Subsidy Project of Decommissioning and Contaminated Water Managementin the FY 2016 Supplementary Budgets

Upgrading of Approach and Systems for Retrievalof Fuel Debris and Internal Structures
Accomplishment Report for FY 2017

April 2018

International Research Institute for Nuclear Decommissioning (IRID)
All Rights Reserved. International Research Institute for Nuclear Decommissioning©International Research Institute for Nuclear Decommissioning

Contents of Achievement Report FY 2017I.

Research Background and PurposesII.

Project Goals

III. Implementation Items and Their Correlations
IV. Schedule (Overall)V.

Project Organization

VI. Implementation Details
(1)
(2)
(3)
(4)

Technical Development related to Confinement Function
Technical Development for Dust Collection/Removal Derived from Fuel Debris
Study on α Nuclide Monitoring System for Fuel Debris Retrieval
Study on Optimization of Ensuring Safety of Methods and Systems©International Research Institute for Nuclear Decommissioning

1

2

I. Research Background and Purposes[Background]
In the project of the last fiscal year, the methods and systems for retrieving fuel debris andreactor internals (hereafter referred to as “fuel debris”) for decommissioning the Fukushima
Daiichi Nuclear Power Station (NPS), were studied. In the results, feasibility issues and risks
were identified [Refer to the attached documents for the project achievements (summary) of
the last fiscal year(FY 2016)].
[Purpose]
To solve identified issues, this project focuses on investigating solutions for the following issues
involving the safety aspects of technologies to improve the methods and systems and conduct
element tests as necessary: “Ensuring Confinement Function”, “Capture and Removal of Dust”,“α Nuclide (a collective name of radioactive nuclides that emit α ray) Monitoring.” By reflecting
results of such technical development and results of reviews from related projects, ways tooptimize (e.g. revisiting and re-evaluating previous term’s review items, comparatively
evaluating the methods and systems, and reviewing the overall scenario related to fuel debris
retrieval) in ensuring safety of the methods and systems in terms of exposure andmaintenance, among other things, are also studied.
©International Research Institute for Nuclear DecommissioningI. Research Background and Purposes (Relations with Project in the Last Fiscal
Year)

3

The project in this fiscal year and the last fiscal year are as shown below.
The components of this project [(1) through (4) below] can be classified into two categories [(i) and (ii)below].
[Project in the last
fiscal year]

Issues Identified
through Reviews[This Project](i) Developing Element Technology for the Feasibility of System Controlling
Emission to Environment(hereafter referred to as “Element Technology Development”)(1) Technical Development related to Confinement Function(2) Technical Development for Dust Collection/Removal Derived from Fuel
Debris(3) Studying α Nuclide Monitoring System for Fuel Debris Retrieval
Issues otherthan (1)through (3)*

Reviewed Methods
and Systems

Study onOptimization

Development results are Reflected(ii) Reviewing Overall Methods and Systems for Fuel
Debris Retrieval(4) Study on Optimization of Ensuring Safety of Methods andSystems** For any other issues related to the methods, work was done together
with the Fundamental Technology PJ to solve them based on thedevelopment plan reviewed during the last term and progress in method
reviews.
©International Research Institute for Nuclear DecommissioningI. Research Background and Purposes (Scope of Element Technology Development)4➢➢

The figure below shows the scope of element technology development planned in this project.
For the study on system optimization, safety-related systems (including facilities for addressing problems in caseof failures) are within the scope of our review. (results of other projects are also reflected, including the criticality
control PJ.)

Liquid System(Overall Image)*: Scope of element technology development
planned in this project

Gas System(Overall Image)*
Boric Acid Solution
Injection Pump

: Scope of element technology development
planned in the Criticality Control PJ

Boric Acid
Solution Tank
[Legends]
Blue: Facility for regular operations
Red: Facility for emergency
operations
Green: Monitoring facility

Injection Pump

Confinement Technology Using
Differential Pressure Control

Water Injection
Tank* Development of PCV maintenance technology
is the scope of a different project

Boric Acid Solution
Supply Pump

Boric Acid
Solution Tank

Soluble Nuclides
Removal Facility

ExhaustPort

Supplementary
Feedwater Tank

Particle
RemovalFacility

Particle
Pretreatment
Removal Filter
Facility

Criticality
Hydrogen Dust
DensitometerMonitor Monitor

Emergency
Buffer Tank
To Water Treatment
Facility
To Water Treatment
Facility

Monitoring
Facility

Exhaust Fan

From Water
Treatment Facility

Supply Pump

Abbreviations for
Monitoring Instruments
L: Water Level Gauge
T: Thermometer
P: Pressure Indicator
F: Flowmeter
n: Neutron Monitor
B: BoronConcentration
R: Radiation
Dosimeter

To Water Treatment
Facility

CoolerExhaust Fan
Particle
Pretreatment
Removal Filter
Facility

Exhaust Port

From Torus Room

Nitrogen Supply Facility

Circulating Pump
Particle
RemovalFacility

Particle
RemovalFacility

Boric Acid
Control
Equipment

Exhaust Fan
Particle
RemovalFilterCoolerBuffer Tank

To Buffer Tank

Torus Room Intake Pump
(For Regular andEmergency Use)

Particle Removal
Facility

D/W Intake Pump
(For Regular andEmergency Use)

S/C Intake Pump
(For Regular andEmergency Use)

Criticality
Hydrogen Dust
DensitometMonitor Monitor
erParticle
RemovalFacility[Terminology]• The terms “gas” and “liquid” are used to indicate a form of fluid being handled (e.g., in system names).
• The terms “gas phase” and “liquid phase” are used to represent separate spaces based on the phasestate (mainly inside the PCV).

Monitoring
Facility

Pretreatment
Facility

In-Leak due to PCV
Negative Pressure

Nitrogen Supply Facility

Pretreatment
Facility

Particle Removal
Facility(HEPA Filter)* This drawing is shown, for illustrative purposes only, as an example of
implementation that satisfies the functional requirements. It is not intended to
identify certain installation positions (in/out of R/B) of the facilities or component
models.

©International Research Institute for Nuclear Decommissioning

5

II. Project Goals
The project focuses on completing the conceptual study of the methods and systems.
Required technologies are developed, comparative evaluation in terms of
exposure/maintainability is conducted, and optimization for ensuring the safety of debris
retrieval to solve issues that involve the safety assurance aspects of technologies for improving
the methods and systems, such as “Ensuring Confinement Function,” “Capture and Removal ofDust,” “α Nuclide (a collective name of radioactive nuclides that emit α ray) Monitoring” isstudied.
Specific objectives for each project item are shown on the following slides.
[Major Project Items(Based on the Application Form of Subsidy Projects)](1) Technical Development related to Confinement Function(i) Technical Development for Ensuring Confinement Function(ii) Technical Development for Dose Reduction*(2) Technical Development for Dust Collection/Removal Derived from Fuel Debris(i) Technical Development for Reducing and Removing Radioactive Materials in Gas Phase System(ii) Technical Development for Reducing and Removing Radioactive Materials in Liquid Phase System(3) Studying α Nuclide Monitoring System for Fuel Debris Retrieval(i) Conceptsual Study and Development Planning of Detection Technologies and Systems for α Nuclides
in the Gas Phase(ii) Conceptsual Study and Development Planning of Detection Technologies and Systems for α Nuclides
in Liquid Phase(4) Study on Optimization of Ensuring Safety of Methods and Systems* Dose reduction is regarded as one of the indicators for method and system optimization, and therefore “(1) (ii) Technical Development for Dose
Reduction” has been integrated reviewed together with the Item (4).
[The corresponding item number is not listed in “IV. Project Items” of this document.]©International Research Institute for Nuclear Decommissioning

6

II. Project Goals(1) Technical Development related to Confinement Function(i) Technical Development for

To set conditions for controlling the differential pressure inside the building and

Ensuring Confinement

PCV.

Function

To confirm

the effectiveness of differential pressure control, ensuring theconfinement function and preventing hydrogen accumulation, fire, andexplosions inside the PCV.
To study measures to improve the sealability of the building/PCV and confirm
their effectiveness.
(Target TRL upon completion: Level 3)(ii) Technical Development for
Dose Reduction

To establish a scenario for dose reduction for the public and workers during thefuel debris retrieval work, or in the case of an accident, and evaluate estimatedexposure dose.
(Target TRL upon completion: Level 3)©International Research Institute for Nuclear Decommissioning

7

II. Project Goals(2) Technical Development for Dust Collection/Removal Derived from Fuel Debris(i) Technical Development for

To study effective dust capture and collection methods as part of the cleaning

Reducing and Removing

function of the gas phase system while taking ensuring safety and waste

Radioactive Materials in Gas

reduction into account.

Phase System(Target TRL upon completion: Level 3)(ii) Technical Development for

To study effective methods for capturing and collecting insoluble and soluble

Reducing and Removing

radioactive materials (α nuclides) as part of the cleaning function of the liquid

Radioactive Materials inphase system while taking ensuring safety and waste reduction into account.

Liquid Phase System(Target TRL upon completion: Level 3)©International Research Institute for Nuclear Decommissioning

8

II. Project Goals(3) Studying α Nuclide Monitoring System for Fuel Debris Retrieval(i) Conceptsual Study and

To study monitoring systems based on the existing technologies for monitoring α

Development Planning of

nuclides in the gas phase.

Detection Technologies andTo identify issues involving the monitoring system for α nuclides in the gas

Systems for α Nuclides in the phase in preparation for fuel debris retrieval, and draw up a future development
Gas Phaseplan.
(Target TRL upon completion: Level 3)(ii) Conceptsual Study and

To study the monitoring system based on the existing technologies forDevelopment Planning ofmonitoring α nuclides in the liquid phase.

Detection Technologies andTo identify issues involving the monitoring system for α nuclides in the liquid

Systems for α Nuclides inphase, in preparation for fuel debris retrieval, and draw up a future development

Liquid Phase

plan.
(Target TRL upon completion: Level 3)©International Research Institute for Nuclear Decommissioning

9

II. Project Goals(4) Study on Optimization of Ensuring Safety of Methods and Systems

To study optimization ways that take technical development results of this project, as well as resultsof other projects, into account to ensure safety of the methods and systems.
(Target TRL upon completion: Level 4)<Supplemental Information> Definitions of Technology Readiness Level (TRL)
Level

Definition Pertinent to This Project

Phase

7

Stage at which practical applications are realized.

Practical Use

6

Stage at which on-site validations are performed.

Field Trial

5

Stage at which a prototype is manufactured based on the actual installation and validations
are performed in a simulated environment at a plant, etc.

Simulated Trial

4

Stage at which functional tests are performed on a test manufactured machine as part ofdevelopment and engineering processes.

Practical
Application
Research

3

Stage at which development and engineering work is performed by applying and combining
conventional experiences. Stage at which development and engineering work is performed
based on basic data in an area where conventional experiences are virtually non-existent.

Applied Research

2

Stage at which development and engineering work is performed and required specifications
are developed in an area where applicable conventional experiences are virtually nonexistent.

Applied Research

1

Stage at which basic information on a development and engineering object is identified.

Basic Research©International Research Institute for Nuclear Decommissioning

III. Implementation Items and Their Correlations (Implementation Item)

10➢ The following issues related to the feasibility of the methods and systems for fuel debris
retrieval based on past reviews conducted by last year was identified.

<Particularly Important Issues for Satisfying the Safety Requirements>• Ensuring Confinement Function• Capture and Removal of Fine Radioactive Particles• Monitoring Fine Radioactive Particles (Especially α Nuclides)➢ In FY 2017 and FY 2018, the development of element technologies are planned for solving
the issues mentioned above and optimizing the debris retrieval methods and systems basedon the results of development.

[Main Project Items]<Developing Element Technologies for the Feasibility of the Methods and Systems>(1) Technical Development related to Confinement Function(2) Technical Development for Dust Collection/Removal Derived from Fuel Debris(3) Studying α Nuclide Monitoring System for Fuel Debris Retrieval<Study on Overall Methods and Systems>(4) Study on Optimization of Ensuring Safety of Methods and Systems©International Research Institute for Nuclear Decommissioning

III. Implementation Items and Their Correlations (among Implementation Items)

11

It is necessary to ensure the system is equipped with the confinement (emission control) function to provide radiation protection.
In this project, element development of important items is conducted as input conditions for the system review [implementation
items (1) through (3)] and the reflection of the results in the methods and systems [implementation item (4) ] is planned.
Input Conditions (Particularly Items Related to
Feasibility)
Safety Requirements
State of the Actual
Installation at 1F* Some of input conditions are set in cooperation with other projects

Functional
Requirements• Required Differential Pressure for
Ensuring Confinement Function• Setting Safety Objectives• Defense in Depth
Requirements• State of Fuel Debris• State of Damage for
PCV/Building• Required Ventilation Rate for
Reducing Hydrogen Concentration• Required Detected Radioactivity
ConcentrationBased on Exposure
Assessment• Required DF Based on Exposure
Assessment

Review Flow
(Facility
Specification)[Terminology] DF: Decontamination Factor• Performance Information of Capture and Collection
Technology

Project Item (2)• Performance Information of Detection Technology

Project Item (3)• Properties of Fine Radioactive Particles(Amount Generated/Particle Size/Transfer Rate
between Gas and Liquid Phases/Specific
Gravity/Chemical Form)• Properties Other Substances than Fine
Radioactive Particles (Impurities such as Oil)
• Environmental Conditions

Project Item (3)Conceptss ofConfinement
Output(Examples) • Methods to Construct Boundary•

Project Item (1)Detailed
Information

Gas Phase: Differential Pressure
Control Liquid Phase: Water Level
Control
System Configurations (Outline)
Project Item (4)SystemSpecifications

Equipment
Specifications

•
•
•
•

• DF
• Model• Pretreatment Method

Target Differential Pressure
Target DF
Target Ventilation Rate
Target Detected (Controlled)
Activity Concentration

Feasibility
Study• SystemSpecifications• System Diagram• Layout Drawing...

A series of reviews are conducted for the project item (4) “Study on Optimization of Ensuring Safety of Methods and Systems.”©International Research Institute for Nuclear Decommissioning

III. Implementation Items and Their Correlations (with Other Research Projects)➢

12

The project shares the conditions to be studied (concepts of safety, element technology, etc.) with otherprojects.
Development of Fundamental Technology for
Retrieval of Fuel Debris and Internal Structures

Retrieval Technology
Characterization• Sharing Analysis
Needs/Results

Upgrading the Comprehensive Identificationof Conditions inside Reactor
Development of Technology for Fuel Debris
Analysis/ Fuel Debris Characterization* Development plans for obtaining fuel debris
solubility property are not contained in the current
implementation plan of the government RandD
project. They and are being coordinated with JAEA
and other organizations.

Internal
Investigation

Development ofTechnology for Detailed
Investigation Inside PCV• Aligned with
Retrieval
Methods andSystems

Sampling
Development of Sampling
Technology for Retrieval of
Fuel Debris and Internal
Structures

Full-Scale Test of Repair andWater Leakage Stoppage
Technologies for Leak
Locations inside PCV

Upgrading of Approach and
Systems for Retrieval of Fuel
Debris and Internal Structures• cooperation of
Task Steps (Determining
the Necessity of PCV
Negative Pressurization,etc.)• Sharing Safety
Scenario(Large-Scale
Earthquake)

Water LeakBlockageTechnology
Development of Repair andWater Leakage Stoppage
Technologies for Leak
Locations inside PCV

Methods and Systems• Sharing
SurveyNeeds/Results• Sharing Safety Scenario

Development of Technology for
Investigation Inside RPV• Sharing Safety Scenario(During Water Leak Blockage
and Removal Work)• Aligned with Water LeakBlockage Steps• cooperation ofCollecting,• Sharing Safety Transferring, andStoring
Scenario
Technologies with
(Criticality
Methods andEvent)
Systems

Seismic
ResistanceCriticality
Control

Development of Soundness
Evaluation Technology for
RPV/PCV

Development of Technology
for Criticality Control Methods

Collecting,Transferring, andStoring Technologies
Development of Technology
for Collection, Transfer andStorage of Fuel Debris©International Research Institute for Nuclear Decommissioning

III. Implementation Items and Their Correlations (with Other Research Projects)➢

13

The table below shows the results from cooperation with other projects.
Cooperation
Method*Input/Output from This Project

No.

Partner Projects

Description

1

Fundamental
Technology Project• Reflect technologies (in general) being developed by Fundamental
Technology Project in method reviews of this project.
• Reflect technologies (mainly processing technology and local collection
facility) being developed by Fundamental Technology Project in systemreviews.

2

Sampling Project• Submit requests to Sampling Project for information necessary inreviewing the methods and systems.

3

Criticality Control
Project• Share the point of view concerning safety, etc., in reviews.
• Share (align) the specifications in consideration of interfacing thecomponents/system.

Participate in themeetings mentioned
in Nos. 1 and 2 asappropriate.

Input: Point of view concerning safety in criticality control,
neutron detector specifications, and system specifications etc.
Output: Conditions to be reviewed for gas monitoring (exhaust
flow rate, etc.)

4Internal Investigation
Project• Submit requests to the Internal Investigation Project for informationnecessary in reviewing the methods and systems.
• Reflect the results of internal investigation in method and systemreviews.

Hold inter-project
meetings asnecessary.

Input: Results of internal investigation (debris locations, etc.)
Output: Requests for internal investigation5

Debris Characterization PJ
Comprehensive
Identification of Conditions
Inside Reactor Project• Receive documents and other materials about the behaviors of α
nuclides during debris processing (the details and timing are being
coordinated) and reflect such information in methods and systems
reviews.

Input: Composition of debris, transfer rate from liquid to gas
phase, etc.
Output: Temperature condition for retrieval, etc.

6

Collecting, Transferring,and Storing
Technologies PJ• Reflect the size of storage canister, restrictions on hydrogencountermeasures, etc., in method reviews.

Input: Storage canister specifications, etc.
Output: Retrieval amount, etc.

7

PCV Repair Project(Repair
Technology/Full-Scale)• Share safety requirements for debris retrieval to align the PCV repair(leak blocking) plan with the methods and systems.

Input: Feasible PCV water level and PCV repair methods
Output: PCV pressure (differential pressure) and exhaust flowrate

8Seismic Resistance
Project• Share understanding of the spreading effects of system configurations
and earthquakes on debris retrieval and review safety scenarios.

Input: Seismic evaluation result and estimation of large-scale
component damage
Output: System configurations for debris retrieval

Hold regular joint
project meetings(once a month).

Input: Amount of particles generated by processing debris andtheir particle size, etc.
Output: Requirements for collecting data during processing
technology development, etc.

Input: Sampling plan (PCV pressure, etc.)
Output: Requests related to sampling* Results of IRID’s internal discussions are shared in regard to general or Input/Output information.
©International Research Institute for Nuclear Decommissioning

14

IV. Schedule [Process Chart (1/3)]
Upgrading of Approach and Systems for Retrieval of Fuel Debris and Internal Structures - FY 2017 Implementation Schedule [As of End of March](1/3)
FY 2018
FY 2017
Subcategory
Category
Apr

1.

Technical Development related to
Confinement Function
i. Technical Development for EnsuringConfinement Function(i) Element Test for Differential
Pressure Control Effective for Dust
Confinement

May

Jun

Jul

Aug

Sep Oct

Nov

Dec

Jan

Mar

Feb

Apr

May

Jun

Jul

Aug

Sep Oct

To Category 4

Mar

Summary

To Category 4

To Category 4

Analysis Conditions Review

a.Analysis Conditions
Review

Revisit Analysis Conditions
Analysis

Reanalysis

b.Analysis

Summaryc. Summary
To Category 4

To Category 4

a.Review Measures/Test
Plan

To Category 4
To Category 4

Test Equipment
Manufacturingb.Test Equipment
Manufacturing

Element Test

c. Element Test

To Category 4

Summary

To Category 4

d.Summary

Major Milestones

Feb

Element Test

d.SummaryLegends
Plan
Possible Acceleration
Postponement
Actual ScheduleLine indicating linkage
between items

Jan

Test Equipment
Manufacturingc. Element Test(iii)Technical Development
for Improving Sealability

Dec

Test Plana.Specification
Review/Test Planb.Test Equipment
Manufacturing(ii) Analyzing Negative Pressure,
Airflow Distribution, etc. of Each
Boundary

Nov

To Category 4

Results of
Solicitation

Interim Report Meeting at IRID Symposium

End-of-Year Report Meeting

Interim Report Meeting

Final Report
Meeting©International Research Institute for Nuclear Decommissioning

15

IV. Schedule [Process Chart (2/3)]
Upgrading of Approach and Systems for Retrieval of Fuel Debris and Internal Structures - FY 2017 Implementation Schedule [As of End of March] (2/3)

1.

Technical Development related
to Confinement Function
ii. Technical Development for
Dose Reduction

FY 2018

FY 2017

Subcategory

Category

Apr

May

Jun

Jul

Aug

Sep Oct

Nov

Dec

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep Oct

Nov

Dec

Jan

a.Scenario Review

b.Exposure
Assessment*c. Summary

2.

Mar

Feb

To Category 4
From Category 4*

To Category 4
From Category 4*

Summary

Subitems “Scenario Review” and “Exposure Assessment” of Item ii
in Category 1 and Category 4 are aligned continually.
(Only a single example is shown here for the sake of simplicity.)

Technical Development for Dust
Collection/Removal Derived from
Fuel Debris
Conceptsual Study/Test Plani Technical Development for Reducing
and Removing Radioactive Materials
in Gas Phase Systema.Conceptsual
Study/Test Plan

Test Equipment
Manufacturingb.Test Equipment
Manufacturing

Element Test
To Category 4

c. Element Test

Summary
To Category 4

d.Summaryii. Technical Development for
Reducing and Removing
Radioactive Materials in Liquid
Phase System
Legends
Plan
Possible Acceleration
Postponement
Actual ScheduleLine indicating linkage
between items

a.Conceptsual Study/Test
Planb.Preparation for
Test/Test Equipment
Manufacturing

Conceptsual Study/Test Plan
Test Equipment
Manufacturing
Element Test
To Category 4

c. Element Test

Summary
To Category 4

d.Summary

Major Milestones

Results of
Solicitation

Interim Report Meeting at IRID
Symposium

End-of-Year Report Meeting

Interim Report
Meeting

Final Report
Meeting©International Research Institute for Nuclear Decommissioning

16

IV. Schedule [Process Chart (3/3)]
Upgrading of Approach and Systems for Retrieval of Fuel Debris and Internal Structures - FY 2017 Implementation Schedule [As of End of March] (3/3)
FY 2018
FY 2017Category
SubcategoryJan
Apr May
Apr MayJun

Studying α Nuclide Monitoring
System for Fuel Debris Retrieval

3.

iConceptsual Study andDevelopment Planning of Detection
Technologies and Systems for α
Nuclides in Gas Phasea. Conceptsual Study

Jul

Aug

Sep Oct

Nov

Dec

Feb

Mar

Jun

Jul

Aug

Sep Oct

Nov

Dec

Jan

Feb

Mar

Conceptsual Study
Developing Development
Plan*As Necessary

b.Developing
Development Plan

Summary

To Category 4c.SummaryTo
Category4Conceptsual Studyii.

Conceptsual Study andDevelopment Planning of Detection
Technologies and Systems for α
Nuclides in Liquid Phasea.Conceptsual Study

Developing Development Plan*As
Necessaryb.Developing
Development Plan

Summary

To Category 4c.Summary

To Category 4

From
From
Category 2 Category 1

4.

Study on Optimization of Ensuring
Safety of Methods and Systems
Legends
Plan
Possible Acceleration
Postponement
Actual ScheduleLine indicating linkage
between items

From
From Category 2
From
Category 1 or 3
Category 1(iii) or(i) or(ii)Category 2

From
From
Category 3 Category 1 From Category 1 (ii)Study on Method Optimization
a.Study on Method
Optimization

Study on System Optimizationb.Study on System
Optimization

Summaryc.Summary

Major Milestones

From Category 1 ii
To Category 1 ii

Results of
Solicitation

From Category 1 ii
To Category 1* iiSubitems “Scenario Review” and “Exposure Assessment” of Itemii in Category 1 and Category 4 are aligned continually.
(Only a single example is shown here for the sake of simplicity.)

Interim Report Meeting at IRID
Symposium

End-of-Year Report
Meeting

Interim Report
Meeting

Final Report
Meeting©International Research Institute for Nuclear Decommissioning

17

IV. Schedule (Summary)➢

The project is progressing well as scheduled at the initial planning stage.

➢

Although the timing for starting “Item i: Technical Development for EnsuringConfinement Function” of Category 1, was modified (delayed for about 3 months), thisis not expected to affect subsequent processes or results at the time of projectcompletion.
[Reason for Schedule Modification]
The schedule was changed to proceed more carefully by hearing from outside
experts .

©International Research Institute for Nuclear Decommissioning

18

V. Project Organization
International Research Institute for Nuclear
Decommissioning (IRID)
Tokyo Electric Power
Company Holdings, Inc.

Hitachi-GE Nuclear Energy, Ltd.
• Assist to evaluate retrieval methods and design
element tests (Company A)• Dust containment test (Company B)• Airflow analysis inside PCV (Company C)• Technical development for improving sealability(Company D)• Backwash HEPA test (Cavendish Nuclear Ltd [UK])• Particle removal performance test in liquid (Company F)• Review debris evaluation and detecting methods(Company G)• Pedestal reinforcement method (Shimizu Corporation)➢ Draw up overall plans and oversee technology management➢ Manage technologies, including technical development
progress

Toshiba Energy Systems and Solutions
Corporation• Measure changes in nitrogen injection flow rate and PC
V differential pressure(Company I)• Analyze negative pressure and airflow distribution in eac
h boundary (Company J)• Review and perform element tests for measures to impr
ove R/B sealability (Company K)• Assist in designs related to exposure evaluation (Compa
ny L)• Element tests for backwashable dry dust collector (Shin
Nippon Air Technologies Co.,Ltd.)• Downsize wet electric dust collector (IHI Corporation)• Develop remote replacement technology for HEPA filters(Shin Nippon Air Technologies Co.,Ltd.)• Element tests for sludge collection technology (IHI Corp
oration)• Assist in reviews related to optimization of methods andsystems (Company M)• Assist in designs related to optimization of methods andsystems (Company N)• Assist in designs related to safety requirements and designs (MPR Associates, Inc. [US])Mitsubishi Heavy Industries, Ltd.
• Assist to review confinement function (Company
Q)• Assist to review dust capture and removal (Company R)• Assist in element tests for dust capture and rem
oval (Company S)• Assist to review optimization of ensuring safetyof methods and systems (Company T)©International Research Institute for Nuclear Decommissioning

19

VI. Implementation Details(1) Technical Development Related to Confinement Function(i) Technical Development for Ensuring Confinement Function[Objectives]•
To confirm the system design conditions (e.g., differential pressure) effective for confinement.
•
To confirm the system design conditions (exhaust amount, amount of nitrogen to fill, etc.)
effective for inactivation (prevention of hydrogen combustion).
•
To review technologies to improve sealability.
End of Fiscal Year 2017: Evaluation of Effectiveness Using Simple Means• Element Test: Develop a test plan
• Simulation: Conduct a trial analysis• Technology for Sealability Improvement: Conduct a desk study
End of Fiscal Year 2018: Confirmation of Effectiveness with Element Test/Simulation• Element Test: Conducting a test
• Simulation: Conducting analyses• Technology for Sealability Improvement: Conduct a desk study (continued) and mockup test
as necessary©International Research Institute for Nuclear Decommissioning

20

VI. Implementation Details(1) (i) Technical Development for Ensuring Confinement Function<Issues to be Solved by Technical Development>⚫ To confine dust generated by a fuel debris retrieval process, negative pressure it going to be controlled by
setting up a boundary and ensuring adequate exhaust is in place that corresponds to openings within thatboundary.
⚫ To establish the confinement technology with boundary settings and negative pressure control, information
about the following issues needs to be obtained.
[Issue (i)]Information on openings within theboundary is unknown.
(Location, dimensions, profile, andquantity)[Issue (iii)]
Need to know the pressure slope
inside PCV.

[Issue (ii)]
Need to prevent outer leakfrom the openings.

[Issue (iv)]
Need to estimate the dust
diffusion for each method.

[Issue (v)]Possible localized accumulationof hydrogen.

©International Research Institute for Nuclear Decommissioning

21

VI. Implementation Details(1) (i) Technical Development for Ensuring Confinement Function<Purpose and Necessity for Development>• To review an action policy to acquire information required for the desired design with regard to issues listed on the previous page.
• To classify and clarifytechnical development objects into analysis, element test, and confirm actual installation.
• The objective is to establish a technology with which necessary information through analysis, element testing, and checking withactual installation can be acquired.
IssuesInformation Required for
DesignAnalysis

Element Test

Confirm Actual
Installation(i) Information on openings
within the boundary

Information on openings todetermine exhaust flow raterequired for maintaining
negative pressure.

(Information on openings
that exist in the actual
installation cannot be
obtained by analysis.)(Information on openings
that exist in the actual
installation cannot be
obtained by element test.)

Propose a test to estimate
information on openings.

(ii) Preventing outer leakfrom the openings

Negative pressure value atwhich in-leak can be
guaranteed locally.

(Verify codes bycomparing local simulation
analysis and test results.)

Validated the negative
pressure control value inelement test for local
simulation.

<Operation withdetermined differential
pressure control value>(iii) Identifying the pressure
slope in PCV

Confirmation that no
localized uneven
distribution of pressure
exists to account for
negative pressure control.

Evaluate the overallpressure distribution in PCV
and confirm required
negative pressure can be
guaranteed throughout
PCV.

(Confirm by analysis.
Comparison of analysis
and element test results
are conduction under (ii).)<Pressure monitoring at
representative points>(iv) Estimating the dust
diffusion for each method

Estimate information on
the location and size ofdust floating in gas phase.

Confirm the dust
distribution in PCV throughdust behavior analysis.

Obtain the information on
dust generated by eachmethod (Fundamental
Technology Project).

<Monitoring dust
concentration>(v) Possible localized
accumulation of hydrogen

Location of accumulatedhydrogen, nitrogen flowrate effective for scavenge,
and positions for injection.

Evaluate locations ofaccumulated hydrogen basedon hydrogen distribution
analysis and review theamount of nitrogen to fill andpositions for injection.

(Confirm by analysis.
Comparison of analysis
and element test results
are conduction under (ii).)<Monitoring exhausthydrogen concentration.
Hard to measure local
hydrogen concentration.>

Notes

Conducted to confirm thefeasibility of a dynamic
boundary for a broken
boundary.

Confirm where to draw aline between local collection
and collection by thesystem.

The angle brackets <> represent proposed measures during debris retrieval.
©International Research Institute for Nuclear Decommissioning

22

VI. Implementation Details(1) (i) Technical Development for Ensuring Confinement Function<Schedule (Achievements and Future Plans)>
STEP-1 Survey Knowledge to Be
Reflected in Analysis Models• Perform a Survey on Fluid Analysis
Technologies and Their Proven
Record of Performance

STEP-2 Develop a Test Plan
• Review Items to Be Checked (Data to Be
Acquired) in the Test Based on STEP-1
Results• Develop a Test Plan

STEP-3 Element Test
• Refine Test Plan
• Test• Build a Model

STEP-4 Confirm
Uncertainties

STEP-5 Analyze Based on
Retrieval Methods• Review Uncertainties inLight of Element Test
Results• Perform Analysis using theRetrieval Conditions

FY 2017

FY 2018

Item
End-of-Year Report Meeting

Interim Report Meeting

MasterSchedule

Interim Report Meeting

Final Report Meeting

Survey Knowledge to Be
Reflected in Analysis Models

Build a Test Plan

Results of reviewing items tobe acquired in order toreinforce the accountabilityof analysis data

Test plan

Element Test (Acquiring Data
for Comparison with Analysis)
Confirm
Uncertainties
Analyze Based on Retrieval
Methods

Feedback to System
StudysTest results

Confirmed
uncertainties

Confinement (differential
pressure control)/
System conditions forpreventing fire andexplosions

Review system configurations
and specifications

Confinement (differential
pressure control)/
System conditions forpreventing fire andexplosions

Review system configurations
and specifications©International Research Institute for Nuclear Decommissioning

VI. Implementation Details

23(1) (i) Technical Development for Ensuring Confinement Function(a) Analyzing Negative Pressure, Airflow Distribution, etc. in Each Boundary
1) Purpose
To establish the 1F analysis model based on flow analysis codes (GOTHIC, CFD code, etc.), taking the differential pressure
control conditions (field data) and state of damage on-site into account. To confirm effectiveness of the following items by
understanding the overall airflow behavior inside the PCV:
➢ Confirm differential pressure control conditions and system effectiveness (in dust emission control) to ensure theconfinement function.
➢ Confirm the possibility of hydrogen accumulation within the PCV and effectiveness of fire and explosion prevention
within the PCV with inert gas supply. (Also confirm these for other areas in the building where hydrogen is likely to havebeen generated, including the torus room.)

2) Scope of Modeling
Scope of Modeling Using Airflow
Analysisin PCV, Cell, Torus Room, etc.

Main Retrieval Method Proposed
in NDF Strategic Plan 2017:
Partial-Submersion Side Access
MethodLeak Potential of PCV• PCV Head
Leak Potential of PCV• Cable Penetration• Piping Penetration• Equipment Hatch,
etc.

Reactor Building

RPV

PCV (D/W)

Retrieval
Equipment

PCV (S/C)

Cell

Pedestal

Exhaust Fan

Areas where hydrogenis likely to have been
generated (e.g. torus
room)

Torus RoomFoundation©International Research Institute for Nuclear Decommissioning

24

VI. Implementation Details(1) (i) Technical Development for Ensuring Confinement Function(a) Analyzing Negative Pressure, Airflow Distribution, etc. in Each Boundary3) Selecting Analysis Codes (Example of Application for Each Evaluation Model)

Purpose ofAnalysis
Example ofApplication

Concentration Parameter Model

Distributed Parameter Model

CFD Analysis Model• Macroscopic Evaluation of State
Quantity in Space• Flow Evaluation between Spaces• Microscopic Evaluation of State Quantity
in Space• Flow Evaluation in Space• Microscopic Evaluation of State Quantity
in Space• Flow Evaluation in Space[GOTHIC]• New Regulatory Requirements:
Evaluation of Hydrogen Behavior in
Building• Evaluation of Vapor Propagation(Overflow)• Investigation of the 1F Accident• Reproducing and Analyzing NUPEC
ISP-35(Developer)[MAAP]• Evaluation of Conformity to the New
Regulatory Requirements
Room Temperature Evaluation during
IS-LOCA by BWR Electric Power
Companies• Evaluation of Conformity to the New
Regulatory Requirements at the
Rokkasho Reprocessing Plant by JNFL
[MELCOR]• Analyzing Boiling Events of Liquid
Waste at Reprocessing Plants Using
MELCOR Code: JAEA-Research2012026[GOTHIC]• New Regulatory Requirements:
Evaluation of Hydrogen Behavior in
Building• Reproducing and Analyzing 1F Reactor
Water Level Gauge Behaviors• Reproducing and Analyzing (NRA)NUPEC ISP-35 (NRA)[STAR-CD]• NUPEC Treatment of Excess Hydrogen(Studying Installation of an Ammonia
Catalytic FCS Inside PCV)[GASFLOW-MPI]• THAI (Germany)• PANDA (Switzerland), etc.
(All of these are VandV by Developers)• BWR (Switzerland, Mexico, andGermany)©International Research Institute for Nuclear Decommissioning

25

VI. Implementation Details(1) (i) Technical Development for Ensuring Confinement Function(a) Analyzing Negative Pressure, Airflow Distribution, etc. in Each Boundary3) Selecting Analysis Codes (Applicability to Flow Evaluation Inside PCV during Debris Retrieval)
Requirements for Modeling

Identifying the Airflow Inside PCV(Macroscopic and Microscopic)

Concentration
Parameter Model

Distributed
Parameter Model

CFD Analysis Model

PCV (D/W) and Cell

Not Applicable

Applicable

Very Applicable

Not Applicable
PCV (S/C) and Building

Applicable

Somewhat
Applicable

Applicable

Applicable

Somewhat
Applicable

Behaviors of Aerosols (e.g. Diffusion, Natural
Deposition, or Removal)

Applicable

Applicable

Somewhat
Applicable

Identifying Hydrogen Behaviors(Accumulation and Substitution)

Applicable

Applicable

Applicable

Somewhat
Applicable
GOTHIC Ver.8.2 Is AppliedSomewhat
Applicable

Airflow Resolution and Ease of Analysis(Sufficient Resolution and Sensitivity
Analysis Are Required)(e.g. Torus Room)
Phase Changes such as Vapor Generation
and Vapor Condensation and Movement of
Substances in Space

Identifying Behaviors Inside the Building(Interface with the Outside of PCV)

Applicable©International Research Institute for Nuclear Decommissioning

26

VI. Implementation Details(1) (i) Technical Development for Ensuring Confinement Function(a) Analyzing Negative Pressure, Airflow Distribution, etc. in Boundary3) Selecting Analysis Codes (Summary)

Flow analysis codes were reviewed that are applicable in analyzing negative pressure, airflow
distribution, etc. in each boundary.
➢ Since the behavior analysis inside the PCV requires evaluating the distribution in that space
while taking into account the differential pressure control conditions and state of damage onsite, the model should identify thermal hydraulic flows by splitting the space into meshes.
➢ Also, although the gas inflow/outflow will be simulated on the outside of PCV (D/W) in order tounderstand behaviors inside the building (e.g. torus room), it is reasonable to apply theConcentration Parameter model for the sake of ease of analysis.
➢ As for the dust confinement function, it is necessary to evaluate aerosol behaviors as well as
the airflow inside the D/W.
➢ Therefore, it is concluded that the GOTHIC code (latest Ver8.2) is the most appropriate for
airflow analysis because it allows simultaneous application of both lumped and distributed
parameters and evaluation of aerosol behaviors.
(Aerosol behavior models incorporated in GOTHIC is currently under investigation.)©International Research Institute for Nuclear Decommissioning

VI. Implementation Details

27(1) (i) Technical Development for Ensuring Confinement Function(b) Element Test for Differential Pressure Control
1) Purpose
To confirm the negative pressure conditions, which can guarantee in-leak locally and are effective for dust
confinement, based on the element test using a simple system and review differential pressure control
conditions for actual installation.
To obtain the velocity field data near the openings to help the verification of local model analysis.

2) Implementation Item
• Measure the velocity field near an opening using the pressure (differential pressure between inside andoutside) conditions of a container with an opening as a parameter to confirm the in-leak.
=> Understand the differential pressure limit and confirm the feasibility of dynamic boundary• Make it possible to change the dimensions, profile, and number of the openings and confiemwhether theform of an opening has an impact to the negative pressure value.
=> Obtain estimated information on openings whose details are unknown• Set the parameter value to between -200 and -300 Pa specified as the pressure (differential pressure
between inside and outside) condition of the primary boundary, and confiemnegative pressure values thatcan guarantee in-leak when different values are assigned to the parameter.
=> Use the results to evaluate the margin time until a standby machine starts up when a fan trip occurs.
(Pressure variations inside the PCV during exhaust fan shutdown are obtained by analysis.)©International Research Institute for Nuclear Decommissioning

VI. Implementation Details

28(1) (i) Technical Development for Ensuring Confinement Function(b) Element Test for Differential Pressure Control
3) Test Equipment and Major Measurement Items (Proposal)
•
•
•
•
•

Duplicated structure with a primary vessel (PCV simulated, 1 m square) and a secondary vessel (2 m square) => Made ofacrylic for visualization
Create openings for simulating openings generated by PCV damage => The area of the openings is adjustable
Generate a negative pressure state by adjusting exhaust volume on the primary side => The pressure is measured
Confirm the area near the opening of the primary vessel is also in an in-leak state=> The velocity field is measured using PIV (Particle Image Velocimetry)
Prepare for a case where simulated dust particles are injected in the primary vessel(Selection and representativeness of simulated particles must be discussed)

DPI

PI

PI

DPI
Pressure
Measurement

Secondary Vessel
Opening• Located as far awayfrom PCV as possible• Create multiple
openings

Secondary
Vessel2m

Primary Vessel

1m
Primary Side
Exhaust1m

1m

Primary Vessel Pressure
between -100 and -400 Pa

2m

PIV measurement of the speed
distribution on the outside of the
2m
opening• Opening simulating the damage on PCV• Replaceable openings so that the test can be
conducted for openings with various profiles anddimensions• Create multiple openings©International Research Institute for Nuclear Decommissioning

VI. Implementation Details

29(1) (i) Technical Development for Ensuring Confinement Function(b) Element Test for Differential Pressure Control
4) Image of Measuring Velocity Field and Test Parameter

Inject Tracer (Smoke)

Laser Light Source

Measurement
Area

High-Speed Camera

Velocity Distribution (Image)[Project Items]• Maintain a negative pressure (-300 Pa) inside the primary vessel, shoot near the area simulating damage with a high-speed
cinema, and compute the speed distribution (base condition).
=> Confirm in-leak is ensured (no outer leak).
=> (Used as the verification data for airflow analysis.)• Change the pressure in the primary vessel between -300 and -50 Pa gradually and measure the speed distribution accordingly.
=> Identify the pressure (differential pressure between inside and outside of the primary vessel) sufficient to ensure in-leak.
• Change the size of the simulated damage and measure the speed distribution accordingly.

©International Research Institute for Nuclear Decommissioning

30

VI. Implementation Details(1) (i) Technical Development for Ensuring Confinement Function(b) Element Test for Differential Pressure Control

5) Items to be Simulated in Element Test
PI

PI

DPI
Pressure
Measurement

Secondary
Vessel2m
Primary Vessel

1m

Primary Side
Exhaust1m

1m

Primary Vessel Pressure
between -100 and -400 Pa

2m

PIV measurement of the
speed distribution on theoutside of the opening

2m• Opening simulating thedamage on PCV

Test Results• Determine the limit differential pressure corresponding to
expected profiles of damage openings• Correlation between exhaust volume W and differential pressure
ΔP (ΔP  W 2)
• The coefficients of the above correlation equation changes as
the profile and area of an damage opening change=> Reflected in the damage opening model for airflow analysis

Differential Pressure (Pa)DPI

Simulate the profile of the damage opening expected on the actual
installation in a reduced size
• PCV head flange (leak in a circumferential direction)• Cable penetration (annular channel), etc.
• Combination of upper section (PCV head) and side (penetration portion)
openings=> Do these have an impact on the flow field of the primary vessel?

Exhaust Volume (m3/s)©International Research Institute for Nuclear Decommissioning

VI. Implementation Details

31(1) (i) Technical Development for Ensuring Confinement Function(c) Test to Estimate the Area of Opening in Actual PCV
1) Proposal for Testing the Amount of Nitrogen to Fill and Increase or Decrease of Exhaust Flow Rate in Order toEstimate the Area of Opening in Actual PCV<Test Purpose>
To review the procedures to estimate the area of opening in the PCV that forms a primary boundary,determine the required airflow rate for maintaining a constant negative pressure in the primary boundary (=airflow rate required in the gas control system), and make on-site measurements. [Adjustment operation withina range where the current control conditions (i.e. a weak positive pressure state to keep the inert state of thePCV) ]
Estimate the resistance coefficient at the opening by changing the flow rate of both the nitrogen filling system
supplying nitrogen to the PCV (RPV) and the PCV gas control system for exhaust from the PCV andmeasuring changes in the differential pressure between inside and outside of the PCV to estimate the area of
opening.
PCV Nitrogen Filling
System (Supply)FI

N2
Generator

FI

Increase/Decreaseof Flow Rate

Increase/Decreaseof Flow Rate

Outer LeakPCV Gas Control System (Exhaust)

dPI

Pressure [Pa]PCV Differential
PCV差圧[Pa]

4000
3500

Differential
差圧[Pa]Pressure [Pa]3000

Polynomial (Differential
Pressure [Pa])多項式 (差圧[Pa])

2500
2000
1500
1000
500
0
0

20

40

60

必要風量（漏気流量）m3/h
RequiredFlow Rate (Leak Flow Rate) m3/h

Differential Pressure Measurement While
Changing Air Supply and Exhaust Volumes

PCV Differential Pressure andRequired Flow Rate with Openings
in PCV (Image)©International Research Institute for Nuclear Decommissioning80VI. Implementation Details

32(1) (i) Technical Development for Ensuring Confinement Function(c) Test to Estimate the Area of Opening in Actual PCV
2) Preparation Items for Testing the Amount of Nitrogen to Fill and the Change of Exhaust Flow Rate in Order
to Estimate the Opening Area in Actual PCV (Under Consideration)(i) Proposed Test Overview (As Described in Previous Two Pages + This Page)a) Test to Estimate the Amount of System In-Leak
Estimate the amount of leak in the PCV gas control system and N2 filling system by changing the
supply and exhaust flow rates while maintaining the PCV pressure at a constant target value.
When the PCV pressure is constant, the amount of leak is the same for PCV and parts at the samepressure level. Compute changes in the flow rate difference between supply and exhaust as the leakin the PCV gas control system or N2 filling system.
b) Test to Estimate the Area of Opening in PCV
Change the PCV pressure by changing the supply and exhaust flow rates, calculate the amount ofleak from the PCV, and estimate the area of opening(the value determined here is equivalent to the“Area * Resistance Coefficient” of the opening). [Example - Unit 1: About the same size as an orificewith a size of 10 mm in diameter (Operation Database as of January 22, 2018)](ii) Confirming System Specifications for the Actual Installation <TEPCO HD>
Confirm the exhauster specifications, pressure, and flowmeter accuracy (including the availability oftemperature/pressure calibration).
(iii) Studying System Specifications Required for Testing <TEPCO HD>
Evaluate the accuracy of the flow rate change width, pressure indicator, and flowmeter required for the tests
mentioned in a) and b) above, confirm the applicability of current facilities, and propose plans to modify theactual installation as necessary.
(iv) Conducting Tests and Organizing Test Results <TEPCO HD>©International Research Institute for Nuclear Decommissioning

VI. Implementation Details

33(1) (i) Technical Development for Ensuring Confinement Function(d) Reviewing Measures to Improve Sealability
Conceptsual proposals for the container structure were reviewed to improve sealability during fuel debris retrieval.
•

All-Encompassing Container: Covers the entire existing facilities•

Individual Container: Each covers a fuel debris retrieval cell only•

SSC (Single Skin Container): Container walls are built with onefold panels•

WSC (Double Skin Container): Container walls are built with twofold panels
All-Encompassing Container
SSC
Inside isnegatively
pressurizedExhaustFacility

Container

Proposed
Structure

Confinement

Exhaust Facility

Individual Container
SSC
Inside isnegatively
pressurizedExhaustFacility

All-Encompassing Container
WSC
Inside isnegatively
pressurizedExhaustFacility

Individual Container
WSC
Inside isnegatively
pressurizedExhaustFacility

Container

Exhaust Facility• Covers the entirety of the fueldebris retrieval cells and theirancillary facilities. (Imagine afull-scale container.)• Can be built without applying
load on the building.

• Covers the fuel debris retrieval
cells individually for retrieval
from the top and the side.
• Additionally requires sufficientbuilding structure strength andinstallation of a mount.

The inner space enclosed in thecontainer is negatively
pressurized and confined.

Each fuel debris retrieval cell is
enclosed individually in a container
and confined through negative
pressurization.

Exhaust Facility

Exhaust Facility• Covers the entirety of the fuel debris
retrieval cells and their ancillaryfacilities.
• This proposed structure wasadopted in Chernobyl.
• Can be built without applying loadon the building.

• Covers the fuel debris retrieval
cells individually for retrieval
from the top and the side.
• Additionally requires sufficientbuilding structure strength andinstallation of a mount.

The inside of the container is
The inside of the container isnegative pressurized andnegative pressurized and©International ResearchInstitute for Nuclear Decommissioning
confined.
confined.

34

VI. Implementation Details(1) (i) Technical Development for Ensuring Confinement Function[Summary](a) Analyzing Negative Pressure, Airflow Distribution, etc. in Each Boundary• In FY 2017, in order to ensure the confinement function, a verification method was selected thatcombines analyses and tests and an analysis code for verification, analysis conditions werereviewed, and a trial analysis was conducted.
• In FY 2018, analyses on the negative pressure and airflow in each boundary (entire area) will be

conducted.
(b) Element Test for Differential Pressure Control• In FY 2017, items to be confirm ed in an element test were reviewed. [Reviewed simultaneously with
Item (a)]• In FY 2018, the element test will be conducted and the limit differential pressure evaluated.
(c) Test to Estimate the Area of Opening in Actual PCV• In FY 2017, the concept of test methods were reviewed.
• In FY 2018, test methods will be further reviewed and a proposal to TEPCO HD submitted.
(d) Reviewing Measures to Improve Sealability• In FY 2017, conceptual proposals for the container structure were reviewed.
• In FY 2018, measures to improve the sealability of the container structure and its ancillary facilities
will be reviewed.
©International Research Institute for Nuclear Decommissioning

35

VI. Implementation Details(2) Technical Development for Dust Collection/Removal Derived from Fuel Debris[Objectives]
To select advantage technologies for retrieving fuel debris, obtain data, and review
systems.

End of FY 2017: Select Effective Model and Review Systems
Technical Investigation: Create technology mapping and evaluate technologies
to identify better ones
Element Test: Develop a test plan
System Study: Study on the systems based on results of technology
investigation
End of FY 2018: Obtain Data and Review Systems
Technology Investigation: None (Additional investigation will be conducted asnecessary)
Element Test: Conduct a test
System Study: System study based on result of elemental test

©International Research Institute for Nuclear Decommissioning

36

VI. Implementation Details(2) Technical Development for Dust Collection/Removal Derived from Fuel Debris(i) Technical Development for Reducing and Removing Radioactive Materials in Gas Phase System

1) Gas System Overview⚫

The (proposed) configurations for the gas phase particle capture and removal facility are as follows:(i)

As the particle capture portion of the gas phase particle capture and removal facility takes final performance credit for the gas
system in terms of performance and results, a high efficiency particle filter (HEPA filter) should be installed at the final stage.

However, there is a concern that this filter may need to be replaced frequently due to clogging.
(ii)

To protect the high efficiency particle filter and reduce the frequency of replacement, a pretreatment system should beinstalled to provide coarser filtering of particles before the final treatment.
Pretreatment
Facility

Final Treatment
Facility

HEPA

Pretreatment
SystemAtmospheric Dust, Sea
Salt Particles, etc.

Released to the
Atmosphere< 0.1 μm

Particles Generated by
Cutting Debris

Captured Particles areTransferred by Replacing Filters
Captured Particles are Transferred
by Washing or Using a Container
The pretreatment and final treatment are defined as follows:

Figure - (Proposed) Configurations for the Gas
Phase Particle Capture and Removal Facility(i) Pretreatment: Larger particles up to 1 μm (tentative definition, revised in
response to treatment methods)(ii) Final Treatment: Captures particles with the size of approximately 0.1 μm©International Research Institute for Nuclear Decommissioning

37

VI. Implementation Details(2) Technical Development for Dust Collection/Removal Derived from Fuel Debris(i) Technical Development for Reducing and Removing Radioactive Materials in Gas Phase System

2) Technology Benchmarking (Selecting Advantage Technologies)
Based on the results of the technical study, technologies which did not meet the system conditions in terms of the throughput andperformance were excluded, and the remaining equipment, based on similar principles, was further narrowed down by comparing theirremoval performance, amount of waste, and maintenance etc. to select advantage technologies.
<Reasons for Selecting Multiple Models>• As the system’s entry conditions (e.g. the diameter and amount of particles, pH, and the presence/absence of boric acid) of the actual installationentail a great deal of uncertainties, technologies with different features were selected so that changes in these conditions can supported.
• In this project, although a single system configuration was set up to review the layout, alternative rearrangement plans in response to theconditions of the actual installation were also considered.
Table - Gas Phase Particle Capture and Removal Facilities (Selected Advantage Technologies)[Pretreatment System]

Model

Centrifugal Dust Collection

Electric Dust Collection

Principles and Features

A cyclone-type dust collector.
Captures particles more efficiently
than conventional cyclone structuresby attenuating the drag acting on
particles.

Captures particles by giving anelectric charge to various particles
contained in the dust air anddrawing them to collecting
electrodes.

Wet Dust Collection
Captures particles in water byrunning particles through anunderwater filler.

Filter Dust Collection
Filters particles contained in dusty
gas with layers of particles adheredand deposited on the surface of andinside filter cloths.
Cleaning

Schematic Drawing

Fan

Released to the Atmosphere

Mist Separator

ShowerShowerFillerExhaust Gas

Feed water

Overflow

Chemical Input Port

Drain
Drain

Filter Cloth

Advantages inApplication to 1F

The removal capability is relatively
low. Produces minimal waste (noconsumables and liquid waste),small, and has a wide range ofapplication.

The removal capability is relatively
high. However, restrictions of thismodel include the need toconfiemthe electrostatic propensityof particles and take measuresagainst moisture (to prevent sparks).

Insufficient data is available about its
removal capability (for particles).
Has an exclusive advantage that
other models do not have - capableof removing gas components if
necessary.

Superior in terms of the removal
capability, range of application, andproven record of performance, but
produces waste. Used to extract organic
elements for which this model has anextensive proven record of performanceand metallic elements to reduce waste.

[Supplemental Information] A high reliability filter dust collection model was selected to ensure wide availability for use and a sufficient removal capability.
©International
Institute for Nuclear Decommissioning
In addition, as the filter dust collection model produces filter waste, a filterless model
was also Research
selected.

38

VI. Implementation Details(2) Technical Development for Dust Collection/Removal Derived from Fuel Debris(i) Technical Development for Reducing and Removing Radioactive Materials in Gas Phase System

2) Technology Benchmarking (Selecting Advantage Technologies)
Table - Gas Phase Particle Capture and Removal Facilities (Selected Advantage Technologies)
Model
Principles and Features[Final treatment System]

HEPA (Glass Fiber)

HEPA (Metal)

ULPA (Glass Fiber)

Filters particles contained in a
portion of air with layers of particles
adhered and deposited on thesurface of and inside filter cloths.

Removes particles in the gas phasewith filters with adjusted pore sizes.

Filters particles contained in a
portion of air with layers of particles
adhered and deposited on thesurface of and inside filter cloths.

Can support the target removal
performance (DF =10 5). Has apermitted and authorized record of
performance.

This model’s removal performance isequivalent to that of glass fiber filters.
Although this model does not have apermitted and authorized record of
performance, it has an advantage interms of the amount of waste andenvironmental applicability.

Superior in terms of the removal
performance. (When compared to HEPA,
the single-item performance of ULPA ishigher by approximately 2 orders ofmagnitude.) Considered an option in thecase where a higher level of removal
performance is required than thatcurrently available.

Schematic Drawing

Advantages inApplication to 1F[Supplemental Information] Dust collection methods based on the principle of filtration were selected, because it is necessary to guarantee ahigh removal capability regardless of the particle size in treating exhaust emitted to the environment.
In addition to HEPA (glass fiber) with an extensive proven record of performance, two models were selected inconsideration for supporting changes in the entry conditions and requirements.

©International Research Institute for Nuclear Decommissioning

VI. Implementation Details

39(2) Technical Development for Dust Collection/Removal Derived from Fuel Debris(i) Technical Development for Reducing and Removing Radioactive Materials in Gas Phase System

3) Necessity for Element Test
Items to Be Confirmed in
the Test
Removal Performance

Model

Necessity for Element Test

Items to Be Confirmed in the Test
(Data Acquired/Criteria)* Shown in red are where each item is reflected

Centrifugal Dust Collection

Insufficient data is available about its removal performance forparticles with a higher specific gravity including UO2.

Removal performance for simulated particles=> Exposure Assessment

Wet Dust Collection

Insufficient data is available about its removal capability for particles
because this model is generally used for removing gas components.

Removal performance for simulated particles=> Exposure Assessment

Filter Dust Collection
Electric Dust Collection(Can be designed once the entry conditions are in place.)

Filter Dust Collection (Filter Material:
Metal)

Insufficient performance data is available about its dependency on the Differential pressure recovery performance forparticle size and humidity.
simulated particles and environmental conditions=> Evaluation of the Frequency (or Necessity) of
Replacement

Filter Dust Collection (Filter Material:
Glass Fiber/Organic Fiber, NonMetal Materials)(An extensive proven record of performance data is available about its
dependency on the particle size and humidity.)

Remote Replacement
Technology(Particle Collection
Container)

Common to All Models (Not Neededfor Models that Collect Particles as
Liquid Waste)

Generally, when containers need to be replaced while suppressing
Replaceability.
dispersion, human intervention or large-scale equipment (e.g. within a Ensured sealability after replacement.
plant) is used. Therefore, it is necessary to develop a technology for=> Maintenance Policy and Component Layout
replacing collection containers of the gas system.

Remote Replacement
Technology(Filter)

Common to All Square Filters

No proven performance record is available for any technologies
Replaceability.
capable of remote replacement of square filters while ensuring the
Ensured sealability after replacement.
sealability and seismic resistance. Therefore, a new technology needs => Maintenance Policy and Component Layout
to be developed.

Common to All Cylinder Filters(Replaced in the Horizontal
Direction)

The technology for replacing filters in the vertical direction is largescale (10 m or higher) and largely restricted in terms of the layout(e.g. hard to be installed inside R/B). Therefore, in consideration of
the layout feasibility, the need is high for equipment that is small andcan support replacement in the horizontal direction.

Common to All Cylinder Filters(Replaced in the Vertical Direction)(This technology is used in Rokkasho and retreatment facilities in the
US and UK.)

Backwash Performance

Replaceability.
Ensured sealability after replacement.
=> Maintenance Policy and Component Layout=> An element test is being prepared for acquiring data missing from the “Necessity for Element©International
Test.” Research Institute for Nuclear Decommissioning

VI. Implementation Details

40(2) Technical Development for Dust Collection/Removal Derived from Fuel Debris(i) Technical Development for Reducing and Removing Radioactive Materials in Gas Phase System

4) Test Conditions
The table below shows major test conditions and the concept behind them.
Type
Simulated
Particles

Item

Test Conditions

Particle (Pretreatment)
Size
0.1, 1, and 4 μm
[Tentative](Final Treatment)
0.1, 1 μm [Tentative]

Specific
Gravity

Process
Conditions

Flow
Rate

Gas
Composition

Tungsten Dioxide (11)
SUS316L (8)Silica Sand (2.6–2.7)

Concepts

Notes

The following evaluation results are considered:
the particle distribution in laser processing(between 0.1 and a few μm) and machining (afew μm or larger), and the maximum particle size
associated with the gas.

• Specified based on the particle size distribution during processing
obtained by now.
• Multiple particle sizes were tested in a single particle size test to
confirm the degree of performance dependency on the particle size.
• Characteristics were obtained as a reference when particles ofmultiple sizes flow simultaneously. (Expected effects include
improvement of the removal performance by captured particles.)If the pretreatment can remove particles with asize of a few μm and larger, refining theconditions will also be considered.

Equivalent to Fuel (UO2) (11)Equivalent to Structure (Stainless) (8)Equivalent to Concrete (2 to 3)

The following are included in the conditions:(Equipment Dependent on
100 m3/h: Equivalent to the estimated amount of
the Flow Rate)in-leak at the opening of the actual installation of
Unit 1 + the minimum amount of nitrogen to fill.
100, 500, 1000, and 2000
2000 m3/h: Conditions reviewed last year.
m3/h(Pretreatment)
Up to 100%

In pretreatment, the assumption is that humidity
adjustment is not performed due to possible
inflow of flammable gas.

Humidity(Post-Treatment)-

In the post-treatment, the assumption is that thehumidity can be adjusted through temperatureadjustment because target fluids have alreadybeen treated in the pretreatment.

• Tests were conducted under multiple conditions by referring to thespecific gravity of estimated materials that comprised the fuel debris.
Data was acquired on the degree of dependency on the specificgravity.
• Although no cleaning target is in place and conditions are not fixed
on the system side, conditions were set based on the concept shown
to the left.
(Even when the flow rate falls outside these conditions, adjustments
can be made based on the number (area) of elements except for thecentrifugal method. The centrifugal method requires an estimation
based on the test and existing data.)• For items on which humidity is expected to have less impact, tests
will be conducted under two humidity conditions for confirm ation. (Forsimilar methods, however, the rationalization of test cases is being
considered by, for example, selecting and testing only one model as arepresentative case.)• In order to widen the range of operating conditions, considerations
are being made to determine whether tests should be conductedusing multiple humidity conditions.

©International Research Institute for Nuclear Decommissioning

41

VI. Implementation Details(2) Technical Development for Dust Collection/Removal Derived from Fuel Debris(ii) Technical Development for Reducing and Removing Radioactive Materials in Liquid Phase System

1) Liquid System Overview⚫

The (proposed) configurations for a new circulation cooling facility are as follows: The facility should have a capability to process at 3m3/h equivalent to the current rate of water injection to the reactor with a baseline circulation flow rate of 10 m 3/h.
(i)Insoluble α Nuclides Removal Facility
Composed of up to three types of removal equipment (e.g. filters).

(ii)

Soluble Nuclides Removal Facility
As a subsequent stage following the insoluble nuclide removal, composed of equipment (adsorption vessel) for removing
soluble nuclides.
(i) Insoluble α Nuclides Removal Facility
CoarseFiltering

Treatment
TargetWater

Remove(Large)Particles

MediumFiltering< a few
dozen μm

Remove (Small
to Large)
Particles

Drain Water(ii) Soluble Nuclides Removal Facility

Final
Treatment< a few μm

Backwash
Water

Adsorption< a few
hundred mm

Remove(Fine)
Particles
Backwash
Water

Coarse filtering, medium filtering, and final treatment are defined asfollows:A) Coarse Filtering: Captures particles with a size of a few dozen μmB) Medium Filtering: Captures particles with a size of a few μmC) Final Treatment: Captures particles with a size of 0.1 μm or so

Treated
Water

Adsorption
VesselBackwash
Water/Drain Water
Treatment*

The coarse filtering (to remove large particles) and medium filtering (toremove particles from small to large) processes are common to boththe primary and secondary boundary water treatment systems.

α Nuclide
Adsorption Vessel

Transport Used
Adsorption Vesselto Storage Area

Feed Treated Water toCirculating System

Debris Particles

Transfer container contents to the debris collection or waste storage area
Figure - (Proposed) Configurations for Circulation Cooling Cleaning Facility* The drain water and backwash water are treated in a separate facility as they
are not drained continuously.
©International Research Institute for Nuclear Decommissioning

42

VI. Implementation Details(2) Technical Development for Dust Collection/Removal Derived from Fuel Debris(ii) Technical Development for Reducing and Removing Radioactive Materials in Liquid Phase System

1) Liquid System Overview (Facilities Under Review)⚫ The review items required for realizing a liquid system that meets the safety requirements are as follows:(i)

Suppressing Radioactive Emission (Capturing Insoluble α and Soluble Nuclides)(ii) Collecting Captured Particle Nuclides(iii) Collecting Waste (e.g. Filters)(iv) Reducing Waste⚫

The table below lists facilities under review for each issue:
Table - Issues for Realizing the System that Meets the Safety Requirements and Facilities Under Review
Facilities Under Review
Issues Relating to the System Feasibility

Circulation Cooling Facility
Insoluble α Nuclides
Removal Facility

Soluble Nuclides
Removal Facility

Contaminated Water
Treatment Facility(i)Suppressing Radioactive Emission

Reviewed

Reviewed

Reviewed(ii)

Collecting Captured Particle Nuclides

Reviewed

-

-

(iii)

Collecting Waste (e.g. Filters)

Reviewed

Reviewed-(iv)

Reducing Waste

Reviewed

Reviewed

Reviewed©International Research Institute for Nuclear Decommissioning

43

VI. Implementation Details(2) Technical Development for Dust Collection/Removal Derived from Fuel Debris(ii) Technical Development for Reducing and Removing Radioactive Materials in Liquid Phase System

2) Technology Benchmarking (Selecting Advantage Technologies)
Based on the technical study results, technologies which did not meet the system conditions in terms of throughput and performance were
excluded, and the remaining equipment, based on similar principles, was further narrowed down by comparing removal performance, amountof waste, maintenance, etc., to select advantage technologies.
* The reasons for selecting multiple models are the same as those for the gas phase system. (See page 44)

Table - Liquid Phase Particle Capture and Removal Facilities (Selected Advantage Technologies) [Insoluble (Particle) Nuclides Removal (Coarse/Medium Removal)]
Application

Coarse Filtering

Model

Liquid Cyclone

Principles andFeatures

Separates particles with higher
specific gravity by applying
centrifugal force to the waterflow.

Schematic Drawing

Medium Filtering
Auto Strainer

Removes particles by passing
the water through the screen.
The filter can be automaticallycleaned with swirl flows.

High-Capacity Filter(e.g. Bag Filters)

Large Pore Microfiltration(MF Membrane) Filter

The water is poured into thetubular inside of the filter unit tomove solid materials to theinside and the liquid to theoutside.

Separates particles from waterby letting the water through finepores. Backwashable due to its
higher physical strength.

The particles with a relatively
larger size can be surely
removed by selecting the filter
pore size. Plenty of particles canbe collected.

The particles with a relatively
larger size can be surely
removed by selecting the filter
pore size. Waste reduction canbe expected by backwashing.

Outlet

Inlet

Filtrate

Drain(Sludge Discharge)

Vortex Tube

Extraction

Advantages inApplication to 1F

Separation of particles by
centrifugal force is effective forremoving debris particles withhigher specific gravity.

Larger size particles can be
surely separated by the strainer
in addition to the centrifugal
force. Also, it is small and has asimple mechanism and highmaintainability.

[Supplemental Information] Since coarse filtering is intended to reduce waste at the pre-stage of filtering and membrane dust collection by removing larger size particles (a few dozen μm orlarger), two filterless centrifugal models with lower application risks were selected.
Medium filtering is intended to surely remove relatively large sized particles (a few μm or larger) at the pre-stage of membrane dust collection, adjust operating
conditions of membranes, and reduce waste.
©International Research Institute for Nuclear Decommissioning
Two filtering models were selected by taking into account the required functions and applicability.

44

VI. Implementation Details(2) Technical Development for Dust Collection/Removal Derived from Fuel Debris(ii) Technical Development for Reducing and Removing Radioactive Materials in Liquid Phase System

2) Technology Benchmarking (Selecting Advantage Technologies)
Table - Liquid Phase Particle Capture and Removal Facilities (Selected Better Technology)[Insoluble (Particle) Nuclides Removal (Final Treatment)]
Application

Final Treatment

Model

Principles andFeatures

MF Membrane

UF Membrane

Separates particles from water by letting the water through fine pores.
Backwashable due to its higher physical strength.

Schematic Drawing
Filtrate

Filtrate

Filtrate

Unfiltered Solution

Filtrate

Inorganic Membrane

Organic
Membrane

Advantages inApplication to 1F

Removable minimum particle size islarger than UF membranes, but theblockage risk is relatively low.

Removable minimum particle size issmaller than MF membranes, but theblockage risk is relatively high.

[Supplemental Information] As a model to surely remove particles with a size of 0.1μm or larger which is required for preventing the blockage ofthe adsorption vessel to remove soluble nuclides (i.e. increased replacement frequency), two successful principles(models) including in the general industries were additionally chosen.

©International Research Institute for Nuclear Decommissioning

45

VI. Implementation Details(2) Technical Development for Dust Collection/Removal Derived from Fuel Debris(ii) Technical Development for Reducing and Removing Radioactive Materials in Liquid Phase System

2) Technology Benchmarking (Selecting Advantage Technologies)
Table - Liquid Phase Particle Capture and Removal Facilities (Selected Better Technology) [Insoluble Nuclides Removal]
Model

Adsorption Vessel (Organic BaseMaterial)

Adsorption Vessel (Inorganic BaseMaterial)

Reverse Osmosis Membrane(including Nanomenbrane)

Schematic Drawing

OxygenTitanium

Example:TannixAdvantages inApplication to 1F

Ion exchange resins are not selective ofadsorbed ions, but can remove various
ions simultaneously. Tannic acidcompounds are known to adsorb actinide
elements. However, not a lot has been
known about them under coexistencewith highly concentrated boric acids, so
additional confirm ation is required with a
test.

Example: Titanates

Bariumなど

They are known to adsorb actinide
elements such as oxine-impregnatedactivated charcoal, zeolites, titanate
compounds, and titanium silicatecompounds. However, not a lot has been
known about them under coexistencewith highly concentrated boric acids, so
additional confirm ation is required with a
test.

Reverse osmosis membranes are known
to be able to block almost all ions.
Similarly, nanomembranes are known tobe able to block a lot of multivalent ions.
However, since both of these membranes
generate concentrated water containing
collected ions, it is necessary to consider
how to treat the concentrated water
before adopting them.

[Supplemental Information] Based on the performance of removing soluble radioactive materials contained in liquid waste to a level ofconcentration restricted in public notifications and a proven record of application in 1F, two principles (3 models), namely, adsorption
vessels (organic/inorganic base materials) and reverse osmosis membrane were selected.

©International Research Institute for Nuclear Decommissioning

46

VI. Implementation Details(2) Technical Development for Dust Collection/Removal Derived from Fuel Debris(ii) Technical Development for Reducing and Removing Radioactive Materials in Liquid Phase System

3) Necessity of Element Test (Overall)
Type

Insoluble
NuclidesRemovalItems to Be
Confirmed in the
Test
RemovalPerformance

Information about
Waste

Model

Items to Be Confirmed in the Test
(Data Acquired/Criteria)* Shown in red are where each item isreflected

Necessity for Element Test

Liquid Cyclone
Auto Strainer

Insufficient data is available about its removal performancefor particles with a higher specific gravity including UO 2.

Filter Dust Collection (Filter, Membrane)(Can be designed once the entry conditions are in place.)

Drain Water Properties(Liquid Cyclone, Auto Strainer)

Insufficient data is available about the properties of drainwater corresponding to expected specific gravities andparticle sizes.

Backwash Performance and Backwash
Water Properties(Sintered Metal Filter, MF Membrane, andUF Membrane)

Insufficient data is available about the backwash
performance and the properties of drain watercorresponding to expected specific gravities and particle
sizes.

Removal performance for simulated particles=> Exposure Assessment

Drain water properties for simulated particles
and environmental conditions=> Review Drain Water Treatment Facilities
Differential pressure recovery performance forsimulated particles and environmental
conditions=> Evaluate the Replacement Frequency(Necessity) and Review Backwash Water
Treatment Facilities

Soluble Nuclides Removal
RemovalPerformance

Adsorption Vessel (Adsorbing Material)

Insufficient data is available about its removal performancefor expected nuclides and operating environment.
The impacts of sodium pentaborate are hard to evaluate.

Information about
Waste

Adsorption Vessel (Adsorbing Material)

Insufficient data is available about its (limit) removal
performance for expected nuclides and operating
environment.
The impacts of sodium pentaborate are hard to evaluate.

Removal performance for simulated liquid waste(Because some nuclides including Pu are hard tobe obtained within the available period of time,they are evaluated based on literature research.)=> Capacity of Facility, Equipment Layout
The amount of water that can be conveyed for
simulated liquid waste(Because some nuclides including Pu are hard tobe obtained within the available period of time,they are evaluated based on literature research.)=> Amount of Waste Generated, Maintenance
Policy=> An element test is being prepared for acquiring data missing from the “Necessity for Element Test.”©International Research Institute for Nuclear Decommissioning

47

VI. Implementation Details(2) Technical Development for Dust Collection/Removal Derived from Fuel Debris(ii) Technical Development for Reducing and Removing Radioactive Materials in Liquid Phase System

3) Necessity for Element Test (in Existing Contaminated Water Treatment Facility)⚫ After the liquid system is constructed, it is necessary to ensure a certain level of nuclides removal performance andsuppress the amount of waste generated to the current level or lower in the existing water treatment facility.
⚫ In the existing water treatment facility, it is required to treat the water added from outside into the circulation coolingsystem such as groundwater flowing into the reactor building.
⚫ Sodium pentaborate may be contained in the cooling water for preventing re-criticality during a debris retrieval
process. If this is the case, the Corrosion Control PJ (active until FY 2016) was made aware that the treatment
performance at the existing water treatment facility might be affected, and the amount of waste generated might beincreased.
⚫ When treatment processes in the existing facility are affected, it may be required to take measures against thedischarged water when it is drained from the circulation cooling system. To clarify the conditions of acceptance inthe existing facility, tests are conducted on a range of matters for which data had not been acquired until last year.
RO
RO
Fresh
Water

RO Equipment(Salt Content
Removal)Concentr
ated
Water

Iron
Coprecipitation
Facility
Carbonate
Precipitation
Facility

CST
From theCirculation
Cooling
Facility

Adsorption
Facility(Cs/Sr Removal)

Adsorption Facility(Multiple Nuclide
Removal)Figure - Configuration Outline of Contaminated
Water Treatment Facility

PostTreatment
Water
Tank
©International Research Institute for Nuclear Decommissioning

VI. Implementation Details

48(2) Technical Development for Dust Collection/Removal Derived from Fuel Debris(ii) Technical Development for Reducing and Removing Radioactive Materials in Liquid Phase System

4) Test Conditions
The table below shows major test conditions and the concept behind them.
Type

Item

Test Conditions

Simulated
Particles

Particle
Size(Coarse Filtering)
10 μm and 100–200 μm[Tentative](Medium Filtering)
0.1, 5, and 10 μm[Tentative](Final Treatment)
0.1, 1 μm [Tentative]
Specific
Gravity
Process
Conditions

Flow
Rate

Liquidity

pH

Tungsten Dioxide (11)
SUS316L (8)Silica Sand (2.6–2.7)

Concepts

Notes

The following evaluation results are considered: theparticle distribution in laser processing (between 0.1
and a few μm) and machining (a few μm or larger),and the maximum particle size associated with thegas.

* Need to align with Fundamental Technology Project.
• Specified based on the particle size distribution during processing
obtained by now.
• Multiple particle sizes were tested in a single particle size test to confirm
the degree of performance dependency on the particle size.
• Characteristics were obtained as a reference when particles of multiple
sizes flow simultaneously. (Expected effects include improvement of theremoval performance by captured particles.)• Since effective removal (separation) of particles with a size of a few μm
or smaller cannot be expected with a coarse filtering facility, it is excluded
from the test conditions.

If the coarse filtering step can remove particles of acertain size and larger, refining the conditions will beconsidered.
If the coarse and medium filtering steps can remove
particles of a certain size and larger, refining theconditions will be considered.
Equivalent to Fuel (UO2) (11)Equivalent to Structure (Stainless) (8)Equivalent to Concrete (2 to 3)• Tests were conducted under multiple conditions by referring to thespecific gravity of estimated materials that comprised the fuel debris. Data
was acquired on the degree of dependency on the specific gravity.

The following are included in the conditions:• Although no cleaning target is in place and conditions are not fixed on the
3 m3/h: A flow rate confirm ed to be sufficient in terms system side, conditions were set based on the concept shown to the left.
(Equipment Dependent onof cooling.
(Even when the flow rate falls outside these conditions, adjustments can be
the Flow Rate)
20 m3/h: A sufficient flow rate for replacing themade based on the number (area) of elements except for the centrifugal
3,10, and 20 m3/h
holding water quantity in about a month (two weeks if method. The centrifugal method requires an estimation based on the test
D/W is used) in the case of flooding.
and existing data.)
Since this test is intended to confirm the performance The behaviors of actual particles (aggregation, deposition, and dissolution)
Neutral(Adjusted by using industrial against different particle sizes and specific gravities, if are assumed to change depending on their pH levels. This technicalwater or dispersing agents, the particle size changes by aggregation, the use of development is intended to obtain information enabling a performancedispersing agents, etc., will be considered (To beassessment once the particle sizes and specific gravities are confirm ed
etc.)
confirm ed in a beaker test in advance.)
under the pH conditions of the actual installation. (If it is difficult to dissolve
the aggregation of particles using a reasonable test method, the particle
size is measured during a test directly through sampling to summarize therelationship between the particle size and equipment performance.)©International Research Institute for Nuclear Decommissioning

49

VI. Implementation Details(2) Technical Development for Dust Collection/Removal Derived from Fuel Debris[Schedule]
STEP-1 Technology Mapping (i)• Research literature andmanufacturers based on the resultsof reviews conducted last year andcomprehensively
clarifytechnologies.

STEP-2 Technology Mapping (ii)
• Sort out evaluation items andconduct a primary evaluation oftechnology based on them

STEP-3 Develop Test Plan
• Sort out and identify issues orinsufficient data to summarize data to
be obtained in the test.
• Develop a Test Plan

STEP-4 Test
• Refine Test Plan
• TestFY 2018

FY 2017
Item

Master Schedule

Technology Mapping (i)(Technical Investigation)
Technology Mapping (ii)(Narrowing Down Advantage
Technologies)

Interim Report Meeting

End-of-Year Report Meeting

Interim Report Meeting

Final Report Meeting

Results of
Research on
Existing
Technologies

Results of Selecting
Significant
Technologies

Build a Test Plan
(Outline Plan)

Element Test Results(Equipment Performance/Layout
Conditions)

Element Test
(Detailed Plan, Test)
Feedback to System
Studys

Review of Equipment Models and Specifications andSystem Configurations

Review of Equipment Models and Specifications andSystem Configurations©International Research Institute for Nuclear Decommissioning

50

VI. Implementation Details(2) Technical Development for Dust Collection/Removal Derived from Fuel Debris[Summary]➢

Conducted research on the existing technologies, both inside and outside Japan, forremoving dust and soluble nuclides.

➢

Reviewed the technologies’ applicability in debris retrieval to select advantage
technologies.

➢

Based on the selected advantage technologies, identified data to be obtained in theelement test and technologies to be developed in order to study system optimization.

➢

Currently, the preparation for the element test is in progress, and FY 2018 will focus on
the element test and evaluations.

©International Research Institute for Nuclear Decommissioning

51

VI. Implementation Details(3) Study on α Nuclide Monitoring System for Fuel Debris Retrieval[Objectives]• Target setting and system study for monitoring, and development planning asnecessary

End of FY 2017: System Outline Review (at a Level that Allows Feasibility
Judgement)
Technical Investigation: Create technology mapping and evaluate effectivemodelsSet monitoring targets and detection accuracy requirements
System Study: System study for results of technology investigation
End of FY 2018: System Outline Review and Development Plan Creation
Technical Investigation: Create technology mapping and evaluate effectivemodelsSet monitoring targets and detection accuracy requirements
System Study: System study for results of technology investigation* Development plans are created for respective issues as necessary.

* This section corresponds to the following items of “II. Objective of Research”: Both gas/liquid phases are described
together.
(3) (i) Conceptsual Study and Development Planning of Detection Technologies and Systems for α Nuclides in Gas Phase(3) (ii) Conceptsual Study and Development Planning of Detection Technologies and Systems for α Nuclides in Liquid Phase©International Research Institute for Nuclear Decommissioning

52

VI. Implementation Details(3) Studying α Nuclide Monitoring System for Fuel Debris Retrieval1) α Nuclide Monitoring Overview
A fuel debris retrieval process will be carried out by monitoring various plant parameters to confirm
they are within the normal range.
The monitoring of radioactive materials is part of this process and monitoring targets are specified
depending on the purposes (α, β, γ, and neutron fluxes, for example). For reasons shown below, it isrequired to consider the applicability of existing α nuclide monitoring technologies (i.e. toconfiemwhether new items should be developed).
• Since nuclear fuel materials are processed and then retrieved in a fuel debris retrieval process, asignificant amount of α nuclides (whose impact of internal exposure is extremely large)
including Pu is expected to be dispersed as well as FPs (fission products). Therefore, it is
crucial to monitor α nuclides.
• FP monitoring technologies have been well established in nuclear facilities (despite someissues including that their installation locations are high radiation areas).
• Although there are some cases where α nuclide monitoring is applied in the reprocessing and fuelprocessing facilities, the situation revolving around fuel debris retrieval is substantiallydifferent from that in the existing facilities.

Debris retrieval is a step-by-step process, and the system is reviewed in the following steps.
Similarly, in the α nuclide monitoring, measurement ranges are reviewed in response to the amountretrieved and the know-hows obtained are reflected as necessary.

©International Research Institute for Nuclear Decommissioning

53

VI. Implementation Details(3) Studying α Nuclide Monitoring System for Fuel Debris Retrieval
2) Study Items
Item

Study Items

Clarifying Purposes for Monitoring α
NuclidesSort out the measurement purposes since the monitoring
location and measurement range vary depending on the
purpose.

Provisional Setting of α Nuclide
Monitoring Positions

Monitoring locations vary depending on the purposes andthe estimated concentration is different at each monitoring
location. Provisional monitoring locations are set to review
the measurement range.

Studying Measurement Range

The required measurement range is reviewed for eachprovisional monitoring location.

Researching on and Clarifying
Specifications of Existing α Nuclide
Monitors

Existing α nuclide monitors are surveyed and their
specifications are sorted out to review their compatibility.

Reviewing the Applicability of Existing α
Nuclide Monitors and Identifying Issues

Based on the results of researching on and clarifying
specifications of existing α nuclide monitors, thecompatibility of existing technologies is reviewed in terms ofthe measurement range, etc. and issues are identified.

Reviewing Alternatives in Case of
Incompatibility (Necessity of System
Modification or Development)

When it is hard to solve issues related to the compatibility ofexisting α nuclide monitors, system modifications arereviewed, development elements are sorted out, anddevelopment plans are createdas necessary.
©International Research Institute for Nuclear Decommissioning

54

VI. Implementation Details(3) Studying α Nuclide Monitoring System for Fuel Debris Retrieval
3) α Nuclide Monitoring Review Process Flow
The α nuclide monitoring review proceeds based on the flow shown below. For the priority of review
items, the gas system takes precedence because it has a greater impact when emitted to theenvironment and breathed in by personnel (i.e. internal exposure).

Scope of Report
Clarifying Purposes of Monitoring

Provisional Setting of Gas System Diagram
Monitoring Location

Reviewing Measurement Range for Monitoring

Provisional Setting of Liquid System
Diagram Monitoring Positions

Researching on and ClarifyingSpecifications of Existing α
Nuclide Monitors

Reviewing the Applicability of Existing α Nuclide Monitors and Identifying Issues
System Modification

Reviewing Alternatives in Case of Incompatibility (Necessity of System Modification or Development)©International Research Institute for Nuclear Decommissioning

55

VI. Implementation Details(3) Studying α Nuclide Monitoring System for Fuel Debris Retrieval
4) Purposes for Monitoring α Nuclides and Monitoring Positions

The targets of protection are divided into “Impact on the General Public (Outside of Perimeter)” and“Impact on Workers.” The monitoring purposes are classified into “Operation Monitoring (Monitoring ofConcentration Changes inside PCV during Retrieval),” “Emission Monitoring (Emission Control),” and“Leak Detection.”
Item

Radiation Protection
I. Impact on the General Public (Outside of
II. Impact on Workers
Perimeter)
Under Normal ⚫ Emission control is guaranteed withGas
⚫ There are leaks within the building under the
Operation
Systemcontinuous monitoring (Emission
normal operation conditions. Workers outside
Monitoring).
the building are included in Category I.
In⚫ The amount of α nuclide emission is monitors ⚫ Abnormalities including leaks are detected
Emergencies
at the secondary boundary (Emission
early (to evacuate workers in the building)
Monitoring).
(Leak Detection).
⚫ Monitoring the α nuclide concentration inside ⚫ Monitoring the α nuclide concentration inside
the PCV (primary boundary) enables early
the PCV (primary boundary) enables early
detection of abnormalities (Operation
detection of abnormalities (Operation
Monitoring).
Monitoring).

Also, the measurement ranges were reviewed assuming the following measurement locations suitable for eachpurpose:Operation Monitoring: (i) A location where the atmosphere inside the PCV can be monitored
Emission Monitoring: (ii) A location where the amount of emission from the exhaust end can be monitored
Leak Detection: (iii) A location where leaks from the primary boundary can be detected©International Research Institute for Nuclear Decommissioning

56

VI. Implementation Details(3) Studying α Nuclide Monitoring System for Fuel Debris Retrieval5) Measurement Range Requirements

In reviewing the measurement range, it is necessary to comprehensively determine the upper limit (αradioactivity concentration expected in the operation range) and the lower limit (requirements of the laws
and regulations, monitoring criteria, etc.) of the measurement range required for monitoring. To this end,
concentrations to be measured were reviewed by dividing them into the following categories.

•

Estimated Radioactivity Concentration in the Design
Set based on the evaluations of the atmosphere inside the PCV and radioactivity concentration
at exhaust outlets under the assumption of full-scale debris retrieval.

•

Limits of Concentration in the Air as Stipulated in Laws and Regulations
Set based on the upper concentration limits stipulated in laws and regulations concerning the
air outside the supervised area and the respiration of radiation workers.

•

Monitoring Criteria
Set based on the measurement guidelines for released radioactive materials, the measurement
guidelines for radiation under emergency operating conditions, and the guidelines for radiation
monitoring (JEAG4606-2017).

•

Current Background/Action Levels

Set based on the target lower limit of detection and action level set in the current R/B dust
sampling process.
Measurement range requirements were specified for each monitoring location based on the above
review results.

©International Research Institute for Nuclear Decommissioning

VI. Implementation Details

57(3) Studying α Nuclide Monitoring System for Fuel Debris Retrieval
6) Summary➢ In FY 2017, mainly in the gas system, the purposes of α nuclide monitoring, themeasurement range, have been reviewed, and existing α nuclide monitors identified,their specifications surveyed, and their compatibility reviewed.
➢ In FY 2018, the liquid system will mainly be reviewed, and, if issues are found inapplying existing α nuclide monitoring technologies, alternatives reviewed.
Item
Clarifying Purposes
Setting Various Conditions for Review(Required Measurement Range)
Researching on and Clarifying Specificationsof Existing α Nuclide Monitors
Reviewing the Applicability of α Nuclide
Monitors in the Gas System

Reviewing the Applicability of α Nuclide
Monitors in the Liquid System

FY 2017

FY 2018
Liquid System

Gas System

Liquid System

Gas System

Gas System

Liquid System

Gas System

Liquid System

Summary (Reviewing Alternatives and theNeed for Development)©International Research Institute for Nuclear Decommissioning

VI.
(4) Study on Optimization of Ensuring Safety of Methods and Systems
4. Progress in Project Implementation

58(i) Study on Optimization of Ensuring Safety of Methods
1) Review of Method Design Conditions
The design conditions required to review fuel debris retrieval methods were sorted out and optimized.
Other Projects
Safety Review

Safety Requirements

System Study

Functional Requirements

As part of the “Study on Optimization of Ensuring Safety of
Methods and Systems,” conditions required for reviewing fueldebris retrieval methods were sorted out and assumptions forstandardized design conditions were made for items for which no
input had been obtained.

1. Properties and Distributions of Fuel
Debris
2. Results of Leak Blocking Feasibility
Review
3. Container Size
4. On-Site Survey Results, etc.

TEPCO HD
1. Site Status
2. Floor Loading and Seismic
Conditions
3. Restrictions on Layout
4. State of Building Damage, etc.

Methods were reviewed based on the optimized common
design conditions.
: Scope to Be: Input and Output
Reviewed in Method
Review©International Research Institute for Nuclear Decommissioning

VI. (4) Study on Optimization of Ensuring Safety of Methods and Systems

59(i) Study on Optimization of Ensuring Safety of Methods2) Identifying and Taking Measures against Issues Common to All Methods(i) Floor Loading Limit
An action policy to deal with the floor loading limit on the first floor of the R/B, an issue common to all side access methods
was developed .
PLAN-A

PLAN-B

PLAN-C

Layout Example for Unit 2

Layout Example for Unit 1
Cask

Carry-in Crane

Layout Example for Unit 2

Equipment
Transport Carriage

Extension
Building

Equipment Hatch Cell

Equipment
Cell

Maintenance Cell

Opening on the R/B Wall

R/B WallFuel Debris Retrieval Cell

Cell Conveyor RailPCV WallCarrying in/out of
Other Materials
than Fuel Debris

Storage
Canister

Waste Transport
Carriage*

Pedestal

Waste Transport
Cell

BSW
Mini-Cask System* BSW on the outside the of PCV

Cell Weight in
R/B

Floor
Loading

Floor Loading
Capacity

Cell Weight in
R/B

Floor
Loading

Floor Loading
Capacity

Cell Weight in
R/B

Floor
Loading

Floor Loading
Capacity

Weight Reduction
under Consideration≤ 4.9 ton/m2

4.9 ton/m2

Weight Reduction
under Consideration

0 ton/m2

4.88 ton/m2

Weight Reduction
under Consideration≤ 7 ton/m2

4.9 ton/m2

•
•
•
•
•

This plan is based on the idea to lay out all cells straight and construct a
relatively large opening in the outer wall of the R/B.
The cells are carried in and installed via conveyor rails from outside the
R/B.
The reinforcement of the opening needs to be considered to maintain the
integrity of the R/B (since the opening imposes a relatively large load on
the R/B).
A reduction in floor loading is under consideration by using a suspensionbridge type structure that can release the load to the outside.
This method supports the cells' load at both ends by the BSW and support
point on the outside of the R/B.

• A method is under consideration to connect an extension building built
outside the R/B and the PCV with an access tunnel.
• Our plan is to support the weight of the access tunnel at both ends by
the BSW and the R/B walls so that no load is imposed on the first floorof the R/B.

• Cells and a transport carriage etc. are positioned on the first floor of the
R/B.
• Equipment requiring maintenance and fuel debris are transferred by the
carriage to the external extension building.
• A reduction in floor loading is under consideration by transferring theload of the equipment cell and carriage to the large beams, the BSW, andthe R/B walls. Our plan is to reduce the floor loading by distributing theload with steel floor plates.

©International Research Institute for Nuclear Decommissioning

VI. (4) Study on Optimization of Ensuring Safety of
Methods and Systems

Concepts: To minimize tasks performed inside
PCV60(i) Study on Optimization of Ensuring Safety of Methods• Reduce Workers’ Exposure• Improve Maintainability of Remote
Equipment

3) Reviewing Side Access Methods(i) PLAN-A: Flow Chart(Fuel Debris: Equivalent of about 15 kg, estimated filling rate at
0.3)

Unit Canister
Storage Canister

A Group of 4 Unit Cans

Cask

A Group of 5 Canisters

A group of 5
A group of 4

(Fuel Debris: Equivalent of about 60 kg)(Fuel Debris: Equivalent of about 300 kg)

Unit Canister

Storage
Canister

Cask

Extension Building(iii) Carrying In/Out Cell

Cell (Nitrogen Atmosphere)
Flow of Debris

Equipment (Robot Arm, etc.)

Flow of Debris (in the Water)
Flow of Equipment

Waste

High Contamination Area(ii) Maintenance Cell

Medium Contamination Area
Low Contamination Area
(iv) Storage Canister Cell(i) Fuel Debris Retrieval Cell

Unit Canister

Double Door System(v) Cask Cell
Storage
Canister

PCV Water Level

Mini-Cask System

Robot Arm

Unit Canister©International Research Institute for Nuclear Decommissioning

VI. (4) Study on Optimization of Ensuring Safety of Methods and Systems

61(i) Study on Optimization of Ensuring Safety of Methods
3) Reviewing Side Access Methods(i) PLAN-A: Step Diagram(Fuel Debris Retrieval Tasks/ Fuel Debris Retrieval Tasks Inside Pedestal (Robot Arm, Access Rail))
1. Carry the robot arm into the cell.

2. Insert the robot arm into the access rail.

3. Mount the robot arm on the access rail.

4. Tilt the access rail toward the opening for
CRD replacement.

5. Extend the access rail.

6. Move forward and expand the robot arm.

7. Access the fuel debris with the robot arm.

8. Cut the fuel debris with a tool attached to
the front edge of the arm.

9. Collect fuel debris fragments in a unit canister
placed in the transport carriage on the access rail.

10. Transfer the unit canister to the cell using thetransport carriage on the rail.

11. Access the unit canister with a manipulator in
the cell.

12. Store fuel debris contained in the unit canister in astorage canister with the manipulator in the cell.

©International Research Institute for Nuclear Decommissioning

VI. (4) Study on Optimization of Ensuring Safety of Methods and Systems
Concepts of PLAN-B(i) Study on Optimization of Ensuring Safety of Methods
3) Reviewing Side Access Methods➢ A method applicable to all units
by using an access tunnel.

(ii) PLAN-B: Flow and Area Classification Diagrams
Near the Pedestal Opening

Pedestal
Platform➢ High degree of freedom in layout

Access Tunnel

Near the Equipment Hatch

Pump

Suctionthrough access tunnel routing.

Red➢ Utilizes the existing equipment

Suction (Fuel Debris + Water)

SuctionTightly
Closedhatch. (Minimizes load (including

Tightly Close UC

Transport System (e.g. Carriage or Conveyor)

Muscle Robot

Cutting

Handling Device

floor loading) on damaged R/B)
(Applicable even for an opening

Near the Pedestal Opening•

Image of Chisel Cutting
and Suction

Collect the UC by
Hoisting(Fuel Debris)

Retrieving Debris Inside the Pedestal• Install a platform inside the pedestal.
• Collect fuel debris by grabbing various tools withthe arm traversing on the rail.
• Cut the fuel debris using a tool such as a chiselon the arm tip and suck in the debris.
• For larger fuel debris that cannot be suctioned,
put the UC into the basement of the pedestaland collect it with a grapple.

62

Load the UC onto the Transport
System with the Muscle Robot.

larger than X-6 penetration.)

Platform

Retrieving Debris Outside the Pedestal• Install a platform at the jet deflector.
• Collect fuel debris by grabbing tools grabbed withthe arm mounted on the platform.
• Process the fuel debris using a tool such as achisel on the arm tip and suction the debris.
• For larger debris that cannot be suctioned, put the
UC into the basement and collect it with a grapple.

➢ A retrieval device approaches andNear the Equipment Hatch• Close the lid of the UC with the handling device (tightly
closed).
• Grasp the UC with the robot arm and load it from the transportsystem to the transport container.
• Close the lid of the transport container using the handlingdevice (tightly closed).
* The transport container is used for improved efficiency bytransporting multiple UCs at a time.

retrieves fuel debris.

Feasibility Verification by Fundamental
Technology Development
Inside R/B

Cask
Near the Equipment Hatch

Access Tunnel

Extension Building

Fuel Debris Retrieval Cell

Canister Seal Cell

Contamination Inspection Cell

Storage Canister
Green
Green

Unit Canister
Red

Red

Yellow

Red
Tightly
ClosedTransport Container• Dry As Necessary• Load onto Storage Canister[Legends]• High Contamination (Red)• Low Contamination (Yellow)• Almost No Contamination(Green): Points where Airtightness is Ensured

Access Tunnel• Inside the access tunnel, transport containers aretransferred on a belt conveyor system or by a similarmeans.
• Since the access tunnel is installed so that it does
not contact the surface of the first floor of the R/B, noload is added on the floor. (Supported at both ends
by R/B wall and BSW.)

Fuel Debris Retrieval Cell
• Open the lid of the transport container with the hoist
and unload the UC.
• Dry UCs as necessary.
• Load the UC onto a storage canister with the hoist.
• Tightly close the storage canister loaded with UCs.

Sealed• Seal• Load onto Cask
• Inspect for
Contamination

Canister Seal Cell
• Seal the lid of thecanister.
• Test the seal.

•

Close the Secondary
Lid

Contamination Inspection Cell
• Load the storage canister into a cask.
• Transfer the cask once its
contamination inspection iscompleted.

©International Research Institute for Nuclear Decommissioning

VI. (4) Study on Optimization of Ensuring Safety of Methods and Systems

63(i) Study on Optimization of Ensuring Safety of Methods
3) Reviewing Side Access Methods(ii) PLAN-B: Step Diagram (Preparation of PCV Interior/Removal of Fuel Debris Inside/Outside
Pedestal/Handing Over to Storage Canister)
Task Steps

Carry In Retrieval Equipment

Install Retrieval Equipment (i)Install Retrieval Equipment (ii)

Retrieval of Fuel Debris(Obstacles) Inside Pedestal(Grabbing)RemoveStep Diagram

Collect

Carry In Portal Winch

Task Steps

Example of Retrieval for Fuel
Debris Inside Pedestal(Cutting and Suction)

Install Rotary
Base and RailInstall Arm

Retrieval of Fuel Debris
Outside Pedestal (Grabbing)UC

Retrieval of Fuel Debris
Outside Pedestal (Suction)

Fuel Debris Transfer (i) (Using
Transport System)

Collector(e.g. Pump)

Collector
Retrieve Fuel Debris

Step Diagram

Collect
Opening of
Grating
Grab the HoseUC

SuctionUC
SuctionRetrieve Fuel
DebrisUC
Retrieve Fuel Debris

Collector©International Research Institute for Nuclear Decommissioning

VI. (4) Study on Optimization of Ensuring Safety of Methods and Systems

64(i) Study on Optimization of Ensuring Safety of Methods
3) Reviewing Side Access Methods(ii) PLAN-B: Step Diagram (Preparation of PCV Interior/Removal of Fuel Debris Inside/Outside
Pedestal/Handing Over to Storage Canister)An element test is being planned to verify obstacle removal feasibility.

Step Diagram

Task Steps(from Equipment Hatch to Access Tunnel)

Fuel Debris Transfer (iii)(Loading onto Storage Canister)

Equipment
Hatch

Extension Building: Fuel Debris Retrieval Cell

Fuel Debris Transfer (ii)

Access Tunnel

Fuel Debris Transfer (iv)
(Transporting Storage
Canisters)
Extension Building:Canister Seal Cell

Fuel Debris Transfer (v)(Loading onto Cask and Carrying-Out)
Extension Building: Contamination
Inspection Cell

From Access Tunnel

Load• Load onto a transport container.
• Close the lid (tightly closed).

Uplifted

Carry
Out

Seal

Open the Lid

UC
Storage Canister

Cask

Debris Transport Route

Cask

Seal and Contamination
Inspection* As a mechanism for transporting debris between
boundaries, double doors and air locks are being
considered.

Storage
Canister©International Research Institute for Nuclear Decommissioning

VI. (4) Study on Optimization of Ensuring Safety of Methods and Systems

65(i) Study on Optimization of Ensuring Safety of Methods
Concepts of PLAN-C

3) Reviewing Side Access Methods⚫

(iii) PLAN-C: Appearance
Equipment Cell⚫

Equipment Transport
Carriage⚫
Waste Transport Carriage
Biological Shielding Wall (BSW)

Mimize the area that requires obstacle removal.
➢ No major obstacles (e.g. larger size piping)on its access route inside PCV➢ No new openings required on R/B
Separate Cells and Traffic Lines for Each
FunctionHigh Degree of Freedom in Determining Layout
for Extension Buildings➢ Waste is transported using a wastetransport carriage.

PCV

New Opening

Seal between BSW and PCV

X-6 Penetration

Equipment CarryingIn System

Waste Carrying-Out
SystemPedestalPedestal Opening

Fuel Debris©International Research Institute for Nuclear Decommissioning

VI. (4) Study on Optimization of Ensuring Safety of Methods and Systems

66(i) Study on Optimization of Ensuring Safety of Methods
3) Reviewing Side Access Methods(iii) PLAN-C: Flow and Area Classification Diagrams: Points where
airtightness is ensured

Filter
Water to Minor Circulation System

Filter Units Are Collected into a Transport Cask as Fuel Debris

Waste Transport Cell

Waste Transport
Carriage

Waste Transport Carriage

The waste transport carriage is used to transfer unit
canisters to the extension building outside the truck bay
door.

Waste Transport Carriage

Transfer Equipment

X-6 Penetration

Unit Canister Transport Device

Unit Canister(Everything Including Fuel Debris Is Stored in a Lump)

Waste Transport
Carriage

Suction Equipment

Extension Building

Container Handling Cell

Extension
Building

Waste Transport
Carriage

Fuel Debris[Process Flow Overview]

Reactor
Building

Extension
Building
Extension Building

Overhead Crane(with a Lifting Tool for Transport Cask)
Storage Canister Transporting and
Handling Cell

Storage Canister Transport Crane

Storage Canister Transport Crane(Lifting Hook Type)(with a Lifting Tool for Storage Canister)

Fuel Debris Canister

Container Handling Cell

SealedContainer Transport Crane

Transfer Equipment

Waste Treatment and Inspection Cell

Tightly
ClosedStored in a
Cask

Transport Cask

Trailer for Transporting Transport Casks

Storage Canister Transport Crane

Container Transport Crane
Manipulator

Storage Canister Transport
Container

Transport Cask Carriage(For Supplying Empty Canisters)
Fuel Debris
Solid Waste

Stores in a Storage
Canister

Extension
Building

Storage Canister Handling and Inspection Cell

(For Drying, (Temporary) Lid Welding, Contamination Inspection, and Measurement etc.)©International Research Institute for Nuclear Decommissioning

VI. (4) Study on Optimization of Ensuring Safety of Methods and Systems 67(i) Study on Optimization of Ensuring Safety of Methods
3) Reviewing Side Access Methods(iii) PLAN-C: Step Diagram (Fuel Debris Retrieval/ Removing Structures and Fuel Debris in and outside Pedestal )Carrying Manipulator for Fuel
Debris Collection into
Equipment Cell 1

Manipulator
Transport Device

Collecting Structures and Fuel
Debris Inside RPV Pedestal (i)-1

Collecting Structures and Fuel
Debris Inside RPV Pedestal (i)-2Long-Arm
Manipulator

Short-Arm
Manipulator

Manipulator

Unit
Canister

Fuel Debris

Collecting Structures and Fuel
Debris Inside RPV Pedestal (ii)

Pedestal
BottomManipulator

Step Diagram

Task Steps

Carrying Manipulator for Fuel
Debris Collection into
Equipment Cell 2

Manipulator
for Fuel
DebrisCollection

Step Diagram

Task Steps

CrawlerType
Manipula
tor©International Research Institute for Nuclear Decommissioning

VI. (4) Study on Optimization of Ensuring Safety of Methods and Systems

68(ii) Study on Optimization of Ensuring Safety of Systems
Safety Design➢ For the “Study on System Optimization,” one of the implementation items ofthis project, conditions to be revisited or added are under review starting fromthe upstream.
➢ For the safety design, the functional requirements were reviewed as basic
specifications and important monitoring parameters identified.
➢ For the system design, the degree of conformance of system configurations
and functions to the reviewed functional requirements was confirm ed. Also,
system review conditions (especially, for reviews for action policies that deal
with prerequisites with a greater level of uncertainty) were sorted out.

Nuclear Safety

Nuclear Power Principles(To Be Achieved)

Safety Requirements
Reported in Progress
ReportCriteria

System Design
Reflected

Setting System Configurations andFunctions

Setting Functional Requirements

Identifying Important
Monitoring Parameters

Reflected

Setting System Specifications...

• Confirm the degree ofconformance (excess/deficiency)of the system to the reviewed
functional requirements.
• Set target control values for themonitoring parameters.
• Select components, review thelayout, etc.
©International Research Institute for Nuclear Decommissioning

VI. (4) Study on Optimization of Ensuring Safety of Methods and Systems(ii) Study on Optimization of Ensuring Safety of Systems

69

Improved System Conceptsual Diagram(a) Brushing Up System Concepts
The system for optimization has been reviewed based on the review conducted last year. The
figure below shows the flow of the review.
Main Function
Risk Potential 1

Specific
Measure 1

Functional
Requirement 1

Specific
Measure 2

Functional
Requirement 2

Level 1

Sub-Function
Risk Potential 2

System Conceptsual Diagram(Based on Last Year’s Review)

Level 1
Risk Potential 3

SafetyRequirements

Level 3
Level 2

Specific
Measure 3

Functional
Requirement 3

Specific
Measure 4

Functional
Requirement 4

Specific
Measure 5

Functional
Requirement 5

Specific
Measures 6

Function
Requirem
ent 6

Functional
Requirements 1, 2,
and 3

Level 2
Risk Potential 4

Risk Potential 5

Issue 1

Issue 2Mechanism 1

Mechanism 2

Countermeasure 1

Countermeasure 2

Level 3
Risk Potential 6

Fuel Debris Retrieval Method
Target Performance

Improved System Conceptsual Diagram(Rev1)

Functional
Requirements

Design Considerations to Maintain Safety Functions(e.g. Reliability and Maintainability)
Figure - Breaking Down Safety Requirements into Practical Design©International Research Institute for Nuclear Decommissioning

VI. (4) Study on Optimization of Ensuring Safety of Methods and Systems

70(ii) Study on Optimization of Ensuring Safety of Systems(a) Brushing Up System Concepts
1) Revisiting the Safety Requirements (1/2)

This year, the safety requirements were revisited in terms of the following aspects:•

To clearly identify items to be achieved (e.g., safety standards) in defining thesafety requirements for a fuel debris retrieval facility in a specified nuclear facility
for nuclear safety purposes.

•

To add requirements for protecting workers from radioactive risks, as workers play
an integral role in fuel debris retrieval tasks in a specified nuclear facility, andradiation protection measures taken for the environment in which workers performsystem maintenance and inspection tasks have an impact on the system’s
feasibility.
To prevent combustion and explosions caused by flammable gas and metallic
powder as safety requirements, taking into account the characteristics of a
specified nuclear facility.

•(The safety requirements set this year are shown in the following pages.)©International Research Institute for Nuclear Decommissioning

VI. (4) Study on Optimization of Ensuring Safety of Methods and Systems

71(ii) Study on Optimization of Ensuring Safety of Systems(a) Brushing Up System Concepts
1) Revisiting the Safety Requirements (2/2)
Nuclear Safety

Safety Principles (To Be Achieved)

Basic Safety Requirements

Safety Requirements (Example)
Prevent leakage that exceeds the allowable level specified in thesafety standards for radioactive materials in gas

Confine radioactive materials
by setting a boundary
Prevent leakage that exceeds the allowable level specified in thesafety standards for radioactive materials in liquid system

Protect People and the Environment from Radioactive Risks

Confine Radioactive
Materials

Protect the Public
and theEnvironment fromRadioactive Risks

Prevent Excessive
Emission ofRadioactive Materials

Prevent Abnormal
Generation of
Additional Radioactive
Materials

Prevent Excessive Radioactive Exposure

Protect Workers
from Radioactive
Risks

Prevent Workers from Excessive External andInternal Exposures- Exposure Associated with Installing New
Equipment Required for Debris Retrieval Tasks- Exposure Associated with Debris Retrieval
Related Tasks- Exposure of Site Workers Due to Tasks Other
than Debris Retrieval Related Tasks

Confine radioactive materials
retrieved from within thereactor with transport
containers

Prevent leakage of radioactive materials from transport containers

Prevent additional nuclear
fission reactions

Prevention of abnormal generation of radioactive materials caused by
criticality

Prevent abnormal overheating

Prevention of the emission of radioactive materials due to abnormal
temperature rise in fuel debris

Prevent abnormal diffusion ofradioactive materials caused
by cutting operation

Prevention of abnormal diffusion of radioactive materials caused by
cutting fuel debris and structuresProtect against external
exposure

Shields for preventing excessive direct radiation exposure

Design for dose reduction forworkers

Shields, appropriate classifications for the level of contamination anddose, and system designs for remote maintenance and traffic line
setting, etc. to reduce exposure

Operation control for dose
reduction for workers

Operation methods, maintenance plans, and task management fordose reduction©International Research Institute for Nuclear Decommissioning

VI. (4) Study on Optimization of Ensuring Safety of Methods and Systems

72(ii) Study on Optimization of Ensuring Safety of Systems(a) Brushing Up System Concepts

2) Revisiting the Functional Requirements (1/3)➢ Systematically organized functional requirements to respond potential risks for eachsafety requirements.
➢ Functional requirements were specified for each level of defense in depth.
Requirements were clearly stated for cases that assume the loss of a function at theprevious stage, as they are an important prerequisite for the system design.
➢ As design conditions were not yet finalized for explosions caused by flammable gas
and metallic power, multiple functional requirements were proposed.
(The functional requirements set this year are shown in the following pages.)©International Research Institute for Nuclear Decommissioning

VI. (4) Study on Optimization of Ensuring Safety of Methods and Systems

73(ii) Study on Optimization of Ensuring Safety of Systems(a) Brushing Up System Concepts
2) Revisiting the Functional Requirements (2/3)
Safety Requirements

Level

Functional Requirements (Tentative)
Reduce the radioactive material concentration in the gas phase within the boundary to a value equal to or less than the control standard
value

Levels
1and2

Prevent radioactive material leakage in the gas phase using a static boundary except in areas that depend on a dynamic boundary
Prevent radioactive material leakage in the gas phase that exceeds the allowable level specified in the safety standards using a dynamic
boundary
Prevent the emission of radioactive materials in the gas phase to the environment that exceeds the allowable level specified in thesafety standards in the exhaust to maintain a dynamic boundary

Prevent leakage that exceeds theallowable level specified in the safety
standards for radioactive materials ingasCapable of isolating the boundary (along isolatable emission routes) when needed (including in the case of criticality accidents and theloss of the debris cooldown function)

Level 3

Prevent radioactive material leakage in the gas phase using a static boundary except in areas that depend on a dynamic boundary
under emergency operating conditions
Prevent radioactive material leakage in the gas phase that exceeds the allowable level specified in the safety standards using a dynamic
boundary under emergency operating conditions
Prevent the emission of radioactive materials in the gas phase to the environment that exceeds the allowable level specified in thesafety standards in the exhaust to maintain a dynamic boundary under emergency operating conditions

Prevent leakage that exceeds theallowable level specified in the safety Levels
standards for radioactive materials in 1and2
liquid system

Prevent radioactive material leakage in the liquid phase using a static boundary in combination with the function to reduce theconcentrations of radioactive materials in the liquid phase within the boundary to maintain the radioactivity concentrationin the liquid
phase in the torus room to a value equal to or less than the control standard value
Reduce the radioactive material concentration in the liquid phase within the boundary to a value equal to or less than the control
standard value
Prevent radioactive material leakage in the liquid phase from the boundary through the opening in the gas phase to the torus room using
a dynamic boundary

Prevent leakage that exceeds theLevelsallowable level specified in the safety 1and2
standards for radioactive materials in
Level 3liquid system
Prevent abnormal generation ofradioactive materials caused by
nuclear fission reactions

Prevent radioactive material leakage in the liquid phase from the torus room to the environment using the dynamic boundary
Prevent radioactive material leakage in the liquid phase from the torus room to the environment using the dynamic boundary

Levels1and2

Maintain sub-criticality

Level 3

Terminal the state of re-criticality of debris promptly when an accident occurs©International Research Institute for Nuclear Decommissioning

VI. (4) Study on Optimization of Ensuring Safety of Methods and Systems

74(ii) Study on Optimization of Ensuring Safety of Systems(a) Brushing Up System Concepts
2) Revisiting the Functional Requirements (3/3)
Safety Requirements

Level

Functional Requirements (Tentative)

Level 1Cool down the debris so that the monitored value of temperature in the boundary does not rise abnormally

Prevention of the emission ofradioactive materials due toabnormal temperature rise in fueldebrisLevel 2Cool down the debris so that, by the temperature rise in the debris, the concentrations of radioactive materials in the gas phase in
the boundary becomes equal to or less than the control value set for a transition period

Level 3Cool down the debris so that, by the temperature rise in the debris, the concentrations of radioactive materials in the gas phase in
the boundary becomes equal to or less than the control value set for emergency operating conditions

Prevention of abnormal diffusion ofradioactive materials caused by
cutting fuel debris and structures

Levels
1and2

Cut the debris and structures in a manner that makes the concentrations of radioactive materials within the boundary equal to orless than the control standard value with a help of the functions to reduce the concentration of radioactive materials in the gas
and liquid phases within the boundary

Shields, appropriate classifications Levels
for the level of contamination and
1and2
dose, and system designs forremote maintenance and traffic line Level 3
setting, etc. to reduce exposure
Operation methods, maintenanceplans, and task management fordose reduction

Maintain conditions under which
fire is not caused by reactions
between metallic powder andoxygenSet appropriate classifications for the level of dose and contamination under emergency operating conditions and design thesystem accordingly

Levels1and2

Develop operation methods and maintenance plans so that the exposure level is equal to or below the safety standards, andmanage tasks accordingly under normal operating conditions

Level 3

Establish measures against accidents so that the exposure level is equal to or below the safety standards, and manage tasks
accordingly

Level 1

Reduce the oxygen concentration to a level equal to or below the control standard value

Level 2

Capable of suppressing the generation of metallic powder in the event the oxygen concentration has exceeded the control
standard value

Level 3Capable of reducing the concentration of metallic powder within the boundary in the event of a rapid rise in the oxygen
concentration

Levels
Maintain flammable gas equal to or 1and2
below its flammability limit toprevent fire and explosions
Level 3
Monitor the plant to understand its
state

Set appropriate classifications for the level of dose and contamination and design the system accordingly

Reduce the oxygen concentration to a level equal to or below the control standard value
Maintain the hydrogen concentration equal to or below the control standard value in the event the oxygen concentration has
exceeded the control standard value

Levels 1–3

Have monitoring functions in place to understand the plant state

Levels 1–3

Have monitoring functions in place to control radiation emission to the environment©International Research Institute for Nuclear Decommissioning

VI. (4) Study on Optimization of Ensuring Safety of Methods and Systems

75(ii) Study on Optimization of Ensuring Safety of Systems(a) Brushing Up System Concepts
3) Clearly Identifying Requirements Using Objective Trees
From Nuclear Safety
Nuclear Safety

Safety Principles (To Be Achieved)

Basic Safety Requirements

Safety Requirements (Example)

Objective Trees

Protect People and the Environment from Radioactive Risks

Prevent leakage that exceeds the allowable level specified in thesafety standards for radioactive materials in gas
Confine radioactive materials by
setting a boundary
Confine Radioactive
Materials

SafetyRequirements
Protect the Public
and theEnvironment fromRadioactive Risks

Prevent Excessive
Emission of Radioactive
Materials

Protect Workers
from Radioactive
Risks

Prevent Workers from Excessive External andInternal Exposures- Exposure Associated with Installing New
Equipment Required for Debris Retrieval Tasks- Exposure Associated with Debris Retrieval
Related Tasks- Exposure of Site Workers Due to Tasks Other
than Debris Retrieval Related Tasks

Level 2
Level 1

Confine radioactive materials
retrieved from within the reactor
with transport containers

Prevent leakage of radioactive materials from transport containers

Prevent additional nuclear
fission reactions

Prevent abnormal generation of radioactive materials caused by
nuclear reactions

Prevent Abnormal
Prevent abnormal overheating
Generation of Additional
Radioactive Materials

Prevent Excessive Radioactive Exposure

Level 3
Prevent leakage that exceeds the allowable level specified in thesafety standards for radioactive materials in liquid system

Prevent leakage that exceeds the allowable levelspecified in the safety standards for radioactive
materials in gas

Prevention of the emission of radioactive materials due to abnormal
temperature rise in fuel debris

Prevent abnormal diffusion ofradioactive materials caused by
cutting operation

Prevention of abnormal diffusion of radioactive materials caused by
cutting fuel debris and structuresProtect against external
exposure

Shields for preventing excessive direct radiation exposure

Design for dose reduction forworkers

Shields, appropriate classifications for the level of contamination anddose, and system designs for remote maintenance and traffic line
setting, etc. to reduce exposure

Operation control for dose
reduction for workers

Operation methods, maintenance plans, and task management fordose reduction

Confinement function using a static boundary

Issue (Does the design
have sufficient reliability?)

Issue (Does the design
allow inspections andmaintenance?)

Function to control emission from a boundary

Issue (Does the design
have sufficient reliability?)

Issue (Does the design
allow inspections andmaintenance?)

Maintain conditions under which fire is not caused byreactions between metallic powder and oxygen

Maintain flammable gas equal to or below its flammability limit toprevent fire and explosions
Monitor the plant to understand its state(Added as necessary)

Functional
Requirements

Countermeasure Considerations
Added to ･ Design considerations for maintaining the safety functions
the Safety
RequiremeType
Design Considerations for Maintaining the Safety Functions
nts AsNecessary
Capable of maintaining functions within expected environmental conditions

Functional Requirements

Prevent radioactive material leakage in the gas phaseusing a static boundary except in areas that depend on a
dynamic boundary
Prevent the emission of radioactive materials in the gas
phase to the environment that exceeds the allowablelevel specified in the safety standards in the exhaust to
maintain a dynamic boundary(The rest is omitted.)

Check whether certain functions and integrity expected of existing facilities
can actually be provided by these facilities
Basic Requirements
to Maintain
FunctionsHave a design that provides a required level of reliability
Have a design that allows necessary inspections and maintenanceCapable of providing necessary monitoring functions

Measures against
Hazards

Capable of providing necessary operability (especially for on-site operations)
Take appropriate measures against internal hazards (including fire,
explosions, and fallen objects)
Take appropriate measures against external hazards (i.e. earthquakes andtsunamis) ©International Research Institute for Nuclear Decommissioning

VI. (4) Study on Optimization of Ensuring Safety of Methods and Systems

76(ii) Study on Optimization of Ensuring Safety of Systems(b) Reviewing Target Control Values
Monitoring parameters and target control values are being reviewed in response to the functional requirement
review.
･ Important parameters were identified in terms of the following three aspects based on the functional
requirements provided by the safety requirements.
(i) Parameters for which the judgement criteria are defined in functional requirements(ii) Parameters for which the judgement criteria are not clearly defined in functional requirements, but
required for quantitatively confirm ing that a functional requirement is met(iii) Parameters which complements (i) and (ii) above• Various settings and conditions values are being reviewed (including target control values, safety analysis
condition values, and action levels) for the identified important parameters.

Action Level
Target Control Value

Safety analysis condition values are set
within this range.

Figure - Relationship among Settings and Levels of Controlled State©International Research Institute for Nuclear Decommissioning

VI. (4) Study on Optimization of Ensuring Safety of Methods and Systems

77(ii) Study on Optimization of Ensuring Safety of Systems(c) Results of Exposure Assessment(i) Exposure Assessment
under Normal Operating
Conditions(ii) Exposure Assessment
under Emergency Operating
Conditions⚫

(iii) Worker Exposure
Assessment

⚫

⚫
⚫

⚫

⚫

Exposure assessment techniques at the site boundary under normal
and emergency operating conditions had been put in place by FY
2016.
Evaluations to confirm feasibility, based on the exposure assessment
for the site boundary under normal and emergency operating
conditions, were conducted in FY 2016.
Re-evaluations in light of changes that arouse from the progress madein the system standardization reviews in FY 2017 were conducted .
Only a simple assessment was conducted in FY 2016 to understandthe tendency in worker exposure, because, for worker exposure, a full
assessment would require more detailed conditions such as layout.
In FY 2017, points of view regarding worker exposure were sorted out,
and the existing nuclear facility was surveyed for settings such asclassifications for the level of dose and contamination required for our
review.
Conditions to be reviewed were sorted out, including plant states atwhich exposure assessments are conducted (level of defense in depth)
and areas accessible to workers, because, for worker exposure,assessments conducted under maintenance as well as normal
operation conditions are important.

Worker exposure assessments are especially important for the feasibility of the retrieval process,therefore worker exposure is assessed with the progress in system standardization and layout study.
©International Research Institute for Nuclear Decommissioning

VI. (4) Study on Optimization of Ensuring Safety of Methods and Systems

78(ii) Study on Optimization of Ensuring Safety of Systems(d) Categories of System Study Prerequisites and Their Standardization Status
The prerequisites in establishing the system have uncertainties. And system specifications and configurations change
depending on the prerequisites (especially the state of the actual installation). However, assumptions for multiple
prerequisites are being made and systems that can meet these prerequisites in advance are being sorted out, so thatsystem based on a standardized point of view can be selected, regardless of methods used, once the prerequisites
are made clear.
System Study Prerequisites

Main Implementation Items Relating to System
Study Prerequisites

Status of Standardization*

Category

Type(i) Basic System Requirements
Safety Requirements

No

-

Yes
(Necessity of the oxygen
concentration limit)• Exposure assessment• Brushing up functional requirements• Reflecting the results of element technology
development

SystemConfigurations

Yes(Presence/absence of recirculation
loops, presence/absence ofmultiplexing emergency systems,
and support for temporary
installation of emergency systems)• Reflecting the results of element technology
development• Reviewing system reliability• Reviewing maintenance policy

Equipment
Specifications

No• Reflecting the results of element technology
development

No• Reflecting the results of element technology
development• Reconfiguring areas to which the system can beallocated

Functional
Requirements(ii) System Specifications(iii) System Layout
Layout Conditions* Items to be determined at the actual design stage are excluded.
©International Research Institute for Nuclear Decommissioning

VI. (4) Study on Optimization of Ensuring Safety of Methods and Systems

79(ii) Study on Optimization of Ensuring Safety of Systems(d) Categories of System Study Prerequisites and Their Standardization Status• Standardization Status: Functional Requirement-Related Matters<Fire and Explosion Prevention: Necessity of the
Oxygen Concentration Limit>

As an example of our standardization items, the following shows where setting prerequisites related to the prevention of fire and explosions are at.

➢Target Hydrogen Concentration
A standardized condition was set that the concentration should be less than the flammable concentration limit (4%). <Standardized Completed>[Supplemental Information]•
If nitrogen is injected under the same conditions as the current ones (in terms of flow rate and injection point) in retrieving the fuel debris, thehydrogen concentration is generally expected to drop to a level lower than the current level. This is because of an additional diluting effect of
the in-leak air caused by negative pressurization.
For this reason, in our review last year, assumptions were made for addressing the hydrogen concentration under the same conditions of RPV
nitrogen injection and PCV scavenging as the current ones.
•
As the locations of hydrogen accumulation are unknown in this project, our plan is to confirm by analysis that nitrogen and in-leak air cansufficiently suppress the hydrogen concentration. Standardized judgement criteria (flow rate and injection point) for this functional requirement
will be set based on the results of this analysis.

➢Target Oxygen Concentration
Since requirements for preventing combustion and explosions of flammable solid substances have not beenclearly identified, multiple prerequisites were prepared. For this reason, multiple system configurations are being
reviewed.
=> “Differences in System Configurations” and “Future Implementation Plans” are shown in the following pages.
Conditions Reviewed Last Year (Hydrogen and Oxygen Concentrations)
SystemConfigurations(See the next page)

System Study Prerequisites

Notes

Plan 1

Hydrogen Concentration: < 4%Oxygen Concentration: Not limited

Nitrogen is injected in an amount required forhydrogen delusion.

Plan 2

Hydrogen Concentration: < 4%Oxygen Concentration: Limited (as low as
possible)

Nitrogen is injected in an amount required foroxygen delusion.
©International
Research
for Nuclear Decommissioning(Increased nitrogenflow rate
than InstitutePlan 1)

VI. (4) Study on Optimization of Ensuring Safety of Methods and Systems

80(ii) Study on Optimization of Ensuring Safety of Systems(d) Categories of System Study Prerequisites and Their Standardization Status

To prevent fire and explosions, localized measures are also expected to be effective as a method for reducing the oxygen concentration. Thus, reviewsin cooperation with the Fundamental Technology PJ will be conducted. Also, the oxygen concentration limit has an impact on corrosion control and theincrease in the amount of nitrogen injected to limit the oxygen concentration has an impact on the monitoring capability for criticality (becomes moredifficult as the amount of exhaust grows larger). Our judgment should take this correlation into account.

Prerequisites(Functional
Requirement)

Plan 1

Plan 2Others(Using a Different Method)

Not Required to Reduce Oxygen Concentration

Required to Reduce Oxygen Concentration

Required to Reduce Oxygen Concentration

Nitrogen is injected as needed near
the locations where the presence ofhydrogen accumulation is expected(as a measure against hydrogen)NitrogenSupplyFacilityImage

A large amount of nitrogen is
injected to dilute the oxygen
concentration in the entire PCV

Nitrogen is injected asneeded near the cutting
pointsNitrogenSupplyFacility

ExhaustPort

ExhaustFan

NitrogenSupplyFacility

ExhaustPort

ExhaustFan
Nitrogen is also injected asneeded near the locations
where the presence ofhydrogen accumulation is
expected

Fill in nitrogen in an amount required for hydrogen dilution inlocations where the presence of hydrogen accumulation is
expected.

Overview

Fill in nitrogen in a large amount (as compared to the in-leakamount) to reduce the oxygen concentration in a wide areaof space in the PCV and prevent explosions of flammablesolid substances.

ExhaustPort

ExhaustFan
Local Collector(Effective for Particle
Dispersion Prevention)

Combine nitrogen injection near the cutting point and a local
collector to prevent a localized drop in the oxygen
concentration + powder dust dispersion and prevent
explosions of flammable solid substances.

(This serves as a measure against hydrogen only.
Explosions of flammable solid substances are not taken into
account.)

Features• Amount of nitrogen to fill: Small (up to 40 m 3/h)*1• Range of area where reduction of oxygen concentration isrequired: None in particular*2• Serves as a measure against hydrogen only
*1 Similar to the current condition.
*2 The in-leak amount may impact the concentration.

• Amount of nitrogen to fill: Large (up to 1000 m 3/h)
• Amount of nitrogen to fill: From small to large (to be• Range of area where reduction of oxygen concentration isreviewed going forward)
required: Entire PCV*3 and 4• Range of area where reduction of oxygen concentration is• Serves also as a measure against hydrogenrequired: Areas near the cutting points*5*3 The oxygen concentration is dependent on the in-leak• Requires separate measures against hydrogenamount.
*5 This assumes a local collector is installed.
©International Research Institute for Nuclear Decommissioning*4 Except for areas near the in-leak points.

VI. (4) Study on Optimization of Ensuring Safety of Methods and Systems

81(ii) Study on Optimization of Ensuring Safety of Systems(d) Categories of System Study Prerequisites and Status of Standardization[Future Implementation Plans]➢ The conditions required to prevent explosions of flammable solid substances will be set.
➢ In case that the reduction of the oxygen concentration is required, countermeasures including localizedmeasures continues to be considered. (=> Need to coordinate with the Fundamental Technology project)➢ Since the oxygen concentration reduction method depends on the in-leak amount as well as the amount of
nitrogen to fill, countermeasures will be reviewed based on the results of element technology development for
confinement (i.e. information on the openings of the actual installation and airflow analysis results [verificationof the effectiveness of hydrogen accumulation prevention]).
➢ As the oxygen concentration affects corrosion control, and increased nitrogen is injected to limit the oxygen
concentration affects the monitoring capability for criticality, an evaluation study for a comprehensive decision
will be conducted.
<System Study Flow for the Necessity of Oxygen Concentration Limit>
Completed
Scope of This ReportCompleted
Set conditions forpreventing
explosions offlammable solid
substances• Set a Target Oxygen
Concentration

Review
Measures• Compare Measures (Plans
1, 2, and Others)

Standardized
System
(FY 2017)• System under Typical
Conditions

Q1–Q3 FY 2018

Revisit
Measures• Sort Out Requirements for the Oxygen Concentration• Reflect the results of Element Technology
Development

Q4 FY 2018

Standardized
System
(FY 2018)• System under Typical
Conditions for Each Unit

©International Research Institute for Nuclear Decommissioning