect

Poor

Structures[Item 4]

Technology to improve theIn the debris retrieval project “Support

Addressing

allow theaccessibility

at the(a) Time toaccessibility of the robot arm

method for remote operation of articulated

Item 7-1 isprocessing jig

to theprocessing reach theto the complexly arranged

MNP,” technology is being developed toassumed toto access theprocessing

site

structures inside the PCV is

support and evaluate the accessibility

area wherearea

processing

3

site

application of

9

9

9

9

causes)

It takes time to

Work

2

Item 7-1

Point ofrepresentation

mechanism

Item 6

Individual

processing

Fuel debris
processing
function

Item 5

Point

DebrisItem 7-4
Item 4Point

equipment

The functionthat the target
is responsiblefor

Weighted evaluation of important monitoring items

Applicable function

TargetItem 2Item 3 (excerpt
from error
extraction
table)

Point

Risk
assessment
table analysis
numberSaku-B-■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is unknown[3 points] Countermeasures exist, but throughput decreases
significantly due to suspension of task
[2 points] Countermeasures exist, but throughput decreases due toworkload limitations[1 point] No impact on throughput, or when 7-1 is 1 point

3

1

have low

under development in the

improvements to the processing area byimpact on

fuel debris retrieval project.

acquiring information on the layout ofthroughput.

external force

structures in advance and mechanicallyis desired

treating the information.
[Item 5]

Sampling equipment to be deployed during(b) Three-

the experimental fuel debris retrieval phasedimensional

will be equipped with technology forshapeacquiring information on the layout ofof the3Work(dimensions)

Same as above

3

structures using laser scanning, and the1Same as above

on-site demonstration testing is scheduled.

structure attheprocessing
site©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-3: Risk assessment table for operational equipment (Detailed version) (29/59)

No.218■ Risk assessment table■ Score table for item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still
under development[2 points] Countermeasures exist, but there are no
track records of application at the Fukushima Daiichi[1 point] Countermeasures exist, and have been
applied at the Fukushima Daiichi.

■ Score table for item 7-2[4 points] Cannot be determined directly and there are issues
with introduction[3 points] Cannot be determined directly and can expect
introduction to be feasible[2 points] Can be determined directly, but there are issues withintroduction[1 point] Can be determined directly and can expect
introduction to be feasible■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is unknown[3 points] Countermeasures exist, but throughput decreases significantly
due to suspension of task
[2 points] Countermeasures exist, but throughput decreases due toworkload limitations[1 point] No impact on throughput, or when 7-1 is 1 point

Model ID
Process

Ko-3

Work

Sa-4

: Debris retrieval: Processing ofdebrisImportant monitoring items

Item 1

Item 4Weighted evaluation of important monitoring items
Item 5causeserror

of errorfor3

to avoid work
delays

Effects on accurate and prompt on-site
response by workers

error handling(Indirect causes)

Fuel debris

Processing jigs

Excessive

Fuel[Item 4]

Technology for remotely- It is difficult to directly determine theAddressing Item 7-

processing

wear out quickly,

wear anddebris(a) Degree of

exchange processing jigs

wear and tear of processing jigs. For

1 is assumed tomechanism

functionand frequent

tear ofwear and tearsuch as a tool changer onvisual verification, training for operators

restrict work

replacement

processingof processing

site, is under development inin sensory inspection is required. For

temporarily.

the fuel debris retrieval

cases other than visual verification,

jigs

time-consuming

3

18

18

18

throughput due to
Presence or absence ofcountermeasures for
disturbing functions

processing

make processing jigs

18

Impact on

Debris

Work

Saku
-B-

requirements

Point of representation

factorcauses of

Detection

Item 7-4(Evaluation
Results)

Individual

responsible

Work delay

Indirect

Item 7-3

Point

equipment

target is

DirectItem 7-2

Point

Targetthat theItem 7-1

Applicable function

The function

Item 6Point

Risk
assessment
table analysis
numberItem 2Item 3 (excerpt
from error
extraction table)

project.

3

multiple data, such as jig vibration and2

motor output, must be obtained tomake a determination.
- General industrial technology can be[Item 5]

utilized for all of the above.
- It is difficult to directly determine the(b)compressive strength, as it isCompressivenecessary to collect a sample andstrength of

conduct a tensile test, etc.

be processed

3

Work

fuel debris toSame as above

3- Since the existing technology requires

2

Same as above

sample collection + hot lab testing, notbeing performed at the processing site,
there is a problem when measurement
is required on-site.

©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-3: Risk assessment table for operational equipment (Detailed version) (30/59)■ Risk assessment table
Model ID
Process
Work

Ko-3
Sa-4

: Debris retrieval: Processing of debris

Item 1error

avoid work

Presence or absence ofcountermeasures for
disturbing functions

Effects on accurate and prompt on-site
response by workers

Debris

Hot spots

Delayed[Item 4]The operational- When using a dosimeter, a direct

Throughput isprocessing

processing

appeardetermination(a) Degree ofprocedure of temporary

determination can be made by setting theassumed to bemechanism

functionand itof effects on

effects on

evacuation from the area

threshold dose based on the cumulative

significantly

takes timeradiationequipment

when a hot spot is

exposure dose of the operational equipment.

41

verified has been

1

- The dosimeter has been introduced in the field

against hot spots

the impact(radiation

incorporated in thedemonstration testing of the project ofof temporaryon

resistance)

investigation inside the3

investigation inside the PCV.

evacuation due toFukushima Daiichi-2(b) Sourceof the source cannot be determined directly due

Work

1

Same as above

3

processing site

- Development of technology to identify hot

3Same as above

Fuel debris

Mechanica

Insufficient[Item 4]The condition of waterrequired.
It is possible to make a direct determination by

Impact on

processing

processingl/thermaltransmission(a) Amount offlow inside the RPV,

the amount of debris throughput per day, andthroughput ismechanism

functionexternalof external

debris filling thewhere cooling water isintroduction is feasible

forces areforce to debris

not

flow

inner container

4

directly injected, is

1

9

16

32

32

32

unknown due to4inability to

unknown. In addition, no

determinetransmitted

countermeasures havecountermeasures

to debrisbeen considered.

for Item 7-1[Item 5]

When using a Price current meter, it is possible

obstruction(b) Coolingto directly determine the flow velocity, but thereby waterwater velocity

flow

and flow rate at

4

Work

due tothe fuel debris

9

spots in a high-dose radiation environment is

Work

u-B-

to the surrounding background.

DebrisWater

9Item 7-1.
- When using a dosimeter, the specific location

spots at theunknown duration

measures taken for[Item 5]location of hot

3

reduced due to theto assess

PCV.

5

error handling(Indirect causes)

delaysequipmentSakthroughput due toforFuel debris

Hot spot

Item 7-4(Evaluation
Results)

Impact on

Detectionrequirements to

Item 7-3

Point ofrepresentationof errorNo.219Individual

factorresponsible

causes of

Item 7-2

Point

Work delay Direct causes

Item 7-1

Pointtarget is

Indirect

Item 6Work

u-B-

Item 5

Applicable
functionTargetthat the■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is unknown[3 points] Countermeasures exist, but throughput decreases
significantly due to suspension of task
[2 points] Countermeasures exist, but throughput decreases due toworkload limitations[1 point] No impact on throughput, or when 7-1 is 1 point

Weighted evaluation of important monitoring items

The function

equipment

Sak

Important monitoring items
Item 3(excerpt
from error
Item 4extraction
table)■ Score table for item 7-2[4 points] Cannot be determined directly and there are issues
with introduction[3 points] Cannot be determined directly and can expect
introduction to be feasible[2 points] Can be determined directly, but there are issues withintroduction[1 point] Can be determined directly and can expect
introduction to be feasible

Point

Risk
assessment tableanalysis
numberItem 2■ Score table for item 7-1[4 points] No countermeasures have been
determined[3 points] Countermeasures exist, but they are still
under development[2 points] Countermeasures exist, but there are no
track records of application at the Fukushima Daiichi[1 point] Countermeasures exist, and have been
applied at the Fukushima Daiichi.

Same as above2

are problems because it requires assessing theradiation resistance of the flow meter in a high-4Same as above

dose radiation environment

processing site

©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-3: Risk assessment table for operational equipment (Detailed version) (31/59)■ Risk assessment table■ Score table for item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still
under development[2 points] Countermeasures exist, but there are no
track records of application at the Fukushima Daiichi[1 point] Countermeasures exist, and have been
applied at the Fukushima Daiichi.

Model ID
Process
Work

Ko-3
Sa-4

: Debris retrieval: Processing ofdebrisNo.220■ Score table for item 7-2[4 points] Cannot be determined directly and there are issues
with introduction[3 points] Cannot be determined directly and can expect
introduction to be feasible[2 points] Can be determined directly, but there are issues withintroduction[1 point] Can be determined directly and can expect
introduction to be feasible

Important monitoring items
Item 1

Item 5Item 6Item 7-1

target isfactorcauses oferror

Indirectcauses oferror

Detectionrequirements toavoid work delays

Darkness

Impact on

throughput due to
Presence or absence ofcountermeasures for
disturbing functions

error handlingon-site response by workers

4

Impact on

Effects on accurate and prompt(Indirect causes)

for
Fuel debris

Processing

Change in[Items 4/5]

In the debris retrieval- When using camera images, it isprocessing

processing

results

shape of(a) Dimensions ofproject, debris processing

difficult to directly determine thethroughput ismechanism

function(completion ofprocessed

processed debris

technology is being

dimension of debris, and image

unknown because

debrisdebris isunaffected bystudied, but

processing is required.

noshredding)unknown

darknesscountermeasures against- General cameras have low

countermeasuresradiation resistance in a high-dose

have beenradiation environment, and there

determined for Item

are development problems.

7-1

6

4

cannot beWork

Debrisobtained due tothis error have not been

4

studied in detail.

darkness, andPoint ofrepresentationequipment

DirectItem 7-4(Evaluation
Results)

Individual

Work delay

Item 7-3

Pointthat theItem 7-2

Point

TargetApplicable function

Thefunction

responsible

Saku
-B-

Item 4[4 points] No countermeasures, and impact on throughput is
unknown[3 points] Countermeasures exist, but throughput decreases
significantly due to suspension of task
[2 points] Countermeasures exist, but throughput decreases due
to workload limitations[1 point] No impact on throughput, or when 7-1 is 1 point

Weighted evaluation of important monitoring items

Point

Risk
assessment
table analysis
numberItem 2Item 3 (excerpt
from error
extraction table)■ Score table for item 7-3

64

64

64

64

having to reprocess takes

7

Fuel debris

time
Processing

Change in[Items 4/5]

In the debris retrieval- When using camera images, it isprocessing

processing

results

shape of(a) Dimensions ofproject, debris processing

difficult to directly determine thethroughput ismechanism

function(completion ofprocessed

processed debris

technology is being

dimension of debris, and image

unknown because

debrisdebris isunaffected by fog

studied, but

processing is required.

noshredding)unknowncountermeasures against- Image processing forcountermeasuresthis error have not beencountermeasures against fog andhave beenhalation suppression with lighting

determined for Item

fog, and having

are required.

7-1

to re-process- General cameras have low

takes timeradiation resistance in a high-dose

cannot beobtained due to

Fog

4

Function

Saku-B-

Debrisstudied in detail.

44

Impact onradiation environment, and there
are development problems.

©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-3: Risk assessment table for operational equipment (Detailed version) (32/59)■ Risk assessment table

Model ID
Process
Work

Ko-3
Sa-4

: Debris retrieval: Processing ofdebrisNo.221■ Score table for item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still
under development[2 points] Countermeasures exist, but there are no trackrecords of application at the Fukushima Daiichi[1 point] Countermeasures exist, and have been appliedat the Fukushima Daiichi.

■ Score table for item 7-2[4 points] Cannot be determined directly and there areissues with introduction[3 points] Cannot be determined directly and can expect
introduction to be feasible[2 points] Can be determined directly, but there are issues
with introduction[1 point] Can be determined directly and can expect
introduction to be feasible

Important monitoring items
Item 1

Item 7-2

Item 7-3

Presence or absence ofcountermeasures for
disturbing functions

throughput due toEffects on accurate and prompt on-site
response by workers

error handling(Indirect causes)

In the debris retrieval- When using camera images, it is

Impact on(a)project, debris

difficult to directly determine thethroughput isshredding) cannot beprocessed

Dimensions ofprocessing technology isdimension of debris, and image

unknown because

obtained due to dripping

debris isprocessed

being studied, but

processing is required.

nowater, and having to re-unknown

debriscountermeasures- Droplets adhering to the camera lenscountermeasures

unaffected byagainst this error haveneed to be blown off by gas or otherhave beenmeans (being developed in the project4 determined forof investigation inside the RPV) or be

Item 7-1

Processing results

processing

processing

mechanism

functionprocess takes time8

dripping water

4

Work

[Items 4/5]

(completion of debris

Fuel debris

not been studied in

4

detail.

Point ofrepresentation

Impact on

Change in Drippingwater
shape of

DebrisItem 7-4(Evaluation Results)

Individual

Detection
Indirectrequirements
causes of
to avoid work
error
delaysItem 7-1

Point

Work delay factor

Directcauses oferror

Item 6Point

The functionthat the target
is responsiblefor

Item 5

Applicable function

Saku
-B-

Targetequipment

Item 4Weighted evaluation of important monitoring items

Point

Risk
assessment
table
analysis
numberItem 2Item 3 (excerpt fromerror extraction table)■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is unknown[3 points] Countermeasures exist, but throughput decreases significantly due
to suspension of task
[2 points] Countermeasures exist, but throughput decreases due to workload
limitations[1 point] No impact on throughput, or when 7-1 is 1 point

64

64

64

64

treated to prevent fogging.
- General cameras have low radiation
resistance in a high-dose radiation
environment, and there are

9

In the debris retrieval

development problems.
- When using camera images, it is

Impact on(a)project, debris

difficult to directly determine the shapethroughput isprocessing technology isand dimension of debris, and image

unknown because

being studied, but

processing is required.

nodebriscountermeasures- Because the floating neutron

countermeasures

cutting (dust), andunaffected byagainst this error haveabsorbent has fluidity, it is possible toneutron absorbent

sediments,

floating in water, andpowders from

Fuel debris

Processing results

Change in Floatingprocessing

processing(completion of debris

shape ofmechanism

function

shredding) cannot be
obtained due toprocessed absorbent Dimensions ofprocessed
debris issediments, powder fromunknownhaving to re-process
takes time.

neutroncutting (dust),
or neutron
absorbents
floating in

4

Work

Saku
-B-

[Items 4/5]

Debrisnot been studied indetail.

4

ensure visibility with artificial water flow.
- The camera has low radiation

have been4

determined for
Item 7-1

resistance in a high-dose radiation
environment, and there aredevelopment problems.

water©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-3: Risk assessment table for operational equipment (Detailed version) (33/59)■ Risk assessment table

No.222■ Score table for item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still underdevelopment[2 points] Countermeasures exist, but there are no trackrecords of application at the Fukushima Daiichi[1 point] Countermeasures exist, and have been applied at the
Fukushima Daiichi.

Model ID
Process
Work

Item 6Item 7-1

Item 7-2

Item 7-3

Item 7-4(Evaluation
Results)

causesof error

Effects on accurate andprompt on-site response by

due to error handling(Indirect causes)

workers

Fuel debris

Debris does Low fuel[Item 4]The condition of water

It is possible to make a

Impact on throughput

sourcecollection

not fit in the collection(a) Amount offlow inside the RPV,

direct determination by theis unknown due tocollection

function

innerdebris filling thewhere cooling water isamount of debris throughput

inability to determine

inner container

directly injected, isper day, and introduction iscountermeasures forunknown. In addition, no

feasible

rate

container
due toobstruction

Water
flow

4

Work

Radiationby thecountermeasures have

1

4

Item 7-1

Point ofrepresentation

factorPresence or absence ofcountermeasures for
disturbing functions

Individual

is responsible

Indirectrequirements tocausesof error avoid work
delaysPointequipment

DirectPointthat the target Work delay

Detection

Applicable
functionTargetmechanism
10

Weighted evaluation of important monitoring items

Impact on throughput
The functionfor

SakuB-■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is unknown[3 points] Countermeasures exist, but throughput decreases significantly
due to suspension of task
[2 points] Countermeasures exist, but throughput decreases due toworkload limitations[1 point] No impact on throughput, or when 7-1 is 1 point

Ko-3

Point

Risk
assessment
table
analysis
number: Debris retrieval: Processing of
Sa-4
debrisImportant monitoring items
Item 3(excerpt
Item 1
Item 2from error
Item 4Item 5extraction
table)■ Score table for item 7-2[4 points] Cannot be determined directly and there are issues
with introduction[3 points] Cannot be determined directly and can expect
introduction to be feasible[2 points] Can be determined directly, but there are issues withintroduction[1 point] Can be determined directly and can expect
introduction to be feasible

16

32

32

32

been considered.

water flow.
(Flowsaway[Item 5]

When using a Price current(b) Coolingmeter, it is possible towater velocity

directly determine the flow

the fuel debris
collection area

4

Work

and flow rate atvelocity, but there areSame as above2

problems because it

4

Same as above

requires assessing theradiation resistance of theflow meter in a high-doseradiation environment©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-3: Risk assessment table for operational equipment (Detailed version) (34/59)■ Risk assessment table■ Score table for item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still underdevelopment[2 points] Countermeasures exist, but there are no track records
of application at the Fukushima Daiichi[1 point] Countermeasures exist, and have been applied at the
Fukushima Daiichi.

Model ID
Process
Work

Ko-3
Sa-4

Item 1

Impact on throughput
Presence or absence of countermeasuresfor disturbing functions

Effects on accurate and prompt
on-site response by workers

due to error handling(Indirect causes)- In the case of debris pick-up operation for

It is possible to make a direct

Among the measures(a) Amount ofcollecting debris into the inner container,

determination by the amount offor Item 7-1, there isdebris fillingsemi-automated repetitive operations thatdebris throughput per day, anda possibility that

introduction is feasible

operator intervention

collection(poor

mechanism

visibility),

the inner

do not rely on environmental

collection

container

measurements on site are present in

the inner

4container

Work

11

Item 7-3[Item 4]of debris in

SakuB-

Item 7-2

8

24

24

24

may reduce the task

general industrial technology and are
expected to reduce disturbing work from

Item 7-4(Evaluation
Results)

Point ofrepresentation

Detectionrequirements
to avoid work
delaysItem 7-1

Individualrate■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is unknown[3 points] Countermeasures exist, but throughput decreases significantly due to suspension oftask[2 points] Countermeasures exist, but throughput decreases due to workload limitations[1 point] No impact on throughput, or when 7-1 is 1 point

Point

sourceItem 6

Point

Radiation

No.223Weighted evaluation of important monitoring items

Applicable
functionTargetequipment

Important monitoring items
Item 3(excerpt
Item 2from error
Item 4Item 5extraction
table)
The functionthat theDirectIndirect
Work delay
target iscauses of causes offactorresponsible
error
error
for
Fuel debris Due to
Low fuel Darkness
collection
darkness collection
function

Point

Risk
assessment
table
analysis
number: Debris retrieval: Processing of debris■ Score table for item 7-2[4 points] Cannot be determined directly and there are issues withintroduction[3 points] Cannot be determined directly and can expect introduction to
be feasible[2 points] Can be determined directly, but there are issues withintroduction[1 point] Can be determined directly and can expect introduction to befeasible

speed.

12

the environment (poor visibility) inside thetakes time

PCV.
- Some shapes of the debris may require
trajectory correction through operator
manipulation, and there are development
problems.
[Item 5]- The operator's trajectory(b) Relative

correction measures (e.g.,position ofminute misalignment between

debris anddebris and inner container) for

inner

semi-automated operations

container

shown in Item 7-1 cannot be

unaffected by
3

Work

darknessdetermined directly when using
Same as above

4

camera images, as it requires

2

Same as above

discernment based on
proficiency.

- When detecting with camera +lighting, impact assessment ofradiation resistance in a highdose radiation environment isrequired.

©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-3: Risk assessment table for operational equipment (Detailed version) (35/59)■ Risk assessment table

Model ID
Process
Work

Ko-3
Sa-4

: Debris retrieval: Processing of debris
Important monitoring items
Item 3(excerpt
Item 1
Item 2from error
Item 4Item 5extraction
table)

Indirecttarget isdelaycauses ofcausesresponsible

factorerror

of errorfor

12delaysthroughput due
Presence or absence of countermeasuresfor disturbing functions

Effects on accurate and prompt on-site response
by workers

to errorhandling

Among thecollection(a) Amount offor collecting debris into the inneramount of debris throughput per day, andmeasures for

rate

debris filling thecontainer, semi-automated repetitive

introduction is feasible

Item 7-1, there

inner container

operations that do not rely on

is a possibilityof debris

environmental measurements on site arethat operator

in thepresent in general industrial technology

sourcecollection(poorcollection

functionvisibility),collection

4

inner

and are expected to reduce disturbing

2
4

24

intervention
1

2

work from the environment (poor visibility)

container

24

causes)
It is possible to make a direct determination by theDue to fog Low fuel8

(Indirect- In the case of debris pick-up operation

Fuel debris

Work

SakuB-

avoid work

Item 7-4(Evaluation
Results)

Impact on[Item 4]

Radiationmechanism

Fogrequirements to

Item 7-3

Point ofrepresentation

DirectDetection

Item 7-2

IndividualWork■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is unknown[3 points] Countermeasures exist, but throughput decreases significantly due tosuspension of task
[2 points] Countermeasures exist, but throughput decreases due to workload
limitations[1 point] No impact on throughput, or when 7-1 is 1 point

Point

that theItem 7-1

Point

Targetequipment

Item 6

Applicable function

The function■ Score table for item 7-2[4 points] Cannot be determined directly and there are issues
with introduction[3 points] Cannot be determined directly and can expect
introduction to be feasible[2 points] Can be determined directly, but there are issues withintroduction[1 point] Can be determined directly and can expect introduction
to be feasible

Weighted evaluation of important monitoring items

Point

Risk
assessment
table
analysis
number

No.224■ Score table for item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still
under development[2 points] Countermeasures exist, but there are no
track records of application at the Fukushima Daiichi[1 point] Countermeasures exist, and have been
applied at the Fukushima Daiichi.

may reduce thetask speed.

inside the PCV.

takes time

- Some shapes of the debris may require
trajectory correction through operator
manipulation, and there are development
problems.

[Item 5]- The operator's trajectory correction measures(b) Relative(e.g., minute misalignment between debris andposition of

inner container) for semi-automated operations

debris andshown in Item 7-1 cannot be determined directly

inner container

when using camera images, as it requires

fog

3

Work

unaffected bySame as above

4

discernment based on proficiency.
- Cameras generally have image processing and2 Same as above

lighting adjustment (halation suppression)technologies for dealing with fog.

- The camera has low radiation resistance in ahigh-dose radiation environment, and there aredevelopment problems.

©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-3: Risk assessment table for operational equipment (Detailed version) (36/59)■ Risk assessment table
Model ID
Process

Ko-3: Debris retrieval

Work

Sa-4

: Processing of debris

Radiation
sourcecollection

Item 5Item 6Item 7-1

Dripping[Item 4]

- In the case of debris pick-up operation

It is possible to make a direct determination by

Among thecollection water(a) Amount offor collecting debris into the inner

the amount of debris throughput per day, andmeasures for Item

functionwater (poorratedebris filling

container, semi-automated repetitive

introduction is feasible

7-1, there is a

visibility),

the inner

operations that do not rely on

possibility thatcollection ofcontainer

environmental measurements on site

operator

Effects on accurate and prompt on-site response
by workers

Point

Low fuel

dripping

Point

Presence or absence ofcountermeasures for disturbing
functionsthroughput bycollection

are present in general industrial

inner

4

container
takes time

Item 7-4(Evaluation Results)

Impact on

Fuel debris Due to

Work

13

Item 7-3

Indirectrequirements
causes of
to avoid work
error
delaysdebris in the
SakuB-

Item 7-2

Directcauses of
error

Point

mechanism

Weighted evaluation of important monitoring items

DetectionWork delay
factor

No.225technology and are expected to reduce

addressing errors(indirect causes)

Point ofrepresentation

TargetequipmentThefunctionthat thetarget is
responsible
for

Risk
assessment
table analysis
number■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is unknown[3 points] Countermeasures exist, but throughput decreases significantly due tosuspension of task
[2 points] Countermeasures exist, but throughput decreases due to workload
limitations[1 point] No impact on throughput, or when 7-1 is 1 point

Individual

Item 2

Important monitoring items
Item 3(excerpt fromerror
Item 4extraction
table)

Applicable function

Item 1■ Score table for item 7-2[4 points] Cannot be determined directly and there are issues
with introduction[3 points] Cannot be determined directly and can expect
introduction to be feasible[2 points] Can be determined directly, but there are issues
with introduction[1 point] Can be determined directly and can expect
introduction to be feasible■ Score table for item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still underdevelopment[2 points] Countermeasures exist, but there are no trackrecords of application at the Fukushima Daiichi[1 point] Countermeasures exist, and have been appliedat the Fukushima Daiichi.

8

24

24

24

intervention may
1

2 reduce the task

disturbing work from the environment

speed.

(poor visibility) inside the PCV.

- Some shapes of the debris may
require trajectory correction throughoperator manipulation, and there aredevelopment problems.
[Item 5]- The operator's trajectory correction measures(b) Relative(e.g., minute misalignment between debris andposition of

inner container) for semi-automated operations

debris andshown in Item 7-1 cannot be determined directly

innerwhen using camera images, as it requires

unaffected by

3

Work

container

discernment based on proficiency.
Same as above

4- In general, there are technologies such as

dripping

blowing off droplets adhering to the camera lens

waterwith gas, etc., and hydrophilic coating.

2

Same as above- The camera has low radiation resistance in ahigh-dose radiation environment, and there aredevelopment problems.

©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-3: Risk assessment table for operational equipment (Detailed version) (37/59)■ Risk assessment table

Model ID
Process
Work

Ko-3
Sa-4

Item 2

Important monitoring items
Item 3(excerpt fromerror
Item 4extraction
table)

Item 7-3

Point ofrepresentation

Effects on accurate and prompt on-site response byworkers

8

24

2

24

24

throughput due
to error handling(Indirect causes)

Fuel debris

Due toLow fuel

Floating[Item 4]

- In the case of debris pick-up operation

It is possible to make a direct determination by theAmong thesourcecollection

sediments,

collection

neutron(a) Amount offor collecting debris into the inneramount of debris throughput per day, andmeasures forcollection

function

powder fromrate

absorbent

debris filling thecontainer, semi-automated repetitive

introduction is feasible

Item 7-1, there is

inner container

operations that do not rely on

cutting (dust),

a possibility thatenvironmental measurements on site areoperatorpresent in general industrial technology

absorbentintervention may

and are expected to reduce disturbing
4

water (poorWorkfloating in thevisibility),

Item 7-4(Evaluation
Results)

reduce the task
2 speed.

Impact on

Presence or absence ofcountermeasures for disturbing functions

Radiationand neutron

14

Item 7-2

Individual

Detectionrequirements toavoid work delays

Item 7-1

Point

Indirectcauses oferror

Item 6

Point

Directcauses oferror

Item 5Point

The functionthat the target Work delay
is responsible factor
for

Weighted evaluation of important monitoring items

Applicable function

Targetequipment

mechanism

SakuB-

No.226■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is unknown[3 points] Countermeasures exist, but throughput decreases significantly due tosuspension of task
[2 points] Countermeasures exist, but throughput decreases due to workload
limitations[1 point] No impact on throughput, or when 7-1 is 1 point: Debris retrieval: Processing of debris

Item 1Risk
assessment
table
analysis
number■ Score table for item 7-2[4 points] Cannot be determined directly and there are issues
with introduction[3 points] Cannot be determined directly and can expect
introduction to be feasible[2 points] Can be determined directly, but there are issues
with introduction[1 point] Can be determined directly and can expect
introduction to be feasible■ Score table for item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still
under development[2 points] Countermeasures exist, but there are no
track records of application at the Fukushima Daiichi[1 point] Countermeasures exist, and have been
applied at the Fukushima Daiichi.

work from the environment (poor1visibility) inside the PCV.
- Some shapes of the debris may require

collection of

trajectory correction through operator

debris in the

manipulation, and there are development

inner

problems.

container
takes time
[Item 5]- The operator's trajectory correction measures (e.g.,(b) Relative position

minute misalignment between debris and innerof debris and innercontainer) for semi-automated operations shown incontainer

Item 7-1 cannot be determined directly when using

unaffected bycamera images, as it requires discernment based onfrom cutting (dust),

3

Work

sediments, powder

Same as above

4

proficiency.

Same as above- Because the floating neutron absorbent hasor neutron

fluidity, it is possible to ensure visibility with artificial

absorbent floating inwater flow.

water- The camera has low radiation resistance in a highdose radiation environment, and there aredevelopment problems.

©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-3: Risk assessment table for operational equipment (Detailed version) (38/59)■ Risk assessment table■ Score table for item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still underdevelopment[2 points] Countermeasures exist, but there are no trackrecords of application at the Fukushima Daiichi[1 point] Countermeasures exist, and have been applied at
the Fukushima Daiichi.

Model ID
Process
Work

Ko-3
Sa-4

: Debris retrieval: Processing of debris

Item 1

Item 2

Risk

Item 5error

Low fuel

sourcecollection

backgroundcollection

function(noise),Noise

to avoid work
delaysthroughput
Presence or absence of countermeasures for
disturbing functions

Effects on accurate and prompt on-site
response by workers

due to error
handling(Indirect
causes)[Item 4]

- In the case of debris pick-up operation for

It is possible to make a direct determination

Among thecollection(a) Amount ofcollecting debris into the inner container, semi-by the amount of debris throughput per day,measures for

rate

debris filling

automated repetitive operations that do not rely on

and introduction is feasible

Item 7-1,

collection of

the innerdebris in thecontainer

inner

environmental measurements on site are present in
4

container
takes time

there is a

general industrial technology and are expected toreduce disturbing work from the environment (poorpossibility that1

2intervention- Some shapes of the debris may require trajectory

may reduce

correction through operator manipulation, and there

the task

are development problems.

speed.
- The operator's trajectory correction(b) Relative

measures (e.g., minute misalignment

position of

between debris and inner container) for

debris andsemi-automated operations shown in Item 7-

inner

1 cannot be determined directly when using

container

camera images, as it requires discernment
3

Work

noise

operator

visibility) inside the PCV.

[Item 5]

unaffected by

Point oferror

requirements

Impact on

representation

causes ofDue to highItem 7-4(Evaluation

Individual

causes of

Fuel debris

Item 7-3

Point

Indirect

Detection

Work

15

responsible forfactorDirectRadiationmechanism
SakuB-

that the target is

Work delay

Item 7-2

Point

equipment

The function

Item 7-1

Point

TargetItem 6

Results)

table analysis
number

No.227■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is unknown[3 points] Countermeasures exist, but throughput decreases significantly due tosuspension of task
[2 points] Countermeasures exist, but throughput decreases due to workload
limitations[1 point] No impact on throughput, or when 7-1 is 1 point

Weighted evaluation of important monitoring items

Applicable function

assessment

Important monitoring items
Item 3(excerpt fromerror
Item 4extraction
table)■ Score table for item 7-2[4 points] Cannot be determined directly and there are issues
with introduction[3 points] Cannot be determined directly and can expect
introduction to be feasible[2 points] Can be determined directly, but there are issues
with introduction[1 point] Can be determined directly and can expect
introduction to be feasible

based on proficiency.
Same as above4- Although camera noise caused by radiation

2

Same as
above

8

24

24

24

from the PCV environment has also occurredin the project of investigation inside the PCV,no major adverse effects have been reported
in the visual survey.
- The camera has low radiation resistance ina high-dose radiation environment, and there
are development problems.

©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-3: Risk assessment table for operational equipment (Detailed version) (39/59)■ Risk assessment table
Model ID
Process

Ko-3: Debris retrieval

Work

Sa-4

: Processing of debris

Item 1

Important monitoring items
Item 3 (excerpt
from error
Item 4extraction
table)■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is
unknown[3 points] Countermeasures exist, but throughput decreases
significantly due to suspension of task
[2 points] Countermeasures exist, but throughput decreases
due to workload limitations[1 point] No impact on throughput, or when 7-1 is 1 point

No.228Weighted evaluation of important monitoring items
Item 5Item 6Item 7-1

Item 7-2

Item 7-3

Item 7-4(Evaluation
Results)

Direct causes

factorof error

Indirectcauses of
error

for

Fuel debris

Cannot verify

Unknownsourcecollection

whether thecollection

functiondebris has

Darkness

Presence or absence ofcountermeasures for disturbing
functionsto error
Effects on accurate and prompt on-site
response by workers

handling(Indirect- In the project of further increasing- In the project of further increasing the

Impact on

amount of fuel(a) Amount of

the retrieval scale, technology isretrieval scale, technology to collect a small

throughput isdebris fillingdebris filling thebeing developed to collect a small

amount of debris using a camera in a capsule

unknown

been collected the inner

inner container

amount of debris

isolated from the PCV environment is being

because thein the innercontainer

unaffected by- In the large-scale retrieval phase,developed, and operational tests are being

container due(overflowing

darknessto darkness

from the innerabove project can be expected, but- In the large-scale retrieval phase,

7-1 is not(poor visibility) container, etc.)

detailed studies and technologicalapplication of the technology in the above

determineddevelopment have not been carriedproject can be expected, but detailed studies

out

and technological development have not

3

24

24

24

24

causes)[Items 4/5]

Work

16

avoid work
delaysRadiationmechanism

requirements to

Point

Work delay

throughput due

Pointthat the target

Point

TargetDetection

Point of representation

The function

Individual

Impact on

equipment is responsible

SakuB-■ Score table for item 7-2[4 points] Cannot be determined directly and there are issues
with introduction[3 points] Cannot be determined directly and can expect
introduction to be feasible[2 points] Can be determined directly, but there are issues
with introduction[1 point] Can be determined directly and can expect
introduction to be feasible

Applicable function

Risk
assessmenttable
analysis
numberItem 2■ Score table for item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still underdevelopment[2 points] Countermeasures exist, but there are no trackrecords of application at the Fukushima Daiichi[1 point] Countermeasures exist, and have been appliedat the Fukushima Daiichi.

application of the technology in the

2 conducted by the operators.

response
4 shown in Item

been carried out
Radiation

Fuel debris

Cannot verify

Unknownsourcecollection

whether thecollection

functiondebris hasmechanism
17[Items 4/5]

- In the project of further increasing- In the project of further increasing the

Impact on

amount of fuel(a) Amount of

the retrieval scale, technology isretrieval scale, technology to collect a small

throughput isdebris fillingdebris filling thebeing developed to collect a small

amount of debris using a camera in a capsule

unknown

been collected the inner

inner container

amount of debris

isolated from the PCV environment is being

because thein the innercontainer

unaffected by fog- In the large-scale retrieval phase,developed, and operational tests are being

container due(overflowing

to fog (poorfrom the innerabove project can be expected, but- In the large-scale retrieval phase,

7-1 is not

visibility)

container, etc.)

detailed studies and technologicalapplication of the technology in the above

determineddevelopment have not been carriedproject can be expected, but detailed studies

out

and technological development have not

3

Work

SakuB-

Fog

application of the technology in the

2 conducted by the operators.

response
4 shown in Item

been carried out©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-3: Risk assessment table for operational equipment (Detailed version) (40/59)

No.229■ Risk assessment table■ Score table for item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still
under development[2 points] Countermeasures exist, but there are no
track records of application at the Fukushima Daiichi[1 point] Countermeasures exist, and have been
applied at the Fukushima Daiichi.

Model ID
Process
Work

Ko-3
Sa-4

■ Score table for item 7-2[4 points] Cannot be determined directly and there are issues
with introduction[3 points] Cannot be determined directly and can expect
introduction to be feasible[2 points] Can be determined directly, but there are issues withintroduction[1 point] Can be determined directly and can expect
introduction to be feasible: Debris retrieval: Processing ofdebrisImportant monitoring items

Item 1

Item 4Item 5

Direct causesof error

responsible

causes of
error

for
Radiation

Fuel debris

sourcecollection

collection

functionmechanism

Cannot verify
whether thedebris has beencollected in the
inner container
due to dripping
water (poorvisibility)

Unknown

Dripping
water

requirements toavoid work
delays- In the project of further- In the project of further

Impact on(a) Amount of

increasing the retrieval scale,increasing the retrieval scale,throughput isfuel debris

debris filling thetechnology is being developed totechnology to collect a small

unknown

filling theinner containercollect a small amount of debris

amount of debris using abecause theinnerunaffected by- In the large-scale retrieval

camera in a capsule isolated

response shown

container

dripping waterphase, application of thefrom the PCV environment is

in Item 7-1 is nottechnology in the above project

being developed, anddetermined

can be expected, but detailed

operational tests are beingfrom the
inner

3

Work

18

Effects on accurate andprompt on-site response byworkers[Items 4/5]

amount of(overflowing
SakuB-

Presence or absence ofcountermeasures for disturbing
functions

Impact on
throughput due
to error handling(Indirect causes)2

studies and technologicalconducted by the operators.

container,

development have not been

- In the large-scale retrieval

etc.)

carried out

phase, application of the4

Item 7-4(Evaluation
Results)

Individual

Work delay factor

Detection

Item 7-3

Pointtarget is

Indirect

Item 7-2

Pointthat theItem 7-1

Point ofrepresentation

The function

Item 6Point

equipment

Item 3 (excerpt
from error
extraction table)

Weighted evaluation of important monitoring items

Applicable function

Risk
assessment
table
analysis
numberTargetItem 2■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is unknown[3 points] Countermeasures exist, but throughput decreases significantly
due to suspension of task
[2 points] Countermeasures exist, but throughput decreases due toworkload limitations[1 point] No impact on throughput, or when 7-1 is 1 point

24

24

technology in the above project
can be expected, but detailed
studies and technologicaldevelopment have not been
carried out©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-3: Risk assessment table for operational equipment (Detailed version) (41/59)■ Risk assessment table

Model ID
Process
Work

Ko-3
Sa-4

: Debris retrieval:
Processing
debris■ Score table for item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still underdevelopment[2 points] Countermeasures exist, but there are no trackrecords of application at the Fukushima Daiichi[1 point] Countermeasures exist, and have been appliedat the Fukushima Daiichi.

ofNo.230■ Score table for item 7-2[4 points] Cannot be determined directly and there are issues
with introduction[3 points] Cannot be determined directly and can expect
introduction to be feasible[2 points] Can be determined directly, but there are issues withintroduction[1 point] Can be determined directly and can expect
introduction to be feasible

Important monitoring items
Item 1

Item 7-3

Fuel debris

Cannot verify

Unknown

Floating[Items 4/5]

- In the project of further

2- In the project of further increasing the

Impact on

sourcecollection

whether the debris

amount ofneutronAmount ofincreasing the retrieval scale,retrieval scale, technology to collect athroughput iscollection

functionhas been collected in fuel debris

technology is being

small amount of debris using a camera in a

unknowndeveloped to collect a small

capsule isolated from the PCV

because theamount of debris

environment is being developed, andresponse shown- In the large-scale retrieval

operational tests are being conducted byphase, application of thethe operators.

technology in the above- In the large-scale retrieval phase,project can be expected, but

application of the technology in the above

absorbent

detailed studies andproject can be expected, but detailed

floating intechnological development

studies and technological development

water[Items 4/5]

have not been carried out- In the project of further increasing the

Impact on(a) Amount of

increasing the retrieval scale,retrieval scale, technology to collect athroughput istechnology is being

small amount of debris using a camera in a

unknowndeveloped to collect a small

capsule isolated from the PCV

because theamount of debris

environment is being developed, andresponse shown- In the large-scale retrieval

operational tests are being conducted byphase, application of thethe operators.

technology in the above- In the large-scale retrieval phase,the inner container

filling thethe inner

due to sediments,

inner

container

powder from cutting

container

unaffected by(dust), and neutron
absorbent floating in(overflowing

sediments,from thepowder fromwater (poor visibility) inner

cutting (dust),

container,or neutron

etc.)

Noise

Fuel debris

Cannot verify

Unknownsourcecollection

whether the debris

amount ofcollection

functionhas been collected in fuel debris

debris fillingthe inner container

filling thethe inner

due to highinner

container

background (noise)container

unaffected by(overflowing

noisefrom theinnercontainer,etc.)- In the project of further

3

Work

Radiationmechanism

3

Work

Saku19B-

absorbent debris filling

project can be expected, but
detailed studies andtechnological development

have not been carried out

4in Item 7-1 is not

Item 7-4(Evaluation
Results)

Point ofrepresentation

Impact on
throughput due
to error handling(Indirect causes)

Radiationmechanism

20

Presence or absence ofcountermeasures for
disturbing functions

Item 7-2

Individual

Detection
Indirectrequirements
causes of
to avoid work
error
delaysItem 7-1

Effects on accurate and prompt on-site
response by workers

equipment

SakuB-

Item 6

Point

Work delay factor

Directcauses oferror

Item 5Point

Item 4

Applicable
function

The function thatthe target is
responsible for

Item 3 (excerpt fromerror extraction table)

Weighted evaluation of important monitoring items

Point

Risk
assessment
table analysis
numberTargetItem 2■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is unknown[3 points] Countermeasures exist, but throughput decreases significantly due tosuspension of task
[2 points] Countermeasures exist, but throughput decreases due to workload
limitations[1 point] No impact on throughput, or when 7-1 is 1 point

24

24

24

24

determined

have not been carried out
2in Item 7-1 is not4

determined

application of the technology in the above
project can be expected, but detailed
studies and technological development
have not been carried out©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-3: Risk assessment table for operational equipment (Detailed version) (42/59)■ Risk assessment table■ Score table for item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still
under development[2 points] Countermeasures exist, but there are no
track records of application at the Fukushima Daiichi[1 point] Countermeasures exist, and have been
applied at the Fukushima Daiichi.

Model ID
Process

Ko-3

Work

Sa-5

■ Score table for item 7-2[4 points] Cannot be determined directly and there are issues
with introduction[3 points] Cannot be determined directly and can expect
introduction to be feasible[2 points] Can be determined directly, but there are issues withintroduction[1 point] Can be determined directly and can expect
introduction to be feasible■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is unknown[3 points] Countermeasures exist, but throughput decreases significantly
due to suspension of task
[2 points] Countermeasures exist, but throughput decreases due toworkload limitations[1 point] No impact on throughput, or when 7-1 is 1 point: Debris retrieval: Various records following processing work
Important monitoring items
Item 3(excerpt
Item 1
Item 2from error
Item 4Item 5extraction
table)

that the target

equipmentis responsibleforDirectIndirectdelay

causescausesfactorof errorof error

Item 7-1

Detectionrequirements toavoid work

delaysPoint

Applicable
function

Item 7-2

Presence orabsence ofcountermeasuresfor disturbing
functions

Point

Item 7-3

Effects on

Impact on throughput

accurate anddue to error handling

prompt on-site response(Indirect causes)

Item 7-4(Evaluation
Results)

Point ofrepresentation

TargetWork

Item 6

Individual

The function

Weighted evaluation of important monitoring items

Point

Risk
assessment tableanalysis
number

No.231

by workers

No environmental changes inside the PCV

No task disturbing©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-3: Risk assessment table for operational equipment (Detailed version) (43/59)■ Risk assessment table
Model ID

Process
Work

Ko-3
Sa-6

: Debris retrieval: Cell transfer of debris■ Score table for item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still underdevelopment[2 points] Countermeasures exist, but there are no trackrecords of application at the Fukushima Daiichi[1 point] Countermeasures exist, and have been applied at
the Fukushima Daiichi.

■ Score table for item 7-2[4 points] Cannot be determined directly andthere are issues with introduction[3 points] Cannot be determined directly and can
expect introduction to be feasible[2 points] Can be determined directly, but there
are issues with introduction[1 point] Can be determined directly and can
expect introduction to be feasible

Important monitoring items
Item 1

Item 4Weighted evaluation of important monitoring items
Item 5Item 6Item 7-1

The

factorresponsi

Indirectcauses of

error

error

requirements toavoid work
delaysble for1

for disturbing functions

Effects on accurate andprompt on-site response
by workers

Fuel

Presence orDelay in

[Items 4/5]

- Investigation inside the Fukushima Daiichi-- Direct determination is

The safety

debrisabsence ofascertaining(a) Presence of

2 PCV shows the effectiveness of thepossible if 3D scans ormeasures forcollection interfering

the presence

interfering

method that confirms the presence orother dimensional

each feature offunction

objects cannot

or absence

objects

absence of interfering objects on the task

acquisitions are madeeach method

be determinedof interfering

unaffected byroute in advance using dedicated equipment,- Detailed investigation

shown in Item 7-

due to darkness,

objects

darkness

and application of a similar method is

inside the Fukushima

Cell transfer
mechanism

3

Darknessand verification

SafetySaku-A-Presence or absence of countermeasures

Impact on
throughput due
to error handling(Indirect causes)

assumed.

1

Daiichi-2 PCV shows theItem 7-4(Evaluation
Results)

Point ofrepresentation

target is

Directcauses of

Item 7-3

Point

Work delay

Point

that thePoint

Targetequipment

Detection

Item 7-2

Individualfunction

Applicable function

Risk
assessment
table
analysis
numberItem 2Item 3 (excerpt
from error
extraction table)

No.232■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is
unknown[3 points] Countermeasures exist, but throughput decreases
significantly due to suspension of task
[2 points] Countermeasures exist, but throughput decreases due
to workload limitations[1 point] No impact on throughput, or when 7-1 is 1 point

3

3

3

3

1 are given 1
1point becauseof safety on the- Since fuel debris will be transferred during

application of laser

no element thattransfer route

this task, it is assumed that additional safety

scanning technology togreatly restrict

takes timemeasures will be required, and 2 points willobtain maintenancework arebe given. These countermeasures are being

information on interfering

extracted.

studied for each feature of each method of

objects.

debris retrieval project.

2

Presence orDelay in

[Items 4/5]

debrisabsence ofascertaining(a) Presence ofcollection interfering

the presence

interferingfunctionor absence

objects

objects cannot

Cell transfer

be verified due to of interfering

mechanism

fog, andobjects

Fog

unaffected by fog

3

Safety

Saku
-A-

Fuel

Same as above

1

Same as above

1

Same as above

verification ofsafety on thetransfer routetakes time

©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-3: Risk assessment table for operational equipment (Detailed version) (44/59)■ Risk assessment table

Process
Work

Ko-3
Sa-6

■ Score table for item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still
under development[2 points] Countermeasures exist, but there are no
track records of application at the Fukushima Daiichi[1 point] Countermeasures exist, and have been
applied at the Fukushima Daiichi.

: Debris retrieval: Cell transfer of debris■ Score table for item 7-2[4 points] Cannot be determined directly and there are issues
with introduction[3 points] Cannot be determined directly and can expect
introduction to be feasible[2 points] Can be determined directly, but there are issues withintroduction[1 point] Can be determined directly and can expect
introduction to be feasible

Important monitoring items

No.233■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is
unknown[3 points] Countermeasures exist, but throughput decreases
significantly due to suspension of task
[2 points] Countermeasures exist, but throughput decreases due
to workload limitations[1 point] No impact on throughput, or when 7-1 is 1 point

Weighted evaluation of important monitoring items
Item 7-4

Item 3 (excerpt
Item 1from error

Item 4Item 5Item 7-1

Item 7-2

Item 7-3

extraction table)

Fuel debris

Presence ormechanism

collection

absence offunctioninterfering objects
cannot be verified

due to dripping

Delay inascertaining
the presenceor absence ofinterfering
objects

water, anddue to error
handling- Direct determination iscauses)
The safety

Daiichi-2 PCV shows the effectivenesspossible if 3D scans ormeasuresof the method that confirms theother dimensional

for each

objectspresence or absence of interfering

acquisitions are madefeature ofunaffected by

objects on the task route in advance- Detailed investigationeach method

dripping waterusing dedicated equipment, andinside the Fukushima

shown inapplication of a similar method is

Daiichi-2 PCV shows

assumed.

the application of laser- Since fuel debris will be transferredscanning technology to

because noduring this task, it is assumed thatobtain maintenanceelement that

additional safety measures will be

information on

greatlyrequired, and 2 points will be given.

interfering objects.

restrict work

- Investigation inside the Fukushima(a) Presence ofinterfering

Dripping
water

safety on the

Effects on accurate andprompt on-site response
by workers

3transfer routetakes time

3

3

3

3

(Indirect[Items 4/5]

Safetyverification ofthroughput
Presence or absence ofcountermeasures for disturbing
functions

Point ofrepresentation

avoid work
delaysCell transfer

3

requirements to

Individual

Work delay factor

Indirectcauses of
error

Point

responsible

Detection
Direct causesof error

Impact on

Point

the target isApplicable function

function that
Targetequipment(Evaluation
Results)

The

for

Saku
-A-

Item 6Point

Risk
assessment
table
analysis
numberItem 2

1

Item 7-1 are
1given 1 point

These countermeasures are beingarestudied for each feature of each method

extracted.

of debris retrieval project.
Fuel debris

Presence orcollection

absence offunctioninterfering objects
cannot be

4

Cell transfer
mechanism[Items 4/5](a) Presence ofinterfering
objects
unaffected bydetermined due tohigh background

Noise

noise

3

SafetySaku-A-Delay inascertaining
the presenceor absence ofinterfering
objects

Same as above

1

Same as above

1

Same asabove

noise, andverification ofsafety on thetransfer routetakes time

©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-3: Risk assessment table for operational equipment (Detailed version) (45/59)

No.234■ Risk assessment table

Model ID
Process

Ko-3

Work

Sa-6

: Debris retrieval: Cell transfer ofdebris■ Score table for item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still
under development[2 points] Countermeasures exist, but there are no
track records of application at the Fukushima Daiichi[1 point] Countermeasures exist, and have been
applied at the Fukushima Daiichi.

■ Score table for item 7-2[4 points] Cannot be determined directly and there are issues
with introduction[3 points] Cannot be determined directly and can expect
introduction to be feasible[2 points] Can be determined directly, but there are issues withintroduction[1 point] Can be determined directly and can expect
introduction to be feasible

Important monitoring items■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is
unknown[3 points] Countermeasures exist, but throughput decreases
significantly due to suspension of task
[2 points] Countermeasures exist, but throughput decreases due
to workload limitations[1 point] No impact on throughput, or when 7-1 is 1 point

Weighted evaluation of important monitoring items

Item 3(excerpt
Item 2from error

Item 7-4
Item 4Item 5Item 6Item 7-1

Item 7-2

Item 7-3(Evaluation

extraction

Results)

table)

causescauses ofrequirements toof errorerror

avoid work delays

Presence or absence ofcountermeasures for disturbing
functions

Effects on accurate andprompt on-site response bythroughput due toerror handlingworkers(Indirect causes)

Point ofrepresentation

factor

Detection

Point

responsible

Work delay

IndirectPoint

equipment

target is

Impact on
DirectPoint

Targetthat theIndividual

The function

Applicable
functionRisk
assessment
table
analysis
numberItem 1

2

4

4

4

for
Fuel debris[Item 4]

- Heavy machinery with- Can be determined directly

Although the specificcollection(a) Time to reachunderwater specifications

by acquiring the actual

safety measures

function

destination

exists in general worktransfer timeshown in Item 7-1

technology and water currents- Can be executed throughhave not been

can be resisted.

control, and there are no

studied in depth in- Since fuel debris will be

issues with introduction

Due towater flow,
1

Cell transfer
mechanismit takes time
to move theSlowtransfer
speed

2

Water flow

Work

Saku
-B-

transferred during this task, it

1

the debris retrieval
1

project, in air

is assumed that additionaltransfer is expectedsafety measures will be

to be applied, and 1

required, and 2 points will bepoint is given.

inner
container
given. It is necessary to study
these measures for eachfeature of each method
When using a Price current
meter, it is possible to directly[Item 5]flow on the transfer
route

determine the flow velocity,2Work(b) Velocity of water

Same as above2

but there are problems

1

Same as above

because it requires assessing
the radiation resistance of theflow meter in a high-doseradiation environment©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-3: Risk assessment table for operational equipment (Detailed version) (46/59)

No.235■ Risk assessment table■ Score table for item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still
under development[2 points] Countermeasures exist, but there are no
track records of application at the Fukushima Daiichi[1 point] Countermeasures exist, and have been
applied at the Fukushima Daiichi.

Model ID
Process

Ko-3: Debris retrieval

Work

Sa-6

: Cell transfer ofdebris

Items
1

Item 5causes ofcauses of

error

error

for

2

to avoid work
delays

Impact on
Effects on accurate and prompt
on-site response by workers

Fuel debris

Transfer takes

DelayedInner[Item 4]

- In general, parts with low radiation- When using a dosimeter, acollection

time due todeterminati

container(a) Degree ofresistance, such as those used todirect determination can befunction

evaluation of

on ofradiationeffects ontransfer spent fuel, are designed tomade by setting the thresholdthe impact on

effects onequipment

be kept away from the radiationdose based on the cumulative

the equipment

radiation

against hot
spots

container thathas become a1source.

1exposure dose of the- In the debris retrieval project, a

operational equipment.

(radiation

method has also been proposed in- Dosimeters have been

resistance)

which cranes are used to transfer

introduced in the on-site

electric drive components without

validation test of the project ofgetting close to the inner container.

investigation inside the PCV.

hot spot[Item 5]- When using a dosimeter, it is(b) Location ofnecessary to establish a

hot spots on

measurement method that is

route

1

Work

the transfer

Because Item
7-1 is 1 point

1

3

1

Same as above

3

3

addressing
errors (indirectcauses)mechanism

for the inner

1

throughput by
Presence or absence ofcountermeasures for disturbing
functions

Cell transfer

Work

Saku
-B-

requirements

Item 7-4(Evaluation
Results)

Point ofrepresentation

Indirect

Item 7-3

Individual

responsible

factorDirectDetection

Item 7-2

Pointthat target is

Work delay

Item 7-1

Point

equipmentfunctions

Item 6

Applicable function

The

Target■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is unknown[3 points] Countermeasures exist, but throughput decreases significantly
due to suspension of task
[2 points] Countermeasures exist, but throughput decreases due toworkload limitations[1 point] No impact on throughput, or when 7-1 is 1 point

Weighted evaluation of important monitoring items

Point

Risk
assessment
table
analysis
numberItems
2

Important monitoring items
Item 3(Extracted
from the error
Item 4extraction
table)■ Score table for item 7-2[4 points] Cannot be determined directly and there areissues with introduction[3 points] Cannot be determined directly and can expect
introduction to be feasible[2 points] Can be determined directly, but there are issues
with introduction[1 point] Can be determined directly and can expect
introduction to be feasible

not affected by the surrounding
Same as above3

background.
- Development of technology toidentify hot spots in a high-doseradiation environment isrequired.

©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-3: Risk assessment table for operational equipment (Detailed version) (47/59)■ Risk assessment table

No.236■ Score table for item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still underdevelopment[2 points] Countermeasures exist, but there are no trackrecords of application at the Fukushima Daiichi[1 point] Countermeasures exist, and have been applied at
the Fukushima Daiichi.

Model ID
Process

Ko-3: Debris retrieval

Work

Sa-6

: Cell transfer of debris

Item 1is responsible

factorfor

SakuB-

Detection

causes ofcauses ofrequirements to avoid

error

error

work delays

Cell transfer

Fuel debris

CannotDelay in

[Items 4/5]

mechanism

collection

detect theascertaining(a) Transfer routefunctiontransfer

the transfer

route due to

route

3

3

Item 7-3

Item 7-4(Evaluation
Results)

Impact on
Presence or absence of countermeasures for disturbing
functions

Effects on accurate andprompt on-sitethroughput due

The detailed investigation inside the Fukushima Daiichi-23Underwater laser

to error handling(Indirect causes)

response by workers

1

Point ofrepresentationequipment

Indirect

Item 7-2

Point

Work delay

DirectItem 7-1

Pointthat the target

Item 6

Point

TargetItem 5

Individual

The function

Weighted evaluation of important monitoring items

Applicable function WorkRisk
assessment
table analysis
numberItem 2

Important monitoring items
Item 3(excerpt
from error
Item 4extraction
table)■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is unknown[3 points] Countermeasures exist, but throughput decreases significantly due tosuspension of task
[2 points] Countermeasures exist, but throughput decreases due to workload
limitations[1 point] No impact on throughput, or when 7-1 is 1 point■ Score table for item 7-2[4 points] Cannot be determined directly and there are issues
with introduction[3 points] Cannot be determined directly and can expect
introduction to be feasible[2 points] Can be determined directly, but there are issues withintroduction[1 point] Can be determined directly and can expect
introduction to be feasible

99There is no

PCV is currently developing a technology that enables

scanning technology

impact on

detection unaffected

equipment to be moved even in the PCV environment byexists in generalthroughput withby soaring sedimentobtaining information on the maintenance of interfering

industry, and the air

the introduction

sediment

Soaring

objects in advance through laser scanning. Although thisdose rate in water isof thesoaringsediment

technology is based on the assumption that the scanner

low, so applicability istechnology

duringwill be used in air, it can be adapted by retrofitting thehigh.

shown in Item 7-transfer,scanner with underwater specifications.

1

and transfer
Cellmechanismradiation,

the current

Innerverification

location ofcontainerof current

the innerradiation

locationcontainer

takes time
Due toDelay incollection

soaring dust

ascertaining

functionin cell (R),the current

verification

location of

5of current

the inner

locationcontainer[Items 4/5](a) The current
location of the innercontainer unaffected

3

3

3

Same as above

3

Same as above

1

Same as above

9

9

Same as above

3

Same as above

1

Same as above

9

9

Work

transfer Fuel debris

mechanismB-ascertaining

function
4

Cell

Saku-

container

Work

B-

Delay incollection

Work

Saku-

takes time
Due to innertransfer Fuel debrisSame as above

3

Same as above

1

Same as above

9

9

by the inner container
radiation[Items 4/5]
Dust(a) Transfer route
detection unaffectedby dusttakes time
Celltransfer Fuel debris

mechanism
SakuB-

6

Due to high

Delay incollection

backgroundascertaining

functionnoise,

the current

verification

location ofof current

the inner

locationcontainer[Items 4/5]
Noise(a) Current location of
the inner container
unaffected by noise

takes time

©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-3: Risk assessment table for operational equipment (Detailed version) (48/59)

No.237■ Risk assessment table

Model ID
Process
Work

Ko-3
Sa-7

: Debris retrieval: Transfer ofdebris ①■ Score table for item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still
under development[2 points] Countermeasures exist, but there are no
track records of application at the Fukushima Daiichi[1 point] Countermeasures exist, and have been
applied at the Fukushima Daiichi.

■ Score table for item 7-2[4 points] Cannot be determined directly and there are issues
with introduction[3 points] Cannot be determined directly and can expect
introduction to be feasible[2 points] Can be determined directly, but there are issues withintroduction[1 point] Can be determined directly and can expect
introduction to be feasible

Important monitoring items
Item 1

responsible for

error

throughput

due to error
and prompt on-site
handling

response by workers

Fuel debris canister

Due to inner

Delay in

[Items 4/5]

Monitoring for interference- The more parallelcauses)Addressing

transfer

sealing function

container radiation,

ascertaining the(a) Detection

between parallel operations

work there are, theItem 7-1 ismechanismverification of thepresence orof flow line

in an unmanned

more control

assumed to①

presence of flow line absence of flowinterference

environment andparameters there are,have nointerference on theline interference

unaffected byoperations based on suchmaking it impossible

impact ontransfer route takeswith other work

Inner

the innermonitoring is widespread infor workers to makecontainer

container

radiation

radiation

time

2

6

6

6

(Indirect

Intra-cell

16Impact on

Effects on accurate

Presence or absence ofcountermeasures for
disturbing functions

Item 7-4(Evaluation
Results)

Point of representation

causes oferror

Item 7-3

Individual

Work delay factor

Detectionrequirements
to avoid work
delaysItem 7-2

Point

the target isDirect causes of

Item 7-1

Work

Saku
-B-

Indirect

The function that

Item 6Point

equipment

Item 5

Applicable function

TargetItem 4Weighted evaluation of important monitoring items

Point

Risk
assessment
table
analysis
numberItem 2Item 3 (excerpt fromerror extraction
table)■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is
unknown[3 points] Countermeasures exist, but throughput decreases
significantly due to suspension of task
[2 points] Countermeasures exist, but throughput decreases due
to workload limitations[1 point] No impact on throughput, or when 7-1 is 1 point

general industry (e.g.,3

direct decisions.

manufacturing plants), so it- Mechanicalis assumed that thismonitoring needs to betechnology will be

specially designed

introduced.

according to thethroughput.
1

characteristics of thework line.

2

Fuel debris canister

Due to soaring dust

Delay in

[Items 4/5]

transfer

sealing functionin cell (R),ascertaining the(a) Detection

mechanismverification of flowpresence orof flow line①

line interference on

absence of flow

the transfer routeline interference

takes timewith other work

Dust in cell interference(R)

unaffected by

2

Work

Saku
-B-

Intra-cell

Same as above

3

Same as above

1

Same as
above

dust

©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-3: Risk assessment table for operational equipment (Detailed version) (49/59)

No.238■ Risk assessment table■ Score table for item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still
under development[2 points] Countermeasures exist, but there are no
track records of application at the Fukushima Daiichi[1 point] Countermeasures exist, and have been
applied at the Fukushima Daiichi.

■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is unknown[3 points] Countermeasures exist, but throughput decreases significantly
due to suspension of task
[2 points] Countermeasures exist, but throughput decreases due toworkload limitations[1 point] No impact on throughput, or when 7-1 is 1 point■ Score table for item 7-2[4 points] Cannot be determined directly and there are issues
with introduction[3 points] Cannot be determined directly and can expect
introduction to be feasible[2 points] Can be determined directly, but there are issues withintroduction[1 point] Can be determined directly and can expect
introduction to be feasible

Model ID
ProcessWork

Sa-7: Debris retrieval: Transfer ofdebris ①
Important monitoring items
Item 3(excerpt fromerror
Item 4extraction
table)

Item 1

Item 2

Targetequipment

The function thatthe target is
responsible forWork delay
factorDirectcauses oferror

Item 5Item 6

Indirectcausesof error

Detectionrequirements toavoid work
delaysItem 7-1

Item 7-2

Item 7-3

Cell (Y)Static boundary

It takes time

Delay in

[Item 4]

- Even if the dust

Direct determination is

Addressing item 7-1

functionto assess theascertaini(a) Dust

concentration in cell (Y)possible by setting thelimits the workload

concentration inincreases temporarily, thedust concentration(temporarycell (Y)concentration will decrease

threshold.

suspension of work)

Item 7-4(Evaluation
Results)increasecell (R)environmentalinmaintenancecontaminaof cell (Y)tion in cell

1

due to error handling(Indirect causes)

Point ofrepresentation

Dust inthe

Effects on accurate andprompt on-site
response by workers

Point

there is an

Safetycontainer on

Pointwhether

Applicable
functionfrom the innerng

Presence or absence ofcountermeasures for
disturbing functions

Individual

Impact on throughput

impact of dust

Saku
1
-A-

Weighted evaluation of important monitoring items

Point

Risk
assessment
table
analysis
number

Ko-3

2

2

2

2

over time due to ventilation
and air conditioning

12

equipment.
- The current PCV also

responds by temporarilysuspending work when dust(Y)concentrations rise.
[Item 5](b) Dust

cell (R)1

Safetyconcentration inSame as above

1

Same as above

2

Same as above©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-3: Risk assessment table for operational equipment (Detailed version) (50/59)

No.239■ Risk assessment table■ Score table for item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still underdevelopment[2 points] Countermeasures exist, but there are no trackrecords of application at the Fukushima Daiichi[1 point] Countermeasures exist, and have been applied at the
Fukushima Daiichi.

Model ID
Process

Ko-3: Debris retrieval

Work

Sa-7

: Transfer of debris ①

Item 1

Effects on accurate andprompt on-site response byworkers

Item 7-4(Evaluation
Results)

Impact on
throughput byaddressing
errors (indirectcauses)Point ofrepresentation

Presence or absence ofcountermeasures for disturbing
functions

Item 7-3

Individual

Detectionrequirements toavoid work delays

Item 7-2

2

work)

2

2

2

Same as above

2

2

Point

Static boundaryfunctionIndirectcauses oferror

Item 7-1

Point

Cell (Y)Direct causesof error

Item 6

It takes time to Delay in[Item 4]

- Even if the concentration of

Direct determination is

Addressing item

assess theascertaining(a) Hydrogenhydrogen or oxygen in the cellpossible by setting the

7-1 limits theimpact of

the effect ofconcentration/or(Y) rises temporarily, thehydrogen concentration or

workloadhydrogen fromincreased

oxygenconcentration will decrease

oxygen concentration(temporary

the innerhydrogenconcentration in cellover time due to ventilation, air

thresholds.

container on

concentration

thein cell (Y)Hydrogenfrom innercontainer(Y)

1

Safety2

The function
Work delaythat the target isfactorresponsible for

Item 5

Applicable function

Saku
-A-

Targetequipment■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is unknown[3 points] Countermeasures exist, but throughput decreases significantly
due to suspension of task
[2 points] Countermeasures exist, but throughput decreases due toworkload limitations[1 point] No impact on throughput, or when 7-1 is 1 point

Weighted evaluation of important monitoring items

Point

Risk
assessment
table
analysis
numberItem 2

Important monitoring items
Item 3(excerpt fromerror
Item 4extraction
table)■ Score table for item 7-2[4 points] Cannot be determined directly and there are issues
with introduction[3 points] Cannot be determined directly and can expect
introduction to be feasible[2 points] Can be determined directly, but there are issues withintroduction[1 point] Can be determined directly and can expect
introduction to be feasible

conditioning equipment, and1nitrogen injection equipment.

environmental- The current PCV is also

maintenanceimplementing safety measuresof cell (Y)with nitrogen injection.
Same as above[Item 5]

- Direct determination is(b) Amount ofpossible by using a hydrogenhydrogen generated

concentration meter andin the innercomparing with the threshold.
1

Safetycontainer

suspension of2- Since the inner container
has a high radiation dose,
there are issues such asproviding radiation resistancewhen the instrument isbrought into close proximity.

©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-3: Risk assessment table for operational equipment (Detailed version) (51/59)■ Risk assessment table■ Score table for item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still underdevelopment[2 points] Countermeasures exist, but there are no trackrecords of application at the Fukushima Daiichi[1 point] Countermeasures exist, and have been applied at
the Fukushima Daiichi.

Model ID
Process

Ko-3: Debris retrieval

Work

Sa-7

:
Transferdebris ①

Item 1of

Item 2

Important monitoring items
Item 3 (excerpt
from error
Item 4extraction
table)

Weighted evaluation of important monitoring items
Item 5Item 6Item 7-1

Item 7-2

Item 7-3

Item 7-4(Evaluation
Results)

error

error

requirements
to avoid work

delaysPresence or absence ofcountermeasures for disturbing
functionserror handling

prompt on-site(Indirect causes)

response by

Delay in

[Item 4]

- Since the radiation source (inner- Direct

Addressing item 7-

assess theascertaining

Air dose ratecontainer) is small compared to thedetermination is

1 limits theof cell (Y)spatial scale of cell (Y), it is thoughtpossible by using

workloadthat there will be no significant

a dosimeter and(temporary

radiation on

increase inthespatial dose

environmental

rate in cellmaintenance

(Y)

Inner
2

containerWork

there is anradiation

2

2

2

2

workers

It takes time tocontainer

Point of representation

causes ofthroughput due toaccurate andIndividual

causes of

Detection

Effects on

Point

Indirect

Point

Shielding
function of
the cellWork delay
factorDirectApplicable function

The functionthat theTargettarget isequipment
responsiblefor

impact of inner whether

3■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is unknown[3 points] Countermeasures exist, but throughput decreases significantly
due to suspension of task
[2 points] Countermeasures exist, but throughput decreases due toworkload limitations[1 point] No impact on throughput, or when 7-1 is 1 point

Impact on

Cell (Y)Saku-B-■ Score table for item 7-2[4 points] Cannot be determined directly and there are issues
with introduction[3 points] Cannot be determined directly and can expect
introduction to be feasible[2 points] Can be determined directly, but there are issues withintroduction[1 point] Can be determined directly and can expect
introduction to be feasible

Point

Risk
assessment
table
analysis
number

No.240impact.

1- If there is a problem with cellcomparing withsuspension of2

the thresholdwork)

operation, measures such as
temporarily returning the innerof cell (Y)container to cell (R) can beconsidered.
[Item 5]

- Directdose rate of
inner

2

Work

(b) Surface

determination isSame as above1

possible by using

2

Same as above

a dosimetercontainer©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-3: Risk assessment table for operational equipment (Detailed version) (52/59)

No.241■ Risk assessment table■ Score table for item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still
under development[2 points] Countermeasures exist, but there are no
track records of application at the Fukushima Daiichi[1 point] Countermeasures exist, and have been
applied at the Fukushima Daiichi.

Model ID
Process

Ko-3

Work

Sa-7

: Debris retrieval: Transfer ofdebris ①
Important monitoring items

Item 1

Impact on
Effects on accurate andprompt on-site response
by workers

throughput due toerror handling

Delay in

[Items 4/5]

Since cell (R) is

Since cell (R) is a newly

Addressing Item

ascertaining(a) Transfer

a newly installed

installed structure, the

7-1 is assumed to

Soaringsoaring dust in cellthe transfer

dust inroute

2

detection
cell (R)structure, the1transfer route can betransfer routedefined in design stage,

unaffected bycan be defined inand direct determination

soaring dust

design stage.

is possible.

Due to inner container[Items 4/5]

- Direct determination

radiation, verification(a) Current

can be made from theof the current location

location

ITV and the amount ofdetection ofwheel rotation of the

Ascertaining
the current
location of theinner container

the inner

Inner
container container
radiation
unaffected bysoaring dust

2

Work

takes time

Item 7-4(Evaluation
Results)

2

2

2

2

(Indirect causes)

transfer route due toof the inner container

5

Item 7-3

Point ofrepresentation

mechanism ①

Presence orabsence ofcountermeasuresfor disturbing
functions

Item 7-2

Individualtransfer

Fuel debris
canistersealingfunction

Item 7-1

Cannot detect the

time

Sak
u-B-

Detection
Indirectrequirements
causes of
to avoid work
error
delays(R), and transfer takes route

Intra-cell

Item 6Point

mechanism ①

Fuel debris
canistersealingfunction

Direct causesof error

Item 5Work

4The functionthat thetarget is
Work delay factor
responsiblefor

Item 4Point

transfer

Item 3 (excerpt fromerror extraction table)

Applicable function

Intra-cell

Item 2

Weighted evaluation of important monitoring items

Point

Risk
assessment
table
analysisTargetnumberequipment

Sak
u-B-

■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is unknown[3 points] Countermeasures exist, but throughput decreases significantly
due to suspension of task
[2 points] Countermeasures exist, but throughput decreases due toworkload limitations[1 point] No impact on throughput, or when 7-1 is 1 point■ Score table for item 7-2[4 points] Cannot be determined directly and there are issues
with introduction[3 points] Cannot be determined directly and can expect
introduction to be feasible[2 points] Can be determined directly, but there are issues withintroduction[1 point] Can be determined directly and can expect
introduction to be feasible

1

have no impact
on throughput.

transfer mechanism inSame as above1

the cell. When the

1

Same as above

accuracy of detection
requirements is high,measures such as use oflimiter switches also
exist.

©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-3: Risk assessment table for operational equipment (Detailed version) (53/59)■ Risk assessment table■ Score table for item 7-1[4 points] No countermeasures have been
determined[3 points] Countermeasures exist, but they
are still under development[2 points] Countermeasures exist, but there
are no track records of application at the
Fukushima Daiichi[1 point] Countermeasures exist, and havebeen applied at the Fukushima Daiichi.

Model ID
Process
Work

Ko-3
Sa-8

: Debris retrieval: Sealed collection ofdebrisImportant monitoring items
Item 3(excerpt from
Item 1
Item 2error
Item 4extraction
table)■ Score table for item 7-2[4 points] Cannot be determined directly and there are issues
with introduction[3 points] Cannot be determined directly and can expect
introduction to be feasible[2 points] Can be determined directly, but there are issues withintroduction[1 point] Can be determined directly and can expect
introduction to be feasible■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is
unknown[3 points] Countermeasures exist, but throughput decreases
significantly due to suspension of task
[2 points] Countermeasures exist, but throughput decreases due
to workload limitations[1 point] No impact on throughput, or when 7-1 is 1 point

Weighted evaluation of important monitoring items

Item 5Item 6Item 7-1

Item 7-2

Due to inner

Delay in

[Item 4]

If a foreign object is- Can be determined directly

Addressing

collection

canistercontainer

ascertaini(a) Time toprotruding from the inner

by obtaining actual task

Item 7-1 limits

radiation, it

ng theverify whether

container, it is expected tohours

the workload.

be returned to cell (R), and- Can be executed in the

to avoid work
delaysPoint

Fuel debris

requirements

Effects on accurate andto error

prompt on-site response byhandling

workers

Point of representation

throughput due

SealedIndirectcauses of
error

4

12

12

12

Impact on

Work delay
factorTargetequipment

Detection
Directcauses oferror

Individual

Point

Applicable function

Presence or absence ofcountermeasures for
disturbing functions

Item 7-4(Evaluation
Results)

Item 7-3

The functionthat thetarget is
responsible
for

Point

Risk
assessment
table
analysis
number

No.242(Indirect
causes)mechanism sealing
function1

takes time toverify whether
the contentsorabsence

Contents of
innercontainer

the contents

2

are protruding

Work

Sak
u-B-

presence1

there will be measures suchcontrol room, and there arefrom the inneras replacing it with anotherno issues with introduction

inner container.

ofcontainer orare protruding

contents

notfrom the innerprotruding[Item 5]

Although sensory

container orfrom the(b) Presence

determination (= direct

not

inner

or absence ofdetermination) may becontainer

contents

possible with camera

the innercontainer

2

Work

protruding from

Same as above

3

images, there are cases inwhich wrong determinations

2

2

Same

as

above

may be made depending on
the conditions forphotography, and certainty
cannot be guaranteed.

©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-3: Risk assessment table for operational equipment (Detailed version) (54/59)■ Risk assessment table■ Score table for item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still underdevelopment[2 points] Countermeasures exist, but there are no trackrecords of application at the Fukushima Daiichi[1 point] Countermeasures exist, and have been applied at
the Fukushima Daiichi.

Model ID
Process
Work

Ko-3
Sa-8

: Debris retrieval: Sealed collection of debris
Important monitoring items■ Score table for item 7-2[4 points] Cannot be determined directly and there are issues withintroduction[3 points] Cannot be determined directly and can expect introduction
to be feasible[2 points] Can be determined directly, but there are issues withintroduction[1 point] Can be determined directly and can expect introduction to
be feasible

No.243■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is unknown[3 points] Countermeasures exist, but throughput decreases significantly due to suspensionof task[2 points] Countermeasures exist, but throughput decreases due to workload limitations[1 point] No impact on throughput, or when 7-1 is 1 point

Weighted evaluation of important monitoring items

Item 3 (excerpt
Items
1from error

Item 7-4
Item 4Item 5Item 6Item 7-1(Evaluation

Detection requirementsof errorerror

to avoid work delays

Effects on accurate and prompt on-site
response by workers

Fuel debris Due to inner

Delay inDamage[Item 4]

If the inner container is- Can be determined directly by obtaining

collection

canistercontainer

ascertaining

during(a) Time to verify

damaged, it is expected to be

actual task hours

mechanism

sealingradiation, it

the presencetransfer ofwhether the innerreturned to cell (R), and there will 1- Can be executed in the control room,takes time toor absence of

the innercontainer is damaged

be measures such as replacing it

and there are no issues with introduction

verify whether

damage to thecontainer

or notwith another inner container.

the inner

inner container

function

2

Work

SealedAlthough sensory determination (= directcontainer is(b) Presence ordetermination) may be possible withdamaged or notabsence of damage tothe inner container

2

Work

[Item 5]

Impact on
throughput byaddressing errors(indirect causes)

Point ofrepresentation

cause cause of2

workload.

4

12

2

Same as above

1
2

12

2

6

6

6

Point

DirectPointtarget is

Indirect
Work delay
factorPointthat thePresence or absence ofcountermeasures for disturbing
functionsIndividualfunctionTargetComponents

e for

2

Item 7-3

Results)

responsibl

Saku
-B-

Item 7-2

extraction table)
The

Applicable function

Risk
assessment
table
analysis
numberItems
2

Addressing Item 71 limits thecamera images, there are cases in which
Same as above

3

wrong determinations may be madedepending on the conditions forphotography, and certainty cannot be

3

Fuel debris Dust (debris

Slow foreign[Items 4/5]

Although the method of removing

guaranteed.
- Can be determined directly by obtaining

There is no impact

collection

canisterpowder) frommatter (debris

Fuel(a) Removal time offoreign matter varies depending

actual task hours

on throughput if amechanism

sealing

the inner

powder)debrisforeign matter (debris

on the mode of dust adhesion to- Can be executed in the control room,

foreign matterfunctioncontainer

removal speed

powderpowder) caught in thethe container (electrostatic force

and there are no issues with introduction

inside thetransfer container

adheres to the

2

Work

Saku
-B-

Sealedlid and maintransfer

droplets), it is assumed that there

body of thecontainer

are no major technologicaltransfer
container, andremoval takes
time

1

problems with the removal itself.
Same as above[Items 4/5]

determination) may be possible with2Work

matter (debris powder)container

established

Although sensory determination (= direct(b) Amount of foreign

adhering to the transfer

removal method is
1

or surface tension due tocamera images, there are cases in which

3

wrong determinations may be made1

Same as above

depending on the conditions forphotography, and certainty cannot be
guaranteed.

©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-3: Risk assessment table for operational equipment (Detailed version) (55/59)■ Risk assessment table

No.244■ Score table for item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still
under development[2 points] Countermeasures exist, but there are no
track records of application at the Fukushima Daiichi[1 point] Countermeasures exist, and have been
applied at the Fukushima Daiichi.

■ Score table for item 7-2[4 points] Cannot be determined directly and there are issues
with introduction[3 points] Cannot be determined directly and can expect
introduction to be feasible[2 points] Can be determined directly, but there are issues withintroduction[1 point] Can be determined directly and can expect
introduction to be feasible■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is unknown[3 points] Countermeasures exist, but throughput decreases significantly
due to suspension of task
[2 points] Countermeasures exist, but throughput decreases due toworkload limitations[1 point] No impact on throughput, or when 7-1 is 1 point

Model ID
Process

Ko-3: Debris retrieval

Work

Sa-8

: Sealed collection ofdebrisImportant monitoring items

Item 1

Item 4Weighted evaluation of important monitoring items
Item 5Item 6Item 7-1

causes of

error

error

for

Fuel debris

Due to noisecollection

canistercaused by themechanism sealing

inner containercollection into the innerradiation,

containerfunctioncollection into
a sealed[Item 4]Inner
container
radiation

container affects the accuracyof equipment operation, this3

error cannot be ignored, but
in the debris retrieval project,1error handling(Indirect causes)- Can be determined

Done by taking

directly by obtaining

measures in line

actual task hours

with the- Can be executed incharacteristics ofthe control room, and1each method

4

4

4

shown in Item 7-1

with introduction

high-dose radiationtime

Effects on accurate
and prompt on-site
response by workers

there are no issues

debris collection methods in acanister takes

3

throughput due to

If the radiation from the inner(a) Time to complete

Work

Saku
4
-B-

Slow
collection
speed

SealedImpact on

Point of representation

causes of

Detection requirements
to avoid work delays

Presence or absence ofcountermeasures for
disturbing functions

Item 7-4(Evaluation
Results)

Individual

responsible

Indirect

Item 7-3

Pointtarget is

DirectWork delay
factorItem 7-2

Pointthat theTargetequipment

Applicable function

The function

Point

Risk
assessment
table
analysis
numberItem 2Item 3 (excerpt
from error
extraction
table)

environment in line with eachmethod are being studied.
[Item 5]

- Direct determination(b) Surface dose rate ofis possible by using a2Work

inner container

Same as above

1

dosimeter

2

Same as above©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-3: Risk assessment table for operational equipment (Detailed version) (56/59)■ Risk assessment table

No.245■ Score table for item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still
under development[2 points] Countermeasures exist, but there are no
track records of application at the Fukushima Daiichi[1 point] Countermeasures exist, and have been
applied at the Fukushima Daiichi.

Model ID
Process

Ko-3: Debris retrieval

Work

Sa-9

:
Transferdebris ②■ Score table for item 7-2[4 points] Cannot be determined directly and there are issues
with introduction[3 points] Cannot be determined directly and can expect
introduction to be feasible[2 points] Can be determined directly, but there are issues withintroduction[1 point] Can be determined directly and can expect
introduction to be feasibleofImportant monitoring items

Item 1

Indirectcauses oferror

Detectionrequirements toavoid work
delays

It takes time to assess

Delay in ascertaining[Item 4]the impact of airborne

whether there is an(a) Dust

dust in cell (Y) on theincrease inconcentration inenvironmental

contamination in cell

cell (G)Item 7-1

Presence or absence ofcountermeasures for
disturbing functions

increases temporarily, the1and prompt on-site
response bythroughput due toerror handling(Indirect causes)

2

2

2

2

workers

concentration will
Dust in cell(Y)

Item 7-4(Evaluation
Results)

Impact on

concentration in cell (G)Safety1

Item 7-3

Effects on accurate- Even if the dust

maintenance in cell (G) (G)
Saku
-A-

Item 7-2

Point ofrepresentation

Item 6

Individual

Direct causes of error

Item 5

Point

Staticboundaryfunction

Work delay factor

Item 4

Point

Cell (G)The functionthat thetarget is
responsiblefor

Item 3 (excerpt fromerror extraction table)

Point

Targetequipment

Item 2

Weighted evaluation of important monitoring items

Applicable function

Risk
assessment
table
analysis
number■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is unknown[3 points] Countermeasures exist, but throughput decreases significantly
due to suspension of task
[2 points] Countermeasures exist, but throughput decreases due toworkload limitations[1 point] No impact on throughput, or when 7-1 is 1 point

Addressing item 7-1

determination islimits the workload

possible by setting(temporary

the dust

suspension of work)

concentration

decrease over time due toventilation and air

Directthreshold.
1

2

conditioning equipment.
- The current PCV also
responds by temporarilysuspending work when
dust concentrations rise.
[Item 5]concentration in

1

Safety(a) Dust

Same as above

1

Same as above

2

Same as above

cell (Y)©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-3: Risk assessment table for operational equipment (Detailed version) (57/59)■ Risk assessment table
Model ID
Process

Ko-3: Debris retrieval

Work

Sa-9

: Transfer of debris②■ Score table for item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still underdevelopment[2 points] Countermeasures exist, but there are no trackrecords of application at the Fukushima Daiichi[1 point] Countermeasures exist, and have been appliedat the Fukushima Daiichi.

■ Score table for item 7-2[4 points] Cannot be determined directly and there are issues withintroduction[3 points] Cannot be determined directly and can expect introduction
to be feasible[2 points] Can be determined directly, but there are issues withintroduction[1 point] Can be determined directly and can expect introduction to
be feasible

Important monitoring items
Item 1

Item 3 (excerpt from error
extraction table)

Item 4Item 5Item 6

Direct causes ofIndirect causes ofDetection requirements to

error

error

Item 7-2

Item 7-3

Item 7-4(Evaluation
Results)

capacity due to partial capacity

drainagetransport cask

blockage caused by dust

mechanism

accumulation

drainage Reduced drainage

Contaminated[Item 4]

water from water(a) Flow rate in thedecontamination

systemmigrating

1

and

on

accurate

prompton-sitepossible by comparing

flushing the piping.

with the threshold.

[Item 5]- It is assumed that the amount ofWorkers cannot make(b) Amount, particle size

dust adhering to the surface of thedirect determinations

drainage piping.

distribution, and particle

sealed canister is small, and thatwhen sampling anddensity of dust in thethe frequency of error occurrence is

hot lab analysis areinto piping

Safety1

lower than that of the liquid phaseequipment inside the PCV.

throughput due
to error handling

1

4

4

4

1

4

4

4

(Indirect causes)

Direct determination is1

into contaminated watertransferring liquid flowing

Impact on

response by workers

If there is a significant trend toward
blockage, it can be handled by

Effects

Point

Reducedfunction for

Point

Decontamination

ation water

SafetyDecontamin

avoid work delays

Presence or absence ofcountermeasures for disturbing
functions

Point of representation

responsible for

Individual

the target isApplicable function

A-

2

Item 7-1

The function thatWork delay factor

Saku-■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is unknown[3 points] Countermeasures exist, but throughput decreases significantly due tosuspension of task
[2 points] Countermeasures exist, but throughput decreases due to workload limitations[1 point] No impact on throughput, or when 7-1 is 1 point

Weighted evaluation of important monitoring items

Point

TargetRisk
assessment
equipment
table analysis
numberItem 2

No.2464

required. Because
contaminated water is- Addressed by multiplexing piping

handled, there areas needed. In addition, the effect ofproblems with theshort term functional deterioration

sampling methods.

1

1

Because item 71 is 1 point

Same as aboveor shutdown is extremely small

A-

3

Decontamin

Decontamination

Acceleration of piping

Deterioration ofContaminated(a) Flow rate in theation water

function for

deterioration

pipingwater from water

system + amount ofdrainagetransport cask

(deterioration of

decontamination

leakagemechanism

1

SafetySaku-

Although there is impact on safetyfunctions, the frequency of

Direct determination is1

occurrence is expected to be low.

possible by comparing
with the threshold.

[Item 5]Workers cannot maketo corrosion resulting(b) Amount, particle size

direct determinations

from potential difference

distribution, and particle

when sampling andcaused by dust

density of dust in the

hot lab analysis areaccumulation migratingtransferring liquid flowing

to contaminated water

into piping

drainage piping.

Safetyboundary function) due

11

Because item 71 is 1 point

required. Because
Same as above

4

contaminated water is

1

Same as above

handled, there areproblems with thesampling methods.

©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-3: Risk assessment table for operational equipment (Detailed version) (58/59)

No.247■ Risk assessment table

Model ID
Process

Ko-3 : Debris retrieval

Work

Sa-9

Item 1error

requirements toavoid work delays

Item 7-3

Effects on accurate andImpact on
throughput due toerror handling(Indirect causes)

prompt on-site response

throughput.

2

4

1

Same as above

44[Item 4]

It is assumed that the- Can be determined

Addressing Item 7-

inspection(a) Time tocontaminated water will

directly by obtaining

1 is assumed toContaminatedcompletesplash out so

actual task hours

have no impact onwater from water

decontamination of

decontaminationtransfer container2

inspection

countermeasures such as1- Can be executed in thedividing the cell (G) into

control room, and there

two cells are assumed.

are no issues withintroduction

equipment,[Item 5]

By addressing item 7-1,

inspection

Inspection items

detection requirements

takes time.

(surface dose rate,

can be achieved without

degree ofbeing affected byhermeticity,

contaminated water. Any

concentration ofitem can be directly

and1

by workers

Delay intask

Item 7-4(Evaluation
Results)

Point ofrepresentation

s the

error

Indirect causes ofPresence or absence ofcountermeasures for
disturbing functions

Item 7-2

Individual

contaminate

causes of

Detection

Item 7-1

Work

d water

DirectItem 6Point

The
function
Work delaythat thetarget isfactorresponsible
forFuel debris Dispersion
transferoffunctioncontaminate

Weighted evaluation of important monitoring items

Point

Targetequipment

Item 2

Important monitoring items
Item 3(excerpt
from error
Item 4Item 5extraction
table)

Applicable
function1■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is unknown[3 points] Countermeasures exist, but throughput decreases
significantly due to suspension of task
[2 points] Countermeasures exist, but throughput decreases due toworkload limitations[1 point] No impact on throughput, or when 7-1 is 1 point: Transfer of debris②

Out-of-celltransferverification
mechanism
Saku-B-■ Score table for item 7-2[4 points] Cannot be determined directly and there are issues
with introduction[3 points] Cannot be determined directly and can expect
introduction to be feasible[2 points] Can be determined directly, but there are issues withintroduction[1 point] Can be determined directly and can expect
introduction to be feasible

Point

Risk
assessment
table
analysis
number■ Score table for item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still
under development[2 points] Countermeasures exist, but there are no
track records of application at the Fukushima Daiichi[1 point] Countermeasures exist, and have been
applied at the Fukushima Daiichi.

2

Work

surface

Same as above

2

determined by comparing

contamination)

them with their thresholds,

unaffected by

but remote operation ofcontaminated water

the inspection machineposes a problem when
detecting by unmanned

operation.

©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-3: Risk assessment table for debris retrieval and transfer operation system (Detailed version) (59/59)
No.248■ Risk assessment table■ Score table for item 7-1[4 points] No countermeasures have been determined[3 points] Countermeasures exist, but they are still
under development[2 points] Countermeasures exist, but there are no
track records of application at the Fukushima Daiichi[1 point] Countermeasures exist, and have been
applied at the Fukushima Daiichi.

Model ID

Process

Ko-3

Work

Sa-10

■ Score table for item 7-3[4 points] No countermeasures, and impact on throughput is unknown[3 points] Countermeasures exist, but throughput decreases significantly
due to suspension of task
[2 points] Countermeasures exist, but throughput decreases due toworkload limitations[1 point] No impact on throughput, or when 7-1 is 1 point:
Debrisretrieval: Transfer ofdebrisImportant monitoring items
Item 3(excerpt fromerror
Item 4extraction
table)

Detectionrequirements
to avoid work
delaysItem 7-2

Item 7-3

Item 7-4(Evaluation
Results)

Impact on

Presence or absenceof countermeasuresfor disturbing
functions

Effects on accurate andprompt on-site response byworkers

throughput due toerror handling(indirect causes)

Point ofrepresentation

Indirectcausesof error

Item 7-1

Individual

Work delay
factorDirectcausesof error

Item 6

Point

Targetequipment

The functionthat the target
is responsiblefor

Item 5Point

Item 2

Applicable
function

Item 1

Weighted evaluation of important monitoring items

Point

Risk
assessment
table
analysis
number■ Score table for item 7-2[4 points] Cannot be determined directly and there are issues
with introduction[3 points] Cannot be determined directly and can expect
introduction to be feasible[2 points] Can be determined directly, but there are issues withintroduction[1 point] Can be determined directly and can expect
introduction to be feasible

No environmental changes inside the PCV

No task disturbing©International Research Institute for Nuclear Decommissioning

Appendix 6.2.4.3-4: Correlation between debris retrieval model and risk assessment table

No.249Extraction of important monitoring items

Debris retrieval model
Equipment layout diagram
State diagram at each task forenvironmental changes inside the PCV

(A)
(B)

①

Table of disturbances to safety equipment(Analysis ID: Gairan--XX-YY)(K)[Legend]
XX of Model ID
Analysis ID XX
Analysis ID YY: Arabic numerals: Arabic numerals: Alphabet: input for analysis

Operational equipment risk assessment

Operational equipment model

Daily workflow

Process name (Model ID: KoXX)

Collection andtransfer mode
Equipment
configuration block
diagram①(F)↓ Model IDs are shown on the equipment layout diagram(G)↓ Model IDs are shown on the equipment layout diagram

Other than Cell/Door (Model ID: SagyouXX)

Table of safety functions (Model ID: Kinou-Saku-XX)

(H)

(I)

Table of operational functions (Model ID: Kinou-AnXX)(J)

Table of disturbances to operational equipment (Analysis ID: GairanXX)(C)

Process name

(D)

Work Name••Work detail sheet (analysis ID: alphabet)(D)

a. Objectives(B)(I)(G)(H)(C)

b. Environment(D)f. Preceding task

Safety equipment model

Physical model of the environment inside the PCV

Related to operational function(Analysis ID: Saku-B-XX)

Error analysis
table

(E)

Cell/Door (Model ID: Sagyou-Seru-XX)

Related to safety function (Analysis ID:
Saku-A-XX)

Work Name(D)

Work Name (Model ID: Sa-XX)

Equipment operation mode (yearly debris
processing work) (Model ID: Kichu-XX, SuichuXX)

Risk Assessment
Table

②

(C)

c. Safety

d. Equipmente. Target

g. Work start conditions(K)

The upper left figure "Debris retrieval model" and the upper right figure "Extraction ofimportant monitoring items" have input-output relationships corresponding to (A) through (K).
When (A) to (K) on the model side are changed, the input for the side of important monitoring
item extraction also changes, and the important monitoring items are also modified.
Although (A) to (K) are not direct inputs to the risk assessment table, they are related to theerror analysis table, so when the analysis table is changed, the risk assessment table isupdated via ②.

(G)(H)(I)(J)h. Action group(D)i. Work termination
conditions

Safety equipment
risk assessment

j. Handover to the next task

Action group sheet (Analysis ID:
Roman numerals)

Error extraction
sheet (Analysis
ID: Arabic
numerals)②

k. Others©International Research Institute for Nuclear Decommissioning