Subsidy Project of Decommissioning and Contaminated Water
Management

Development of Technology for Investigation inside
the Reactor Pressure Vessel (RPV)

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

Contents

No.1

1. Research background and objectives
2. Goals
3. Implementation items, their co-relation and relation to other projects
4. Implementation schedule
5. Project organization
6. Implementation details(1) Upgrading of processing technology for the top access investigation method
・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・No. 8(2) Development of the bottom access investigation method- Unit 1: Development of drone for accessing inside RPV・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・No. 46- Units 2 and 3: Development of telescopic equipment for accessing inside
RPV・・・・・・・・・・・・・・・・・・・・ No. 82
7. Summary©International Research Institute for Nuclear Decommissioning1. Research background and objectives[Purpose of investigation inside the reactor
pressure vessel (RPV)]
Acquisition of basic information about RPV interior(distribution of fuel debris, radiation dose, structure
condition, etc.) to retrieve fuel debris.

Top access investigation method

No.2

Side accessinvestigation
method[Implementation details up to FY2019]
Methods for accessing the reactor core by making an
opening from the top and from the side were
investigated (hereinafter referred to as “the top accessinvestigation method” and “side access investigation
method,” respectively). In the previous subsidy project“Development of Technology for Investigation inside theRPV” (FY2018/2019), the functions of both methods
was verified through element tests of equipment for
actual equipment applicability, the concepts of theinvestigation method were organized, and equipment
Bottom accessspecifications were developed by FY2019.
investigation
method[Future applications of this project]
Development of Technology
for Investigation inside the
RPVActualequipment
investigation

Information on RPV interior(visual information, radiationdose rate, etc.)

Examination of fuel debris
retrieval method /equipment design©International Research Institute for Nuclear Decommissioning1. Research background and objectives

No.3[Implementation details of this project]
For the top access investigation method, development of an abrasive water jet (AWJ) method to cut openings in thereactor internals (steam dryer, steam separator, shroud head, etc.) for establishment of an access route into the shroud
was a priority, even though there is little certainty about the condition of the reactor internals. However, there are issues
to be addressed in developing a method to reduce the volume of secondary waste (abrasives, etc.) generated from theaccess route establishment, and a method to suppress radioactive dust dispersion during the work. Due to the change
in the spent fuel removal method for Unit 2, further engineering work will be needed to verify how the side accessinvestigation method can actually be applied on-site.
Therefore, in order to improve the applicability of the top access investigation method with actual equipment, thisproject aims to develop a new method of opening the reactor internals (steam dryer, steam separator, shroud head,etc.) for establishment of an access route into the shroud, and aims to develop a processing technology that generates
less secondary waste (abrasives, etc.) and radioactive dust dispersion by cutting inside the RPV, compared to theconventional abrasive water jet (AWJ) method.
⇒ (1) Upgrading of processing technology for the top access investigation method
It is also important to develop a method that may enable earlier investigation inside the RPV, since substantial time isneeded before the top and side access investigation methods can be applied on-site. The access route establishment
work for the detailed investigation inside the PCV is underway.
Therefore, in this project, investigation equipment will be installed in the pedestal interior using the access route thathas already been established to proceed with the project of Development of Technology for Detailed Investigation
inside the PCV and the project of Development of Technology for Gradually Increase of Retrieval Scale of Fuel Debris.
Investigation equipment will be inserted into an opening at the bottom of the RPV; the conceptual study of the bottom
access and suitable investigation equipment to investigate inside the RPV will be conducted.
⇒(2) Development of the bottom access investigation method©International Research Institute for Nuclear Decommissioning2. Goals
TRL(Technology readiness)
7(1) Upgrading of processing technology for the top
access investigation method⇒ Regarding the top investigation method, for establishing anaccess route into the shroud, the feasibility of a processing
technology that produces less secondary waste from cutting
than the conventional abrasive waterjet method should beverified.

FY2024-25 target for application toactual equipment

6

5

4

(2) Development of the bottom accessinvestigation method⇒ An investigation and development plan forthe bottom access investigation should beformulated and engineering should proceed
based on the element technology
development that constitutes methods. For
the access method into the pedestal
developed in “Development of Technology for
Detailed Investigation inside the PrimaryContainment Vessel,” the conceptual study of
RPV interior access equipment andinvestigation equipment inside the RPVshould be explored, as well as for several
other methods depending on-site conditions.

3

2

1

No.4

Achieving the technology readiness level (TRL) for investigation
method by making openings developed by FY20192

On-siteconditions

7
Applying for
permission andauthorization

Status ofthe site

On-siteinvestigation

6
Training andrehearsal
Equipment
manufacturing for
actual equipment
investigation

5

Partial mockup test

4

3

Basic design

Conceptual
designStudy of equipment
specifications

Element test

Element test

Partial mockup test
equipment
manufacturing

Detailed equipment
design based on
status of the site

1
Applicability
study©International Research Institute for Nuclear Decommissioning3. Implementation items, their co-relation and relation to other projects
Development of Technology
for Detailed Investigation
inside PCVDevelopment ofTechnology for Gradually
Increasing Retrieval Scaleof Fuel Debris

Study of fuel debris
retrieval method andequipment
Study of criticality control【input】- Access equipment specifications- Various constraints
Detailed design,
equipment manufacturing,
Development of Technology
mockup, etc.

for Investigation inside the
RPVThis project

No.5【output】- Information on the RPV interior andaccess route (visual information,
radiation dose rate, etc.)

Actualequipment
investigation- Top access investigation- Bottom access investigation【input】- Investigation results of the upper part ofthe pedestal (RPV bottom) (location of
openings, condition of structures, etc.)

Development ofTechnology for Detailed
Investigation inside PCV©International Research Institute for Nuclear Decommissioning4. Implementation schedule
Implementation items(1) Upgrading of processing
technology for the top accessinvestigation method① Investigation and evaluation ofpotential alternative processing
technologies

No.6

FY2020

FY2021

Organization of investigation items/parameters
Simplified test

Comparative evaluation
Study of development plan

② Planning of development forpotential alternative processing
technologies

Basic design③ Element tests of potential
alternative processing technologies,
feasibility verification(2) Development of the bottom
access investigation method① Planning of top
access/investigation anddevelopment plan foraccess/investigation equipment② Conceptual study of bottom
access/investigation equipment

Selection of alternative
processing technology
candidates

Planning of outline specifications
for potential alternative
processing technologies

Element test
Evaluation
Results of study ofcandidate technologies

Drafting of investigation plan
Feasibility study (test)

Investigation andDevelopment
Planning

Feasibility evaluation

Conceptual design

Planning of
methodElement test
Evaluation©International Research Institute for Nuclear Decommissioning5. Project organization

No.7

This project aims to develop technology for investigation inside the RPV. The interface with each development project teamis of utmost importance. Therefore, IRID Head Office, Toshiba Energy Systems & Solutions Corporation (Toshiba ESS), andHitachi-GE Nuclear Energy (Hitachi-GE) are working together to develop a safe, reliable, logical, rapid, and site-oriented fueldebris retrieval technology for the Fukushima Daiichi, through mutual technological cooperation among IRID Japanese plantcomponent manufacturers, in order to analyze the on-site situation and to develop a series of measures that are consistent withthe fuel debris retrieval plan, etc.
International Research Institute for Nuclear
Decommissioning (IRID) (Head Office)〇 Overall planning and technological supervision〇 Technological management of technology development
progress, etc.

Toshiba Energy Systems & Solutions
Corporation(2) Development of the bottom accessinvestigation method① Planning of top access/investigation anddevelopment plan for access/investigationequipment② Conceptual study of bottom
access/investigation equipment

Hitachi-GE Nuclear Energy, Ltd.
(1) Upgrading of processing technology for the top
access investigation method① Investigation and evaluation of potential
alternative processing technologies② Planning of development for potential
alternative processing technologies③ Element tests of potential alternative
processing technologies, feasibility verification(2) Development of the bottom access investigation
method
① Planning of top access/investigation anddevelopment plan for access/investigationequipment② Conceptual study of bottom
access/investigation equipment

Tokyo Electric Power Company Holdings, Inc.
〇 Adjustments for on-site applicability

Partner development project teams

Development of Technology for Gradually
Increasing Retrieval Scale of Fuel Debris

Development of Technology for Detailed
Investigation inside PCV

Sugino Machine Limited-(1) Structural design for upgrading ofprocessing technology for the top
access investigation method
Hitachi Plant Construction, Ltd.
-(1) Technological investigation for
upgrading of processing technology
for the top access investigation
method©International Research Institute for Nuclear Decommissioning6. Implementation details

No.8(1) Upgrading of processing technology for the top access investigation method<Summary of implementation in the second half of FY2021>
Using the nozzle designed in the first half of the fiscal year, element test plans for AWJ (Abrasive Water Jet)cutting and laser cutting were drafted, and the tests were conducted.
<Details of implementation in the second half of FY2021>

Processing
technology
AWJ/
Laser

Details of implementation①

Element test plan②

Conducting of element tests③

Design of actual equipment<Results>
AWJ

Laser

- Although the effect of increasing flow rate by approximately twice the conventional level were notverified, the abrasive feed rate with good cutting performance was verified (for purposes of reducing
abrasive consumption), and the rate was revised from the conventional 500 g/min to 100 g/min.
- The operational conditions for each cutting site were verified at an abrasive feed rate of 100 g/min,and the prospects of achieving the target abrasive consumption of 500 kg or less (presented in
the solicitation information) were found.
- In FY2020, the nozzle was only applied to vertical cutting of the steam separator, but a new nozzle forhorizontal cutting was designed, and prospects of applying the horizontal cutting were found.
- Based on those results, prospects for applying the laser cutting process to all of the reactor
internals required for the top access were found, and the operational conditions for each target
cutting site were verified by testing.

©International Research Institute for Nuclear Decommissioning6. Implementation details

No.9(1) Upgrading of processing technology for the top access investigation method

1) Summary of results through the first half of FY2021 (1/4)
After investigating pressure and flow rate increases for AWJ (Abrasive Water Jet) cutting, it was determined that pressure increase isunacceptable. Flow rate increase is feasible, and the AWJ nozzle design that can handle a higher flow rate and the system design weredevised. For laser cutting, a small nozzle was designed for horizontal cutting application.
Implementation details and results
1. Organization of implementation details for FY2021- Implementation details were organized for AWJ and laser cutting. For AWJ cutting, the pressure and flow rate increase were studied and anozzle was designed based on those results, and verification of cutting performance through element tests was conducted.

Table 1 Flow of FY2021 implementation items (AWJ)
MethodTargetsites
AWJ

FY2021 implementation policy

FY2020 test results
Step 1
Theoretical study (test portion
available)

Step 2

Test details/results

Other thantheseparator
body

-

-

-

Separator
body

Adoption of a small
nozzleStep 3

Step 4
Study of actual
equipment applicability

Test

Design for equipment in
the actual use

Element test
① Verification of cutting thepartial mock-up② Planning of optimal
operational conditions
when applying to actual
equipment(1)

Study of pressure andflow rate increase

Downsizing of nozzle makes it ① Study of feasibility of pressure andpossible to approach theflow rate increase
cutting target.
(Shorter standoff improves
cutting efficiency)
Significant reduction involume of abrasives(from 8 tons to 0.33 tons)(2) Pressure, flow rate
- Pressure: 343 MPa- Flow rate: 3.7 liter/min

Nozzle design① Nozzle design for increased flowrate(3) Abrasive feed rate
- Feed rate: 500 g/min

Implementation details for the first half of the fiscal year

Basic test of flow rateincrease① Verification of cutting
performance under thecondition of Increasing theflow rate② Verification of the appropriate
value of the abrasive under
the condition of increased
flow rate① Design equipment in theactual use based on element
test results

Element test
① Verification of cutting thepartial mock-up② Planning of optimal
operational conditions
when applying to actual
equipment

Nozzle durability test
① Evaluation of the nozzle
lifetime by durability testingunder the operational
conditions verified by theelement test

③ Comparison of performancewith the nozzle used in
FY2020④ Measurement of theprocessing reaction force
under the condition ofincreased flow rate

©International Research Institute for Nuclear Decommissioning6. Implementation details

No.10(1) Upgrading of processing technology for the top access investigation method

1) Summary of results through the first half of FY2021 (2/4)
Implementation details and results
1. Organization of implementation details for FY2021
For laser cutting, a nozzle suitable for horizontal cutting was designed, and the cutting performance was verified through element tests.

Table 2 Flow of FY2021 implementation items (laser)
MethodFY2020 test results
Target sites

Test details/results

FY2021 implementation policy
Step 1

Step 2

Theoretical study (test portion
available)
Laser

Other thantheseparator
body-

Separator
body

Adoption of laser cutting(1) Vertical cutting is available.
(2) The nozzle was too large to
be inserted between thethree separator tubes, so it
was not adopted forhorizontal cutting.

--Nozzle design① The downsized nozzle designthat is suitable for horizontal
cutting (including sampling test)

Step 3

Study of actual equipment
applicability

Test-

Basic test of a small
nozzle①Test of small nozzle cutting
performance

Step 4

Element test

Design for equipment in
the actual use① Verification of cutting the ① Design equipment in thepartial mock-up
actual use based on② Planning of optimal
element test results
operational conditions
when applying to actual ② Planning of investigationequipment
into countermeasures toproject issues
Element test
(implementation details ofnext phase)① Verification of cutting

the partial mock-up② Planning of optimal
operational conditions
when applying to actual
equipment

Identification of issues inapplication to actual equipment① Identification of issues inapplication to actual
equipment and study ofcountermeasures

Implementation details for the first half of the fiscal year

©International Research Institute for Nuclear Decommissioning6. Implementation details

No.11(1) Upgrading of processing technology for the top access investigation method

1) Summary of results through the first half of FY2021 (3/4)
Implementation details and results
2. AWJ (Abrasive Water Jet) nozzle (angle nozzle) design- Nozzle design considerations were identified, and the results of the study were applied to the nozzle design.
No.

Study details

Study results

1

Pressure increase- In FY2020, a simplified test at a pressure of 343 Mpa wasconducted, so the pressure will be increased (to about twice
the target) to improve the cutting efficiency and reduce theamount of abrasive consumption.

Deemed not applicable-When increasing the pressure to 400 MPa or higher, it isnecessary to switch from a high-pressure hose to a steel pipe.
Since it is difficult to incorporate a steel pipe into the equipment,
additional pressure increase was deemed not feasible.

2

Flow rate increase- In FY2020, a simplified test was conducted at a flow rateof 3.7 liter/min, so the flow rate will be increased (to about
twice the target) to improve the cutting efficiency and reduce
the amount of abrasive consumption.

Deemed applicable and the flow path design implemented-Since it was possible to increase the flow rate without changing
the hose diameter, a nozzle and system were designed to handle
about twice the FY2020 flow rate.

3

Downsizing of nozzle- In FY2020, a test was conducted by using a nozzle ofnominal dimensions such that can be inserted into thespace between the three steam separator tubes.
- It is necessary to consider accessibility to the steam
separator.

Downsizing of nozzle is possible- The nozzle size (Φ64 mm) was chosen for ease of access to thesteam separator.

Φ64 mmAWJ nozzle

AWJ nozzle
Front view
Side view
AWJ Nozzle (angle nozzle)©International Research Institute for Nuclear Decommissioning6. Implementation details

No.12(1) Upgrading of processing technology for the top access investigation method

1) Summary of results through the first half of FY2021 (4/4)
Implementation details and results
3. Laser nozzle (angled nozzle) design- Issues pertaining to horizontal cutting were identified and appropriate countermeasures were applied to the nozzle design.
No.

Issues of horizontal cutting

Countermeasures

1

Damage to mirror section-Since cutting is performed in the space between
the three steam separator tubes, there is only ashort distance to the cutting target. Therefore thefocal point and the mirror are close to each other, so
the energy density of the laser beam on the mirror ishigh, resulting in a risk of mirror damage.

Additional mirror cooling- In order to suppress mirror temperature increase, awater cooling structure was added.

2

Decreased cutting capacity-Since horizontal cutting has a large standoff
fluctuation range, cutting may not be possible if the
distance from the focal point to the cutting target is
too great.
(Distance from focal point to cutting target: amaximum of 30 mm)

Preliminary confirmation test
-In designing the nozzle, a preliminary confirmation test
was conducted to confirm whether cutting was possible ata greater distance from the focal point to the cutting
target. By confirming that cutting is possible even at a
distance of up to 80 mm from the focal point, it was
concluded that standoff fluctuations are manageable.

Focal point
Auxiliary gas nozzle
Auxiliary gas path

MirrorSmall nozzle

Laser nozzle (angled nozzle)

Φ70 mm or less

Safety glass

Mirror coolingsystem©International Research Institute for Nuclear Decommissioning6. Implementation details

No.13(1) Upgrading of processing technology for the top
access investigation method
2) Implementation details for the second half of FY2021① Test plan (AWJ: Abrasive Water Jet)
The flat plate cutting test and the mockup cutting
test shown in the table below are conducted toconfirm cutting performance.
Test
Category

Straight nozzle
Straight nozzle

Straight nozzle

Steam dryer bottom plate

Test item

Test to verify the effect of flowrate increase
Flat plate (including processing reaction
cutting force measurement)
test

Test to verify the suitable value
for abrasive feed rate

Steam separator connecting rod

Steam separator rib

Purpose
Straight nozzle- Verification of cutting
performance(Performance comparison
between the FY2020 and theimproved FY2021 angle nozzles
included)- Verification of processing
reaction force under the conditionof increased flow rate

Angle nozzle- Verification of the suitableabrasive feed rate

Cutting test on steam dryer
bottom plate
Cutting test on steam separator
connecting rod
Mockupcutting
test

Cutting test on steam separator
rib
Cutting test on steam separator
upper surface

Steam separator upper surface- Verification of conditions underwhich operation is possible- Identification of operation-related
issuesCutting test on steam separator
main body

Entire steam separator

Straight nozzle
Angle nozzle

Cutting test on the shroud head*:
- Straight nozzle: A nozzle that emits a straight stream without bending the flow of high-pressure water (conventional nozzle prior to FY2019)- Angle nozzle: A nozzle that bends the flow of high-pressure water and emits at a right angle (first applied in FY2020, design improved in FY2021)

Shroud head
Steam separator main body©International Research Institute for Nuclear Decommissioning6. Implementation details

No.14(1) Upgrading of processing technology for the top access investigation method
2) Implementation details for the second half of FY2021① Test plan (AWJ (Abrasive Water Jet))
The test pieces for each treatment target were used for simulations of cutting range and the area that would be
obstructed during cutting. Each simulated range is shown in the table below.
Processing objects
Steam dryer

Shape of test pieces (simulation range)

AWJ cutting conditions

Bottom plate
Side plate

Steam separator
Connection bars
Steam separator

Rib

Connection
bars

Upper surface

Main body-

Rib
Steam separator
NozzleNozzleNozzleShroud head

Area subjected for
cutting

Area subjected for cutting
NozzleArea subjected for cutting
NozzleNozzleArea subjected Bottom platefor cutting

Area subjected Steam separator
for cutting
upper surface
Steam separator
Steam separator

Area subjected for cutting

Connection bars

Steam separator
upper surface

Shroud head
Steam separator main body
Steam separator

Steam separator main body
Ring

Rib

Outer tube
Middle tube
Inner tube

Side plate
SpacerShroud head
- Shroud head (thickness):
Actual equipment 50.8 mm →Test piece 50 mm

Bottom plate- Bottom plate (thickness):
Actual equipment 12.7 mm
Test piece 13 mm- Side plate (thickness):
Actual equipment 6.4 mm
Test piece 8 mm

- Connecting rod (width x height):
Actual equipment 6.4 mm × 12.7 mm
Test piece 8 mm × 12.7 mm- Rib (width x thickness):
Actual equipment 5 mm x 28.1 mm (1F-4 information)
Test piece 5 mm × 28.1 mm- Upper surface (thickness): Actual equipment 6.4 mm →Test piece 8 mm

The actual shroud head isspherical, but in this case, a flat
plate was used to simulate a- Outer tube (thickness): Actual equipment 3.2
spherical shape.
mm → Test piece 3 mm
It was concluded that there was no- Middle tube (thickness): Actual equipment 3.2
problem using a flat plate in the
mm → Test piece 3 mm
simulation due to the lack of a
- Inner tube (thickness): Actual equipment 6.35
significant difference in standoff
mm → Test piece 6 mm
and emission angle.
- Spacer (thickness): Actual equipment 3.2 mm- Stand-off: Actual equipment <Test piece (0.33 mm)→ Test piece 3 mm-forEmission
Actual- Ring (thickness):
Actual equipment
12 mm→©International
Research
Institute
Nuclearangle:
Decommissioning
equipment > Test piece (0.97°)
Test piece 12 mm

6. Implementation details(1) Upgrading of processing technology for the top
access investigation method
2) Implementation details for the second half of FY2021② Test plan (laser)
The flat plate cutting test and the mockup cutting
test shown in the table below areconducted toconfirm cutting performance.

Test
Category

No.15
Straight nozzle
Straight nozzle
Straight nozzle

Steam separator connecting rod
Steam dryer bottom plate

Test item

Steam separator rib

Goal

Straight nozzle

Flat plate
cutting
test

Small nozzle cutting test

- Performance verification of asmall nozzle

Cutting test with low laser power
output- Verification of cutting
performance for each laser
power output

Cutting test on steam dryer bottom
plate
Angle nozzle

Cutting test on steam separator
connecting rod
MockupCutting
test

Cutting test on steam separator rib
Cutting test on steam separator
upper surface- Verification of conditions underwhich operation is possible- Identification of operationrelated issues

Cutting test on steam separator
main body
Cutting test on the shroud head

Steam separator upper surface

Entire steam separator

Angle nozzle

Straight
nozzle*:- Straight nozzle: A nozzle that irradiates a straight stream without bending laser beams- Angle nozzle: A nozzle that bends the laser beam and irradiates it at a right angle (designed in FY2021)
Shroud head

Steam separator main body©International Research Institute for Nuclear Decommissioning6. Implementation details

No.16(1) Upgrading of processing technology for the top access investigation method
2) Implementation details for the second half of FY2021② Test plan (laser)
The test pieces for each treatment target were used for simulations of cutting range and the area that would be
obstructed during cutting. Each simulated range is shown in the table below.
Processing objects
Steam dryer

Steam separator

Laser cutting conditions

Bottom plate

Connection bars

Steam
Side plate separator

Upper surface

Main bodybars

Steam separator
Area
subjected for
cuttingNozzleNozzleNozzleArea subjected for cutting
Steamseparator

Area
subjected
for cutting

Steam separator uppersurface

Area subjected for cutting
Steam separator main body
Steam separator main body

Steam separator
upper surface

Ring

Rib

Side plate

Area subjected
for cutting

NozzleNozzleArea subjected Bottom platefor cutting-

RibNozzle Connection

Steam separator

Shape of test pieces (simulation range)

Rib

Shroud head

Connection bars

Shroud head
Steam separator

Outer tube
Middle tube
Inner tube

SpacerShroud head
Bottom plate- Bottom plate (thickness):
Actual equipment 12.7 mm
Test piece 13 mm- Side plate (thickness):
Actual equipment 6.4 mm
Test piece 8 mm

- Connecting rod (width x height):
Actual equipment 6.4 mm × 12.7 mm
Test piece 8 mm × 12.7 mm- Shroud head (thickness):
Actual equipment 50.8 mm →Test piece 50 mm- Rib (width x thickness):
Actual equipment 5 mm x 28.1 mm (1F-4 information)
Test piece 5 mm × 28.1 mm- Upper surface (thickness): Actual equipment 6.4 mm →Test piece 8 mm

The actual shroud head isspherical, but in this case, a flat
plate was used to simulate a- Outer tube (thickness): Actual equipment 3.2
spherical shape.
mm → Test piece 3 mm
It was concluded that there was no- Middle tube (thickness): Actual equipment 3.2
problem using a flat plate in the
mm → Test piece 3 mm
simulation due to the lack of a
- Inner tube (thickness): Actual equipment 6.35
significant difference in standoff
and emission angle.
mm → Test piece 6 mm
- Stand-off: Actual equipment <- Spacer (thickness): Actual equipment 3.2 mm
Test piece (0.33 mm)→ Test piece 3 mm
- Emission angle: Actual- Ring (thickness): Actual equipment 12 mm →equipment
Test piece (0.97°)©International
Research
InstituteforNuclear>Decommissioning
Test piece 12 mm

6. Implementation details

No.17(1) Upgrading of processing technology for the top access investigation method

2) Implementation details for the second half of FY2021③ Test results (AWJ: Abrasive Water Jet) [flat plate cutting test (1/4)]- Test to verify the effect of flow rate increase (without<Test results>
supply of abrasives)
Standoff: 20 mm<Test details>
The flat plate was cut by moving the nozzle in the
direction of the flat plate edge in the condition that
the AWJ flow rate is increased to 8.4 liter/min. The
effect of the increased flow rate was verified from thecutting length.

<Test conditions>

Abrasive feed
Nozzle speed
rate(mm/min)(g/min)0.5

0Flow rate: 8.4
liter/minCutting
depth
No.
(mm)

3

1

Flow rate: 3.7liter/min*Cutting
depth
No.
(mm)

2

3

4
0.2 2
4
2
*: The flow rate result of 3.7 liter/min is from the FY2020 test results.

Feed direction Stroke: 15 mm
Test No.

AWJ nozzle

1

3

4

Emission angle 90°

20 mm

Cutting marks

Cutting depth
Flat-plate test piece
Plate thickness: 3 mm

Items

2

Photo of test piece (flow rate 8.4 liter/min)Photo of test piece (flow rate 3.7 liter/min)<Conclusion>
Conditions

AWJ nozzle

Angle nozzle

Injection pressure

343 MPa

Injection flow rate

8.4 liter/min

Abrasive feed rate

0 (water jet (WJ) cutting)- Compared to the result of 3.7 liter/min from the FY2020 test, themaximum cutting depth was doubled.
Therefore, water jet (WJ) cutting verified the effect of high flow rate.
- Although cutting effect was obtained, cutting performance was low, andas in FY2020, the WJ cutting is not applicable to actual equipment.

©International Research Institute for Nuclear Decommissioning6. Implementation details

No.18(1) Upgrading of processing technology for the top access investigation method
2) Implementation details for the second half of FY2021③ Test results (AWJ: Abrasive Water Jet) [flat plate cutting test <Test results>(2/4)]- Test to verify the effect of flow rate increase (AWJ)
Cutting speed

Abrasive feed rate: 500 g/min
Standoff: 20 mm
Flow rate: 8.4 liter/min
Flow rate: 3.7 liter/min*
No. Cutting depth (mm) No. Cutting depth (mm)(mm/min)<Test details>
The flat plate was cut by moving the nozzle in the directionof the flat plate edge in the condition that the AWJ flowrate is increased to 8.4 liter/min. The effect of theincreased flow rate was verified from the cutting depth.

100
80
60
40

1
2
3
4

11
12
16
26

5
6
7
8

12
14
16
27

*: The flow rate result of 3.7 liter/min is referred from the FY2020 test results.

<Test conditions>Feed direction Stroke: 15 mm

20 mm

AWJ nozzle

Test No.

1

2

3

8

4

7

6

5

Emission angle 90°

Cutting marks

Cutting depth
Flat-plate test piece
Plate thickness: 3 mm

Items

Photo of test piece (flow rate 8.4 liter/min)Photo of test piece (flow rate 3.7 liter/min)<Conclusion>
Conditions

AWJ nozzle

Angle nozzle

Injection pressure

343 MPa

Injection flow rate

8.4 liter/min

Abrasive feed rate

500 g/min- Compared to the result of 3.7 liter/min from the FY2020 test, theeffect of an improvement in cutting efficiency through increasing
the flow rate was not verified with an abrasive feed rate of 500
g/min.
- However, depending on the abrasive feed rate, it may be possible toverify the effect of increasing the flow rate, so a test was conducted toverify the suitable abrasive feed rate.
©International Research Institute for Nuclear Decommissioning6. Implementation details

No.19(1) Upgrading of processing technology for the top access investigation method
2) Implementation details for the second half of FY2021③ Test results (AWJ: Abrasive Water Jet) [flat plate cutting test (3/4)]- Test to verify the effect of flow rate and abrasive feed rate (1/2)<Test details>
The abrasive feed rate was varied under conditions of AWJ flow rates of either 8.4 liter/min or theconventional 3.3 liter/min. The flat plate was cut by moving the nozzle in the direction of the flat plateedge and the relationship between flow rate and abrasive feed rate were verified from the cutting depth.
<Test conditions><Test results>
A table of the test results is provided on the next page.

Feed direction Stroke: 15 mm

20 mm

AWJ nozzle

Test No.
2

×

1

3

4

5

6

7

8

9

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

Emission angle 90°
Cutting marks

Cutting depth
Flat-plate test piece
Plate thickness: 10 mm

Items

10

11

12

13

14

15

16

17

18

Conditions

AWJ nozzle

Angle nozzle

Injection pressure

343 MPa

Injection flow rate

8.4, 3.3 liter/min

Abrasive feed rate

100 to 900 g/min

Phot of test piece (standoff: 20 mm)

Photo of test piece (standoff: 50 mm)©International Research Institute for Nuclear Decommissioning6. Implementation details

No.20(1) Upgrading of processing technology for the top access investigation method
2) Implementation details for the second half of FY2021③ Test results (AWJ: Abrasive Water Jet) [flat plate cutting test (4/4)]- Test to verify the effect of flow rate and abrasive feed rate (2/2)<Test results>

Cutting speed
B (mm/min)
AWJ nozzle

Abrasive
feed rate
A (g/min)Cutting depth
D (mm)

Standoff: 20 mm
Standoff: 50 mm
Abrasive
Flow rate: 8.4 liter/min
Flow rate: 3.3 liter/min
Flow rate: 8.4 liter/min
Flow rate: 3.3 liter/min
Abrasive
supplySpeed
Cutting
Cutting
Cutting
Cuttingfeed rate
rate
Cutting
Cutting
Cutting
Cutting(mm/min)efficiency
efficiency
efficiency
efficiency(g/min)(g/mm) No. depth
No. depth
No. depth
No. depth(mm2/g)(mm2/g)(mm2/g)(mm2/g)
*1
(mm)
(mm)
(mm)
(mm)
<Abrasive supply
*2
*2
*2
*2
rate>
- When the nozzle
900
15.0 123
1.53 1019
1.27 119
1.27 1019
1.27
advances 1 mm
Amount of abrasive to800
13.3 227
2.03 1118
1.35 218
1.35 1118
1.35
be used- A÷B＝C (g/mm）
Thickness
3
12
3
12
700
11.7
20
1.71
17
1.46
17
1.46
17
1.46 of flat plate600
10.0 419
1.90 1316
1.60 415
1.50 1317
1.70 test piece:<Cutting efficiency>- Area that can be cut
5
14
5
14
500
60
8.3
16
1.92
15
1.80
14
1.68
16
1.92 10 mmwith 1 g of abrasive- D÷C＝E (mm /g）
400
6.7 6
14
2.10 15
14
2.10 610
1.50 15
13
1.95
300
5.0 7
12
2.40 16
11
2.20 78
1.60 16
11
2.20
200
3.3 8
8
2.40 1792.70 85
1.50 178
2.40 Fig. 1 Regarding cutting efficiency
100
1.7 9
6
3.60 18
7
4.20 942.40 18
4
2.40*1: Abrasive supply rate (g/mm) is the value obtained by dividing the abrasive feed rate (g/min) by the cutting speed (mm/min).
*2: Cutting efficiency is the value (mm 2/g) obtained by dividing the cutting depth (mm) by the abrasive supply rate (g/mm) (refers to the area that can be cut per 1 g ofabrasive when moving 1 mm in the feed direction (See Fig. 1)).
2

<Conclusion>- It was verified that the cutting efficiency is satisfactory with an abrasive feed rate of 100 g/min under both conditions of flowrate 8.4 liter/min and 3.3 liter/min (red frame in the table).
- In comparing flow rates of 8.4 liter/min and 3.3 liter/min at 20 mm standoff, 500 g/min or higher abrasive feed rate, the flow rate of
8.4 liter/min resulted in higher cutting efficiency (blue frame in the table). There were no other differences between the two flow rates
but 3.3 liter/min gave better results.

- It was verified that increasing the flow rate was effective under some conditions but had only a small effect inother cases.
- Focused on reducing the amount of abrasive consumption, the cutting efficiency of 3.3 liter/min and 100 g/min
was satisfactory, and these parameters were adopted in the mockup cutting test.
©International Research Institute for Nuclear Decommissioning6. Implementation details

No.21(1) Upgrading of processing technology for the top access investigation method
2) Implementation details for the second half of FY2021③ Test results (AWJ: Abrasive Water Jet) [Mockup cutting test (1/9)]- Summary of operational conditions for each treatment target
The table below shows the operational conditions for each treatment target verified in the mockup cutting test.
Processing objects
Steam dryer

Steam separator
Connection bars

Side plate

Steam separator

Rib

Upper surface

Steam separator

Area
subjected
for cutting

NozzleNozzleMain body

Rib

Connection bars

NozzleArea
subjected for
cuttingNozzleArea
subjected
for cutting

NozzleNozzleArea subjected
for cutting

Bottom plate

Area subjected for cutting

Area subjected
for cutting
Steam separator upper surface
Steam separator- Straight nozzle+- Angle nozzle- Straight nozzle

Injection pressure: 343 MPa, Abrasive feed rate: 100 g/min
Injection flow rate: 3.45 liter/min (straight nozzle) / 3.3 liter/min (angle nozzle)- Straight nozzle- Straight nozzle

Shroud head
Steam separator main body

- Upper flat plate- Vertical cutting
cutting: 10 to 30 mm/min: 30°/min - Horizontal cutting- Vertical cutting: 12°/min: 10 to 15 mm/min- Horizontal cutting: 12°/minNozzletype- Small diameter- Connecting rod cutting - Upper rib cutting
machining: 10°/min: 5°/min- Lower rib cutting: 50°/min- Large diameter: 10°/minmachining: 3 to 10°/min

Commonconditions

Cutting speed

AWJ cutting conditions

Bottom plate

Shroud head

- Angle nozzle- Drilling of central
hole: 60°/min- Circumferential
cutting: 6°/min- Straight nozzle©International Research Institute for Nuclear Decommissioning6. Implementation details

No.22(1) Upgrading of processing technology for the top access investigation method
2) Implementation details for the second half of FY2021③ Test results (AWJ: Abrasive Water Jet) [mockup cutting test (2/9)]- Steam separator: cutting of main body (1/7)<Test details>
The conditions for cutting the main structure of the steam separator with an abrasive feed rate of 100
g/min were verified.

<Cutting procedure (actual equipment assumed)>
Middle tube
Outer tube

Shape before treatment① Vertical cutting (interior)Spacer② Vertical cutting (exterior)③ Vertical cutting (spacer)

Cutting height for 1 round(50 mm)Ring

Repeat steps 1 to 4
until the specified
number of rounds④ Horizontal cutting

Shape after treatment (1 round): Range added in FY2021, notsimulated until FY2020.

⑤ Vertical cutting (ring)©International Research Institute for Nuclear Decommissioning6. Implementation details

No.23(1) Upgrading of processing technology for the top access investigation method
2) Implementation details for the second half of FY2021③ Test results (AWJ: Abrasive Water Jet) [mockup cutting test (3/9)]- Steam separator: cutting of main body (2/7)<Test results><Test conditions>- Vertical cutting (interior) was possible for cutting theouter and middle tubes at 20 mm/min.

① Vertical cutting (interior)
Outer tube Middle tube

Cutting line ①
Inner tube②

(Turning radius of nozzle tip)

Nozzle running⑤③④
Outer tube

Inner
tube

Outer tube
Inner tube

Outer tube

Drawing of cutting conditions
Items

Conditions

AWJ nozzle

Angle nozzle

Injection pressure

343 MPa

Injection flow rate

3.3 liter/min

Abrasive feed rate

100 g/minStandoff

16.3 mm (until the outer tube)
47.5 mm (until the middle tube)

Cutting speed

Middle tube

Cutting line ③

Inner tube

Cutting line ②

Photo of test piece: vertical cutting (interior)

20 mm/min©International Research Institute for Nuclear Decommissioning6. Implementation details

No.24(1) Upgrading of processing technology for the top access investigation method
2) Implementation details for the second half of FY2021③ Test results (AWJ: Abrasive Water Jet) [mockup cutting test (4/9)]- Steam separator: cutting of main body (3/7)<Test conditions><Test results>② Vertical cutting (exterior)- Vertical cutting (exterior) was possible for cutting the outertube at 10 mm/min.

Outer tube Middle tube②③

Inner tube
(Turning radius of nozzle tip)

Cutting line ①
Nozzle running⑥④⑤
Outer tube
Outer tube
Inner tube

Inner
tube

Outer tube

Drawing of cutting conditions
Items

Conditions

AWJ nozzle

Angle nozzle

Injection pressure

343 MPa

Injection flow rate

3.3 liter/min

Abrasive feed rate

100 g/minStandoff

41.9 mm

Cutting speed

10 mm/minMiddle tube

Cutting line ④
Inner tube

Cutting line ③

Photo of test piece: vertical cutting (exterior)©International Research Institute for Nuclear Decommissioning6. Implementation details

No.25(1) Upgrading of processing technology for the top access investigation method
2) Implementation details for the second half of FY2021③ Test results (AWJ: Abrasive Water Jet) [mockup cutting test (5/9)]- Steam separator: cutting of main body (4/7) <Test results><Test conditions>- For vertical cutting (spacers), the cutting of each spacer was
possible at the following cutting speeds.

③ Vertical cutting (spacer)[Cutting speed] Spacer 1: 30 mm/min (one round trip), spacer 2: 20 mm/min
Spacer 3: 20 mm/min, spacer 4: 20 mm/min

Outer tube Middle tube

Spacer 2

Spacer 2

Spacer 2②
Cutting line ①

Cutting line ②

Spacer 1

Inner tube

Spacer 1(Turning radius of nozzle tip)

Spacer 3

Spacer 1

Spacer 3

Nozzle running

Inner tube③

Middle tube④
Spacer 4

Outer tube

Spacer 4

Inner
tube

Cutting line ①

Outer tube
Inner tube

Outer tube

Drawing of cutting conditions
Items

Conditions

AWJ nozzle

Angle nozzle

Injection pressure

343 MPa

Inner tube

Cutting line ④
Middle tube

Injection flow rate

3.3 liter/min

Abrasive feed rate

100 g/minStandoff①: 31.1 mm (until the spacer)②③: 52.6 mm (until the spacer)④: 49.5 mm (until the spacer)

Cutting speed①: 30 mm/min (one round trip)②③④: 20 mm/min

Spacer 4

Spacer 3

Outer tube

Middle tube

Outer tube

Cutting line ③
Inner tube

Photo of test piece: vertical cutting (spacer)©International Research Institute for Nuclear Decommissioning6. Implementation details

No.26(1) Upgrading of processing technology for the top access investigation method
2) Implementation details for the second half of FY2021③ Test results (AWJ: Abrasive Water Jet) [mockup cutting test (6/9)]- Steam separator: cutting of main body (5/7)<Test results><Test conditions>- Horizontal cutting was possible for cutting the outer andmiddle tubes and spacers at 12°/min.

④ Horizontal cutting

SpacerCutting line ①
Nozzle rotation(114°×3)(Turning radius of nozzle tip)②③
Outer tube

SpacerInner
tube

Outer tube Inner
tube

Drawing of cutting conditions
Items

Conditions

AWJ nozzle

Angle nozzle

Injection pressure

343 MPa

Injection flow rate

3.3 liter/min

Abrasive feed rate

100 g/minStandoff

4 mm to 58 mm

Cutting speed

12°/minCutting line ②

Inner tube Middle tube

Outer tube

Photo of test piece: horizontal cutting©International Research Institute for Nuclear Decommissioning6. Implementation details

No.27(1) Upgrading of processing technology for the top access investigation method
2) Implementation details for the second half of FY2021③ Test results (AWJ: Abrasive Water Jet) [mockup cutting test (7/9)]- Steam separator: cutting of main body (6/7)<Test results><Test conditions>- Vertical cutting (ring) was possible for cutting the ring at
30 mm/min (9 round trips).

⑤ Vertical cutting (ring)②
Spacer③
Cutting line ①

Ring

Nozzle running⑥④⑤

SpacerOuter tube

Outer tube
Inner tube

Inner
tube

Ring

Drawing of cutting conditions

Items

Conditions

AWJ nozzle

Angle nozzle

Injection pressure

343 MPa

Injection flow rate

3.3 liter/min

Abrasive feed rate

100 g/minStandoff

53.5 mm (until ring)

Cutting speed

30 mm/min (9 round trips)

Cutting line ②

Photo of test piece: vertical cutting (ring)©International Research Institute for Nuclear Decommissioning6. Implementation details

No.28(1) Upgrading of processing technology for the top access investigation method
2) Implementation details for the second half of FY2021③ Test results (AWJ: Abrasive Water Jet) [mockup cutting test (8/9)]- Steam separator: cutting of main body (7/7)<Test results>
Orientation for shooting of photo ③
Opening after cutting
AWJ nozzle(Angle nozzle)

Round 1Round 2Round 3Round 4

Photo ① of test pieces before cutting

Photo ② of test pieces after cutting into 4 pieces

Photo ③ of test pieces after cutting inro 4 pieces

According to the cutting procedure described in the previous pages, the main
body of the steam separator was cut into four pieces by using the angle
nozzle designed in FY2021.
©International Research Institute for Nuclear Decommissioning6. Implementation details

No.29(1) Upgrading of processing technology for the top access investigation method
2) Implementation details for the second half of FY2021③ Test results (AWJ: Abrasive Water Jet) [mockup cutting test (9/9)]- Other treatment targets
Connection bars
Side plate

Opening

Rib

Opening

Steamseparator

Opening
Bottom plate

Steam dryer bottom plateSteam
separator

Steam separator connecting rods

Steam
separator

Steam separator ribs

Steam separator upper surface

Steamseparator

Cutting tests for objects to be processed other than the main body ofthe steam separator were carried out by using every nozzle. It wasverified that all reactor internal structures to be processed can be cut.
Opening

Shroud head (front)

Shroud head©International Research Institute for Nuclear Decommissioning6. Implementation details

No.30(1) Upgrading of processing technology for the top access investigation method(*1): An abrasive feed rate of 100 g/min was used for the element test, but due to variations in
the feed rate, 120 g/min was used in the Estimations.
(*2): The evaluations were made conservatively due to instability in the abrasive feed rate inpast tests.
(*3): Targets where operational conditions were verified by new FY2021 simulations.

2) Implementation details for the second half of FY2021③ Test results (AWJ: Abrasive Water Jet)
[Estimation of abrasive consumption]
Processing objects

Steam
dryer

Bottomplate

Changes other than abrasive feed rate

Same as that on
the left

0.88 kg○

No change

12.64 kg

Same as that on
the left

7.35 kg○

No change

60.00 kg (*2)

Same as that on
the left

1.08 kg○- Limited emission range (364°→ 90°)
- Reduced standoff

8.59 kg

Same as that on
the left

1.56 kg○- Change in emission range (17° → upper 20°, lower
25°)- Increase in cutting points (2 points → 4 points)- Upper flat plate cutting- Vertical cutting (interior)- Vertical cutting(exterior)

829.06 kg

Same as that on
the left

17.16 kg○

- Change in cutting combination(Combination of conical cuts → combination ofconical cutting + vertical/horizontal cutting)- Change in emission range (364° → 342°)- Vertical cutting (spacer)
(*3)

―

―

0.17 kg○

No change(New consideration)- Vertical cutting (interior)- Vertical cutting(exterior)- Horizontal cutting

7840.21 kg

323.75 kg

269.82 kg○

No change- Vertical cutting (spacer)- Vertical cutting (ring)
(*3)

―

―

20.12 kg○

No change(New consideration)

Small diameter treatment

―

Rib

―

Main body

Shroudhead

2.74 kg

FY2021
Changes in abrasive feed
rate (yes: ○, no: x)

Connection
bars

Upper
surface

FY2020abrasive
consumption

Abrasive consumption(*1)

Large diameter
treatment
Steamseparator

Abrasive
consumption up to
FY2019-Drilling of central hole

4.5 kgSame as that on
the left

0.97 kg○

No change-

Circumferential cutting

51.57 kg

Same as that on
the left

8.28 kg○

No change

1293 kg

328 kg(Compared to previous
FY: approx. 75%
decrease)

―

―

37 hr

46 hr
(Compared to previous
FY: approx. 25%
increase)

Total(Rounded up to the nearest whole number)

Total operation time
(Rounded up to the nearest whole number)

8810 kg

228 hrAlthough operation time will increase, theprospect of abrasive consumption of 500― less can be achieved.
―
kg or©International Research Institute for Nuclear Decommissioning6. Implementation details

No.31(1) Upgrading of processing technology for the top access investigation method
2) Implementation details for the second half of FY2021③ Test results (AWJ: Abrasive Water Jet) [Results of nozzle durability test]<Test results><Test details>
Flat plate was cut for every hour of emission,and the cutting depth is verified. Nozzle
lifetime was evaluated from changes in
cutting depth.

- The cutting depth decreased slightly after 2 hours, remained
stable after that until the 8th hour, and then gradually decreased
after the 9th hour.
Range that has less cutting
depth than a brand new nozzle(0 hr), but still a consistentcutting depth<Test conditions>

Range of gradualdecrease in cutting
depth

50 mm

AWJ nozzle

Emission angle 90°
Cutting marks

Cutting depth

Cutting depth (mm)Feed direction Stroke: 15 mm

Thickness of flat plate
test piece: 10 mm

Items

Conditions

Hours of emission (hr)

AWJ nozzle

Angle nozzle

Injection pressure

343 MPa<Conclusion>

Injection flow rate

3.3 liter/min

Abrasive feed rate

100 g/min- Based on the above results, it was concluded that the nozzle
lifetime is 8 hours.

Cutting speed

60 mm/minNozzle durability test results

It takes about 42 hours to install the angle
nozzle, therefore, the method for replacing thenozzle needs to be considered in the future.
©International Research Institute for Nuclear Decommissioning6. Implementation details

No.32(1) Upgrading of processing technology for the top access investigation method
2) Implementation details for the second half of FY2021④ Test results (laser) [flat plate cutting test (1/2)] <Test results>- Angle nozzle performance test

<Test details>
Flat plates were cut in the direction of the flat plate
thickness by using either angle or straight nozzles toverify the performance of the angle nozzle based on
cutting depth.

Angle nozzle

Standoff: 50 mm
Standoff: 55 mm(Nozzle tip to focal point: 30 mm
Nozzle speed (Nozzle tip to focal point: 35 mm + + focal point to test piece: 20
focal point to test piece: 20 mm)(mm/min)mm)
Cutting depth
No.
(mm)

Feed direction Stroke: 40 mm
Emission angle 90°

Standoff

Cutting depth

No.

<Test conditions>
Laser nozzle

Straight nozzle

Cutting marks

Test No.

(mm)

300

1

20

1

22

180

2

24

2

31.5

120

3

28

3

38.5

1

2

3

1

2

3

Cutting depth
Flat-plate test piece
Plate thickness: 10 mm

Items
Laser nozzle

Conditions- Angle nozzle(Focal point: 35 mm from nozzle tip)
- Straight nozzle(Focal point: 30 mm from nozzle tip)

Laser output

8 kW

Auxiliary airpressure

0.68 MPa

Auxiliary air flowrate

- Angle nozzle: approx. 680 liter/min- Straight nozzle: approx. 750
liter/min

Test pieces (angle nozzle)<Conclusion>

Test pieces (straight nozzle)- The angle nozzle of cutting performance was about 20 to 30% inferior to that of thestraight nozzle.
- Although angle nozzles are inferior in performance to straight nozzles, angle nozzles
were deemed to have sufficient ability to cut the reactor internals.
(Even at a nozzle speed of 300 mm/min, a cutting depth of 20 mm was achieved, and
it is possible to cut the steam separator main body of up to 3.2 mm in thickness)©International Research Institute for Nuclear Decommissioning6. Implementation details

No.33(1) Upgrading of processing technology for the top access investigation method
2) Implementation details for the second half of FY2021④ Test results (laser) [flat plate cutting test (2/2)]<Test results>- Performance test of laser output (actual
Laser output: 7.2 kW
Laser output: 8 kW (*1)
equipment assumed)Standoff: 55 mm<Test details>

The flat plate was cut by moving the nozzle in the direction of
the flat plate thickness at 7.2 kW, which takes into accountthe loss of laser output in the actual equipment. The
performance of the laser was verified from cutting depth.

Nozzle speed (Nozzle tip to focal point: 35 mm + focal point to test
piece: 20 mm)(mm/min)Cutting depth
Cutting depth
No.
No.
(mm)
(mm)

<Test conditions>Feed direction Stroke: 40 mm

55 mm

Laser nozzle

Emission angle 90°
Cutting marks

300

1

19

1

20

180

2

23

2

24

120

3

28

3

28

(*1): The laser output result of 8 kW is shown for comparison with the results of the angle nozzle
performance test on the previous page.
Test No.

3

2

1

1

2

3

Cutting depth
Flat-plate test piece
Plate thickness: 10 mm

Items
Laser nozzle

Conditions
Angle nozzle(Focal point: 35 mm from
nozzle tip)

Laser output

7.2 kW

Auxiliary air pressure

0.68 MPa

Auxiliary air flow rate

Approx. 680 liter/min

Test pieces (laser output 7.2 kW)

Test pieces (laser output 8 kW)<Conclusion>- There was no significant difference in cutting depth between
laser outputs 7.2 kW and 8 kW; the mockup cutting test was
conducted with 7.2 kW laser output to verify operational
conditions.
©International Research Institute for Nuclear Decommissioning6. Implementation details

No.34(1) Upgrading of processing technology for the top access investigation method
2) Implementation details for the second half of FY2021④ Test results (laser) [Mockup cutting test (1/10)]- Summary of operational conditions for each treatment target
The table below shows the operational conditions for each treatment target verified in the mockup cutting test.
Processing objects
Steam dryer

Steam separator
Main bodyLaser cutting conditions

Upper surface

Area subjected
for cutting

Cutting speed

Rib- Small diameter- Connecting rod cutting - Upper rib cutting
machining: 354°/min: 94°/min- Lower rib cutting: 516°/min- Large diameter: 118°/min
machining: 46°/minNozzletype

Connection bars

- Straight nozzle

Commonconditions

Bottom plate

Shroud head

Laser output: 7.2 kW, auxiliary air pressure: 0.68 MPa
Auxiliary air flow rate: approx. 750 liter/min (straight nozzle )/approx. 680 liter/min (angle nozzle)

Steam separator
Side plate

Rib

NozzleConnection
bars

Steam separator

NozzleArea
subjected
for cutting

NozzleBottom plate

Area subjected for cutting- Straight nozzle

NozzleNozzleArea subjected
for cutting
Steam separator- Straight nozzle-

Area subjected
for cutting

Steam separator upper surface

Steam separator
main body- Upper flat plate- Vertical cutting
cutting: 60 to 300 mm/min: 92°/min - Horizontal cutting- Vertical cutting: 190°/min: 60 to 120 mm/min- Horizontal cutting: 190°/min- Straight nozzle+- Angle nozzle- Angle nozzle

NozzleArea subjected
for cutting

Shroud head

- Drilling of central
hole: 286°/min- Circumferential
cutting: 20°/min- Straight nozzle

Total actual operation duration:
approx. 4 hours©International Research Institute for Nuclear Decommissioning6. Implementation details

No.35(1) Upgrading of processing technology for the top access investigation method
2) Implementation details for the second half of FY2021④ Test results (laser) [mockup cutting test (2/10)]- Steam separator: cutting of main body (1/8)<Test details>
The conditions for cutting the main body of the steam separator were confirmed.
<Cutting procedure (actual equipment assumed)> *: Cut the main body of the steam separator by combining steps ① through ⑥.
Angle
nozzle0°

Steam separator 1

Steam separator 2
Spacer 1

Middle
tube

270°
90°
Outer
tube
Spacer 4

Steam separator 3

180°
Shape before treatment① Vertical cutting (exterior)③ Horizontal cutting② Vertical cutting (spacers 1, 4)
Spacer 2

Cutting height for 1 round (50 mm)

Spacer 3④ Vertical cutting (interior)⑤ Vertical cutting (before⑥ Vertical cutting (spacers 2, 3)
reaching spacer): Range added in FY2021, not simulated in AWJ cutting until FY2020.

Shape after treatment (1 round)©International Research Institute for Nuclear Decommissioning6. Implementation details

No.36(1) Upgrading of processing technology for the top access investigation method
2) Implementation details for the second half of FY2021④ Test results (laser) [mockup cutting test (3/10)]- Steam separator: cutting of main body (2/8) <Test results><Test conditions>- Vertical cutting (exterior) for the outer tube at 300 mm/min
was possible.

① Vertical cutting (exterior)
Outer tube Middle tube

Steam separator 1

Steam separator 3②(Turning radius of nozzle tip)

⑤

④

③

⑥

Inner tube

Cutting line ①

Steam separator 2
Steam separator 2⑥

Cutting line ①

Nozzlerunning④③②

Steam separator 1⑤
Steam separator 3
Outer tube
Inner tube

Middle tube

Drawing of cutting conditions
Items

Outer tube

Conditions

Laser nozzle

Angle nozzle

Laser output

7.2 kW

Auxiliary gas

Air

Auxiliary gas pressure /flow rate

0.68 MPa / approx.
680 liter/min

Standoff

47.2 mm

Cutting speed

300 mm/min

Cutting line ②

Photo of test piece: vertical cutting (exterior)©International Research Institute for Nuclear Decommissioning6. Implementation details

No.37(1) Upgrading of processing technology for the top access investigation method
2) Implementation details for the second half of FY2021④ Test results (laser) [mockup cutting test (4/10)]- Steam separator: cutting of main body (3/8)<Test conditions><Test results>② Vertical cutting (spacers 1, 4)Outer tube

- Vertical cutting (spacers 1, 4) for each spacer at 300
mm/min was possible.

Middle tube
(Turning radius of nozzle tip)

Spacer 2

Inner tube

Spacer 1

Inner tube

Cutting line ①

Spacer 1

Spacer 3

Spacer 1

Middle tube
NozzlerunningOuter tube②
Spacer 4

Cutting line ①

Spacer 4

Outer tube
Inner tube

Spacer 4

Drawing of cutting conditions
Items

Inner tube

Conditions
Middle tube

Laser nozzle

Angle nozzle

Laser output

7.2 kW

Auxiliary gas

Air

Auxiliary gas pressure /flow rate

0.68 MPa / approx. 680 liter/min

Standoff①: 32.2 mm (until spacer)②: 50.5 mm (until spacer)

Cutting speed①: 300 mm/min②: 300 mm/min

Outer tube

Cutting line ②

Photo of a test piece: vertical cutting (spacers 1, 4)©International Research Institute for Nuclear Decommissioning6. Implementation details

No.38(1) Upgrading of processing technology for the top access investigation method
2) Implementation details for the second half of FY2021④ Test results (laser) [mockup cutting test (5/10)]- Steam separator: cutting of main body (4/8)<Test conditions><Test results>- Horizontal cutting was possible for cutting the outer andmiddle tubes and spacer at 190°/min.

③ Horizontal cutting

SpacerSteam separator 3(Turning radius of nozzle tip)③

Cutting line ①
25*2 (*1 part)

Steam separator 2

②

②

③

Cutting line ①
SpacerOuter tube Inner
tube

Inner tube

Drawing of cutting conditions
Items

Steam separator 1

Conditions

Laser nozzle

Angle nozzle

Laser output

7.2 kW

Auxiliary gas

Air

Auxiliary gas pressure /flow rate

0.68 MPa / approx.
680 liter/min

Standoff

5 to 59 mm

Cutting speed

190°/minInner tube

Cutting line ②

Middle tube

Cutting height: 50 mm
Outer tube

Photo of a test piece: horizontal cutting©International Research Institute for Nuclear Decommissioning6. Implementation details

No.39(1) Upgrading of processing technology for the top access investigation method
2) Implementation details for the second half of FY2021④ Test results (laser) [mockup cutting test (6/10)]- Steam separator: cutting of main body (5/8)<Test conditions><Test results>- Vertical cutting (interior) for the middle tube at 300
mm/min was possible.

④ Vertical cutting (interior)
Outer tube

Middle tube⑤
(Turning radius of nozzle tip)

Cutting line ①④

Steam separator 3⑥

Inner tube②

Steam separator 2
Nozzlerunning⑤

Cutting line ①③③

Steam separator 1④
Outer tube
Inner tube

Drawing of cutting conditions
Items

②

Conditions

Laser nozzle

Angle nozzle

Laser output

7.2 kW

Auxiliary gas

Air

Auxiliary gas pressure/ flow rate

0.68 MPa / approx. 680
liter/minStandoff

8.3 to 30 mm

Cutting speed

300 mm/min

Inner tube
Middle tube
Cutting line ③

Outer tube

Photo of a test piece: vertical cutting (interior)©International Research Institute for Nuclear Decommissioning6. Implementation details

No.40(1) Upgrading of processing technology for the top access investigation method
2) Implementation details for the second half of FY2021④ Test results (laser) [mockup cutting test (7/10)]- Steam separator: cutting of main body (6/8)<Test results><Test conditions>- Vertical cutting (before reaching spacer) at 300
mm/min was possible.

⑤ Vertical cutting (before reaching spacer)
Outer tube

Middle tube
(Turning radius of nozzle tip)

Spacer 2

Spacer 2

Spacer 1

Inner tube

Cutting line ①
Spacer 3

Spacer 3

Cutting line ①
Nozzlerunning②

Cutting line ②

Spacer 4

Outer tube
Inner tube

Drawing of cutting conditions
Items

Conditions

Laser nozzle

Angle nozzle

Laser output

7.2 kW

Auxiliary gas

Air

Auxiliary gas pressure / flow rate

0.68 MPa / approx. 680 liter/min

Standoff①: 44.9 mm (until spacer)②: 44.9 mm (until spacer)

Cutting speed①: 300 mm/min②: 300 mm/min

Photo of a test piece: vertical cutting (before reaching spacer)©International Research Institute for Nuclear Decommissioning6. Implementation details

No.41(1) Upgrading of processing technology for the top access investigation method
2) Implementation details for the second half of FY2021④ Test results (laser) [mockup cutting test (8/10)]- Steam separator: cutting of main body (7/8)<Test results><Test conditions>- Vertical cutting (spacers 2, 3) at a cutting speed of
300 mm/min was possible.

⑥ Vertical cutting (spacers 2, 3)Outer tube Middle tube
(Turning radius of nozzle tip)
Spacer 2

Spacer 2

Steam separator 3

Steam separator 2

Spacer 1

Inner tube

Cutting line ①
Spacer 3

Spacer 3
Nozzlerunning②

Spacer 4

Outer tube
Inner tube

Steam separator 1

Drawing of cutting conditions
Items

Conditions

Laser nozzle

Angle nozzle

Laser output

7.2 kW

Auxiliary gas

Air

Auxiliary gas pressure / flow rate

0.68 MPa / approx. 680 liter/min

Standoff①: 53.7 mm (until spacer)②: 53.7 mm (until spacer)

Cutting speed①: 300 mm/min②: 300 mm/min

Cutting line ①
Cutting line ②
Outer tube

Outer tube
Middle tube

Middle tube

Spacer 3

Inner tube

Inner tubeSpacer 2

Photo of test piece: vertical cutting (spacer 2, 3)©International Research Institute for Nuclear Decommissioning6. Implementation details

No.42(1) Upgrading of processing technology for the top access investigation method
2) Implementation details for the second half of FY2021④ Test results (laser) [mockup cutting test (9/10)]- Steam separator: cutting of main body (8/8)<Test results>
Steam separator 2

Steam separator 2

Opening after cutting

Round 1Round 2Round 3

Steam separator 1

Round 4

Steam separator 3
Steam separator 1

Steam separator 3
Photo ① of test pieces : after 4 rounds of cutting

Photo ② of test pieces after 4 rounds of cutting- The main body of the steam separator was cut into four pieces by using
the angle nozzle in accordance with the cutting procedures described in
the previous pages.
- To cut the steam separator body, the angle nozzle can be applicable tovertical and horizontal cutting.
©International Research Institute for Nuclear Decommissioning6. Implementation details

No.43(1) Upgrading of processing technology for the top access investigation method
2) Implementation details for the second half of FY2021④ Test results (laser) [mockup cutting test (10/10)]- Other treatment targets
Side plate
Connection bars

Rib

Opening

Opening

Cut pieces

Opening

Bottom plate

Steam dryer bottom plateSteam
separator

Steam separator connecting rods

Steam
separator

Steam separator ribs

Steam
separator

Steam separator upper surface

Steamseparator

A cutting test for each nozzle was also carried out for objects to beprocessed other than the main body of the steam separator. It wasverified that all reactor internal structures to be processed can be cut.
In addition, both the angle and straight nozzles were used for 1.5 times
longer than the actual operational duration, thus it was concluded that
there are no issues concerning durability.

Ope
ning

Shroud head (front)

Shroud head©International Research Institute for Nuclear Decommissioning6. Implementation details

No.44(1) Upgrading of processing technology for the top access investigation method
2) Implementation details for the second half of FY2021⑤ Design of actual equipment- An element test was conducted to verify that there is no problem in cutting performance of the AWJ nozzle(angle nozzle) and laser nozzle (angle nozzle) that were designed in FY2021.
- Designing for incorporation into actual equipment was performed.
- Assuming actual equipment operations, the addition of cameras to each nozzle was examined and reflected in
the design.

Connected to articulated guide pipe
Connected to articulated guide pipe

Laser nozzle(angle nozzle)

Camera (downward vertical orientation)
Camera (lateralview orientation)
Camera (downward verticalorientation)
AWJ nozzle(angle nozzle)

AWJ head (built-in angle nozzle)

Camera (lateral view orientation)

Laser head (built-in angle nozzle)©International Research Institute for Nuclear Decommissioning6. Implementation details

No.45(1) Upgrading of processing technology for the top access investigation method
3) Summary and future issues
Summary- Nozzle downsizing in FY2020 enabled a significant reduction in abrasive consumption when cutting the main body of the steam
separator by AWJ (Abrasive Water Jet). In this fiscal year, study of further reduction of abrasive consumption including for cutting
targets other than the main body of the steam separator was conducted. Due to reduction and optimization of the abrasive feed rate
and use of the smaller FY2020 nozzles on cutting targets other than the main body of the steam separator, the prospect ofachieving the target abrasive consumption of 500 kg or less was verified through element tests.
- Laser cutting was not applicable in FY2020 and a nozzle applicable for horizontal cutting of the steam separator main body was
examined. By combining the nozzle studied in FY2020, the operational conditions were verified to allow cutting of all targeted
reactor internals.

Issues to be addressed
No. Major items Intermediate
items
1

Cutting
machine

AWJ cutting

Issues to be addressed- Nozzle lifetime

Laser cutting - Feasibility of the remote equipment,
taking into account actual operational
conditions

Drum
Pipe sling
Hoisting equipment- Incorporation into the fiber drum (*)(*):In reference to the drum, see diagram on
the right.

- Investigation or examination of slip rings
for high power lasers
Common2

Ancillary
operations

Common- Remote insertion of a cutting nozzle into
narrow spaces- Verification method for the treatment
target status before and after cutting- Treatment of cut pieces (moving)

Schematic drawing of equipment for operating onreactor internals (studied in FY2019)©International Research Institute for Nuclear Decommissioning6. Implementation details

Common to Units 1, 2 and 3

No.46(2) Development of the bottom access investigation method

Definition of development items: definitions of access equipment and investigation equipment
The technology applied to RPV interior investigation method from the bottom was divided into the following
three categories and reviewed.
Inside the RPVCore support plate(iii)
CRD housing top
surface

Inside the PCV

(ii)

7.2 m

(i)
CRD opening

10.6 mPCV

Platform

Inside the pedestal(i) Access equipment inside the pedestal ⇒ appropriation of technology developed in other projects(ii) Access equipment from inside the pedestal to inside the RPV ⇒ new development item(iii) Investigation equipment ⇒ appropriation of technology developed in other projects

Based on the FY2020 study results, access equipment to inside the RPV using adrone for Unit 1 and telescopic equipment for Units 2 and 3 were identified as new
development items©International Research Institute for Nuclear Decommissioning6. Implementation details

Unit 1

No.47(2) Development of the bottom access investigation method (drone)
Unit 1: Development of drone for accessing inside RPV<Summary of implementation in the second half of FY2021>
Element tests for wired/wireless drones were conducted to address the issues from the previous fiscal year
and the studies from the first half of the fiscal year.
<Details of implementation in the second half of FY2021>
Research technology
Wired/wireless drone/ancillary system

Details of implementation①

Manufacturing of prototype②

Planning of element tests③ Conducting of element tests<Results>
Wired Drone:• Improved flight performance → Achieved target flight height of 7 m (*).
• Improved investigation performance → verified that in dark/rainy environments investigation can be
performed by panning and tilting the camera.
Wireless drone:• Improved flight performance → Achieved target flight height of 7 m (*) or more. Capable of approx. 6
minutes of continuous flight.
• Improved investigation performance → verified that in dark/rainy environments investigation can be
performed by panning and tilting the camera.
• Communications verification → Based on tests and analyses, prospects of communication with theactual drone are verified.
Ancillary system:• Cable drum → Verified electrified cable drum performance.
• Overhead view camera → Overhead camera monitored drones in flight to improve operability.
(*) For Unit 1, the distance from the platform to the top surface of the CRD housing is approx. 6.9 m, so a setting of 7 m is selected©International Research Institute for Nuclear Decommissioning6. Implementation details

Unit 1

No.48(2) Development of the bottom access investigation method (drone)
1) Summary of results through the first half of FY2021

Measures for addressing the failure to achieve the 7 m target flight height due to voltage drop in the power cable, and otherissues raised in FY2020 simplified tests were considered.
In addition, other items for new verification this year were examined, including a configuration study of the actual drone and theancillary system, and pertinent test plans were discussed.

(11 m(*))

Inside the
RPV

Investigationrange

RPV bottom head
opening, expected
diameter 1 m

Expected flightroute

Cable drum
(wired only)

Target flight height

Pedestal

Maximum expected flight heightDrone(wired/wireless)Core support
plate uppersurface(7 m)

Implementation details and results (See next page fordetails)• Summary of issues and discussion of countermeasures
proposed based on FY2020 test results• Review of items to be newly verified in FY2021• Study of actual drone and the ancillary system that theabove two items were reflected• Review of test plans to confirm proposed
countermeasures and new verification items

Extension arm
CRD opening

Grating(*) For Unit 1, the distance from the platform to the upper surface of the reactor
coresupport plate is approx. 10.9 m, so a setting of 11 m is selected

Illustration of actual investigation equipment©International Research Institute for Nuclear Decommissioning6. Implementation details

Unit 1

No.49(2) Development of the bottom access investigation method (drone)2) Implementation details for the second half of FY2021 (addressing issues from FY2020 test results)
Issues fromFY2020 test
results

Implementation details for the
first half of FY2021

Implementation details
for the second half of
FY2021

Achieving goals

Wired

Wireless

Insufficient flight height • Study of voltage drop countermeasuresdue to voltage drop in(High voltage cable adopted, DC-DC
the power cableconverter installed)• Element test using prototype

Ability of flight at least 7 mheightConducted―

There were events ofthe drone colliding into
the test system during
flight and crashing• Review of flight monitoring method(In addition to the control camera
Ability of operating the drone
mounted on the drone, an overhead view
without test system collisions• Element test using prototype
camera is installed at the tip of theby monitoring with anextension rod to monitor the position
overhead view camera.
between the drone and the test system)

Conducted ConductedDifficulty ininvestigation for thebottom of RPV due todrone turning
movements• Addition of a pan/tilt camera to theunderside of the drone for investigation
purposes considered(Investigation by drone turning
movements is not implemented)

Ability of covering the scopeof investigation inside theRPV bottom by keeping the• Element test using prototype drone within a diameter of 1
m in the RPV opening andpanning and tilting the survey
camera.

Conducted Conducted• Consideration of flight time extension(Increased battery capacity, morebatteries installed, etc.)- Based on measurements ofinvestigation duration, review
of target duration of 10• Element test using prototype
minutes- Evaluation of flight timeagainst reset target time―

Conducted• Examination of communication
verification method• Verification test ofcommunication acceptability
threshold• Analysis of radio wave
strength inside the pedestal
and RPV―

Conducted

Insufficient flight time
relative to target flighttime

Study of radio wave
communication
verification test

Ability of determining thetransceiver setting position
from the communication
acceptability threshold andradio wave strength analysis.

©International Research Institute for Nuclear Decommissioning6. Implementation details

Unit 1

No.50(2) Development of the bottom access investigation method (drone)2) Implementation details for the second half of FY2021 (implementation items added in FY2021)
Additional implementation
items

Implementation details in FY2021

Wired

Wireless

Combined wired drone cable

Test manufacturing of composite cable for operation system, power, and camera

Conducted―

Cable drum electrification

Test manufacturing of motor-driven cable drum

Conducted―

Evaluation of radiation resistance

Irradiation testing at the drone component level

Conducted Conducted

Dark environment effects

Flight test in a dark environment

Conducted Conducted

Rainy environment effects

Flight test in a rainy environment

Conducted Conducted

Verification of the scope ofinvestigation

Investigation scope verification test by survey camera operation

Conducted Conducted

Verification of minimum flight space

Minimum flight space verification test

Conducted Conducted©International Research Institute for Nuclear Decommissioning6. Implementation details

Unit 1

No.51(2) Development of the bottom access investigation method (drone)2) Implementation details for the second half of FY2021① Manufacturing of improved prototype (1/3)(Countermeasures for voltage drop of power cable/wired drone)<Issues>➢➢

Voltage dropped caused by increased cable mass due to flight
It was not possible to fly at the target 7 m height.

[Powersource]- Low voltage[Before flight]- Voltage: 24 V
- Electric current: 0.8 A

Drone[Power cable]- Length 15 m
- 2 body mass of 145 g/m- Conductor resistance 9Ω/km

8.3 voltage
drop

3.2 m flight

Power source

460 g cable traction[After flight]- Voltage: 16.2 V- Electric current: 42 A

<Countermeasures>➢ The voltage of the power source was increased and decreased just before the drone.
➢ A step-down converter (DC-DC converter) was installed in the drone[Power source]- High voltage- Step down
to 24 VPower source

DC-DC
converter[Drone]- Maximum voltage 24 V

©International Research Institute for Nuclear Decommissioning6. Implementation details

Unit 1

No.52(2) Development of the bottom access investigation method (drone)2) Implementation details for the second half of FY2021① Manufacturing of improved prototype (2/3) (Countermeasures for turning performance/common to
wired and wireless drones)<Issues>➢ It was not possible to turn over within the expected Φ1 m of the RPV opening.
➢ It was not possible to investigate around 360°circumference of the RPV bottom.

<Countermeasures>➢ A pan/tilt survey camera was attached to the underside of the drone➢ Pan and tilt operations were used to investigate the inside of the RPV bottom, and drone
turning operations were discontinued.
Maneuvering camera- Tilt: 90°

Drone

Survey camera
Survey camera- Pan: 360°
- Tilt: 180°

Drone survey camera installation position

Top of CRD housing

RPV
RPV bottom head opening

Illustration of RPV bottom investigation©International Research Institute for Nuclear Decommissioning6. Implementation details

Unit 1

No.53(2) Development of the bottom access investigation method (drone)2) Implementation details for the second half of FY2021① Manufacturing of improved prototype (3/3)(Countermeasures for operability: common to wired and wireless drones)
Φ1000<Issues>➢➢➢

Wired and wireless drone flight capability was confirmed through a series ofprocedures in a combined test
However, several times during the test, there were events of the drone
colliding with the mockup and crashing
Flying with only one drone-mounted camera carries a crash risk<Countermeasures>➢➢

Example picture from overhead
view camera image 1

Drone

Overhead view camera was added to confirm flight status with abird's-eye view
Additional survey cameras was used for the drone to aid in
Simulatedmaneuvering
RPV
opening
Simulated CRD opening
Extension rod

Example picture from overhead
view camera image 2

Cable drum

Cable feedmechanism
Overhead view camera 3(Wired drone only)

Overhead view
camera 2

Overhead view camera 1

Drone overhead view camera installation position

Example picture from overhead
view camera image 3©International Research Institute for Nuclear Decommissioning6. Implementation details

Unit 1

No.54(2) Development of the bottom access investigation method (drone)2) Implementation details for the second half of FY2021② Drone configuration (Exterior view of FY 2021 wired drone prototype)■ Maneuvering camera
2000TVL

Tilt: 90 degree mobility
150 degree camera angleof view■ Measurement camera 2000TVL
Pan: 360 degree mobility
Tilt: 180 degree mobility

Front view
Propeller guard

150 degree camera angle of view

Side view

Propeller (5 inch)[Main differences from the actual equipment plan]- Φ20 camera (built-in LED) not installed(Commercial camera and external LED lighting
substituted)- Dosimeter not installed- Connector integration⇒ Adding weight of mass difference of the above statedvalue does not result in any issues- Omission of fiber-optic dosimeter cable from composite
cable⇒ The fiber-optic cable is lightweight (0.04 g/m) and theprotective PEEK tube is quite rigid, so there are no
problems in the flight test

Propeller motor

Power cable
D: 25 AWG twisted pair cable (for drone control signals)

Maneuvering
cameraB: 26 AWG 4-stranded cable (for camera power source)

Communication cable
Dosimeter cable

Tension member + staple fiber interpositioning
F: PEEK tube (for fiber-optic cable protection)
E: 14 AWG insulated wire (for drone power source)
Binding tape
SheathTop view

C: 26 AWG 4-stranded cable (for LED power source)
A: 30 AWG coaxial cable (for camera signals)

Outer diameter: Φ9.5 mm, approx. mass: 120 kg/km

Illustration of composite cable arrangement©International Research Institute for Nuclear Decommissioning6. Implementation details

Unit 1

No.55(2) Development of the bottom access investigation method (drone)2) Implementation details for the second half of FY2021② Drone configuration (Exterior view of FY2021 wireless drone prototype)■ Maneuvering camera 2000TVL

Tilt: 90 degree mobility
150 degree camera angle of view

■ Measurement camera 2000TVL
Pan: 360 degree mobility
Tilt: 180 degree mobility
150 degree camera angle of view

Front view

Side view

Propeller guard[Main differences from the actual equipment plan]- Φ 20 camera (built-in LED) not installed(Commercial camera and external LED lighting substituted)- Dosimeter not installed⇒ Adding weight of mass difference of the above stated value
does not result in any issues

Propeller (5 inch)

Propeller motor

Wireless antenna(2.4/5.7 GHz)
Maneuvering
cameraTop view©International Research Institute for Nuclear Decommissioning6. Implementation details

Unit 1

No.56(2) Development of the bottom access investigation method (drone)2) Implementation details for the second half of FY2021③ Test plan (test items)

Test No.

Test classification

1
Flightperformance test

3
4Stand-alone
performancetest

6

Visualperformance test

7

8
Ancillary system
test

9

10

11

Once-through
test

12

15

Verification tests of the investigation(normal)Verification of the scope of investigation under normal
environmental conditions

Verification tests of the investigation(darkness)
Verification tests of the investigation(rainfall)
Cable drum performance verification
test

Verification of the scope of investigation in a dark
environment
Verification of the scope of investigation in a rainyenvironment
Verification of feeding/winding mechanism and random
winding prevention function
Verification of the functional linkage between the cable
drum and the cable feeding/winding mechanism at theextension arm tip
Verification of the functions of equipment under normal
environmental conditions via a series of investigation
procedures, and formulation of final investigation
procedure
Verification of the functions of equipment in a dark
environment via a series of investigation procedures, andformulation of final investigation procedure
Verification of the functions of equipment in a dark andrainy environment via a series of investigation
procedures, and formulation of final investigation
procedure

Flight travel time verification test

Cable drum and extension arm
combined performance verification test

Once-through test (darkness)Once-through test (darkness + rainfall)
Radiation
resistance test

13
14

Minimum flight space verification test
(vertical/horizontal directions)Continuous flight time verification test

Once-through test (normal)

Combined test

OthersCommunication
performance test

Test purpose
Verification of target flight height (7 m)capability/maximum flight height
Verification of continuous flight time
Verification of flight time from X-2 penetration to CRD
opening
Verification of the minimum dimensions of passable
horizontal and vertical openings

Flight height verification test

2

5

Test item

Wired

Wireless

Conducted Conducted-

Conducted-

Conducted

Conducted Conducted
Conducted Conducted
Conducted Conducted
Conducted Conducted
-

-

-

-

Conducted Conducted

Conducted Conducted

Conducted Conducted

Irradiation test

Verification of radiation resistance of each component

Threshold verification test

Verification of transmitted and received power thresholds
for maneuvering/video system wireless equipment

Radio wave propagation analysis

Verification of electric field strength distribution of
Conducted
maneuvering/video system wirelessradio waves in©International Research Institute for Nuclear Decommissioning
actual equipment system

Conducted Conducted-

Conducted

6. Implementation details(2) Development of the bottom access investigation method (drone)2) Implementation details for thesecond half of FY2021③ Test plan (test facility): Overview of mockup facility

Top of RPV
opening(height 7000 mm)

RPV interior (investigation area) simulation

No.57

Unit 1

Water drop jig

Rainfall (dripping water) simulation

Bottom of RPV
opening (height2500 mm)

Exterior view of mockup facility
CRD
opening ventSimulated RPV opening

12.8 mControl room
TIP guide pipe

CRD
opening vent

CRD opening
vent

In front of the CRD opening /Simulated control room

1.8 m

8.1 m
CRD opening / TIP guide pipe simulation

Front view of mockup facility©International Research Institute for Nuclear Decommissioning6. Implementation details

Unit 1

No.58(2) Development of the bottom access investigation method (drone)

RHV system (*2):
approx. 15 m3/h2) Implementation details for the second half of FY2021③ Test plan (test environment): Simulability of nitrogen and water injection into actual reactor

1. The effects of nitrogen (wind) injection
1)The distance between the drone survey location and the nitrogen outlet is large enough to preclude impacts ondrone flight.
2) The wind velocity conversion value at the RPV bottom opening, assuming that all of the injected nitrogen passthrough, is 0.02 m/s. A wind speed of 0.02 m/s corresponds to “wind scale 0 (calm)” in the Beaufort wind force
scale, which is an index of the Japan Meteorological Agency. This is an environmental condition in which smoke
rises straight up, and is not expected to affect drone flight.

Wind velocity conversion
Nitrogen injection volume (*1)

Expected dimensions of RPV
bottom opening

Wind velocity conversion value at
RPV bottom opening

Normal: 30 m3/h, Maximum: 50
m3/h

Diameter: Φ1 m, cross-sectional
area: 0.785 m2

0.02 m/s

JP system (*) 2:
approx. 15 m3/h(*1) Operational upper limit (limited by flow rate meter range, common to Units 1 to 3).
(*2) Quoted from the plant operational parameters on the TEPCO website.

Due to the above considerations, wind conditions due to nitrogen injection are not taken
into account in this test.

Nitrogen injection
location in RPV

2. The effects of water injection (rainfall)

1) The amount of water injection into the reactor is equivalent to 189.8 mm/h of rainfall water conversion value in the Reactor Pressure Vessel,
which corresponds to “heavy rain (80 mm/h or more)” according to the Japan Meteorological Agency’s index.
These precipitation conditions are the environmental condition in which umbrellas are completely useless, making drone flight difficult.
2) As a countermeasure, suspension of water injection is proposed during the investigation. In the 2019 water injection test for Unit 1, water
injection was suspended for 49 hours without any issues. However, even when water injection is suspended, water dripping from the wet
structure continues to be an environmental condition.
3) Therefore, this test is conducted in a dripping water environment, and the drip rate is set at 100 cc/min. When reviewing the video during theinvestigation inside the Unit 2, it was verified that the drip rate was acceptable: 100 cc/min, similar to the drip rate in this test. In addition, thedrone should be designed to withstand dripping water.

Rainfall volume conversion
Reactor water injection amount (*3)
Feedwater system: 2.0 m3/h, Cesium(CS) system: 1.4 m3/h
→ Total: 3.4 m3/h

Reactor pressure vessel

Rainfall volume conversion value
inside the Reactor Pressure Vessel

Inner diameter: Φ4.775 m, Cross- (*3) Quoted from the plant operational parameters on the
189.8 mm/h
sectional area: 17.91 m2
TEPCO website.

Based on the above considerations, this test was conducted with the condition of dripping water (driprate: 100 cc/min, equivalent to rainfall of 8 mm/h). ©International Research Institute for Nuclear Decommissioning6. Implementation details

Unit 1

No.59(2) Development of the bottom access investigation method (drone)2) Implementation details for the second half of FY2021④ Test results (Test No.1: Flight height verification test)
Test results

Test
purposeTest details

Verificationof target
flight height(7 m)capability/maximumflight height① The ability of thetarget flight height of 7m was verified by theflight test.
② A maximum flightheight was verified by
the flight test.

Test methods① For the wired drone, the composite cable(15 m) is marked, and the drone is raised.
② For the wireless drone, the flight height ismarked on the test facility, and the drone israised.
③ After the drone rises, if it can hover for 10
seconds at each arrival point, it is deemedcapable of flight.

Wired drone

Wireless drone① Target flight height of 7 m waspossible.
② Although the maximum flightheight was 9 m, there was a casein which the drone lost control
and crashed due to a rise in ESC(*1) temperature when flying at 9m. Therefore, 8 m is considered
the actual flight height limit.

① Target flight height of 7m was possible.
② Capable of flying up toa maximum expected
flying height of 11 m (*2).

(*1) Abbreviation of Electric Speed Controller. Part that controls drone motor speed.
(*2)Core support plate upper surface position: A target of 11 m (exceeding approx. 10.9 m) was set.
Wirelessdrone

Hovering for
10 seconds

Identification
mark

Wired drone

Flight height

Hovering for
10 seconds

Flight height(7 to 11 m)

Composite
cable[Wired drone]
Wired drone

Wireless drone

Overview of the test

[Wireless drone]

Test conditions©International Research Institute for Nuclear Decommissioning6. Implementation details

Unit 1

No.60(2) Development of the bottom access investigation method (drone)2) Implementation details for the second half of FY2021④ Test results (Test No. 2: Continuous flight time verification test)

Test
purposeVerificationofcontinuous
flight time

Test results

Test details

Test methods

The available
flight timeusing selectedbattery isverified byflight test.

① The flight time until landing caused byrunning out the battery (3500 mAh x 2units) was verified. The flight stateshould be hovering or repeatedascent/descent.
② As a reference data, the battery of4600 mAh x 2 units (*1) was also
verified.

Wireless drone[Flight time] (*2): - Hovering: 5 minutes 48 seconds (8 minutes 54 seconds)- Repeated ascent/descent (1 to 2 m): 6 minutes 4 seconds(8 minutes 49 seconds)- Repeated ascent/descent (1 to 7 m): 5 minutes 57
seconds (8 minutes 51 seconds)→ Average 5 minutes 56 seconds.
[Number of round trips]:- Repeated ascent/descent (1 to 2 m): 31.5 times (49.5
times)- Repeated ascent/descent (1 to 7 m): 16.5 times (26.0
times)
Figures in parentheses are results of 4600 mAh x 2 units,
and for reference only(*1) This values is a reference, as the 4600 mAh battery was too large for the drone cover to shut completely.
(*2) The lack of a large impact of flight form on continuous flight duration can be attributed to smooth maneuvering, with no sudden ascent or descent.
Ascent/descent
Wireless drone

Wireless drone

Wireless drone

Flight height(1 to 7 m)

Ascent/descent

Hovering

Flightheight (1 to
2 m)

Flight height(1 m)[Hovering][Ascent/descent (1 to 2 m)][Ascent/descent (1 to 7 m)]

Test conditions
Overview of the test
©International Research Institute for Nuclear Decommissioning6. Implementation details

Unit 1

No.61(2) Development of the bottom access investigation method (drone)2) Implementation details for the second half of FY2021④ Test results (Test No.3: Flight travel time verification test)
Test results

Test purpose

Test details

Test methods
Wireless drone

Verification offlight time fromX-2
penetration to
CRD opening

After installing through the
PCV penetration, the timeand battery consumption
were verified when moving to
the CRD opening are verified
by the flight test.

The drone flies while taking off and landing at equalintervals between markers that simulate the route fromthe X-2 penetration to the CRD opening to verify theflight time and battery consumption from takeoff tolanding.

① Flight time: (average) 1 minute 08 seconds(*1)② Battery A consumption 7.3% / Battery B
consumption: 6.7%: (average) 7% (*2)(The wireless drone is equipped with twobatteries of the same type, which are referred
to as battery A and battery B for
convenience.)(*1) One-way value for X-2 penetration to CRD opening. In the case of a round trip with the return trip taken into consideration, the flight time is 2 minutes
and 16 seconds.
(*2) One-way value for X-2 penetration to CRD opening. In the case of a round trip with the return trip taken into consideration, battery consumption is 14%.

Pilot

Wireless drone

Take-off andlanding
distance(≒3200)Flightheight(850 mm)MarkerFlight direction(counterclockwise rotation)

Overview of the test

Conditions of the test
©International Research Institute for Nuclear Decommissioning6. Implementation details

Unit 1

No.62(2) Development of the bottom access investigation method (drone)2) Implementation details for the second half of FY2021④ Test results (Test No.4: Minimum flight space verification test (vertical/horizontal directions))

Test
purposeVerification of
the minimum
dimensions ofpassablehorizontal
and verticalopenings

Test results
Test details
Vertical or
horizontal flightinside the mockup facility wasverified.

Test methods① Flight performance of a round-trip flight from the bottom tothe top of the inside of a 4.5 m long rectangular mockup
facility with a □800 mm opening is verified.
② If the □800 mm opening can be passed, a modified testwith a □600 mm opening is conducted.
③ The mockup is laid on its side to verify dimensions of themockup that flight is possible.

Wired drone

Wireless drone□800 mm- Vertical: passable (*1)
- Horizontal: passable□600 mm- Vertical: passable (*1)
- Horizontal: passable□800 mm- Vertical: passable (*1)
- Horizontal: passable□600 mm- Vertical: not passable- Horizontal: passable(*1) Although the drone passed through, there were instances when it lightly brushed against the mockup or protruded outside of flight path boundaries.

Wired drone

Wirelessdrone

Composite cable

Wired drone

Composite cable

Verticaldirection

Wirelessdrone

Vertical direction

Verticaldirection

Horizontal direction

Overview of the test

Horizontal
direction

Horizontal
direction

Test conditions©International Research Institute for Nuclear Decommissioning6. Implementation details

Unit 1

No.63(2) Development of the bottom access investigation method (drone)2) Implementation details for the second half of FY2021④ Test results (test No. 5, 6, 7: Verification tests of the investigation (normal, dark, rainfall))

Test purpose

Test details

Test methods

Verification of thescope ofinvestigation(undernormal/dark/rainy
conditions)

The visibility range in a test facility thatsimulated the bottom of the RPV wasverified while the drone maintained
hovering and operating the pan tilt
camera.

① In order to verify the visibility range, visibility confirmation panels are placed aroundthe test facility of height equal to the RPV bottom, and the visibility range is verified
while the drone maintains hovering at 7 m target height by operating the pan tilt
camera.
② The three patterns of conditions are implemented in (1) normal, (2) dark, and (3)rainy environmental conditions.

2500 mm
MSP Gothic text 100 pt (24×20.5)

90°
0°

180°

Visibility confirmation panel
5 panels arranged at 500 mm
intervals from the center ofthe opening in 4 directions

7000 mm (target flight height)

6057 mm (RPV bottom head height)

270°

Remarks:- For wireless, no cable drum or composite cable- The dark environmental condition is simulated by turning off nearby lightings at night- The rainy environmental condition (dripping water) is simulated by dripping water at 100 cc/min from the water dripping jig

Overview of the test

Test conditions (normal
environmental)

Test conditions (darkenvironment)©International Research Institute for Nuclear Decommissioning6. Implementation details

Unit 1

No.64(2) Development of the bottom access investigation method (drone)2) Implementation details for the second half of FY2021④ Test results (Test No. 5: Verification tests of the investigation (normal))
Test results
Wired drone (*1)

Wireless drone (*2)

① The observation of character shapes were verified at a panel
position of 2500 mm.
② The smallest characters were clearly identified at a panel position of1000 mm.

① The observation of character shapes were verified at a panel position of2500 mm.
② The smallest characters were identified at a panel position of 1000 mm.

(*1) Composite cables obstruct visibility and can make it difficult to verify panels, so cable treatment is an issue.
(*2) Interference from wireless radio waves can cause intermittent noise in the video feed, and video quality is inferior to that of wired systems.
90° bearing

180° bearing

270° bearing

Wireless

Wired

0° bearing

Survey video (normal environment)©International Research Institute for Nuclear Decommissioning6. Implementation details

Unit 1

No.65(2) Development of the bottom access investigation method (drone)2) Implementation details for the second half of FY2021④ Test results (Test No. 6: Verification tests of the investigation (darkness))
Test results

Wired drone (*1, 2)

Wireless drone (*3)

① The observation of character shapes were verified at a panel positionof 2500 mm.
② The smallest characters were clearly identified at a panel position of1000 mm.

① The observation of character shapes were verified at a panel position of2000 mm.
② The shape of the panel itself was verified at a panel position of 2500mm.

(*1) Composite cables obstruct visibility and can make it difficult to verify panels, so cable treatment is an issue.
(*2) LED lighting sometimes reflected off the drone's legs and composite cables, negatively impacting visibility.
(*3) Interference from wireless radio waves can cause intermittent noise in the video feed, and video quality is inferior to that of wired systems.

90° bearing

180° bearing

270° bearing

Wireless

Wired

0° bearing

Survey video (dark environment)©International Research Institute for Nuclear Decommissioning6. Implementation details

Unit 1

No.66(2) Development of the bottom access investigation method (drone)2) Implementation details for the second half of FY2021④ Test results (Test No. 7: Verification tests of the investigation (rainfall))
Test results
Wired drone (*1, 3)

Wireless drone (*2, 3)① The observation of the character shapes was verified at a panel
position of 2500 mm.
② The smallest characters were clearly identified at a panel position of1000 mm.

① The observation of the character shapes was verified at a panel positionof 2500 mm.
② The smallest characters were identified at a panel position of 500 mm.

(*1) Composite cables obstruct visibility and can make it difficult to verify panels, so cable treatment is an issue.
(*2) Interference from wireless radio waves can cause intermittent noise in the video feed, and video quality is inferior to that of wired systems.
(*3) Since the survey camera is mounted on the bottom of the drone, water dripping from the top had virtually no impact.
90° bearing

180° bearing

270° bearing

Wireless

Wired

0° bearing

Survey video (rainy environment)©International Research Institute for Nuclear Decommissioning6. Implementation details

Unit 1

No.67(2) Development of the bottom access investigation method (drone)2) Implementation details for the second half of FY2021④ Test results (Test No.8/9: Cable drum performance verification test/Cable drum and extension arm
combined performance verification test)

Test item

Test purpose

Test details

Cable drum
performanceverification
test

Verification of
feeding/winding
mechanism andrandom winding
prevention function① The ability of
feeding/winding was verified.
② The irregular winding
during feeding/winding wasverified.

① Feed and wind the cable, verify
feeding/winding capability, drum
cable condition, and cableappearance.

① Feeding/winding (without irregular winding) was
possible, and there were no observed abnormalities
that could affect cable performance.
② When feeding the cable, it sometimes caught theback side of the drum, so countermeasures for theseissues are necessary.

Verification of thefunctional linkage ofthe cable drum andthe cable feedingmechanism at theextension arm tip

It was verified that there is no
problem in cable feeding andwinding to confirm combined
operations.

① According to the expected
procedures of the actual equipment,
performance verification tests wereconducted to confirm operations of
the cable drum, the feed mechanism
at the extension arm tip, andperformance (via flight test) of thewired drone.

Same as above

Cable drum
andextensionarm
combined
performanceverification
test

Test methods

Test results

Motor for drum rotation

Signal slip ring

Winding drum

Cable feed motor

Tension spring(for cable tension)Composite cable(Φ10 mm × 15 m)

Slip ring for power source

Cable feed roller
Tension spring(for cable feeding)Drone investigation
cameraLED lighting

Base

Cable drum
Cable is fed to the rear ofthe drum
Verify the functional linkage ofthe feeding/winding
mechanisms

Test conditions

Illustration of the combined test overview©International Research Institute for Nuclear Decommissioning6. Implementation details

Unit 1

No.68(2) Development of the bottom access investigation method (drone)2) Implementation details for the second half of FY2021④ Test results (Test No. 10/11/12: Once-through test (normal, darkness, darkness + rainfall))
Test purpose

Test details

Test methods

Verification of the functions ofequipment via a series ofinvestigation procedures, anddevelopment of the final
investigation procedure(normal/dark/dark + rainyenvironment)① Validity of the investigation procedure andimplementation guidelines were confirmed.
② Flight capability, capability of investigation, andflight duration were verified.
③ Issues to be addressed were identified.

The series of operations were verified under normal/dark/dark+ rainy environment conditions according to the investigation
procedures and implementation guidelines expected for actual
equipment.

Water drop jig

Overhead view
camera image(Extension arm tip)

Simulated RPV
opening Φ1000 mm

7000 mm (target flight height)

Simulated TIP guide tube
CRD opening

Overhead view camera 2
Cable drum
Overhead view camera
3 (wired only)

Extension arm
Overhead view
camera 1

Composite cable(wired only)

Overhead view camera
image(Body of extension arm)

Overhead view
camera image(Cable drum)
CRD opening

Composite cable
Wired drone
RPV opening
Extension arm

Maneuvering
camera image

Survey camera
image

Test facility

Simulated cockpit area
・1 monitor each for piloting/investigation
・3 overhead view camera monitors
・Cable feed control panel

Overview of the test
©International Research Institute for Nuclear Decommissioning6. Implementation details

Unit 1

No.69(2) Development of the bottom access investigation method (drone)2) Implementation details for the second half of FY2021④Test results (Test No. 10: Once-through test (normal))
Test results

Wired drone

Wireless drone

Flight capability: flyable (*1)
Investigation capabilities: video verification possible (with cable reflection)
Duration of investigation: 8 minutes 15 seconds (round trip) (*2)

Flight capability: flyable/Surveyable: video verification possible (withintermittent video noise)
Duration of investigation: 2 minutes 9 seconds (round trip) (*2)
Battery A consumption: 36%/Battery B consumption: 35% :: (average) 35.5%(*1) There is an issue in cable treatment because cables may come in contact with the floor.
(*2) Excluding time for extension/retraction of extension arm. Flight duration may depend on pilot skill.

Maneuvering camera

Investigation camera

Maneuvering camera

Investigation camera

Overhead view
camera 1

Overhead view
camera 1

Overhead view
camera 2

Overhead view
camera 3

Video from wired drone camera

Overhead view
camera 2

Overhead view
camera 3

Video from wireless drone camera©International Research Institute for Nuclear Decommissioning6. Implementation details

Unit 1

No.70(2) Development of the bottom access investigation method (drone)2) Implementation details for the second half of FY2021④ Test results (Test No. 11: Once-through test (darkness))
Test results
Wired drone

Wireless drone

Flight capability: flyable (*1)
Investigation capabilities: video verification possible (with cable reflection)
Duration of investigation: 8 minutes 49 seconds (round trip) (*2)

Flight capability: flyable/Surveyable: video verification possible (withintermittent video noise)
Duration of investigation: 2 minutes 24 seconds (round trip) (*2)
Battery A consumption: 43%/Battery B consumption: 42%: (average) 42.5%(*1) There is an issue in cable treatment because cables may come in contact with the floor.
(*2)Excluding time for extension/retraction of extension arm. Flight duration may depend on pilot skill.

Investigation camera (right: when the cable is reflected)

Investigation camera (right: when noise occurs)
Overhead view
camera 1

Overhead view
camera 1

Overhead view
camera 2

Overhead view
camera 3

Video from wired drone camera

Overhead view
camera 2

Overhead view
camera 3

Video from wireless drone camera©International Research Institute for Nuclear Decommissioning6. Implementation details

Unit 1

No.71(2) Development of the bottom access investigation method (drone)2) Implementation details for the second half of FY2021④ Test results (Test No. 12: Once-through test (darkness + rainfall))
Test results
Wired drone

Wireless drone

Flight capability: Flight is available. (*1)
Investigation capabilities: video verification possible (with cable reflection)(*2)
Duration of investigation: 9 minutes 00 seconds (round trip) (*3)

Flight capability: Flight is available. /Investigation capabilities: video
verification possible (with intermittent video noise) (*2)
Duration of investigation: 2 minutes 11 seconds (round trip) (*3)
Battery A consumption: 37%/Battery B consumption: 39%: (average) 38%(*1) There is an issue in cable treatment because cables may come in contact with the floor.
(*2) The bottom-mounted drone survey camera was virtually unaffected by dripping water. On the other hand, top-mounted maneuvering camera’s view was intermittently
blocked by dripping water.
(*3) Excluding time for extension/retraction of extension arm. Flight duration may depend on pilot skill.

Maneuvering camera (while water is dripping)
Overhead view
camera 1

Maneuvering camera

Investigation camera

Overhead view
camera 1

Overhead view
camera 2

Overhead view
camera 3

Video from wired drone camera

Overhead view
camera 2

Overhead view
camera 3

Video from wireless drone camera©International Research Institute for Nuclear Decommissioning6. Implementation details

Unit 1

No.72(2) Development of the bottom access investigation method (drone)2) Implementation details for the second half of FY2021④ Test results (actual equipment procedure): Based on the results of the once-through test,
the actual equipment is operated in the following procedure.
Wired drone actual equipment procedure
ProcedureNo.

Operation of cable drum

Operation of extension arm

Initial condition

8 m cable is wound-up

Extension arm is retracted. The cable is sent out 3 m from the extension arm
tip①

Send out 7 m of cable

Send out 2 m of cable from the extension arm tip②―

Operation of wired droneStandby just before entrance to the CRD opening――

Take off and hover at the exit of the CRD opening

Extend the extension arm 5.3 m and point the overhead view camera towards
the RPV opening③

Pass under the TIP guide pipe, move directly below the RPV
opening and hover

④

―

⑤

―

⑥

―

―

Ascend to the target height and investigate inside the RPV

⑦

―

―

After investigation, descend directly below the RPV opening and
hover

⑧

―

⑩

―

⑪

―

―

Send out 2 m of cable from the extension arm tip

Wind up 2 m of cable

⑨

⑫

―

―

Wind up 2 m of cable from the extension arm tip―

Pass under the TIP guide pipe, move to the exit of the CRD
opening and hover―

Return to the entrance of the CRD opening and land―

Retraction of the extension arm

Wind up 5 m of cable―

Wind up 2 m of cable from the extension arm tip

Wireless drone actual equipment procedure
Procedure No.
Initial condition

Operation of extension arm
Extension arm is retracted

Wireless drone operation
Standby just before entrance to the CRD opening①

Extend the extension arm 5.3 m and point the overhead view camera towards the
RPV opening

―

②

―

Take off and fly to the survey location. After completing the investigation, return to the entrance of
the CRD opening and land③

Retraction of the extension arm―©International Research Institute for Nuclear Decommissioning6. Implementation details

Unit 1

No.73(2) Development of the bottom access investigation method (drone)2) Implementation details for the second half of FY2021④ Test result (Test No. 13: Irradiation test)
Test results
Test purpose
Verification ofradiation
resistance of
eachcomponent

Test details
The irradiation tests
for the component
level were conducted
to verify the radiation
resistance of eachcomponent.

Test methods
The following items are applied to both wired/wireless drones① Two sets of drones for the trial irradiation test were
manufactured. Only one of the drones were irradiated with
100 Gy (*1).
② Each component of the irradiated drone was replaced one
by one with the equivalent component from the non-irradiateddrone to verify functional operation of each component.

Wired drone

Wireless drone

The flight controller
has a malfunction.
(*2)

The flight controller
has a malfunction.
(*2)(*1) Estimated value assuming a survey duration of 10 minutes.
(*2) During the operation verification, an abnormality in the flight controller compass (function to verify the bearing of the aircraft) was identified. However,no compass sensor was used in this test. Therefore, manufacturing of a flight controller with no compass sensor is necessary.
Propeller
motor

CameraManeuveringsystem receiver

Flight controller

RS485 converter

Altimeter

ESG

Dedicatedcircuit board[Wired drone][Wireless drone]Videotransmitter

Maneuvering
camera tilt motor

Test component configuration
Test conditions (wireless drone)©International Research Institute for Nuclear Decommissioning6. Implementation details

Unit 1

No.74(2) Development of the bottom access investigation method (drone)2) Implementation details for the second half of FY2021④ Test result (Test No.14,15 Communication performance test)

Communication performance of wireless drones
1) In order to use wireless drones in the actual facility, it is necessary to evaluate maneuvering and video transmission capability ofwireless drones.
2) In the actual equipment, a transceiver was installed at the extension arm tip for communication, but wireless radio waves may beshielded by the reactor internals, making communication impossible.
3) Moreover, the tests up to last fiscal year verified that simulating the actual wireless environment was difficult.

As described to the above, communication performance was evaluated by comparing the results of Test No. 14(threshold verification test) and Test No. 15 (radio wave propagation analysis).

RPV (steel)Predicting the location of the signal
reception boundaryRadio waves
Transmitter

ReceiverCRD (steel,annular)Pedestal(concrete)

CRD opening

Illustration of actual equipment

Transmission
power [dBm]

Transmission
electric fieldstrength [dBV/m]

Electric fieldstrength threshold[dBV/m]Electric field strength
distribution [dBV/m] depending
on distance and presence ofobstacles

Monitoror motor

Received power
threshold [dBm]

Convert withconversion formula

The transmitted/received images of actual equipment signals show themethod of obtaining each physical quantity (testing or analysis). Notethat blue and green letters indicate data from the test and analysis,
respectively.

Illustration of signal propagation and relationshipbetween test data and analysis data
©International Research Institute for Nuclear Decommissioning6. Implementation details

Unit 1

No.75(2) Development of the bottom access investigation method (drone)2) Implementation details for the second half of FY2021④ Test result (Test No. 14 Threshold verification test)
Test purpose

Test details

Test methods

Verification oftransmitted andreceived power
thresholds formaneuvering/video
system wirelessequipment

The transmitted
and received power
thresholds of thetransmitter for use
as an analytical
input were
measured.

① Measure the transmission power of maneuvering system 2.4 GHz/Video system 5.7 GHz.
② Since the 2.4 GHz band is used for communication components such as wireless LAN, thetransmission/reception antenna should be installed in an anechoic box.
Increase the attenuation of the attenuator and measure the received power when motor
function is disturbed.
③ The 5.7 GHz band requires a license and notification for use. The transmitter is installed in
an anechoic box and the transceiver is connected by cable. Increase the attenuation of theattenuator and measure the received power when the video is disturbed.

Actualequipment
systemExtension arm tip

Receiving antenna

Transmitter

ReceiverTransmitted power [dBm]

Test system

Cable

Transmitter

Transmitted
power [dBm]

Actualequipment
systemWireless drone

Transmitting
antenna

Radio waves(attenuated in space)

Transmitting
antenna

Attenuator

Flightcontroller

Motor

Receiver

ReceiverRadio waves(attenuated inspace)

MonitorReceived power [dBm]

Cable
Motor

Anechoic box (prevention of radio
wave intrusion)

Maneuvering system 2.4 GHz

Transmitter

Test system

Radio waves(attenuated in space) Received power [dBm]
Simulation of radio wave
attenuation in space

Receiving antenna

Transmitted power [dBm]

Receiving antenna
Flightcontroller

Transmitting antenna

CameraReceived power [dBm]

Extension arm tip

Wireless drone

CameraTransmitter

Attenuator

Transmitted power [dBm]
Anechoic box (preventionof radio wave leakage)

ReceiverMonitorReceived power [dBm]
Simulation of radio wave
attenuation in space

Video system 5.7 GHz

Comparison between actual equipment system and test system©International Research Institute for Nuclear Decommissioning6. Implementation details

Unit 1

No.76(2) Development of the bottom access investigation method (drone)2) Implementation details for the second half of FY2021④ Test result (Test No. 14 Threshold verification test)
Received power
measurement cable

Test results

Receiving Power Attenuator

Receiving antenna
Attenuator(0 to 70
dB)

Counter

Transmitter

Anechoic antenna
Received power box
measurement
cable

sourceCable

Transmitting
antennaCounterantenna
Flightcontroller

Anechoic box

Powersource

Motor

Counter

Motor
Counter antenna

Maneuvering system 2.4 GHz

MonitorCameraTransmitter

SubjectPowersourceAttenuator(90 to 130
dB)

ReceiverAnechoic box

Frequency[GHz]

Transmitted
power [dBm]

Received power
threshold [dBm]

2.4

15.8

-95.1

5.7

28.4

-86.6

Transmitter
Transmitting antenna

Subject

Cable

MonitorCameraPowersourceTransmitter

Power source

ReceiverAttenuator

Video system 5.7 GHz

Summary of testing status

Changes in video state dependingon the amount of attenuation©International Research Institute for Nuclear Decommissioning6. Implementation details

Unit 1

No.77(2) Development of the bottom access investigation method (drone)2) Implementation details for the second half of FY2021④ Test results (Test No. 15 Radio wave propagation analysis)
Analysis purpose

Analysis content

Analysis method

Verification of electric fieldstrength distribution of
maneuvering/video systemwireless radio waves in
actual equipment system

Analysis software conducts
simulations of actual equipment toanalyze the electric field strength
distribution of the 2.4 GHz
maneuvering system and the 5.7
GHz video system.

① For analysis conditions, the wave source input should be the transmitted power of
the transmitter. In addition, 8 case analyses for both 2.4 and 5.7 GHz in total wereconducted while changing the CRD shape, wave source position, and antennaorientation.
② At the transceiver position expected in the actual equipment, the received power
threshold value obtained from analysis results and testing were compared with thevalue converted to the electric field strength.

CRD
shape

Wave sourceheight (*)
Pedestal

1

CuboidParallelTarget (7 m)

2

CuboidOrthogonalTarget (7 m)

3

CylinderParallelTarget (7 m)

CylinderOrthogonalTarget (7 m)

5

CuboidParallelMaximum (11 m)

6

CuboidOrthogonal

Maximum (11 m)

7

CylinderParallelMaximum (11 m)

8

CylinderOrthogonal

Maximum (11 m)

CRD opening

CRD switchboard, etc.
(Platform)

CRD opening

Analysis system overview
Analysis: cylindrical model

4

CRD

Approx. 7 m

No.

Flight height(target)
RPV

PCVOpening

Antennaorientation
relative to CRD
openingCore support plate upper surface

Φ1000 (RPV opening)

RPV

CRD

Approx. 11 m

Analysis conditions for 2.4 GHz maneuveringsystem / 5.7 GHz video system

Drone

Flight height(maximum)Wave source height (drone
flight position)

Analysis: cuboid model

Pedestal interior

RPV opening

Pedestal exterior
Opening Φ1000

Opening Φ1000

Extensionarm
CRD opening

Crawlergroundcontact
No.1(*) Due to the reversibility of radio waves, the drone is usedas the wave source location.

CRD shape (left figure: cylindricalmodel, right figure: cuboid model)

No.2

No.3

No.4

Analysis evaluation positions©International Research Institute for Nuclear Decommissioning6. Implementation details

Unit 1

No.78(2) Development of the bottom access investigation method (drone)2) Implementation details for the second half of FY2021④ Test results (Test No. 15 Radio wave propagation analysis)
Analysis/threshold comparison results① Comparison of tests and analyses suggests a high likelihood of maneuvering/video system communication capability inside the CRD
opening.
② Communication with the 5.7 GHz video system may not be possible outside the CRD opening.
2.4 GHz analysis: CRD (cuboid model)_wave source (maximum flightheight)_antenna orientation (parallel)

5.7 GHz analysis: CRD (cylindrical model)_wave source (target flightheight)_antenna orientation (parallel)

No.3(entrance to
CRD opening)

No.1 (justbelow theRPV opening)

No.4(extension
arm core)

5.7 GHz analysis: CRD (cylindrical model)_wave source(target flight height)_antenna orientation (parallel)

Threshold

Position from center of RPV opening [m]Analysis results (2.4 GHz operating system)

No.2(pedestalinterior)

No.3 (entrance
to CRD
opening)

No.4(extension
arm core)

Electric field strength [dBV/m]

2.4 GHz analysis: CRD (cuboid model)_wave source (maximum
flight height)_antenna orientation (parallel)

No.2(pedestalinterior)

Electric field strength [dBV/m]

No.1 (justbelow theRPV opening)

Threshold

Position from center of RPV opening [m]Analysis results (5.7 GHz video system)

Note: The threshold (red line) is the received power threshold from “Test No. 14 Threshold verification test,” converted from [dBm] to [dBV/m].

Based on the above results, both of maneuvering and video systems will be able tocommunicate when the transceiver inside the CRD opening (with the extension arm) is
installed by using the extension arm.
©International Research Institute for Nuclear Decommissioning6. Implementation details

Unit 1

No.79(2) Development of the bottom access investigation method (drone)2) Implementation details for the second half of FY2021④ Test results (wired drone test results and evaluation of applicability to actual equipment)
Test No.

Test item

Wired drone

Evaluation of applicability to actual equipment- Capable of 7 m target flight height and 8 m maximum flightheight.
- Crashed at 9 m flight height due to temperature rise inelectronic speed controller (ESC).

- Capable of reaching the upper surface of the CRD housing.
- Heat generation from the electronic components in the fuselage is an issue
that needs to be addressed. (Ambient temperature must also be considered)-1

Flight height verification test

2

Continuous flight time verification
test

-

3

Flight travel time verification test-

- Even at □800 mm, there is contact with the frame when passing through.
Thus it is believed that 1 m, which is the current expected dimension, isnecessary for the actual equipment. (The actual equipment applicability will
be determined based on the results of the prior investigation inside thepedestal.)

4

Minimum flight space verification
test(vertical/horizontal directions)- Vertical: Capable of passing through □ 800 mm, 600 mm
despite hitting the frame.
- Horizontal: Capable of passing through □600 mm.

5Verification tests of theinvestigation (normal)

6

Verification tests of theinvestigation (darkness)- Prospects to be able to verify structures at the bottom of the RPV.
- There is background reflection from aircraft components in the survey
image.
→ The drone legs structure needs to be reviewed, but the reflection fromthe wired cables is difficult to deal with.

7

Verification tests of theinvestigation (rainfall)- Normal: It is possible to identify character shapes at a panel
position of 2500 mm.
- Darkness: It is possible to identify character shapes at apanel position of 2500 mm.
- Rainfall: It is possible to identify character shapes at a panel
position of 2500 mm. Water droplets have no effect.
- There are cases where cables block the view for all of theabove.

8

Cable drum performanceverification test

- A design is needed that better directs cables during feeding.

9

Cable drum and extension arm
combined performance verification
test- Feeding/winding is possible without irregular winding.
- In some cases, cables get fed to the back side of the drum
during feeding.

10

Once-through test (normal)- With monitoring by an overhead view camera, the drone can fly in a seriesof procedures. However, it also depends on the pilot's skill, so sufficienttraining is required when using the actual equipment.

11

Once-through test (darkness)

12

Once-through test
(darkness + rainfall)(darkness + rainfall results below)- Flight capability: flight possible (no crashes thanks tomonitoring by overhead view camera monitoring)- Investigation capabilities: video verification possible (noeffects from water droplets)- Duration of investigation: 9 minutes 00 seconds (round trip)-There is contact between the cable and floor.

13

Irradiation test

- There is something wrong with the compass in the flightcontroller.

- Necessity of using a flight controller that does not have a compass sensor.
→ It is necessary to investigate the components that can be mounted orconsider custom manufacturing

14/15

Threshold verification test/Radio
wave propagation analysis-©International Research Institute for Nuclear Decommissioning6. Implementation details

Unit 1

No.80(2) Development of the bottom access investigation method (drone)2) Implementation details for the second half of FY2021④ Test results (wireless drone test results and evaluation of applicability to actual equipment)
Test No.

Test item

Wireless drone- Capable of flying 11 m.

- Capable of reaching the upper surface of the CRD housing. It can alsoreach near the maximum core support plate.

1

Flight height verification test2

An average continuous flight duration of 5 minutes 56
Continuous flight time verification test -seconds
is feasible.
- X-2 penetration CRD opening round trip time: 2 minutes 16
Flight travel time verification test
seconds- Round trip battery consumption: 14%

3

4

6
7

Verification tests of the investigation(rainfall)

8

Cable drum performance verification
test
Cable drum and extension arm
combined performance verification
test

9- Evaluated by once-through test items- Evaluated by once-through test items- Even at □800 mm, there is contact with the frame when passing through.
Thus it is believed that 1 m, which is the current expected dimension, isnecessary for the actual equipment. (The actual equipment applicability will
be determined based on the results of the prior investigation inside thepedestal.)- Normal: It is possible to identify character shapes at a panel - Prospects to be able to investigate the bottom of the RPV.
position of 2500 mm.
- However, due to intermittent noise, the image quality is inferior to wired.
- Darkness: It is possible to identify character shapes at a
- Image noise is caused by radio wave multipath, which is difficult to deal
panel position of 2000 mm.
with at present.
- Rainfall: It is possible to identify character shapes at apanel position of 2500 mm.
Water droplets have no effect.
- There is intermittent noise for all of the above.

□800 mm is passable although there is contact with
Minimum flight space verification test Vertical:
the frame.
(vertical/horizontal directions)
Horizontal: □600 mm is passable.
Verification tests of the investigation(normal)Verification tests of the investigation(darkness)

5

Evaluation of applicability to actual equipment

10

Once-through test (normal)

11

Once-through test (darkness)

12

Once-through test
(darkness + rainfall)

13

Irradiation test

14/15

Threshold verification test/Radio
wave propagation analysis--(darkness + rainfall results below)- Flight capability: capable of flying. (No crashes thanks tomonitoring by overhead view camera)- Investigation capabilities: video verification possible(intermittent video noise, no effects from water droplets)- Duration of investigation: 2 minutes 11 seconds (round trip)- Battery consumption: 38%- Monitoring by overhead view camera enables stable flight.
- From the total with flight travel time, total flight duration is 4 minutes and
27 seconds. The continuous flight duration is 5 minutes and 56 seconds, so
the prospect for investigation is favorable.
- In an evaluation of battery consumption, a series of surveys consumed
52% of battery charge.
- The above calculation does not take into account factors like time waiting
for the crawler (between the X-2 penetration and CRD opening), or
electrical tolerance, so further study is required.
- Necessity of using a flight controller that does not have a compass- There is something wrong with the compass in the flightsensor.
controller.
→ It is necessary to investigate the components that can be mounted orconsider custom manufacturing.
Both
the 2.4 GHz maneuvering system and 5.7 GHz video system are- Communication is possible by installing a transceiver inside expected
to be able to communicate by installing the transceiver inside thethe entrance of the CRD opening.
CRD opening.
©International Research Institute for Nuclear Decommissioning6. Implementation details

Unit 1

No.81(2) Development of the bottom access investigation method (drone)2) Implementation details for the second half of FY2021

Summary- In the simplified FY2020 test, the wired drone failed to reach its target flight height due to a voltage drop in the
power cable, and the wireless drone failed to extend flight time. Issues common to both drone types included
drone monitoring methods and difficulty in investigating the RPV bottom due to turning movements of a drone. In
response to these issues, countermeasures were examined and a drone was test-manufactured.
- Besides that, element tests were performed to verify the effect of these countermeasures, including proposed
countermeasure for dealing with actual environments (darkness, dripping water, etc.).
- From the results of the element tests, the wired drone achieved the target flight height by revising the power
supply method, and the wireless drone was able to remain in flight longer than the target time by revising thebattery configuration.

Remaining issues
New issues from the FY2021 test results and other potential issues are shown below.
• Feasibility of a series of investigation methods (including access from X-2 penetration to CRD opening)• Feasibility of extension rods under development for other projects and their combination with cable drumequipped crawlers• Radiation resistance of drone (wired/wireless) electronic components• Investigation or surveying of lightweight radiation sensors that can be mounted on wireless drones©International Research Institute for Nuclear Decommissioning6. Implementation details

Units 2 and 3

No.82(2) Development of the bottom access investigation method (telescopic pipe)

Units 2 and 3: Development of telescopic equipment for accessing inside RPV<Summary of implementation in the second half of FY2021>- In regards to the FY2020 development issues, the conceptual study
and necessary element tests were conducted.
- Proposed countermeasures for FY2020 issues were reflected into
equipment specifications, and a simplified test with a 3-stage
telescopic guide pipe was conducted to verify the effect of thecountermeasures.
- Element tests were conducted to evaluate the feasibility of all 14stages of the access equipment, and to evaluate the feasibility of thetelescopic access equipment as a stand-alone unit.
<Details of implementation in the second half of FY2021>- Test to verify the effect of countermeasures- Conceptual study and simplified test regarding development issues- Feasibility verification test using the 14-stage telescopic guide pipe
- Feasibility evaluation<Results>- Conceptual design and element tests were conducted to addressdevelopment issues, including the study of connections on arm-typeaccess equipment for retrieval operations.
- Reflecting proposed countermeasures to last year's issues (leakage
and high sliding resistance), the 14-stage telescopic guide pipe was
manufactured and tested. Only telescopic access equipment wasevaluated as feasible.
©International Research Institute for Nuclear Decommissioning

Units 2 and 3

6. Implementation details

No.83(2) Development of the bottom access investigation method (telescopic pipe)
1) Summary of results through the first half of FY2021 (1/2)
In the simplified FY2020 test using a 3-stage telescopic guide pipe, factors of issues such as high leakage and sliding resistance at the sealing section
were analyzed, and the proposed countermeasures were examined. Proposed countermeasures, such as inner pipe surface roughness reduction, werereflected in equipment specifications and the effect was verified by simplified 3-stage telescopic guide pipe testing.

Implementation details and results
1. Overview of telescopic access equipment- The telescopic access equipment consists of a total of 14 thin-walled,
multi-stages to enable extension from dimensional constraint of approx.
1 m to 7 m in length, and Φ100 mm to enable connection with the fueldebris retrieval access equipment. In addition, it is extended using air
pressure and retracted by winding the cable inside the pipe.

7291 mm (when extended)1009 mm (when retracted)

Investigationequipment

Telescopic guide
pipe

Cable
winderOverview of telescopic access equipment

Schematic specifications of telescopic access equipment
Items

Specifications

Number of stages

14 stages

Material

Pipe: CFRP, aluminum
Other components: aluminumcomponents

Power source

Extension: air
Retraction: cable winder
Various motors: power source

Pipe thickness

1 mmDimensions when retracted(telescopic guide pipe only)

1100 mm or lessDimensions when extended(telescopic guide pipe only)

7100 mm or greater

Outer diameter

Base: Φ97 mm
Tip: Φ37 mm

Air pressure

Maximally extended: 0.1 MPa

Maximum transportable weight

2 kg (when air pressure is 0.1 MPa)

Cable

Built-in to telescopic guide pipe

Cable handlingControlled by reeling the cable winderat the base

Clearance between pipes

0.3 mm (pipe and piston clearance)

Seal material

NBR

CameraCCD or CMOS

©International Research Institute for Nuclear Decommissioning

Units 2 and 3

6. Implementation details

No.84(2) Development of the bottom access investigation method (telescopic pipe)
1) Summary of results through the first half of FY2021 (2/2)
Implementation details and results
2. Examination of proposed countermeasures to address issues- Proposed countermeasures against high leakage and sliding resistance at the sealing section were examined. Measures such as pipe innersurface roughness reduction were reflected in equipment specifications.
Issues andpresumed factors

EventsTechnical issue ①:leakage frompackings

Pipe surface roughness
Piston surface roughness
Increased resistance due tolooseness

Separation
betweensuppliedpressure andadjustmentpressure

Increased resistance due tosealing structure

Technical issue ②:
High sliding
resistance

Increased resistance due tocontact between pipe innersurface and lower piston
Increased resistance due tocontact between pipe innersurface and collar
Increased resistance due tocontact between pipe outersurface and scraper tip
Increased resistance due tocontact between dust seal andpipe outer surface
Increased resistance due tocontact between rail, scraperand top ring

Insufficienttension force
duringretraction

Increased resistance due tocontact between top ring andpipe outer surface

Cable ends were notsealedLow cable winder
tension force(*1) Items not applied

Inconsistent or non-uniform
grease application method,
location, amount, etc.

Proposed countermeasures(The effect was verified in FY2021 test)
Make the fold of the CFRP inner pipe surface
material unidirectional(Alternative)Adoption of aluminum for pipematerial
Adoption of aluminum for piston material
Use of WR sealing
structure
Use of GLY sealing
structure

Use of hybrid
sealing structure

Reduction of inner diameter of lower
pistonCollar outer diameter reduction
Use of a coating to improve sliding on the pipe
outer surface and scraper inner surface (*1)
Optimization of dust seal dimensions(*1)
Apply sliding material (*1)
Change of rail material(*1)
Fixing the top ring in place
Setting the location to be greased

Cable ends sealed during testing
Improvement of the cable winder torque

WR: Wear ring, GLY: Nitrile rubber (NBR) based packing©International Research Institute for Nuclear Decommissioning

Units 2 and 3

6. Implementation details

No.85(2) Development of the bottom access investigation method (telescopic pipe)2) Flow of “② Conceptual study of bottom access/investigation equipment”

FY2020① Planning of top access/investigation anddevelopment plan for access/investigationequipment② Conceptual study of bottom
access/investigation equipment<Conceptual design>

FY2021<Element tests>

Drafting of investigation
plan (Examination of
applicabletechnologies)(a) Factor analysis of
issues(e) Feasibility
verification test using
the 14-stage telescopic
guide pipe

Drafting of development
plan (Identification ofdevelopment issues)(b) Examination of
proposedcountermeasures(f) Feasibility evaluation(Stand-alone telescopic
access equipment)

Implementation of
simplified tests(c) Test to verify theeffect of proposed
countermeasures

Feasibility evaluation(Identification of newissues)(d) Conceptual study
and simplified tests fordevelopment issues

Investigation anddevelopment planning

Method planning©International Research Institute for Nuclear Decommissioning6. Implementation details

Units 2 and 3

No.86(2) Development of the bottom access investigation method (telescopic pipe)3) (c) Test to verify the effect of proposed countermeasures〇 Test items
Proposed countermeasures to test results of FY2020
No.

Test item
A

B

C

D

E

F

1

Test to verify the sealing functions

Done

Done

Done

―

―

―

2

Test to verify strength of connecting part

Done

Done

―

―

―

―

3

Section verification test

Done

Done

Done

Done

Done

Done

〇 Proposed measures for test results of FY2020 (from No. 84)

A

Issue ①: Leakage from packing
The CFRP folds of the pipe material of arechanged to the unidirectional folds.
(Alternative) Adoption of aluminum for pipe materialIssue ②: High sliding resistance
Reduction of inner diameter of lower piston

D

Fixing the top ring in place
Setting the spot for grease application

B
C

Issue ①: Leakage from packing
Adoption of aluminum for piston materialIssue ②: High sliding resistance
Adoption of WR
Adoption of hybrid
sealing structure
Adoption of GLY
sealing structure
sealing structure

E
F

Event ①: Separation between supplied pressure
and adjustment pressure
Sealing of cable ends during testing
Event ②: Insufficient tension force during retraction
Improvement of the cable winder torque©International Research Institute for Nuclear Decommissioning

Units 2 and 3

6. Implementation details

No.87(2) Development of the bottom access investigation method (telescopic pipe)3) (c) Test to verify the effect of proposed countermeasures<1. Test to verify the sealing functions>〇 Purpose
Regarding reduction of sliding resistance during extension/retraction, and pipe material and sealing structure candidates for air
leakage reduction, the purpose of the test is to select a suitable combination of sliding resistance and sealing efficiency (leakage
check, leakage volume) while verifying the effect.
Regarding new leakage volume verification to be implemented this fiscal year, it will be verified that the leakage flow rate from thepacking/external air ingress is low relative to the supply flow rate during telescopic pipe extension or the exhaust flow rate during
emergency retraction, and leakage volume is sufficient for smooth, reliable extension and emergency retraction operations.
〇 Test overview
The sliding resistance was measured by pulling the piston with a load weight gauge. The sealing capability (leakage check,leakage volume) was verified by investigating foaming of soapy water applied around the piston section after closing the ON/OFF
valve to collect air in a sealed container and opening the ON/OFF valve to send compressed air to the telescopic guide pipe. In
addition, the time variation of the pressure indicator (attached to the sealed container) readings during compressed air supply wasrecorded.
〇 Test system: Verification of sealing efficiency (leakage check,〇 Test system: Verification of sliding resistanceleakage volume)
Pipe fixture ①

Sealing section
Jig for securing
telescopic guide pipe
Telescopic guide pipe:
Dimension of 1st stage

Test piece

Soapy water application area

Joint

PistonPiston: Dimension of
2nd stage (withTensile components
thermocouple inside)
Pressure Air tube ①
Tool for securing tensile direction

indicator

Roller

Thermometer

ON/OFF valve

Air tube ②

Test piece

PulleyStopper

Platform
Pipe fixture ②

Wire (approx.
Φ1 mm)
Load weightgauge

Sealedcontainer
Air tube ③
Thermocouple cableAir supply
To data logger©International Research Institute for Nuclear Decommissioning

Units 2 and 3

6. Implementation details

No.88(2) Development of the bottom access investigation method (telescopic pipe)3) (c) Test to verify the effect of proposed countermeasures<1 Test to verify the sealing functions>

The effect of proposed countermeasures were verified under the following conditions. Since
performance of the hybrid sealing structure is direction-dependent, for the leakage volume verification
test and leakage check, the piston was installed upside down and pressure was applied from the
opposite direction.
Condition ①: Pipe material CFRP plain weave, CFRP axial UD, CFRP circumferential UD⇒ Verification of the effect of proposed countermeasure A, “Make the weave of the CFRP inner
pipe surface material unidirectional”
Condition ②: Piston material CFRP plain weave, aluminum⇒ Verification of the effect of proposed countermeasure B, “Adoption of aluminum for piston
material”
Condition ③: Sealing structure Normal type (GLY x 2), hybrid type (WR + GLY)⇒ Verification of the effect of proposed countermeasure C, “Adoption of hybrid sealing structure”

Inner wall ofthermostaticchamber

Fixture forsecuring
extensionpole

Telescopic guide pipe
/ piston

Load weight gauge
Test frame Wire
Extension
Tank
pole

Condition ④ (reference): Pipe material Aluminum⇒ Verification of the effect of proposed countermeasure A, “(Alternative) Adoption of aluminum forpipe material”
In addition, simulation tests were conducted under simulated environmental conditions, with thesealing section configuration selected from the results of this test. To verify the effects of different
environmental conditions, various tests were conducted under the conditions for doses of 0 Gy and7200 Gy (assuming 100 Gy/h for 3 days), temperatures of 25℃ (room temperature) and 50℃, normal
humidity and 100% humidity (simulated by immersing the furnace in room temperature water for 3days), and with and without wetting of inside pipes by water drops in the reactor.

Conditions ①, ④: Pipe material- CFRP plain weave- CFRP axial UD- CFRP circumferential UD- (Alternative) Aluminum

Outsidethermostaticchamber

Thermocouple
cable

Access hole

Air tube
Through-hole
Compressed air
injection→To data logger

Test system under simulated
environmental conditions

Condition ②: Piston material- CFRP plain weave- Aluminum
Condition ③: Sealing structure- Normal type (GLY x 2)
- Hybrid type (WR + GLY)

©International Research Institute for Nuclear Decommissioning6. Implementation details

Units 2 and 3

No.89(2) Development of the bottom access investigation method (telescopic pipe)3) (c) Test to verify the effect of proposed countermeasures<1. Test to verify the sealing functions>○ Selection indices for the sealing section configuration based on results of the sealing functions
verification test
Index ①: Sliding resistance- The primary candidate for the sealing section structure is the one with the lowest sliding resistancethat has a steady-state tension force less than the cable winder’s 319 N.
Index ②: Leakage volume- During extension: By increasing the source pressure, the leakage volume is expected to reduce thepressure inside the telescopic guide pipe to 0.10 MPa (upper limit 0.30 MPa)
- In case of emergency retraction: When the exhaust source pressure is set to -0.092 MPa (maximum
exhaust pressure), after taking into account the dead weight of each pipe and the investigationequipment, the leakage volume is expected to be sufficient to create a negative pressure (-0.090
MPa) that produces tension force equivalent to the extension force (maximum extension force) when
the pressure in the telescopic guide pipe is set to 0.10 MPa

In addition to the above indices, the sealing section configuration should be selected with considerationof operability.

©International Research Institute for Nuclear Decommissioning

Units 2 and 3

6. Implementation details

No.90(2) Development of the bottom access investigation method (telescopic pipe)3) (c) Test to verify the effect of proposed countermeasures〇 Summary of the sealing functions
verification test results1
2
3
Estimation scenarios<1. Test to verify the sealing functions>(Condition ①)

Sealing structure

Normal type
GLY×2

Normal type
GLY×2

Normal type
GLY×2

Normal type
GLY×2

Pipe inner surface
material

CFRP
Plain weave

CFRP
Axial UD
(Proposed
countermeasure A)

CFRP
Circumferential UD(Proposed
countermeasure A)

Piston material

CFRP
Plain weave

CFRP
Plain weave

CFRP
Plain weave

CFRP
Axial UD
(Proposed
countermeasure A)
Aluminum(Proposed
countermeasure B)
While
Max. value
sliding
22.0

Sliding resistance [N](Condition ①)

Sliding resistance(Examined in FY2020)

4(Condition ②)

Transport
Max. value
frequency

1
2
3
4

While
slidingMax. value
20.9

Omitted as
was already Approx. 16
reported in
to 27
FY20205

Average

Leakage volume

Whilesliding

―

34.9

21.4

22.3
21.1

While
slidingMax. value

26.6
Approx. 6 to
9

25.7

5
(Condition ③)
Hybrid type
WR+GLY(Proposed
countermeasure C)
CFRP
Axial UD
(Proposed
countermeasure A)
Aluminum(Proposed
countermeasure B)
While
Max. value
sliding
15.4

20.4
Approx. 6 to
11

20.9

13.4
Approx. 5 to
8

13.5

6
(Condition ④,
alternative)
Hybrid type
WR+GLY(Proposed
countermeasure C)
Aluminum(Proposed
countermeasure A)
Aluminum(Proposed
countermeasure B)
While
Max. value
sliding
12.7
11.6

Approx. 5 to
7

11.7

20.6

23.0

20.3

13.0

11.7

21.8

20.3

20.7

13.4

12.3

―

21.3

―

23.4

―

20.9

13.7

―

12.0

Approx. 3 to
4―

Piston direction

―

―

―

―

Front-facing Rear-facing Front-facing Rear-facing

Time from 0.10 MPa
to 0.09 MPa

7 seconds

1 min. 12 sec.

1 min. 34 sec.

118 min. 22 sec.

113 min. 58 5 min. 16 131 min. 26 128 min. 41
sec.
sec.
sec.
sec.

Leakage volume
from 2nd stage pipe

6 liter/min

0.6 liter/min

0.5 liter/min

0.006 liter/min

0.006
liter/min

0.140
liter/min

0.006
liter/min

0.006
liter/minLeakage volume whenconverted to 14-stage
telescopic guide pipe

55 liter/min

5 liter/min

4 liter/min

0.05 liter/min

0.06
liter/min

1.22
liter/min

0.05
liter/min

0.05
liter/min©International Research Institute for Nuclear Decommissioning

Units 2 and 3

6. Implementation details

No.91(2) Development of the bottom access investigation method (telescopic pipe)3) (c) Test to verify the effect of proposed countermeasures<1. Test to verify the sealing functions>〇 Summary: Planning of the sealing section configuration➢ The main proposal for pipe material is CFRP axial UD pipe, which reduces sliding resistance and leakage
volume compared to CFRP plain weave pipe.
- The CFRP axial UD with the lowest sliding resistance is selected for CFRP axial UD/circumferential UD- Although aluminum is superior to CFRP in both sliding resistance and leakage volume, due tomanufacturing issues, it is an alternative to the main proposal. The main proposal for piston material isaluminum, which can reduce leakage volume compared to CFRP plain weave pistons.
➢ The main proposal for a sealing structure is a hybrid sealing structure, which has lower sliding resistancethan the normal type, and by using the above pipe and piston, the leakage volume during telescopic guidepipe extension and the amount of outside air ingress during emergency retraction are sufficiently small
compared to the air tube’s supply/exhaust flow rate (CAD results verified that the telescopic guide pipe canenter the reactor bottom opening without scraping, and is effective at controlling tilt).
Considering operability and results of the sealing
functions verification test, the main proposals for thesealing section configuration used for the telescopic
guide pipe are as follows.

Wear ring
Scraper
Stopper ring

Dust seal

Pipe material: CFRP axial UD (proposed
countermeasure A)
Piston material: Aluminum (proposed
countermeasure B)
Sealing structure: Hybrid type (proposed
countermeasure C)

CollarUpper pipe:
CFRP axial UD

Top ring

Hybrid type
Packing forpneumatic
cylinders
Lower pipe:
CFRP axial UD

Piston: Aluminum©International Research Institute for Nuclear Decommissioning

Units 2 and 3

6. Implementation details

No.92(2) Development of the bottom access investigation method (telescopic pipe)3) (c) Test to verify the effect of proposed countermeasures <1. Test to verify the sealing functions>〇 Summary of the sealing functions verification test results (environmental simulation tests)
Environmental
conditions
Temperature
Cumulative doserate

Room temperature

Simulated reactor
environment 1
50℃

Simulated reactor
environment 2
50℃

0 Gy (unirradiated)

7200 Gy

7200 Gy

Normal environment

Wetting inside the
pipe

None

Sliding resistance[N]

Normal humidity

Sliding resistance

Humidity

Transportfrequency Max. value

1

15.4

2

13.4

None
Max. value

Whilesliding

14.2

4

13.0

14.3

24.2

5

13.4

15.9

23.6

Piston direction―
Rearfacing

14.9
Frontfacing

Whilesliding

22.1
Approx. 5
to 7

13.5

13.7
Frontfacing

13.4

Max. value

22.6

16.7
Approx. 5
to 7

Yes

3

Average

Leakage volume

Whilesliding

100% (immersed in 100% (immersed inroom temperature room temperaturewater for 3 days)
water for 3 days)―
Rearfacing

23.3

23.2
Frontfacing

Approx. 5
to 7

Environmental simulation tests were conducted with the
combination described in pattern 5 (the main proposal).
Conditions without environmental simulation were
described as normal environment. Sliding resistance wasalso measured under conditions where the inside of thepipe was not wetted, as water droplets inside the pipe
may lower sliding resistance. Since water droplets in thepipe are expected to increase sealing efficiency, leakage
volume verification was conducted only for non-wetting
conditions.
When the inside of the pipe was wet, sliding resistance
was approx. 10 N greater than in the normal environment,
but there was no difference in resistance when the piston
was sliding.
Leakage volume did not affect the extension/retractionof the telescopic guide pipe, and the simulated reactor
environment was less likely to leak.

―Rearfacing

Time from 0.10 113 min. 5 min. 16 132 min. 11 min. 26
MPa to 0.09 MPa 58 sec.
sec.
47 sec.
sec.

――

Leakage volume
from 2nd stage
pipe

0.006
liter/min

0.140
liter/min

0.005
liter/min

0.063
liter/min――Leakage volume
0.06
when converted to
14-stage telescopic liter/min
guide pipe

1.22
liter/min

0.05
liter/min

0.56
liter/min――Sliding resistance tends to increase in thereactor environment, but leakage volume is
reduced. The feasibility will be evaluated inconjunction with the results of “(e) Feasibility
verification test using the 14-stage telescopic
guide pipe.”©International Research Institute for Nuclear Decommissioning

Units 2 and 3

6. Implementation details

No.93(2) Development of the bottom access investigation method (telescopic pipe)3) (c) Test to verify the effect of proposed countermeasures<2. Adhesive strength verification test>〇 Purpose
The purpose of the test is to verify the strength of telescopic connecting part under expectedenvironmental conditions.
The pipe material (CFRP axial UD material: proposed countermeasure A) and piston material(aluminum material: proposed countermeasure B) that were proposed in No. 91 will be used for thetelescopic components.

Top ring

Collar Piston

Antirotation rail
Lower pipe

Upper pipe

〇 Test overview
Using a small connecting sample piece, a shear load was applied to the connecting part to verify thebreaking stress. The radiation environment simulated by pre-irradiating the connecting test piece. The
effects from storing samples for 72 hours under irradiation dose conditions of 0 Gy and 7200 Gy(assuming 72 hours at 100 Gy/h), at 50℃, 90% humidity, are verified〇 Evaluation items, etc.
No.

1

Test nameEvaluation items

Verification of strength ofconnecting part〇 Test system

CFRP

85 mm

- Breaking stress when shear load
is applied to the connecting
section- CFR pipe and each component- Aluminum pipe and eachcomponent

Objective (evaluation criteria)- The breaking stress when a shear
load is applied is
Pipe/top ring: 4.7 MPa or more*1
Pipe/piston: 4.7 MPa or more*1
Pipe/collar: 0.2 MPa or more*2
Pipe/rail: 0.3 MPa or more*2〇 Shear failure state
Connecting
failure surface

18 mm

Verification method- The stress at failure is measured by applying a
shear load to both irradiated and unirradiatedsamples and then gradually increasing the load (allsamples stored at constant temperature andhumidity).

*1: The maximum stress in the connecting part is 0.26 MPa, based on the maximum piston thrustof approx. 709 N (air pressure: 0.1 MPa x maximum pressure-receiving area (2nd stage sliderpart)) and the area of the connecting part: 2743 mm2 . Impacts of adhesive length on adhesivestrength reduction: (3) multiplied by the safety factor (6); the target is 4.7 MPa or more
*2: The maximum force needed to break the bond between collar and rail is approx. 73 N, which isequivalent to the sliding resistance during extension/retraction, and the target value is set by
multiplying the safety factor as in *1〇 Simulated scope of test system
5 mm
45 mm

Simulant target

Connecting
surface

2 mm
2 mm
45 mm
Tension direction

7200 Gy of cumulative irradiation, 50℃,
humidity: 95%, shear failure test results
after 24 hours of exposure

Points tosimulate

Connecting partsof CFRP/CFRP
CFRP/aluminum
Aluminum/aluminum- Material- Adhesive

Surrounding
environment- Irradiation
dose

Points not tosimulate

Reason for not simulating- Area ofconnecting part

Because the measurement ispossible in terms of breaking
stress by area.

- Test piece
thickness

Because it does not affect the
breaking stress- Darkness

Because it does not affect the
breaking stress©International Research Institute for Nuclear Decommissioning

Units 2 and 3

6. Implementation details

No.94(2) Development of the bottom access investigation method (telescopic pipe)3) (c) Test to verify the effect of proposed countermeasures② Pipe/rail① Pipe/top ring
Pipe: CFRP axial UD
Top ring: Aluminum (A5052)

Adhered with
POLYMETAC

The cutting process produces
aluminum pipes as one piece, so noconnecting is required

Connecting
part<2. Adhesive strength verification test>③ Pipe/collar

Pipe: CFRP axial UD
Rail: CFRP plain weave

Adhered withepoxy

Pipe: CFRP axial UD
Collar: CFRP plain weave

Adhered withepoxy

Pipe: Aluminum (A7075)
Rail: CFRP plain weave

Adhered with epoxy(*1)

Pipe: Aluminum (A7075)
Collar: CFRP plain weave

Adhered with
POLYMETAC

Top ring

CollarPistonRail

Lower pipe

④ Pipe/piston

Upper pipe

CFRP pipe
Aluminumpipe

Pipe: CFRP axial UD
Piston: Aluminum (A5052)

Adhered with
POLYMETAC

Pipe: Aluminum (A7075)
Piston: Aluminum (A5056)

Adhered with
POLYMETAC

The adhesive strength of the 5 types, “a” to “e”, to be used in telescopic equipment was evaluated.
CFRP pipe

Aluminum pipe

Adhered with CFRP axial UD/Aluminum(A5052) POLYMETACa

No adhesion―② Pipe/rail

Adhered with CFRP axial UD/CFRP
plain weave epoxybAdhered with aluminum (A7075)/CFRP
plain weave epoxyc③ Pipe/collar

Adhered with CFRP axial UD/CFRP
plain weave epoxybAdhered with aluminum (A7075)/CFRP
plain weave POLYMETAC

d④ Pipe/piston

Adhered with CFRP axial UD/Aluminum(A5052) POLYMETACa

Adhered with aluminum(A7075)/aluminum (A5056)
POLYMETACe① Pipe/top ring(*1) Pretreatment is not possible due to dimensional restrictions after anodizing, and POLYMETAC connecting is not possible. (The required strength is low due to rotation
control, so POLYMETAC connecting is not necessary)©International Research Institute for Nuclear Decommissioning

Units 2 and 3

6. Implementation details

No.95(2) Development of the bottom access investigation method (telescopic pipe)3) (c) Test to verify the effect of proposed countermeasures<2. Adhesive strength verification test>〇 Test results- CFRP pipe
The shear failure stress after irradiation ranged from 27.6 to 29.5 [MPa] with an average of 24.6 [MPa], while the unirradiated samples ranged from
16.6 to 20.6 [MPa] with an average of 18.6 [MPa]. There was no significant difference in bond strength. All samples were stored at constanttemperature and humidity. In both irradiated and non-irradiated test pieces, cohesive failure occurred within the adhesive bed, indicating that there wasno degradation of the adhesive due to irradiation.

Breaking stress (MPa)Breaking stress (MPa)- Aluminum pipe (alternative)
The shear failure stress after irradiation ranged from 21.8 to 29.4 [MPa] with an average of 26.5 [MPa], while the unirradiated samples ranged from25.1 to 30.6 [MPa] with an average of 27.9 [MPa], showing no significant difference in connection strength. In both irradiated and non-irradiated test
pieces, cohesive failure occurred within the adhesive bed, indicating that there was no degradation of the adhesive due to irradiation.

4.7

UnirradiatedUnirradiated under constanttemperature and humidity

Irradiated under constanttemperature and humidity

CFRP pipe/top ring & piston

4.7

UnirradiatedUnirradiated under constanttemperature and humidity

Irradiated under constanttemperature and humidity

Aluminum pipe/piston

Based on the above results, it was evaluated that there was no shear failure stress degradationof the connecting part within 72 hours (*) under the environment expected for the investigation
inside the RPV (temperature: 50[℃], humidity: 90%, and dose rate: 100[Gy/h]).
*From the result of cohesive failure (the adhesive strength test of previous fiscal year gave the same results), it was evaluated thatadhesion strength can be maintained for about 24 hours even in an irradiation environment©International Research Institute for Nuclear Decommissioning

Units 2 and 3

6. Implementation details

No.96(2) Development of the bottom access investigation method (telescopic pipe)3) (c) Test to verify the effect of proposed countermeasures<3. Section verification test>

The 3-stage telescopic guide pipe tests were conducted as in the previous fiscal year.
Proposed countermeasures were reflected to the 3-stage telescopic guide pipe.

A
B
C

D

Issue ②: High sliding resistance
Reduction of inner diameter oflower piston
Fixing the top ring in place
Setting the spot for grease application

E

Event ①: Separation between supplied pressure
and adjustment pressure
Sealing of cable ends during testingF

Event ②: Insufficient tension force during
retraction
Improvement of cable winder torque

Issue ①: Leakage from packing

Pipe material: CFRP axial UD adopted

Issue ①: Leakage from packing
Piston material: Aluminum adopted

Issue ②: High sliding resistance
Adoption of WR sealing
Adoption of hybrid
structuresealing structure
Adoption of GLY
sealing structure©International Research Institute for Nuclear Decommissioning6. Implementation details

Units 2 and 3

No.97(2) Development of the bottom access investigation method (telescopic pipe)3) (c) Test to verify the effect of proposed countermeasures

D<3. Section verification test><Reduction of inner diameter of the piston lower bottom><Adoption of slide-enhancing coatings on the pipe outer surface and thescraper inner surface>< Optimization of dust seal dimensions ><Apply a sliding material to the pipe outer surface><Change in rail material><Fixing the top ring in place><Setting the location for grease application><Reduction of inner diameter ofthe piston lower bottom>
Larger gap between pipe innersurface and lower end of piston
One side: 0.2 → 0.5 mm<Fixing the top ring in place>
Outer diameter from general
tolerance to fit tolerance
One side: 0.3 → 0.035 mm
Scraper
Stopper ring

Top ring

Packing forpneumatic
cylinders
Wear ring

Dust seal

Lower pipe

Scraper

Anti-rotation
rail
Upper pipe

CollarPiston<Setting thelocation for grease
application>

Only the above three items were reflected in the design.

Not reflected in the design for the following
reasons<Adoption of slide-enhancing coatings on the pipe
outer surface and the scraper inner surface>⇒ Each of the following items were considered but
not adopted due to respective issues● Fluorine coating Film thickness: 1 μm
The firing temperature of the coating is 120℃.
The operating environment temperature for
CFRP pipes is 80 to 100℃, so it is difficult toapply a coating (low-temperature coatings are
too thick and cannot be used).
● Plating
Film thickness 0.6 mm (copper plating 0.5 mm+ chrome plating 0.1 mm)
The feasibility of the plating treatment on CFRP
pipes is uncertain. In addition, since thethickness of the CFRP pipe is 1 mm, there is apossibility that the CFRP pipe will not be strong
enough due to shrinkage of plating from theplating treatment. Not adopted because theeffect of the final improvement is unknown.
<Optimization of dust seal dimensions>⇒ The gap between the dust seal and the pipe
was not enlarged, giving priority to the dust
seal's function of preventing foreign substancesfrom entering the pipe.
<Apply a sliding material to the pipe outer surface>⇒ Not adopted because dust adheres easily.
<Change in rail material>⇒ Not adopted due to significant impact of designchanges on adhesive strength, thermal
expansion, etc.
©International Research Institute for Nuclear Decommissioning

Units 2 and 3

6. Implementation details

No.98(2) Development of the bottom access investigation method (telescopic pipe)3) (c) Test to verify the effect of proposed countermeasures

E <Sealing of cable ends during testing><3 Section verification test>

In order to prevent the compressed air supplied to the cablewinder from leaking out through the cable, the part of thecomposite cable that will become a single wire is sealed(mold), excluding coating○ Sealed spot
① Cables for cable winder drive② Cables for investigation equipment
Mold location
Single wire

Composite cable

Cable
Location of object tobe sealed

Illustration of the mold
Cable winder examined in FY2020©International Research Institute for Nuclear Decommissioning6. Implementation details

Units 2 and 3

No.99(2) Development of the bottom access investigation method (telescopic pipe)3) (c) Test to verify the effect of proposed countermeasures<3. Section verification test>

F <Improvement of the cable winder torque>
To improve tension as much as possible within the dimensional constraints, the torque was increased byincreasing the reduction ratio of the drive. As a result, the constant tension force was able to reach 319 N(83 N for the equipment designed in FY2020), which is larger than the required maximum tension force ofapprox. 270 N verified in the FY2020 test.
Another modification was a structure with constant load on the motor, in order to maintain propulsion of
the telescopic guide pipe by cables. Therefore, the cable drum was structured to move through a worm
gear so that the load is not directly applied to the motor, and not to rotate when the power is lost, making
it possible to prevent the telescopic guide pipe from protruding.
Traverser roller

Cable outlet

Traverser
shaft

Worm gear
Cable drum

Conceptual drawing of the cable winder examined in FY2021©International Research Institute for Nuclear Decommissioning6. Implementation details

Units 2 and 3

No.100(2) Development of the bottom access investigation method (telescopic pipe)<3. Section verification test>3) (c) Test to verify the effect of proposed countermeasures
Tests for a 3-stage telescopic guide pipe were conducted as in the previous fiscal year.
3.1

Test items/outline

Confirmation items

Evaluation items

Objective(evaluation
criteria)

Results

Judge
ment

Test to verify the extension/retraction
operations of telescopic guide pipe

―

―

―

―

―

Verification of extension/retraction
operations

3.1.1 Verify whether the telescopic guide pipe can bevertically extended and retracted, and identify any
features unique to vertical operation

Cable tension required 319 N or lessduring retraction

Supplied pressure required forextension

Air pressure required 0.1 MPa or less0.03 MPa or lessduring extension
There was no difference
Difference between
between the supplied
supplied pressure and No significant
and the pressure
the pressure inside the pressure difference pressure
insidethetelescopic guidetelescopic guide pipe
pipe

Whether it is possible to supply
the desired pressure to inside
the pipe

Verification of rigidity when horizontal load
Tilt control of each sealing
is applied

3.2

extension

1.5 mm(Previous fiscal year result: 7 Goodmm)

Tensile force required frommaximum extension

Cable tension required 319 N or lessduring retraction

Tensile force during
retraction: 20 N to 80 N
Good
Maximum tension force: 110
N

Whether it is possible to supply
the desired pressure to inside
the pipe

Verification of pressure resistance (0.2 MPa Must be able to withstand apressure of 0.2 MPa
supply)3.3

Good

20 mm or less

Test to verify extension/retraction
operations when the telescopic guide pipe Supplied pressure required foris inclined
extension
Tilt the telescopic guide pipe and verify the
maximum angle at which extension/retraction ispossible (max. 5 degrees)Good

Amount of tip
misalignment

3.1.2 With the telescopic guide pipe fully extended, apply section structure during
a horizontal load to each pipe joint and verify the
degree of tip misalignment

Tensile force during
retraction: 10 N to 80 N
Good
Maximum tension force: 110
N

Tensile force required frommaximum extension

With the telescopic guide pipe fully extended, apply
air pressure of 0.2 MPa for 2 hours, disassemble
and visually inspect for damage or deformation of Whether it is possible to supply
components such as the stopper rings at the pipe the desired pressure to insideends
the pipe

Air pressure required 0.1 MPa or less0.03 MPa or lessduring extension
There was no difference
Difference between
between the supplied
supplied pressure and No significant
and the pressure
the pressure inside the pressure difference pressure
inside the telescopic guidetelescopic guide pipe
pipe
Whether main
No deformation
components areor after 0.2
deformed 2 hours after before
MPa supply
supplying 0.2 MPa

Good

Good

There was no deformation ofGood
the main load-bearing
components

Even at 0.2 MPa, there was
Difference between
no difference between the
supplied pressure and No significant
Goodpressure and thethe pressure inside the pressure
difference supplied©International ResearchInstituteinside
for Nuclear
pressure
theDecommissioning
telescopic guide pipe
telescopic guide pipe

6. Implementation details

Units 2 and 3

No.101(2) Development of the bottom access investigation method (telescopic pipe)3) (c) Test to verify the effect of proposed countermeasures <3. Section verification test>
Comparison of the section verification test results (extension/retraction operations verification) fortelescopic guide pipe base section (1st to 3rd stages)(FY2020 test manufacturing / FY2021 improved test manufacturing)
✓

✓

✓
✓

It was verified that, by applying measures to reduce sliding resistance, the telescopic
guide pipe can be extended with less pressure and retracted with less cable tension
force.
In the test manufacturing of FY2020 telescopic guide pipe, the pressure in the pipe
was less than the source pressure, but in the test manufacturing of FY2021 improved
model, the pressure was the same, verifying the effectiveness of measures to reduceleakage volume from the sealing section.
It was also verified that the telescopic guide pipe can be extended and retracted evenat a greater inclined angle (previous fiscal year: 3° ⇒ this fiscal year: 5°)
It was thought that the telescopic guide pipe would be retracted by negative internalpressure in cases of cable winder malfunction but the test manufacturing of FY2021
improved model can be retracted solely by its weight, at an internal pressure of 0.004
Mpa.

During retraction
During extension
Test manufacturing of FY2021 improved
telescopic model (3-stages on the base side)

The above results verified the effectiveness of the proposed countermeasures.
FY2020

FY2021

Supplied pressure (pressure
inside telescopic guide pipe)

0.040 MPa0.030 MPa

Source pressure

0.050 MPa0.030 MPa

Air pressure during retraction

0.005 MPa0.010 MPa

Tensile force during retraction

50 N to 130 N

10 N to 80 N

3 degrees

5 degrees (expected
operational upper limit)

Compared items
During extension (telescopic
vertical)During retraction (telescopic
vertical)Telescopic inclined angle at which extension/retraction ispossible©International Research Institute for Nuclear Decommissioning6. Implementation details

Units 2 and 3

No.102(2) Development of the bottom access investigation method (telescopic pipe)

ExtendedlengthExtension
range
Cable tension
force

Retraction
range

Extended length [mm]FullyextendedUpper tension limit:
208 N

Rated tension force:
83 N

Tensile force during
retraction: roughly in therange of 50 N to 130 N
Time [s]Supplied pressure [kPa]<3. Section verification test>
Momentary force: 220 N(Assumed snagging on the
inner pipe surface)

Tensile force [N]3) (c) Test to verify the effect of proposed countermeasures
Test results of extension/retraction operations for the test
manufacturing of FY2020 telescopic guide pipe

Fully
retracted

Issue ①:
The cable tension force intermittently
exceeds the rated tension force. There may
be cases of overload and motor shutdown,
exceeding upper tension force limit.

Supplied pressure (pressure insidetelescopic guide pipe)

Issues ②:
The telescopic extension operation
increases the volume in the pipe anddecreases the pressure in the telescopic
guide pipe, but it takes time to return to thesource pressure due to high leakage.

When extended, supply pressure was set to
30 kPa to 40 kPa, and applied sourcepressure: 30 to 50 kPa

Time [s]The telescopic guide pipe was operated with supplied pressure of 5 kPa
when retracted©International Research Institute for Nuclear Decommissioning6. Implementation details

Units 2 and 3

No.103(2) Development of the bottom access investigation method (telescopic pipe)3) (c) Test to verify the effect of proposed countermeasures
Test results of extension/retraction operations for the test
manufacturing of FY2021 improved telescopic guide pipe
Retraction
range

Momentary force:
110 N

Extended length [mm]FullyextendedTensile force during
retraction: roughly in therange of 10 N to 80 N

Time [s]Supplied pressure [kPa]Fully
retracted

Supplied pressure when
extended: 30 kPa
Source pressure: 30 kPa

ExtendedlengthCable tension force
Tensile force [N]Extensionrange<3. Section verification test>

Supplied pressure whenretracted: 10 kPa

Time [s]Upper tension limit:
208 N

Rated tension force:
83 N

Operated at the same extension
and retraction speed as the test
Supplied pressure (pressure inside manufacturing of FY2020
telescopic guide pipe (extension:telescopic guide pipe)
20 mm/s, retraction: 5 mm/s).
When the pressure decreased due
to extension operation, the time toreach the desired pressure (30kPa) was shorter than that of thetest manufacturing of 2020
telescopic guide pipe.
The tension force during retraction
could be kept within a range
roughly equal to or less than the
rated tension force of the cablewinder.
©International Research Institute for Nuclear Decommissioning6. Implementation details

Units 2 and 3

No.104(2) Development of the bottom access investigation method (telescopic pipe)(4) (d) Conceptual study and simplified test for development issues: Development plan formulated last
fiscal year
Red: Items to be verified by testing in FY2021
Blue: Items related to specifications of the access equipment under development in other projects

No. 2: Attachment anddetachment operation method,verification of specifications

Enclosure for fuel debris retrieval

No. 3: Examination of basic
structure
No. 4: Understanding
extension/retraction behavior
No. 5: Understanding
characteristics ofextension/retraction operations

Investigationequipment (pantilt camera)
Composite cablefor investigationequipment(dotted line)

No. 8: Exterior design of investigationequipment
No.11: Measures against adhered objects
on the camera and lighting
No. 12: Visibility

No. 9: Cable design

Telescopic guide pipe

No. 1: Verification of detailed specifications of arm-typeaccess equipment for retrieval
Arm-type access equipment for fueldebris retrieval

No. 13: Operability
Wrist section pan tilt
cameraCable winder

No. 6: Design of cable winding
mechanism
No. 10: Noise reduction method

No. 7: Design of postureadjustment mechanism

The feasibility of the unit of telescopic access equipment wasevaluated in FY2020 and FY2021.
©International Research Institute for Nuclear Decommissioning6. Implementation details

Units 2 and 3

No.105(2) Development of the bottom access investigation method (telescopic pipe)4) (d) Conceptual study and simplified test for development issues: Development issues and action policy 1/2
No. Major items

1 Access
equipment
into thepedestal
2

Intermediate
items

Minor items
Verification of detailed
specifications of armtype access equipment
for retrieval

Verificationofconnection
with the armtype accessequipment Attachment andfor retrieval detachment operation
method, verification of
specifications
Examination of basic
structure3

Development issues

FY2021 action policy

FY2021 test/implementation items- Tip positioning accuracy- The information that contributes to the study of- Arm deflection/oscillation- Range of motion of each axis
equipment specifications is confirmed by the projectInterviewing from other projects
team of “Development of Technology for Further- Transportable weight- Arm external cable specifications
Increasing the Retrieval Scale of Fuel Debris.”- Emergency action policy- Verification of feasibility of procedures/transport casks - The information that contributes to the study offor transfer in and out of the enclosure
equipment specifications is confirmed by the projectInterviewing from other projects- Installation and removal methods using the maintenance team of “Development of Technology for Furtherarm
Increasing the Retrieval Scale of Fuel Debris.”- Design review- Structural feasibility under the dimensional constraints - The impact of environmental conditions on the
Verification test of the strength ofstrength of connecting parts depending on changes
imposed by use of an arm-type access equipment forthe connecting part
retrievalof materials and more are understood by verification
tests of a prototype.
- Joint connection accuracy (pipe tilt)- Swaying during extension (investigation equipment
section)

Understanding
extension/retraction
behavior

4
Accessequipmentfrom inside
the pedestal
to inside theRPV

5Telescopic
accessequipment
designUnderstanding
characteristics ofextension/retraction
operations- Amount of tip misalignment (looseness/deflection) during - Design review- Behaviors of the proposed 3-stage telescopic pipe
vertical extensionthat is improved for the sliding resistance are
Verification test of parts⇒ (c)- Verification of extension/retraction behavior when
understood as information that contributes to the
Feasibility verification test of thetelescopic pipe is inclined
examination of equipment specifications.
14-stage telescopic pipe⇒ (e)- Verification of extension/retraction behavior when
- Verification of the 14-stage telescopic pipe
snagged (whether telescopic pipe can expand/retract
prototypewhen snagged, and whether telescopic pipe can retract
when investigation equipment is snagged)- Effects of adhered objects on extension/retraction
behavior- Design review- Required air pressure during extension- The sliding resistance of the seal under theassumed environmental conditions (dose and- Positioning control
temperature) and the effect on sealing efficiency are- Sliding resistance between air packing and telescopic
determined through test manufacturing verification.
pipe
Verification test of sealing function
This information contributes to the study of- Sliding resistance of telescopic rotation control guideequipment specifications to determine whether or ⇒ (c)Verification test of parts ⇒ (c)not to adopt the proposed countermeasures- Behaviors of the proposed 3-stage telescopic pipe Feasibility verification test of
the14-stage telescopic pipe⇒ (e)that is improved for the sliding resistance areunderstood as information that contributes to theexamination of equipment specifications.
- Verification of the 14-stage telescopic pipe
prototype©International Research Institute for Nuclear Decommissioning

Units 2 and 3

6. Implementation details

No.106(2) Development of the bottom access investigation method (telescopic pipe)4) (d) Conceptual study and simplified test for development issues: Development issues and action policy 2/2
No. Major items

Access6 equipmentfrom inside
the pedestal
to inside the
RPVIntermediate
items

Minor items

Development issues- Accuracy of wire tension force measurement (whether
slack can be detected)- Coordinated control of cable winding force and airpressure during telescopic extension and retraction

Telescopic
accessequipment
designDesign of cable winding- Limit detection
mechanism- Mechanical arrangement (X6 penetration passage, arminterference)

FY2021 action policy- Design review
Test to verify cable winder torque- Confirm improved cable winder torque throughimprovement
test manufacturing verification
14-stage feasibility verification test
- Test manufacturing verification using a 14-stage⇒ (e)telescopic pipe

- Pressure-resistant box design (approx. 0.1 MPa)
Design of posture- Mechanical arrangement (X6 penetration passage, arm
adjustment mechanism interference)
Exterior design of- X6 penetration, interference with reactor internals
investigation equipment

78- Diameter reduction (target: Φ6 or less)- Tensile strength9

Cable design

10

Noise reduction method - Noise during rotation when using slip rings (dosimeter)- Design review

Theoretical study- Design review

Theoretical study- Design review

Theoretical study- Design review- Evaluation of dosimeter noise using slip rings

Slip ring noise evaluation

Investigation
Investigationequipment
equipment
Measures against
design- Effects of water droplets and adhered objects, etc. on the11adhered objects on the- Design review
camera and lighting
camera and lighting

Visibility

Operability

Operability with camera- Whether the operational situation (such as contact withstructures) can be determined clearly enough, byinvestigation equipment/wrist section camera, to enable
operation- Design review

Theoretical study

Emergency
response- Response to power cutoff (disconnection, etc.), control
Examination of items to
failure (software excursion), control line disconnection, etc.
- Design review
be expected in case of- What kind of events, such as seismic activities andemergency
blackouts, should be expected?

Theoretical study

Others
14

Theoretical study- Verification of long-distance visibility when there is- Design review
machinery/structures near the camera (halation problem)- Evaluation of camera visibility for consideration Evaluation of camera visibility- Understanding characteristics of visibility deteriorationof CMOS camera adoption
due to radiation dose

12

13

FY2021 test/implementation items©International Research Institute for Nuclear Decommissioning

Units 2 and 3

6. Implementation details

No.107(2) Development of the bottom access investigation method (telescopic pipe)4) (d) Conceptual study and simplified test for development issues<1, 2 Verification of connection with arm-type access equipment for retrieval>
Telescopic guidepipe

Alignment
mechanism

Cable for investigationequipment

Cable drum

Replacement
range

Retrieval arm
Replacement

Posture change
Cable winder
Telescopic guide pipe
(14-stage)
Investigation equipment

Vertical posture (postureduring investigation)©International Research Institute for Nuclear Decommissioning

Units 2 and 3

6. Implementation details

No.108(2) Development of the bottom access investigation method (telescopic pipe)4) (d) Conceptual study and simplified test for development issues<1, 2. Verification of connection with arm-type access equipment for retrieval>
In meetings with other project teams, RPV interior investigation equipment isbeing adjusted to specifications for installation to replace the wand. In regards toretrieval arms, it will be necessary to feedback on detailed specifications inreference to various design and evaluation information.
〇 Main future verification items- Arm wrist posture of the expected investigation equipment (just below the
opening)- Minor adjustment accuracy and vibration of the arm- Interference between inner wiring connector and 14-axis actuator- Automatic attachment/detachment method for outer wiring- Others
Items.

Carriage ① Forward/backward 0 to 6.9 m ② Lift ±50 mm ③ Tilt 2 to 3° ④ Roll ±0.5°
Boom link 1: ⑤ No movement required, ±60°
Boom link 2: ⑥ -90 to 0゜
Boom link 3: ⑦ 0 to 180°
Boom link 4: ⑧ -180 to 0゜
Boom link 5: ⑨ 0 to 180゜
Telescopic arm⑩ -127.5 to 12.5゜⑪ Tilt: -20 to 5゜⑫ Extension 0 to 2.1 m
Horizontal offset link: ⑬ -27.5 to 152.5°

Wrist:⑭ -135 to 45゜⑮ -130 to 45゜
Wand⑯ 0 to 2.8 m(extension + forward)
Tool pan & tilt:⑰ Roll ±90°
⑱ Tilt ±110°

Specifications.

Tip positioning accuracy±50 mm or lessRange of motion of retrieval arm

Arm deflection

140 mm or less
Boom link tip: approx. 80 mm or less
Single telescopic arm: approx. 60 mm or lessOuter wiring

Arm vibration±10 mm (within 5 minutes: target value)* Detailed survey arm result

Range of motion of each axis

See figure on the right

Wrist axis
carrying
capacity

Transportable weight 40-45 kg (Wand: 25-30 kg, Tool: 15 kg)
Allowable torque1263 Nm

For wand (inside)

Twisted pair: 18 Pair ( 36 core)
Parallel: 24 core

For tools (outside)

Control cable: 3 ( 20 core, 8core,
2 core)Motor cable: 1 (16 core)Coaxial cables: 8
N2hose: 2 hoses (O.D. 6 mm ×I.D. 4 mm)
Water hose: 1 ( O.D. 6 mm ×I.D. 4 mm)

Cable
specifications

Emergency action policy

Cut the wand and throw it into the pedestal

Types
Survey camera control(camera, lighting, pan & tilt)

Custom D-sub 62 pin
N2: 2 units

Dosimeter
Control of cable winding
N2

Inner wiring
Types
Survey telescopic pipe
forward/backward control
Custom D-sub 62 pin
RPV interior investigation equipment

Survey telescopic pipe attitudecontrol (α axis)
Survey telescopic pipe attitudecontrol (β-axis)

Cable specifications (outer, inner wiring)©International Research Institute for Nuclear Decommissioning

Units 2 and 3

6. Implementation details

No.109(2) Development of the bottom access investigation method (telescopic pipe)4) (d) Conceptual study and simplified test for development issues <3. Examination of basic structure>
Consideration of adopting aluminum as an alternative pipe material
CFRP (inner and outer UD
surface)

Aluminum (A7075)

Φ100 (1st stage) toΦ35 (14th stage)

Manufacturable

Manufacturable

431.5 mm (1st stage) to658.2 mm (14th stage)

Manufacturable

Manufacturable

14

Manufacturable

Main target specifications
Pipe outer diameter
Pipe length
Number of pipe stages
Pipe thickness

1 mm or lessOuter diameter tolerance+0.2/0 mm

Inner diameter tolerance

H9
1st stage: Φ95 +0.087 to 0
13th stage: Φ35 +0.062 to 0

Operability

Linearity

0.1 mm or lessRoundness

0.2 mm or less

Inner surface roughness

Ra 3.2 or less1.6 (actual result)0.3 (actual result)

Tensile strength (axial
direction)

100 MPa or more

Pipe stages 2 to 9: 796 MPa
Pipe stages 10 to 14: 618 MPa

570 MPa

Tensile strength(circumferential direction)

100 MPa or more

Pipe stages 2 to 9: 603 MPa
Pipe stages 10 to 14: 129 MPa

570 MPa

CFRP: High-strength pre-preg (*1) cannot be used for stages 10 to 14
because of the small pipe diameter, so circumferential tensile strength
is low

Safety factor (0.3 MPapressure resistance)

15 or higher

Pipe stages 2 to 9: 45
Pipe stages 10 to 14: 20

38

CFRP: High-strength pre-preg(*1) cannot be used for stages 10 to 14
because of the small pipe diameter, so the safety factor is low, but not
low enough to be an issue

10 mm or less
Looseness of each stage notincluded

2.0 mm

3.4 mm

Structural analysis assuming zero looseness (adhesion condition) for
each telescopic stage

9 kg or less

8.0 kg

9.4 kgInvestigation equipment not included
Excluding pipes; scrapers, pistons, stopper rings, etc. included

7200 Gy or higher

7200 Gy or higher

7200 Gy or higher

1 or more surveys possible

Required evaluation

Required evaluation

Deflection

Robustness

Since manufacturing issues were expected with the CFRP pipe, a 3stage aluminum tip was test-manufactured as an alternative

Manufacturable
Aluminum is difficult to manufacture with 1 mm wall thickness, andDifficultto guarantee shape only one company accepted the order under target precision
Manufacturable
tolerance
conditions (test manufacturing), so the evaluation was performed on
the test manufacturing of a thin pipe (12th, 13th, and 14th stages:
Manufacturable
Manufacturable
inner diameter Φ40 to Φ30 test manufactured), which is difficult to
Difficult to guarantee accuracy
make more rigid with CFRP. Result: approx. 0.3 mm warp in the 13th
After manufacturing at +0.4/0stage, preventing full retraction into the 12th stage.
mm, match up the components
Manufacturable
that join together (pistons, etc.)
The previously manufactured aluminum telescopic pipe (investigationin order to adjust theirinside the 1F2_PCV (A2)) has a 2.5 mm wall thickness. With thisdimensions
thickness, if the maximum outer diameter is less than Φ100, only a 7Processing difficulties
stage structure can be made, which has insufficient reach even at full
Manufacturable
13th stage actual result: 0.3 extension (cannot access the bottom of the reactor)mm
Manufacturable
Manufacturable

Strength

WeightRemarks

14-stage weight
Cumulative dose
resistanceAbrasion/repeatability

3 days or more at 100 Gy/h

*1: Pre-preg: A sheet-like intermediate material in which carbon fiber, etc., is pre-impregnated with resin.
Pre-pregs are laminated to form the product.

There is an issue in manufacturing (processing) for adopting aluminum.
©International Research Institute for Nuclear Decommissioning

Units 2 and 3

6. Implementation details

No.110(2) Development of the bottom access investigation method (telescopic pipe)4) (d) Conceptual study and simplified test for development issues <7 Design of posture adjustment mechanism>〇 Posture adjustment mechanism
Due to the degree of freedom of the retrieval arm, it may be difficult to set the
RPV interior investigation equipment in a vertical position at the expected survey
location. Therefore, installation of a 2-axis posture adjustment mechanism on thesame side of the RPV interior investigation equipment was considered.
〇 Specifications of posture adjustment mechanism
Forward/backward
drive
Range of motion

α-axisβ-axis

581 mm or greater

13° or more

20 mm or more

Positioning accuracy±1 mm or less±0.01° or less

±1 mm or less

Weight (kg)

8 kg or less

7 kg or less

5.5 kg or lessSize (mm)

W: within 1100 mm
H: within 400 mm
D: within 150 mm

W: within 600 mm
H: within 250 mm
D: within 200 mm

W: within 430 mm
H: within 150 mm
D: within 200 mm

Dose rate (Gy/h)

100

100

100

Cumulative dose
(Gy)

7200

7200

7200

Radiation
resistance

β-axis mechanism
α-axismechanism

Cable winding
Telescopic
Survey camera

Forward/backward mechanism

Extending the verticalscope of RPV interior
investigation
Arm for increasing theretrieval scale

Moving the RPV interior

Upper grating surface

investigationequipment forward
Tilt angle adjustmentα, β axis adjustment

Telescopic posture adjustment mechanism©International Research Institute for Nuclear Decommissioning

Units 2 and 3

6. Implementation details

No.111(2) Development of the bottom access investigation method (telescopic pipe)4) (d) Conceptual study and simplified test for development issues <7. Design of posture adjustment mechanism>

α-axis mechanism:
angle adjustment

α-axis operation

Linear motion
mechanism
Linear motion
mechanism
drive motor

α-axis link

β-axis mechanism:
horizontal offset adjustment
Ball screw
Horizontal fineadjustment motor
Worm gear

Linear guide©International Research Institute for Nuclear Decommissioning

Units 2 and 3

6. Implementation details

No.112(2) Development of the bottom access investigation method (telescopic pipe)4) (d) Conceptual study and simplified test for development issues<8. Exterior design of investigation equipment>

For investigation equipment, the policy is to use a camera with a pan/tilt drive shafts developed for the investigation inside thePCV. The investigation inside the PCV was carried out by suspending the cable for investigation equipment, but in thisinvestigation, the cable is used facing upward, so countermeasures to address issues arising from the difference in orientation wereconsidered.
The umbrella component served to prevent the investigation equipment from getting caught on structures during the investigation
inside the PCV, and to prevent dripping reactor cooling water from splashing on the camera and drive unit. In this investigation, thesame functions can be expected in terms of preventing snagging, but there is a risk of dripping water accumulating inside theumbrella component. Expecting that water will accumulate in the camera lens section and lighting hood, it was decided to provide
drainage holes and slits. In addition, when used in the upward direction, there is a risk of water intrusion into pan/tilt drive shafts
and joints of combined components. A policy of devising countermeasures such as sealing reinforcement and mold treatment foreach component was adopted.

Investigation equipment specifications
Items
Outer
dimensions
WeightMountedcameraDrainageholes(4 directions)

Drainage slits(4 directions)① Tilt section② Camera③ LED lighting
extension④ Pan section

Lighting hoodLens hood
Umbrella component

Lighting
Visiblerange

Mountedsensors
Radiation
resistanceSpecifications
Φ84 [mm] × L210 [mm]0.7 [kg]
Color CCD camera or color CMOS camera
LED lighting (10 [W] x 1, variable distance
between camera and optical axis, maximum 105[mm])
238[°] (vertical angle of view 17.8[°] + tilt 110[°],pan ±180[°])
Dosimeter (1 [Gy/h] to 2000 [Gy/h] measurable),thermometer (0 to 50 [℃], accuracy ±0.5 [℃](obtained as reference information))
1000 [Gy] (from radiation resistance of CCD
camera)©International Research Institute for Nuclear Decommissioning

Units 2 and 3

6. Implementation details

No.113(2) Development of the bottom access investigation method (telescopic pipe)4) (d) Conceptual study and simplified test for development issues<9. Cable design>

In order to extend the telescopic guide pipe to its maximum length, the cable must be wound for 6.1 m + winding allowance(approx. 700 mm) with a small cable winder. In FY2020, a thinner cable was designed, with a permissible bending radius of
R35 mm or less so that it can be wound by a Φ70 mm cable drum of a small cable winder. On the other hand, since theextension/retraction operation test of the 3-stage telescopic guide pipe revealed that the cable needs to be pulled with a force
of about 270 N, which is larger than expected when the cable is pulled to retract the telescopic guide pipe, an improved
design to increase the cable's tensile strength was implemented this year.
Camera options for inclusion in the investigation equipment include CMOS and CCD cameras, so both cables wereconsidered. The diameter of a cable was reduced to a level that allows it to be wound up to the required length with a small
cable winder, and a cable with a tensile strength of 750 N was designed.

Cable specifications
Items

Diameter

Required
specifications

Target
6 mm orless

Designresult forCMOS

5.8 mmDesignresult forCCD

6.5 mmCoaxial cable
Remarks
If CCD cable isused, verificationis necessary
because it may bepossible to wind
the required length
to 8 mm

Green
Ash

Numberof cores

CMOS
29 single
wires
1 coaxial
cable
CCD
29 single
wires
4 coaxial
cables

750 N

750N

FY2020 design is
250 N

Red

Purple Blue

PurpleGreen

Yellow

Brown

Brown

Red

Blue

Orange

Green

White
Ash Green

Blue

White

Orange

Blue
Brown

Sky

White

Green

Yellow

Yellow

OrangeRedBlue

29 single
wires
4 coaxial
cablesOrange Red

Black

Red

White

29 single
wires
1 coaxial
cable

PurpleYellow Brown

Green

Brown

PurpleOrange

Blue

Brown

Yellow

Yellow

Red

270 N orgreaterRed
OrangeBlue

Blue

Tensilestrength

Orange Yellow GreenBlack Brown Red

Peach Black

Green

Red

OrangeGreen Yellow

Blue
Brown

White

Tension members―

Cross section view of CMOS
camera cable

Cross section view of CCD
camera cable©International Research Institute for Nuclear Decommissioning

Units 2 and 3

6. Implementation details

No.114(2) Development of the bottom access investigation method (telescopic pipe)4) (d) Conceptual study and simplified test for development issues<10. Noise reduction method: Evaluation of dosimeter noise using slip rings>〇 Purpose
Since the dosimeter to be used needs to transmit a very small current, it tends to generate noise and leakage
current in areas with mechanical contacts such as connectors, where the electromagnetic shield is locallydiscontinuous. In particular, because slip rings contain rotating electrodes and are considered relatively vulnerable
to noise, tests to verify noise effects will be conducted.
〇 Test overview① The effects on electromagnetic noise are verified when the cable drum drive motor operates near the slip ring
② The selected dosimeter element is connected through a slip ring and verify the effects of noise and leakage
current.
A slip ring is placed close to the motor part.

Power line

Distribution
board fortesting

Noise cuttransformer

Motor
controlpanel

Dosimeter
controller
Dosimeter cable

Noise filter

Slip ring

Telescopic
drum motor

Dosimeter

Telescopic
pipe©International Research Institute for Nuclear Decommissioning

Units 2 and 3

6. Implementation details

No.115(2) Development of the bottom access investigation method (telescopic pipe)4) (d) Conceptual study and simplified test for development issues<10. Noise reduction method: Evaluation of dosimeter noise using slip rings>〇 Test results① Electromagnetic noise was effected when the cable drum drive motor operates near the slip ring.
◆ When acquiring data under conditions where the dosimeter does not output a measurement signal, the motor
was driven at 100% load.
➢ Dosimeter controller output became unstable and an abnormal current value (instrument over-range) wasrecorded.
➢ It was verified that occurrence of an abnormal current value was suppressed by use of a noise filter in thedosimeter signal transmission line.

It was verified that the effects on electromagnetic noise can be suppressed by using a noise filter.
② The selected dosimeter element was connected through a slip ring to verify the effects of noise and leakage current.
➢ With a simulated measurement signal (10 nA; equivalent to 20 [Gy/h]*) flowing through the dosimetertransmission line, the dosimeter cable and slip ring were inserted into the transmission line and the effects were
*The conversion factor is diverted from the calibration data collected during the investigation inside the 1F-2 PCV
verified.
➢ It was verified that the leakage current generated by the cable and slip ring is about 0.03 nA (equivalent to 0.06
Gy/h*).

It was verified there is no problem in the leakage current since it is a small amount compared to the
expected environmental dose of 100 Gy/h.
Effects of electromagnetic noise on motor operation

Condition 1

Dosimeter
controller

NoisefilterCondition 2

Dosimeter
controller

Noisefilter

Dosimeter

Condition 3

Dosimeter
controller

NoisefilterSlip
ring

Test conditions

Current value [nA]

Leakage current
value [nA]

Condition 1

10.055― (standard)

Condition 2

10.0350.020

Condition 3

10.0280.027

Dosimeter

Dosimeter controller output
current value [nA]

Verified irregular electromagnetic noise (instrument over-range)
No filter
FilterUse of a noise filter suppresses the occurrence of abnormal currents

Motor operating time [s]Dosimeter©International Research Institute for Nuclear Decommissioning6. Implementation details

Units 2 and 3

No.116(2) Development of the bottom access investigation method (telescopic pipe)4) (d) Conceptual study and simplified test for development issues<11. Measures against adhering objects on cameras and lighting>From results of previous investigations inside the PCV, it was verified that the surfaces of structures inside the PCV
are covered with foreign substances such as mud and sand. Since the investigation equipment is mounted in an
upward-pointed position on the telescopic access equipment to access into the inside of the RPV, foreign substancesfrom structure surfaces may adhere to the camera and lighting when the investigation equipment is in motion,
impairing visibility.
A new mechanism such as a wiper could be incorporated, but to drive the actuator, the number of cable cores forthe investigation equipment needs to be increased. This would increase cable diameter, and the cable winder would
not be able to wind the length of cable needed for telescopic guide pipe extension.
Therefore, as measures to remove adhered objects, the operational policy is to wash it away with cooling water thatdrips from the furnace, and if necessary, to tilt the investigation equipment so that the camera and lighting are at anangle that causes the objects to fall off.

① Tilt section② Camera③ LED lighting extension④ Pan section©International Research Institute for Nuclear Decommissioning

Units 2 and 3 No.117

6. Implementation details(2) Development of the bottom access investigation method (telescopic pipe)4) (d) Conceptual study and simplified test for development issues<12 Evaluation of camera visibility in consideration of CMOS camera adoption>〇 Purpose
For the purpose of adopting CMOS cameras for thinner cables, the visibility is evaluated in foggy and radiatedenvironments.
〇 Test overview
In a foggy environment, visibility is evaluated when light transmittance varies due to changes in fog concentration.
In addition, by radiation resistance testing, evaluate the effects of radiation noise on dose and the effects ofcumulative doses of 1000 Gy or more.
Monitoringroom(No fog)

Fog chamber
Transmittance
Monitor + recording
component

Recording distance

Recordingcomponent

CCU

Monitoringroom

CCD camera

Irradiation chamber

CameraDistance to source(dose rate)
SourceTest chartor testpiece

LightingPowersupplyequipment

CCU

500 mmTest chart ortest pieceLighting controller

CMOS camera

Proposed system for foggy environment testingExternal lighting

Proposed system for radiation resistance testing

Dose rate meter
CCD camera CMOS camera
External lighting

Guiding system performance test

CMOS·CCD
CameraExternal
lighting

Guiding system performance test
©International Research Institute for Nuclear Decommissioning

Units 2 and 3

6. Implementation details

No.118(2) Development of the bottom access investigation method (telescopic pipe)4) (d) Conceptual study and simplified test for development issues<12 Evaluation of camera visibility in consideration of CMOS camera adoption>〇 Foggy environment test results

Foggy environmental condition (estimated value at Unit 1 of Fukushima Daiichi Nuclear Power Station): Absorption coefficient 0.511
An absorption coefficient of 0.511 gives a transmittance of approx. 21.6% at a distance of 3000 mm. In this evaluation, a transmittance of 20%/3000 mm
is evaluated as equivalent to a transmittance of 0.511

Distance to object [mm]
1000

2000

3000

4000

Simulated fuelrod Φ10 mm
Beforeimage
processing

CMOS

Landolt ring
Opening 20 mm
After image
processing

Beforeimage
processing
CCD

After image
processing

It was verified that that Landolt rings (20 mm opening) can be observed at up to 4000 mm, and simulated fuel rods
(Φ10 mm) at up to 2000 mm by using both the CMOS and CCD cameras.
⇒ There was no difference of visibility between CMOS and CCD cameras in a foggy environment©International Research Institute for Nuclear Decommissioning

Units 2 and 3

6. Implementation details

No.119(2) Development of the bottom access investigation method (telescopic pipe)4) (d) Conceptual study and simplified test for development issues<12 Evaluation of camera visibility in consideration of CMOS camera adoption>〇 Radiation resistance test results (effects of dose rate)
Dose rate (Gy/h)
0 (unirradiated)

150

590

1850

CMOS

CCD

It was verified that video output was possible up to 1850 Gy/h, although both the CMOS and CCD cameras
generated noise due to radiation.
⇒ There was no difference in visibility (dose rate effects) between CMOS and CCD cameras in a radiation
environment.

©International Research Institute for Nuclear Decommissioning

Units 2 and 3

6. Implementation details

No.120(2) Development of the bottom access investigation method (telescopic pipe)4) (d) Conceptual study and simplified test for development issues<12 Evaluation of camera visibility in consideration of CMOS camera adoption>〇 Radiation resistance test results (effects of cumulative dose, conducted only with CMOS cameras)

External
lighting
1100lx

Before test

During irradiation

UnirradiatedDose rate: approx. 1850 Gy/hDuring irradiation(immediately before theend of the test)
Cumulative: 1600 Gy or more
Dose rate: approx. 340 Gy/hAfter test
Cumulative: 1600 Gy or more
Unirradiated✓ After an irradiation test with a cumulative dose of at least 1600 Gy was conducted, and output of video images was verified.
The CCD camera was tested in the same way as in the past investigation inside the PCV, and the contrast decreased after 1100
Gy irradiation✓ After irradiation, an event that video images were distorted in low light intensity was verified.
It is estimated that the gain control section of the camera was damaged due to the irradiation.
⇒ It is necessary to conduct an impact assessment on investigations of the cumulative dose that causes video distortions in low
light intensity, and video alterations due to the cumulative dose

Laboratory
lighting
36lx

Before test

After test
©International Research Institute for Nuclear Decommissioning

Units 2 and 3

6. Implementation details

No.121(2) Development of the bottom access investigation method (telescopic pipe)4) (d) Conceptual study and simplified test for development issues<12 Operability with camera>〇 Purpose
The purpose of investigating inside the RPV is to verify the visibility-ensuring camera mechanism and its
operational method, by means of a simulator that allows to verify simulated reactor interior images.
〇 Study outline
Two simulated video images (object display and overhead view from a fixed point) are acquired
simultaneously from the camera mounted on the arm access equipment for retrieval (fixed point camera)
and the camera mounted on the investigation equipment (moving camera).
Moving camera
Perspective
4
Fixed point camera

Moving camera

Telescopic
guide pipe +movingcameraFixed point
camera image

Perspective
3

Moving camera
image

Perspective
2

Perspective
1

Fixed point camera

3D model of the structure used
©International Research Institute for Nuclear Decommissioning

Units 2 and 3

6. Implementation details(2) Development of the bottom access investigation method (telescopic pipe)4) (d) Conceptual study and simplified test for development issues
Moving camera image

Fixed point camera
image

No.122<12 Operability with camera>
Overhead view images(lighting ON)

Overhead view images(lighting OFF)

Simulated images andoverhead view at eachsimulator perspective(Unit 2)

Unit 2

Perspective 4

Perspective 3

Perspective 2

Perspective 1©International Research Institute for Nuclear Decommissioning6. Implementation details

Units 2 and 3

No.123(2) Development of the bottom access investigation method (telescopic pipe)4) (d) Conceptual study and simplified test for development issues
Moving camera image

Fixed point camera
image<12 Operability with camera>
Overhead view images(lighting ON)

Overhead view images(lighting OFF)

Simulated images andoverhead view at eachsimulator perspective(Unit 3)

Unit 3

Perspective 4

Perspective 3

Perspective 2

Perspective 1©International Research Institute for Nuclear Decommissioning6. Implementation details

Units 2 and 3

No.124(2) Development of the bottom access investigation method (telescopic pipe)4) (d) Conceptual study and simplified test for development issues<13 Examination of items to be expected in case of emergency>

The equipment placed inside the PCV for the investigation should be collected in the enclosure after the investigation iscompleted in a way that ensures that the isolation valve installed between the enclosure and the PCV can be closed. How tocollect or otherwise deal with the equipment that fails to operate properly during the investigation was examined.
Possible equipment problems that would make equipment collection difficult are listed below. Note that the problems with thearm-type access equipment for retrieval are not included here, since that equipment is being studied and developed in a
separate project.
No.
1

Expected troubles
The telescopic guide pipe is retracted by winding the cable through the inside of
the investigation equipment, but the cable winder cannot be driven due toirregular winding or drive motor burnout, and the telescopic guide pipe cannot be
retracted.

2

The cable for investigation equipment inside the telescopic guide pipe broke, andthe telescopic guide pipe can not be retracted. At this time, the telescopic pipe isfully extended.

3

The cable installed on the exterior of the retrieval arm came into contact with astructure and broke, or the cable connector had poor contacts, and the cablewinder does not function and can not be retracted.

4

Due to a cable winder control software excursion, the telescopic guide pipe can
not be extended or retracted as intended.

5

Telescopic guide pipe and investigation equipment got caught on surrounding
structures, and the telescopic guide pipe cannot be retracted.

6

The structures inside the PCV are covered with powdery and muddy foreign
substances, which adhere to the outer surface of the telescopic guide pipe, and it
cannot be retracted.

7

Camera failure or foreign substances adhering to the camera prevents theacquisition of images necessary for equipment operation.

Basic response policy
By creating negative pressure inside the telescopic guidepipe, it is retracted by air pressure.
⇒ (e) Feasibility verification test using the 14-stage
telescopic guide pipe
By creating negative pressure inside the telescopic guidepipe, it is retracted by air pressure.
⇒ (e) Feasibility verification test using the 14-stage
telescopic guide pipe
By creating negative pressure inside the telescopic guidepipe, it is retracted by air pressure.
⇒ (e) Feasibility verification test using the 14-stage
telescopic guide pipe
Stop the control of the cable winder, and by creating
negative pressure in the pipe, it is retracted by air pressure.
⇒ (e) Feasibility verification test using the 14-stage
telescopic guide pipe
Verify by testing to see if it actually causes a problem.
⇒ (e) Feasibility verification test using the 14-stage
telescopic guide pipe
Verify by testing to see if it actually causes a problem.
⇒ (e) Feasibility verification test using the 14-stage
telescopic guide pipe
Verify during the mockup test whether the collection can be
performed using only one of the images from theinvestigation equipment camera and the overhead view
camera (mounted at the end of the arm-type accessequipment for retrieval).
©International Research Institute for Nuclear Decommissioning

Units 2 and 3

6. Implementation details

No.125(2) Development of the bottom access investigation method (telescopic pipe)4) (d) Conceptual study and simplified test for development issues<13 Examination of items to be expected in case of emergency>

The following policies were adopted to deal with cases where retraction by cable
winding is not possible, as in the cases of expected problems 1 to 4.
〇 Policy 1: By creating a negative pressure inside the telescopic guide pipe, it is fully
retracted by air pressure and is collected inside the enclosure by the normal
procedures.
〇 Policy 2: If total retraction cannot be achieved via Policy 1 and the isolation valve
cannot be closed even after collected in the enclosure, the telescopic accessequipment should be cut off and discarded inside the PCV using the cutting mechanismon the arm tip of the arm-type access equipment for retrieval, and only the arm-typeaccess equipment for retrieval should be collected in the enclosure. At this time, theequipment should be moved to a location outside the pedestal (where it would notinterfere with future operations) by the arm-type access equipment for retrieval, andthen be cut and discarded.

〇 Policy 3: If the telescopic guide pipe interior cannot be negatively pressurized due toan air tube rupture, etc., and the telescopic guide pipe cannot be pulled out below thelower end of the CRD, it should be cut and discarded on the spot. This means that thetelescopic access equipment will remain inside the pedestal.

Policy 1: The telescopic guide pipe isretracted by air pressure by creating anegative pressure in the pipe, and collectedby normal procedures.

Telescopic
guide pipe

Enclosure for fueldebris retrieval

Arm-type access equipment forfuel debris retrieval

Policy 2: Negative pressure is createdinside the telescopic pipe to retract it via airpressure and then it is cut and dumped
outside the pedestal.

Enclosure for fueldebris retrieval

Arm-type access equipment
for fuel debris retrieval

Cut t i ng/ dumping
Telescopic guide pipe

Bolt hole for fixing wandin place

Policy 3: Cut the telescopic guide pipe in its
extended state and dump it in the pedestal.

Wand
Frangibolt
Pin hole for fixing
wand in place

Enclosure for fueldebris retrieval

Connection to wandHorizontal offset link

Wrist

Wrist

Telescopic
guide pipe

Arm-type access equipment
for fuel debris retrieval

Cable cutter

Overview of the cutting mechanism
C u t t i n g/ d ump i ng

©International Research Institute for Nuclear Decommissioning

Units 2 and 3

6. Implementation details

No.126(2) Development of the bottom access investigation method (telescopic pipe)5) (e) Feasibility verification test using the 14-stage telescopic guide pipe

〇 Test system

Observation
cameraInvestigationequipment
mockupObservation camera/plumb bob
installation height

4th level ofscaffolding

3rd level ofscaffolding

Cable for simulated
investigation equipment

Sealing
sectionstructure

Telescopic guide pipe
(14-stage)

Approx. 5900
Approx. 5900 mm
mm

Simulated opening
installation height

Investigationequipment mockup

Observation
camera2nd level ofscaffolding

Pressure
indicator

Vacuumgenerator

1st level ofscaffolding

Alignment
mechanism
Cable drum

Limit switch to confirm home
position

Telescopic
guide pipe

Plumb bob

Cable winder

Laser
rangefinder

Pressure
indicator

Test piece for verifying telescopic guide pipe
extension/retraction operations

Electro-pneumatic
regulator

Regulator withfilterBuilding air
Electromagnetic
control valve

Direct acting Electromagnetic
3-port valve control switching valve

Test system©International Research Institute for Nuclear Decommissioning

Units 2 and 3

6. Implementation details

No.127(2) Development of the bottom access investigation method (telescopic pipe)5) (e) Feasibility verification test using the 14-stage telescopic guide pipe
〇 Test environment
The operator checks the telescopic guide pipe extension
status by direct visual observation as well as observation
camera video footage, and then operates the equipment
under the direction of the observer and conductor.
(Remote operation performance is not evaluated in this test)
Operation panel

Telescopic accessequipment

Telescopic accessequipment
Observation
camera monitor
Control
panel

Exterior view of the test site

Pneumatic
control panel

Operator

Operating condition©International Research Institute for Nuclear Decommissioning6. Implementation details

Units 2 and 3 No.128(2) Development of the bottom access investigation method (telescopic pipe)5) (e) Feasibility verification test using the 14-stage telescopic guide pipe

〇 Testing status

Full extension
During retraction

2nd stage pipe extension©International Research Institute for Nuclear Decommissioning6. Implementation details

Units 2 and 3 No.129(2) Development of the bottom access investigation method (telescopic pipe)5) (e) Feasibility verification test using the 14-stage telescopic guide pipe
〇 Test items
No.

1

Test items/outline

Test item: Verification of extension/retraction operations
Test overview: Verify if the telescopic guide pipe can be verticallyextended and retracted, and understand the characteristics ofvertical operation

Confirmation items

Cable tension required during
retraction

319 N or less

Supplied pressure required forextension

Air pressure required duringextension

0.1 MPa or less

Amount of swaying during telescopic
guide pipe extension

Accuracy of measurement of telescopic
guide pipe extended length2

3

Test item: Verification of extension/retraction operations when thetelescopic guide pipe is inclined
Test overview: The telescopic guide pipe is installed at an angle toverify the maximum inclined angle at which it can be extended andretracted (while the design limit angle is 5 degrees, the maximum
angle is set at 3.5 degrees in terms of margin)

Objective(evaluation criteria)

Tensile force required from maximum
extension

Whether the pressure in the pipe canbe adjusted to the target value

Test item: Verification of rigidity when horizontal load is applied
Test overview: In a fully extended telescopic guide pipe, ahorizontal load is applied to each pipe joint and the tip of thetelescopic guide pipe, in sequence from the base, to verify theamount of tip misalignment of the telescopic guide pipe.
(Measurement of misalignment is performed only when a load isapplied to the tip of the 14th stage pipe).

Evaluation items

Whether the telescopic guidepipe sways (if there is swaying,
the time it takes for swaying tostop after extension has
stopped)Difference between suppliedpressure and the pressure inside
the telescopic guide pipe
Value converted from theamount of drum rotation of thecable winder

No large amplitude(qualitative evaluation)―

Capable of adjusting thepressure in the pipe to thedesired pressure―

Verify the actual
performance―

Tilt control of each sealing section
structure during extension (loadapplied: 15 points)

Amount of misalignment at
50 mm or lessheight of reactor bottom opening

Tensile force required from maximum
extension

Cable tension required during
retraction

319 N or less

Supplied pressure required forextension

Air pressure required duringextension

0.1 MPa or less

Amount of swaying during telescopic
guide pipe extension
Whether the pressure in the pipe canbe adjusted to the target value
Accuracy of measurement of telescopic
guide pipe extended length

Whether the telescopic guidepipe sways (if there is swaying,
the time it takes for swaying tostop)
Difference between suppliedpressure and the pressure inside
the telescopic guide pipe
Value converted from theamount of drum rotation of thecable winder

Rationale of objectives
Because it must be able toretract at or below 319 N(design value), the tension
force obtained when the cablewinder motor output torque is100%
Normal pressure of telescopic
guide pipe: because it must
be able to expand and retract
at 0.1 MPa or less

Because ideally, even if theinvestigation equipment with
Φ84 mm is misaligned in thehorizontal direction, it should
not touch the Φ187 mm
opening
Rated tension force of thecable winder: Because it must
be able to retract the pipe at
319 N or less
Normal pressure of telescopic
guide pipe: because it must
be able to expand and retract
at 0.1 MPa or lessNo large amplitude(qualitative evaluation)―

The pressure in the pipeshould be equal to thedesired pressure―

Verify the actual
performance―©International Research Institute for Nuclear Decommissioning

Units 2 and 3

6. Implementation details

No.130(2) Development of the bottom access investigation method (telescopic pipe)5) (e) Feasibility verification test using the 14-stage telescopic guide pipe
〇 Test items
No.

4

5

Test items/outline
Test item: Verification of pressure resistance (0.2 MPa supply)
Test overview: The telescopic guide pipe is fully extended andsubjected to pneumatic pressure of 0.2 MPa, which is the designpressure resistance value of the telescopic guide pipe, for 3 hours (= 2hour round trip for telescopic pipe operation + 1 hour of survey time).
Disassemble and visually inspect for damage to the pipe anddeformation of the pipe end stopper ring, scraper, scraper retaining
bolt, and collar
Test item: Verification of behavior of simulated structure and telescopic
pipe when snagged
Test overview: A simulated opening is placed at the bottom of the RPV
at a height of about 5.9 m from the end face of the cable winder, andthe scraper of the telescopic guide pipe is snagged. Verify whether thetelescopic guide pipe can extend/retract following the tapered shape ofthe scraper
Target scraper: Because the larger diameter pipes are easier to catchon the opening, when the pipe is fully extended, of the scrapers thathave passed through the opening, the one closest to the opening (12thstage pipe scraper)

Confirmation items
Must be able to withstand apressure of 0.2 MPa

Capable of being pulled out even if Possibility of passing through ancaught on the opening
opening

6

7

Test item: Verification of extension/retraction operations when there isadhesion of foreign substances
Test overview: Foreign substances are adhered to the outer surface ofthe 2nd stage pipe, which has the largest diameter, greatest sliding
resistance, and easily accumulates foreign matter and thus is likely
susceptible to adhesion effects. Verify whether telescopic guide pipe
extension/retraction operations are possible. The foreign substances tobe used are soil with a 15 μm grain size and alumina with a 75 to 100
μm grain size

8

Whether there is deformation of
main components 3 hours after
supplying 0.2 MPa

Objective(evaluation criteria)
No deformation before orafter supplying 0.2 MPa

Difference between supplied
Whether the pressure in the pipe
Verify the actualpressure and the pressure inside
can be adjusted to the target value
performancethe telescopic guide pipe

Test item: Verification of emergency retraction behavior
Test overview: The 14-stage telescopic guide pipe is extended to verify Whether the negative pressure
if it can be retracted without using a cable winder, either by reducing
generated by a vacuum generator
the interior pressure or by creating a negative pressure using a vacuum can retract the telescopic pipe
generator.

Test item: Verification of change in leakage volume when pipe is tilted
Test overview: The telescopic guide pipe is placed in a vertical/inclined
and fully extended state, the compressed air supply is turned off. Verify
any difference in internal pressure change due to leakage.
Measurement time of 30 minutes.

Evaluation items

Capable of passing throughfollowing the tapered shapeof the scraper

Negative pressure during
telescopic pipe retraction-0.092 MPa or lessTensile force required frommaximum extension

Cable tension required during
retraction

319 N or less

Supplied pressure required forextension

Air pressure required duringextension

0.1 MPa or lessDifference between supplied
Capable of adjusting theWhether it is possible to supply thepressure and the pressure inside pressure in the pipe to thedesired pressure to inside the pipe
the telescopic guide pipe
desired pressure

Whether the leakage volume
increases even if the telescopic
guide pipe is tilted

Even if the telescopic guide
Difference in leakage volume
pipe is tilted, the leakage
between vertical and tilted states volume should be the sameas in the vertical state

Rationale of objectives―――

Maximum negative pressurethat can be generated by theselected vacuum generator:
Because it must be able toretract at -0.092 MPa or less
Rated tension force of thecable winder: Because it must
be able to retract the pipe at
319 N or less
Normal pressure of telescopic
guide pipe: because it must
be able to expand and retract
at 0.1 MPa or less―
Because even if thetelescopic pipe is tilted,
extension/retraction
operations (pressureadjustment) should be thesame as when the pipe is in
the vertical position©International Research Institute for Nuclear Decommissioning

Units 2 and 3

6. Implementation details

No.131(2) Development of the bottom access investigation method (telescopic pipe)5) (e) Feasibility verification test using the 14-stage telescopic guide pipe
<1 Verification of extension/retraction operations>〇 Test overview
Vertical motions and characteristics of vertical motions are verified when the telescopic pipe is vertically extended.
〇 Test results (Part 1)•
Fundamentally, the pipe was extended from the base, and the diameter and the pressure-receiving area become smaller toward thetip. It was verified that by increasing the internal pipe pressure, all stage pipes can be extended with 0.1 MPa, the upper limit of theoperational design pressure. It was also verified that via decompression and cable winding, by retracting starting from the tip piece,
all stage pipes can be retracted. During retraction, the cable tension force (measured value) at 100% motor output torque wasexceeded, but not constantly, and since no motor overload error occurred, it was determined that there was no problem.
•
The cable tends to incline toward the anti-rotation rail on the side of the telescopic guide pipe (see No. 97) as it is extended, but thedegree of inclination was improved when the cable was fed out without tension force being applied after full extension. If the pipe isinclined and the cable is in contact with the pipe inner surface, tension force will be applied to the cable, which may push the pipe
horizontally, so countermeasures are required.
•
Cable tension force (motor drive torque) fluctuates greatly in a short time, but the drive load may not be uniform due to imprecise
assembly of gears and drive shafts. This results in a loss of cable tension force and needs to be inspected and improved in the
future.
Extension range
Retraction range
Extension range
Retraction range
Extended length (winder)

Telescopic guide pipeinternal pressure
Supply pressure setting

Supplied pressure [kPa]Tensile force [N]Extended length [mm]Cable tension
force

While the extension speed during
the 3-stage telescopic guide pipe
test was 20 mm/s, themechanism was slowed down to2 mm/s to increase the tension
force of the cable winder, so thepressure inside the telescopic
guide pipe did not decrease withextension.

Rated tension
force 170 N(Actualmeasurement)

Time [s]Time [s]Changes in the extended length, cable tension force, and internal pressure during telescopic guide pipe extension/retraction operations©International Research Institute for Nuclear Decommissioning

Units 2 and 3

6. Implementation details

No.132(2) Development of the bottom access investigation method (telescopic pipe)5) (e) Feasibility verification test using the 14-stage telescopic guide pipe
<1. Verification of extension/retraction operations>〇 Test results (Part 2)•
It was verified that after extending each stage pipe, or at the start of retraction, the telescopic guide pipe tip sways with an amplitude of about±10 mm, but extension/retraction is possible without more swaying than that. In addition, even when there was swaying, it stopped in approx.
2 seconds, verifying that there are no extension/retraction problems.
•
The extended length of the telescopic guide pipe was determined by the cable feed rate (the amount of rotation of the winding drum), but acomparative evaluation with the actual extension length using a laser rangefinder verified that the full extension length (6282 mm) can bemeasured with a 2% error.
14.0

Target plate

Laser
rangefinder

Measurement error[%]

12.0
10.0
8.0
6.0
4.0
2.0

0.0
-2.0
0

1000

2000

3000

4000

5000

6000

7000

Extended length (measured value by laser range finder)[mm]Method of measuring extended length
by laser rangefinder

Telescopic guide pipe extended length and the measurement error

It was verified that the 14-stage telescopic guide pipe and cable winder studied in FY2021 canbe used for full extension and retraction. It is necessary to modify for fixing the inclination in
the direction of the anti-rotation rail during extension and for improving the accuracy of cablewinder drive shaft assembly.
©International Research Institute for Nuclear Decommissioning

Units 2 and 3

6. Implementation details

No.133(2) Development of the bottom access investigation method (telescopic pipe)5) (e) Feasibility verification test using the 14-stage telescopic guide pipe
<2. Verification of rigidity when horizontal load is applied>〇 Test overview
In a fully extended telescopic guide pipe, apply a horizontal load to each pipe joint and the tip, starting from the base, and verify theamount of tip misalignment. (Misalignment is measured only when a load is applied to the 14th stage pipe tip)
〇 Test results
When a horizontal load was applied to the pipe tip, it applied a large bending moment on the base, and since sufficient force could
not be applied to the tip to counteract the looseness, bending force was manually applied to each stage pipe starting from the tip. After
that, the amount of the tip misalignment of the 14th stage pipe due to looseness in a state of no load was checked, and it was verified
that there was a looseness of +144.7 to -218.3 mm. (The direction in which the anti-rotation rail of the telescopic guide pipe is attached
218.3 mm 144.7 mm
is negative)―+

Vertical position
Plumb bobThe bending direction force is being
applied to the pipe so that the third
stage pipe is inclined

Measuring the distance from theplumb bobAmount of tip misalignment caused by inclination
due to looseness

It was verified that if the looseness due to the gap between each stage pipe is biased in one
direction, the telescopic guide pipe cannot pass through the expected opening (Φ187 mm), even
if it is extended vertically from directly under the opening. Looseness must be suppressed.
©International Research Institute for Nuclear Decommissioning

Units 2 and 3

6. Implementation details

No.134(2) Development of the bottom access investigation method (telescopic pipe)5) (e) Feasibility verification test using the 14-stage telescopic guide pipe
<3. Verification of extension/retraction operations when the telescopic guide pipe is inclined>〇 Test overview
Install the telescopic pipe at an angle and verify the maximum inclined angle at which extension/retraction operations are possible(maximum 3.5 degrees)〇 Test results•
It was verified that all stage pipes can be extended and retracted at a 3.5-degree angle, in the same way as when verticallyinstalled.
•
There was no significant change in cable tension force compared to vertical installation. In addition, the telescopic guide pipe could
be operated with an internal pressure equivalent to the source pressure used for extension/retraction operations in the verticalstate.
Retraction range
Extension range
Retraction range

Extension range

Extended length (winder)

Telescopic guide pipe internal pressure
Supply pressure setting

Supplied pressure [kPa]Tensile force [N]Extended length [mm]Cable tension force

Rated tension
force 170 N(Actualmeasurement)

Time [s]Installation at a 3.5 degree angle

Time [s]Changes in the extended length, cable tension force, and internal pressure during telescopic guidepipe extension/retraction operations

No significant change in supply pressure during extension or required tension force during
retraction was observed when the telescopic guide pipe was inclined compared to when it
was installed vertically, verifying that extension/retraction operations are possible at an angleof up to 3.5 degrees.
©International Research Institute for Nuclear Decommissioning6. Implementation details

Units 2 and 3

No.135(2) Development of the bottom access investigation method (telescopic pipe)5) (e) Feasibility verification test using the 14-stage telescopic guide pipe
<4 Verification of pressure resistance (0.2 MPa supply)>〇 Test overview
With the telescopic guide pipe fully extended, air pressure of 0.2 MPa (the design pressure resistance value) is applied for 3 hours (=2 hour round trip for telescopic guide pipe operation + 1 hour of survey time). Disassemble and visually inspect for damage to the pipeand deformation of the pipe end stopper ring, scraper, scraper retaining bolt, and collar.
〇 Test results•
No abnormal behavior or anomalies were observed when the pipe internal pressure was set to 0.2 MPa.
•
After retracting the telescopic pipe, the stopper ring, scraper, scraper retaining bolt, and collar were visually inspected at the joints
between the 1st/2nd, 7th/8th, and 13th/14th stage pipes and no deformation or other abnormalities were observed.
CollarAppearance of scraper at the tip of the 1st stage pipe afterpressure resistance test (disassembled state)

Stopper ring

Stopper ring and collar of the 2nd stage pipe after pressure
resistance test (disassembled state)

It was verified that the test manufacturing of FY2021 telescopic guide pipe has pressureresistant strength that satisfies required specifications.
©International Research Institute for Nuclear Decommissioning

Units 2 and 3

6. Implementation details

No.136(2) Development of the bottom access investigation method (telescopic pipe)5) (e) Feasibility verification test using the 14-stage telescopic guide pipe
<5 Verification of behavior of simulated structure and telescopic guide pipe when snagged>〇 Test overview
A simulated opening at the bottom of the RPV is placed at a height of approx. 5.9 m from the end face of the cable winder, and thetelescopic guide pipe scraper is placed on the opening. Verify that the telescopic guide pipe can be extended and retracted following
the tapered shape of the scraper
Target scraper: Because the larger diameter pipes are easier to catch on the opening, when the pipe is fully extended, of the scrapers
that have passed through the opening, the one closest to the opening (12th stage pipe scraper)〇 Test results•
When the taper of the lower side of the 12th stage pipe scraper was brought into contact with the simulated opening, the entire
telescopic guide pipe inclined, allowing it to pass through and retract.
•
Since the scraper upper taper of the 12th stage pipe could not structurally be brought into contact with the simulated opening,extension was performed after bringing the narrow part of the telescopic guide pipe connector into contact with the investigationequipment. The telescopic guide similarly inclined to allow extension after passing the scraper through.
•The pressure in the pipe during extension was the same as during non-contact, and no significant change was observed in thecable tension force during retraction.
•
The taper of the investigation equipment was also brought into contact with the simulated opening and then retraction was
performed. The telescopic guide pipe similarly inclined, allowing it to pass through and retract.
Scraper

Simulated investigationequipment

Simulated
opening(Φ187)

Simulated
opening(Φ187)

Retracting through the simulated opening following the taper

The taper of the investigation equipment is incontact with the simulated opening

It was verified that even if the telescopic guide pipe gets caught on the structure, thetelescopic guide pipe inclines along the scraper's tapered surface, thereby eliminating thesnag and allowing extension/retraction to continue.
©International Research Institute for Nuclear Decommissioning

Units 2 and 3 No.137

6. Implementation details(2) Development of the bottom access investigation method (telescopic pipe)5) (e) Feasibility verification test using the 14-stage telescopic guide pipe
<6. Verification of emergency retraction behavior>〇 Test overview
With the 14-stage telescopic guide pipe extended, reduce the internal pressure or create a negative pressure using a vacuum generator.
Verify that the telescopic guide pipe can be retracted without using a cable winder.
〇 Test results•
When the pipe internal pressure was reduced during the fully extended state, the telescopic guide pipe gradually tilted, and the test
was stopped when the tip of the 14th stage pipe tilted more than 5.5 degrees. The test was resumed with the tip of the telescopic
guide pipe lightly suspended by a rope to prevent it from tilting too much.
•
The pipe retracted irregularly as the pressure was reduced, and at an internal pressure of 0 kPaG (atmospheric pressure), the 2ndstage pipe and the 5th to 9th stage pipes retracted completely.
•
As a result of creating a vacuum inside the pipe and reducing the pressure to -74 kPaG (maximum negative pressure value), the 10th
to 12th stage pipes further retracted, and the pipe retracted to the extended length of 250 mm. Since in this state the pipe did not
move even when retraction was attempted by manually pushing in the tip, it is assumed that the cable was jammed inside the pipe.
•
It is expected that even at this retracted length, the telescopic access equipment can be collected in the enclosure by adjusting theposture of the arm-type access equipment for retrieval, but it is necessary to evaluate whether the telescopic access equipment canbe subsequently isolated and collected via the maintenance arm in the enclosure.

The stage on the tip side does not retract completely

Retracted by negative pressure (most retracted state)
Since the telescopic guide pipe cannot be completely retracted from the fully extended state evenwhen the pipe interior is negatively pressurized, future evaluation is required to determine whether thepipe can be collected in the enclosure while in said state, or whether it can be isolated and collectedby a maintenance arm.
©International Research Institute for Nuclear Decommissioning6. Implementation details

Units 2 and 3 No.138(2) Development of the bottom access investigation method (telescopic pipe)5) (e) Feasibility verification test using the 14-stage telescopic guide pipe
<7 Verification of extension/retraction operations when there is adhesion of foreign substances>〇 Test overview
Among the 14 stage pipes, the 2nd stage pipe has the largest diameter, the highest sliding resistance, and is believed to be most impacted
by adhesion of foreign substances. Foreign substances are applied to the outer surface of the 2nd stage pipe to verify whether
extension/retraction operations are possible. The foreign substances to be used are soil with a grain size of 15 μm and alumina with a grain
size of 75 to 100 μm.
〇 Test results•
It was verified that the 2nd stage pipe, which was covered in soil and alumina, could be re-extended after retraction.
•
The telescopic guide pipe internal pressure during extension was the same as in the normal condition, and the cable tension force duringwinding was not significantly different from that in the normal condition.
•
After the test, the scraper was disassembled and visually inspected for wrapping around the dust seal and the packing. Although the dirt
was caught by the dust seal and did not appear to adhere to the packing, there were traces of larger alumina Thereparticlesthat
hadthatpassedare nosigns
through the dust seal and also adhered to the packing in minute amounts.
a large amount passed
through the dust seal

Dust seal(a) Soil
Appears to have passed throughthe dust seal, but a very small
amount has adhered to the packing(a) Soil(b) Alumina
Powder adhered to the entire outer surface ofthe pipe(a) Soil There are wiping streaks(b) Alumina
Condition of pipe outer surface after retraction
and re-extension(b) Alumina
Dust seal condition

Compared to the case where no powder is adhered, there is no significant difference in the internalpressure during extension or in the cable tension force during retraction, so it is determined that thetelescopic guide pipe can be extended and retracted without any problem even in the case ofadhesion of powdery foreign substances.
©International Research Institute for Nuclear Decommissioning

Units 2 and 3

6. Implementation details

No.139(2) Development of the bottom access investigation method (telescopic pipe)5) (e) Feasibility verification test using the 14-stage telescopic guide pipe
<8. Verification of change in leakage volume when pipe is tilted>〇 Test overview
Set the telescopic guide pipe in a vertical/inclined position and then in a fully extended position, shut off the compressed air
supply, and verify for any difference in internal pressure changes due to leakage. Measurement time of 30 minutes.
〇 Test results
It was verified that there is no pressure change difference in the telescopic guide pipe due to leakage when vertical vs.
when inclined (3.5 degrees). Even if the posture of the telescopic guide pipe changes, the internal pressure of the telescopic
guide pipe can be adjusted with the same amount of air supply as is used during vertical operation. Therefore, theequipment design will be proceeded using the air supply required for vertical operation.

Result of change in telescopic guide pipe pressure
Telescopic guide pipe internal pressure [MPa]At the start 30 minutesof the test after the test

Pressure drop due toleakage

Vertical

0.105

0.082

0.023

Inclined angle:
3.5°

0.106

0.081

0.025

It was verified that there is no significant change in leakage volume compared to verticalinstallation, even if the telescopic pipe is inclined.

©International Research Institute for Nuclear Decommissioning

Units 2 and 3

6. Implementation details

No.140(2) Development of the bottom access investigation method (telescopic pipe)5) (e) Feasibility verification test using the 14-stage telescopic guide pipe

〇 Test results: SummaryNo.

1

Test item

Verification ofextension/retraction
operations

Confirmation items

3

Verification of rigidity
when horizontal load
is applied

Verification ofextension/retraction
operations whentelescopic guide pipe
is inclined

4

5

Verification of
behavior of simulated
structure andtelescopic pipe when
snaggedResults

Cable tension required during retraction

319 N or less

Achieved(No motor overload error)

Supplied pressure required for extension

Air pressure required during extension

0.1 MPa or less

Achieved(Maximum 0.1 MPa)

No large amplitude (qualitative evaluation)

Achieved(No large amplitude)

There should be no significant difference
between the supply pressure and thetelescopic guide pipe internal pressure

Achieved(No significant difference)

Accuracy of measurement of telescopic guidepipe extended length

Whether the telescopic guide pipe sways (ifthere is swaying, the time it takes forswaying to stop after extension has
stopped)Difference between supplied pressure andthe pressure inside the telescopic guidepipe
Value converted from the amount of drum
rotation of the cable winder

Tilt control of each sealing section structureduring extension (load applied: 15 points)

Amount of misalignment at height ofreactor bottom opening

50 mm or lessNot achieved (misalignment ofapprox. 220 mm)

Tensile force required from maximum extension

Cable tension required during retraction

319 N or less

Achieved(No motor overload error)

Supplied pressure required for extension

Air pressure required during extension

0.1 MPa or less

Achieved(Maximum 0.1 MPa)

Amount of swaying during telescopic guide pipe
extension

Amount of swaying during telescopic guide pipe
extension
Whether the pressure in the pipe can be
adjusted to the target value
Accuracy of measurement of telescopic guidepipe extended length

Verification ofpressure resistance(0.2 MPa supply)

Objective (evaluation criteria)

Tensile force required from maximum extension

Whether the pressure in the pipe can be
adjusted to the target value

2

Evaluation items

Must be able to withstand a pressure of 0.2
MPa
Whether the pressure in the pipe can be
adjusted to the target value
Capable of being pulled out even if caught on
the opening

Whether the telescopic guide pipe sways(if there is swaying, the time it takes forswaying to stop)
Difference between supplied pressure andthe pressure inside the telescopic guidepipe
Value converted from the amount of drum
rotation of the cable winder
Whether there is deformation of main
components 3 hours after supplying 0.2
MPa
Difference between supplied pressure andthe pressure inside the telescopic guidepipeOpening passability

Verify the actual performance

Average error 2%

No large amplitude (qualitative evaluation)

Achieved

There should be no significant difference
between the supply pressure and thetelescopic guide pipe internal pressure

Achieved(No significant difference)

Verify the actual performance- (The true value could not bemeasured by the laser rangefinder
because the telescopic guide pipe
inclined beyond the installation
angle)

No deformation before or after supplying
0.2 MPa

Achieved(No deformation)

There should be no significant difference
between the supply pressure and thetelescopic guide pipe internal pressure

Achieved(No significant difference)

Capable of passing through following thetapered shape of the scraper

Achieved(Passable)©International Research Institute for Nuclear Decommissioning

Units 2 and 3

6. Implementation details

No.141(2) Development of the bottom access investigation method (telescopic pipe)5) (e) Feasibility verification test using the 14-stage telescopic guide pipe

〇 Test results: SummaryNo.

Test item

Confirmation items

Evaluation items

6

Verification of
emergency retraction
behavior

Whether the negative pressure generated by avacuum generator can retract the telescopic
pipe

Negative pressure during telescopic pipe
retraction-0.092 MPa or lessTensile force required from maximum extension

Cable tension required during retraction

319 N or less7

Verification ofextension/retraction
operations when
there is adhesion offoreign substances

Supplied pressure required for extension

Air pressure required during extension

0.1 MPa or less

Whether it is possible to supply the desiredpressure to inside the pipe

Difference between supplied pressure andthe pressure inside the telescopic guidepipeCapable of adjusting the pressure in thepipe to the desired pressure

Achieved(No significant difference)

Verification ofchange in leakage
volume when pipe istiltedWhether the leakage volume increases even if
the telescopic guide pipe is tilted

Difference in leakage volume between
vertical and tilted states

Even if the telescopic guide pipe is tilted,
the leakage volume should be the same asin the vertical state

Achieved(No significant difference)

8

Objective (evaluation criteria)

Results
Not achieved (Could be reduced to 0.074 MPa, but the telescopic guidepipe was not be retracted completely
and was not also be retracted byhand.)
Achieved(No motor overload error)
Achieved(Maximum 0.1 MPa)

©International Research Institute for Nuclear Decommissioning

Units 2 and 3

6. Implementation details

No.142(2) Development of the bottom access investigation method (telescopic pipe)(6) (f) Feasibility evaluation〇 Purpose
Based on the results of “(e) Feasibility verification test using the 14-stage telescopic guide pipe,” evaluate whether the 14-stage
telescopic access equipment can be driven under the conditions of the reactor environment (high-temperature, high-humidity,
radiation).
〇 Evaluation
Among the 14-stage telescopic access equipment, the site of the drive that is affected by the environment is thought to be the sealing
section of the telescopic guide pipe. Therefore, based on the results of the sealing functions verification test which simulates thereactor environment (see Sheet No. 92), evaluate whether the equipment can be driven.
Summary of the sealing functions verification test results (environmental simulation test)
Simulated reactor
Simulated reactor
environment 1
environment 2
Room temperature
50℃
50℃
0 Gy (unirradiated)
7200 Gy
7200 Gy
100% (immersed in
100% (immersed in
Temperature
Normal humidity
room temperatureroom temperaturewater for 3 days)
water for 3 days)
Wetting inside the pipe
None
None
Yes
Transport Max. value While Max. value
While
While
frequency
slidingsliding Max. value sliding
1
15.4
14.2
22.6
2
13.4
16.7
22.1
approx. 5
approx. 5
approx. 5
3
13.5
13.4
23.3
to 7
to 7
to 7
4
13.0
14.3
24.2
5
13.4
15.9
23.6
Average
13.7
―
14.9
―
23.2
―
Normal environment

Sliding resistance [N]Sliding resistance[Results of the sealing functions verification test]
Sliding resistance: Increased by approx. 10 N compared tonormal environment
Leakage volume: Leakage volume was reduced compared tonormal environment

Environmental
conditions
Temperature
Cumulative dose rate

Piston direction

Leakage volume[Predicted reactor environment]
Temperature: 50℃
Humidity: 100%
Cumulative dose: 7200 Gy(assuming a 3-day investigation
under 100 Gy/h environment)

Front-facing Rear-facing Front-facing Rear-facing Front-facing Rear-facing

Time taken frommin. 58 5 min. 16 132 min. 47 11 min. 26
0.01 MPa to 0.09 113sec.
sec.
sec.
sec.
MPa

―

―

Leakage volume
from 2nd stage
pipe

0.006
L/min

0.140
L/min

0.005
L/min

0.063
L/min

―

―

Leakage volume
when converted to
the 14-stage
telescopic guide
pipe

0.06
L/min

1.22
L/min

0.05
L/min

0.56
L/min

―

―

©International Research Institute for Nuclear Decommissioning

Units 2 and 3 No.143

6. Implementation details(2) Development of the bottom access investigation method (telescopic pipe)(6) (f) Feasibility evaluation(1) Effects of change in leakage:
The leakage does not increase in the reactor environment, and it
is determined that the telescopic guide pipe can be operated byadjusting the internal pressure to the desired level

Rated tension
force 170 N(actualmeasurement)

Time [s]Difference in thrust required for extension
Targetpipe

Increased sliding
resistance inreactorenvironment [N]Difference inthrust required
for extension[MPa]

2nd stage
pipe

10

0.002

14th stage
pipe

3.7

*1

0.006

Tensile force [N](2) Retraction effects- Even when the tension force is close to 500 N duringextension, the motor does not shutdown (from an overload
error in the motor driver), and operates without issues, so a
maximum increase of 10 N in tension force, compared toapprox. 250 N during retraction, is not a problem.

Extended length(winder)Cable tension force

Extended length [mm](2) Effects of change in sliding resistance:① Extension effects- The difference in the pressure required for pipe extension due
to the increase in sliding resistance was calculated to besmall enough that there is no problem.

Retraction range

Extension range

Changes in the amount of extension/retraction and the cable tension force
during extension/retraction operations of the vertically installed 14-stage
telescopic guide pipe

It was verified that there are no operational
problems in the reactor environment, and thatthe feasibility of investigation by using thetelescopic access equipment was evaluated.

Small differences*1: Calculated by multiplying the result of the 2nd stage pipe packing by the circumference ratio©International Research Institute for Nuclear Decommissioning

Units 2 and 3

6. Implementation details

No.144(2) Development of the bottom access investigation method (telescopic pipe)(7) Summary and remaining issues

Summary• Conceptual design and element tests were conducted to address development issues, including thestudy of connections on the arm-type access equipment for retrieval.
• Reflecting the measures taken to address issues from last fiscal year (leakage and large sliding
resistance at the sealing section of the telescopic guide pipe), a prototype of the 14-stage telescopic
guide pipe was manufactured and the function verification test was conducted. The feasibility of theequipment for telescopic access operations was verified.

Remaining issues
New issues obtained from the FY2021 study and test results are listed below.
①
②
③
④
⑤

⑥
⑦
⑧
⑨
⑩
⑪

Verification of adhesive strength assuming cylindrical pipe shape
Verification of aluminum pipe operability, an alternative structural proposal for telescopic guide pipe
Control of inclination in the direction of the anti-rotation rail during telescopic guide pipe extension
Control of looseness due to the gap between each stage pipe, and prevention of the inclination
during emergency retraction (when depressurizing) due to the gap
Evaluation of telescopic guide pipe behavior when the arm-type access equipment for retrieval
sways
Uniform drive torque for cable winding drum (reduction of the loss of a cable tension force)
Test manufacturing and evaluation of posture control mechanism
Noise evaluation of the investigation equipment to dosimeters
Impact assessment of the cumulative dose on video due to CMOS camera irradiation
Evaluation of the possibility of determining telescopic guide pipe passage clearance and extension
length via the fixed-point camera at the tip of an arm-type access equipment for retrieval
Evaluation of the possibility of determining the passage of an opening and the directional correctionof telescopic guide pipe posture by the camera of investigation equipment©International Research Institute for Nuclear Decommissioning7. Summary

No.145(1) Upgrading of processing technology for the top access investigation method- Nozzle downsizing in FY2020 enabled a significant reduction in abrasive consumption
when cutting the main body of the steam separator by AWJ (Abrasive Water Jet). In thisfiscal year, study of further reduction of abrasive consumption including for cutting targets
other than the main body of the steam separator was conducted. Due to reduction andoptimization of the abrasive feed rate and use of the smaller FY2020 nozzles on cutting
targets other than the main body of the steam separator, the prospect of achieving thetarget abrasive consumption of 500 kg or less was verified through element tests.
- Laser cutting was not applicable in FY2020 and a nozzle applicable for horizontal cutting of
the steam separator main body was examined. By combining the nozzle studied in FY2020,
the operational conditions were verified to allow cutting of all targeted reactor
internals.
Insert each nozzle
Steam separator body

into the gap between
the three bodies

AWJ nozzle (angle nozzle)

Laser nozzle (angle nozzle)

Opening range

Illustration of cutting of steam separator body (AWJ cutting, laser cutting)©International Research Institute for Nuclear Decommissioning7. Summary

No.146(2) Development of the bottom access investigation method〇 Development of drone access equipment for Unit 1•

Other than that, proposed measures for issues such as response to realenvironments (darkness, dripping water, etc.) were included, and element
tests were conducted to verify the effect.

•

From the results of the element tests, the wired drone achieved the target
flight height by revising the power supply method, and the wireless drone
was able to remain in flight longer than the target time by revising thebattery configuration.
Maneuvering
cameraManeuvering
cameraPropeller motor

Survey camera*1: Predicted applications include cable

insertion for wired drones and radio
relay for wireless drones

Expected RPV
Drone
opening
RPV bottom
Pedestal

Crawler type CRD*1 accessequipment Opening

Approx. 5.8 m

In the simplified FY2020 test, the wired drone failed to reach its target flightheight due to a voltage drop in the power cable, and the wireless drone
failed to extend flight time. Issues common to both drone types included
drone monitoring methods and difficulty in investigating the RPV bottom
due to turning movements of a drone. In response to these issues,countermeasures were examined and a drone was test-manufactured.

Flight route•

Grating

ExtensionrodIllustration of accessing bydrone

Propeller

Simulatedmass

Composite cable

Wired drone prototype

Test-manufactured wireless drone

Exterior view of test-manufactured drones©International Research Institute for Nuclear Decommissioning7. Summary

No.147(2) Development of the bottom access investigation method〇 Development of telescopic access equipment for Units 2 and 3- Conceptual design and element tests were conducted to address development issues, including the studyof connections on arm-type access equipment for retrieval operations.
- Simplified tests for using a 3-stage telescopic guide pipe were conducted in FY2020 to respond to issuesof leakage from the sealing section and high sliding resistance. Improvement of pipe inner surface
roughness, etc., was applied to equipment specifications. Another simplified test using a 3-stage
telescopic guide pipe was conducted to verify the effect of the proposed response.

- Element tests were conducted to evaluate the feasibility of access equipment for all 14 stage pipes. The
feasibility of a unit of telescopic access equipment was evaluated.
Camera Tip

Approx. 8mGrating top surface

Illustration of access by telescopic guide pipe

Full retraction
Full extension
Simplified test using a 3-stage telescopic
guide pipe

Element test for the 14-stage
telescopic guide pipe
©International Research Institute for Nuclear Decommissioning