Subsidy Project of Decommissioning and Contaminated Water Managementin the FY2015 Supplementary Budgets

Development of Technology for Investigation
inside RPV
Final Report

March 2018
International Research Institute for Nuclear Decommissioning (IRID)
All Rights Reserved. International Research Institute for Nuclear Decommissioning©International Research Institute for Nuclear Decommissioning

CONTENTS (1/3)

No.1

1. Research Background and Purposes
2. Project Goals
3. Implementation Items, Their Correlations, and Relations with Other Research
4. Schedule
5. Project Organization Chart
6. Implementation Details(1) Prerequisites (and Items Implemented in and before FY2015)(2) Required Safety Requirements(3) Required Functions and Equipment for Top-Opening Investigation
Method
6.1 Development of Equipment to Access the Reactor Core from the Top
6.1.1 Development of Equipment to Access Down to the RPV Head
(1) Connecting the Tool Box and Guide Pipe(2) Equipment for Processing Work up to the RPV Head
(3) Tests for the RPV Head Spare Nozzle Removal(4) Test Results of the RPV Head Spare Nozzle Removal©International Research Institute for Nuclear Decommissioning

CONTENTS (2/3)

No.2

6.1.2 Development of the Boundary Maintenance Equipment and Work Cell
(1) Exposure Assessment Results and New investigation Policies(2) Work Cell and the Plan for Preventing Contamination Spread (under Negative
Pressure Environments in the PCV)
(3) Study on the Method the Negative Pressure Control Method for the Work Cell
(4) Work Cell Appearance(5) Changes of the Guide Pipe Sealing Structure(6) Results of the Guide Pipe Sealing Test
6.1.3 Development of the Inside-Reactor Opening Equipment(1) Study on Design of Opening Equipment inside the Reactor(2) Assembly of the Prototype Inside-Reactor Opening Equipment(3) Element Test: (i) Verification Test on the Cutting Conditions; (ii) Remote
Operability Test
6.2 Development of the Equipment to Access the Reactor Core from the Side
(1) Conclusions from the Study on the Equipment Concept(2) Boundary Formation(3) Drilling of investigation Holes(4) Concepts of the Boundary Maintenance(Preventing Dust Diffusion)©International Research Institute for Nuclear Decommissioning

CONTENTS (3/3)

No.3

6.3 Development/Selection of the Investigation Method for the Reactor Core
(1) Investigation Equipment A (for Prior Confirmation): Investigation
Specifications and Requirement Specification of Equipment(2) Investigation Equipment B (for the Full-Scale Investigation):
Investigation Specifications and Requirement Specification of
Equipment(3) Investigation Equipment C (for the Full-Scale Investigation):
Investigation Specifications and Requirement Specification of
Equipment(4) Study Results
6.4 Designing the Entire Investigation Equipment System and Planning theinvestigation(1) Study on the Processing and Investigation Flows (for Top-Opening
investigation)(2) (Draft) Overall Plan of Investigation
7. Summary©International Research Institute for Nuclear Decommissioning1. Research Background and Purposes

No.4
Top-Opening investigation method[Purpose of investigateing the inside of the RPV]
Obtain basic information about the inside of the RPV
toward fuel debris retrieval (fuel debris distribution, dose,
structure conditions, etc.).
[Purpose of the technical development]
Clarify investigation needs and targets to develop thetechnology that enables the investigation.
Side-opening
investigation
method[Use of the Project’s achievements]
Conduct the investigation at the Units using thetechnology developed under the R&D project and thereby
obtain information that will contribute to the study on fueldebris retrieval and criticality control.

Development of Technology for
Investigation inside RPVInvestigationof Units

Information about the RPVinterior(Visual information, dose rate,etc.)

Study on the method andequipment design for
retrieving fuel debris©International Research Institute for Nuclear Decommissioning2. Project Goals
What to do

Generate and update investigation anddevelopment plans
Develop equipment to access the reactor
core
6.1 Development of equipment to accessfrom the top

No.5
Target achievement index
Multiple ideas on the RPV-interior investigation processes are studied and compared, optimal technology isselected, and the investigation and development plans are generated toward the selection of a fuel debris
retrieval method and the fuel debris retrieval operation or toward the obtainment of permissions andauthorizations for the operation. (Excluded from the “TRL” technology readiness level for the sake of easier
information organization)-

6.1.1 Development of opening
equipment to access down to
the RPV head

The Unit application feasibility of the opening equipment to access down to the RPV head is evaluated.
(Target TRL as of completion: Level 4)

6.1.2 Development of boundary
maintenance equipment andaccess equipment for operations

The Unit application feasibility of the boundary maintenance equipment and access equipment for
operations is evaluated. (Target TRL as of completion: Level 4)

6.1.3 Development of the inside-reactor
opening equipment

The Unit application feasibility of remote-control technology to make holes at reactor internals is evaluated.
(Target TRL as of completion: Level 4)

6.2 Development of equipment to accessfrom the side

6.3 Development/Selection of method toinvestigate to the reactor core
6.4 Designing the entire investigationequipment system and planning theinvestigation

The feasibility of the method to investigate the reactor core through the RPV side-opening is evaluated, themethod concept is designed based on the evaluation results, and the Unit applicability of the method is
evaluated. (Target TRL as of completion: Level 3-4)
The feasibility of the Unit application of the method for investigateing to the reactor core is evaluatedthrough the use of the findings from the project “Development of the Basic and Generic Technology to
Retrieve Fuel Debris and Reactor Internals (Visual and Measurement Technology)”, etc. (Target TRL as ofcompletion: Level 4)
Safety requirements and responses thereto that would need to be regulated and discussed are identified,
and the entire work flow from the equipment installation at the R/B operation floor to the on-site surveys
and the post-investigation treatment is in place. (Excluded from the “TRL” technology readiness level forthe sake of easier information organization)©International Research Institute for Nuclear Decommissioning3.1 Implementation Items in the Research Project
#
-

6.1.1

6.1.2

6.1.3

6.2

6.3

6.4

Items
Generate and update
investigation anddevelopment plans

Achievements up to FY2015• investigation flowchart generated• Studied the needs identified in otherprojects and drew up investigation anddevelopment plans

Items implemented in FY2016-2017

Action policy/Solutions• Studied the viability of the side-opening investigation method• Desk-study the side-opening investigation method in FY20162017.

• Planned the remote-control works (positioning andinstallation/anchoring)• Studied the concept of the equipment to • Explored a method to prevent a hydrogen explosion fromopen the part between well cover andhappening during processing work
the RPV head
• Method to prevent the fall of fragments from processing work
• Conducted an elemental test in FY2014
and the methods to fixate and collect them
• Studied and understood the migration behavior of radioactive
materials including radioactive dust
• Established the remote-control procedures for installing andBoundary maintenance• Drew up the basic concept; andanchoring the boundary maintenance equipment and madeequipment
conducted a test on sealing to verify theseismic design
basic structure in FY2015• Method for verifying the installation and post-investigation
treatment• Structural (seismic) and shielding designs• Conducted a study on handling tools
Access equipment for• Studied the concept in FY2015• Air (conditioning) system
operations (work cell)• Monitoring plan (for door opening/closing and during theoccurrence of an abnormality)• Tool head and the mechanism to remove fragments from
Development of the•Conducted an element test and confirmed
processing work
technology to make holes the feasibility of processing work to make(Access from the top: for narrow or complicated shapes)
inside the reactor (the part holes in reactor internals inside the RPV,
• Guide pipe insertion and the tool transfer mechanism
down to the upper grid
the key process to access the reactor core
(Access from the top: approx. 20 m below)
plate)•Studied the concept in FY2015• Remote control and collection of equipment• Determined the viability of the side-opening investigation
Development of themethodequipment to access from
• Designed the concept of side-opening investigation method
the side• Designed equipment for side-opening investigation method• Narrowed down investigation instruments such as cameras
Development of theand detectors
technology to investigate• Method to access the reactor core (wire, telescope, guide pipe,
the reactor core and RPV • Studied the concept in FY2015
etc.)bottom part
• Rescue methods at the time of failure• Studied methods to investigate the reactor core and the RPV
bottom part and on their precision requirements• Elaborated investigation flow using equipment mentioned in
Designing theSections 5.1-5.3 and its work plans (area decontamination,
investigation equipment
processes from preparation to completion, and equipment
system and planning theretrieval/decontamination /maintenance, etc.)
investigation methods• Studied safety requirements
Opening equipment toaccess the part down to
the RPV head

No.6

• Equipment design and element test (FY2016-2017)➢ Confirm, through partial prototyping, the procedures andequipment for remote-control works• Equipment design and element test (FY2016-2017)➢ Verify, through partial prototyping of the equipment, themethod and equipment➢ Verify the compatibility with the opening equipment• Equipment design (FY2016-2017)➢ Verify the compatibility with the opening equipment• Equipment design and element test (FY2016-2017)➢Decide whether it’s necessary to prototype the equipment andconduct a verification test on the equipment or method after
designing the equipment and, if necessary, conduct the test

➢ Establish a method focusing on securing boundaries➢ Conduct a study on the equipment specifications• Equipment design and element test (FY2016-2017)➢ Verify investigation method using partial elements (shroud
head, upper grid plate, etc.)➢ Build HP, scrutinize exposure assessment conditions, andconfirm the investigation viability in a slightly -positivepressure environment➢ Generate investigation flowcharts©International Research Institute for Nuclear Decommissioning3.2 Relationships among Implementation
Tool box(Processing
and
Items

•Study on utility functions and systems•Study on the method/carrier to carry in/out theequipment

Work cell Section 6.1.2

Investigation equipment)

Equipment for processing work
~ Opening down to the RPV
head Section 6.1.1

Tool box transport cart

Overview of the Top-Opening
Investigation method

No.7

Environment adjustment andwork-area making after fuelremoval from the pool
Work for creating a negative
pressure environment inside
the PCV, etc.
 Outside the scope of thisproject• Opening equipment• Equipment to make smalldiameter holes, etc.

Boundary maintenanceequipment Section 6.1.2•Tool box
•Guide pipe
•Sealing mechanism (resin packing), etc.
Equipment to perform
processing work for the PCV
head

Equipment to perform
processing work for theheat-retention material

Equipment to perform processing
work for the RPV head

Opening equipment for reactor internals ~Opening inside the reactor (down to theupper grid plate)

Guide pipe sealing part
System configuration
for boundary
maintenance

The whole system andinvestigation plans 
Section 6.4

Equipment to investigate down to the reactor
core and the bottom part of the RPV
 Section 6.3• Tool head (abrasive water jet nozzle)• Access equipment (stored in the tool box) ,etc.

Abrasivewater jetReactor corearea
For the full-scale
investigation

investigation equipment

Access equipment for the
opening of reactor
internals

Development of equipment to accessfrom the side Sections 6.2 and 6.3*

• Suspension lowering
equipment• Camera• Dosimeter• Horizontal-motion
mechanism, etc.

For PriorConfirmation

 Section 6.1.3

Access (suspension lowering)equipment*investigation tools (such as camera, dosimeter and the like only)

Tool head
Overview of the side-opening investigation
method©International Research Institute for Nuclear Decommissioning3.3 Relationships with Other Research

Study and Research on method
and equipment to retrieve fueldebris[Input]investigation needs (Matters thatneed to be investigated toward thestudy on debris retrieval andcriticality control)

Study and Research on
criticality control

Development of technology forinvestigation inside RPVInvestigation of Units[Input]Site conditions, etc.

Study and Research to identify
conditions inside the reactor[Output]
Information about the RPV interior(Visual information, dose rate, etc.)

Equipment manufacturing,
mockup, etc.

The Project[Input]Estimated information about
the inside of the PRV(structure conditions, etc.)

No.8[Output]
Prerequisites andrequirements for the Unit
investigation

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

©International Research Institute for Nuclear Decommissioning4. Schedule

No.9
FY2016

Implementation items

FY2017

Formulate and update
the plans

Formulate and update
investigation and development
plans

HP
Study multiple
methods

Evaluate the applicability,and judge whether toproceed to the next phase

Formulate and update
the investigation plan
Study the applicability of the side-opening
investigation method

HP

Generate the investigation flowcharts

Narrow down themethods

6.1

Development of equipment
to access from the top

HP
Study/compare/evaluate multiple methods

Study construction work flow

6.2

HP
Verify the selected technology’s remote workability
at the Units

Design the concept (Study the viability of multiple
proposals)

Development of equipment
to access from the side

Confirm the remote workability

Design equipment

Element test (Verify the feasibility of the concept)
Prototype the equipment and test (Confirm the remote workability)
Uptake of evaluation
results

6.3

Uptake of the side-opening
investigation method

Determine the validity ofthe method

Development/Selection of
the method to investigate
down to the reactor core

• Designed the concept of side-opening
investigation method

Determine whether it’snecessary to conduct on-site
validation

HP

HP

Designed equipment for side-opening
investigation method

6.4

Designing the entire
investigation equipment
system and planning theinvestigation

HP
Study safety requirements

Verify the viability of the Top-Opening
Investigation method at exposure
assessment

Study the work flow from the equipment installation to its removal, and generate the investigation flowcharts©International Research Institute for Nuclear Decommissioning5. Project Organization Chart

No.10(Main) official in charge: International Research Institute for Nuclear Decommissioning (IRID)(Deputy) official in charge: Toshiba Energy Systems & Solutions Corporation (International Research Institutefor Nuclear Decommissioning)

Toshiba Energy Systems & Solutions
Corporation
1) Generate and update investigation anddevelopment plans2-1) Develop the equipment to access thereactor core from the top(i) Develop the opening equipment toaccess down to the RPV head(ii) Develop the boundary maintenanceequipment and the access equipment for
operations(iii) Develop opening equipment for upper
grid plate3) Develop/Select method to investigate
down to the reactor core4) Design entire investigation equipment
system and plan the investigation

IHI Corporation• 2-1) (i) Develop opening equipment toaccess the RPV head
IHI Corporation• 2-1) (ii) Develop boundary
maintenance equipment
KIMURA CHEMICAL PLANTS CO.,LTD.
• 2-1) (ii) Develop access equipment for
operations

Tokyo Electric Power Company
Holdings, Inc.

International Research Institute for Nuclear Decommissioning(Head Office)Cooperating development projectteams

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

Upgrading the Comprehensive Identification ofConditions inside Reactor

Hitachi-GE Nuclear Energy, Ltd.

Mitsubishi Heavy Industries, Ltd.

1) Generate and update investigationand development plans2-1) Develop the equipment to accessthe reactor core from the top(iii) Develop opening equipment forupper grid plate4) Design entire investigation equipment
system and plan the investigation

1) Generate and update investigationand development plans2-2) Develop the method and equipment
to access the reactor core from the side

Development of Fundamental Technology for
Retrieval of Fuel Debris and Internal Structures;
Upgrade the Approach and Systems; andConduct Sampling
Development of Technology for Collection,
Transfer and Storage of Fuel Debris
Development of Technology for Criticality
Control Methods
Grasp the Fuel Debris Characterization
Development of Technology for Investigation
inside PCV
R&D for Treatment and Disposal of Solid
Radioactive Waste

Development of Repair Technology for Leakage
Points inside PCV
Hitachi Power Solutions Co.,Ltd.
• 2-1) (iii) Support design and tests inthe development of opening
equipment for upper grid plate
Hitachi Power Solutions Co.,Ltd.
• 2-1) (iii) Design, manufacture andconduct a test of element test
machines for the development of
opening equipment to the upper grid
plate

AREVA ATOX
D&D SOLUTIONS Co., Ltd. (ANADEC)• 2-2) Develop method and equipment toaccess the reactor core from the side

SHIMIZU CORPORATION• 2-2) Evaluate integrity of Unit 1’s R/B
through an access to the reactor corefrom the side
Kajima Corporation• 2-2) Evaluate integrity of the R/Bs of
Units 2 and 3 through an access to thereactor core from the side

Note: Organized companies were selected by competitive bidding.
©International Research Institute for Nuclear Decommissioning6. Implementation Items: (1) Prerequisites (and Items Implemented in and before FY2015)
Items

No.11

Content

Investigation needs(Items implemented in andbefore FY2016)• Early access to the reactor core and data collection will allow us to reflect the data in the specific design of debris retrieval
equipment.
• The following two pieces of data need to be collected: visual information and dose rate.

Target Unit
(Items implemented in andbefore FY2016)• Top-opening: Unit 3• Side-opening: Unit 2

Access route(Items implemented in andbefore FY2016)• Top-opening: right above the RPV spare nozzle• Side-opening: rooftop of the air conditioning room east to the R/B

Assumed air dose rate
(Max.)

Drywell: 16 Sv/h
Inside the reactor (in the vicinity of the steam dryer and steam separator): 800 Sv/h
Inside the reactor (in the vicinity of the reactor core): 5,000 Sv/hAssumed structure
conditions

part between well cover and shroud head: (Presumably) in a sound condition
part below the upper grid plate: it may have major damage; the structures below the upper grid plate were defined as debris andprocessing work for the part to the shroud head was performed before conducting theinvestigation. The deepest part of the bottom part of the RPV was accessed based on theassumption that the melting of the fuel, structures, etc. in the reactor core starts at theircenter.

Light penetration rate
(in fog/mist)

46% (the absorption coefficient value for Unit 1 measured under stricter conditions than the internal PCV investigation ones:
0.511)

Work site and remote
operability

Work site: operation floor Assumed work area: 1.3m above the operation floor Assumed work area environment: 1 mSv/h
Equipment installation: manually by workers Processing work and investigation: remotely-operated

Fragments from processing
work

From aspect of criticality control, the top priority is to prevent fragments from falling into the reactor core.

Boundary(Items implemented in andbefore FY2016)

A boundary is built in the PCV. A negative pressure environment is created inside the work cells that are installed on theoperation floor and at the rooftop of the air conditioning room to prepare for a situation where radioactive materials leak toward
their openings.
©International Research Institute for Nuclear Decommissioning6. Implementation Items (2) Required Safety Requirements
Safetyrequirements

No.12

Assumed events

Responses and their policies

Prevent radioactive
materials fromleaking to the gas
phase

Migration of radioactive
materials to the gas
phase during an operation

Build a boundary in the PCV. Create a negative pressure environment for the work area as a measure against
contamination spread. Monitor works, ventilate the R/B, etc. during operation.
Assess public exposure doses at the site boundaries and worker exposure doses inside the R/B based on theradioactive dust amounts that would be generated from the cutting of structures in the PCV, RPV and reactor.
Conduct Top-Opening Investigation after creating a negative pressure environment in the PCV, given thepossibility of the inside of the R/B getting contaminated during processing work. For side-opening investigation,
confirm if the exposure standard value will be satisfied even when the PCV has, as it does currently, a slightlycompressed environment.

Prevent radioactive
materials fromleaking to the liquid
phase

Migration of radioactive
materials to the liquid
phase during operation

Continue to study, while referring to the study on the water system, how to assess the concentrations when watercontaining radioactive materials flows to the outside of the PCV  to the torus room or into the PCV  to theinside of the pedestal.

Maintain the fueldebris cooling
function

Loss of the fuel debris
cooling function

Select an access route that avoids the piping currently in use.

Control criticality andmaintain subcriticality.

Occurrence of criticality
resulting from a change ina fuel debris shape due tothe fall of a fragment fromprocessing work

Find an access route and method that will have less processing objects and cause less falls of fragments in thereactor core. Explore, for the side-opening investigation, an approach that enables the shroud head to be cut into
as tiny pieces as possible and thereby reduces the risk of recriticality due to the fall of a fragment in the reactor.
Continue to conduct a study, in cooperation with the criticality control project, on the evaluation of the weight offragments from the cutting work that would affect criticality.

Prevent fire or
explosion

Hydrogen explosion
during a processing work

Introduce, for the top-opening investigation, anti-hydrogen measures for the work to make small-diameter holes
at the PCV head and the RPV head.

Prevent the fall of aheavy weight object

Dispersion and diffusionof radioactive materials
resulting from the fall of aheavy weight object

Design equipment that does not cause the fall of a heavy weight object (multiplexing, diversification, etc.).

Prevent the collapseof the R/B during theconstruction work forthe investigation

Collapse of the R/B due tothe installation ofequipment

Design the support structure in such a way that the floor slab of the air conditioning room (above which a work
cell is to be installed for the side-opening investigation) withstands the load of the work cell and other equipment.
Evaluate the seismic resistance of the R/B walls against the investigation hole perforation and make sure that the
impact of the work will be minor.
©International Research Institute for Nuclear Decommissioning6. Implementation Items: (3) Required Functions and Equipment for the Top-Opening investigationNo.13
The diagram below shows the functions and equipment necessary to conduct the investigation all the while ensuring safety (Evaluation
items are omitted there.)
PurposeRequired functions

Investigate the RPVinterior

Obtain basic
information about
the RPV interior

Required equipment(Development items)

Main capabilities/Element
technology

Section 6.3
investigation andsuspension-lowering
equipment•Accessibility to narrowareas•Visibility in fog/mist•Radiation resistanceEstablish the access
route

Sections 6.1.1 and 6.1.2
Equipment to provide processing
work for the structures located on
the access route•Workability at narrow areas•Remote operability•Down-size of the accessequipment

Confine radioactive
materials

Section 6.1.2
Boundary maintenanceequipment(Guide pipe and tool box)

•Sealing performance at
the interfaces

Prevent contamination
spreadSection 6.1.2
Work cell• Negative pressure control• Instruments for handlingequipment in the cell

Prevent hydrogen
explosion

Section 6.1.1
Equipment to make smalldiameter holes• Processing method that
does not use fire

Monitor the work
environment

Monitor dusts, criticality,
etc.

Obtain visual
information

Obtain dose rate data

Ensure safety
Section 6.1.2
Work cell

Section 6.1.2
Boundary maintenance equipment(Guide pipe and tool box)

Sections 6.1.1 and 6.1.2
Equipment to provide
processing work for the
structures located on theaccess route

Section 6.3investigationand suspensionlowering equipment

Outside the scopeof this project

Element tests
conducted in FY2017
Desk-studied in FY2017
or applied otherresearch achievements©International Research Institute for Nuclear Decommissioning6.1 Development of Access Device from the Top to the Reactor Core

No.14

6.1.1 Development of the Opening Device for Accessing the RPV Head
 Outline of schedule
#

Items

FY2016

Achievements up to FY2015• Studied the concept of theequipment for opening well
Opening equipment
cover, PCV head, RPV heatto access the part
6.1.1
retention frame, and PRV head
down to the RPV
head• Conducted an elemental test in
FY2014Formulate and update the investigation
plan
Conceptual design (Comparison and Items implemented in and before FY2016⚫ The RPV spare nozzle part was selected as the access route for its
workability and the amount of processing-work objects thereon.
⚫ The policy to collect fragments from processing work in a tool box was
adopted, instead of storing them in a container, and to dispose of themwith the tool box.
⚫ The following structure-processing methods were selected.
Structure

MethodWell coverCore boring

PCV head

Small-diameter opening: machining*
Large-diameter opening: abrasive
water jet (AWJ) The finding of the PCV
Maintenance Technology Project
was referred to.

Heat-retention
material

AWJ

RPV head(spare nozzle part)

Small-diameter opening: machining*
Large-diameter opening: AWJ
Verified in an element test in
FY2017.

FY2017

evaluation of multiple methods)

Element test

Basic design (System
configuration, etc.)

Design the
prototype

Detailed design

Test-manufacture
the equipment
Test Items implemented in FY2017<Equipment design>•Opening equipment for the well cover, PCV head*, RPV heat-retention frame and RPV
head was designed.
•The design was elaborated to take account of its relationships with the boundary
maintenance equipment and the access equipment for operations.

Notes<Test-manufacturing and testing the equipment>•A test was conducted using a partial mockup of the actual size and the workability of the
RPV spare Nozzle Removal method was confirmed.
*Method that takes
account of residualhydrogen*Method that takes
account of residualhydrogen Remote operability was confirmed in a test assuming that the guide pipe and thespare nozzle would be located about 100 mm away from the center.

 Remaining issues•Streamline the structure and method to attain higher workability•Conduct a study on the access route other than the RPV spare nozzle part (and thestudy on the processing method for the RPV heat-retention material and RPV head)and conduct an element test to verify the viability*For the PCV head small/large-diameter hole processing method, the findings of a test
conducted in the PCV Maintenance Technology Project were referred to.

©International Research Institute for Nuclear Decommissioning6.1.1 Development of Access Device from the Top to the Reactor Core

No.15

(1) Joint between Tool Box and Guide Pipe
Each processing and investigation equipment are set with the access device(suspension-lowering device), and stored in a tool box which has an air
tight function. Then, a work cell is placed on a transport rail cart and transported to the upper part of the guide pipe. A tool box is carried into a work cellfor each step and replaced to install on the guide pipe.

Upper corner fitting
Suspension-lowering
equipment forinvestigationequipment

Tool box (which
also contains
gate valves andcorner fittings)

Work cell

Tool box

Lower corner fitting

Tool box
transport cart
Gate valve

Twist lock

work area

Gate valve for toolbox
Transport cart(including cleaning
and connection
equipment and twist
locks)

Well cover

Guide pipe

Rail (base shape and tentative
stopper)Gate valve

PCV head

Guide pipe (including auxiliary
equipment)©International Research Institute for Nuclear Decommissioning6.1.1 Development of Access Device from the Top to the Reactor Core(2) Processing device to the RPV Head

No.16

Equipment to process the RPV head spare nozzle
Well cover: element test
conducted in FY2014
PCV head: element test
conducted in FY2014; the similar
technology developed in the PCV
Maintenance PJ
RPV heat-retention material:
element test conducted in
FY2014
RPV head (spare nozzle part):
element test conducted in FY2014 toconfirm whether it can be processedwith AWJOpen the flange

Remove theflangeRemove thenozzleFlange opening
equipment

Equipment tosevere the inner
flangeEquipment tosevere the outer
nozzle

The feasibility of the processing methods is already confirmed at element tests conduced in the previous
fiscal year(s). A test in FY2017 was conducted to confirm the remote operability of the method forremoving the RPV head spare nozzle, which was the most difficult work.
©International Research Institute for Nuclear Decommissioning6.1.1 Development of Access Device from the Top to the Reactor Core

No.17

(3) Testing the RPV Head Spare Nozzle Removal
Garnet supply Hopper

Lifting machine (hoist)

Work floor
AWJ
Pump

Controlpanel

Compressor

Mock guide pipe
RPV Nozzle Removal tool
Mock PCV Head

Mock RPV spare nozzle
Approx. 4,700 mm
Approx. 747 mm(equivalent toactual size)
Water tank
Approx. 730 mm(equivalent toactual size)

Mock processing specimen

Overview of the test facility©International Research Institute for Nuclear Decommissioning6.1.1 Development of Access Device from the Top to the Reactor Core

No.18

(4) Results of the RPV Head Spare Nozzle Removal Test

100 mm from thecentral axis

100 mm from thecentral axis

Removal of fragments of the (upper)
RPV nozzle
Removal of the RPV nozzle flange

Removal of fragments of the (root part of)
RPV nozzle

Processing and removing function tests using prototype equipment were conducted by remote-operation. The
tests verified that the RPV spare nozzle removal method can be remotely operated, including that equipment
can be off-set to work even when the nozzle is 100 mm deviate from the central axis.
©International Research Institute for Nuclear Decommissioning6.1.2 Development of the Boundary Maintenance Device and the Access Device for Operations

No.19

 Outline ofschedule#
Items

FY2016

Achievements up to FY2015

FY2017

Formulate and update the investigation plan

Boundary
maintenancedevice• Formulate the basic concept• Conduct a test on the sealing
function in FY2015 to confirm
the basic structure

Basic design (System configuration, etc.)
Conceptual design (Comparison andevaluation of multiple methods)
Element test

6.1.2

Access devicefor operations(Work cell)• Study the concept in FY2015

Formulate and update the investigation
plan
Conceptual design (Comparison andevaluation of multiple methods)

Detailed design
Verify the viability at an exposure
assessment
Design the
Test-manufacture theprototypeequipment

Test

Conduct a study on the method to build aboundary in relation with the R/B

Basic design (System configuration,
etc.)

Detailed design

 Items implemented in FY2016• A study on the system to control negative pressures for a work cell and on the method tocarry in/out the equipment was conducted.
•Concepts of the opening equipment to access the part down to the RPV head, the boundary
maintenance equipment and the access equipment for operations, were designed.
<Test-manufacturing and testing the equipment>•A summary evaluation concerning the exposure during a processing work for reactor•The guide pipe of the actual size for the boundary maintenance equipment was testinternals under the current slightly-compressed environment was conducted, it was found that manufactured and a test was conducted, confirming the workability of the installation angle
it would be impossible to work in the R/B.
adjustment process.
•A test to confirm the sealing property of the actual-sized guide pipe was conducted and slight Items implemented in FY2017
leakage was observed; however, it is thought that the PCV can maintain its negative pressure
environment with the sealing.
<Equipment design>•The exposure assessment conditions were scrutinized to determine whether it’s possible toconduct the assessment when the PCV has a slightly-positive pressure environment.
The Top-Opening Investigation The PCV should have a negative pressure
environment.
The side-opening investigation  The PCV should have a slightly-positive pressure
environment.
•A seismic problem will arise if a work cell is installed on the shield that is currently in use at
Unit 3 because of the acceptable maximum load of the operation floor and also because theshield is not anchored. ・If the investigation at Unit 3 is conducted, therefore, the shieldneeds to be remodeled or have a work area different from the current one.

 Remaining issues•Streamline the equipment structures and methods to attain higher workability•Rationalize the layout plan for a work cell and its surroundings, and clarify the work-cell
installation method and interface conditions.
•Conduct a detailed study on the system for maintaining negative pressures inside a work cell.
•Confirm the sealing (confinement) between guide pipe and tool box, and optimize the guidepipe seal structure (element test).
©International Research Institute for Nuclear Decommissioning6.1.2 Development of the Boundary Maintenance Device and the Access Device No.20
for Operations(1) Exposure Assessment Results and Future Investigation Policies➢

The side-opening investigation method (No change made to the policy)•Target values are satisfied for activity concentration and site boundary dose.
 The investigation can be conducted in a slightly-positive pressure environment (No problem with theconcentration level inside the R/B).
• Measures, such as dust monitoring and installation of a filter exhaust facility in the R/B will be introduced.

➢

The Top-Opening Investigation method (Changes made to the policy)• The activity concentration level at the (outdoor) vicinity of the R/B is within the limit for personnel. The siteboundary dose is also within the limit.
• If, however, processing work for structures located below the steam dryer is performed, the inside of the
R/B will be contaminated, making it impossible for anybody, even in a full-body mask, to enter.
 The investigation takes place in a negative pressure environment.
(The investigation will be conducted in the negative pressure environment created for the side entry
fuel debris retrieval.
 The investigation schedule needs to be adjusted.)•Dust monitoring will be performed during the investigation.

The following changes will arise if the investigation is conducted in a negative pressure environment.
(i) Structure change of the resin packing for the guide pipe that will be installed at the PCV headConfirmed by an element test.
(ii) Change from the N2 purge system to an exhaust system ⇒ Study on the design.

©International Research Institute for Nuclear Decommissioning6.1.2 Development of the Boundary Maintenance Device and the Access
Device for Operations

No.21(2) Work Cell and the Plan for Preventing Contamination Spread (under Negative Pressure Environments in the PCV)
Differential: boundary (which will be built inside the PCV)Work cellpressure: -60 Pa(g): contamination spread prevention range(inside the work cell)Work cell

Negativepressure

Airlock cell

Negativepressure

Tool box(Processing/investigation equipment)

Outdoor(Atmosphericpressure)-60 PaDifferential pressure:-100 Pa(g)Inside the work cell(Contamination
spread prevention)

Gate valve-160 Pa-100 Pa
ShieldingInside the PCV (tool box)

Well cover

PCV head
Boundary maintenanceequipment

Differential pressure:-160 Pa(g)Pressure relations among the
PCV inside, the work cell, andthe inside/outside(atmospheric air) of the R/B

Negative pressure

To prevent radioactive materials from leaking outside, the inside of a work cell shall have a negative
pressure environment. (The RPV interior investigation, which does not involve fuel debris retrieval, will
only use the primary boundaries, which has a function different from the second boundaries that will be
used for the fuel debris retrieval.)©International Research Institute for Nuclear Decommissioning6.1.2 Development of the Boundary Maintenance Device and the Access Device No.22
for Operations(3) Study on the Method to Control Negative Pressures inside a Work Cell
Summary of specifications of the system for controlling negative pressures

Work cell ceiling door

Airlock cell ceiling door

Work cell

Airlock cell

Internal volume: 550 m3
Negative pressure value: -100 Pa

Function

Gravity damper(1)

Automatically adjust
negative pressuresinside the airlock cell(the “L” area)
Automatically adjust
negative pressuresinside the work cell (the“M” area)
Collect radioactive
powder dust containedin exhaust air (one of
the filters is a spare forreplacement)
Absorb and exhaust air
in/from the cell (one of
the blowers is a sparefor failure)
Monitor negative
pressures inside theairlock cell
Monitor negative
pressures inside thework cell
Monitor the clogging of
the HEPA filter
Monitor the integrity ofthe blower
Alert an abnormal
negative pressure
Monitor the exhaust
airflow

Internal volume: 400 m3
Gravity damper (2) Negative pressure value: -60 Pa

Cell partition shutter

Metallic mesh

SymbolGravity damper (1)Stainless steel spiral duct
Nominal diameter:
300 A

Gravity damper(2)

HEPA filters(1)(2)
ExhaustHEPA filter (1)Blowers (1)(2)
Blower (1)HEPA filter (2)ExhaustdPI (1)

Blower (2)dPI (2)

Summary diagram of the negative
pressure control system

dPIs (3)(4)
dPIs (5)(6)

A system required to create a negative
pressure environment inside the work cell wasstudied.

dPS
FI

Summary of
specifications
Set value-60 PaSet value-40 PaCollection efficiency: 0.3
μm or higher, 99.7%
Rated airflow: 70 m3/min

Airflow: 100 m3/min
Static pressure: 2.15 kPa

Set value: -60 Pa©International Research Institute for Nuclear Decommissioning6.1.2 Development of the Boundary Maintenance Device and the Access
Device for Operations

No.23(4) Work Cell Appearance
Opening
Carrying-in gate for
equipment

Work cell

Inlet

ExhaustoutletGravity damper

Tool box
Transport cart
Gate for workers

SuctionGuide pipe

RemainingissuesDamperBalanceweightExhaustInstall a “gravity damper” at an air inlet to control the gas flow at
the area.

Adjust the method for Connecting the equipment with the work cell area; optimize the layouts for thework cell and its surroundings; optimize the equipment structures for higher workability; and elaborate
the system for maintaining negative pressures inside a work cell.
©International Research Institute for Nuclear Decommissioning6.1.2 Development of the Boundary Maintenance Device and the Access Device No.24
for Operations(5) Changes to the Guide Pipe Seal Structure
Until FY2016, a packing structure was explored on the assumption that the
PCV would have a slightly-positive pressure environment and thefeasibility of its sealing at an element test was confirmed, but the structure
was changed to respond to the change to the negative pressure
environment inside the PCV.

Mine-shaped partIn a positive
pressure
environment
Guide pipe

Guide pipe

PCV headLip part

Cross-section of the resin packing
for a negative pressure
environment

Reverse the positionsof the lip and mineshaped parts

In a negative
pressure
environment
Guide pipe

Sealing part
Resin packing

Resin packing©International Research Institute for Nuclear Decommissioning6.1.2 Development of the Boundary Maintenance Device and the Access Device No.25
for Operations(6) Results of the Guide Pipe Sealing Test
The sealing performance was confirmed by using an actual-sized guide pipe (approx. 5 m long) against a condition where the sealing material(ethylen-propolindiene EPDM rubber) was irradiated (106 Gy).
A test was also conducted assuming the occurrence of displacement or inclination in order to figure out the required precision level for theguide pipe installation and the result was reflected in the equipment specifications. A test was conducted for the endpoint of not creating any
pressure change during a 10-minute holding period under ‐200 Pa(g).
During the 10-minute holding period under -200 Pa (g), the sealing for the use in a negative pressure environment experienced a pressurechange of up to -145 Pa(g), resulting in a small amount of leakage; however, since it will be an in-leak inside the PCV which will have anegative pressure environment, no leakage of radioactive materials will occur even when the sealing function is lost due to an earthquake,
etc. No influence on the sealing function from either the presence or absence of the irradiation was observed.
Guide pipe
installation device

Guide pipe

Seal
Mock-up PCV head

Sealing part

Remaining issue

Lower part

Upper part

Optimize the sealing structure so that it will have higher reliability for the use in a negative
pressure environment©International Research Institute for Nuclear Decommissioning6.1.3 Development of Opening Equipment inside the Reactor

No.26

 Outline of schedule
#

6.1.3

Items

Achievements up to FY2015•An element test was conducted toconfirm the feasibility of processing
Development ofwork for opening holes in reactor
technology for drillinginternals in the RPV, the key process
holes inside the reactor
to access the reactor core
(to the upper grid plate)•Conceptual study was conducted in
FY2015.

FY2016
Formulate and update theinvestigation plan
Conceptual design

Element test

FY2017

Basic design

Detailed design

Design the prototype
Test-manufacture the equipment
Test
Equipment composition

 Studies conducted in and until FY2016◼Tool head: severe structures and remove fragments from the top
to open holes

The conceptual study on equipment for opening holes in the reactor⚫ Studied the non-contact method(small processing reaction force), positioning and opening thenarrow parts of the reactor internals using the Abrasive Water Jet (AWJ) that is easy to reprocess (combination cutting).
⚫ Confirmed process-ability and workability of a small-sized AWJ nozzle by an element test andevaluate its feasibility.
⚫ Studied an access route with small risk of criticality (with less risk of the fall of fragments fromprocessing work) and the investigation plan.

◼Tool transfer system: insert the guide pipe into the lower part of
the RPV spare nozzle

 Items implemented in FY2017
Basic and detailed designs for equipment of opening holes in the reactor (including thework plan)⚫ Studied the dividing-up of the guide pipe and the down-sized insertion mechanism (joint/drum
methods).
⚫ Studied correction of the position deviations of the tool head AWJ nozzle (link method).
⚫ Studied a longer supply line of services (high-pressure water and abrasive) (drum relay).
⚫ Produced a prototype equipment and evaluated the remotely-operated cutting performance toverify remote operability by an element test (including simulation of actual layout.

◼Remote control/monitoring system, and service/power supply
system(Service andpower)•Long-distance
supply Drum relay

Work cell toolbox

PCV boundary
maintenanceguide pipe

(Tool transfer)• Guide pipe insertion Drum type

(Tool transfer)
Split guide pipe Joint type

(Tool head)
AWJ nozzle
 Link type

Concept about the core access©International Research Institute for Nuclear Decommissioning6.1.3 Development of Opening Equipment inside the Reactor

No.27(1) Study on Design of Opening Equipment inside the Reactor
Drum(Remotely replace thedrums for 0 and 45 
nozzles)
Guide pipe
(Store the high-pressure waterand abrasive hoses inside toprotect from a cutting surface)

Connecting unit

Accessequipment(i) Dividing the guide pipe
and the down-sized
insertion mechanism(joint/drum approaches)• Use an joint elastic guideto roll up to the drum andstore therein• Lift/Lower the joint in a
fixated state through a
toggle clamping motion
with the connecting unit

Main equipment specifications

Abrasive tank(Pressure-Supply
abrasive to the tool
head via the rotating
joint inside the drum)

Tool head(Install at the tip of theguide pipe to change
the nozzle angles andoperate the rotation)(iii) Make longer the supply
line of services (highpressure water andabrasive)(drum relay)• Relay long-distance hoses
and cables at the rotating
joint inside the drum (andstore them in the drum)• Use a regulator inside thetool head to relay theabrasive pressure-fed (0.3MPa) from the drum(ii) Correct the position deviationsof the tool head’s AWJ nozzle(link type)
Axis θ

• Rotate the nozzle atthe tool head

•The guide pipe was down-sized by rolling up with adrum.
•The tool head needs to be down-sized to take accountof its relation with the component (tool box) on theoperation floor.

• Change the angle
and correct theposition of the AWJ
nozzle at the linkmechanism

45 nozzle(L-shaped)(Access equipment)• Drum: height up to 4 m (to be stored in the tool box)
• Guide pipe
- Insertion length at 18 m; speed at 3.5 m/min (provisional)- Structure divided into 32 parts (600 mm  8 sections  4volumes at height 4 m)
- Outside diameter: φ140mm(Tool head)• AWJ nozzle (0/45 nozzle)- High-pressure water flow rate: 3.7 ℓ/min; pressure: 342
MPa- Abrasive garnet sand• Drive mechanism’s drive axes: α (angle), R (position), θ(rotation)• Regulator- Abrasive capacity: 1 kg
- Pressure Supply (receiving): 0.3 MPa (standard)- Abrasive supply volume: max. 500 g/min(Other equipment)• High-pressure water pump: flow rate at 3.7 ℓ/min; pressure
at 342 MPa• Air pressure: 0.2~0.3 MPa (standard)

Axis R[Remaining issue]
Down-size the tool head by dividing it up (at joints intoR
the parts with a length of 600 mm) to store it in the tool
Nozzle driving axes box (whose height is 4 m or lower provisionally)
Axis αWhen bent
When unlocked0 nozzle(Straight)©International Research Institute for Nuclear Decommissioning6.1.3 Development of Opening Equipment inside the Reactor

No.28(1) Study on Design of Opening Equipment inside the Reactor(i) Dividing the guide pipe and the down-sized insertion mechanism : 1) Drum structure• Elevate/Lower the tool head to the processing position and keep it at the position: insertion length at 18 m; speed at 3.5
m/min• Divide up the guide pipe at joints and stored due to height limit inside work cell: height of 4m(Store the extra part of the guide pipe in the drum as the guide pipe is lifted/lowered: 600 mm  8 sections  4 volumes=19.2m)• Extract and adjust the guide pipe’s center core to severe multiple nozzle angles in combination: target deviation within 5 mm
Evaluation item

Drum roll-up

Drum roll-up + jack lifting/lowering

Drum roll up + elevating/lowering roller

Roll up the guide pipe with drum

Lift/Lower the guide pipe with jack andstore it in drum

Lift/Lower the guide pipe with roller andstore it in drum

Anchoring
performance The guide pipe rattles and deviates

 (Jack) does not loosen (Roller pressing) does not easily
loosenPositioning Not anchored (rattles and deviates)nchored (Roller pressing) contact surface

Workability

 Not long time needed Long time needed Not long time needed

Connecting
structure©International Research Institute for Nuclear Decommissioning6.1.3 Development of Opening Equipment inside the Reactor

No.29(1) Study on Design of Opening Equipment inside the Reactor(i) Dividing the guide pipe and the down-sized insertion mechanism : 2) Guide pipe structure
Evaluation item

Nut anchoring
Stabilize stretch with locknut

Pipe

Self-weight retention
Retain stretch with self-weight

Sleeve anchoring
Stabilize stretch with sleeve

Toggle anchoring
Stabilize stretch with toggle clamp

Pipe

600 mmToggleSleeveConnecting
structure

Lock

Nut
Pipe
UnlockPlate

Anchoring
performance (Screw) does not easily loosen Weak against external force (Taper) loosens (Toggle) does not easily loosen

Positioning No rattling at the screw
fastening part

 Not anchored (Precision
required for the processing) Contact surface (Precision
required for the processing)Workability

 Nut’s rotation
 Long time required (for screw) No anchoring work required Sleeve’s up/down motion
 Not long time needed Contact surface (Precision
required for the processing) Lock mechanism easy to
open/close Not long time needed• Anchor with toggle clamp• Twist the joint by about 1.5 by rollingup the guide pipe with drum andaligning it to the skew (twisting) angle•Tilt the drum by about 2 to insert theguide pipe vertically85

LockedOpening
dimension
Approx. 85  55

Unlocked

Joint twisting

Drum tilting©International Research Institute for Nuclear Decommissioning6.1.3 Development of Opening Equipment inside the Reactor

No.30(1) Study on Design of Opening Equipment inside the Reactor(ii) Correcting the position deviations of the tool head’s AWJ nozzle mechanism: 1) Nozzle structure•To open holes in reactor internals and thereby allow the guide pipe to pass, the nozzle mechanism must have φ140 mm.
•The nozzle mechanism must be storable inside the guide pipe so narrow reactor internals can be cut with the mechanism, or more
specifically, so the cutting work can be conducted by using multiple nozzle angles in combination.
(If the work space allows, both simple-cutting and combination-cuttingapproaches will be employed to prevent the
Axis θ
falling of fragments.)

Axis R[1] [2] [3] [4][5] [6] [7][8]Axis αR

Conditions [1]~[4]:(0 nozzle head)(i) cutting at angles [1]~[4]Conditions [5]~[8]:(45 nozzle head)

Combined-cutting plan(ii) cutting at angles [5]~[8](iii) cutting for the first level complete

Tool head’s link structure(Repeat the same process
for the second level andthereafter)

Nozzle driving axes

• Change the nozzle angle by driving
the α axis
• Correct the nozzle position deviation in
the diameter direction by driving the R
axis©International Research Institute for Nuclear Decommissioning6.1.3 Development of Opening Equipment inside the Reactor

No.31(2) Assembly of the Prototype Inside-Reactor Opening Equipment(a) Drum and guide pipe(b) Drum and abrasive tank(d) Guide pipe’s skew guide(c) Tool head(e) Guide pipe’s toggle lock©International Research Institute for Nuclear Decommissioning6.1.3 Development of Opening Equipment inside the Reactor

No.32(3) Elemental Test(i) Verification test on the cutting conditions (Combination-cutting of a simulated steam dryer upright plate (6
tons)
[1]

Conditions[1]~[4][2] [3] [4][7][5] [6]

Conditions[5]~[8][8](a) After cutting(b) cutting plan

Conditions
cutting
speed(mm/min)[1]
3

0 nozzle

45 nozzle

Prototype inside-reactor
opening equipment

Platform for the mockspecimen(inside the test tank)(c) Combined-cutting

[2]
1.8

[3]
2

[4]
1.8

[5]
10

[6]
7

[7]
5

[8]

Notes

3

High-pressure water supply:
3.7 ℓ/minAbrasive consumption: 200
g/min• The remote operability of the combination-cuttingwith AWJ was confirmed; some parts were left uncut and required re-processing. (The nozzle’s
horizontal position deviation of 4 mm and vertical position deviation of 1 mm were taken into account; abrasive consumption at 200 g/min.)• It was confirmed whether the tool head position can be corrected. (The precision level will be sought to be improved through the anchoring of theguide pipe joints and by reviewing the adjustment structure.)[Remaining issues] Review the AWJ cutting conditions (combination angles, positions, etc.) and improve the equipment toward a higher precision level
for remotely-opened diameters and a less chance of re-processing. Stabilize the supply of services (abrasive up to 500 g/m).
©International Research Institute for Nuclear Decommissioning6.1.3 Development of Opening Equipment inside the Reactor

No.33(3) Elemental Test(ii) Verification test (using a mock specimen) on remote operability
Simple cutting(0 nozzle)

Target opening: φ100 (lower surface)
Target opening: φ120 (upper surface)

195
Simple cutting(0 nozzle)
Target opening:
φ200(a) Steam dryer (bottom plate)

Simple cutting(0 nozzle)(b) Steam separator(connecting rod)

i. cutting surface

ii. When opened

iii. Fragment from processing
work (upper surface)

iv. Fragment from processing
work (lower surface)

212

170
Combined-cutting(0/45 nozzle)

Combined-cutting(0/45 nozzle)

Target opening: φ160

Target opening: φ200(c) Steam separator (triple
cylinder center)(d) Steam dryer (corrugated plate)(e) Shroud head

•It was confirmed whether the cutting can be remotely conducted and a hole was made in a mock Unit layout setting, it was found that the
opening diameters varied and required re-processing.
 Need to improve the cutting precision, access accuracy and workability (by adjusting the nozzle positions and stabilizing abrasive).
• It was confirmed that fragments from the processing work of the shroud head can be collected and removed. (Fragments from the cutting
work fell on the shroud head or in the stand pipe).
©International Research Institute for Nuclear Decommissioning6.1.3 Development of Opening Equipment inside the Reactor

No.34[Remaining issues]◆

The design of the equipment structures, the making of element prototypes continues to be worked on, and element tests conducted, inorder to address the technical issues identified in the studies conducted in FY2017 (see below), and the Unit applicability of those
designs was confirmed.
The concretization and rationalization of the designs of the equipment and systems are sought and the preparation of component
specifications, assembly diagrams, systematic charts, etc., are being prepared.
Abrasive tank:◆[Issues]••••

The tool head needs to be made more compact because of the its relation with the component (tool box) on theoperation floor.
The remotely-conducted AWJ combination-cuttingresulted in some parts being left uncut and requiring re-processing.
The diameters of the remotely-worked openings varied in the mock Unit layout setting and needed to be re-processed.
 Improve the cutting precision, access accuracy and workability.
Some fragments other than those from the processing work of the shroud head fell into the stand pipe; need tocompromise the limit concerning the fall of fragments.

Items[Equipment structure
design]Implemented items
Down-size the tool head

Stably supply
abrasive to the tool
head

Drum: Store in
the tool box

Issues/Policy proposals• Divide up the tool head (at joints into the length of 600 mm each) so it becomes
more compact and can be stored in the tool box (which has the height of 4 m orless provisionally).

Reduce the guide pipe’s
vibration• Anchor the joints, review the adjustment structure and concretize the precision
improvement to reduce the tool head’s position deviations.

Improve the cutting precision,access accuracy and workability• Review the AWJ cutting conditions (combination angle, position, etc.) andsophisticate the equipment toward higher accuracy of the remotely-worked
opening diameters and less chance of re-processing.

Access equipment

Total
Guide pipe: Protect
length: 18 m the service hose anddetermine its position• Divide up so eachhas 600 mm (joint
type)• Remotely insert andpull out from 18 m
downward(lift/lower)• Stabilize the service supply (abrasive consumption: 200 → max. 500 g/min)[Element prototyping andtesting]

Study the methods forpreventing interferences inside
the reactor and how todetermine the opening positions• Rationalize the remote operations and monitoring based on the equipment design(positioning of processing work targets and openings).

Study the equipment in light ofassumed reactor conditions• Formulate the processing work and investigation flows (including the layout of theprocessing work targets, opening positions and opening diameters) andrationalize the investigation method and equipment to respond to thecompromised limit concerning the fall of fragments from processing work into thereactor.

Confirm the workability of theequipment and systems at theUnit(s).

• Make a prototype combining the tool head and the access equipment and conduct
a partial mockup test to confirm the remote operations, monitoring and service
management.

Total
length: 2 m

Tool head
AWJ nozzle: Improve
the angling andpositioning accuracy
and stabilize the highpressure water andabrasive amounts.

©International Research Institute for Nuclear Decommissioning6.2 Development of Equipment to Access the Reactor Core from the Side

No.35

 Outline of schedule
#

Items

Development of theequipment to access2.4
from the side

Achievements up to FY2015

FY2016
Study the applicability-

FY2017
Evaluate the applicability
Determine the method feasibility
Conceptual design
Design equipment

 Implementation items(Second half of FY2016)➢It was decided to additionally seek a method to access from the side(the side-opening investigation method) and the development plan
was drawn-up and a study launched.
(First half of FY2017)➢The applicability of the method was evaluated in early FY2017.
➢The applicability to the Units was examined and it was concluded thatthe priority should go to Unit 2.
➢Working on the conceptual design was started and the concept of theinvestigation method concretized with particular focus on securing theboundaries.
➢An exposure assessment was conducted concerning the construction
work for the investigation, it was confirmed that the investigation isapplicable under the current PCV condition (nitrogen substitution)even when an exposure increase occurs due to the dispersion ofradioactive dust.

East side of
R/B

Work cell(Negative
pressure area)
Tool box(AC0, Acx)

Tool
System to prevent
contamination
spreadAir conditioning
room(Second half of FY2017)➢Specifications of equipment was summarized based on theconceptual design.

©International Research Institute for Nuclear Decommissioning6.2 Development of the Equipment to Access the Reactor Core from the Side

No.36

(1) Results of the Study on the Equipment Concepts◼

A tool box (Acx) stored necessary tools (for drilling, inserting guide-tube andinstalling seal) is fixed in the tool box space on the east side wall of the reactor
building (R/B). The tool box is connected one to another for the side-opening
investigation.

The work cell has an openable ceiling, which will be
opened/closed for the replacement of tool boxes.
Work cell◼

A work cell is installed (in a negative pressure environment) to cover the tool box.
The layout should be considered for dust leakage from the tool box.

◼

Pre-preparation and post-treatment for the tool box is conducted at the“maintenance unit” installed on the ground level.
Work cell

Maintenance unit (floor plan)
Materials andwastesCarrying
in/out SAS

Material storage
Internal storage
area
External storage
area

Tool box
WorkerWorkergate SAS gate SAS

Workergate SAS

Workergate SAS

Tool box example (side view)©International Research Institute for Nuclear Decommissioning6.2 Development of the Equipment to Access the Reactor Core from the Side

No.37

(2) Boundary Formation◼

Use mechanical seals and compressed seals in combination to make a boundary.

◼

Install a work cell (with a negative pressure environment) in such a way as to wrap the tool box (AC0 and/or ACx) as apreventive measure.
Compressed seal
Chemical resin

Work cell (with a negative
pressure environment)

Tool box AC0

Lighting-guidetube

PCV sleeve
PCV guide tube
RPV guide tube

Compressed seal
RPV

Tool box ACx

Biological shield
PCV shield
wall

PCV

Example of Mechanicalsealing

R/B exterior wall

Mechanical seal
PCV shieldwall

Guide tube

Montagetube

EPDM

Example of Compressed sealing
Issue: sealing performance with the surface of cylinder
structures
Needs to conduct an element test to confirm the sealing
performance.

PCV sleeve
Inject chemicalresin

PCV sleeve when installed

Withdraw the The resin passes
montage tube through the sleeve’s
bottom plate

Issue: joint strength at the cutting surface of chemical resin concrete.

Needs to conduct an element test to confirm the joint strength.
©International Research Institute for Nuclear Decommissioning6.2 Development of the Equipment to Access the Reactor Core from the Side

No.38

(3) Drilling of investigation Holes◼

Use a hybrid head with a water jet (WJ; used to drill concrete) and abrasive water jet (AWJ; used to drill rebars and steel plates)
to open the holes.

Tool head

AWJ nozzle

Tool box

WJ nozzle

Eccentric rotation
moduleEccentric rotation
moduleAWJ/WJ head frame

Cable and hose

AWJ nozzle
CameraCameraSuctionnozzleSuctionnozzleAWJ/WJ head frame

Tool head (side view)

Tool head (plan view)
Issue: whether capable of cutting the reinforced concrete used for the reactors inFukushima?
Needs to conduct an element test to confirm the cutting capability (against a coarse
surface).

Issue: how to collect and drain treated water (and fragments from cutting work)
Needs to conduct an element test to confirm the waste treatment performance(and the collection and separation of fragments from cutting work).

©International Research Institute for Nuclear Decommissioning6.2 Development of the Equipment to Access the Reactor Core from the Side

No.39

(4) Concepts of the Boundary Maintenance(Preventing Dust Diffusion)◼

Prevent contaminated dust from diffusing after the PCV opening by Supplying air or nitrogen gas into the tool box (AC0 or
ACx) and thereby keeping the pressure inside the tool box (AC0 or ACx) higher than the pressure inside the PCV.

Supply air or nitrogen gas
Tool box ACx

Tool box AC0
Absorb air or nitrogen gas

Tool box
AC0

Supply air or nitrogen gas
Absorb air or nitrogen gas

When the AC0 tool box is connected Acx.
When the AC0 tool box is alone.

➢

Establish a negative pressure area
outside the tool box (AC0 and/or ACx)
which has a slightly-positive pressure, asa measure against contamination spread.

Parea
Patm

PPCV
Pcell

PPCV < Pcell > Parea < Patm

Slightly-positive
pressure by Supplying
nitrogen gas or air©International Research Institute for Nuclear Decommissioning6.3 Development/Selection of the Investigation Method for the Reactor Core

No.40

 Outline of schedule
Items

Achievements up to FY2015

FY2016FY2017

Formulate and update theinvestigation plan

6.3

Conceptual design (Comparison andevaluation of multiple methods)

Development/Selecti
on of the method toinvestigate the partto the reactor core-

Element test

Verify the viability at an exposure assessment

Design the concept of the investigation equipment that makes
use of the existing space inside the reactor
Basic design (System configuration, etc.)
Detailed design
Design the prototype Test-manufacture
the equipment

 Items implemented in FY2016• The concepts of the investigation equipment and the access equipment were designed.
Based on the results of an element test, it was decided to use either an imaging tube or
CID camera as part of the investigation equipment.
 Items implemented in FY2017<Equipment design>• Based on the summary composition of the investigation equipment studied in FY2016, it
was decided to employ the following investigation equipment.
A: Equipment for Prior Confirmation that will be injected through small-diameter
openings
B: Equipment for the Full-Scale Investigation that will be injected through largediameter openings
C: Equipment that moves horizontally inside the shroud head toward the center of the
RPV to investigate the deepest part of the RPV• A study on whether/how to bundle investigation instruments, i.e., a camera, lighting,dosimeter and thermometer was also conducted.
A study on the cable
composition was also conducted.

Investigationequipment A
Steam
separator

Test<Test-manufacturing and testing the equipment>•The following at an element test was conducted:✓ Verification test on the access-ability of the investigation equipment
 The test was conducted using test mock-ups and each equipment’s remote
operability was confirmed.
✓ Verification test on the visibility of fiber scopes and industrial-use endoscopes
 It was confirmed that the equipment A met the visibility required for Prior
Confirmation.
✓ Test on the viability of the prototype of the horizontal-motion mechanism
 The viability was confirmed in the assumed real-life environment.
✓ Test on the radiation resistance of the thermometer It was confirmed that it can be used in the assumed real-life environment.
 Remaining issues• Improve the operability and visibility (image processing) of the investigation equipment• Conduct another element test and a study to address the issues identified in the elementtest• Estimate the inside-reactor conditions from the findings of the investigation at the Units
and use the estimate for the development of the fuel debris retrieval equipment• Reflect the progress of the inside-reactor investigation equipment design in the design of
the access equipment for the side-opening investigation

Passage inside the steam separator©International Research Institute for Nuclear Decommissioning6.3 Development/Selection of the Investigation Method for the Reactor Core

No.41

(1) Investigation Equipment A for Prior Confirmation: Investigation Specifications and Requirement Specification of Equipment
Required specifications for investigation equipment A

Investigation route(Spare nozzle’s central axis)
Environmental
conditions:•Humidity: 100%
•Fog/mist•Darkness•Dose rate:

Investigation flow & location

Limit of size

Preliminary investigation
inside the well cover

Diameter of the wellcover opening: φ40 mm

Preliminary investigation
inside the PCV head

Diameter of the PCV
head opening: φ40 mm

Preliminary investigation
inside the RPV head

Diameter of the sparenozzle opening: φ40mm

Preliminary investigation of
the steam separator

Diameter of the steam
dryer bottom plate
opening: φ40 mm

Preliminary investigationof the outside of thesteam separator and theupper part of the shroud
headMin. gap outside steam
separator: 67 mm; gap
between supporting rods:
37 mm

16 Sv/h800 Sv/h
Passing outside
Passing inside

Approx. 100 mm

5,000 Sv/h

Preliminary investigation of
the inside of the steam
separator
After passing
through the steam
separator
Preliminary investigation of thereactor core (Upper grid plate)Preliminary investigation of thereactor core (Core support
plate)
Investigation of the bottom partof the RPV

Vanes inside the steam
separator: screw-shapedwith a gap of approx. 79~21mm between them

Investigation Equipment (AS)External diameter: φ30 mm or less
Dose: up to 5,000 Sv/hinvestigation items:• Visual information: foreign objects of φ50 mm orlarger• Dose: precision level necessary for orders to beprocessed• Temperature: accuracy of ±2oC
investigation route: on the central axis of the sparenozzle(for the part down to the upper part of the shroud
head)
Max. descent distance: 16.2 m
Other: protection against water drops, fall prevention, andsecuring of collection capability at the time of failure

Investigation equipment (AB)External diameter: φ20 mm or less; Length: 100 mm or
less
Dose: up to 5,000 Sv/hinvestigation items:• Visual information(*1): foreign objects of φ50 mm
or larger
investigation route: From the spare nozzle’s central axis
(up to the steam dryer) to the inside of the steam
separator (down to the bottom part of the RPV)(*2)
Max. descent distance: 26.9 m
Other: protection against water drops, fall prevention,and securing of collection capability at the time of failure(*1) Priority is given to the easiness-to-pass of the steam separator vanes through narrow areas
for the purpose of obtaining information about the reactor core before processing the shroud
head. Neither thermometer nor dosimeter is installed on the equipment AB because the data
can be collected with the investigation equipment AS or can be measured, after theprocessing work, with the investigation equipment B.
(*2) Through a remote operation, curvature of the off-set amount (approx. 100 mm) is given to theinvestigation equipment so it can enter the steam separator through the hole that will be
opened at the steam dryer bottom plate.

©International Research Institute for Nuclear Decommissioning6.3 Development/Selection of the Investigation Method for the Reactor Core

No.42

(2) Investigation Equipment B (for the Full-Scale Investigation): Investigation Specifications and Requirement Specification of Equipment
investigation route(Spare nozzle’s central
axis)
Environmental
conditions:•Humidity: 100%
•Fog/mist•Darkness•Dose rate:
16 Sv/h800 Sv/h

Investigation flow &location
Investigation of the insideof the well cover

Limit of size
Diameter of the wellcover opening: φ700mm

Investigation of the insideof the PCV head

Diameter of PCV
head opening: φ500
mm

Preliminary investigation
inside the RPV heatretention material

Diameter of the RPV
heat-retention
material opening:
φ680 mm

Investigation inside the RPV
head
Diameter of the steam
separator opening: φ140 mm

Diameter of the RPV
opening: φ300 mm(Remove the sparenozzle)Steam separator(After processing)

Diameter of thesteam separator
opening: φ140 mm

Required specifications forinvestigation Equipment B
Investigation Equipment B
External diameter: φ100 mm or less
Dose: up to 5,000 Sv/hinvestigation items:• Visual information: fuel rod of φ10 mm• Dose: precision level necessary fororders to be processed• Temperature: accuracy of ±2oC
investigation route: On the spare nozzle’s
central axis (the part down to the bottom part of
the RPV)
Max. descent distance: 26.9 m
Other: protection against water drops, fall
prevention, and securing of collection capability
at the time of failure

Upper grid plate
After passing theupper grid plate

5,000 Sv/h

Diameter of the
shroud head opening:φ110 mm

Investigation inside thereactor coreCore support plate
Investigation of the bottom
part of the RPV(Straight descending route)©International Research Institute for Nuclear Decommissioning6.3 Development/Selection of the Investigation Method for the Reactor Core

No.43

(3) Investigation Equipment C (Which Moves Horizontally): Investigation Specifications and Requirement Specification of Equipment
Investigation route(Spare nozzle’s central axis)
Environmental
conditions:•Humidity: 100%
•Fog/mist•Darkness•Dose rate:
16 Sv/hWork flow & interfering
objects
Well cover ~ steam
dryer(After processing)
Steam separator(After processing)800 Sv/h

Shroud head
(After processing)

Limit of size
Diameter of thesteam separator
opening: φ140 mm

Investigation Equipment C
Diameter of the
opening in the shroud
head: φ110 mmHorizontal-motion zone

Upper grid plate
investigation inside thereactor core(near the reactor’s central
axis)
5,000 Sv/hRequired specifications forinvestigation Equipment C

Distance between the
shroud head opening
and the upper surfaceof the tie plate: 1,180mm

Upper grid plate 300 mm

External diameter: φ100 mm or less
Dose: up to 5,000 Sv/hinvestigation items:•Visual information: fuel rod of φ10 mm•Dose: precision level necessary for orders to beprocessed•Temperature: accuracy of 2oC
investigation route:on the spare nozzle’s central axis (to the shroudhead) and on the reactor’s central axis (from theupper grid plate to the bottom part of the RPV) (*1)
Max. descent distance: 26.9 m
Protection against water drops, fall prevention, andsecuring of collection capability at the time of failure

After passing theupper grid plateCore support plate

Investigation of the bottom
part of the RPV(*1) The horizontal-motion amount below the shroud: approx. 1,220 mm, which is the
distance between the spare nozzle’s central axis and the reactor’s central axis;
and the height of the space available for offset adjustment: the distance between
below the shroud head opening and the upper end of the fuel assembly’s fuelplate (both according to our study conducted in FY2016).
©International Research Institute for Nuclear Decommissioning6.3 Development/Selection of the Investigation Method for the Reactor Core(4) Study Results
Type

A

B

Suspension lowering + X-Y position
adjustment mechanism (+ middle
inflection mechanism)

Low dose area
Industrial-use endoscope(~ 102 Gy)

Suspension lowering + X-Y position
adjustment mechanism (+ middle
inflection mechanism)

High radiationarea(103 Gy ~)Suspension + X-Y position adjustment
mechanism

Connecting drum + horizontal-motion
mechanism
Investigation Equipment A

Investigationequipment

C

Fiber scope

Access equipment

Investigation Equipment (for visual
information collection)

Access equipment

Fiber scope + movable tip
mechanism

No.44
Diameter of theequipment

Overview

Equipment injected through small-diameter openings for Prior Confirmation.
φ30 mm or φ20
They are equipped with a dosimeter and thermometer. The one used for themminvestigation of the inside of the steam separator will also be equipped with a middle
inflection mechanism so that it can access narrow areas.

Camera (CCD) + pan tilt
Low dose area
mechanism2(~ 10 Gy)
High radiationarea(103 Gy ~)High radiationarea(103 Gy ~)Industrial-use endoscope(for the investigation of theinside the PCV)

Suspension lowering
Access method employed for the investigation equipment
A

Equipment injected through large-diameter openings for Full-Scale
Investigation. They are equipped with a dosimeter and thermometer. The
Camera (CID and imaging straight-descending one will have a camera with a pan tilt or powered mirror
so that it will fully cover the investigation area.

φ100 mmtube) + pan tilt mechanism

Camera (CID and imaging Equipment injected through large-diameter openings for the Full-Scale
Investigation. They will be equipped with a dosimeter and thermometer andtube) + pan tilt mechanism have a horizontal-motion mechanism for an access to the center of theφ100 mm
Investigation
Equipment
B
Investigation
EquipmentCreactor.

CCD(for the investigationof the inside of the
PCV A2)CID (in colors)

Imaging tube
(in black and white)

Imaging tube
(in black and white)

Connecting drum

Suspension lowering
Access method employed for the investigation equipment B

Horizontal-motion
mechanism

Access method employed for the investigationequipment C©International Research Institute for Nuclear Decommissioning6.4 Designing the Entire Investigation Equipment System and Planning the investigation

No.45

 Outline of schedule
Items

Achievements up to FY2015

FY2016FY2017

Formulate and update the investigation plan
Studied safety requirements

Studied safety requirements

6.4

Designing the entire
investigation equipment
system and planning theinvestigation

Verify the viability at an exposure assessment

Study the investigation procedures and work flows

Study the investigation procedures and work flows
Generate work flowcharts

 Items implemented in FY2016•In order to develop safe and secure investigation methods and access routes despite having
no information about the state of the reactor well inside, structures, reactor core or dose rates,
the access operation flow was broken down and a study conducted on the implementationplan.
 Items implemented in FY2017•A study on the investigation procedures and work flows was conducted.
•Safety requirements were organized, which would need to be discussed with the regulatory
authority.
•The specifications required for each equipment were put together and investigation
flowcharts and layout drawings were generated.
 Remaining issues•Rationalize the work and investigation flows; assess the impact of fragments from theprocessing work of structures; and conduct an exposure assessment.
•Estimate the conditions inside the reactor and environmental conditions from other project
findings.
•Organize the relations between safety and function requirements and reflect the findings in
the designs of the equipment.
•Clarify when to introduce the supplementary systems necessary to conduct investigation(e.g., gas control, nitrogen supply, negative pressure control, dust monitoring, criticality
control system) and what specifications those systems should have, and conduct a study on
the applicability of those systems (and the systems that are being studied in other projects).
•Conduct a study on the operation guidelines for the real-time dust monitoring system.
•Establish a utility supply system for each tool.

<Required Safety Requirements>
Safety requirements

Assumed events

Prevent radioactive materials
from leaking to the gas phase

Migration of radioactive materials to the gas
phase during an operation

Prevent radioactive materials
from leaking to the liquid phase

Migration of radioactive materials to theliquid phase during an operation

Maintain the fuel debris cooling
function

Loss of the fuel debris cooling function

Control criticality and maintain
sub-criticality.

Occurrence of criticality resulting from achange in a fuel debris shape due to the fallof a fragment from processing work

Prevent fire or explosion

Hydrogen explosion during a processing
work

Prevent the fall of a heavy
weight object

Dispersion and diffusion of radioactive
materials resulting from the fall of a heavy
weight object

Prevent the collapse of the R/Bduring the construction work forthe investigation

Collapse of the R/B due to the installation ofequipment©International Research Institute for Nuclear Decommissioning6.4 Design of Whole Investigation Equipment System and Plan of the Investigation Method No.46(1) Study on the Processing and (Top-Opening) Investigation Flows
The processing and investigation flow steps are as below. Prior to the opening of large-diameter holes, small-diameterholes are planned to be opened for preliminary confirmation to determine the next step for investigation.
No.

Flow steps

Processing work/Applicable
investigation equipment
Make small-diameter holes (φ40 mm)

Notes

1

Process the well coverUse a core boring for the processing work. Fragments from the processing work will fall.

2

Preliminarily investigate the inside of the well cover Investigation Equipment A

3

Process the well cover

Make large-diameter holes (φ700 mm)

Use a core boring for the processing work. Fragments from the processing work are collectable.

4

Investigate the inside of the well cover

Investigation Equipment B

Investigate the inside of the reactor well. Confirm the conditions of the structures.

5

Process the PCV head

Make small-diameter holes (φ40 mm)

Open by machining as a measure against hydrogen explosion. Fragments from the work will fall.

6

Preliminarily investigate the inside of the PCV head Investigation Equipment A

7

Process the PCV head

Make large-diameter holes (φ500 mm)

Use AWJ to conduct the processing work. Fragments from the processing work are collectable.

8

Investigate the inside of the PCV head

Investigation Equipment B

Investigate the space between PCV and RPV heat-retention material. Confirm the conditions of the structures.

9

Process the RPV heat-retention material

Make large-diameter holes (φ680 mm)

Use AWJ for the processing work. Fragments from the processing work will fall.

10

Preliminarily investigate the inside of the RPV
heat-retention material

Investigation Equipment B

Prior-investigate the RPV head spare nozzle. Determine whether it’s possible to conduct the processing work.

11

Process the RPV head (spare nozzle)

Make small-diameter holes (φ40 mm)

Open by machining the center of the spare nozzle closing flange as a measure against hydrogen explosion. Fragments from the processing work will fall.

12

Preliminarily investigate the inside of the RPV head Investigation Equipment A

13

Process the RPV head (spare nozzle)

Make large-diameter holes (φ300 mm)

Use AWJ to conduct the processing work. Remove the spare nozzle. Fragments from the processing work are collectable.

14

Investigate the inside of the RPV head

Investigation Equipment B

Investigate the inside of the RPV head. Confirm the conditions of the structures and the state of the space.

15

Process the steam dryer bottom plate

Make small-diameter holes (φ40 mm)

Use AWJ to conduct the processing work. Perform the processing for corrugated plates, etc. at a safer location. Fragments from the processing work will fall.

16

Preliminarily investigate the steam separator

Investigation Equipment A

Prior-investigate the conditions of the upper part of the steam separator; confirm only its immediate underneath. Determine whether it’s possible to conduct the processing
work.

17

Process the steam dryer bottom plate

Make large-diameter holes (φ140 mm)

Use AWJ for the processing work. Fragments from the processing work will fall.

18

Preliminarily investigate the outside of the steam
separator

Investigation Equipment A

The equipment will pass through the outside of the steam separator to prior-investigate the conditions of the part down to the shroud head. Determine whether it’s
possible to conduct the processing work.

19

Preliminarily investigate the inside of the steam
separator

Investigation Equipment A

The equipment will pass through the inside of the steam separator. Investigate the part down to the reactor core if the equipment can pass through the vane part.
Determine whether it’s possible to conduct the processing work.

20

Process the steam separator

Make large-diameter holes (φ140 mm)

Use AWJ for the processing work. Fragments from the processing work will fall.

21

Process the shroud head

Make large-diameter holes (φ110 mm)

Use AWJ to conduct the processing work. Fragments from the processing work are collectable.

22

investigation inside the reactor core

Investigation Equipment B

The equipment will make a straight descent to the point it can reach to investigate the parts from the upper grid plate to the reactor core and also (if reachable) to the RPV
bottom part.

23

Investigate the inside of the reactor core
(horizontal-motion)

Investigation Equipment C

The equipment will horizontally move in the shroud head toward the center of the reactor and then go down to and investigate the deepest bottom (possible to access).

Prior-confirm the PCV head; confirm only its immediate underneath. Determine whether it’s possible to install and process the guide pipe.

Confirm the upper part of the RPV heat-retention material; confirm only its immediate underneath. Determine whether it’s possible to conduct the processing work.

Prior-confirm the conditions of the dryer; confirm only the immediate underneath of the dryer. Determine whether it’s possible to conduct the processing work.

©International Research Institute for Nuclear Decommissioning6.4 Designing the Entire Investigation Equipment System and Planning the investigation(2) (Draft) Integral PlanningWork site

Unit 1

Operation floor

Unit 2

Operation floor

Rooftop of the air
conditioning room

Negative pressure
environment inside
the PCV

Planned work flow (The time needed for each item is not considered.)

Prepare for the SFP fuel retrieval (Remove theupper part of the building and the well cover, installshields, etc.)

Rooftop of the air
conditioning room

Negative pressure
environment inside
the PCV

Start the SFP fuelretrieval(hopefully in
FY2023)Top-opening
investigation

Removethe upper
part ofthebuilding

Prepare for the SFP fuel retrieval(Install shields, etc.)

 Common among the Units•Perform on-site pre-surveys•Priority of works•Duration of work for each item
•Timing for creating a negative pressure environment

Side-opening
investigation

Removeinterfering objects
and install work
platforms

Side-opening
investigation

Start the SFP
fuel retrieval(hopefully in
FY2023)Top-opening
investigation

Retrieve fueldebris from the
RPV (top entry)

Start the SFP
fuel retrieval(around mid
FY2018)Remodel the shields and build a work
area

Remove interfering objects and installwork platforms

 Unit 1•Plan the SFP fuel debris retrieval and coordinate post-investigation
works on the operation floor toward fuel debris retrieval
 How to establish the work area after removing the well-cover?
 How to reflect investigation findings about the SFP fuel retrieval work
area into the facilities?
 Unit 2
・Determine when to remove the interfering objects on the rooftop of the
air conditioning room
・Plan the SFP fuel debris retrieval and coordinate post-investigation
works on the operation floor toward fuel debris retrieval
 How to reflect investigation findings about the SFP fuel retrieval work
area into the facilities?

Establish a negative pressure environment inside the PCV

Removethecoveringbuilding
and gantry

Issues/Matters that need to be studied or considered

Retrieve fueldebris from the
RPV (top entry)

Establish a negative pressure environment inside the PCV

Operation floor

Unit 3<Prerequisites>・The side-opening investigation will be conducted only when it can be carried out prior to the top-opening investigation• Schedule of the major flow steps should not be planned at the same timing.
• The top-opening investigation will be set after removing fuels from the SFP and building a negative pressure environment

Rooftop of the air
conditioning room

Negative pressure
environment inside
the PCV

No.47

Top-opening
investigation

Side-opening
investigation

Retrieve fueldebris from the
RPV (top entry)

 Unit 3•Plan the SFP fuel debris retrieval and coordinate post-investigation
works on the operation floor toward fuel debris retrieval
 Find out how much the well cover is damaged and judge whether it’s
possible to process it
 How to reflect investigation findings about the work area into theremodeling of the shield toward fuel debris retrieval

Establish a negative pressure environment inside the PCV The Top-Opening Investigation will probably start with a delay. The flow of the “Connecting” work needs to be rationalized more (conducted at theoperation floor) while taking account of the pre- and post-investigation plans (per Unit) and the entire operation flow up until the fuel debris retrieval.
©International Research Institute for Nuclear Decommissioning7. Summary

No.48

7.1 Development of equipment to access the reactor core from the top⚫
⚫

An exposure assessment was conducted and the policy to perform the investigation in a negative pressure environment adopted.
A verification test on the boundary maintenance equipment’s sealing in a setting that simulated a negative pressure environment for the inside of
the PCV was conducted.
⚫
Equipment for removing the RPV spare nozzle was prototyped and an element test conducted.
⚫
Equipment for making holes at narrow reactor internals (combination-cutting of the steam separator, etc.) was prototyped and an element test
was conducted.
 For the method to establish an access route by opening the upper part of the RPV, studies were conducted on the plans/specifications of
the equipment (and systems); its prototype was made and an element test conducted; its design elaborated; and its remote operability
confirmed.

7.2 Development of equipment to access the reactor core from the side
A study on the equipment’s applicability to each Unit was conducted and the data showing the validity of applying it to Unit 2 earlier than the otherunits was put together.
⚫
An exposure assessment was conducted and it was confirmed whether the method would cause no problems even when radioactive dust
disperses.
⚫
The concept was studied and a method for securing a boundary established .
⇒ A method for cutting the PCV shield wall , PCV and RPV without compromising a boundary was established; the work flow was clarified;
the specifications compiled; and the application feasibility to the Units confirmed.
⚫

7.3 Development/Selection of the method to investigate down to the reactor core⚫

Studies were conducted, per each investigation flow, on the specifications of the two types of equipment: the one to preliminarily confirm theaccess route after making small-diameter holes; and the other to perform the Full-Scale Investigation after making large-diameter holes.
⚫
A study on the specifications of the investigation equipment which has a horizontal-motion mechanism was conducted.
⚫
A verification test on the access capability was conducted and the remote operability confirmed.
 The equipment was prototyped and a verification test conducted, by using mockup openings, on the equipment’s access capability and its
remote operability confirmed.

7.4 Designing the entire investigation system and planning the investigation⚫
A study on the processing/investigation flows was conducted and the entire investigation flow organized.
⚫
A study on the action policy for each Unit that responds and corresponds to the pre- and post-investigation state and plan was conducted.
 The entire work flow was generated from the equipment installation on the R/B operation floor through to the on-site surveys and to thepost-investigation treatment.
 A study on the necessity of conducting the following pre-investigation on-site surveys aimed at heightening the equipment system’s andplan’s applicability to the real-life situations was conducted.
•Survey on the inside of the reactor well (for the top-opening investigation)•Survey at the third floor of the Unit 2’s R/B (for the side-opening investigation)©International Research Institute for Nuclear Decommissioning