Subsidy Project of Decommissioning and Contaminated Water Managementin the FY2017 Supplementary Budgets

Development of Technology for Investigation
inside the reactor pressure vessel (RPV)
Final ReportAugust 2020
International Research Institute for Nuclear Decommissioning (IRID)
All Rights Reserved. International Research Institute for Nuclear Decommissioning

無断複製・転載禁止
技術研究組合国際廃炉研究開発機構©International
Research Institutefor Nuclear Decommissioning©International Research Institute for Nuclear Decommissioning

CONTENTS (1/2)

No.1

1. Research background and purposes
2. Project goals
2.1 Roadmap of the top-opening investigation method
2.2 Roadmap of the side-opening investigation method
3. Implementation items, their correlations, and relations with otherresearch
3.1 Implementation items
3.2 Correlations among implementation items
3.3 Relations with other research
4. Schedule
5. Project organization chart©International Research Institute for Nuclear Decommissioning

CONTENTS (2/2)

No.2

6. Implementation details
6.1 Investigation and development planning
6.1.1 Organization of fuel debris retrieval information
6.1.2 Investigation update and development plans
6.2 Investigation method planning
6.2.1 Crystallization of work steps and rationalization of work
procedures
6.2.2 Clarification of safety requirements and exposure assessment
6.3 Study on investigation auxiliary system
6.4 Development of access and investigation equipment
6.4.1 Development of investigation equipment for the top accessmethod
6.4.2 Development of investigation equipment for the side accessmethod
7. Summary©International Research Institute for Nuclear Decommissioning1. Research Background and Purposes

No.3
Top-opening investigation method[Purpose of investigating the inside of the RPV]
Basic information regarding the inside of the reactor pressure vessel(RPV) is obtained toward fuel debris retrieval (fuel debris distribution,dose, conditions of the structures, etc.).

Primary containment
vessel (PCV)[Purpose of the technical development]
Information inside the RPV required for fuel debris retrieval (Investigationneeds) is examined to clarify investigation targets, and technology thatenables the investigation is developed.
[Implementation items conducted in FY2016–2017]
Investigation inside the RPV and technological plans developed until
FY2015 were established and updated, and technological developmentof the side-opening investigation method started. Remote-operated
investigation equipment and system were developed based on theinvestigation and development plans to confirm environmental conditions
including the fuel debris conditions and doses. Equipment to access thereactor core from the top was developed, and an investigation method foraccessing the reactor core was selected. Moreover, work steps for bothof the top-opening and side-opening investigation methods, frompreparations for prior investigation and treatment after investigation, wereplanned for the entire investigation equipment design and the method
planning.

Development of Technology
for Investigation inside the
RPV

Reactor building(R/B)

Reactor pressure
vessel (RPV)
Side-opening
investigation method【Contribution of project achievements】
Because of this project development, actual
investigation can be performed, and the obtained
information that would contribute detailed study ofcriticality control will be provided.

Actualinvestigation
Information on inside the RPV(Visual information, dose rate, etc.)

Study on the method andequipment design for fueldebris retrieval©International Research Institute for Nuclear Decommissioning2. Project goals (FY2018 to FY2019)

No.4

Implementation Items

Goal indicator(1) Investigation and development
Planning

Information required to plan and implement fuel debris retrieval shall have been collected
and organized. An investigation plan shall have been formulated based on a clear
understanding of preconditions for on-site investigation, such as implementation timing. In
addition, the development plan shall have been updated as needed.
(No target is set for technology readiness level (TRL) as it’s an information organizing task)(2) Investigation method planningWork steps, procedures, and safety requirements shall have been made clear and specific.
In addition, the investigation work’s impact on the surrounding environment shall have been
evaluated through exposure assessment based on the clearly defined work steps andprocedures.
(No target is set for technology readiness level (TRL) as it’s an information organizing task)(3) Study of investigation auxiliary
systemThe system’s specifications for investigating and configuring the exposure assessment
systems shall have been studied.
(Target TRL upon completion: Level 2)(4) Development of access andinvestigation equipment① Development of investigationequipment for the top accessmethodThe following shall have been achieved for the top-opening investigation method: drawingsof the devices with specifications, element tests if necessary, and verification of the devices’
on-site applicability based on the correct understanding of the actual site conditions and thedevices’ use conditions.
(Target TRL upon completion: Level 4)② Development of investigationequipment for side accessmethodThe following shall have been achieved for the side-opening investigation method: drawingsof the devices with specifications, element tests if necessary, and verification of the devices’
on-site applicability based on the correct understanding of the actual site conditions and thedevices’ use conditions.
(Target TRL upon completion: Level 4)©International Research Institute for Nuclear Decommissioning2.1 Roadmap of the top-opening investigation method

After this point, a prior site survey, information on available
space at the site, and input from engineers will be needed.

Achievements to date and future plans[Expected remaining issues after all the implementation items of this projectand necessary actions to address them are completed]· Coordination on providing utilities (such as water, electricity, and gas, as well as
discharged water and waste treatment) at the site and supply of them to devices· Manufacturing design for manufacturing devices(including the review and revision of the specifications and drawings based on-site
information provided by prior site surveys and element test results, creation of parts
drawings, preparation of design calculation documents such as seismic capacity
calculation sheets, and preparation of inspection manuals)
Develop equipment· Construction of ancillary systems
specifications· Regulatory approval· Work area preparations (confirmation of available space)· Partial mockup test device manufacturing· Partial mockup tests
Precondition· Manufacturing devices for fully
formulation andequipped investigations
review· Training and test-run

TRL
7

6

5

4

Organize functional
requirements

Organize safety
requirements

Organize safety requirements

33
Element test2

2

Basic design/detailed
designPreparation for on-site
investigation
Completion of spent fuelremoval from SFP

Construction of ancillarysystems
Workspaceavailability at the site
Site information
obtained from priorsite surveys

7
Regulatory
approval
On-siteinvestigation

6
Training and test-run

Manufacturing devices forfully equipped
investigations

5

Partial mockup test

Partial mockup test device
manufacturing

4
Organize functional
requirements

No.5

Study equipment
specifications

Detailed device design
based on site information· Work cell
· Boundary protection device· Processing apparatus· Investigation system

Element test
· Small hole penetrating of PCV/RPV heads· RPV thermal insulation hole opening and removal· The reactor core internal structure cutting and removal· Investigate system guiding methods· Capture video image by investigation
Safety assessment such
systems and image quality evaluation

as radiation exposure

Conceptual design

1

1Applicability
study

until FY2015

Method rationalization based on
precondition review

FY2016 to FY2017

Study ancillary system
requirements

FY2018 to FY2019©International Research Institute for Nuclear Decommissioning2.2 Roadmap of the side-opening investigation method

After this point, a prior site survey, information on available
space at the site, and input from engineers will be needed.

Achievements to date and future plans[Expected remaining issues after all the implementation items of thisproject and necessary actions to address them are completed]· Coordination on providing utilities (such as water, electricity, and gas, aswell as discharged water and waste treatment) at the site and supply ofthem to devices· Manufacturing design for manufacturing devices(including the review and revision of the specifications and drawings based
on-site information provided by prior site surveys and element test results,
creation of parts drawings, preparation of design calculation documents
such as seismic capacity calculation sheets, and preparation of inspection
manuals)
Develop equipment· Construction of ancillary systems
specifications· Regulatory approval· Work area preparations (confirmation of available space)· Partial mockup test device manufacturing· Partial mockup tests· Manufacturing devices for fully equipped investigations· Training and test-run
4

TRL
7

6

5

4

3

3

Organize functional
requirements

Study equipment
specifications

Organize safety
requirements· Work cell
· Processing apparatus· Boundary protection device· Access device· Maintenance unit

Element test

2

Basic
design/detailed
design21Completion of spent fuelremoval from SFP

Construction of ancillarysystems
Workspaceavailability at the site
Site information
obtained from priorsite surveys

7
Regulatory
approval
On-siteinvestigation

6
Training and test-run

Manufacturing devices forfully equipped
investigations

5

Partial mockup test

Partial mockup test device
manufacturing

Detailed device design
based on site information

Safety assessment
such as radiation
exposure

Applicability
study
Method rationalization based on
precondition review

FY2016 to FY2017

Preparation for on-site
investigation· Reinforced concrete machinability· Sealing performance of the boundary· Wastewater collection and discharge· Strength of joints

Conceptual
design1

No.6

Study ancillary system
requirements

FY2018 to FY2019©International Research Institute for Nuclear Decommissioning3.1 Implementation items of the project (FY2018-2019)
Implementation items(1) Investigation and development plans (See 6.1)
① Organization of fuel debris retrieval information (See
6.1.1)② Investigation update and development plans (See 6.1.2)(2) Investigation method planning (See 6.2)
① Detailed design of work steps and rationalization of
construction procedures (See 6.2.1)② Clarification of safety requirements and exposure
assessment (See 6.2.2)(3) Study of ancillary systems required for investigations(See 6.3)

No.7

Outlines of items
Organize and update the list of items to be investigated about RPV insideconditions.
Update investigation and development plans based on the organized andupdated list of investigation needs. In addition, review preconditions
required for the investigation.
Design detailed work steps based on the work steps outlined in the FY2017
project and clarify and rationalize procedures for each work step.
Clarify safety requirements for investigation, perform exposure assessment,
and assess the impact of investigations on the surrounding environment.
Clarify the timing of ancillary systems required for investigations and safetyassurance, such as gas and negative pressure control system, nitrogen
supply system, and criticality control system, and required specifications forthem from the investigation team to prevent contaminated dust fromspreading.

(4) Development of access and investigation equipment (See
6.4)
① Development of investigation equipment for top accessmethod (See 6.4.1)

Develop technologies that can solve issues to realize investigation works at
the site, design devices and systems in detail, and rationalize them basedon element tests performed in the FY2017 project. In addition, consider thenecessity of elements tests for device development and perform them ifnecessary in FY2018 to verify the devices' on-site applicability toinvestigation works based on the correct understanding of the actual site
conditions.

② Development of investigation equipment for side accessmethod (See 6.4.2)

Develop technologies that can solve issues to realize investigation works at
the site, design devices and systems in detail, and rationalize them basedon the FY2017 project's outcomes. In addition, consider the necessity ofelements tests for device development and perform them if necessary in
FY2018 to verify the devices' on-site applicability to investigation works
based on actual site conditions.
©International Research Institute for Nuclear Decommissioning3.2 Correlation among implementation items: Top-opening investigation method· Development of a negative pressure control
system for contamination spread prevention· Study on the method/carrier to carry in/out
the equipment

Work cell⇒ 6.4.1.1

Airlock cellWork cell

Boundary function⇒ 6.4.1.2
maintenance system· Hole opening machinedevelopment for each location· Small diameter holepenetrating machinedevelopment, etc.

Processing
apparatus⇒ 6.4.1.3

PCV head
RPV thermal
insulation

Coupling
deviceTool box
Gate valve on thetool box side

Well cover

No.8· Tool box design· Gate valve development· Seal mechanism development
and design (resin packing)Tool box transfer carrier

Tool box transfer
carrier

Tool box

Gate valve on theboundary guidepipe side

Gate valve on
the boundary
guide pipe side

Boundary guide
pipe

Boundary guide pipe
(section to run through PCV head)

RPV head

Investigation system
Steam dryer
PCV headprocessing
apparatus

RPV insulation
hole opening
machine

RPV head sparenozzle flange holeopening machine

Steam separator
Shroud headUpper grid plate

Machines to reach andcut reactor internals⇒ 6.4.1.4· Investigation system development· Investigation equipment
development· Access device development· Visibility simulation· Horizontal extension arm design,
etc.

Simulation of overlaying
captured images

AWJ tool head

* AWJ: Abrasive Waterjet

Horizontal extension arm
Suspension device
Access device

For preliminary verification
For full investigation
Investigationequipment©International Research Institute for Nuclear Decommissioning3.2 Correlation among implementation items: Side-opening investigation method No.9
Processing apparatus used until reaching the shroud
head(Hybrid waterjet cutting head)

Work cell⇒ 6.4.2.2
R/B wall

WJ nozzle
AWJ nozzle

Tool box AC0

RPVTool box ACx

Suction port

PCV
Light guidetube

Biologicalshielding wall

Biologicalshielding wall

PCV sleeve
PCV guide tube

Processing apparatus used until
reaching the shroud head
(Wastewater collection system)

Cement milk

SleeveCompressed seal
(seal solidification by EPDM)

Boundary function maintenance device(Sealing performance around the guide tube)⇒ 6.4.2.3

Boundary function maintenance device(Guide tube fixation to the hole of thebiological shielding wall)⇒ 6.4.2.3⇒ 6.4.2.2©International Research Institute for Nuclear Decommissioning3.3 Relations with other research【Input】
・ Investigation needs (investigation items
to be required for the study of fueldebris retrieval and criticality control)

No.10

Study and research on
method and equipment toretrieve fuel debris

Study and Research on
criticality control[Output]
Information regarding the
RPV interior(Visual information, doserate, etc.)【output】
・Requirement specifications forthe ancillary system
Development of technology
for investigation inside the
RPV
The Project【Input】
・Estimation investigation of inside
the RPV/PCV (conditions of thestructure and transmissivity, etc.)

Equipment manufacturing,
mockup, etc.

【input】
・Timing of investigation
to be conducted
・Site conditions, etc.

Study and research on theidentification of the reactor
conditions

Actual investigation[Output]• Prerequisites and requirements forthe site investigation• Requirement specifications of theancillary system

Information regarding interfaces,interfering objects, and timing for
application, etc.

Investigation inside the
PCV©International Research Institute for Nuclear Decommissioning4. Schedule* Preliminary test: a test to examine the feasibility of an element technology and formulate an element test plan
Element test: a test to validate device specifications or obtain information to determine specifications

Implementation items(1)

Investigation andDevelopment
Planning① Organization offuel debris retrieval
information② Formulate andupdateinvestigation anddevelopment plans

FY2018Organization of fueldebris retrieval
information

No.11

FY2019

List investigation
needs

Formulate an
investigation planand preconditions

Study of preconditions for investigation timing and investigations at thesite

Update

Review of investigation and development plans
Update work steps
and procedures

Detailed design of work steps and procedure rationale

UpdateReflect on formulated preconditions
(2)

(3)

Investigation method plan

Enumerate safety requirements and exposure
assessment results

Development ofaccess andinvestigationequipment

Required ancillarysystems’
specifications

Study on ancillarysystems’ applicability

Study of ancillary systems required forinvestigation works① Development ofinvestigationequipment for the
top access method(4)

Clarification of safety
requirements andexposure assessment

Detailed design, rationale, and equipment specifications
considering site work

Detailed method design and rationale
and determine equipment specifications
according to the precondition review

Element test (Preliminary test andelement test planning)

Consider the need for anelement test and plan if
necessity

Element test (preparationand implementation)

Detailed design, rationale, and equipment specifications considering site work
② Development ofinvestigationequipment for side
access method

Verify on-site
applicability

Verify on-site
applicability

Equipment design for element tests
Consider theneed forelement tests

Element testplanning

Element test

©International Research Institute for Nuclear Decommissioning5. Project organization chart

No.12

International Research Institute for Nuclear
Decommissioning (IRID Head Office)Tokyo Electric Power Company
Holdings, Inc.

Toshiba Energy Systems andSolutions Corporation

Cooperating development
project teams

 Integral planning and technical supervision
 Management of technical development and its progress

Development of Investigation for Further
Increasing the Scale of Retravel Debris
and Internal Structures

Hitachi-GE Nuclear Energy, Ltd.

Mitsubishi Heavy Industries, Ltd.

(1) Investigation and development planning①Organization of information required forfuel debris retrieval②Planning and updates of investigationand development(2) Creation of method planning(3) Study of the ancillary system forinvestigation(4) Development of access andinvestigation equipment①Development of equipment for the topopening investigation method(1) Investigation and development
planning①Organization of information required
for fuel debris retrieval②Planning and updates of investigationand development(2) Creation of method planning(3) Study of the ancillary system forinvestigation(4) Development of access andinvestigation equipment①Development of equipment for the topopening investigation method(1) Investigation and development
planning①Organization of information
required for fuel debris retrieval②Planning and updates ofinvestigation and development(2) Creation of method planning(3) Study of the ancillary system forinvestigation(4) Development of access andinvestigation equipment①Development of equipment for theside-opening method

IHI Corporation
・(4)①Study and test of opening
device for accessing the RPV head

Sugino Machine Limited
・(4)①Structural design ofprocessing equipment for the reactor
internals to develop opening
equipment of the upper grid plate.

IHI Corporation
・(4)①Study and test for boundaryfunction maintenance equipment
KIMURA CHEMICAL PLANTS CO.,LTD.
・(4)①Study on a work cell

Hitachi Power Solutions Co., Ltd.
・(4)①Test production and test ofprocessing equipment for the reactor
internals to develop opening
equipment of the upper grid plate.

Orano ATOX D&D Solutions (ANADEC)・(4)②Development of access andinvestigation equipment
Kajima Corporation
・(4)②Concretization of the structure
for accessing the reactor core fromthe side, such as a work cell andmaintenance unit.

©International Research Institute for Nuclear Decommissioning6. Implementation details(1) Preconditions (including outcomes in previous fiscal years)
Items

No.13

Preconditions

Investigation needs· Collect information and data about reactor inside conditions by accessing it can accelerate the detailed design of fuel debris retrieval
devices.
· Data to be collected are two types: visual images and dose.

Implementation policy

Do not cut or touch any structures under the upper grid plate unless necessary as defined by fuel debris Cutting will be allowed only forthe shroud head and structures above it.

Reactors to be investigated(Achievements through FY2017)· Top opening: Unit3· Side opening: Unit2

Access route(Achievements through FY2017)· Top opening: From right above RPV spare nozzle to the reactor core
· Side opening: From the air conditioning room roof on the east side of R/B to the reactor core

Preconditions of work areas· Top opening: Interfering objects on the operation floor should have been removed, and shielding should have been installed on thefloor. An environment with a dose rate of 1 mSv/h or less should have been established in work areas.
· Side opening: Exhaust ducts and chillers should have been removed. An environment with a dose rate of 1 mSv/h or less should havebeen established in work areas.

Estimated air dose rate(Max)

· Drywell: 16 Sv/h
· Inside the reactor (near steam dryer/steam separator): 800 Sv/h
· Inside the reactor (near reactor core): 5,000 Sv/h

Estimated conditions of eachstructure· From well cover to shroud head: Not damaged· Upper grid plate and below: Seriously damaged Note that access to the reactor core’s deepest part must be based on the assumptionthat all the fuel and structures in the reactor core should have melted down to the bottom.

Light transmission(in a foggy condition)· 46% at 1.5 m distance (from Unit1 PCV inside investigation result): Absorption coefficient of 0.511· 72% at 1.5 m distance (from Unit2 PCV inside investigation result): Absorption coefficient of 0.223 ⇒ Used as design conditions

Workplace and remote
operability· Top opening: Operation floor In addition, the work area height should be 1.3 m from the operation floor.
· Side opening: The air conditioning room roof on the east side of R/B

Use of remote operation

As a basic policy, equipment and devices should be installed by a direct operation. Cutting and investigation work should be done
remotely.

Handling of processed materials
generated by cutting

The possibility of a criticality accident is considered low even if the possibly largest processed materials(about 16 kg) falls to the reactor
core. Falling processed materials are considered acceptable as long as they are within this size.

Boundary(Achievements through FY2017)

The boundary should be established by PCV. As a basic policy, a work cell should be prepared on the operation floor and/or the air
conditioning room roof. Maintain negative pressure inside to prevent radioactive material spread in case of leakage through holes madefor the investigation.
©International Research Institute for Nuclear DecommissioningNo.14

6.1 Investigation and development planning
6.1.1 Organization of fuel debris retrieval information

Investigation needs that contribute to the fuel debris retrieval are collected, organized, and updated based on
the latest information, such as that on the lower part of PCV obtained from PCV inside investigation.
Item

Outlines

Progress status

Investigation needs
Collect information for
Organization of fuellisted in FY2016 wererequired fuel debris
1 debris retrieval
updated. There was no
retrieval from each PJ
information
change in investigation
and update it.
items. (Reported)

FY2018

Listing investigation
needs

FY2019Result of investigation needs

The investigation needs listed in FY2018⚫

The early collection of information and data about reactor inside conditions by accessing it can accelerate
the detailed design of fuel debris retrieval devices.
✓ Essential for detailed design The sooner investigation is performed, the more useful the investigation
results.
✓ Information about the reactor core and bottom is the most important, followed by information about theupper part of RPV inside, such as the steam dryer and steam separator.
⚫ The following information is considered effective for risk reduction:✓ Visual information: can help determine the deformation and damage of structures, distribution of fueldebris, and tree stump shape fuel. An investigation that provides information about overall conditions
such as the distribution of fuel debris and inclination and deformation of structures is more useful thandetailed investigations, including dimensional measurement. Imaging data resolution should be on theorder of several cm.
✓ Dose rate: Estimation of the order of dose rate (1 to 103 Gy/h)©International Research Institute for Nuclear DecommissioningNo.15

6.1.2 Investigation update and development plans

An investigation plan is formulated in FY2018 to rationalize each action item about the investigation needs listed
in Section 6.1.1. The site's latest conditions, including the planning of fuel removal from the fuel pool, should bereflected for a more practical updated investigation plan. Simultaneously, the implementation timing andpreconditions of the on-site investigation (on-site validation), such as necessary preparations, should be clarified.
Additionally, the development plan of access and investigation equipment should be updated as needed.
Implementation
items

1

2

Outlines

Development of an
Develop an overall
RPV insideschedule of RPV inside
investigation
based on the SFP fuelimplementation
removal and fuel debris
plan based on the
retrieval plans.
entire plan

Progress status

FY2018Update the investigation and development Determination of investigationplans based on the updated investigation
implementation timing andneeds list. (Reported)
Update the investigation plan based on
environmental conditions
the latest information, such as that about
the site condition.

FY2019Investigation plan andpreconditions formulation

UpdateInvestigation plan andpreconditions review

Estimate the structures’ Analyze the temperature change in theconditions based on the reactor core internal structures based on Temperature change estimation
PCV inside investigation the result of the accident progression
Evaluation of theresult and the Reactor
analysis performed by the Reactor Inside
structure condition
Inside Condition
Condition Investigation Project in FY2017. Study of the influence of structures
Investigation Project
Estimate the structures’ condition.
outputs in 2017.
(Reported)
Verify the estimated air
Estimation ofdose rate of 5,000 Sv/hthebased on PCV insidecontamination
Air dose rate
investigation results and Estimate the dose rates to determine theAir dose rateestimation
the outputs of thedevice design preconditions. (Reported)
level ofestimation
Reactor Inside Condition
structures
Investigation Project in2017.
Risk assessment
for the occurrenceof a criticality
accident byprocessedmaterials falling*

The possibility of a criticality accident is
The maximum weight ofconsidered low even if processed
Study of evaluation policies
processed materials ismaterials falls as long as its weight isdetermined in terms of
Risk assessment for a criticality
within an expected range. The public andnot causing a criticality
workers' exposure outside R/B would
accident
in case of a heavy object fall
accident even if it falls toremain within a permissible level even if athe reactor core.
criticality accident occurs. (Reported)©International Research Institute for Nuclear Decommissioning* Use the same basic evaluation method as the other project teams. Evaluations expected to be performed in RPV inside investigation and modeling are performed in this project.

6.1.2.1 Update of the investigation plan
Expected work steps for Unit 2 and Unit 3 in consideration of overall processes(draft)Work area
Operation
floor(Top floor)

Expected work steps (time scale not considered)Preparation for SFP fuel removal(Shield installation, exhaust ventilation systeminstallation, etc.)

SFP fuelremovalUnit2

The air
conditioning
room roof(Side)

R/B 3rdfloor

R/B 1st floor

Yard around
R/B

Operation
floor(Top floor)

PCV inside detailed
investigation and fuel debris
retrieval tests

Establish anegative pressure
environment in
PCV

Upper R/B
dismantlement

Work area
setup

Top-opening
investigation

Blow-out panel
duct removalInterfering object
removal from theroof of the air
conditioning room

Supportstructure
construction

Side-opening
investigation

Preliminarysite survey

Interfering
object removal

Gradually scaled
up fuel debris
retrieval tests(Side entry)

Preliminarysite survey

SFP condition
control

SFP fuelremovalEquipment
removalUnit3

Preliminarysite survey

Fuel debris
removal(Top entry)

Fuel debris
removal(Side entry)

Platform
removalExtensionbuilding
construction

Upper dome
removalShieldingremovalWork area
setup

Top-opening
investigation

Interfering object
removal from theroof of the air
conditioning room

Supportstructure
construction

Side-opening
investigation

Preparation for SFP fuel removal(Platform construction, etc)

SFP fuelremovalRemarks

Preliminarysite survey

The air
conditioning
room roof(Side)

R/B 3rd
floor

No.16

[Preconditions]· Only implement the side-opening investigation before the top-opening investigation.
· Plan to implement the top-opening after removing the SFP fuel and establishing anegative pressure environment.

Fuel debris
removal(Top entry)

Interfering
object removal

Establish anegative pressure
environment in
PCV

R/B 1st floor

Yard around
R/B

Platform
removal: Relevant to RPV inside investigation

Fuel debris
removal(Side entry)<Considerations andpreparations>o Common to both units· Implementation of preliminarysite surveys· Decision on the priority orderof each work
· Determination of theimplementation period ofeach item· Determination of negative
pressure activation timingo For Unit2· Time when interfering objects
can be removed from the air
conditioning room roof
· Dismantle the upper part of
R/B and coordinate space
available on the operation
floor for fuel debris retrieval
works after completing fuelremoval from SFP and onsite investigationo For Unit3· Coordinate space allocationof the operation floor for fueldebris retrieval work after
completing fuel removal from
SFP and on-site investigation· Investigate the well coverdamageExtensionbuilding
construction©International Research Institute for Nuclear Decommissioning6.2 Investigation method planning

No.17

6.2.1 Crystallization of work steps and rationalization of work procedures
Design of detailed work steps based on the series of work steps outlined in the FY2017 project.
Clarification and rationalization of work step procedures.
Implementation
items

Outlines

Progress status

FY2018FY2019

List of investigation needs
Detailed design andrationalization of work
1 steps and procedures(Creation of a step
diagram)

Detailed design andrationalization ofUpdate of work procedures
construction procedures based on the progress of design
after STEP 2 based on
work, including element test
the results of the projects results.
until FY2017

Preliminary site survey(STEP 1) planning

Study of the access route forinvestigation equipment to the
Study of access routes to inside of the reactor andthe inside of the reactor penetrating locations. A specificwell and determination of plan, including implementation
penetrating locations
timing, needs to be discussedwith the Tokyo Electric Power
Company (TOPECO).

2 Study of preliminary site

Study of penetrating
investigation methods
methods(STEP 1) for penetrating

Conceptual study for a method
applicable to the penetrating of
the well cover and the shielding
installed on it. (Reported)

Study of preliminary site
investigation methods(STEP 1) forinvestigation

Study of equipment used for theinvestigation and suggestion of
outputs obtained by theinvestigation. (Reported)*

Study of investigation
methods

Update work steps and procedures
Detailed design andrationalization of work
steps and procedures

Plan of preconditions
Reflection of results Update

Within the project
scope
Outside the project
scope

Planning
On-site work planning
Conceptualstudy
Detailed study

Conceptualstudy
Detailed study* These items are necessary only for the top-opening investigation method because preliminary site investigations for the side-opening investigation method will be implemented using existing technologies and devices. Thus, there are no elements to develop.

©International Research Institute for Nuclear Decommissioning6.2.1.1 Work step: Top-opening investigation method (1/2)
Main stepSub-step(Others)

Sub-step(Investigation)

No.18
Sub-step(Cutting)

Work cell
installation

Work cell
installation

Carry in transfer
carriers

TemporaryshieldingremovalWell cover
penetrating andinside investigation

1st and 2nd layers
Large hole
penetrating and core
removal

3rd layer
chipping

3rd layer small
hole opening

Pre-investigationof well coverinterior

3rd layer largehole penetrating
and core removal

Investigation ofwell coverinterior

Guide pipe
installation

PCV headsurfacetreatment

PCV headsurfacemeasurement

Base plate
installation

Install the main partof the boundary
guide pipe

Install sideshielding andseal plate

Install the gate valve
on the boundary
guide pipe side

PCV head hole
opening and inside
investigation

PCV head small
hole opening

Pre-investigationof inside of PCV
head

PCV head hole
opening

Investigation of
inside of PCV
head

RPV thermal insulation
hole opening and inside
investigation

Cutting RPV thermal
insulation fixing fittingat the spare nozzle

RPV thermal
insulation
removal

RPV sparenozzle cleaning

RPV sparenozzle surface
measurement

Pre-investigation of
inside of RPV
thermal insulation* Although it is not shown in the diagram, an airtightness test should be performed at a tool change in each sub-step.
©International Research Institute for Nuclear Decommissioning6.2.1.1 Work step: Top-opening investigation method (2/2)

RPV head hole
opening and inside
investigation

RPV spare nozzle
Small hole
penetrating throughthe flange

Pre-investigationof inside of RPV
head

RPV sparenozzle flangehole opening

Investigation of
inside of RPV
head

Cutting RPV
spare nozzle(inside)Steam dryer bottom
plate hole opening andinside investigation

Small hole openingof the steam dryer
bottom platePre-investigation
inside of thesteam separator

Steam dryer
bottom plate hole
openingPre-investigationof outside thesteam separator

Pre-investigationof inside thesteam separator

Steam separator
hole opening andinside investigation

Steam separator
hole opening

Shroud headhole opening

Investigation of
inside of reactor
core

Investigation of inside
reactor core
(Advance in a lateral
direction)

PCV head sealing

Install a PCV
head sealing
plug

Guide pipe removal

Remove the gate
valve on theguide pipe side

Seal plate andside shielding
removalRemove components
attached to the guide
pipeGuide pipe
removalWork cell removal

Temporaryshieldinginstallation

Transfer carrier
withdrawal

Work cell
removalNo.19

Cutting RPV
spare nozzle(outside)

Remove the baseplate and its
mounting base

* Although it is not shown in the diagram, an airtightness test should be performed at a tool change in each sub-step.
©International Research Institute for Nuclear Decommissioning6.2.1.2 Work step: Side-opening investigation method (1/2)
Sub-step(Others)

Main stepSub-step(Investigation)

Preparatory work

Clean up the installation area

Carry in and install thecontrol center

Carry in and install theplatform

Work cell installation, 3rdfloor investigation

Installation of R/B wall frame

Carry in and install the work
cell

Carry in and install theventilation system

AC0 installation

Building footprints on R/B
wall

Carry in and installation of
the multi-use plateAC0 carry in and installation

Light guide tube
installation

Penetration of R/B wall,inside ventilation

Carry in and install AC2

Carry in and install the lightguide tube

AC2 removal, inside
cleaning, and tool
preparation

PCV sleeve installation

Carry in and install AC3

Biological shielding wall
footprint building

AC3 removal, inside
cleaning, and tool
preparation

Carry in and install AC3

PCV sleeve insertion

Filling and hardening of
cement milk

AC2 removal, inside cleaning,
and tool preparation

Carry in and install AC3

Biological shielding wall
through penetration

AC3 removal, inside
cleaning, and tool
preparation

PCV guide tube insertion

AC2 removal, inside cleaning,
and tool preparation

PCV guide tube installation

No.20
Sub-step(Cutting)

Unit2 3rd floor investigation

Carry in and install AC2* Although it is not shown in the diagram, an airtightness test
should be performed at a tool change in each sub-step.

* See Equipment and device specifications No. 75 and No. 77 for toolboxes AC2, AC3, and AC5.

©International Research Institute for Nuclear Decommissioning6.2.1.2 Work step: Side-opening investigation method (2/2)
RPV guide tube
installation

Carry in and install AC3

Reactor shielding wall
through penetration

RPV guide tube
insertion

AC2 removal, inside cleaning,
and tool preparation

Hole opening through RPV
and shroud head (small
hole)

Carry in and install AC3

Hole opening through RPV(large hole)
Penetrating through the shroudhead

AC3 removal, inside cleaning,
and tool preparation

Carry in and install AC2

Penetration throughRPV and shroud head

Change investigationequipment

Implement investigation 1

Change investigationequipment

Hole opening through RPV (large
hole)
Penetrating through the shroudhead

AC3 removal and inside
cleaning

Implement
investigation 2

AC5 transportation andinstallation

Implement investigation 2

AC5 removal and inside
cleaning

RPV guide tube
removalCarry in and install AC2

RPV guide tube
removalAC2 removal and inside
cleaning

PCV plug installation and
PCV guide tube removal

Carry in and install AC2

PCV plug installation

PCV guide tube
removalLight guide tube
removalCarry in and install AC2

Light guide tube
removalAC2 removal and inside
cleaning

Work cell/attachedequipment removal

Multi-use plate
Plug

Work cell removal

AC0/platform removal* See Equipment and device specifications No. 75 and No. 77 for toolboxes AC2, AC3, and AC5.

No.21

AC2 removal and inside
cleaning

Attached equipment
removal©International Research Institute for Nuclear DecommissioningNo.22

6.2.2 Clarification of safety requirements and exposure assessment

Safety requirements are listed and classified as related to an accident event, single failure, and seismic category.
At the same time, exposure assessment is performed based on the device design and detailed investigation
planning. Through those actions, the investigation works’ impact on the surrounding environment is evaluated.
Implementation
items

Outlines

Implementation Items andResults

FY2018FY2019

List of investigation needs
Formulate safety design process andOrganize concepts ofclarify safety requirements. Based onsafety requirements forthe work organization results, identify
Clarification of safety investigations.
the required safety functions under
1 requirements⇒ Related projects:
normal and abnormal conditions.
Fuel Debris Retrieval
In addition, consider and list safety
Methods and Systems
requirements against external events.

Estimation of thecontamination levelof structures

Scrutiny of the
exposure
2 assessment model(airflow analysis) *Exposure
assessment*

Consider theassessment
methods

Update work steps and procedures

Safety requirements list
Clarification of safety requirements

Estimate the amount of Estimate the amount of adhered Cs
Estimation of the contamination
radioactivity thatbased on the result of the accident
level of structures
spreads during cutting progression analysis performed by theand reflect the result in Reactor Inside Condition Investigation
the assessment model. Project team in FY2017. (Reported)
Analyze airflow in PCV
to concretize theexposure assessment
model and reflect
results in it.

Analyze the exposure assessment
model and the airflow. Evaluate theradioactive dust reduction effect bygravity settling.

Assess exposure levels
The exposure levels estimated in(of workers and at theprevious years were reexamined withborder of the premise)
updated conditions and found to becaused by investigation
safe.
works.

Study the assessment models
Modeling and analysis

Exposure assessment result
Exposure
assessment* Use the same basic evaluation method as the other project teams. Perform the evaluations appropriate for the RPV inside investigation and modeling.
©International Research Institute for Nuclear Decommissioning6.2.2.1 Clarification of safety requirements(Safety design process)No.23
Establish protection measures undernormal conditions

Develop abnormality detection
methods and responses

List safety
requirements madeby the Fuel Debris
Retrieval Project

START
Initial concept

Identify safety-functionthreatening risks

Elaborate on the useof the RPV inside
investigation
Develop the detection
methodExamine risk factors forsafety requirements which
may exist in each work stepunder normal conditions

Safetyassurance
concept
undernormalconditions

Exposure assessment

Enumerate safety requirements
against risks caused by external
eventsExamine risk factors forsafety requirements
Exposure
assessment

Countermeasuredevelopment

Listing necessary
equipment
Does theevent meet thecriteria undernormalconditions?

Establish safety design, including
measures against external events

Does theevent meet thecriteria undernormalconditions?

Yes

No
Yes

Safety assurance
concept underabnormal conditions

Development ofsafety functions

No

Development ofsafety functions

END
Establish a total safetyassurance concept©International Research Institute for Nuclear DecommissioningNo.246.2.2.1 Clarification of safety requirements
Internal event(Summary)
Abnormal conditions
Safety requirements
Safety functions under normal
conditions

Confinement ofradioactive materials Confinement of airborne radioactive
materials by the primary boundary
in the gas phase

Confinement of
In accordance with the methods toradioactive materials confine airborne radioactive materials byin the liquid phase the primary boundary
Use of a criticality monitoring systemand prevention of tools and materials
from falling
The weight of processed materials
pieces needs to be controlled if they areallowed to scatter.
Use a temperature monitoring systemand prevent tools and materials fromfalling

External event
Earthquake

Detection

Countermeasures

Gas control system
breakdown alarm,radiation andradioactive duct
monitoring in thereactor well,operation floor, andwork cells

Activate the backup gas control system, shut
off the nitrogen supply system if the backup
system fails to function, shut off the migrationof radioactive materials to the tool boxes by
isolation valves, reduce the amount ofradioactive material leakage to the operation
floor by installing a work cell, and reduce thespread of radioactive materials by installing aventilation system (with filters) in the work cell.

Confirm no
additionalsafetyfunctions are
required.

－

－

－

－

－

－

－

－

－

Prevention of theexcessive spread ofradioactive materials Monitor the appropriate process controlof cutting work
due to abnormal
cutting－－－

Reduction of workers’
radiation exposure Provision of shielding(External exposure)

－

－

－

Reduction of workers’ In accordance with the methods toradiation exposure confine airborne radioactive materials by(Internal exposure) the primary boundary

－

－

－

Work conditions should be properly
Prevention of fire andmanaged to avoid explosion due toexplosion
locally accumulated hydrogen.

－

－

－

Criticality control

Overheating
prevention

OthersEquipment
installed for
RPV inside
investigation
shall bedesigned sothat it won’t
degrade theenvironmental
conditions of
the 1st floor.

©International Research Institute for Nuclear DecommissioningNo.256.2.2.2 Exposure assessment: Details of the assessment● Exposure assessment under the PCV condition of a slight positive pressure (assessment
conditions changed from those used in FY2017)
Assessment for the top-opening investigation method
1. Concentration of airborne radioactive material (under normal conditions)① Activity concentration near R/B: Activity concentration that migrates to near R/B via the operation floor② Activity concentration near the turbine building (T/B): Activity concentration that migratesc. Tool box
to near T/B via the gas control system
2. Radiation dose at the border of the premise① Exposure dose migrated to the surrounding environment via the operation floor
b. Guide pipe
② Exposure dose migrated to the surrounding environment via the gas control system
The sum of ① and ② is the assessment value.
①

Spreading

R/B

General public

Border of②
the premise
Exposure doseas the sum of
Spreading① and ②WorkerNear T/B
Activity
concentration ②

PCV head leakNitrogen feed
(Nitrogen supply
system)T/B

Exhaust(Gas control system)
FilterAerosol
generatedby cutting

Workera. PCV

Near R/B

Slightly higher thanatmospheric pressure● Primary boundarya. PCVb. Guide pipec. Tool box

Activity
concentration ①©International Research Institute for Nuclear DecommissioningNo.266.2.2.2 Exposure assessment results for the top-opening investigation(compared to those in FY2017) Numbers in ( ) are margins (if meeting the criteria: Pass) or insufficiencies (if not meeting: Fail) expressed in the number of digits
Evaluation item

Activity concentration near R/B(Cs-137)[Bq/m3]
Activity concentration near R/B(Pu-238)[Bq/m3]
2. Radiation dose at the border ofthe premise[μSv/y]Results of the previous
assessment

Results of the assessment inthis project

1.7E+00 (*1)

2.6E-02 (*1)

Pass (3-digit)

Pass (5-digit)

2.7E-5 (*1)

2.6E-07 (*1)

Pass (4-digit)

Pass (6-digit)

1.9E+01 (*2)

1.6E-01

Pass (1-digit)

Pass (3-digit)

Effects ofreview

2-digitTarget values

3.0E+03(Outdoor,
without mask)

7.0E-01

2-digit(Outdoor,
without mask)

2-digit

1.0E+02(*1) These values of the activity concentration near R/B were obtained during the cutting of the steam separator, which showed the maximum activity concentration in the assessment
in FY2017 (except for the activity concentration near T/B via the gas control system).
(*2) The radiation dose at the border of the premise was the sum of the radiation doses at the same location caused by the cutting of the PCV head, RPV thermal insulator, steam
dryer, steam separator, and shroud head (including that originated from the exhaust of the gas control system with a filter DF of 1,000).

The exposure assessment results had shown that investigation
for the inside of RPV can be conducted by the top-opening
investigation method under the PCV condition of a slight
positive pressure from a perspective of a safety assessment. It
is the same conclusion as the FY2017 assessment.
©International Research Institute for Nuclear DecommissioningNo.276.2.2.2 Exposure assessment: Activity concentration in R/B
Item① FY2017 top-opening
investigation method② FY2019 top-opening
investigation method

The difference in
number of digits[① minus ②]

Target values

Maximum activity concentration(Cs137) in R/B (Bq/m3)

1.1E+06

1.9E+07- 1-digit

3.0E+03(Outdoor, without mask)

Maximum activity concentration(Pu238) in R/B (Bq/m3)

1.8E+01

8.6E+010-digit

7.0E-01(Outdoor, without mask)

On the other hand, the exposure assessment result had shown that the top-opening investigation for
the inside of RPV cannot be conducted under the PCV condition of a slight positive pressure,because radioactivity concentration in R/B is higher than target levels same as the result in FY2017.
The following changes in assessment conditions affected the result of FY2019 assessment greatly:• More structures were added as an assessment target. ⇒ All conceivable structures were considered to be a
cutting target.
• The stagnation and sedimentation in PCV and R/B was taken into consideration. ⇒ The result of airflow analysis
using GOTHIC code was reflected.
• Radiation dilution effect by the volume of R/B ⇒ The volume of R/B used to calculate the dilution effect was
decreased.
Note that exposure assessment conditions (including contamination level setting using MAAP code, setting of thepercent of airborne spreading dust during cutting, leakage from PCV including leak locations and leak rate) areaccompanied with uncertainty. Additional information, such as site information, is needed to improve the accuracy of
the assessment.
There may still be a possibility to establish a safe environment by maintaining a slight positive pressure in PCV andnegative pressure in R/B. Further, there is also a possibility to establish a negative pressure environment in PCV withthe advancement of fuel debris retrieval method development and scaling up that will take place in parallel to thisproject.
©International Research Institute for Nuclear Decommissioning6.3 Study on investigation auxiliary system

No.28

The use timing of ancillary systems required for investigation works and safety assurance, such as the nitrogen supply
system, dust monitoring system, and criticality control system as well as gas and negative pressure control system, andrequired specifications for them from the investigation team are clarified to prevent contaminated dust from spreading.
Especially, the top-opening investigation method will be used under the PCV environment of negative pressure before fueldebris retrieval from the PCV bottom is started. Therefore, specifications need to be clarified for the gas control system and anegative pressure control system that will be required for negative pressure control. In addition, operation instructions willneed to be considered for a dust monitoring system if used constantly to prevent contaminated dust.
Implementation
items
Formulation ofrequired
specifications of
the systems
needed forinvestigation
works

1

No.

Outlines

Implementation Items
and Results

The investigation team clarifies
the use timing of ancillary systems
required for investigations, safety Required specifications wereconsidered based on theassurance, and required
created safety requirement
specifications.
⇒ Related projects: Fuel Debris list.
Retrieval Methods and Systems,
Criticality Control

Ancillary systems considered to benecessary for investigation works

FY2018FY2019Update work steps and procedures

Formulation of required
specifications forancillary systems

Study on ancillary systems’ applicability

Outlines1

Gas control system

System to reduce the concentration and amount of radioactive materials spreading out from PCV to thesurrounding environment as much as possible by the ventilation and filtration of gas in PCV

2

Nitrogen supply system

System to keep the inside of RPV and PCV in an inert condition to prevent hydrogen explosion by feeding
nitrogen3

Negative pressure control system(Only for top-opening investigation method)

System to keep the inside of PCV in a negative pressure environment to prevent airborne radioactive particles
generated by the cutting of structures from spreading out of PCV

4

Criticality control system

System to monitor the occurrence of a criticality accident caused by fuel and fuel debris lying in the reactor
during structure cutting work and to keep the accident under control even if it occurs ⇒ Use existing equipment.

5

Dust monitoring system

System to monitor the concentration of airborne radiation during structure cutting work

6

Water treatment system

System to reduce the concentration and amount of radioactive materials that are generated by structure cutting,mixed into wastewater circulation, and spread out from PCV to the surrounding environment by filtration©International Research Institute for Nuclear Decommissioning6.3.1 Requirements for ancillary systems

Countermeasures

Detection

No.29
Possible abnormal events were listed along with necessary responses to them based on
the created safety requirement list.

Detection and response

Necessary equipment

Detection by the gas control system breakdown alarm

Gas control system breakdown alarm

Radiation leak detection by the radiation monitor and dust
monitor of the reactor well

Radiation monitor and dust monitor
of the reactor well

Radiation leak detection by the radiation monitor and dust
monitor of the operation floor

Radiation monitor and dust monitor
of the operation floor

Radiation leak detection by the radiation monitor and dust
monitor installed in the work cell

Radiation monitor and dust monitor in
the work cell (to be developed in thisproject)

Activation of the backup system of the gas control system,
shutting off the nitrogen supply system if the backup system fails
to function

Backup gas control system

Mitigation of the migration of radioactive materials to thetoolboxes by isolation valves

Isolation valve (to be developed in thisproject)

Reduction of radioactive material leakage to the operation floor
by installing a work cellWork cell (to be developed in thisproject)

Reduction of radioactive material spread by installing aventilation system (filter) in the work cellWork cell ventilation system (filter)(to be developed in this project)©International Research Institute for Nuclear Decommissioning6.3.2 Ancillary systems for the top-opening investigation
No.

Ancillary systems1

Gas control system

2

Nitrogen supply system

3

Negative pressure
control system(Only for top-opening
investigation method)

4

Criticality control
system56FilterWork cell(Negative pressure)ExhaustN2 purge(only during a positive pressure in PCV)

N2
2. Nitrogen
supply system

ExhaustRadiation and dust
1. Gas control
monitoring systemsystem
3. Negative
Water treatment
systempressurecontrol system
4. Criticality control system(Noble gas monitor, radiation monitor)

No.30

Boundary

5. Radiation anddust monitoring
systemFilter

4. Criticality
control system(Standby liquid
control system)
Particlefiltrationequipment

6. Water treatment
systemUpdate ancillary systems necessary for the top-opening investigation method
based on the created safety requirement list (items written in red letters).
©International Research Institute for Nuclear Decommissioning6.3.3 Ancillary systems for the side-opening investigation

Work cell(Negative
pressure)N2
2. Nitrogen
supply system
3. Criticality control
system(Standby liquid
control system)
1. Gas control
systemNo.31

N2 purge

ExhaustFilterFilter

3. Criticality control system(Noble gas monitor,
radiation monitor)

Boundary

ParticlefiltrationequipmentNo.

5. Water treatment
system

4. Radiation and dust
monitoring system

Ancillary systems1

Gas control system

2

Nitrogen supply system

3

Criticality control system

Improvement of ancillary systems necessary for the4side-opening investigation method based on the created5
safety requirement list (items written in red letters).

Radiation and dust
monitoring system
Water treatment system©International Research Institute for Nuclear Decommissioning6.4 Development of access and investigation equipment
No.32
6.4.1 Development of investigation equipment for the top access method
Machines used for penetrating from the top of the operation floor to the shroud head, equipment to prevent dust
spread, and investigation equipment applicable to different investigation targets. Specifically, develop technologies
that can solve issues to realize investigation works at the site. Design and rationalize necessary devices andsystems in detail based on the outcomes of the projects until FY2017. In addition, consider the necessity ofelements tests for device development and perform tests if necessary in FY 2018 to verify the devices’ applicability
to site investigation works based on the correct understanding of the site conditions.
Implementation items

Outlines

Progress status

1 Work cell development
Develop technologies thatcan solve issues to realize
Development of a boundary investigations at the site.
2 function maintenance device
Design and rationalize
necessary devices and
See the following
systems in detail based on
pages.
the outcomes of theDevelopment of processing FY2017 project. Perform
3 apparatus
large-scale element tests,
like a combination test, as
needed.
Development of

4 investigation systems

FY2018FY2019Update work steps and procedures

Detailed design, rationalization,and equipment specification
determination in considerationof on-site working

Verify on-site applicability

Reflection of formulated
preconditions
Preliminary tests
Consider the need for anelement test and plan if
necessity

Element test

©International Research Institute for Nuclear Decommissioning6.4.1 Development of investigation equipment for the top access method No.33
Item

Implementation plan

Implementation Items and Results

Work cell· Rationalization of structures and methods in consideration of
the operability of each device· Rationalize device and equipment layout plans in and aroundthe work cell.
· Clarify installation methods and interface conditions· Detailed design of the negative pressure control system· Preparation for on-site works including penetrating and investigation work and the organization ofwork procedures for each operation such as toolbox change· Study ancillary systems required for the work cell (negative pressure control and monitoring
systems).
· Organize required utilities and peripherals as well as interface information for each device· Examine layout plans in detail.
· Redundant design (dual system design) of the exhaust system in preparation for a failure

Boundary protection
equipment· Rationalize structures and methods in consideration of ease of
construction· Improvement of the reliability of the guide pipe sealingmechanism for negative pressure· Verification of the sealing performance (confinement
performance) of the joint between the guide pipe and toolbox· Operating procedures and necessary functions were reviewed and organized for the transfer carrier,connection mechanism, and gate valves in connection with toolbox replacement.
· Determine a sealing mechanism applicable to negative pressure through a preliminary test.
· Verify a temporary clamping method and necessary clamp force through the gate valve and joint
preliminary tests.
· Perform preliminary tests on the connection mechanism in terms of the up/down movement of its
bellows, forced separation, and sealing performance, and confirm that the targeted functions andperformance can be achieved.

Processing apparatus · Rationalization of structures and methods
used until reaching· Study of other access routes than the one via RPV spare
RPV headnozzle (RPV thermal insulation and RPV head cutting method)· Regarding small hole opening of PCV and RPV head, perform element tests to assess the feasibilityof carrying out hydrogen degassing and cutting for prior check in a single work process.
· Perform preliminary tests to assess the applicability of AWJ to well cover hole opening as analternative.
· Perform element tests to study RPV thermal insulation hole opening and removal methods.

· Size reduction of the tool head device· Guide pipe vibration suppression· Improvement of cutting performance, positioning accuracy, andworkability
Processing apparatus· Study methods to maneuver around interfering objects in thefor the reactor core
reactor and to locate hole opening positions
internal structure· Design and develop devices based on the estimated condition
inside the reactor vessel· Development and design of devices and systems, andverification of their on-site workability· Install an injection reaction force receiving jig to reduce the deviation of the injection head fromthe target position due to the injection reaction force during cutting. Test the effect of the receiverwith element tests.
· Plan element tests for the hole opening of the steam separator and shroud head. Verify theconnected guide pipe linearity.
· Reexamine AWJ operation parameters. Confirm that the amount of abrasive could be reduced
from about 20 t to about 9 t by adjusting cutting speed and other parameters.
· In response to changes made in shroud head cutting parameters as the result of element tests,
design a new tool head. Attach an injection reaction force receiving jig, which concurrently serves
as a jig for processed materials collection.

· Improvement of the reachable range and maneuverability ofinvestigation equipment· Measures to improve visibility (image processing)· Develop investigation methods and devices that fit estimatedconditions in the reactor· Reflect on the outcomes of device development and design forreactor inside investigation in designing assess devices used forthe side-opening investigation· Perform an accessibility evaluation test as an element test and indicate the test result in thedesign of the investigation and access devices to complete the design work.
· Suspend the investigation equipment at a simulated height and test to capture a celestial-sphereimage (B2) and an around-view image B3). They were confirmed to be able to output a seamlesscomposite image without any problematic blurring.

Investigation system* See Equipment and Device List (No. 57) for investigation equipment B2 and B3.

©International Research Institute for Nuclear DecommissioningNo.346.4.1.1 Top-opening investigation method: Work cell
Implementation items

Rationalization of structures andconstruction methods considering
operability of each equipment

Implementation plan

Implementation Items and Results· Rationalize the work cell's design by reexamining its
structure and method from the viewpoint of minimizing work
time and radiation exposure to protect workers and thesurrounding environment from exposure during the
installation of the work cell, processing apparatus, andinvestigation equipment.

· Preparation for on-site works including penetrating
and investigation work and the organization of work
procedures for each operation such as toolbox
change (Reported)· Study ancillary systems required for the work cell(negative pressure control and monitoring systems).

Remarks· Plan device and equipment layouts taking into account· Organize required utilities and peripherals as well
Rationalization of device and equipment workers’ traffic lines around the work cell, and plan the layout as interface information for each device
layout plans in and around the work cell of utility supply systems according to the above-mentioned · Examine layout plans in detail.
method rationalization effort.
Clarification of installation methods andinterface conditions· Determine the available space for the installation of thework cell and seismic design conditions.

· Use the same target seismic strength as that for
PCV inside investigation for seismic design.
(Reported)

Detailed design of a negative pressure
control system for the work cell

· Study functional requirements for the work cell negative
pressure control system from a safety point of view andreflect the system specifications.

· Redundant design (dual system design) of theexhaust system in preparation for a failure(Reported)

Work cell

Airlock cell

A temporary facility to prevent contaminatedmaterials from spreading to the surrounding
environment, protect workers from radiation
exposure and provide devices with a safe
environment if by any possibility the PCV
boundary fails to function *Work cell

Equipment carry-in
entrance on the
airlock cell side
(Hatch in the airlock
cell ceiling)

Worker access door

Airtight
shutter

Equipment carry-in
entrance on the work cellside
(Hatch in the work cell
ceiling)

Worker access door

From the worker
access control room
to the entrance tothe work cell

Equipment carry-in
entrance on the
airlock cell side
(Hatch in the airlock
cell ceiling)

Airtight
shutter

Workeraccesscontrol room

Tool box

Transfer carrier* This is not a cell constructed to establish the primary boundary planned for fuel debris retrieval and other works.

Guide pipe

Movable shielding

Transfer carrier©International Research Institute for Nuclear Decommissioning6.4.1.2 Top-opening investigation method: Equipment for maintaining
boundary function
Implementation items

No.35

Implementation Items and Results

Implementation plan

Remarks· Rationalize the design of the boundary protection equipment by
Rationalization of structures and construction reexamining its structure and method from the viewpoint ofmethods in consideration of ease ofminimizing work time and radiation exposure to protect workers
and the surrounding environment from exposure during theconstruction
installation of the boundary guide pipe and toolboxes.

· Operating procedures and necessary functions werereviewed and organized for the transfer carrier, connection
mechanism, and gate valves in connection with toolbox
replacement. (Reported)· Improvement of the reliability of the· Evaluate the reliability of the improved boundary guide pipeboundary guide pipe sealing mechanism forsealing mechanism for negative pressure.
negative pressure· Determine a sealing mechanism applicable to negative
pressure through a preliminary test. (Reported)

Includingpreliminary
tests· Verify a temporary clamping method and necessary clamp
force through the gate valve and joint preliminary tests.
Verify the sealing performance (confinement · Feasibility verification of the gate valve
Including(Reported)
performance) of the joint between the· Evaluate the sealing performance of the connection mechanism · Perform preliminary tests on the connection mechanism in preliminary
terms of the up/down movement of its bellows, forced
boundary guide pipe and toolbox
between the boundary guide pipe and toolbox
tests
separation, and sealing performance, and confirm that thetargeted functions and performance can be achieved.

A temporary facility that allows thetransfer of processing apparatus andinvestigation equipment into the PCV
by extending the PCV boundary

Airlock cellWork cell

Boundary protection
equipment
Tool box

Tool box transfer carrier

Gate valve on thetool box side

Tool box
Tool box
Transfer carrier
Gate valve on theboundary guidepipe side
Boundary guidepipeGate valve on the boundary
guide pipe side

Connection part of PCV head
(Test in FY2017)

Boundary guide pipe

©International Research Institute for Nuclear DecommissioningNo.366.4.1.3 Top-opening investigation method: Processing apparatus (1) for
opening of RPV head and upper structures
Implementation items

Implementation plan

Implementation Items and Results

Remarks

Rationalization of structures andconstruction methods· Rationalize the work cell's design by reexamining its· Regarding small hole opening of PCV and RPV
structure and method from the viewpoint of minimizing work
head, perform element tests to assess thetime and radiation exposure to protect workers and thefeasibility of carrying out hydrogen degassing and Including element
tests
surrounding environment from exposure during the installation
cutting for preliminary survey in a single workof the work cell, processing apparatus, and investigation
process.
(Reported)
equipment.

Technology design to address issues
arose in the previous years andfeasibility study· Perform preliminary tests to assess the· Perform preliminary tests and element tests for technology applicability of AWJ to well cover hole opening as
Includingdesign and feasibility study to address issues that arose in the an alternative. (Reported)
preliminary tests
element tests and design work in the previous years andand element tests· Perform element tests to study RPV thermalreflect device design results.
insulation hole opening and removal methods.

Processing
apparatus

Hole-opening machines used to construct anaccess route into the reactor for investigationequipment

Well cover[Outlines of the penetrating of RPV head and structures above it]

PCV head

Structures to beprocessed

RPV thermal insulation

Specifications of the structures

Processing methods

Required hole diameter

Well coverMaterial: Reinforced concrete
Thickness: 618 mm (top), 610 mm(middle and bottom)

Core boring
AWJ (alternative)≥ φ750 mm

Steam dryer

PCV head

Material: Carbon steel
Thickness: 30 mm
Curvature: 8,347 mm

Small hole opening:
Mechanical cutting*Large hole opening: AWJ

Small hole: ≥ φ40
Large hole: ≥ φ550

Steam separator

RPV thermal
insulation

Material: SUS304, A3004P-0
Thickness: 0.7 mm/1.5 mm

AWJ≥ φ600RPV head(Spare nozzle
section)Material: ASTM A 533 Gr.B CL.1
Thickness: Min. 75 mm

Small hole opening:
Mechanical cutting*Large hole opening: AWJ

Small hole: ≥ φ40
Large hole: ≥ φ300

RPV head

Shroud headUpper grid plate* Pay attention to accumulated hydrogen when selecting a method.
©International Research Institute for Nuclear Decommissioning6.4.1.3 Top-opening investigation method: Processing apparatus (2) forprocessing the reactor core internal structures
Implementation plan

Implementation Items and Results

Tool head
Size reduction· Reduce the tool head's size by making it
foldable (using 600 mm-long pipes seriallyconnected with flexible joints) to retract it in
the work cell (tentative height of 4 m orless).

• Redesign the size and layout of the toolhead.
• Compare the new tool head design withthe current design, and examine its
feasibility.

Suppression of theguide pipe
vibration· Take the following measures to suppress
the tool head vibration: making the flexible
joints rigid, adjusting mechanism review,and detailed design for accuracy
improvement.
· Review AWJ cutting parameters(combination angle, position, etc.), upgrade
the machine, and stabilize the abrasive
feed rate (increase abrasive feed rate from
200 to max. 500 g/min) to improve theaccuracy of the diameter of bored holes
made by remote operation and to reduce
re-do work.
· Rationalization of remote operation andmonitoring tailored to the design of devices(the type of structure to be cut and methodof locating hole opening position)• Investigate guide pipe vibration factors
and study measures for improvement.
• Design parts based on the devised
measures and perform preliminary tests.

Sample production for element tests and testing

Structural design of devices

Implementation items

Improvement of
cutting
performance,
positioning
accuracy, andworkability

Methods tomaneuver aroundinterfering objects
in the reactor andlocate hole
opening positions
On-site workabilityof devices andsystems

Rationalization ofdevices based on
the estimatedcondition inside
the reactor vessel· Prototype the combined system of thetool head and the access device andperform partial mockup tests to evaluate
the remote operation, monitoring, andutility facility management.

· Design cutting and investigation work
steps (such as the location of structures tobe cut and hole opening locations anddiameters), and rationalize methods anddevices according to the ease of restriction
on the processed materials that is
produced and falls in the reactor during
cutting• AWJ cutting parameters were reviewed.
• Investigate factors to improve theabrasive feed rate stability.
• AWJ cutting parameters were optimized,
and parts were reselected or added to
improve abrasive feed rate stability.
• Install an injection reaction force
receiving jig to reduce the deviation of
the injection head from the target
position due to injection reaction force
during cutting. Test the effect of thereceiver with element tests.
• Plan element tests for the hole openingof the steam separator and shroud
head. Verify the connected guide pipe
linearity.
• AWJ operation parameters were
reexamined. Confirm that the amount ofabrasive could be reduced from about
20 t to about 9 t by adjusting cutting
speed and other parameters.
• In response to changes made in shroud
head cutting parameters as the result of
element tests, a new tool head was
designed. An injection reaction force
receiving jig, which concurrently serves
as a jig for processed materials
collection, was attached to it.

Remarks

Drumretracted in thetool box

No.37
Abrasive tankfor stable abrasive
feed to the tool headCompletedin FY2018
Includingpreliminary
tests

Access device
Guide pipe
for protection andpositioning of the abrasive
feed hoseCompletedin FY2019

Includingelement
tests

Total
length18 m

Total
length2m· Serial connection of 600 mmlong pipes(Flexible joint connection)· Suspended down to a depthof 18 m by remote control
Insertion and retraction (upand down)

Tool head
AWJ nozzle
to improve angle andposition accuracy, and thestability of high-pressure
water and abrasive feed rate

©International Research Institute for Nuclear Decommissioning6.4.1.4 Top-opening investigation method: Investigation system
Item

Implementation Items and Results

Implementation plan

Investigation equipment
prototyping, improvementof outreach range andmaneuverability of them

No.38

· Test the prototype samples to address issues that were found indesigned devices and preliminary tests in FY2017.
· Set the investigation equipment in the guide pipe dispensing andretracting equipment and evaluate the accessibility to the reactor coreinternal structures.

· Conceptual design was conducted in FY2018 to develop a horizontal
extension arm with increased extension range and a telescopic guide
Development ofpipe mechanism used to guide the new arm to expand the range ofinvestigation methods andinvestigation in the reactor core section. Design these two mechanisms
devices that fit estimatedin detail, build their prototypes, and evaluate their performance.
conditions in the reactor· Perform accessibility evaluation tests to the reactor core internal
structures.
· Evaluate image capturing performance in foggy conditions.
· Obtain a clear, blur-less image even if the investigation equipment
shakes due to its suspended condition. (Degree of the shake of the
Image capturing
investigation equipment should be larger than those for PCV inside
performance evaluation
investigation with proven records due to a longer suspension distance)· Development of technology to process captured images (such as acelestial-sphere image)Remarks· Design change was made to the whole part of the investigation equipment based on the
results of tests on the partial prototypes of the full investigation equipment B2 and B3, andprototypes were built. The accessibility to the reactor bottom (equivalent reaching a depth ofabout 26 m) and the prototypes’ ability to capture a celestial-sphere image and around-view
Includingimage were tested in the site-simulated environment with structure mockups.
preliminary tests· The configuration of the components of the guide pipe dispensing and retracting
and element tests
equipment (cable drum) was designed based on the result of noise tests with the use of slip
rings, and a single cable-drum style unit was prototyped. Noise tests were performed with it.
The influence of drum driving noise on the operation of the equipment was negligible
though the noise was mixed in image data. Ethernet signals required special slip rings.
· The design verification of the investigation and access devices was completed.
· A new horizontal extension arm with increased extension range was prototyped to expand
the range of investigation in the reactor core section. At the same time, a telescopic guide
Includingpipe and positioning mechanism suitable for the guiding and position control of the new arm
preliminary tests
was also prototyped.
and element tests· Investigation equipment C was able to be guided to a target location by combining thetelescopic guide pipe extended to the top of the upper grid plate and the horizontal
extension arm in the site-simulated environment with structure mockups.
· The investigation equipment for prior check (AHS/AHB) and full investigation(B1/B2/B3/B4) were mounted in the access device and tested to evaluate their image
Includingcapturing performance. (FY2018)preliminary tests· An image sharpening algorithm applicable to blurs caused by vibration was developed.
and element tests· Suspend the investigation equipment at a simulated height and test to capture a celestialsphere image (B2) and an around-view image B3). They were confirmed to be able tooutput a seamless composite image without any problematic blurring.

Positioning mechanism

Upper grid plateMax. about 12 m extendable tothe shroud head

Boundary guide pipe

Investigationequipment B2

Investigationequipment B3

Prototype of fullinvestigation equipment

Double-wheel cable drum

(The center of the upper grid plate was assumed tohave melted)

Telescopic mechanism(4-draw type)

Telescopic guide pipe and positioning
mechanism (for investigationequipment C)

Suspension device

Captured celestial-sphere image

PCV head

Horizontallyextendable length
2,200 mm

Investigationequipment
Horizontal extensionCarm withan increased extension range* See Equipment and Device List (No. 57) for investigation equipment AHS, B1, etc.

Image after sharpening
Original image
Image sharpening to compensate for blurring
caused by vibration©International Research Institute for Nuclear Decommissioning6.4.1.4 Top-opening investigation method: Investigation system - Improved prototypes No.39
of investigation equipment
φ95 mm(Investigation equipment B2)
Component function tests● Operation and performance tests of drive➢Cables were made thinner to fit in tiny spaces of the motion
mechanism, and no noises were mixed in video image data or sensor
signals.
➢The cables in the devices moved smoothly in response to the tilt andpan motion.
● Ability to retract the mechanism in case of failure (Effect of slip
clutch)➢The mechanism could be retracted by allowing the link mechanism toslip by an external force when the tilt motion couldn’t be activated.
Visibility evaluation● Image-capturing performance was tested in foggy conditions.

Design and prototyping in FY2019
Prototype of the whole mechanism● Addition of stretchable light mounting arms
➢A slip clutch was installed in the link mechanism of thelight mounting arms in addition to the tilt link mechanism
so that the arms could be folded during the investigationequipment retraction operation even if the motor failed.
● Prototype of control system➢The tilt and pan angles could be kept within ±0.5° (target
is ±1.0°) of intended angles by using acceleration anddeceleration control to suppress the vibration of thedevices.
➢An automatic remote control that links to the operation of
the celestial-sphere image capture system was developed.

835 mmPrototyping and evaluation in FY2018

Tilt rotationfrom 0°(vertical)
to 110°

Position during up
and down
movement

Stretching arm
lightsStretchable
arm lights

Panrotation±180°

Tilted at 90°
Hole diameter φ110 mm

Guide pipe retraction

Tilted at 90°, light
mounting arms stretched

The tilted head is pushed
down to a vertical position
as it goes through the hole.

Stretched light mounting
arms are folded as theygo through the hole.

Getting
through thehole

The installation of slip clutches made it possible for the investigation equipment
to be folded and straightened due to slippage caused by structural forces whenpulled up. Thus, they could be safely retracted in case of failure or malfunction.
©International Research Institute for Nuclear Decommissioning6.4.1.4 Top-opening investigation method: Investigation system
No.40: Improved prototypes of investigation equipment (Investigation equipment B3)
φ95 mmPrototyping and evaluation in FY2018

Image pick-up
tube
Swivel unit
Pan rotation
motor added

683 mmFunction verification of mechanism configuration● Operation and performance tests of drive➢The cables in the devices moved smoothly in response to
the pan motion of the mechanism.
➢The friction resistance of the sealing used in the panrotation mechanism increased about threefold (to 1.2 Nm)
when the mechanism was not operated for a long time.
The original design was to utilize the swivel unit of theimage pick-up tube mounted in the device. Increased
friction resistance could cause insufficiency in driving
torque.
Visibility evaluation● Image-capturing performance was tested in foggy
conditions.

Sealing used in
the pan rotation
mechanism

Range of panrotation ±180°

Design and prototyping in FY2019● Increase of pan motor torque➢Stable pan rotation was achieved by installing an additional
pan motor and doubling the drive torque to 2.6 Nm.

Side-viewing lightImage
pick-uptube● Prototype of control system➢The same control unit as the one for investigation equipment
B2 was adopted. An automatic remote control linked to theoperation of the around-view image capture system wasdeveloped.

Side-viewing window(The front view canbe obtained bymirror tilt operation)

Prototyping in
FY2018

Prototyping in
FY2019Front-viewing light

Front-viewing direction©International Research Institute for Nuclear Decommissioning6.4.1.4 Top-opening investigation method: Investigation system - Improved prototypes
No.41
of investigation equipment (Investigation equipment C) Configuration of the accessequipment with the horizontal extension arm
Boundary· Moving up/down and unfolding the horizontal extension
arm and moving up/down investigation equipment C
Guide the horizontal extension arm andinvestigation equipment C to under the
shroud head by extending the telescopic
guide pipe in the boundary guide pipe fromthe PCV head section and unfold thehorizontal extension arm to send theinvestigation equipment to the wide area ofthe reactor core.
Double-wheel
cable drum

Telescopic guide pipe 12,400 mmrθ positioning
mechanism· Controlling the position of the telescopic guidepipe in the boundary guide pipe in a radial
direction and axial angle· Guiding the horizontal extension arm through the holein the shroud head by the CFRP-made 4-draw
telescopic guide pipe
Telescopic guide pipe

Boundary
Guide pipe

Shroudheadrθ positioning
mechanism

Unfolding

guide pipe

r-adjustment
θ adjustment
Seated on thering at thebottom end of
the boundary
guide pipe
Hole in the
PCV head

Telescopic guidepipeOperation sequence of investigation equipment C
deployment and retraction
The operation sequence shown below is required to pullout investigation equipment C from the horizontal
extension arm and hang it at the arm's front tip. The same
sequence is taken for retraction.
Extension

Telescopic
guide pipe

Swivel motion
Pullout

Steam dryer bottom
plate (Φ200 hole)

Shroud head

Extension(Φ110 hole)
Horizontal
extension arm
Investigationequipment C(Image pickup tube)

Suspenddown

Investigationequipment C

Housed in the telescopic guide pipe, unfolded after passing
through the opening of the shroud head, and sending
investigation equipment C to a wide area in the reactor©International Research Institute for Nuclear Decommissioning6.4.1.4 Top-opening investigation method: Investigation system – Improved prototypes No.42
of investigation equipment (Investigation equipment C) Horizontal extension arm
RPVMaximum outreach range

Design in FY2018

Horizontal extension
arm downward position
1,180 mmConceptual design of the structure● The objective is to increase the extendable
length of the horizontal extension arm toexpand the outreach range of investigationequipment C (1,180 mm in the FY2017
design).
➢A three-part folding mechanism was adopted
for the horizontal extension arm.

2,200 mm

Design in FY2017

Design in FY2018 to 2019

Φ90
Swivel mechanism

Design and test manufacturing
in FY2019

Horizontal extension arm suspension wire
Shroud headbottom surface

1,218

1,812

Detailed structure design and test manufacturing,
including the control systems➢The detailed design and test manufacturing of theextension arm was completed, and its extendable
length was increased to 2,200 mm.
➢Stand-alone unit tests and accessibility evaluation
tests were conducted.

Cable of investigation equipment
C
Investigationequipment C(Image pickup
tube)

Extensionarm hinge

1,044
2,200
Extendable length: 1,044 to 2,200

Shape during descent

Extended state of the extension arm©International Research Institute for Nuclear Decommissioning6.4.1.4 Top-opening investigation method: Investigation system – Improved prototypes
No.43
of investigation equipment (Investigation equipment C)
2,200 mmHorizontal extension arm
850 mmUnit testing for functional verification

Test item

What to test

Folding/unfolding operation(Cables are routed
manually)· 0° to 90° folding/unfolding
operation· Investigation equipment C up–down
operation

The arm was confirmed to work as
designed, and the operation
sequence was determined.

Extension and contractionof the extendable arm(Cables are routed
manually)· Extension and contraction in the full
extension range of 2,200 mm· Examination of the hinge angle
range where the full extension of thearm is possible· It was confirmed that the arm could
be fully extended (2,200 mm) when
the hinge angle was within 60° to
90°.
· Contraction was possible regardlessof the hinge angle.

±180° swivel motion by
the swivel mechanism· ±180° swivel motion

The mechanism was confirmed towork as intended. It was determined
to operate at a rate of 0.3°/s tosuppress shaking.

10-m-long up–down test to
simulate access to thereactor bottom (withmanual cable operation)· Up–down test with a 2 kg weight tosimulate the weight of a 10-m cable· Examination of the hinge angle
range where the full extension of thearm is possible

Hinge angle of 90°

RPV

Horizontal extension arm
suspension wire

<Purposes>
To verify the following performances of the horizontal extension arm: folding/unfolding andextending/contracting operation; the ability to pull out investigation equipment C and suspend andmove it up–down with a weight load equivalent to the weight of sling necessary to reach the reactor
bottom; and its rigidity required to perform a stable swivel motion with the arm unfolded and extended

Cable of investigationequipment C

Test results

Accessible
range
Extensionarm hinge

Extension arm

Investigationequipment C
Horizontal extension arm test system

Achieved investigationequipment accessible range
with the new horizontal
extension arm(10-m-long suspension)
The range with a yellow fill is investigatedusing investigation equipment B.

· It was confirmed that up-down could
be performed without problem when
the hinge angle was within 55° to90°. (850- to 2,200-mm range in the
top right figure)

Hinge angle of 60°(Highest tilt position)

Fully extended arm (to 2,200 mm) with different tilt angles

Operation sequence of the deployment of investigation equipment
C©International Research Institute for Nuclear Decommissioning

Investigation system

Processing apparatus

6.4.1.5 Top-opening investigation method: Element test plan
(Reported)

No.44

Test item

Purposes and reasons

Test outline① Test to evaluate theon-site workability of
PCV/RPV head smalldiameter penetratingmachine(Reported)

A small-diameter (φ10 mm) penetrating machine for degassinghydrogen from the upper part of S/C was tested in the element tests
conducted in another project* in FY2017. The feasibility of carryingout penetrating for hydrogen degassing and penetrating forpreliminary surveys (φ40 mm) together in a single work process isevaluated to streamline the construction method.

Conduct penetrating tests of simulated PCV head and RPV head with the preliminary prototype of thepenetrating machine to obtain the following information:· Feasibility of penetrating a hole of φ40 mm or larger in the PCV/RPV head
· Information that helps develop methods to support the reaction force and suppress vibration duringpenetrating and to determine their specifications② Test to evaluate theon-site workability of the
RPV insulator holeopening and removal
machine(See slide No. 45)

The feasibility of measures to address the issues found in the test in
the past FY (separation and fall of insulator during processedmaterials collection, abrasive accumulation in the tool swivel
mechanism, and tool inclination during offset operation) is evaluated.
In addition, the feasibility of the insulator removal method (φ570-mm
hole opening) is evaluated in response to the enlarged hole-opening
diameter after access route review in FY2015.

Open a through hole in the simulated insulator and remove it with the preliminary prototype of theprocessing apparatus to obtain the following information:· Information that helps develop a measure for preventing cutting scraps from falling during hole
opening and determine its specifications· Feasibility of the insulator removal method· Information that helps develop a measure for preventing abrasive from accumulating in the tool
swivel mechanism and determine its specifications· Information that helps develop a measure against tool inclination during offset operation anddetermine its specifications③ Test to evaluate theon-site workability of thereactor core internal
structure processing
apparatus(See slides No. 46 to 48)(1) Hole opening in thesteam separator

The validity of measures to address
the issues found in the test in the past
FY (vibration of the pipe sling anddecrease in abrasive feed rate) andthe feasibility of cutting work
parameters revised to reduce theprocess time are evaluated.

Open a through hole in the simulated steam separator with the prototype of the processing apparatus toobtain the following information:· Vibration amplitude of the pipe sling· Abrasive feed rate
· Feasibility of φ160-mm hole opening· Occurrence of cutting scraps falling into the inside of the steam separator· Process time(2) Hole opening in the
shroud head

The feasibility and validity of measures
to address the issues found in the testin the past FY (hole diameter not large
enough) are evaluated.

Open a through hole in the simulated shroud head with the prototype of the processing apparatus toobtain the following information:· Interference of the surrounding structures with the tool head
· Feasibility of φ110 mm or larger hole opening· Feasibility of the collection of the shroud head cutting scraps④ Performance tests of
the investigationequipment guiding
system(See slides No. 49 to 54)

The performance of the improved investigation equipment A and B
guiding system is evaluated with a focus on how the strength of thecables against bending stress is improved and how the reliability ofhinges is improved. The performance of the investigation equipment
C guiding system is evaluated with a focus on the extension andretraction operation of the telescopic mechanism and smooth guidingof the device through holes.

Conduct tests to guide the investigation equipment by remote control using videos through holes created ina test mockup at simulated locations and with simulated sizes along simulated interrupting factors, such as
the surface condition of the inner wall, to obtain the following information:· How smoothly the investigation equipment can be guided through the holes (investigation equipment A,
B, and C).
· Extension and retraction operations of the telescopic mechanism (investigation equipment C)⑤ Test to evaluate thevideo capturingperformance of theinvestigation system(investigation system B)(See slides No. 51 to 52)

The image capturing performances of investigation equipment B2(with a pan and tilt mechanism) and investigation equipment B3 (witha pan mechanism and tilt mirror) are evaluated with a focus on theability to output a seamless celestial-sphere image (investigationequipment B2) and horizontal 360°-view image (investigationequipment B3) and the influence of the shaking of the device causedby the up–down motion on the image quality.

Conduct tests to move investigation equipment B2 and B3 up and down near image-capturing locations andcapture images according to the planned procedures to obtain the following information:· Accuracy of celestial-sphere images (B2) and horizontal 360°-view images (B3)
· Time needed to capture an image including waiting time for device shaking to diminish*: Development of the PCV leak repair technology©International Research Institute for Nuclear Decommissioning6.4.1.5 Element tests for the top-opening investigation method② Test to evaluate the on-site workability of the RPV insulator
hole-opening and removal machine<Purposes>
Open a through hole in the simulated insulator and remove it with the preliminary prototype of theprocessing apparatus to obtain the following information:· Information that helps develop a measure for preventing cutting scraps from falling during hole
opening and determine its specifications· Feasibility of the insulator fixing, fitting, cutting, and removing method· Information that helps develop a measure for preventing abrasive from accumulating in the tool
swivel mechanism and determine its specifications· Information that helps develop a measure against tool inclination during offset operation anddetermine its specifications<Test item>
Tests are conducted under the following two conditions:· Without offset (no offset between the axis of the guide pipe and the center of the RPV spare nozzle
flange)· With an offset of 100 mm (100-mm offset between the same axis and the center)<Cutting the fixing bracket><Test system>
Boundary guidepipe simulant
Crane hoist

PCV head simulant

Camera image
monitorControl panel forprocessing apparatus<RPV insulator removal>

No.45

RPV insulator
simulant<Test results and things to be considered in detail in the design>· The fixing bracket was able to be cut and grabbed for removal regardless of whether the 100-mm offset is used.
· The remote operability of the thermal insulation penetrating and processing apparatus needs to be further improved by downsizing, adding more cameras, etc., as thiswork needs to be performed in a very narrow space by remote control.
· There were two ideas to leave the pieces of the cut and removed thermal insulation near its original location: keep them in a side-lying position or in a standing
position. The two positions were tested and were found to be feasible. Which position to take will be determined based on the burden of workers that will be known
through the skill training of the workers for the remote operation.
©International Research Institute for Nuclear Decommissioning6.4.1.5 Element tests for the top-opening investigation method

No.46③ Results of the element tests to evaluate the on-site workability of the reactor core internal structure processing
apparatus: (1) steam separator hole opening ①<Purposes>
Testing the validity of the measures to address the issues found in the test in the past FY(vibration of the pipe sling and abrasive feed rate decrease) and the feasibility of cutting
work parameters revised to reduce the process time
<Evaluation items>
Open through holes in three types of simulants (flat-plate, steam separator upper part,and steam separator lower part) with the prototype of the the reactor core internal
structure processing apparatus to obtain the following information:· Vibration amplitude of the pipe sling due to AWJ injection· Abrasive feed rate
· Feasibility of φ160-mm hole opening· Occurrence of cutting scraps falling into the inside of the steam separator· Process time
<Test results>: Flat-plate test piece cutting test
The maximum vibration amplitude of the tool head due to the reaction force of theinjection was determined to be about 60 mm and was found to exceed the criteria in thetest of cutting the flat-plate test piece placed at about the same height as the steam
separator by AWJ.
⇒ As a measure for it, an injection reaction force receiving jig was added at the tip of thetool head.

Tool head

Injection reaction force receiving jig

The injection reaction force
receiving jig is inserted in the
gap formed in the center of thethree cylinders of the steam
separator, so that the axis of
the tool head is aligned with thecenter of the three cylinders,
and the outer surface of thesteam separator cylinder
supports the reaction force via
the receiver.

The reactor coreinternal structure
processing
apparatus

AWJ nozzle
Pipe sling fixture

Flat-plate test piece

Cutting the flat-plate test piece
Mockup support cradle

Approx. 30 mm

Approx. 60 mm

Steam separator
upper part
Steam separator
lower part

Shroud head

Planned cutting lines

Result of the flat-plate test piece
cutting test
Test system©International Research Institute for Nuclear Decommissioning6.4.1.5 Element tests for the top-opening investigation method

No.47③ Results of the element tests to evaluate the on-site workability of the reactor core internal structure
processing apparatus: (1) steam separator hole opening ②<Test results>: Results of steam separator upper and lower part simulants cutting tests
Evaluation
items

Results

Vibration
amplitude of thepipe sling due to
AWJ injection

Cutting work was done as planned without leaving any uncut part, and thecut edge surface exhibited a roughly uniform condition. Based on thisresult, it was confirmed that the vibration of the tool head was suppressedenough to create a hole in the steam separator with sufficient quality.

Abrasive feedrate

Cutting work was done as planned without leaving any uncut part, and thecut edge exhibited a smooth and uniform surface. Based on this result, it
was confirmed that the abrasive feed rate was kept constant enough tocreate a hole in the steam separator with sufficient quality.
(Abrasive feed rate in the test: 589 to 703 g/min)Feasibility of
φ160-mm hole
opening

It was confirmed that a hole with a diameter of ≥φ160 mm was created byinserting a cylinder with an outer diameter of 160 mm through the opened
hole.

Occurrence of
cutting scraps
falling into theinside of thesteam separator

Although cutting scraps were found to fall into the inside of the steam
separator, the size of all the pieces was less than 16 kg, which isconsidered to pose a moderate risk of a criticality event due to fuel debris
even if they reach the reactor core.

Process time

Based on this test result, the total hours necessary to open a hole in thesteam separator (AWJ injection time) was estimated to be about 228 h,which is 70% less than that estimated from the FY2017 test result (702 h).
The total required abrasive was estimated to be about 9 t, which is about
60% less than that obtained from the FY2017 test result (about 21 t). The
amount can be further reduced by optimizing the parameters.

The cut edge
surface waswaving.

Uncut part
remains.

The cut edge
surface wassmooth anduniform.

The cut edge surface tested in
FY2017 (example)

The Cut edge surface tested
in FY2019 (example)

φ160-mmcylinderMeasurement of the holediameter

Falling cutting scraps foundinside the steam separator(example)©International Research Institute for Nuclear Decommissioning6.4.1.5 Element tests for the top-opening investigation method

No.48③ Results of the element tests to evaluate the on-site workability of the reactor core internal structure
processing apparatus: (2) Shroud head hole opening<Purposes>
The feasibility and validity of the measures to address the issues found in the test in the past FY (hole diameter notlarge enough) is evaluated.

AWJ nozzle<Evaluation items>
Open a through hole in the shroud head simulant with the prototype of the the reactor core internal structure
processing apparatus to obtain the following information:· Interference of the surrounding structures with the tool head
· Feasibility of φ110-mm or larger hole opening in the shroud head
· Feasibility of the collection of the shroud head cutting scraps<Test results>➢An injection reaction force receiving jig with a different shape from the one used for the steam separator was
attached to the tip of the tool head and then tested. No interference of the surrounding structures (stand pipe) withthe tool head was observed.
➢Since the hole opened in the shroud head mockup was not as large as φ110 mm, the cutting parameters werechanged, and cutting was retried. As a result, opening a φ110-mm or larger hole was confirmed to be possible.
➢The feasibility of collecting the shroud head cutting scraps was also confirmed.
➢It was decided to add the injection reaction force receiving jig to the tool head and reflect the changed cutting
parameters to the tool head design.

Tool head

φ110-mmcylinderShroud headcutting scrap

Cutting scrap
collection jig

Injection
reactionforce
receivingjigStand pipe simulants

Appearance of the shroud head after
cutting

Injection
reactionforce
receiving jig
Injection reaction force receiving jig
for the shroud head cuttingStand pipe simulants

Shroud head cutting scrap

Shroud head hole diametermeasurement©International Research Institute for Nuclear Decommissioning6.4.1.5 Element tests for the top-opening investigation method

No.49④ Maneuverability evaluation test of the investigation equipment(investigation equipment ALS)
<Purposes>
The maneuverability of the investigation equipment is evaluated after adopting a new cable with an improved flexibility (through theuse of a flexible sheath tube and its jacket as well as a flexible industrial endoscope cable) for the purpose of improving
maneuverability. Evaluation tests are conducted in combination with the use of the prototype of the cable drum.

Weight notrequired

Weight
1.4 kg<Test results>➢It was confirmed that the investigation equipment was accurately located right above the target small hole (φ40 mm) and guided through it
without getting stuck by remote control. Especially, the ability to pass through a long hole (in the well cover) was improved.
➢The shaking motion of the investigation equipment during position adjustment (at a horizontal travel speed of 1mm/s) increased more than
before the improvement due to the adoption of a flexible cable. Despite this adverse effect, the horizontal travel speed of the investigationequipment guiding system was concluded to be adequate since all the device guiding tests through different holes were successful and afurther decrease in the speed would make it difficult to determine a traveling direction from the change of the captured videos.
➢The investigation equipment was also able to pass through the hole without problems during the retraction operation even if the guiding
system was operated to intentionally cause the investigation equipment to get stuck at the hole.
Investigation step

What to test

Test results

Preliminary survey of thearea under the well cover(PCV head)

Ability to guide the investigationequipment to the center of thethrough hole with the smallest
diameter (φ40 m) and thelongest length (618 mm) andthrough the hole

Although the investigation equipment got caught
at the edge of the hole when inserted into the hole,
the position was adjusted with the assistance ofthe videos it captured. The investigationequipment had often hit the inner wall of the holeand got stuck in it due to the insufficient flexibilityof the sheath tube. After improvement, it was
confirmed that it could smoothly pass through thehole. The round-trip travel time is about 15 min.

Preliminary survey of thearea under the steam
dryer bottom plate (above
the steam separator)
Investigation of the area
between the outside of thesteam separator and the
shroud head

Ability to guide the investigationequipment to the center of the
φ40-m through hole located at
the lowest position and throughthe hole

It was confirmed that the investigation equipment
was moved down about 18 m, located at the rightabove the hole, guided through the hole. It did not
get stuck in the hole at all. The round-trip travel
time is about 25 min.

Ability to guide the investigationequipment to a narrow areasurrounded by the barrels of thesteam separator and connection
bars and through the area

It was confirmed that the investigation equipment
was guided to the shroud head through theoutside of the steam separator after its position
was adjusted to be above the steam dryer, rightabove the bottom plate, and right above theconnection bars of the steam separator. The
round-trip travel time is about 45 min.

Investigationequipment
ALS

Deviation of
80 mm the tip position 21 mm
Before improvement
After(Weight did not help improve
improvement
the maneuverability due to alarger deviation)

BarrelConnection
bars

BarrelStand pipe
Investigation of the area under thesteam dryer bottom plate (above
the steam separator)

Investigation equipment passing
through the area under thesteam separator barrel©International Research Institute for Nuclear Decommissioning6.4.1.5 Element tests for the top-opening investigation method

No.50④ Maneuverability evaluation test of the investigation equipment (investigation equipment
ALB/AHB: intermediate flexible link mechanism)<Purposes>
The maneuverability of the improved investigation equipment ALB/AHB is evaluated.
Investigation equipment ALB: The flexibility of the industrial endoscope cable was increased. The weight at the tip was downsized by the material change
Investigation equipment AHB: The weight is increased by changing the material of the housing to gain more thrust by gravity force.

<Test results>➢It was confirmed that both investigation equipment ALB and AHB were guided toward the shroud headthrough any one of the three steam separator cylinders located near the hole opened in the steam dryer
bottom plate. It was also confirmed that they could be guided through the narrow swirler section without
getting stuck.
Investigation step

What to test

Test results

Approach to the hole in
the upper part of thesteam separator

Guiding the investigationequipment through thehole in the upper part ofthe steam separator using
the operation of theintermediate flexible linkmechanism

Investigation equipment ALB: It was confirmed that theinvestigation equipment was guided through the target hole bypointing it toward the target hole using the flexible linkmechanism and moving it close to the hole using the XY
positioning mechanism.
Investigation equipment AHB: It was confirmed that theinvestigation equipment was guided through the target hole bypointing it toward the target hole using the flexible linkmechanism without the help of the XY positioning mechanism.
The round-trip travel time from the tool box is about 15 min forboth ALB and AHB.

Maneuvering through thegap and swirler in thesteam separator using theintermediate flexible linkmechanism and cable
drum

Investigation equipment ALB: The tip of the investigationequipment was inserted into the opening of the swirler without
getting stuck after maneuvering around a gap, taking advantageof the front-end bending motion of the industrial endoscope.
Investigation equipment AHB: Although this device does nothave a front-end bending mechanism, the tip of the investigationequipment was inserted into the opening of the swirler without
getting stuck by shaking it using the intermediate flexible linkmechanism while guiding it.

Maneuvering throughthe inside of the steam
separator (internal gap
and swirler)

From the investigationof the area under the
shroud head (reactorcore) to withdrawal

Guiding to the reactor
core and withdrawal fromthere by the cable drum

Investigation equipment ALB: It was confirmed that theinvestigation equipment was deployed and withdrawn without
getting stuck. The round-trip travel time from the top of thesteam separator to the reactor bottom is about 50 to 55 min.
Investigation equipment AHB: The same as above The
round-trip travel time along the abovementioned route is about
50 min.
* When the investigation equipment was suspended outside
the simulation scope of the upper grid plate and core support
plate, tests were conducted within a reachable range.

* Camera video: Separately provided cameras were used to capture the overall view of the device position control as investigationequipment ALB only outputs the videos of industrial endoscope, and the fiber scope of investigation equipment AHB is a structural
dummy.

Intermediate
flexible linkmechanism

Hole in theupper part ofthe steamseparator

WeightInvestigation equipment ALB

Investigation equipment AHB

Investigation equipment being guided to the hole in the upper
part of the steam separator

ShakingmotionGuiding down to the position
above the swirler

Shaking using the intermediate
flexible link mechanism while
guiding down to the opening

Suspenddown

Guiding the tip into the
opening of the swirler

Investigation equipment (AHB) being guided into the hole of theswirler of the steam separator* Investigation equipment ALB can be guided into the hole of the swirler without theshaking motion by the front-end bending mechanism.

©International Research Institute for Nuclear Decommissioning6.4.1.5 Element tests for the top-opening investigation method

No.51④ Performance tests of the investigation equipment guiding system (investigation equipment B2/B3)⑤ Test to evaluate the video capturing performance of the investigation system (investigation equipment B2/B3)<Purposes>
The maneuverability of the investigation equipment guiding system is evaluated using the prototypes of the investigation equipment and the cable drum in combination. In addition,
the tests to create celestial-sphere images (B2) and horizontal 360°-view image (B3) are conducted to evaluate the influence of the shaking of the device on the image quality andtime needed to capture images, including the waiting time for the device shaking to stop.
<Test results>➢It was confirmed that the investigation equipment were guided through each hole by the control of the guiding system assisted by videos captured by themselves. It was
confirmed that the investigation equipment was released from the get-stuck condition in the hole by operating the guiding system using the videos captured by itself, which
provide information on the occurrence of the get-stuck event and what part of the device had been caught from the inclination of videos.
➢It was confirmed that none of the up–down movements, XY positioning, and pan/tilt operations of the guiding system caused shaking of the investigation equipment, which
adversely affected the guidance of the devices to the holes or the creation of composite
panoramic images.
Investigation
step

What to test

Test results

Detailed
investigation of
the area under
the RPV head

Celestial-sphere image andhorizontal 360°-view image
capturing performance,
including the influence of thedevice shaking

B2: The round-trip travel time from the tool box isabout 25 min.
Celestial-sphere image capturing: about 140min
B3: The round-trip travel time from the tool box isabout 20 min.
Horizontal 360°-view image capturing: about
60 minReactor coresection (under
the upper gridplate)
Detailed
investigation

Celestial-sphere image andhorizontal 360°-view image
capturing performance,
including the influence of thedevice shaking under theupper grid plate

B2: Celestial-sphere image capturing: about 150min
B3: Horizontal 360°-view image capturing: about
60 minDetailed
investigation of
the area under
the core support
plate

Celestial-sphere image andhorizontal 360°-view image
capturing performance,
including the influence of thedevice shaking above thecore support plate

B2: The round-trip travel time from the tool box isabout 65 min.
Celestial-sphere image capturing: about 130min
B3: The round-trip travel time from the tool box isabout 50 min.
Horizontal 360°-view image capturing: about
60 min

XY positioning
mechanism
Single cable
drum

Investigationequipment B2

Φ140-mm hole

Access device

Investigation equipment passing throughthe hole in the steam dryer bottom plate(Investigation equipment B3)

Φ110-mm hole

· The slight shaking motion of investigation equipment B2 caused by its pan/tilt operation
lasted less than 1 min and was considered to be negligible for the creation of composite
panoramic images.
· No shaking motion was caused on investigation equipment B3 by its pan and mirror tilt
operation.
<Number of captured images>
Celestial-sphere image: 276 images, horizontal 360°-view image: 126 images (for theheight range of 1.25 m)

Investigation equipment B2 with its
pan/tilt mechanism activated andstretchable light arms fully extended after
passing through the hole in the shroud
head

Upper gridplate

Shroud head hole
opening
Video captured by investigationequipment B3 while it was passing
through the hole in the shroud head©International Research Institute for Nuclear Decommissioning6.4.1.5 Element tests for the top-opening investigation method

No.52④ Performance tests of the investigation equipment guiding system (investigation equipment B2/B3)⑤ Test to evaluate the video capturing performance of the investigation system (investigation equipment B2/B3)
Created composite around the view image
North
side
West side

BottomNorth side

South side

Enlarge
Ref: Typical camera
image

East
side

Images used to create the composite image

East side
Created composite celestial-sphere image

South
side

Created composite around the view image (investigation equipment B3):
Under the upper grid plate
Outlines ofthe mockup

Bottom

West
side

West
side

East
side Bottom
Approx. 2 m

Enlarged composite celestial-sphere images
Created composite celestial-sphere images (investigation equipment
B2): Under the upper grid plate

Investigation equipment B2 test

Viewed from the center of the mockup The mockup
was covered by blackout curtains, and cloth with rustsimulating pattern printing was put on the inner walls.

Test environment

It was confirmed that no shaking motion occurred in the investigation equipment, and seamless composite panoramic images were obtainedeven if the pan/tilt mechanism of the investigation equipment was in operation.
©International Research Institute for Nuclear Decommissioning6.4.1.5 Element tests for the top-opening investigation method④ Performance tests of the investigation equipment guiding
system (investigation equipment C)

Boundary
Guide pipe
Simulantsrθ positioning mechanism

1. Telescopic guide pipe extension and retraction tests<Purposes>
The ability of the guiding system to guide investigation equipment C through the holes in
the reactor core internal structures to the top of the upper grid plate by relying on videos
captured by investigation equipment C and information shown in the operation panel
about the axial positions of all involved devices is tested. Tests were conducted, startingfrom the condition where the rθ positioning mechanism was seated.
<Test results>
Test item

What to test

Test results

Ability to guideinvestigationequipment to thereactor coreinternal structures① Going through φ200
opening in the steam
dryer bottom plate② Going through φ140
opening in the barrel ofthe steam separator③ Going through φ110
opening in the shroud
heads(iv) Reaching the top of theupper grid plate⑤ Telescopic guide pipe
positioning· It was confirmed that the guiding system wascapable of guiding the investigationequipment through all the holes and locating it
at target positions.
· It was confirmed that the telescopic guidepipe position adjusting mechanism could be
operated accurately using the information on
the positional relationship between the guidepipe and the hole shown in the videos.
· The process time from the start of thetelescopic guide pipe positioning to the arrivalof its front end at the top of the upper gridplate was about 30 min.

Is it possible to detect theoccurrence of the gettingstuck event of the telescopic
guide pipe and recover thetelescopic guide pipe by
relying on videos captured byinvestigation equipment C?

· It was confirmed that detection of the event
was possible using the videos, regardless ofwhen it occurred (i.e., during the extension or
retraction), as investigation equipment C
travels inside the telescopic guide pipe. (Theinner wall of the telescopic guide pipe needs
to be in the viewing field.)· It was confirmed that a get-stuck event was
not likely to occur during the extension
because the play of the telescopic
mechanism provided flexibility to its
movement.
· It was found that the shape of the fitting at the
tip of the telescopic guide pipe needed to bechanged as it could get stuck during theextraction. It took time to recover from thecondition due to the lack of information on thelocation of the contact point between thefitting and the structure.

Test to detect andrecover from aget-stuckcondition

No.53

Double-wheel cable
drum

Telescopic
guide pipe

Seating position
Hole in the
shroud head

Telescopic guide pipe

Opening

Test system for the investigation equipment
C guiding system
Opening in the upper
part of the steam
separator barrel

Investigationequipment C

Horizontal extension
arm bottom end

Half-unfolded horizontal
extension arm
Fitting at the tip of the telescopic guide pipe
(for hooking and pulling up upper pipes)

Inner wall of the telescopic guidepipe at its bottom end

Video captured byinvestigationequipment C

Passing through thehole in the steam
separator barrel

Hitching position©International Research Institute for Nuclear Decommissioning6.4.1.5 Element tests for the top-opening investigation method

No.54④ Performance tests of the investigation equipment guiding system (investigation equipment C)
2. Horizontal extension arm unfolding/extending and investigation equipment C suspention test
<Purposes>
The ability of the guiding system to control swivel, unfolding, and extending motions and guide investigation equipment C to the target cell of the upper grid plate is tested. In
addition, the ability of the guiding system to release investigation equipment C from a get-stuck condition at the upper grid plate by solely relying on videos captured by thedevice itself is tested. Note that these tests are conducted using only the horizontal extension arm from the dimensional constraints of the simulated structural environment.

Horizontal extension arm position<Test outline>➢Test to evaluate accessibility to the upper grid plate
Place investigation equipment C on the upper grid plate simulant at the start position in the Start
figure; then, lift it, move to position ①, and down it there. Repeat these steps along thepositionarrows presented in the figure until the position is reached ⑥. Two upper grid plate
simulants were placed along the 0° line (for horizontal extension/retraction operation) and
45° line (for combination operation of extension/retraction and swivel) as presented in Figure(b). The test was conducted in darkness to simulate the site environment, and the guiding
system was operated using only videos from investigation equipment C.
➢Recovery test from the get-stuck condition at the upper grid plate
Cause investigation equipment C to get stuck at the upper grid plate intentionally during theretraction operation and test the ability of the guiding system to locate the contact point andrelease the device from that condition by relying on videos captured by the device.

Investigation equipment
C0°
direction45°
direction(a) Investigation equipment C descentprocedures<Test results>
Test item

What to test

Test results

Test to evaluate
accessibility to theupper grid plate(Cables are routed
manually)

Is it possible to guideinvestigation equipment
C to each target cell by
relying only on videos
captured by itself?

It was confirmed to be possible to guide it to eachtarget cell. The upper and side surfaces of the gridplate could be used as navigation information. The
process time to move from a cell to the one next to it
is about 5 to 6 min.

Upper grid plateGet-stuck condition
recovery test
(Cables are routed
manually)

Is it possible to detect
and recover from a getstuck condition by relying
only on videos captured
by investigationequipment C?

It was found that the occurrence of the get-stuck
event with investigation equipment C could be
detected by the captured videos, but it could not bereleased from that condition, as the get-stuck event
did not change the position of the device, so that
information on the location of the contact point
between the device and the grid was not available. It
was decided to prepare a support tool that displays
the location of the investigation equipment based on
the axial positions of all the involved devices for theguiding system used for the investigational works at
the site. It was found that the connector of theinvestigation equipment caused a get-stuck event. It
was confirmed that changing the connector design toa tapered shape could prevent it.

(b) Layout of upper grid plate simulants

Portions to cause
a get-stuck event Tapered shape

Darkness

Upper grid plate
Simulants
Investigationequipment C

Shape improvement ofinvestigation equipment
C

Guiding system performance test
©International Research Institute for Nuclear Decommissioning6.4.1.6 Top-opening investigation method: Specifications of equipment - Parameters
for water volume to be used in abrasive and cutting works (rough estimate)
Required holespecifications

Structures to be cut

Well cover

PCV head

RPV insulator

RPV head

Shroud head

Water consumption(L)

Amount of abrasive(Kg)

φ950 mm

Core boring

900

30,000―

3rd layer penetrating

φ750mm

WJ/AWJ420

10,000500

Surface treatment

―

WJ

120

600

―

Small-hole penetrating

φ40 mm

Drill

15

―

―

Large-hole penetrating

φ550 mm

AWJ

160

700

130

Cutting the fixing
bracket

―

AWJ

60

300

50

Removeφ570 mm

Grabbing andtransferring

60

―

―

Spare nozzle cleaning

―

WJ

180

700

―

Small-hole penetrating

φ40 mm

Drill

30

―

―

AWJ

90

400

80

AWJ

40

200

40

AWJ

240

1,000

190

Hole opening in flange
φ385 mmBase structure removal

Steam separator

Process time (min)1st and 2nd layer
penetrating

Nozzle removal

Steam dryer

Construction method

No.55

Bottom plate, small
hole

φ40 mm

AWJ

5

19

3

Bottom plate, largehole

φ184 mm

AWJ

30

111

15

Connection bars

φ190 mm

AWJ

120

444

60

Main bodyφ162 mm (78 tubes)

AWJ

42,120156,000

21,060Cutting scrap collection
hole

φ12 mm

AWJ

10

37

5

Investigationequipment guiding holeφ120 mm

AWJ

40

148

20

44,640200,659

22,153

Approx. 201 t

Approx. 22 t

Total

Approx. 745 h
Approx. 31 days

©International Research Institute for Nuclear Decommissioning6.4.1.6 Top-opening investigation method: Specifications of equipment – Equipment and device list (1/2) No.56
No.

1*

Equipment/device name

Entire work cell

Outlines
A temporary facility to prevent contaminated materials fromspreading to the surrounding environment, to protect workers
from radiation exposure, and to provide devices with a safe
environment by maintaining negative pressure if by any chance
the PCV boundary fails to function

2

Tool box transfer carrier

Equipment to transfer the tool box to the position of holes via
remote control

3

Connection mechanism

Mechanism to connect the tool box with the boundary guidepipe via remote control

4Gate valve on the boundary guide pipeside

A valve to isolate the boundary guide pipe that is connected to
the PCV

5*

Boundary guide pipe

Equipment for maintaining the boundaries after a hole isopened in PCV head6

Boundary guide pipe installationequipment

Equipment to install the boundary guide pipe

7

Movable shielding

Movable shielding used to shield a hole for which the tool box is
not installed

8

Crane-equipped carrier

Crane-equipped carrier used for the maintenance of the gate
valve on the boundary guide pipe side

9

10

Water injection equipment for the innerwall of the boundary guide pipe

Equipment to inject water to the inner wall of the boundary
guide pipe

Tool box 1

Container to house the investigation equipment, accessdevices, and the reactor core internal structure processing
apparatus

No.

Equipment/device name

Outlines

17

PCV head surface measuring equipment

3D laser scanner to measure the shape of a specific part of
the PCV head surface where the guide pipe is installed andits periphery

18

PCV head small-hole penetrating machine

A penetrating machine to open small holes in the PCV
head to eliminate the risk of adverse effect of theaccumulated hydrogen in the PCV head prior to large-hole
opening work

19*

PCV head hole opening machine

Machine to open holes in the PCV head20

Processing apparatus for fixing bracket on
RPV insulator

Machine to cut RPV insulator fixing fittings

21

RPV insulator removal equipment

Equipment to remove a part of the insulator which does notaffect the removal of RPV spare nozzle

22

RPV spare nozzle cleaning equipment

Equipment to remove the pieces of the insulator and othermetal pieces left in the area where the RPV spare nozzle
removing work is carried out

23

RPV spare nozzle surface measuring
equipment

3D laser scanner to measure the shape of the area aroundthe RPV spare nozzle

24

Small-hole penetrating machine for RPV
spare nozzle flange

A penetrating machine to open small holes in the RPV
spare nozzle flange to eliminate the risk of adverse effectof the accumulated hydrogen in the RPV spare nozzle prior
to large-hole opening work

25

Hole opening machine for the RPV sparenozzle flange

A machine to open a hole in the RPV spare nozzle blind
flange26

AWJ machine to cut the RPV spare nozzle
from the inside

An AWJ machine to cut the RPV spare nozzle from theinside and remove its upper part by inserting its head into
the nozzle

11

Tool box 2

Container to house the processing apparatus used until
reaching the RPV head, etc.

12Tool box 3

Container to house the processing apparatus used until
reaching the RPV head

27

AWJ machine to cut the RPV spare nozzle
from the outside

An AWJ machine to cut the joint between the RPV sparenozzle and the RPV head from the outside and remove its
lower upper part

13

Well cover core boring machine

A machine to bore holes in the 1st and 2nd layers of the well
cover

28*

The reactor core internal structure
processing apparatus

Machine to open a hole in the steam dryer, steam
separator, and shroud head

14

Well cover AWJ chipping machine

A machine to bore small holes in the well cover, remove its 3rdlayer, and serve as a backup in case of the deformation of the
1st and 2nd layers

29

Fixture for the the reactor core internal
structure processing apparatus

Equipment to fix the pipe sling for the the reactor coreinternal structure processing apparatus

15

PCV head surface treatment system(WJ)

Equipment to process a specific part of the surface of the PCV
head where the guide pipe is installed and its periphery,specifically removing the coating and foreign materials there, toprevent adverse effects of the surface condition on the sealingof the gap between the PCV head and the guide pipe

16

PCV head surface treatment system(brush)Equipment to remove coating and foreign materials that remainon the surface of the PCV head after treatment by the PCV
head surface treatment system (WJ)

©International Research Institute for Nuclear Decommissioning6.4.1.6 Top-opening investigation method: Specifications of equipment – Equipment and device list (2/2) No.57
No.

30

31

Equipment/device name

Investigation equipment ALS

Investigation equipment AHS

Outlines
An investigation machine sent to the reactor through small
holes (φ40mm) opened in the the reactor core internal
structures to perform preliminary surveys, such as
investigation of the condition of the structures andenvironment (air dose rate and temperature) andexamination of the feasibility of planned works to proceedwith investigation activities

An investigation machine sent to the reactor through small
holes (φ40mm) opened in the the reactor core internal
structures to perform preliminary surveys, such as
investigation of the condition of the structures andenvironment (air dose rate and temperature) andexamination of the feasibility of planned works to proceedwith investigation activities

32

Investigation equipment ALS and AHS
guiding system

A mechanical system to guide investigation equipment ALS
and AHS from the tool box down to the shroud head

33

Investigation equipment ALB

An investigation equipment for the reactor core section
deployed only in case an access route through the insideof the steam separator is established

34

Investigation equipment AHB

An investigation equipment for the reactor core section
deployed only in case an access route through the insideof the steam separator is established

35

Investigation equipment ALB and AHB
guiding system

A mechanical system to guide investigation equipment ALB
and AHB into the steam separator

Investigation equipment B1

A device that is sent to the reactor through large-diameterholes (≥ φ110 mm) opened in the the reactor core internal
structures and used to investigate the condition of thestructures and fuel debris as well as the environmental
conditions (air dose rate and temperature) in the reactor indetailInvestigation equipment B2

A device that is sent to the reactor through large-diameterholes (≥ φ110 mm) opened in the the reactor core internal
structures and used to investigate the condition of thestructures and fuel debris as well as the environmental
conditions (air dose rate and temperature) in the reactor indetail38

Investigation equipment B3

A device that is sent to the reactor through large-diameterholes (≥ φ110 mm) opened in the the reactor core internal
structures and used to investigate the condition of thestructures and fuel debris as well as the environmental
conditions (air dose rate and temperature) in the reactor indetail39

A device that is sent to the reactor through large-diameterholes (≥ φ110 mm) opened in the the reactor core internal
structures and used to investigate the condition of theInvestigation equipment B4
structures and fuel debris as well as the environmental
conditions (air dose rate and temperature) in the reactor in
L: Low radiation,detail
H: High radiation, S: Straight, B: Bend

36

37*

No.
40

41

42

Equipment/device name

Outlines

Investigation equipment B guiding system

A mechanical system to guide investigation equipment B1,
B2, B3, and B4 from the tool box down to the shroud head

Investigation equipment C

An investigation equipment for the reactor core section
where a high environmental dose rate is estimated. It canbe moved around in a wide area of the reactor core section
by the XY position control above the upper grid plate using
the guiding system (horizontal extension arm) in
combination with its position control functions.

Investigation equipment C accessing system

A guiding system to guide investigation equipment C to thereactor core section. It suspends the investigationequipment, brings it down to the area above the upper gridplate, and moves laterally by unfolding the horizontal
extension arm in a space between the shroud head andthe upper grid plate. The final XY position of the device iscontrolled by the extension of the horizontal extension arm,and the device is moved down to the reactor bottom.

*) Some of the main equipment and devices in this table are further explained indetail in the next and subsequent pages.

©International Research Institute for Nuclear Decommissioning6.4.1.6 Top-opening investigation method: Specifications of the equipment and devices No.58
No. 1: Entire work cell
<Outlines>
A facility to prevent radioactive materials that leaked from the joints with the tool box and boundary
guide pipe on the operation floor, if any, from spreading to the surrounding environment
The floor of the work cell at and around the connection with the hole is elevated to the height of the
newly installed shielding floor with a work pit in the space created by the elevation, considering repair
work by workers which may be required in case of the failure or malfunction of the equipment associatedwith the connection with the boundary guide pipe or the gate valve on the guide pipe side.
Guide rails are laid on the floor of the entire work cell between the airlock cells and work cell so that atransfer carrier can travel on them to carry the tool box to the area above the boundary guide pipe.
Airtight shutters are installed between the work cell and airlock cells to prevent direct airflow between
the outside of the work cell and the work cell when equipment and devices are carried in or out and also
to maintain a negative pressure. Two airlock cells are attached to both sides of the work cell to enable
the inbound transfer of one device and the outbound transfer of another at the same time to support
device change.
Utility interface wall boards are installed on the side wall of the work cell to help supply utilities to thedevices in the tool box.
A hatch is installed on the ceiling board of the entire work cell to enable the transfer of devices aroundthe boundary guide pipe. Similarly, a hatch is installed on the ceiling board of each airlock cell to enable
the transfer of the tool box, etc.
<External appearance>

Equipment transfer
hatch of the airlock cell
(Hatch in the airlock
cell ceiling)

Workeraccessdoor

Airtight shutter

Equipment transfer hatchof the work cell
(Hatch in the work cell
ceiling)

Door between the worker
access control room andentire work cell
Worker access door

Workeraccess door

<Main functions and features>[Negative-pressure control function]· The negative pressure in the entire work cell is maintained below the atmospheric pressure using an
exhaust fan (blower) and gravity dampers to confine contaminated materials that leaked through thejoints with the tool box and boundary guide pipe in it, if any. In addition, the entire work cell is divided into
the following three compartments to maintain its negative pressure even when workers go in or out fromthe cell or when the equipment is carried in or out from it: a compartment positioned right above a hole(hereinafter referred to as “work cell”) and two compartments attached to both sides of the work cell forcarrying in and out the tool box (hereinafter referred to as “airlock cell”).
[Utility supply function]· Detachable utility interface wall boards with sealing ability, each of which is designed unique to different
equipment and devices, are provided to the interface utility supply lines between the sources outside andequipment and devices in the entire work cell through its wall.

<Basic specifications>[Structure]· Constructed by wall boards to exhibit an airtight capability.
[External dimensions]· Entire work cell: approximately 7.85 m(W) × 28 m(D) × 7.8 m(H)[Total volume]· 1,365 m3<Cells>Airlock cell A: 290 m3
Airlock cell B: 290 m3
Work cell: 785 m3[Approximate weight]· About 196 t[Exhaust fan capacity]· 4,095 m3/h

Equipment transfer hatchof the airlock cell
(Hatch in the airlock cell
ceiling)

Airtight shutter

Workeraccesscontrol room

Workeraccesscontrol room

Tool box

Transfer
carrier

Boundary guidepipeMovableshielding

Door between the worker
access control room andentire work cell
Worker access door

Work pitSideshielding©International Research Institute for Nuclear Decommissioning6.4.1.6 Top-opening investigation method: Specifications of the equipment and devices No.59
No. 5: Boundary guide pipe
<Main functions and features><Outlines>
Equipment for maintaining the boundaries between the work cell and thePCV head after a hole is opened in the PCV head
<External appearance>
Guide pipe ancillaryequipmentInterface flange for guidepipe ancillary equipment

Base plateapprox. 5,400 mm

Positioning plate

WeightPipe (650A Sch10)
Outer diameter φ660.4 mm
Inner diameter φ644.6 mm

Guide pipe mainbody

Sealingmechanism

Cross-section view ofthe sealing mechanism

Seal material(EPDM rubber)[Configuration]· This equipment consists of the guide pipe (main component), sealing mechanism attached to theguide pipe, base plate used to fix the guide pipe to the work cell, and ancillary unit equipped withutility ports and pressure indicator, etc.
· A weight is attached to the outer surface of the upper part of the guide pipe to exert sufficient gravity
force to achieve a stable rubber sealing function.
[Double-sealing function]· A rubber sealing (such as EPDM rubber) is provided at the bottom end of this equipment, whichcomes in direct contact with the PCV head, to secure the airtightness of the connection. The sealing
is pushed against the PCV head by the gravity force of the weight.
· The sealing mechanism has the following sealing performance:
Positive pressure: 10 kPa
Negative pressure: inside PCV (guide pipe) < Entire work : −100 Pa,
Inside PCV (guide pipe< inside Reactor well (section with atmospheric pressure):
negative pressure 160 Pa[Position adjustment function]· Tapped holes are supposed to be prepared on the floor of the work cell in advance so that the baseplate is fixed using them.
· Position guiding blocks attached to the base plate help the guide pipe to be placed at the rightposition.
[Measuring function]· Pressure indicators, nitrogen flow meters, hydrogen and oxygen gas detectors, and exhaust gas line
connection ports are installed on ancillary equipment of the guide pipe to measure various
parameters.
[Cleaning function]· A spray tube is attached to the base plate to wash the surface of the guide pipe.

<Basic specifications>[Main body]· Approximate dimensions: 870 mm × L
5,400 mm
· Pipe size: 650A Sch10 (outer diameter:
φ660.4 mm, inner diameter: φ644.6 mm)· Approximate weight: 2,000 kg[Base plate]· Approximate dimensions: φ1,500 mm ×
H280 mm· Approximate weight: 400 kg[Ancillary equipment]· Approximate dimensions: φ825 mm × t 50 mm· Approximate weight: 65 kg[Installation position accuracy] (rough guideline)· Inclination: 1°, XY position: ±10 mm©International Research Institute for Nuclear Decommissioning6.4.1.6 Top-opening investigation method: Specifications of the equipment and devices No.60
No. 19 PCV head hole opening machine<Outlines>
A machine to open a hole in the PCV head at thepredetermined position (right above the spare nozzle) after asmall hole is bored in the PCV head
<External appearance>

Guide roller

Tool turning motor

Stabilizer
Abrasive
protection sheet
Camera with lighting
Nozzle up–down
mechanism
AWJ nozzle
MagnetPCV head hole opening
machineMagnet(For the collection of
cutting scraps)

WJ nozzle
Cut pieces<Main functions and features>[Configuration]· This machine consists of the tool frame and AWJ penetrating tool attached to it. The tool frame is equipped withguide rollers to guide it smoothly and stabilizers to stabilize it in the guide pipe by making contact with the innerwall of the pipe.
[Lifting function]· The tool frame can be moved up and down in the guide pipe (between the tool box and the top of the PCV head)using a hoist in the tool box installed above the guide pipe.
· Once it reaches the top surface of the PCV head, it is fixed to the inner wall of the guide pipe by the air-driven
stabilizers (pneumatic cylinder).
[Penetrating function]· The machine has a function to open a round hole with a diameter of about φ550 mm and its center exactly
matching the center of the tool (center of the guide pipe) in the PCV head by swiveling the AWJ tool using anelectric tool swivel mechanism.
[Abrasive protection function]· The tool frame is equipped with the abrasive protection sheet so that the flying abrasive can be blocked during
AWJ injection.
[Function to hold and collect cutting scraps]· A cutting scrap collection magnet (permanent magnet) is installed at the center of the AWJ penetrating tool sothat it can hold and collect the cutting scraps generated during the PCV head penetrating by AWJ. This
permanent magnet can be switched on and off using compressed air.
[Monitoring function]· A small camera is installed on this machine along with lighting so that it can monitor the condition of the transfer,installation, and operation of this machine.
<Basic specifications>[Entire machine]· Main dimensions (approximate values): φ600 mm ×H1,000 mm· Weight: approx. 100 kg· Material (main structure): SUS304[Hoisting mechanism]· An electric hoist is installed on the tool box to movethis machine up and down. Two sets of the hoists
are installed to suspend the machine with two slings
to prevent the machine from falling.
[Tool turning mechanism]· Swivel motion of the bottom part of the tool by anelectric motor· Swivel range: more than 0° to 360°

[Tool fixing stabilizer]· Fixing the tool by three pneumatic cylinders· Pressing force: approx. 150 kgf[AWJ penetrating tool]· AWJ mechanism: injection pressure, approx. 345–380
Mpa; abrasive feed rate, approx. 0.78 kg/min· AWJ nozzle up–down mechanism: a mechanism tokeep the distance between the surface of the PCV
head and the nozzle constant in response to theundulation of the PCV head surface and perform AWJ
penetrating using the nozzle position controller with avertical extension and contraction mechanism. Thismechanism moves the nozzle up and down using thelink mechanism and spring reaction force without
using any actuator.
· Cutting scrap holding and collection mechanism: apermanent magnet with a pneumatic cylinder position
controller and a holding power of ≥approx. 120 kg(weight of a single cutting scrap: approx. 60 kg)©International Research Institute for Nuclear Decommissioning6.4.1.6 Top-opening investigation method: Specifications of equipment and devices
No. 28: The reactor core internal structure processing apparatus<Outlines>
A machine that is installed on the work cell at a planned position along the vertical line that
goes through the RPV spare nozzle and opens holes in the steam dryer, steam separator,and shroud head
<External appearance>

Abrasive tankDrum

Connection guide pipe
Lifting
apparatus

Approx.
3,600 mmTool transfer
mechanismApprox. 3,700 mm

AWJ nozzle

Injection reaction force receiving
jig ② (Supporting reaction force
by making contact with the holein the steam separator after the
injection reaction force receiving
jig ① passes through the gap
between the three cylinders of
the steam separator). It isretracted in the pipe sling unless
AWJ is operated.)

Injection reaction
force receiving jig①(Inserted in the gap
between the threecylinders of thesteam separator)

No.61<Main functions and features>[Configuration]· This machine consists of the tool head with the AWJ nozzle, pipe sling, hoistingmechanism, drum, abrasive tank, and tool transfer mechanism.
· High-pressure water for AWJ is supplied from a super-high-pressure pump installed on theoutside of the entire work cell.
[Tool head]· The tool head consists of the AWJ nozzle, injection reaction force receiving jig, linkmechanism to control the position and angle of the AWJ nozzle, and θ-axis motor toswivel the tool head.
[Pipe sling]· Each pipe forming the pipe sling is 700-m long, and the tool head is attached to the distal
end of the pipe sling. The other end is connected to the drum.
· The drum turns to wind and unwind the pipe sling, which in turn causes the tool head tomove up and down.
· Each link of the pipe sling is fixed as it passes through the hoist assist mechanism, so thatthe axis of each pipe is aligned straight, and the tool head is stably held by it.
[Hoisting mechanism]· This mechanism is composed of the hoist rollers and toggle lock and assists the verticalmovement of the pipe sling.
[Drum]· This equipment winds and unwinds the pipe sling.
[Abrasive tank]· This equipment consists of a tank and a weight scale.
[Tool transfer mechanism]· This mechanism controls the horizontal position of the the reactor core internal structure
processing apparatus.
<Basic specifications>[Entire machine]· Main dimensions (approximate values): 5,300 mm * × 3,700 mm × H3,600 mm* This can be downsized according to the required stroke for the tool transfer
mechanism· Approximate weight: 10,000 kg[Penetrating machine]· AWJ nozzle[Control methods for the mechanisms]· Electric and hydraulic remote control

Tool head (for the steam separator cutting)©International Research Institute for Nuclear Decommissioning6.4.1.6 Top-opening investigation method: Specifications of the equipment and devices No.62
No. 37: Investigation equipment B2<Outlines>
A device that is inserted into the reactor through large-diameter holes (≥φ 110 mm)
opened in the reactor core internal structures and used to investigate in detail thecondition of the structures and fuel debris as well as the environmental conditions (airdose rate and temperature) in the reactor It is used in high-radiation areas as its camera
has a high radiation resistance. It can create a panoramic image by scanning a target
using its pan and tilt mechanism. It is used mainly in the investigation in the following
areas:· Inside the well cover· Inside the PCV head
· Inside the RPV head
· Inside the reactor core
<External appearance>

Tilting range
0°(vertical)
to 110°

Position during the up
and down movements

Light arms fully stretched

Stretchable
arm lights

Panning
range
±180°

Tilted at 90°<Main functions and features>[Configuration]· Color CID camera, pan/tilt mechanism, LED lights (with stretchable mounting arms), dosimeter,
and thermometer· Cables are bundled in a sheath tube (flexible SUS tube) for protection.
[Function]· Slip clutches installed on the head tilting and light arm stretching mechanisms make it possible forthe head and light mounting arms to return to their retracted position as the head goes throughholes, so that the head can be withdrawn by forceful pull-up in case of failure.
· A celestial-sphere image (panoramic image) can be created.
[Advantages]· A color image can be captured.
· It has a wide eyesight in the vertical direction.
· A lookdown-view celestial-sphere image (lookdown overview image) can be captured.
[Disadvantages]· The head loses its horizontal position when tilted due to the change in the center of the gravity.
(Position compensation is required)<Basic specifications>[Outer dimensions]· Main dimensions : Outer diameter, Φ95 mm; length, 835 mm· Weight: approx. 6 kg
[Image capturing performances]· Type of camera : CID (color); diagonal angle of view, 35°; number of pixels, approx. 300,000· Lighting: LED (3W × 6 when the arm is fully stretched); distance between the optic axesof the camera and the light, 117.5 mm· Visibility range: 2,000 mm (defined as the maximum distance at which a φ10-mm fuel rod canbe recognized in a fog with an absorption coefficient of 0.223)[View direction control]· Pan and tilt method: pan motion range, ±180°; tilt motion range, 0° (vertical) to 110°
[Mounted sensors]· Dosimeter: 1 to 5,000 Gy/h, sufficient accuracy for determining the digit number of thedose rate· Thermometer: Range 0° to 50°C; accuracy ±1.5°[Radiation resistance]· Cumulative dose rate
: 30 kGy· Maximum permissible exposure time: 10 h (exposure limit for the LED light in 3,000 Sv/henvironment)[Waterproof and dust proof]· Equivalent to IPX4©International Research Institute for Nuclear Decommissioning

North

6.4.1.6 Top-opening investigation method: Equipment and device layout design(operation floor layout)

Total weight: approx. 600 t(When all the equipment and devices are
installed on the operation floor)

48 mOpening hole forinvestigation
Well cover outer diameter

No.63

Area for the entire work cell (weight: approx. 321 t)
Weight breakdown• Entire work cell: 196 t• Area for the ancillary equipment of the work cell : 50 t
×2
• Others: 25 t

Well cover outer
diameterBored hole forinvestigation North。

Upper section of the operation floor of Fukushima
Daiichi Power Station No. 3 Unit (Bird’s-eye view)

37 m

Area for equipment and device area (weight: approx.
213 t)
Weight breakdown• Boundary protection equipment and devices: 10 t
• Machines used to cut the structures until reaching the
RPV head: 113 t• The reactor core internal structure processing apparatus:
24 t• Investigation systems: 66 t
⇒ Can be placed in places other than the operation floor.

Area for control boards (weight: approx. 52 t)
Weight breakdown• Boundary protection equipment control systems: 21 t
• Control systems for machines used to cut structures until
reaching the RPV head: 20 t
• Control systems for the reactor core internal structure
processing apparatus: 8 t• Investigation system controllers: 3 t⇒ Can be placed in places other than the operation floor.

Upper section of the operation floor of Fukushima Daiichi Nuclear Power Station Unit 3 (top view)©International Research Institute for Nuclear Decommissioning6.4.1.6 Overview of system configuration for Top-opening investigation method<Remote control room area>• Control PC

No.64<Entire work cell area>• Boundary protection equipment
✓
✓
✓
✓
✓
✓
✓
✓
✓

Boundary guide pipe
Boundary guide pipe installation equipment
Gate valve on the boundary guide pipe side
Tool box (1, 2, 3)Gate valve on the tool box side
Tool box transfer carrier (including the link mechanisms)
Movable shielding
Crane-equipped carrier
Water injection equipment for the inner wall of theboundary guide pipe
✓ Exhaust blower for the entire work cell
✓ Exhaust blower for the tool boxes• Machines used to cut the structures until reaching
the RPV head<Control panel area>• Boundary protection equipment
control systems• Control systems for machines used
to cut the structures until reaching
the RPV head
• Control systems for the reactor coreinternal structure processing
apparatus• Investigation system controllers

✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓

Well cover core boring machine
Well cover AWJ chipping machine
PCV head surface treatment system (WJ, brush)
PCV head surface measuring equipment
PCV head small-hole penetrating machine
PCV head hole opening machine
Processing apparatus for fixing bracket
RPV insulator removal equipment
RPV spare nozzle cleaning equipment
RPV spare nozzle surface measuring equipment
Small-hole penetrating machine for the RPV head
Hole opening machine for the RPV spare nozzle flange
AWJ machine to cut the RPV spare nozzle from theinside✓ AWJ machine to cut the RPV spare nozzle from theoutside✓ PCV head plugs• The reactor core internal structure processing
apparatus✓ The reactor core internal structure processing apparatus(for Units 1 and 2)• Investigation systems✓✓✓✓

Investigation equipment (ALS, AHS, ALB, and AHB)
Investigation equipment (B1, B2, B3, and B4)
Investigation equipment C
Investigation equipment guiding systems (A, B, C)©International Research Institute for Nuclear Decommissioning6.4.2 Development of investigation equipment for side access method No.65
With regard to machines used for penetrating from the outside of R/B to the shroud head, equipment to prevent dust spread, and devices
that guide investigation equipment to the investigation target points, technologies that can solve issues for the realization of on-site
investigation are developed, and necessary devices and systems are designed in detail and rationalized. In addition, element tests arenecessary for device development; thus, they should be conducted if necessary in FY2018 to verify the applicability of the devices toinvestigational works at the site based on the correct understanding of the actual site conditions.

Item
1

Entire work cell development

Outlines

Progress

Develop a system to maintain anegative pressure, in preparation forthe possibility of radioactive dust leakfrom the tool box.

Develop a system and equipment thatcan prevent radioactive materials fromspreading to the surrounding
the shroud head
Development of equipment to environment during cutting. Morespecifically, develop a method andprevent radioactive materials
equipment to establish a boundary by
from spreading
inserting the guide tube into thetelescopic guide pipe whenever the
penetrating and cutting of the biologicalshielding wall, PCV, and RPV are
implemented. Especially, conduct
See the pages below
Development of investigation
element tests for systems to handle
equipment guiding systems
processed materials and wastewater
generated by the use of abrasive water
jet, which is a key technology for thismethod, at an early stage and reflect
the results in the design work.
The tool boxes house the hole opening
machines and equipment to prevent
radioactive materials from spreading.
They will be preconditioned andDevelopment of a maintenance decontaminated before and after use inunit
a maintenance unit built in a groundlevel area according to the plan.
Develop a maintenance unit capable ofpreventing radioactive materials fromspreading.

FY2018
Necessity of theelement tests
considered

FY2019Element test planning

Development of processing

2 apparatus used until reaching3

4

Element test

Verification of the applicability
to works at the site

Detailed design, rationalization, and equipment
specification determination in consideration of
on-site working©International Research Institute for Nuclear Decommissioning6.4.2 Development of investigation equipment for side access method No.66
Item

Entire work cell

Implementation plan

Implementation items and results· Rationalization of the structure and construction method, taking into
consideration the work steps, as well as weight reduction, including support
structure· The device and equipment layout plans in and around the entire work cell wererationalized.
· Clarification of the location of potential interfering objects on access route
candidates and space availability· Detailed design of the negative-pressure control system· Layout plans were established for the inside and outside of thework cell in consideration of the worker’s traffic line in the entire
work cell.
· The methods to reduce the weight of the entire work cell andsupport structures and also distribute their weight evenly weredevised in consideration of the maximum bearing capacity of theconcrete slab roof of the air-conditioning equipment room. The
feasibility of the devised methods was verified.
· An airflow rate balance required to maintain the negative pressure
was set, and system configuration and the capacity of components
to realize the airflow rate balance were elucidated.

· Feasibility verification (evaluating the cutting performance and wastewater
Processing apparatus used until collection method) and rationalization of the penetrating tools
reaching the shroud head
· Rationalization of the structure and construction method of the tool boxes· Interface between the investigation equipment and the tool box· The basic structures of the tool box and cutting tool heads were
designed through the cutting performance tests and wastewatercollection tests. In addition, system design was performed alongwith the component selection.

Boundary protection· The sealing performance of the guide tube was evaluated by an· Rationalization of the structures and construction methods in consideration of the element test.
ease of construction· The basic structures of the guide tubes were determined.
· Verification of the sealing performance (confinement performance) of the guide · Mass balance required to maintain a slight positive pressure than
the PCV inner pressure was calculated, and system configuration
pipe· Detailed design of a high-sensitivity pressurization control systemand the capacity of components to realize the mass balance were
elucidated.

Investigation equipment guiding
systems· Develop a mechanism to guide the investigation equipment in the reactor core
· Information on the interface required to operate the investigation
area based on the policy that investigation equipment, including cameras, under equipment (such as shape, weight, electricity, and communication)
development for the top-opening investigation method are used for the sidewas made clear as design conditions, and the guiding mechanism
opening investigation method.
was designed based on it.

Maintenance unit

· Rationalization of the layout plans for the inside of the maintenance unit and its · The functions of the maintenance unit and the configuration of theperipheryequipment in it were studied, and a layout plan was created.
· Development and design of the devices and systems and verification of their on- · The strength of the maintenance unit was evaluated based on thesite operability
layout plan. In addition, the design specifications were determined.

©International Research Institute for Nuclear Decommissioning6.4.2.1 Side-opening investigation method: Entire work cell (1/2) No.67
Item

Implementation plan

· The weight of the entire work cell was estimated to be heavier than theoriginal plan in the study in FY2017. Weight reduction needs to be
Weight reduction of the entire achieved for the entire work cell itself as well as for its support structures.
work cell and support· Estimate the total weight of the main equipment installed on the periphery
structuresof the entire work cell, such as a wastewater collection and discharge
Rationalization of a layout
system and negative-pressure control system, and develop an equipment
plan for peripherylayout plan that fulfills the maximum bearing capacity of the concrete slab
roof of the air-conditioning equipment room based on the estimatedweight.

Implementation items and results· A method for reducing the weight of the work cell and a layout
plan to achieve an adequate weight-load distribution on theroof of the air-conditioning equipment room were devised inconsideration of the maximum bearing capacity of the concreteslab roof of the room. The weight-load distribution to R/Bpillars was calculated, and the method and layout plan wereconfirmed to be feasible.
(The entire work cell was downsized, reinforcing support
structures were strengthened, and some of the equipment
were relocated to a ground-level area)
Hydraulic pump unit and its peripheral equipment(Approx. 1 t)

Airlock system(Approx. 1 t)

Tool box AC0(approx. 9 t)

Air-conditioning
equipment room
Ancillaryequipment

T/B

Airlock module for worker in/out(Approx. 1 t)

R/B
Tool box

Air-conditioning
equipment for negativepressure control(Approx. 1.8 t)

Tool box ACx and support structure(Approx. 30 t)

High-pressure water supply system(approx. 2.5 t)
Waste storage tank
(Approx. 18.5 t)

Entire work cell

Nitrogen gas supply
system(Approx. 2.3 t)

Turbo blower for cutting scrap
collection and filter unit
(Approx. 14 t)

Some of the peripheral
equipment are installed
on a ground-level area.
©International Research Institute for Nuclear Decommissioning6.4.2.1 Side-opening investigation method: Entire work cell (2/2) No.68
Item

Implementation plan

Clarification of the location ofpotential interfering objects onaccess route candidates andspace availability

Implementation items and results· Study the best access route for investigation that can minimize cutting and penetrating works, such as· An access route plan that could avoid cutting of
cutting piping in the reactor, and determine the tool installation position (penetrating angle forpiping and other interfering objects in the reactor
investigation hole penetrating).
was formulated. (Reported)· Determine the available space for the installation of the entire work cell and seismic design conditions.

Detailed design of the negative- Study functional requirements for the negative-pressure control system of the entire work cell from thepressure control system
point of view of safety and reflect the result in the system specifications.

· Target pressure values (negative pressure of up to−300 Pa) were determined for each of theboundary protection equipment, a system diagram
was created, and airflow rate balance between
adjacent compartments was designed. (Reported)· The system specifications were fixed.

Maintain the inner pressure of ACx and AC0 at 1.25 times higher than the PCV inner pressure by feeding nitrogen gas to ACx and AC0 before opening the isolation
valve of AC0. Prevent the spread of radioactive dust in the PCV to the surrounding atmosphere by maintaining the inner pressure of each boundary protection
equipment as defined by the inequality below after opening the isolation valve. (A design value that was set by adding margin to the maximum operation data of theplant should be used as the PCV inner pressure)

PPCV ≤ PACx > > POB < Pair

Entire work cell
POB = -80 to -100Pa

Tool box
PAC0/Acx = 7.5kPa(PAC0/ACx = -220+ to -300Pa)*

Pressure inside
the PCVPPCV =7.5 kPa

Atmosphericpressure
Pair = ±0 Pa*) The equation in the parentheses expresses the state before the isolation valve is opened.

System diagram of the equipment installed on theroof of the air-conditioning equipment room
(ACx is docked with AC0)
©International Research Institute for Nuclear Decommissioning6.4.2.2 Side-opening investigation method: Processing apparatus used until
reaching the shroud head (1/2)
Item

Implementation plan

No.69

Implementation items and results

Feasibility verification(evaluating the cutting· Conduct element tests to verify the feasibility of
performance and wastewaterelement technologies and collect basic data forcollection method) andequipment design.
rationalization of the penetrating
tools· Element tests to evaluate the cutting performance and wastewater collection
ability were conducted using test samples made for these purposes.
(Reported)· The results of the tests were reflected in the design of the machines, and theamount of abrasive and water required for the cutting works was estimated.

Biologicalshielding wall

PCV
Biological shielding

Shroud head
Concrete formwork
Heat-retention
material

RPV

AWJ
nozzleStructures to be cut on the access route

WJ nozzle

Equipment for wastewater collection test
Tool head used in the cutting
performance
evaluation
Total water testTotal abrasive consumption
Structures to be cut
consumption (L)(kg)

Process time (hours andminutes)

Biological shielding
wall
+PCV

83,9864,520(4290 + 230)*1

176:04

RPV shield wall +insulator + RPV

15,671705

31:25

Shroud head

1,270

163*2

4:30

Remarks*1) A large part of the abrasive used for the AWJ cutting process was consumed for cutting rebars in the
biological shielding wall into small pieces (see the photo below on the left). The amount of abrasive
needed for penetrating the PCV itself was 230 kg. Based on this data, about 4,300 kg of consumed
abrasive was estimated to be collected together with the wastewater.

*2) To ensure sub-criticality, it is important to limit the weight of a single piece of scraps 16 kg that may fall in
the reactor core area during the cutting work.

©International Research Institute for Nuclear Decommissioning6.4.2.2 Side-opening investigation method: Processing apparatus useduntil reaching the shroud head (2/2)
Item

Implementation plan

No.70

Implementation items and results•· Design the basic structure withconsideration of the weight of the tool boxes
Rationalization of theand the gravity center during handling.
•
structure and construction· Design the structure of the tool boxes inmethod of the tool boxes
detail based on the specifications of thetools equipped in it.

The basic structures of the tool boxes and tool heads were designed.
AC0: The tool box that is permanently installed on R/B and functions as the base forconnecting other tool boxes (ACx)
AC2: The tool box used to insert the guide tube
AC3: The tool box to house the processing apparatus
AC5: The tool box used to insert the investigation equipment
A mechanism capable of stably moving the tool forward and backward in the guidetube without shaking was designed. (A guide tube laid inside another guide tube isguided in the latter by the crawler that has rollers and rotation preventing mechanisms
on it. The rollers and rotation preventing mechanisms of the crawler comes into
contact with the inner surface of the latter to maintain an exact concentric relationshipbetween the two while they are moved forward and backward as presented in the
figures below)

Basic structure of the tool boxes (AC2, AC3, and AC5)

Crawler

AC0 side viewAC0 bird’s-eye viewRotation preventing
mechanism
Guide
tube
Crawler

Guide tube

RollerIllustration of the guide tube with the crawler inserted in it from the tool box

Guide tube inside cross-sectional view
©International Research Institute for Nuclear Decommissioning6.4.2.3 Side-opening investigation method: Boundary protection No.71
Item

Implementation plan

Implementation items and results

Verification of the sealing
performance (confinement
performance) of the guide
tube· Conduct element tests to verify the feasibility of element technologies
and collect basic data for equipment design, such as a leak rate.

· Element tests were conducted, and the sealing performance ofthe guide tube was found to satisfy the criterion (≤ 0.05 vol%/h)
set in reference to the leak rate criteria of ISO10648 applicable toglove boxes, etc. (Reported)

Rationalization of thestructures and construction
methods in consideration of
the ease of construction· Conduct element tests to verify the feasibility of element technologies
and collect basic data for equipment design.

· Element tests (joint strength tests) were conducted, and the jointof the guide tube was found to be strong enough to withstand anaxial load determined to be necessary to achieve the target
sealing performance through the abovementioned tests.

Main body of the guide tube

Mechanical seal

EPDM seal
Illustration of the mechanismof the rotation preventing
mechanisms

Rotation preventing
mechanism

Air exhaust

EPDM seal
Metal shims
Pipe flange
Rotation preventing
mechanisms

Guide roller

Drawing of a guide tube structure
Each of the guide tubes is equipped with guide rollers and rotation preventing
mechanisms, so that they can be aligned in an exact concentric manner.

Quick-release coupling

Drawing of a PCV guide tube sleeve structure
Cement milk filling ports are provided at four positions in the top edge of thesleeve to evenly fill the entire gap between the sleeve and a hole with cement.

©International Research Institute for Nuclear Decommissioning6.4.2.4 Side-opening investigation method: Investigation equipment
guiding systems
Item

Investigation equipment
guiding systems

No.72

Implementation plan

Implementation items and results· Design interface between the investigation equipment and tool
boxes based on the policy that investigation equipment, including
cameras, under development for the top-opening investigation
method are used for the side-opening investigation method.
· Design a mechanism to guide and send investigation equipment to
the reactor core.

· Information on the interface required to operate theinvestigation equipment (such as shape, weight, electricity,and communication) was made clear as design conditions,and the interface systems and mechanisms necessary tohouse the investigation equipment in the tool boxes in goodconditions and make them work accurately and effectively
were designed. (Reported)

Site
Control room
(Control center)

Power panel room (electrical room)

Legend
LV trans panel(Low-voltage switch box)

PowersourceControl
SignalLAN
Control panel (PC)Air
Others

Negative-pressure area
distribution panel(Outer building cabinet)

Main control room
(Control room) –Seismic Isolated
Building

ACx distribution panel(ACx cabinet)

AC0 cabinet

Control panel (PC)Main control
panel(Main control
cabinet)Air supply

Entire work cell
(Outer building)

Relay panel

AC0 group power supply panel(AC0 grouping electrical box)

ACx group power supply panel(ACx grouping electrical box)

AC0 group signal panel(AC0 grouping control box)

ACx group signal panel(ACx grouping control box)

Power panel

Roof hatch
Hoist

Air supply

Tool box (ACx)Tool box (AC0)Pipe sling drive
mechanism

Converters, etc.

Relay panel

Relay panel

Isolation valve

Isolation valve

Water treatment system

Machines and devices

MotorsInvestigationequipment

Measuringequipment

Relay
panel

Power line andcommunication block
diagram for investigationequipment (example)

Trolley

Blowers
Motors©International Research Institute for Nuclear Decommissioning6.4.2.5 Side-opening investigation method: Maintenance unit
Item

Implementation plan

No.73

Implementation items and results· The functions of the maintenance unit and the configuration of the equipment in it werestudied, and a layout plan was created. (Reported)· Rationalization of the layout plans for the inside of· A system diagram for the equipment used to control the negative pressure inside thethe maintenance unit and its periphery
Maintenance unit
room was created (presented in the next page), and airflow rate balance was· Development and design of the devices anddetermined according to the level of negative pressure.
systems and verification of their on-site operability· The specifications of the equipment were fixed, and their strength was evaluated basedon the specifications.
Equipment, material,
and waste in/out
control room

Maintenance
unit

Materialstorage

Maintenanceroom

Transfer tool boxes
ACx by trailer

Control area

Temporary building*Staff access
control room

Connection
room

Tool box
connecting area
Staff access
control room

Bird’s-eye view*) A temporary building like a tent warehouse is used for buildings constructed outside tosave cost and construction time.

Layout diagram of thetemporary building inside(plan view drawing)©International Research Institute for Nuclear Decommissioning

No.746.4.2.6 Side-opening investigation method: Operating parameters
for the water volume to be used in abrasive and cutting works (rough estimate)
Required holespecifications

Structures to be cut

Construction
methodProcess time
(Hours andminutes)Water
consumption(L)

Abrasive
consumption(kg)

WJ/AWJ

176:04

83,9864,520(4290 + 230)*1

WJ/AWJ

31:25

15,671

705

AWJ

4:30

1,270

163*2

211:59100,972

5,388

Approx.
8.9 days

Approx.
100,000 L

Approx.
5.3 t

φ480 mm

Biological shielding wall
PCV

φ400 mm

RPV shield wall

φ400 mmHeat-retention material

φ300 mm

RPV

φ220 mmShroud headφ220 mm
Total*1) A large part of the abrasive used for the AWJ cutting process was consumed for cutting rebars in the biological shielding wall into small pieces (see the photo below on theleft). The amount of abrasive needed for penetrating the PCV itself was 230 kg. Based on this data, about 4,300 kg of consumed abrasive was estimated to be collected
together with the wastewater.
*2) To ensure sub-criticality, it is important to limit the weight of a single piece of scraps 16 kg that may fall in the reactor core area during the cutting work. The shroud head is cut
into four parts as shown in the photos below on the right.

Cutting the main rebars of the biological shielding
wall in the element test

Cutting the shroud head into four parts in theelement test
©International Research Institute for Nuclear Decommissioning6.4.2.6 Side-opening investigation method: List of equipment and devices No.75
No.
1

Name of equipment
and device
Entire work cell

Outlines
A structure to prevent radioactive dust from spreading during the
cutting and investigational works by maintaining negative
pressure.

No.

Name of equipment anddeviceOutlines

11*

AWJ/WJ hybrid cutting tool
head

Four types of cutting tool heads are prepared, each of whichis capable to bore a hole with a diameter of φ480, 400, 300,
and 220 mm.

12*

Crawler

A mechanism that is attached to the AWJ/WJ hybrid cutting
tool head rigidly and moved forward and backward in theguide tube Guide rollers and rotation preventing
mechanisms are attached to the outer surface of thecrawler. They come into contact with the inner surface ofthe guide tube, inside which the crawler is moved, and keep
it at the center of the guide tube.

2

Support structure

Temporary storage for tool box ACx during lifting/hoisting. Usedfor docking and undocking with tool box AC0

3

Connection room

A structure to enclose the joint between tool boxes ACx and AC0
with the structural members of the entire work cell. Function toprevent contamination during docking and undocking if, by any
chance, it occurs.

4*

Tool box AC0

A structure connected to the multi-use plate mounted on the R/Bwall and equipped with a two-stage isolation valve. Equippedwith a cap to block direct ray when none of tool boxes ACx areconnected.

13*

Tool box AC5

A structure to station a mechanism to transfer theinvestigation equipment developed for use in the topopening investigation method to the reactor core area

A structure used to install the light guide tube, PCV guide tube,
and RPV guide tube. Equipped with an expandable mandrel

14

Wastewater collection anddischarge system

A system that is composed of three turbo-fan units andused to collect cutting scraps (concrete and rebar scraps)
The collected wastewater is filtrated to separate it fromcutting scraps.

15

Platform

A steel-frame structure to distribute the weight load of theentire work cell, tool boxes, and utility supply equipment
installed on the roof of the air-conditioning equipment room,
not only on the concrete slab roof but also on the R/B wall

16

Maintenance unit

A facility planned to be built in a ground-level area toprovide an environment for the preconditioning anddecontamination of the cutting tools and guide tubes thatare installed on tool boxes ACx when tool change is
implemented

5*

Tool box AC2

6*

Light guide tube

A guide tube to cover the route from AC0 to the biologicalshielding wall

7*

PCV guide tube

A guide tube to cover the route from AC0 to PCV An EPDM
rubber sealing is attached to its end surface to protect theboundary. Guided by guide rollers and rotation preventing
mechanisms to a position that forms an exact concentric
relationship with the light guide tube

8

PCV sleeve

Equipment to support the PCV guide tube by the biologicalshielding wall against the axial load exerted to it by filling the gap
between the biological shielding wall and itself with cement milk.

9*

RPV guide tube

A guide tube to cover the route from AC0 to RPV Guided by
guide rollers and rotation preventing mechanisms to a position
that forms an exact concentric relationship with the light guide
tube

10*

Tool box AC3

A structure to house the AWJ/WJ hybrid cutting tool head in it
and cut the biological shielding wall, PCV, RPV shield wall,insulator, RPV, and shroud head*) Some of main equipment and devices, especially for cutting investigation
holes, in this table are further explained in detail in the pages below.

©International Research Institute for Nuclear Decommissioning6.4.2.6 Side-opening investigation method: Specifications of equipment and devices
No. 4: Tool box AC0<Outlines>
A tool box permanently installed on the entire work cell. It is fixed to the multi-use
plate attached to the R/B wall with anchor bolts. A cap (radiation shield) is set toblock direct ray from the reactor core when none of the tool boxes ACx areconnected and no construction work is being carried out either.
<External appearance>

Isolation valve 2

Flame

Silent block(Anti-vibration bush)[Direct ray shielding function]· A cap (radiation shield) is provided to block direct ray from the reactor core whennone of the tool boxes ACx are connected and no construction work is being
carried out either.
[Radioactive dust spread prevention function]· Two sets of isolation valves are provided so that the opening (guide tube) is shutoff and sealed airtight even if one of them fails.

Multi-use plate

Flat seal<Main functions and features>[Configuration]· The multi-use plate is fixed to the R/B wall with anchor bolts via flat seal.
· The frame is also fixed to the R/B wall to enable it to bear part of the weight loadof the connected ACx via anti-vibration bushes.
· Two sets of isolation valves are provided, which contribute to the prevention of
the spread of radioactive dust.
[ACx guiding function]· The guide pin mates with the guide hole on ACx to guide it at the right position
when docking tool box ACx. After docking, the rotation lock is turned andengaged to secure the connection between AC0 and ACx.

Isolation valve 1

R/B wall

No.76

Radiation shield
Rotation lock

Guide pin

<Main component specifications>[Isolation valve]· Product of VAT, Series 192 UHV – DN 40/1000 mm (supplier ref. 19260-PE44)[Rotation lock mechanism]· Remotely controlled electric-driven lock mechanism©International Research Institute for Nuclear Decommissioning6.4.2.6 Side-opening investigation method: Specifications of equipment and devices
No. 5, 10, 13: Tool boxes ACx

No.77<Outlines>
Tool boxes to guide and transfer the AWJ/WJ hybrid cutting tool head, guide tube, and other equipment to penetrating locations<Main functions and features>[Configuration]
The following three types of tool boxes are prepared.
· AC2: Used to transfer guide tubes· AC3: Used to transfer the AWJ/WJ hybrid cutting tool head
· AC5: Used to transfer the investigation equipment
Guide tubes and other tools in each tool box are replaced with other setsin the maintenance unit.
[Function to move tools forward and backward]· The trolley guide rail is installed on the ceiling of the tool box. The trolley
moves along the rail, pushing and pulling tools between the tool box andtarget penetrating locations.
· Besides the trolley, a pair of winches is provided to pull the crawler if by
any chance the trolley fails to function. Tools can be withdrawn bypulling a wire rope connected to the crawler by a winch.
[Double-sealing function]· Double-layer EPDM sealing is installed on the surface of the flange of
ACx for connection with AC0. The sealability between AC0 and ACx issecured by pressing the flange of AC0 against the sealing.

Tool box AC3 bird’s-eye viewA

Trolley

Rail

B

A

<Main component specifications>· Main dimensions (approximate values): W2200 mm×H2300mm × L18000 mm (AC2): W2200 mm × H2300 mm × L15000 mm (AC3): W2200 mm × H2300 mm × L11500 mm (AC5)· Approximate weight: 30,000 kg (when equipped with the heaviest tool)
EPDM seal

Winch

Winch

EPDM seal

Enlarged view from arrow B

Cross section A-A©International Research Institute for Nuclear Decommissioning6.4.2.6 Side-opening investigation method: Specifications of equipment and devices
No. 6, 7, 9: Guide tubes

No.78<Outlines>
The light tube, PCV guide tube, and RPV guide tube are laid out in a concentric configuration in this order with the light tube placed at the outermost part. The rollers and rotation
preventing mechanisms on the outer surface of the PCV guide tube contact the inner surface of the light guide tube to maintain an exact concentric relationship between the two while
they are being moved. The rollers and rotation preventing mechanisms on the outer surface of the RPV guide tube work similarly. Thus, the three guide tubes are aligned in an exact
concentric manner. In addition, an EPDM rubber sealing is installed on the end surface of the PCV guide tube so that the boundary is protected by pressing the PCV guide tube and thesealing against the PCV outer surface.
<Main functions and features>[Configuration]· Equipped with guide rollers and rotation preventing mechanisms on its outersurface· Equipped with the anti-rotation stop on its inner surface
Rotation
Side view
Anti-rotation stop
preventing· EDPM rubber sealings are installed on the grooves on the end surface of the PCV
mechanism
guide and light guide tube.
· Mechanical sealings are installed on the other end of each guide tube andconnected to the multi-use plate.
[Guiding function]· The guide rollers keep the gap between two guide tubes constant, so that their
exact concentric relationship is maintained while they are being moved. In
addition, the anti-rotation stop and rotation preventing mechanisms (rotation
Guide roller
prevention mechanism) suppress the rotational movement of the guide pipes.
Cross-sectional[Double-sealing function]
drawing· Pressing the end surface of the guide pipes against the PCV outer surface
together with the EPDM sealings installed on it secures an airtight connection
Illustration of three guide tubes
and protects the boundary.
RPV GUIDE TUBEaligned in an operation position· The gap between the light guide tube and multi-use plate and the gap between
the guide tubes are sealed using mechanical seals.

<Basic specifications>

Guide
tube

Material

Outer diameter/thickness/length
Unit: mmLight
guide tube

Stainlesssteel pipe

φ660.4/6.4t/6622L

PCV
guide tube

Stainlesssteel pipe

φ457.2/6.4t/8741L

RPV
guide tube

Stainlesssteel pipe

φ267.4/6.4t/11274L

EPDM seal

Example ofmechanical seal
PCV guide tube head©International Research Institute for Nuclear Decommissioning6.4.2.6 Side-opening investigation method: Specifications of equipment and devices
No. 11: AWJ/WJ hybrid cutting tool head

No.79

<Outlines>
A penetrating head that combines a standard waterjet (WJ) mechanism and abrasive waterjet (AWJ) mechanism (hybrid configuration). It is used as the head of the processing
apparatus to open holes in the structures between the biological shielding wall and PCV.

<Main functions and features>[Configuration]· WJ nozzle used to chip concrete layers.
· AWJ nozzle used to cut rebars and steel plates· Cutting scrap suction port to vacuum and collect concrete and metal scraps· Camera to monitor the condition of the holes during cutting (A microphone isembedded in the camera to check noises generated during the AWJ cuttingwork)· A 3D scanner to detect the position of rebars[Penetrating position guide]· A 3,000-mm-long crawler is connected to the near end of the tool head rigidly,
and guide rollers and rotation preventing mechanisms (rotation prevention
mechanism) on the crawler come into contact with the inner surface of the lightguide tube to maintain the tool head at the center of the light guide tube while thetool head advances.
[Concrete layer penetrating function]· Chipping concrete layers with WJ. Two nozzles are installed on the WJ nozzle.
They are laid out to point different directions both inclined outwardly as shown in
the photo on the right so that the WJ head can bore a φ480-mm hole.
[Metal layer penetrating function]· Penetrating steel frames and plates with AWJ to open a φ400-mm hole in them.
[Collection function]· Collecting concrete and rebar scraps generated by the cutting work through the
cutting scrap suction port
<Basic specifications>[Entire machine]· Main dimensions (approximate values): φ440 mm × L3000 mm[Metal layer penetrating mechanism]· Abrasive water jet with garnet abrasive

WJ nozzle head

AWJ nozzle head

WJ nozzle(It rotates around its
axis and also moves
horizontally in the tool
head radial direction)

AWJ nozzle 1(It moveshorizontally in thetool head radial
direction)

Suction port forcut pieces

Camera(It can be stored in the head
when cutting )3D scanner
AWJ nozzle 2(It moves horizontally in thetool head radial direction)©International Research Institute for Nuclear Decommissioning6.4.2.6 Side-opening investigation method: Specifications of equipment and devices
No. 12: Crawler

No.80<Outlines>
The AWJ/WJ hybrid cutting tool head is connected to the crawler and moved forward and backward in the guide tube. Guide rollers and rotation preventing mechanisms areattached to the outer surface of the crawler 0. They come into contact with the inner surface of the guide tube, inside which the crawler is moved, and keep it at the center of theguide tube. In addition, the pipes to supply water and abrasive to the cutting tool head, pipes to collect and discharge wastewater, and cables for electric instruments are installed on
the crawler.
<Main functions and features>[Configuration]· Crawler is equipped with guide rollers and rotation preventing mechanisms on its outersurface.

Anti-rotation stop

[Guiding function]· The guide rollers keep the gap between two guide tubes or the gap between the guide tube
and the crawler constant so that an exact concentric relationship of the two guide tubes ismaintained while they are being moved. In addition, the rotation preventing mechanisms(rotation prevention mechanism) engage with the anti-rotation stop provided on the innersurface of the light guide tube to keep the tool head in the center of the light guide tube
while it is being moved forward and backward.
· The crawler provides a passage for pipes and cables run from the tool box to the tool headto support its operation. It is constructed using a chain-drive mechanism, so that the pipes
and cables can move smoothly in it when the tool head is moved forward and backward.

Rotation preventing
mechanism<Basic specifications>

CrawlerTools to be connected

Material

Outer diameter/length
Unit: mm

CR1

Cutting tool head H1(biological shielding wall)

Stainless steelpipe

φ457/3650L

CR2

Cutting tool head H2(PCV, reactor shield wall,insulator)

Stainless steelpipeΦ355.6/3650L

CR3

Cutting tool head H3(RPV, shroud head)

Stainless steelpipe

φ208/3190L

CR4

Investigation equipment

Stainless steelpipe

φ208/4600L

Guide roller
Rotation preventing
mechanism

Cutting tool head

Crawler

Guide roller

Illustration of the crawler connected to the cutting tool head©International Research Institute for Nuclear Decommissioning6.4.2.6 Side-opening investigation method: Layout design

No.81

Platform for the entire work cell
⚫ The total weight of the structures and equipment installed on the roof of the air-conditioning equipment room,
including the entire work cell, was estimated to be about 140 t (80 t for those installed on the negative-pressurearea). The concrete slab roof was not strong enough to bear the weight of all the structures and equipment alone.
For this reason, a platform to hold the structures and equipment was designed based on the information on theirweight and layout plan. A design plan to support the platform not only with the concrete slab roof (chiller mountingbase) but also with the pillars of R/B on the east side and the side walls of the air-conditioning equipment room
was adopted to distribute the weight load. Based on this plan, the specifications of the platform were determined.

Information wasused as input forcalculation.

Platform plan drawing(Especially the platform in the negative-pressure area where the load
is concentrated was designed according to the layout.)
Insertthe end of the
鉄骨梁端部を外壁に埋込むsteel
beam in the wall

Layout and approximate weight of the structuresand equipment installed on the roof of the airconditioning equipment room

プラットフォーム鉄骨梁
Steelplatform

Wall thickness:
500 mm
壁厚500mm

Illustration of the design to distribute theweight to the R/B pillars on the east side
(Insert the end of the steel beam in thewall to hold it with the compression forceof the concrete.)©International Research Institute for Nuclear Decommissioning6.4.2.6 Side-opening investigation method: Overview of system configuration

No.82

A system to realize the negative-pressure control system described in the page above was designed; system diagram,
piping list, and valve list were created; and information to grasp the scale of the facility was organized. Based on the
results of these actions, the weight of the structures and equipment listed in the page above was estimated.
R/B side

Valve list, piping list, etc.

System drawing of the equipment installed on theroof of the air-conditioning equipment room
(ACx is docked with AC0)

©International Research Institute for Nuclear Decommissioning7. Summary

No.83

7.1 Investigation and development planningThe obtained information was similar to that from the needs research in FY2016. Schedule forinvestigation plan was updated, however there was no change that the data should be obtained as soon
as possible. Investigation plans were updated in a step-by-step manner with the aim of reflecting themin ① the next step of the RPV inside investigation and ② the study of fuel debris retrieval methods.
There was no change in the development plans.
7.2 Investigation method planning
Exposure assessment confirmed that there is no problem in the safety assessment. However,maintaining negative pressure inside the PCV will be necessary during investigation using the topopening method as radioactivity concentration in the R/B would increase. As a result of the assessment,
it was concluded that investigation of the side-opening method can be carried out in the condition of aslight positive pressure inside PCV.
7.3 Study on the investigation auxiliary system
Necessary ancillary systems were clarified and suggested as requirements based on the safety
requirement list and exposure assessment result. Redundant designs were devised for radiation anddust monitoring systems as well as gas control systems in preparation for emergency.
7.4 Development of access and investigation equipment
As to element technologies required for each work step, verification tests were conducted to verify
the feasibility of technologies, and the information and parameters necessary for a detailed design wereobtained. In addition, the preliminary calculation of supply amount for utilities required each work stepwas estimated, and work steps and the specifications of the facility and equipment were determinedbased on the results of element tests.
©International Research Institute for Nuclear Decommissioning