Subsidy Project of Decommissioning and Contaminated Water
Management in the FY 2021

Development of Technology for Detailed
Investigation inside PCV
FY2021 Accomplishment ReportAugust 2022
International Research Institute for Nuclear Decommissioning(IRID)©International Research Institute for Nuclear Decommissioning

No.1

Table of Contents
1. Research Background and Purpose
2. Project Goals
3. Implementation Items and Relation with Other Projects

4. Schedule
5. Project Organization Chart
6. Implementation Details
6.1 Planning and update of investigation and development for detailed investigation inside the pedestal
6.2 Development of the access and investigation equipment and investigation technology for detailed investigation
inside the pedestal
6.3 Mock-up test plan
6.4 Issues
6.5 Level of the goal achievement
6.6 Future plans©International Research Institute for Nuclear Decommissioning

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No.2

1. Research Background and Purpose[Purpose of this project]
The purpose of this project is to develop an access and investigation equipment and investigation technology for obtaining information on theupper section of the pedestal from the CRD opening to the area in the vicinity of the inner center of the pedestal, which is important in studying
the details of the status inside the pedestal, especially, the viability of the bottom access investigation method for investigating the inside of theReactor Pressure Vessel (hereinafter “RPV”), based on the results of previous projects; and to implement the following.
(1) Planning and update of investigation and development for detailed investigation inside the pedestal(2) Development of the access and investigation equipment and investigation technology for detailed investigation inside the pedestal[Reflections of this project]
The information obtained from this project (status of structures inside the pedestal, status of fuel debris distribution, dose rate) will be reflectedin the detailed study of the bottom access method and equipment for investigation inside RPV which is part of a different project. And, it will bereflected in the detailed study of fuel debris retrieval method and equipment as well.
Inside the pedestal
CRD opening
Investigation inside the pedestal
・Distribution of fuel debris and deposits inside the pedestal(gas phase)・Status outside the pedestal (in the vicinity of CRD opening)・Status of CRD system (damage, presence of opening)・Dose rate distribution
・3D information of the inside of the pedestal (point clouddata)

Reflection into detailed
design of retrieval method
and equipment

Reflection into detailed design ofinvestigation method and equipment

X-2 penetration
B1 investigationequipment(stack)Assumed travelingroute of the access andinvestigation equipment

Figure 1: Estimated traveling route of the accessand investigation equipment inside PCV

B1 investigation equipment:
Stack during investigation in
April 2015

Fuel Debris Retrieval

Figure 2: Assumed data to be acquired©International Research Institute for Nuclear Decommissioning

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No.3

2. Project Goals(1) Planning and update of investigation and development for detailed investigation inside the pedestal

This project aims to create a plan for developing the access and investigation equipment with additional
necessary functions, and a plan for detailed investigation using the developed equipment, in reference to theplans for developing the access and investigation equipment and for the investigation equipment, which weredeveloped in the previous project.
Furthermore, these plans are continuously revised and updated as required while taking into consideration thelatest site information, results of internal investigation, etc.

(2) Development of the access and investigation equipment and investigation technology for detailed investigation
inside the pedestal
This project also aims to design and manufacture the access and investigation equipment, in reference to thestudies in the previous project, and to carry out in-plant verification (unit test) of the equipment, as well as theinvestigation technology for verifying applicability in internal investigation, based on the plan for developing theaccess and investigation equipment described in (1) above.

Furthermore, mock-up tests that are simulated actual equipment are conducted to verify the site applicability.

©International Research Institute for Nuclear Decommissioning

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No.4

2. Project Goals
This project aims to plan investigation and development related to detailed investigation

inside the pedestal as well as to develop the access and investigation equipment, based on technologies
Developed in the previous project (completed until FY2020).

TRL: Technology Readiness Level
Table 1: Goals pertaining to the investigation inside the pedestal

TRL 1
Basic
research

TRL 2
Appliedresearch

TRL 4Research
forpractical
use

TRL 3
Appliedresearch

TRL 5
Simulateddemonstration[Development and verification of element technologies]

Technology developed in the previous project(Completed until FY2020)

The Project (FY2021 to FY2022)

Items
(1)

Planning and update of investigation and development
for detailed investigation inside the pedestal(2) Development of the access and investigation equipment
and investigation technology for detailed investigation inside
the pedestal

TRL 6
Field test

TRL 7
Practical
use[Mock-up verification]

Engineering company(Or developed as part of other subsidized projects)

Goal of this project

TRL

・Planning of the pedestal investigation
・Overall plan pertaining to the investigation equipment,
equipment and machines
・Development of investigation equipment and investigation
technology
・On-site demonstration (plan for onsite-investigation)

3 to 43 to 43 to 43 to 4・Detailed designing and manufacturing of the investigationequipment and investigation technology
・In-plant verification (unit test)
・Mock-up tests (testing facility, tests)

3 to 43 to 4
5©International Research Institute for Nuclear Decommissioning

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No.5

3. Implementation Items and Relation with Other Projects

The scope of investigation (conceptual image) of this project (Investigation Inside the Pedestal) and related projects isshown in the figure below. The inside of the pedestal, which is outside the scope of the Development of Detailed
Investigation Inside Pedestal (Deposits) Project, is the main scope of investigation of this project.
It is assumed that the projects will be carried out in the order of Development of Technology for Detailed Investigation
Inside PCV project ⇒ This Project ⇒ Development of Technology for Investigation Inside RPV project, and the results ofeach step will serve as Input for the following step.
Table 2 : Scope of investigation of each project (for Unit 1)
Investigation Inside RPV
project

Project nameScope of investigation

Development of
Inside RPVTechnology for(Mainly inside the shroud)
Investigation Inside RPV[Other subsidized project]

Input
Investigation Inside
Pedestal project

Input
Detailed Investigation
Inside PCV (fordeposits) project

Method ofinvestigation
Investigation bymeans of a drone
is being considered

Development ofTechnology for
Investigation Inside
Pedestal[This project]

Inside the pedestal(Mainly the air part, and theStudied as part ofunderwater area only to the extent
this projectthat is visible from the air part)Development ofTechnology for Detailed
Investigation Inside PCV(Deposits)[In-house project]

Inside the pedestal(Mainly the underwater area, andthe air part only to the extent thatis visible from the underwater
area)

ROV

Figure 3: Relation with other projects©International Research Institute for Nuclear Decommissioning

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No.6

4. Schedule

Refer to Table 2 for the proposed implementation schedule. Detailed design and manufacturing of the access and investigation equipment/in-plantverification (unit test)/mockup tests/work training/on-site demonstration will be implemented based on the results of this term.
Table 3

Proposed implementation schedule (FY2021 onwards)
FY2022

FY2021Item

FY2023
onwards

Master schedule
The work indicated by the alternate longand short dashed line is outside thescope of this project.
The work indicated by dotted line is
implemented as needed.

MRI (Interim report)

MRI (Final report)

MRI* (Interim
report)IRID in-house project Detailed Investigation
Inside PCV (Deposits PJ)

Work training
On-site demonstration

1. Planning and updateof the investigation anddevelopment for
detailed investigation
inside the pedestal(i) Planning of theinvestigation plan

Investigation planning(ii) Development
planning

Development planning
Detailed designing of the access and investigation equipment and investigation

Development oftechnology fordetailed
investigation
inside pedestal
through thepedestal CRD
opening (R&D)(i) Detailed designing,
manufacturing and unit
tests of the access andinvestigation equipment

technology
Manufacturing of the access and investigation

2. Development ofaccess and investigationequipment andinvestigation technology
for detailed investigation (ii) Mock-up tests
inside the pedestal(iii) Planning for on-site
demonstration (onsite
investigation)equipment

In-factory verification (unit test)

Designing and fabrication of mock-up test facility
Mock-up tests

Development of the plan for on-site demonstration (onsite
investigation)©International Research Institute for Nuclear Decommissioning

MRI*: Mitsubishi Research Institute, Inc.

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No.7

5. Project Organization
Figure 4 shows the project organization of this project.
Technology Research Association International ResearchInstitute for Nuclear Decommissioning (IRID) (Headquarters)○○

Coordination of overall planning and technology
management
Coordination of technology administration including
technology development progress management

Tokyo Electric Power Company
Holdings, Inc.
○

Various coordination for site application

Hitachi-GE Nuclear Energy, Ltd.
Cooperating development project teams(1) Planning and development of detailed investigation inside
the pedestal(2) Development of the access and investigation equipment
and investigation technology for detailed investigation inside
the pedestal

Cooperation

Development of Technology for Detailed Investigation
inside PCV(On-site demonstration of technology for detailed
internal investigation using X-6 penetration)

Development of Technology for Increasing the
Scale of Fuel Debris Retrieval in Stages

Development of Sampling Technology for
Retrieval of Fuel Debris and Internal Structures
Development of Technology for Containing,
Transfer and Storage of Fuel Debris
Development of Analysis and Estimation
Technologies for Fuel Debris Characterization
Development of Technology for Investigation
Inside RPV
Research and Development for Treatment
and Disposal of Solid Waste

Figure 4: Project Organization©International Research Institute for Nuclear Decommissioning

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No.8

6. Implementation Details
6.1 Planning and update of investigation and development for detailed investigation inside the pedestal
A conceptual study for moving the access and investigation equipment from the X-2 penetration to the CRD opening andinvestigating the inside of the pedestal was carried out in previous project. Based on the results of the previous project, theproject involves planning for investigation inside of the pedestal and for development of the access and investigationequipment, etc. and updating as required.

Inside the pedestal
CRD opening

X-2 penetration
B1 investigationequipment (stack)Assumed traveling route of
the access and investigationequipment

Figure 5: Estimated traveling route of the access and investigation equipment inside PCV©International Research Institute for Nuclear Decommissioning

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No.9

6. Implementation Details
6.1 Planning and update of investigation and development for detailed investigation inside the pedestal
Based on the investigation plan and results of development plan studied in the previous project, planning and update ofinvestigation as shown below are carried out as part of this project.

Table 4: Investigation planning and development plan
Study items
Investigation planning

Development planning

Study details

Study results

Planning forinvestigating inside thepedestal① Setting and updating of the investigation goals according to the investigation needs② Verification of the design conditions (temperature, humidity, radiation, CRD opening dimensions,presence of interfering objects, dimension conditions, etc.) inside the PCV and inside thepedestal③ Verification of the details (images, radiation dose, point cloud data, etc.) of the investigation inside
the pedestal④ Planning and updating for investigating inside the pedestal based on ② and ③ mentioned above.

Overall plan pertaining
to the investigationequipment, equipment
and machines① Identification of the technological requirements and design specifications required for the accessand investigation equipment② Identification of support equipment (cable feeding equipment, installation equipment, seal box,etc.) required for the investigation, and study of the design and specifications

Development ofinvestigationequipment andinvestigation
technology① Details of equipment development
・Detailed designing of the equipment based on test manufacturing results from previous project・Study of unit tests and mock-up test details, and study of the testing facility overview② Equipment development schedule
・Equipment manufacturing schedule, unit tests, mock-up test schedule③ Risk assessment concerning equipment development

Planning of on-site
demonstration (onsite
investigation)① Plan for functional requirements of equipment (boundary function, emergency collection function,
shielding function,dust prevention and waterproofing, remote operation function, etc.)② Field work planning for investigating inside the pedestal (the number of working days andworkers, etc.)©International Research Institute for Nuclear Decommissioning

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No.10

6. Implementation Details
6.1 Planning and update of investigation and development for detailed investigation inside the pedestal≪Setting the investigation goals according to the investigation needs≫
Table 5 shows the investigation goals (proposed) and use application of the results studied in the previous project. In the
project, Table 5 is updated as required, and the final investigation goals are set.

Table 5: Investigation goals (proposed) and use application of results
Investigation location

Investigation goals (proposed)

Use application of results

・Checking for presence of interfering
objects
・Checking whether or not entering inside
the pedestal is possible
・Verification of radiation dose・Study of the viability of side access method
・Designing of the fuel debris retrieval equipment

・Checking the status of damage ofplatform
・Verification of interfering objects andfallen objects
・Verification of radiation dose・Assessment of the 3D structure

・Designing of the fuel debris retrieval equipment

Upper part inside the pedestal

Visualobservation
Radiation (γ)
Point cloud data

・Verification of the status of damage of
RPV bottom
・Verification of radiation dose・Assessment of the 3D structure

・Designing of the fuel debris retrieval equipment
・Verification of the viability of bottom access forinvestigation inside RPV・Verification of interfering objects andfallen objects
・Verification of radiation dose・Assessment of the 3D structure

・Designing of the fuel debris retrieval equipment

Lower part inside the pedestal (partiallysubmerged)

Visualobservation
Radiation (γ)
Point cloud data

CRD opening, above the CRD rail,
inside the X-6 penetration

Investigation
items
Visualobservation
Radiation (γ)
Visualobservation

Equipment for replacing CRD inside thepedestal

Radiation (γ)
Point cloud data

©International Research Institute for Nuclear Decommissioning

10No.11

6. Implementation Details
6.1 Planning and update of investigation and development for detailed investigation inside the pedestal《Prospect of investigation inside the pedestal (1/2)》
The following visual data were obtained in the previous project, which helps to understand the situation inside the pedestal.
① Status of damage of CRD system, status of adhering of fuel debris, status of opening till the RPV bottom [Figure 6, 7]② Water surface of accumulated water [Figure 8]
The purpose of this project is to develop technology for acquiring information including radiation dose, point cloud data andvisual datas.

CRD system

CRD system

GratingA
Investigation
cameraB

Accumulated water

Figure 6: Illustration of the inside of
the pedestal

Water surfaceof accumulated water

Figure 7: Illustration of a view
seen from the A position

Figure 16: Illustration of aview seen from the B position©International Research Institute for Nuclear Decommissioning

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No.12

6. Implementation Details
6.1 Planning and update of investigation and development for detailed investigation inside the pedestal《Image of investigation inside the pedestal (2/2)》
The investigation inside the pedestal is conducted to acquire
images from all directions inside the pedestal are acquired using
the pan-tilt camera at the tip of the extension rod.

RPV bottom

Moreover, three-dimensional structural information is acquired by
mounting a sensor for measuring point cloud data.
： Area that can be investigatedTelescopic rod

Investigation equipment

CRD system
Pan-tilt
cameraConcrete
inner wall

Telescopic rod

Figure 10: Area that can be visually confirmed by the equipment forinvestigating inside the pedestal (A view / Upper part of the pedestal)

2.5m

Pan-tilt
cameraPan-tilt
cameraTelescopic rod

Concrete
inner wall
Figure 9: Area that can be visually confirmed by the equipment forinvestigating inside the pedestal (horizontal)

1.7m

Accumulated water

1.8m

Figure 11: Area that can be visually confirmed by the equipment for investigating
inside the pedestal (A view / Lower part of the pedestal)©International Research Institute for Nuclear Decommissioning

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No.13

6. Implementation Details
6.2 Development of the access and investigation equipment and investigation technology for detailed investigation
inside the pedestal《Implementation overview of the development of access and investigation equipment and investigation technology》
The following items concerning the access and investigation equipment and investigation technology are implemented in thisproject, based on the results of the conceptual study on the access and investigation equipment conducted in previous project.
Table 6: Study items and implementation overview
Study items

Study details

Implementation overview

Detailed designing &manufacturing

Designspecifications

All equipment used for on-site demonstration are designed and manufactured based on the test manufacturing
results from previous project, such that they meet the required specifications (performance, reliability, emergency
retrieval, contamination countermeasures, etc.).

In-plant verification(Unit tests)

Verification items

In-plant verification is conducted to verify that all equipment used for on-site demonstration meet the required
specifications (performance, reliability, emergency retrieval, contamination countermeasures, etc.). Then, therequired equipment improvements are made.

Mock-up test

Testing facility

The area that the workers and equipment can access is manufactured at full-scale during the investigation inside
the pedestal.
(Length 20m x width 10m x height 10m)

Mock-up test

It is confirmed that detailed investigation inside the pedestal can be conducted by simulating the actual equipment
conditions and following the same procedures as those for actual equipment. The number of estimated workers
are 10 to 20 (based on past record of the previous project).

Approx. 20m

Air lock roomX-2
penetration

B

Inside thepedestalA
Scope ofsimulation of
the testing
facility

CRD railFigure 12: Scope of simulation of test equipment

Figure 13: View seen from A(access route）

Figure 14: View seen from B (PLR shielding:
before the earthquake disaster)©International Research Institute for Nuclear Decommissioning

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No.14

6. Implementation Details

6.2 Development of the access and investigation equipment and investigation technology for detailed investigation
inside the pedestal
Table 7: Illustration of the configuration of the equipment for investigation inside the pedestal
Composite cable

Extension rod

Investigation
instrument

CRD opening

Pedestal

Traveling part

Installation equipment for theinvestigation equipment

Equipment for investigating inside the pedestal

Hole cover

Seal box(For the cable
feedingequipment)

Hole cover installation
X-2 penetrationequipment

Traveling route

Cable drum

Air lock room

Cable feeding equipment

Seal box (For theinvestigation equipment)

Monitoring
camera(Chamber)Seal box, etc. (layout of air lock room)©International Research Institute for Nuclear Decommissioning

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No.15

6. Implementation Details
6.2 Development of the access and investigation equipment and investigation technology for detailed investigation
inside the pedestal
B3 investigation: Detailed
In the previous project, a prototype of the equipment for investigating inside the pedestal
was manufactured, and functional verification tests were conducted. In this project, detailed
design and manufacturing of the equipment is performed for a practical use.

Investigation inside PCV (Deposits)
CRD
opening

Table 8: Equipment specifications for the equipment for investigating inside the pedestal
Pedestal
Site on theequipment

Required specifications (functions)

Traveling part・Should be able to cross over the B1 investigation equipment left behind, and reach the area in the vicinity of the
CRD opening

Extension rod

・Should be able to extend and retract the extension rod (air type) to 5m・Should be able to control the length of the extension rod
・Cable should be embedded in the extension rod

Investigation
instrument

・Should investigate the fuel debris and structures inside the pedestal with the help of a pan-tilt camera
・Should measure the dose rate inside the pedestal by mounting a sensor for measuring the dose rate・Should measure three-dimensional point cloud data using a sensor (stereo-camera, etc.) for acquiring the point
cloud data

Hole for the B3
investigation ROV

Location where theB1 investigationequipment was left
behindTraveling routeX-2 penetration

Investigation
instrument

Extension rod (5m)Figure 15: Traveling route of the investigation equipment
inside PCV (assumed)

Extension rod (5m)Pan-tilt mechanism

Investigation
instrument
Flipper type crawler
Figure 16: Equipment for investigating inside the pedestal

Figure 17: Equipment for investigating inside the pedestal©International Research Institute for Nuclear Decommissioning

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No.16

6. Implementation Details
6.2 Development of the access and investigation equipment and investigation technology for detailed investigation
inside the pedestal

In previous project, the inside of the pedestal was simulated as a dark area and it was verified that simulated structures and fueldebris can be observed. In this project, acquiring data including images, dose rate from inside the pedestal is studied.

Table 9: Visual images being captured by the equipment for investigation inside the pedestal
Scope of capturing the image (photo of the test piece)
Photographed by inserting the camera into the pedestal (View A,
B)

AB

Example of capturing the test image (result of the previous project)
The simulated structures and fuel debris are clearly visible even in the dark.

Dark area

CameraInvestigation equipment

View A

Simulated fuel debris
Simulated fueldebrisVisual data captured by the investigation instrument (camera)(Image from View A)

Assumed water level(Height of the sandbags)

Simulated CRD

View B
Assumed water level(Height of the sandbags)

Inside the pedestal Test simulation

Visual data captured by the investigation
instrument (camera) (Image from View B)©International Research Institute for Nuclear Decommissioning16

6. Implementation Details

No.17

6.2 Development of the access and investigation equipment and investigation technology for detailed investigation
inside the pedestal
In previous project, a prototype of the ancillary equipment for investigating inside the pedestal was manufactured, andfunctional verification tests were conducted. In this project, detailed design and manufacturing of the ancillary equipment isperformed.
Table 10: Required specifications for the ancillary equipment for investigating inside the pedestal
No.

1

2

Equipment

Hole cover installationequipment

Installation equipment

Preconditions

Hole cover・Should be able to insert the investigation equipment from the X-2
penetration, install it on the first floor grating inside PCV and retrieve it,by means of remote operation.

Investigationequipment

Camera3

Cable feeding
equipment

4

Seal box(Including cable drum)

5

Monitoring camera(Including the chamber)Cable grabbing andfeeding part

Seal box(including cable drum)

Monitoring camera(chamber)・Should be able to remotely install and retrieve the cover for the holefor ROV by means of remote operation.
・The investigation equipment should be able to travel over the holecover.

・Should be able to grab and move (including correction of the cableroute) the cables of the investigation equipment by means of remote
automatic operation.
・Should be capable of feeding cable into the investigation equipment bymeans of remote operation.
・Should be able to monitor the movement of the investigationequipment and the status of the surrounding area by means of thecamera provided.
・Should be able to maintain the PCV boundary for the investigationequipment and other equipment.
・Dimension should be such that it can be carried into and installedinside the air lock room.
・Should be able to be inserted from 200A (through hole of diameter
200mm opened in the X-2 penetration) and monitor various works
inside the PCV.
・Should be able to maintain the PCV boundary, and the dimensions
should be such that it can be carried in and installed inside the airlock room.
©International Research Institute for Nuclear Decommissioning17

6. Implementation Details
6.2 Development of the access and investigation equipment and investigation technology for detailed investigation
inside the pedestal
The status of progress of FY2021 is given below.

No.18

Table 11: Status of development of the equipment for investigating inside the pedestal and other items
FY2019 to FY2020 (preceding project)

No.

Equipment

Back and forth traveling of the investigationequipment(including crossing over the B1 investigationequipment)
Access to the inside of the pedestal(Extension rod)1

Equipment forinvestigating inside thepedestal

FY2021 (April 2021 to March 2022)

Required specifications

Composite cable

CameraInvestigati
oninstrument

Point cloud data sensor

Radiation sensor (dosimeter)

Installation and retrieval of cover for closing
the hole for ROV on first floor grating

Remarks
Initial plan

Advancement

Designing & Manufacturing● (Crawler)● (Flipper type crawler)● (Additional improvements)

Item 6.2.1● (4m)● (5m, enclosed in the cable,
can halt arbitrarily)● (Additional verification tests)

Item 6.2.2－－● (Structural study / verification test)

Item 6.2.3- (B2
investigation
results
available)- (B2 investigation results
available)- (B2 investigation results available)

-

－

－

● (Method selection, conducting elemental tests)

Item 6.2.4- (B2
investigation
results
available)- (B2 investigation results
available)● (Conducting elemental tests, cable selection)

Item 6.2.5●● (Improvement)● (Additional improvements)

Item 6.2.62

Hole cover installationequipment

3

Installation equipment for
the investigationequipment

Insertion of the investigation equipment into
the first floor grating inside the PCV from theX-2 penetration, and its retrieval●● (Improvement)● (Additional improvements)

Item 6.2.7

4

Cable feeding equipment

Investigation equipment cable adjustment●● (Improvement)● (Verification using the composite cable for theactual equipment)

Item 6.2.8

5

Seal box(Including cable drum)

Maintaining the PCV boundary for theinvestigation equipment and other equipment－(Results areavailable)－(Results are available)● (Considering the structure, manufacturing)

Item 6.2.9

6

Monitoring camera

Ancillary equipment required for investigation
with actual equipment－(Results areavailable)－(Results are available)● (Improvement and verification test)

Item 6.2.10

Legend ●: Method determination and improvement， ―： Utilization of existing developed products©International Research Institute for Nuclear Decommissioning

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No.196.2.1 Status of improvement in the traveling part

(1) The following improvements in the investigation equipment were made in response to the issues persisting after
previous project and for further functional enhancement.
① Addition of a guide at the back for enhancing traversing efficiency② Review of the rear motor part for reducing interference while traversing (adjustment of the motor layout)③ Reduction in weight for enhancing traversing efficiency (Changed the material from SUS (42kg) ⇒ Duralumin (33kg)④ Increase in the tip roller diameter fro enhancing traversing efficiency⑤ Improvement in the crawler for enhancing traversing efficiency (Motor output increased 1.6 times, width of the belt
increased from 30mm ⇒ 60mm)(3) Reduction in weight by changing the material[Investigation equipment during previous project](2) Review of the rear
motor part

[Investigation equipment after
improvements](1) Addition of guide at
the back

Improvement(4) Increase in diameter of the tip roller(5) Increase in belt widthfrom 30 -> 60mm

Figure 18: Improvements in the investigation equipment©International Research Institute for Nuclear Decommissioning

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No.206.2.1 Status of improvement in the traveling part(2) The results of the test on back and forth traveling of the investigation equipment are indicated below.
Table 12: Result of verifying back and forth traveling
Test item

Test details

Traveling test of theinvestigation equipment

The movement and cable behavior
when the investigation equipment
travels (including crossing over the B1
investigation equipment left behind) is
verified.

[Test status]

Test results

Good

・The equipment was able to travel by moving forward while checking the status
by means of the camera on the cable feeding equipment and the camera image
from the investigation equipment.
・Even if the cable got caught, it was released with the help of the cable feeding
equipment.
・The B1 investigation equipment left behind crossed over. (onward route/returnroute)
・The B1 investigation equipment left behind crossed over even if it was wet due towater droplets (assuming the conditions when using actual equipment).
Camera images from the cable feeding
equipment (View A)[Status of cable release]

Cable feeding equipment

Cable feeding equipment Composite cable

ReleaseA
B1 investigation equipment left
behindInvestigation equipment

Camera on the cable feeding equipment

The composite cable is grabbed and released if it gets caught.
©International Research Institute for Nuclear Decommissioning

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No.21

6.2.2 Status of improvement in the extension rod(1) Status of the previous project① Duration of extending (retracting) 5meter-extension-rod is approx. 3 minutes. Air leaked from the seal part therefore themovement was not stable.
② Deflection arisen when extending the rod.
・ Rod angle 20.6°: Deflection 1.76meters
・ Rod angle 43.5°: Deflection 0.9meters③ The length of the rod was controlled by direct visual confirmation.
⇒ The structure needs to be revised with respect to countermeasures for air leak and deflection reduction, reduction intime required for extension, and rod length control by remote operation.

Extension rod (5meters)

Deflection
0.9m

Investigationequipment

Deflection of the extension rod

Figure 19: Extending of the extension rod (5 meters)

Height at each location

3000
2500

Rod angle
43.5°

2000
1500

Deflection
1.76m

1000
500

20.6°

0
1

2

3

4

5

Position of the extension rod (m)Figure 20: Status of deflection when the rod is extended©International Research Institute for Nuclear Decommissioning

21

No.22

6.2.2 Status of improvement in the extension rod(2) Improvements in the extension rod are given below.

① [Countermeasures for deflection and air leak] Review of the seal part structure ⇒ Enhancement of leakage prevention performance ofthe seal part・ The packing was deformed due to the load applied to the guide part (the part overlapping with the extension rod) resulting in an air
leak. The structure was improved so that the packing does not get pushed in the axial direction,
・ The hardness of the packing was reduced (A85⇒A65), so that it can accommodate the change in shape when the rod is extended.
Nut

Packing

Male screw (pipe)
Surface A

O ringBack-up ring

Packing
(A85)
Nut

Seal
housing

Packing(A65)

Improvement

2nd stage of the rod

2nd stage of the rod

1st stage of the rod

Guide part

Figure 21: Seal part developed in the previous project
1st stage of the rod
1st stage of the rod

1st stage of the rod

Figure 22: Improvements in the seal part packing
2nd stage of the rod
1st stage of the rod

2nd stage of the rod

Extension
2nd stage of the rod

Figure 23: Extending of the rod©International Research Institute for Nuclear Decommissioning

22

No.236.2.2 Status of improvement in the extension rod
The test results for confirming deflection after improvements is indicated below.
Table 13: Results of the extension rod extension confirmation (deflection confirmation)
Test item

Test details

Test results

Extension rod extension
confirmation test

③ Deflection confirmation
・Rod angle: approx. 20°
・Weight at the tip: 400g(*1) or 900g(*2)

Good

Test status

Height at each position (mm)Before improvement: Deflection 1.76m ⇒ After improvement: Deflection 0.47m⇒ The deflection could be reduced.

Measured
測定日on

Rod
angle
ロッド角度

Weightat the tip
先端重量

1m

2m

3m

4m

5m

(1)2021/3/18

20.6°

400g

350

380

315

210

0

(2)2021/7/8

20°

400g

450

715

930

1095

1245

(3)2021/10/14

20°

900g

445

680

855

995

1078

Deflection
Deflection(2) Measured data

Reduced deflection(1): Deflection to the extent that the tip touches the floor(2): Secured a height of approx. 1.25m to reduce bending ⇒ Reduced deflection(3)： Secured a height of approx. 1.08m ⇒ The weight at the tip was 900g and hence the deflection
increased by approx. 0.17m as compared to when the weight was 400g.

(1) Measured data

(2) At the time of measurement
Deflection

1245

1095
930

715
450

Rod length when extended (m)(1) At the time of measurement
0

5m

4m

3m

2m

4m

3m

2m

1m

(3) At the time of measurement

350

380

315

210

5m

1m

(*1) The weight of the instruments (camera + radiation sensor or camera + point clouddata sensor) planned to be mounted at the rod tip is assumed for the 400g weight at
the tip.
(*2) The weight of the instruments (camera + radiation sensor + point cloud data sensor)
planned to be mounted at the rod tip is assumed for the 900g weight at the tip.

1078

995

855
5m

4m

3m

680
445
2m

1m

©International Research Institute for Nuclear Decommissioning

23

No.246.2.2 Status of improvement in the extension rod② [Measures to reduce the time required for extension] The structure of the rear end of theinvestigation equipment was reviewed and the air inlet of the extension rod was enlarged.
⇒ Increase in flow rate of air supplied into the rod
・ Inner diameter of air tube： Φ6.5 ⇒ Φ7.5
・ Air tube joint: Φ2.5 ⇒ Φ7.5

Air tube(Inner diameterΦ6.5)

Air tube joint(Inner diameter Φ7.5）

Improvement
Air tube joint(Inner diameterΦ2.5)

Figure 24: Air inlet developed in previous project

Air tube(Inner diameter Φ7.5）

Figure 25: Improvements in the air inlet©International Research Institute for Nuclear Decommissioning24

No.256.2.2 Status of improvement in the extension rod
The results of the test for verifying extension movement after improvements is indicated below.
Table 14: Verification of the extension rod movement in each instance of weight at the tip （in combination with the cable drum)
Test Item

Test details

Test results

Extension rod extension
verification test

Verification of time required for the extension
movement
・Rod angle: 20°
・Weight at the tip: 0.4kg/ 0.9kg/ 1.5kg

Extension (retraction) time: approx. 1 minute 20 seconds

Good[a. 0.4kg weight at the tip]a. When weight at the tip is 0.4kg: The posterior end of the crawler does not get liftedb. When weight at the tip is 0.9kg: The posterior end of the crawler does not get lifted (the rod
gets deflected)
c. When weight at the tip is 1.5kg: The posterior end of the crawler gets lifted and it could getoverturned.
⇒ Maximum weight on the tip to be up to 0.9kg.

[c. 1.5kg weight at the tip]

Rod angle: 20°

Posterior end of
the crawler does
not get lifteda. 0.4kg weightat the tip
The tip touches the ground

Posterior end of the crawler gets lifted(Risk possibility of being overturned)[b. 0.9kg weight at the tip]
Cable drum

Rod angle: 20°

B. 0.9kg weight at the tip (*1)[Rod gets slightly deflected]

Posterior end of thecrawler does not get lifted
Composite cable(*1)
The weight of the instruments (camera + radiation
sensor + point cloud data sensor) planned to be
mounted at the rod tip is assumed for the 0.9kg weightat the tip.
Investigation equipment©International Research Institute for Nuclear Decommissioning25

No.266.2.2 Status of improvement in the extension rod
The results of verifying the range of visibility at the time of extension are indicated below.

Table 15: Results of the extension rod extension verification (range of visibility)
Test item

Test details

Test results

Extension rod extension
verification test

Insertion verification and verification of rangeof visibility
Good・Structures that were 5m ahead were visible in a dark environment.
・The rod could be extended inside the pedestal while checking the position of the laser
point on the camera image. In this case, it was confirmed that the rod can be extended
through the ladder, which was an on-site interfering object.

Test status

Simulated RPV bottom
CRD opening

Laser pointerLadder (on-site
interfering object)

Extension rod
Investigationequipment

Simulated
RPV bottom

Cable drum(a) Status of the test (outside the pedestal)
Structures(e) Visual data obtained from themounted camera (above position (d))

Structures

Extension rod

CRD
opening(b) Status of the test (inside the pedestal)

Extension rod(c) Status of the test (cable
drum)(d) Status of the test (from thebottom inside the pedestal)(f) Visual data obtained from themounted camera (in front of position (d))©International Research Institute for Nuclear Decommissioning

26

No.276.2.3 Status of the study of composite cables(1) Composite cable for the investigation equipment
An overall outline of the composite cable for the investigation equipment is given below. The investigation equipment power cable andthe cable for the extension rod (including the cable for the investigation instruments inside the rod) were combined to form a composite
cable.
A cable drum for the composite cable and for the extension rod are installed in the seal box to facilitate the in and out movement of thecables.
(*1) Cable for the investigation
Inside PCV

instrument (inside the rod)

Outside the PCV (air lock room)

LegendCable inside the rod
Equipment power cable(*3)(*2) Cable for the extension rod（metal braided flexible）

Seal box

Cable feed mechanism forthe investigation instrument

Composite cable

Cable drum forthe extension rod(*1) Cable for the investigation instrument (inside the rod)

Composite cable (30m)

Equipment power cable
Cable feed mechanism
for the investigation
instrument(*3)

Composite cable drum

Equipment power
cable
Enlarged viewof the posteriorend(*2) Cable for the extension rod（metal braided flexible）

Composite cable

Equipment power
cable

Figure 26: An overview of the investigation equipment composite cable©International Research Institute for Nuclear Decommissioning

27

No.286.2.3 Status of the study of composite cables(2) Configuration of the composite cable for the investigation equipment
An overall outline of the composite cable for the investigation equipment is given below. The composite cable is made by placing thecable for the extension rod（metal braided flexible) at the center with the other cables placed around it, taping it together and then covering
it with a sheath.
Further, the status of the test in which the investigation equipment and cable drum are combined with the composite cable is indicatedin Table 16.
Hold down tapeInternal tube for the extension rod
tip investigation instrument (Φ8)

Sheath

Bending radius: 200

Cable
ケーブル

１

ＳＳ３００Ｒ
ＡＷＧ２２×２Ｃ
SS300R AWG22×2C

φΦ ４．４4.4

２

ＳＳ３００Ｒ
ＡＷＧ２２×３Ｃ
SS300R AWG22×3C

φΦ ４．６4.6

３

φ１３カメラケーブル
Φ13 camera cableφΦ ５．０5.0

４

Φ8 camera cable
φ８カメラケーブルφΦ ２．３2.3

５

エアチューブＴＳ０８０６
Air tub
TS0806φΦ ８．０8.0

６

エアチューブAir tube７

Air tube
TS0425エアチューブＴＳ０４２５4.0
φ Φ４．０８Flexible
metal hose KIH16
金属フレキホースＫＩＨ１６

Φ 21.1
φ２１．１

９ステンレス鋼Stainlesssteel

φ Φ３．０3.0

Ｔ０４２５
T025Φ .4.4

φΦ ４．０
4.0

Figure 28: Creating of the composite cable

Figure 27: Configuration of the composite cable©International Research Institute for Nuclear Decommissioning28

No.296.2.3 Status of the study of composite cables(3) Investigation equipment, composite cable and cable drum combination test
Table 16: Investigation equipment, composite cable and cable drum combination test results
Test item

Test details

Test results

Extension rod extension
verification test

Test for verifying the rod extension when theinvestigation equipment, composite cable and cable
drum are present in combination (Weight at the tip:
0.4kg)

Findingissues

① 1 drum winding: The extension rod can be extended and retracted② 2 drum windings: The extension rod cannot be extended and retracted (operational
failure)(Issue)If there are more than one cable drum winding, it would cause operational failure of theextension rod. Hence, in order to reduce the number of drum windings (excess cable length)
as much as possible, the length of the composite cable was reviewed (30 → 25m)

① Status of rod extension in the case of 1 cable drum winding: Can be extended and retracted

Cable drum (1 winding: 2.5m)

Rod can be extended with apressure of 0.2MPa
Excess length of the cable② Rod extension in the case of 2 cable drum windings: Cannot be extended and retracted (operational failure)
Excess lengthof thecable
Cable
feedingequipment
Investigationequipment

Rod extension stops atstage 7

Number of windings of the remaining composite
cable on the cable drum

©International Research Institute for Nuclear Decommissioning

29

No.306.2.4 Status of study of point cloud data sensor(1) Measurement range of point cloud data sensor
During the investigation inside the pedestal, measurement (radius 5m or more) is performed using the measuring
instrument (point cloud data sensor) mounted at the tip of the extension rod of the investigation equipment as shown in
the figure below.

Investigationequipment

Instruments (tip of theextension rod)

Figure 29: Range of measurement during the investigation inside the pedestal©International Research Institute for Nuclear Decommissioning30

No.31

6.2.4 Status of study of point cloud data sensor(2) Assumed cumulative dose during the investigation inside the pedestal

Based on the duration of work of the investigation equipment inside the PCV and the dose rate (including
assumptions) inside the PCV, the cumulative dose of the γ rays received by the investigation equipment was
assumed to be 140 to 240Gy.
Table 17: Duration of investigation inside the pedestal and dose rate (assumed)
Inside the pedestal

CRD opening
No.

Item

1

Installation
X-2 penetration to B1 investigationequipment left behind
Investigation of the area in thevicinity of B1 investigationequipment left behind
B1 investigation equipment left
behind to the CRD opening
Investigation inside the pedestal
Return route

2
3

4

X-2
B1 equipment left
behind56Time required
for work(hr)

Dose rate(Gy/h)

Accumulated
dose
(Gy)

1

1

1

0.5

8 (*1)

4

0.5

8 (*1)

41

8 (*1)

8

1 to 2100 (*2)

100 to 2003

8 (*1)

24

Travel route*1: Measurements from the B1
investigation (measured in April, 2015)*2： Estimated value
Seal box

Estimated dose rate:
140 to 240Gy

Figure 30: Investigation route inside
the pedestal (assumed)©International Research Institute for Nuclear Decommissioning31

No.326.2.4 Status of study of point cloud data sensor(3) Ease of mounting the point cloud data sensor① Mounting on the equipment tip (Refer to Figure 31)
The equipment needs to be as small as possible considering the risk of interference while installing and retrieving,since there are space constraints at the access location.

Point cloud data sensor mounting partApprox. 820mm
Lid for the opening (for safety)

Interfering object (PLR piping)

Point cloud data sensor mounting part

First floor grating

Figure 31: Status while installing the investigation equipment©International Research Institute for Nuclear Decommissioning32

No.336.2.4 Status of study of point cloud data sensor② Layout inside the cable (Refer to Figure 32 and 33)

Since th camera cable, etc. are inserted simultaneously into the internal cable (Φ8) for the investigation instrument on the tip of theextension rod, the point cloud data sensor cable needs to be Φ5 or smaller. Hence the connection (*) is done using a LAN cable (Φ3.7).
Note that, a USB2.0 can be converted to a LAN cable using a LAN converter and then connected.
(*) As the LAN cable connector cannot be smaller than Φ5, it is necessary to cut off the connector from the cable ⇒ insert the cable into theinternal cable ⇒ and then reconnect the connector.
Instruction
room

100V power
supplyIn front of the airlock roomMainmechanicalbody

Inside the rod

Power adapter
Repeater /extenderInternal tube for the extension
rod tip investigation
instrument (Φ8)
Pan-tilt (4 (4本units)
パンチルト)（φ1.5）
LED
camera (Φ3)
LEDカメラ(φ3）

USB2.0 cable

USB2.0 cable
Internal
tube
内在チューブ（φ８）
3.7mm ultra slim STP

34.5

Rod tip
Cut once.
Reconnect after
passing through TOF depth camera
the internal tube
and rod.

3.7mm ultra slim STP

40

Point clouddata sensor (lessthan
点群データセンサ(φ
5以内）
Φ5)

Figure 32: Cross-section of theinvestigation equipment composite cable

USB-LAN converter
Ranger 2311
(transmitter mass:
88g)

LAN cable 40m

LAN cable 40m

USB-LAN converter(transmitter mass:
89g)

Cable diameter
Φ3.7

Repeater

PoE extender

Cable diameterΦ3.7

Figure 33: Example of mounting on the investigation equipment©International Research Institute for Nuclear Decommissioning

33

No.346.2.4 Status of study of point cloud data sensor(4) Selection of point cloud data sensor
The depth camera listed as No. 9 and the stereo camera listed as No. 10 from among the sensors indicated below, are the primary
choices from the perspective of mounting capability (mounting at the tip of the equipment and inserting into the cable) on the equipment. In
the future, radiation resistance, etc. will be confirmed, and the plan for mounting on the investigation equipment will be designed.

Table 18: Point cloud data sensor selection results
No.

1Classification

LRF

Product name/Model

Manufacturer

UTM-30LX-EW (2-dimensional)

LRF + pan unit (3-dimensional)

Weight(Less than
400g)
300g (〇)

Dimensions(Around 100mm)

Radiation resistance(140 to 240Gy)

Cable

60m (〇)(130) (×)

100MbpsEthernet(〇)

215 (〇)

USB3.0 (×)

62×62×88 (〇)HOKUYOASK Corporation

Measurement
distance(5m or more)

1kg (×)120×62×88 (〇)124g (〇)

175×30×33 (〇)0.2 to 20m (〇)450g (〇)

169×53×52 (〇)1 to 12m (〇)2 to 25m (〇) -USB3.0 (×)
USB2.0 (〇)Evaluation
resultx(Weak anti-fogging
performance)

2

Stereo camera

ZED 2 Stereo Camera

3

Stereo camera

ISC-100XC (Color)
ISC-100VM (Monochrome)4

Depth camera

SCS-Color or
SCS-Mono

ARGO Corporation 53g (〇)109×18×24 (〇)0.3 to 10m (〇)-USB3.0 (×)

5Depth camera

REALSENSE D435

Intel

99×25×25 (〇)0.2 to 10m (〇)290 (〇)

USB3.0 (×)

6

Omnidirectional camera Omni-60

ARGO Corporation 377g (〇)Φ106×54 (〇)--USB3.0 (×)

7Millimeter wave radar

T18PE_01030103_2D

MarubunCorporation

62g (〇)

55×15×90 (〇)10m or more (〇)130 (×)USB3.0 (×)

8Millimeter wave radar

T18PE_01030103_3D

MarubunCorporation

62g (〇)

55×15×90 (〇)10m or more (〇)130 (×)USB3.0 (×)

9TOF depth camera

DCAM710VzenseTechnology

73ｇ (〇)

103×33×22 (〇)0.2 to 8m (〇)200 or more (〇)(tests completed 3/30)

USB2.0 (〇)〇 (light)(LAN conversion)

10

Stereo camera (+RGB
camera)OAK-D OpenCV DepthAI camera(PoE)

Luxonis361g (〇)

130×101×31(△)

0.2 to 38.4m (〇)200 or more (〇)(tests completed 3/30)

1Gbps
Ethernet (〇)Minato Advanced
Technologies, Inc.

75g (〇)

USB3.0 ×(Cable/connector cannot
be reconnected)

Primary choice

USB2.0 〇〇Mounting capability of equipment©International Research Institute for Nuclear Decommissioning

34

No.356.2.4 Status of study of point cloud data sensor(5) Measurement principle of the point cloud data sensor
The measurement principle of the TOF (Time Of Flight) depth camera and the stereo camera from among the point
cloud data sensor selection results (Table 18) is indicated below.

① Measurement principle of the TOF depth camera② Measurement principle of the stereo camera

The TOF depth camera obtains the distance by means ofa technology that uses infrared light to measure thedistance. When infrared light hits the object to be
photographed, the time required for the reflected light toreturn is used to obtain the distance with the formula“Distance = Speed of light x Time”.

The stereo camera is able to obtain the distance up to thetarget object. It calculates the distance using the principle oftriangulation, based on the pixel information of the target
object obtained from 2 cameras.

ObjectFarDistance

Focal length

Distance between
the cameras

Disparity

Reflected light
Lens

Based on the scaling relation between the red
triangle and the green triangle, the distance (z) up to
the object can be calculated with the following
formula.

Irradiated light
Distance = Speed oflight x Time

Near
False-color image of distance information

Imaging
area

Left focal point

Right focal point

Figure 34: Measurement principle of the TOF depth camera
Figure 35: Measurement principle of the stereo camera©International Research Institute for Nuclear Decommissioning35

No.36

6.2.4 Status of study of point cloud data sensor(6) Point cloud data measurement using the TOF depth camera (Example)

Sample data from the point cloud data on structures inside the pedestal measured using the TOF depth camera isgiven below. In the future, multiple point cloud data inside the pedestal will be measured and study of generating
point cloud data on the entire area inside the pedestal will be conducted by connecting the point cloud data.

Image obtained from the camera

Point cloud data

* Reference image captured in the same
direction as the point cloud data on the right.

Figure 36: Point cloud data using the TOF depth camera (Sample)©International Research Institute for Nuclear Decommissioning36

No.37

6.2.4 Status of study of point cloud data sensor(7) Point cloud data measurement using the stereo camera (Example)

Sample data from the point cloud data on the CRD opening measured from inside the pedestal using the stereo
camera is given below.

Visual datafrom the left
cameraVisual data fromthe left camera

Image depicting the point cloud data “from the upper left”
obtained by manipulating the point cloud data

Figure 37: Point cloud data using the stereo camera (Sample)©International Research Institute for Nuclear Decommissioning37

No.386.2.5 Status of study of radiation sensor(1) Radiation sensor

The applicability of the Self-Powered Gamma Ray Detector (SPGD), which is a prime probable option for the radiation
detector to be used for the investigation inside the pedestal, was verified.
Further, as shown in the figure below, SPGD is a passive detector that can measure even if the power supply to thedetector is interrupted.
<Basic structure of the Self-Powered Gamma Ray Detector (SPGD)>

γ raysCollector

EmitterInsulating material① Composed of an emitter, insulating material, and collector② Voltage impression and amplification is not needed.
Electrons<Measurement principle>① γ rays collide with the electrons in the emitter② In order supplement the deficient electrons, electrons flow from the ground into theemitter.
③ The electric current generated as a result of the movement of electrons is measured.

γ raysγ raysCollector

Insulating material

Electric
current

Emitter

Electrons Insulating material

Electrons
Electrons

Collector

Figure 38: Structure of SPGD and its
measurement principle©International Research Institute for Nuclear Decommissioning38

No.396.2.5 Status of study of radiation sensor

Transmission distance: There is minor attenuation depending on transmission distance. It is constant with a margin of error even with
300m transmission.

Current value [pA]

Cable resistance increases by 26%

Average (20.7pA)
Matches with a margin of error

10

Cable length [m]

60

300

100

Figure 39: Transmission distance of the SPGD
Noise resistance: Induced noise is likely to result in an error of 5% or less while measuring 100Gy/h. (High-sensitivity type)
Picoammeter

Measured current [A]High-frequency
noise cablePoweramplifierPulse
generator(Assumed to be several pA during theinvestigation inside the pedestal)

Impact of parallel noise is 12pA

No noiseAt the time of parallel high-frequency
noise current [1MHz, 1A]
Time [s]Figure 40: Noise resistance of the SPGD
©International Research Institute for Nuclear Decommissioning

39

No.406.2.5 Status of study of radiation sensor(2) The results of elemental tests of the radiation sensor are given below.
Table 19: Results of performance tests of the radiation sensor
Test overview and results
Configuration of apparatus

Test layout

Irradiation area

Work area

Picoammeter

Multiplexer

Coaxial cable

Vicinity

Signal wire

100 Gy/h 10 Gy/hIrradiation area
1000 Gy/hExtensionlead wire③ Multiplexer② Cable

0.5
Gy/h

Co60

Φ25×180 (approx. 380g)① Detector

1 Gy/h④ Picoammeter⑤ PC

ResultExternal appearance of the detector

Detector conditions* Measurements

Material of the outer collector

AluminumOuter diameter of the material of theouter collector [mm]25Outer thickness of the material of theouter collector [mm]1.0Insulating material (polyimide)
thickness [mm]0.2

Thickness of inner collector (AI) [mm]0.05

Thickness of emitter (Pb) [mm]0.3

Diameter of the shaft emitter (steel)[mm]

5

Total length of SPGD [mm]180

Length of sensing part [mm]100

Φ25 mm

180 mmWeight: 380 g

Coaxial cable (3.0D2V)* Measurements
Current value [pA]

Specifications

Current value [pA]

Items

Enlarged
BNC
Dose rate [Gy/h]
Dose rate [Gy/h]

BNC

0.3

・ Expected to be able to measure 0.3Gy/h as the minimum measurement accuracy* Since the dose rate inside the PCV is assumed to be 1Gy/h or more, it is believed that there
will not be any issues with the numerical values mentioned above.

©International Research Institute for Nuclear Decommissioning40

No.41

6.2.5 Status of study of radiation sensor(3) The results of selecting the cable for the radiation sensor are given below.

In order to mount the sensor on the equipment for investigating inside the pedestal, the radiation sensor cable needs to beinserted into the inner tube (Figure 42: inner diameter Φ8) for the investigation instrument that is present inside the composite
cable (Figure 41), and for that the cable needs to be thinned further (Φ2.5 or smaller: currently Φ3).
Internal tube for the extension rod
tip investigation instrument (Φ8)

Wrapping tape

Pan-tilt (4 units)
パンチルト
(4本 )
（φ 1.5）
Inner tube
内在チューブLED
camera (Φ3)
LEDカメラ(φ3） （φ８）

Sheath(Φ2.5 x 2
（φ2.5×2本）
units)
Radiation sensors
放射線センサFigure 41: Cross-section drawing of the investigation equipment
composite cable

Figure 42: Cross-section drawing of the inner tube

©International Research Institute for Nuclear Decommissioning41

No.426.2.5 Status of study of radiation sensor

Hence, in order to select a thinner cable with the same performance as the current cable (Φ3: 1.5D2V), a cablethinning verification test (Table 20) was conducted and the sensitivity (current value at the time of irradiation), impact ofcable vibrations, and impact of induced noise were evaluatedAs a result, the Φ2.5 cable (RG316/U) was selected. (Fig. 43)
Table 20: Results of the radiation cable thinning verification test
Item

Summary

Sensitivity

Little variation in the 1/12 second sampling (measurement) in the case of RG-316U,
and little variation in the 1 second sampling (estimation) in the case of RG-178B/U

Vibrations

Little impact in the case of RG-316/U

Induced noise No significant impact was seen in both cases

This cable was selected

Conventional cableThin cable

Figure 43: Probable options for the radiation sensor cable©International Research Institute for Nuclear Decommissioning42

6.2.5 Status of study of radiation sensor

No.43(4) Radiation sensor manufacturing, evaluation test
Table 21: Specifications of radiation sensor
Items

Before thechangeAfter thechangeMaterial of the outer collector

Aluminum

AluminumOuter diameter of the material of theouter collector [mm]2525Outer thickness of the material of theouter collector [mm]

1.0

1.0

Insulating material (polyimide) thickness
[mm]

0.2

0.2

Thickness of inner collector (AI) [mm]

0.05

0.05

Thickness of emitter (Pb) [mm]

0.3

0.3

Diameter of the shaft emitter (steel)
[mm]

5

5

Total length of SPGD [mm]

180

100

Length of sensing part [mm]

100

50

The length was reduced so that it can be mounted on the equipment(The length of the sensing part reduced as the overall length reduced)[Required specifications of radiation sensor]
・Measurement range: 1 to 100Gy/h
Estimated dose rate Outside the pedestal (8Gy/h(*), inside the pedestal (100Gy/h)*1: Measurements from the B1 investigation (measured in April, 2015)
・ Dimensions / mass: Total length 100mm or less / Mass 0.5kg or less(Can be mounted on the extension rod of the investigation equipment)[Manufacturing of the radiation sensor]
・The lower measurement limit of 0.6Gy/h was verified. (The upper limit of 100Gy/h or more
has been confirmed)
・ In order to achieve dimensions that enable mounting on the extension rod of theinvestigation equipment,a radiation sensor with reduced total length and reduced weight (100mm / mass 0.3 kg)
was designed and manufactured.

[Evaluation test overview]・ The sensor is mounted on the investigation equipment, assembly such as inserting thecable inside the composite cable, etc. is performed, and verification is carried out.
・Also, measures against impact of noise on the radiation sensor are verified through tests.

©International Research Institute for Nuclear Decommissioning

43

No.446.2.5 Status of study of radiation sensor(5) The risks pertaining to the development of the radiation sensor, and countermeasures are given below.
Table 22: Radiation sensor development risks and countermeasures (planned)
No.

Risk

Countermeasures and verification method

1

Decrease in current value due to long distancetransmission

Verification method: Transmission distance impact test (measurement of current value for each transmission distance)

2

Drift in current value due to induced noise fromthe cable that is adjacent at the time ofcomposite cable

Countermeasure: Reducing error by extending the time constant (* if there is an impact)
Verification method: Induced noise test (current value/frequency of the adjacent cable is changed and measured)

3

Generation of noise along with vibrations

Countermeasure: Measuring when it is stationary
Verification method: Combination test with the investigation equipment (noise level is evaluated under stationary condition
assuming measurement is performed)

4

Generation of noise due to switching of signal
wire and extension lead wireCountermeasure (system): Developing a differential measurement system that measures 2ch simultaneously so thatswitching of ch is not required
Verification method: System verification test (It is verified that application of the system does not lead to change in thecurrent value)

5

Generation of surge noise from a momentary
eventCountermeasure (operation): Excluding extreme fluctuations in current value from the evaluation

6

Common-mode noise

Countermeasure: Application of a transformer and soft magnetic material
Verification method: Combination test with the investigation equipment (noise level is evaluated under conditions
assuming measurement is performed)

7

Drift in current value depending on the site
environment

Countermeasure (operation): Measuring back-ground (BG) before moving into the irradiation area on the site, andconsidering it as the reference current value when there is no irradiation

8

Wait time until current value stabilizes

Countermeasure: Estimating the stable current value based on the attenuation curve, or considering the maximum
fluctuation to be an error(*If the wait time is long)
Verification method: Demonstration testing of the estimation method (possibility of being able to estimate based on theattenuation curve is verified)

9

Cable disconnection

A method that can determine cable disconnection is developed and verified©International Research Institute for Nuclear Decommissioning44

6.2.6 Status of improvement in the hole cover installation equipment

No.45

The following improvements in the hole cover installation equipment were made in response to the issues persisting after previous
project and for further functional enhancement. The test results were verified that there is no problem in the applicability of the hole coverand the travel efficiency of the investigation equipment.

Table 23: Improvements in the hole cover installation equipment (1)
No.

Items

Status during previous project
The wire had come off from the pulley, it had comeloose, and the suspension balance was lost.

Improvement details
・ Changed the stainless wire rope(Φ2) to a cord with a Kevlar core(Φ2.2 (load capacity 300kg))

Result of verification
Lifting operation was repeated (about 10 times) and it wasverified that the wire was not loose.

1 Revised wire
part
Wire was not loose

Wirehadwas looseWirebeen loosen.

2 Revised thepulley part・Changed the pulley with aseparate shaft and roller to one
in which these are integrated.

Lifting operation was repeated (about 10 times) and it was verified that the pulley
was not getting stuck anywhere.

Pulley part
Changed the pulley witha separate shaft androller to one in whichthese are integrated.

©International Research Institute for Nuclear Decommissioning45

6.2.6 Status of improvement in the hole cover installation equipment

No.46

Table 24: Improvements in the hole cover installation equipment (2)
No.

Items
項目

先行事業時の状況
Status during
previous project

Improvements
改善内容

Verification
results
確認結果• The thickness of the hole cover was 調査装置にて穴カバー表面上を走行し、変形や走行性、設置性に•・調査装置走行時、穴カバー取っ手プレートが強度不The handle plate of the hole cover got bent due to
The investigation equipment was let to travel on the surface of the hole・穴カバーの板厚を3t⇒6tに変更
changed from 3t ⇒ 6t
insufficient strength when the investigation equipment wascover, and it was verified that there is no problem with respect to
足により曲がった。
・表面形状を縞鋼板タイプにて製問題がないことを確認した。
•
The
surfacewasfabricatedusing
traveling.
deformation, traveling efficiency and installation efficiency.
checkeredsteelplates,
and
the
ease
•・走行時に滑りが発生したため、カバー表面の材質見The equipment slipped while traveling. Hence the material of 作し、カバー上の走行性を確認
of traveling on the cover was
No problem in installation efficiency using the hole cover
the surface of the cover needs to be reviewed.
直しが必要。
・穴カバーの形状を拡大
verified.
穴カバー設置装置での取付性も問題無
installationequipment•・現地（先行事業後の2021年6月18日に作業）でのグ
Along with the increase in the size of the grating hole at the • The hole cover was enlarged.
site (work performed on June 18, 2021 after previous
レーチング穴径拡大に伴う、穴カバー径拡大が必要。
project), the size of the hole cover needs to be increased.

Occurrence
of a
曲がり発生
bend

Revisedthe穴カバーの強strength, mass,
3 度・質量・材質、
material, and
形状見直し
shape
of thehole coverHole cover
穴カバー

Frame Lead wool mat
Approx.
600mm

PLR piping,insulating material

No problem of interference or in the traveling efficiency
after調査装置着座後の干渉、走行性も問題無
the investigation equipment is positioned as well.

Approx. 150mm

Approx.
400mm

Approx.
550mm

Lower steel portionof the grating

Portion of the lead wool
mat and grating to be cut

Grating

PLR piping shield©International Research Institute for Nuclear Decommissioning46

6.2.7 Status of improvement in the installation equipment

No.47

The following improvements in the installation equipment were made in response to the issues persisting after previous project andfor further functional enhancement. The verification result was confirmed by means of tests that there is no problem in the ease of
installation and retrieval of the investigation equipment.

Figure 25: Improvements in the installation equipment for the investigation equipment
No.

Items
項目

Status during
previous project
先行事業時の状況

Improvements
改善内容
A
90 ° swivel function was
インストール箇所が狭隘部のため、インストー「Rガイド」と「ラック＆ピニオン」取Since there were space constraints at
added
by installing an “R
ルが困難であった。
付けにより90°旋回機能を追加
the installation location, installation was
guide” and “rack and pinion”
difficult.

Verification
results
確認結果
インストール装置に旋回機能を追加したことにより、調査装置のIt was verified that the investigationequipment can beinstalled due to the addition of the swivel feature to the
インストールが可能であることを確認した。
installation equipment.
【インストール装置】[Installationequipment]
旋回機能の追加
Addition of swivel
featureAdditionof
旋回機能の
1 swivel
追加
functionInterfering
干渉物
objectA notch was added to the
インストール・回収時に装置がずれる事象が発 スコップ部に切欠を追加する。
There was an incident in which the
scoop part.
生した。
equipment slipped out of place during
installation and retrieval.

The stability of the equipment during installation and retrieval was
インストール装置先端スコップ部に切欠きを設けたことにより、インenhanced (prevention of slipping out of place) due to the notch at
ストール・回収時の装置安定性が向上(ずれ防止)し、屈曲・押し出
the scoop part at the tip of the installation equipment, and as a
しの回数が低減され作業時間の短縮に繋がった。
result the frequency of bending and pushing out was lowered thus
reducing the work time.

Addition of
スコップ部の
2 a notch in
切欠追加
the scoop
part
Aスコップ部に切欠
notch was added to thescoop part.

を追加する

Additionof notch at the scoop part
スコップ部に切欠き追加©International Research Institute for Nuclear Decommissioning47

6.2.8 Status of improvements in the cable feeding equipment

No.48

The following improvements in the cable feeding equipment were made in response to the issues persisting after previous project and for further functional
enhancement. The test results were verified avoidance of the interfering roller part at the time of installation, cable feeding and release functions, and that there is nointerference at the time of lifting.

Table 26: Improvements in the cable feeding equipment
No.

Items
項目

Status 先行事業時の状況
during previous projectThe
gear wheel of the roller
ケーブル送り装置のインストー
part
was likely to interfere with
ル時、ローラー部歯車がグレー
thegrating while installing the
チングに干渉する可能性有cable feeding equipment.

Improvements
改善内容
確認結果results
VerificationThe
cable feeding equipment was suspended from the installation equipment
Since the size of the
ローラ直径はφ90mmであ90°屈曲したインストール装置からケーブル送り装置を吊降し、着座時にthat was turned 90°, and it was verified that the roller part does not interfereroller is Φ90mm, the
るため、歯車径をそれ以下
ローラ部がグレーチングに干渉しないことを確認した。
withthe grating while positioning.
gear wheel wasの寸法に変更(φ90⇒ケーブル送り装置用インストール装置
Installationequipment for the cable feeding equipmentchanged to a smaller
84mm)し、干渉を無くす
size (Φ90 ⇒ 84mm) toeliminate theRollerローラ
interference.

Revisedローラー部
1 the gear
歯車見直し
wheel ofthe roller
part

Risk of
干渉懸念
interference
Gearwheel smaller than the roller was used.
歯車径をローラより小さくした

残置B1調査装置等にケーブル
If the cable got caught in theが引っ掛かった際、ｹｰﾌﾞﾙ送り
B1 investigation equipment装置にて解除が困難
left behind, the cable feeding
equipment could not easily
release it.

Increase in
ケーブル送
the
り装置の
elevating
2 ローラー部
length ofストローク
therollerUP in the
part
cable
feedingequipment

It was verified that by changing the elevating length of the cable feeding
ケーブル送り機構部の昇The elevating length of ケーブル送り機構部の昇降ストロークを50mm⇒80mmに変更したことによmechanism from 50mm ⇒ 80mm, the cable can be released if it gets caught in降ストロークを50mm⇒
り、構造物にケーブルが引っ掛かった際の解除が可能なことを確認した。
the cable feeding
any of the structures.
80mmに変更し、ケーブル
mechanism was
Cable feedingmechanism
Composite
cablechanged from 50mm ⇒の解除が可能なようにする
ケーブル送り装置
複合ケーブル80mm to enable releaseof the cable.

Cable needs to
解除要be released

Grabbing the composite
複合ケーブルを把持しcable
and releasing thecaughtcable.
引っ掛かりを解除©International Research Institute for Nuclear Decommissioning48

6.2.9 Status of study of seal box (including cable drum)

No.49

It was verified that there is no problem in operational performance, when the following seal boxes are designed
and manufactured, and combined with each equipment.
In the future, carrying-in and installation will be verified by means of mock-up tests.
(1) Seal box for the cable feeding equipment (including cable drum) [250A] (Refer to Figure 44)(2) Seal box for the hole cover installation equipment [350A] (Refer to Figure 45)(3) Seal box for the investigation equipment (including cable drum) [350A: switched after installing (2)](Refer to Figure 46)

250A: (Existing hole of 250mm in diameter opened in X-2 penetration)
350A: (Existing hole of 350mm in diameter opened in X-2 penetration)©International Research Institute for Nuclear Decommissioning49

6.2.9 Status of study of seal box (including cable drum)

No.50(1) Seal box for the cable feeding equipment (including cable drum) [250A](2) Seal box for the hole cover installation equipment [350A][Installed in 250A] Seal box for the cable feeding equipment[Installed in 250A] Seal box + cable drum for the cable feeding equipment

Cable drum[Installed in 200A] Chamber for themonitoring camera[Installed in 350A] Seal box for the hole cover installation equipment[Installed in 350A] Seal box for the hole cover installation equipment

Figure 44: Installation status of the seal box for the cable feeding equipment and the seal box for the hole cover installation equipment©International Research Institute for Nuclear Decommissioning50

6.2.9 Status of study of seal box (including cable drum)

No.51(3) Seal box for the investigation equipment (including cable drum) [350A: replaced after installing (2)]Cable drum for the investigation equipment

Cable drum

Seal box for the investigation equipment[Installed in 350A]
Seal box for the investigation equipment[Installed in 350A] Seal box + cable drum for the investigation equipment

Figure 45: Installation status of the seal box for the investigation equipment©International Research Institute for Nuclear Decommissioning

51

No.526.2.10 Status of study of the monitoring camera(1) The status of the study of the monitoring camera is given below.
To enhance further functional improvement after the previous project, a bend part of the monitoring camera wasadded for improvement to enlarge the view range. As a result of the test, there was no problem in visibility.
Addition of bend section
Monitoring camera[Image obtained fromthe monitoring camera]

Improvement

Monitoring camera

Figure 46: Status of study of the monitoring camera©International Research Institute for Nuclear Decommissioning52

6.2.10 Status of the monitoring camera

No.53(2) The status of the monitoring camera chamber is given below.
The monitoring camera chamber was fabricated with dimensions such that it can be placed inside the air lockroom. It was verified that there is no problem in operational performance when the monitoring camera is installedinside the chamber.

[Installation in 200A] Monitoring camera chamber

Figure 47: The status of the monitoring camera chamber©International Research Institute for Nuclear Decommissioning

53

No.54

6.3 Mock-up test plan

According to the mock-up test plan, the mock-up test will be conducted at the test facility that was simulated
actual environment (Mock-up tests are planned to be conducted in FY2022).
(*1) Air lock outer door(*1) Air lock outer door(*2) CRD opening

Carry-in route

A photo of the vicinity of the airlock outer door (at the site)
A photo of the carry-in route (at the site)

CRD opening

A photo of the vicinity of the
CRD opening (at the site)(*2) CRD opening

Figure 48: Status of study of the mock-up test facility©International Research Institute for Nuclear Decommissioning

54

No.55

6.4 Issues
A list of work risks in this project is indicated below.
Table 28: List of work risks (1/6)
Work step
Major category
Installation ofmonitoring camera
inside PCV

Installation of cable
feeding equipment
inside the PCV

Anticipated risk

Occurrence
frequency

Countermeasures

The camera gets damaged due to interference withstructures in the surrounding area while the camera
is in operation

MediumSelecting a camera with protective cover so that the lens does not get damaged directly.

The hand rail interferes with the installationequipment when the installation equipment is being
pushed throughHigh・Operating from the most suitable monitoring camera position
・Clearly specifying the operating range by marking the operating pole

The cable drum motor does not move and hence
the cable feeding equipment cannot be suspended.

Low

Enabling the cable drum to be operated manually

The gear wheel part of the cable feeding equipment
gets damaged during positioning.

MediumCircumventing the interference by using a gear wheel part with a diameter smaller than
the grabbing part

MediumMarking the operating pole so that the equipment does not get pushed too much

Medium・Determining the location to be monitored using the bend type dome camera and thecable feeding equipment camera, so that there is no misalignment
・Even then if there is misalignment, grabbing the hole cover, retrieving it and installingagain

Sub-category① Passing the bend type dome camera through the guide pipe
(200A)② Installing the camera at an arbitrary position so that it canmonitor work in the following steps.

① Passing the installation equipment through the guide pipe
(250A)② Pushing through the installation equipment till it crosses thehandrail③ Bending the installation equipment④ Rotating the cable drum and suspending the cable feeding
equipment⑤ Positioning the cable feeding equipment① Passing the hole cover installation equipment through the guide When the hole cover installation equipment is being
pipe (350A)
pushed through, it gets pushed too much and② Pushing through the hole cover installation equipment up to the interferes with the structures.
Covering the opening
opening
for the ROV③ Suspending the hole cover④ Inserting the hole cover pin into the groove on the grating⑤ Releasing the grip and installing the hole cover
While installing the hole cover, it gets misaligned.
⑥ Pulling in and retrieving the hole cover installation equipment① Passing the installation equipment through the guide pipe
(350A)② Pushing through the installation equipment till it crosses the
Installation ofhandrailinvestigation③ Bending the installation equipment
equipment inside PCV ④ Rotating the cable drum and suspending the investigationequipment⑤ When the front crawler part touches the ground, rotating theinvestigation equipment towards the left and suspending it⑥ Positioning the investigation equipment

・Re-examining the shape of the installation equipment scoop to secure larger clearance
・Monitoring with bend type dome camera and cable feeding equipment camera to makesure there is no interference

The hand rail interferes with the installationequipment when the installation equipment is being
pushed through.

MediumThe structures interfere with the installationequipment when the installation equipment is being
pushed through.

High

Marking the operating pole so that the equipment does not get pushed too much

The cable drum motor does not move and hence
the investigation equipment cannot be suspended.

Low

Enabling the cable drum to be operated manually

The structures interfere with the camera at the tipof the investigation equipment when theinvestigation equipment is being suspended.

High・Adding a swivel mechanism to the scoop part of the installation equipment to avoid
interference with the structures
・Clearly specifying the suspension area to make sure there is no interference©International Research Institute for Nuclear Decommissioning55

No.56

6.4 Issues
A list of work risks in this project is indicated below.

B2 investigation: Conducted in March 2017

Table 29: List of work risks (2/6)
Major category

Work step
Sub-category

Anticipated risk
The equipment gets damaged due tointerference with structures in thesurrounding area while the investigationequipment is traveling.

The equipment slips on the grating and isunable to travel and rotate.
The cable drum motor does not move andhence the cable feeding equipment cannot① Letting the cable feeding equipment travel, and moving travel.
it to the position from where the investigation equipment
The cable feeding equipment cannot travel
can be comprehensively monitored
due to issues in the electrical system.
Traveling from X-2
penetration to B1② Letting the investigation equipment travel up to right ininvestigation
The cable drum motor does not move andfront of the B1 investigation equipment left behind, while
equipment left
hence the investigation equipment cannot
rotating the cable drum
behindtravel.
③ If the cable is about to get caught, adjusting the
The investigation equipment cannot travel
position of the cable as needed using the cable feeding
due to issues in the electrical system.
equipment
The cable gets caught in the handrail, etc.
and hence the investigation equipment
cannot travel.
The structures, etc. on the travel routecannot be verified inside the PCV
environment (darkness, steam).
The cable feeding equipment gets
overturned while crossing over thecomposite cable.
① Rotating the investigation equipment while looking at
the position of the laser pointer, and making fine
Extension of rod
adjustments to the extension position
from right in front of② Raising the rod up to the specified hoisting angle
the B1 investigation③ Extending the rod
equipment left
④ Acquiring information on the area in front of thebehindpedestal CRD opening by operating the camera*: Visibility up to inside the pedestal CRD opening isverified during the mock-up tests.
⑤ Retracting the rod

The rod interferes with the structures while itis extended.
Due to breakage of the internal tube air does
not get supplied and hence the rod cannot
be extended.
The extended rod cannot be retracted due to
breakage of the internal tube and problem
with the electrical system.

Occurrence
frequency

Countermeasures

Medium・Planning the layout of the camera in such a way that it can monitor theinterfering objects without any omissions
・Letting the equipment travel while checking for interferences by means of
the bend-type dome camera, cable feeding equipment camera, and theinvestigation equipment camera

MediumEnhancing the performance of the crawler

Low

Enabling the cable drum to be operated manually

Low

Winding the cable drum and retrieving the cable feeding equipment

Low

Enabling the cable drum to be operated manually

Low

Winding the cable drum and retrieving the investigation equipment

MediumLow

Low

MediumLow

Low

Releasing the caught cable using the cable feeding equipment
Using a camera that has been used for investigation inside PCV in thepast (B2 investigation)
Winding the cable drum, retrieving the cable feeding equipment andinstalling once again
・Verifying that there are no interference objects at the extension position
by means of a laser pointer, before extending the rod
・Extending while verifying that there are no interfering objects in thesurroundings by inching ahead
・Passing a Kevlar cord through the internal tube so it does not break・Retrieving the investigation equipment, if it breaks
Winding the cable drum so that the rod can be retracted mechanically©International Research Institute for Nuclear Decommissioning

56

No.57

6.4 Issues
A list of work risks in this project is indicated below.
Table 30: List of work risks (3/6)
Major category
Crossing overthe B1equipment left
behind (onward
route)

Work step
Sub-category① Moving the cable feeding equipment to the backof the investigation equipment so that it can becomprehensively monitored while crossing overthe B1 investigation equipment left behind② Investigation equipment crossing over the B1
investigation equipment left behind

Anticipated risk
While crossing over, the investigationequipment loses balance and gets
overturned.
While crossing over, it interferes withthe surrounding structures (150A piping,etc.)
The equipment gets damaged due tointerference with structures in thesurrounding area while the investigationequipment is traveling.

The equipment slips on the grating andis unable to travel and rotate.
The cable drum motor does not moveand hence the cable feeding equipment
cannot travel.
① Letting the investigation equipment travel up to
The cable feeding equipment cannot
Traveling fromthe front of the CRD opening by rotating the cable
travel due to issues in the electrical
B1 investigation
drum
system.
equipment left
② If the cable is about to get caught, adjusting thebehind up to the
The cable drum motor does not moveposition of the cable as needed using the cable
CRD opening
and hence the investigation equipment
feeding equipment
cannot travel.
The investigation equipment cannot
travel due to issues in the electricalsystem.
The cable gets caught in the handrail,
etc. and hence the investigationequipment cannot travel.
The structures, etc. on the travel routecannot be verified inside the PCV
environment (darkness, steam).

Occurrence
frequency
Low

MediumHigh

MediumCountermeasures
Winding the cable drum and retrieving the investigationequipment
Performing comprehensive monitoring by means of the cable
feeding equipment camera, and checking the front by means of
the investigation equipment camera.
・ Planning the layout of the camera in such as way that it canmonitor the interfering objects without any omissions・ Letting the equipment travel while checking for interferencesby means of the cable feeding equipment camera, and theinvestigation equipment camera
Enhancing the performance of the crawler

Low

Enabling the cable drum to be operated manually

Low

Winding the cable drum and retrieving the cable feeding
equipment

Low

Enabling the cable drum to be operated manually

Low

Winding the cable drum and retrieving the investigationequipmentHigh

Releasing the caught cable using the cable feeding equipment

Low

Using a camera that has been used for investigation inside PCV
in the past (B2 investigation)©International Research Institute for Nuclear Decommissioning

57

No.58

6.4 Issues
A list of work risks in this project is indicated below.
Table 31: List of work risks (4/6)
Major category

Work step
Sub-category

Anticipated risk
The rod interferes with the structures while itis extended.

① Rotating the investigation equipment while looking at
the position of the laser pointer, and making fine
Extending the rod
adjustments to the extension position
to investigate② Raising the rod up to the specified hoisting angle
inside the pedestal ③ Extending the rod④ Acquiring information from inside the pedestal by
operating he camera⑤ Retracting the rod

Backing up to B1
investigationequipment left
behindDue to breakage of the internal tube air does
not get supplied and hence the rod cannot
be extended.
The extended rod cannot be retracted due to
breakage of the internal tube and problem
with the electrical system.
The image sensor of the camera getsdamaged due to the high radiation
environment.
Gets overturned due to the vibrations of theearthquake.
The equipment gets damaged due tointerference with structures in thesurrounding area while the investigationequipment is traveling.
The equipment slips on the grating and isunable to travel and rotate.

The cable drum motor does not move andhence the cable feeding equipment cannot
travel.
① Backing up the investigation equipment from the
The cable feeding equipment cannot travel
investigation location② Letting the investigation equipment travel up to the B1 due to issues in the electrical system.
investigation equipment left behind while supporting the The cable drum motor does not move andcable by means of the cable feeding equipment
hence the investigation equipment cannot
travel.
The investigation equipment cannot travel
due to issues in the electrical system.
The cable gets caught in the handrail, etc.
and hence the investigation equipment
cannot travel.
The structures, etc. on the travel routecannot be verified inside the PCV
environment (darkness, steam).

Occurrence
frequency

Countermeasures

Medium・Verifying that there are no interference objects at the extension position
by means of a laser pointer, before extending the rod
・Extending while verifying that there are no interfering objects in thesurroundings by inching ahead

Low

Low

Low
Low

High

Medium・Passing a Kevlar cord through the internal tube so it does not break・Retrieving the investigation equipment, if it breaks
Winding the cable drum so that the rod can be retracted mechanically

Selecting a radiation resistant camera that has been used in similar
environments (B2 investigation inside PCV)
Verifying by means of mock-up tests whether or not there is a possibility ofgetting overturned・ Planning the layout of the camera in such a way that it can monitor theinterfering objects without any omissions・ Letting the equipment travel while checking for interferences by meansof the investigation equipment camera
Enhancing the performance of the crawler

Low

Enabling the cable drum to be operated manually

Low

Winding the cable drum and retrieving the cable feeding equipment

Low

Enabling the cable drum to be operated manually

Low

Winding the cable drum and retrieving the investigation equipment

High

Releasing the caught cable using the cable feeding equipment

Low

Using a camera that has been used for investigation inside PCV in thepast (B2 investigation)©International Research Institute for Nuclear Decommissioning

58

No.596.4 Issues
A list of work risks in this project is indicated below.
Table 32: List of work risks (5/6)

Work step
Occurrence
Anticipated risk
Countermeasuresfrequency
Major category
Sub-category
Crossing over
① Moving the cable feeding equipment to the back of While crossing over, the investigation
Winding the cable drum and retrieving the investigationequipment loses balance and gets
Low
the B1the investigation equipment so that it can beequipment
equipment left
comprehensively monitored while crossing over the overturned.
behind (returnB1 investigation equipment left behind
While crossing over, it interferes with
Performing comprehensive monitoring by means of the cableroute)② Crossing over the B1 investigation equipment left the surrounding structures (150A
Medium feeding equipment camera, and checking the back by means ofbehind by backing up the investigation equipment piping, etc.)
the investigation equipment camera.
The equipment gets damaged due to
・ Planning the layout of the camera in such a way that it caninterference with structures in themonitor the interfering objects without any omissionsHighsurrounding area while the・ Letting the equipment travel while checking for interferences byinvestigation equipment is traveling.
means of the investigation equipment camera
The equipment slips on the grating
Medium Enhancing the performance of the crawler
and is unable to travel and rotate.
The cable drum motor does not moveand hence the cable feeding
Low
Enabling the cable drum to be operated manuallyequipment cannot travel.
The cable feeding equipment cannot① Letting the cable feeding equipment travel, andWinding the cable drum and retrieving the cable feeding
travel due to issues in the electrical
Low
Traveling frommoving it to a position where the investigationequipment
system.
the B1equipment can be comprehensively monitored
investigation② Backing up the investigation equipment up to right The cable drum motor does not moveequipment leftin front of the X-2 penetration while rotating theand hence the investigation equipment
Low
Enabling the cable drum to be operated manuallybehind up to thecable drum
cannot travel.
X-2 penetration ③ If the cable is about to get caught, adjusting the
The investigation equipment cannot
Winding the cable drum and retrieving the investigation
position of the cable as needed using the cable
travel due to issues in the electricalLowequipment
feeding equipment
system.
The cable gets caught in the handrail,
etc. and hence the investigation
High
Releasing the caught cable using the cable feeding equipment
equipment cannot travel.
The cable feeding equipment getsWinding the cable drum, retrieving the cable feeding equipment
overturned while crossing over the
Low
and installing once again
composite cable.
The structures, etc. on the travel route
Using a camera that has been used for investigation inside PCV
cannot be verified inside the PCV
Low
in the past (B2 investigation)
environment (darkness, steam).
©International Research Institute for Nuclear Decommissioning

59

No.606.4 Issues
A list of work risks in this project is indicated below.
Table 33: List of work risks (6/6)
Major category

Retrieval of theinvestigationequipment

Retrieving thehole cover

Cable feeding
equipment
retrieval

Retrieval of themonitoring
camera inside
PCVWork step
Occurrence
Anticipated risk
Countermeasuresfrequency
Sub-category① Winding up the cable when the investigationequipment comes up to the retrieval position② When the investigation equipment is placed in the
The cable drum motor does not move
scoop part of the installation equipment, bending
and hence the investigation
Low
Enabling the cable drum to be operated manually
the installation equipment to bring it to a horizontal
equipment cannot be wound up.
position③ Pulling in and retrieving the investigationequipment① Passing the hole cover installation equipment
When the hole cover installation
through the guide pipe (350A)
equipment is being pushed through, itMarking the operating pole so that the equipment does not get② Pushing through the hole cover installation
gets pushed too much and interferesHighpushed too much
equipment up to the hole cover position
with the structures.
③ Suspending the wire to a height such that thehandle can be grabbed④ Grabbing the handle⑤ Winding up the wire, and placing the hole cover on
Wire gets overwound and breaks.
Medium Marking the position indicating over-winding
the installation equipment⑥ Pulling in and retrieving the hole cover installationequipment① Winding up the cable when the cable feeding
equipment comes up to the retrieval position② When the cable feeding equipment is placed in the
The cable drum motor does not move
scoop part of the installation equipment, bending
and hence the cable feeding
Low
Enabling the cable drum to be operated manually
the installation equipment to bring it to a horizontal
equipment cannot be wound up.
position③ Pulling in and retrieving the cable feeding
equipment
The camera gets damaged due tointerference with structures in the
Selecting a camera with protective cover so that the lens does not① Pulling in and retrieving the bend-type camera
Mediumsurrounding area while the camera is
get damaged directly.
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6.5 Level of the goal achievement● Level of the goal achievement
As the results of the elemental tests and equipment manufacturing, thespecifications were verified to satisfy its requirements.

• There is a prospect of capturing visual datas of inside the pedestal, where is dark,
by using the camera and extending the extension rod mounted on theinvestigation equipment when it can reach the pedestal CRD opening after
installing inside the PCV through the X-2 penetration and travelling over the firstfloor grating.

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6.6 Future plans

The investigation instruments (point cloud data sensor and radiation sensor) will be mounted to verify the movement. Also, the risk identification andcountermeasures will be implemented by conducting comprehensive tests. Further, the equipment will be continuously improved towards perfection by conducting
in-plant verification (unit tests) and mock-up tests using mock-up test facilities in preparation for the on-site demonstration. Development items and future plans
are indicated below.

Figure 34 : Development items and future plans

2

3
4
5

6

7

Mock-up test

8

On-sitedemonstration
plan

Equipment for investigating
inside the pedestal

Classifi
cationAncillary equipment

1

Items

Detailed designing, manufacturing and unit tests of the access andinvestigation equipment

No.

Testingfacility

Plan

Details

Accomplishments

Future plans

Main body① Traveling up to the pedestal CRD opening② Insertion and retrieval from the access route (350A)➂ Traveling across the B1 investigation equipment left behind④ 5m extension rod with air driveand embedded cables

Composite cable① Thinning of cables to Φ40

Functionalverification
through in-plantverification andmock-up tests

Point cloud data
sensor① Can be used in actual equipment environment (darkness, fog, water droplets, high radiation)② Dimensions and weight such that equipment can be mounted on the tip of the extension rod

Mounting on theimplementationequipment

Radiation sensor① Minimum 1Gy/h can be measured ② Dimensions and weight such that equipment can be mounted on the tip ofthe extension rod

Mounting on theimplementationequipment

Hole coverinstallationequipment① Blocking of the hole for ROV

Installationequipment① Insertion and retrieval of equipment for investigating inside the pedestal into the PCV

Cable feeding
equipment① Grabbing and feeding the composite cable for the equipment for investigating inside the pedestal② Monitoring the work of the equipment for investigating inside the pedestal using the mounted camera

Seal box(Including cable
drum)① Composite cable for the equipment for investigating inside the pedestal can be fed and wound up② Ensuring air-tightness (boundary part)

Monitoring
camera① Work of equipment for investigating inside the pedestal and ancillary equipment (hole cover, installationequipment, cable feeding equipment, etc.) can be monitored

Preparation oftest facility

Designing of the mock-up test facility

Fabrication of the
mock-up test
facility

Commencing mock-up test planning

Study of on-site
demonstration
plan reflecting theresults of the
mock-up test

On-sitedemonstrationplan② Can be remotely installed and retrieved

Functionalverification
through in-plantverification andmock-up tests©International Research Institute for Nuclear Decommissioning

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