IRID In-house Project
Development of Technology for Detailed Investigation
inside Primary Containment Vessel (PCV)(On-site Demonstration of Technology for Detailed
Investigation Considering Deposit Measures)
FY2021 Accomplishment ReportAugust, 2022
International Research Institute for Nuclear Decommissioning(IRID)All Rights Reserved©International Research Institute for Nuclear Decommissioning

Table of Contents (1/2)
1. Research Background and Purpose
1.1 Reasons for this research
1.2 Reflection of results and contribution thereof
1.3 Overview of on-site demonstration
2. Implementation Items and Goals
3. Implementation Schedule and Project Organization
4. Implementation Details (Implementation items and results)
4.1 On-site demonstration of access route establishment
4.1.1 Detailed planning for establishment of access route(1) Study of ROV insertion route(2) Study of cutting plan(3) Cutting plan

©International Research Institute for Nuclear Decommissioning

1

Table of Contents (2/2)
4.1.2 On-site demonstration of access route establishment(1) Countermeasures for interfering objects(i) Implementation of detailed investigation of interfering objects(ii) Removal of lead wool mat and cutting of the grating(iii) Cutting of T type beam and middle crosspiece of handrail(iv) Cutting of conduits(2) Installation of guide pipe
4.2 On-site demonstration of detailed investigation inside PCV
4.2.1 Detailed planning for detailed investigation inside PCV(1) Study on impact of interfering objects(2) Study on impact of reduced water level inside PCV due to the earthquake
off-shore of Fukushima Prefecture
4.2.2 On-site demonstration of detailed investigation inside PCV
4.3 Level of achievement compared to the goal
5. Summary©International Research Institute for Nuclear Decommissioning21. Research Background and Purposes
1.1 Reasons for this research (1/2)- Background and the purpose of this project -3[Background]
In order to ascertain the distribution and form of fuel debris inside and outside the pedestal in the PrimaryContainment Vessel (PCV), the situation of structures in the PCV, etc. with higher accuracy for finalizing the fueldebris retrieval method, the size of the access and investigation equipment needs to be increased, and theinvestigation technology used in those equipment need to be further advanced.
[Purpose of this project]
There are large amount of deposits in Unit 1 and since the Control Rod Drive (CRD) housing or the reactor internals are assumed tohave fallen off (refer to Figure 1.1-1), the deposits need to be retrieved and the fallen objects need to be removed during fuel debris
retrieval (or before then). The purpose of this project is to enter inside the PCV by creating an opening (approximately 350mm) larger
than those created for internal investigations in the past and ascertaining the situation of inside the PCV such as the distribution ofdeposits, distribution of fuel debris in the deposits, situation of the reactor internals, etc.

Falling off of CRD housing, etc.
Falling of reactor internals, etc.

Deposits

Fuel debris
MCCI* reactants

Figure 1.1-1 Estimated status of inside Unit 1 PCV*MCCI: Molten Core Concrete Interaction©International Research Institute for Nuclear Decommissioning1. Research Background and Purposes
1.1 Reasons for this research (2/2) - Overview of detailed investigation inside Unit 1 PCV -4

The purpose of this project is to study means and equipment for retrieving deposits, and to collect information such as information
pertaining to the work plan for deposit retrieval, dismantlement and removal of fallen objects, etc., by investigating the extensive area
outside and the inside of the pedestal, by introducing Remotely Operated Vehicles (ROVs) in the basement inside the PCV throughthe X-2 penetration, during on-site demonstration of the detailed investigation inside Unit 1 PCV.

A

B

A

Information to be acquired
Outside the pedestal to
the worker access port
(A in the figure)

Inside the pedestal(B in the figure)

Method of investigation

・ Information concerning the study of deposit retrieval means andequipment(Amount, source, etc. of deposits)・ Information concerning the plan for deposit retrieval, breaking
up and removal of fallen objects, etc.
(Status under the deposits, spread of fuel debris, etc.)

・ Measurement*
・ Deposit sampling
・ Visual inspection

・ Information concerning the plan for deposit retrieval, breaking
up and removal of fallen objects, etc.(Information concerning thework space inside the pedestal, and status of falling off of CRD
housing)

・ Visual inspection©International Research Institute for Nuclear Decommissioning*: Three dimensional mapping of the surface of deposits, measurement of the thicknessof the deposits, detection of fuel debris inside or under the deposits.

5

1. Research Background and Purposes
1.2 Reflection of results and contribution thereof
FY2016 to FY2017
FY2017 to FY2018

Development of Technology for Investigation inside PCVDevelopment of Technology for Detailed Investigation inside PCV

FY2018 to FY2019
Development of Technology for Detailed Investigation inside PCV(On-site Demonstration of Technology for Detailed Investigation Considering Deposit Measures)
Development of investigation plan anddevelopment plan

Part of the on-site demonstration of the access and investigation equipment andinvestigation technology

FY2020 Development of Technology for Detailed Investigation inside PCV(Part of “On-site demonstration of access route establishment” and part of “On-site Demonstration of Detailed Investigation
inside PCV” during the “On-site Demonstration of Technology for Detailed Investigation Considering Deposit Measures”)

Thisproject

FY2021 to FY2022 IRID In-house Project Development of Technology for Detailed Investigation inside PCV(On-site Demonstration of Technology for Detailed Investigation Considering Deposit Measures)

Research projects concerning detailed design of the fueldebris retrieval methods and equipment, etc. (fuel debris
retrieval, earthquake resistance measures, repairs, criticality
control, etc.)
Information for “Determination of fuel debris retrieval methods” and“Detailed design of the fuel debris retrieval equipment”, etc.

Research concerning the technology for gradually
increasing the scale of fuel debris retrieval
Information required for gradually increasing the scale of fueldebris retrieval, etc.
©International Research Institute for Nuclear Decommissioning6

1. Research Background and Purposes
1.3 Overview of on-site demonstration (1/2)
On-site demonstration is carried out using equipment related to the establishment of the access route developed during the“Development of Technology for Detailed Investigation inside PCV”, the technology related to the detailed investigation inside
PCV and the prototype of the access and investigation equipment.

P/A chamber: Personnel air lock chamber

Establishment of the access route
New boundary part

Connecting to
a new boundary

Up to
FY 2019

Cut-through of
the air lock outer door

P/A chamber

P/A chamber

Cut-through of
the air lock inner door

Isolated part
FY2020Insertion of guide pipe

Isolated part

Detailed investigation
P/A
chamber

Isolated part

Equipment for creating
an opening

P/A chamber

AWJ
equipment

P/A chamber

Guide pipe

Supporting jig

Inserting jig

Closing lid

Cable drum

Detailed Investigation inside PCVCompletion of on-site demonstration

Seal box
P/A chamber©International Research Institute for Nuclear Decommissioning1. Research Background and Purposes7

1.3 Overview of on-site demonstration (2/2)
Setting up of installationequipment andthe isolation partγ dosimeterB10 detector

Guide ring
①Position alignment⇒② Pushing out the magnet⇒③ Access⇒④ Adsorption⇒⑤ Guide ring detachment

Guide ring installation(γ dosimeter)

Detailed visual inspection(γ dosimeter, B10 detector)

ROV-A2(Small-sized ROV)• Ultrasonic range finder• Water temperature gauge• Winch + anchor

Deposit 3D mapping(Water temperature gauge, highoutput ultrasonic sensor)

Deposit thickness
measurement (Water temperature• High-output ultrasonicsensor• Preamplifier• Water temperature gauge

Anchorgauge, ultrasonic range finder)

Fuel debris detection• CdTe semiconductor detector• Improved small-sized B10 detector• Winch(CdTe semiconductor detector,
B10 detector)

Deposit sampling*
Winch
Fuel debris
detection sensor

Removal of installationequipment and isolationequipment*Transportation and analysis of the deposit
will be studied as part of othercollaborating PJs.

Deposit collection
equipment

PJ: Project

The above-mentioned is the initial plan.
The sequence of investigation is planned to be changed
depending on the site situation.
©International Research Institute for Nuclear Decommissioning8

2. Implementation Items and Goals
Implementation items
Detailed planning forestablishment ofaccess route

On-site demonstrationof access routeestablishment

Detailed planning for
detailed investigation
inside PCV

On-site demonstrationof detailed
investigation inside
PCV

Study of ROV insertion route

Goal achievement indicators (FY2021)
Drafting the cutting plan
(Not included in the scope of the goal achievement
indicators)

Study of cutting plan
Cutting plan
Implementation ofCompletion of detailed investigation of interfering objects
detailed investigation of(Target TRL at completion: Level 6)interfering objects
CounterRemoval of lead wool
measuresfor
mat and cutting of grating
Interfering
Cutting of T type beam Completion of cutting
objects
and middle crosspiece of (Target TRL at completion: Level 6)
handrail
Cutting of conduits
Completion of installation of guide pipe
Installation of guide pipe
(Target TRL at completion: Level 6)

Study on impact of interfering objects
Study on impact of reduced waterlevel inside PCV due to theearthquake off-shore of Fukushima
Prefecture
Guide ring installation(ROV-A)

Explanation
4.1.1(1)4.1.1(2)4.1.1(3)4.1.2(1)(i)4.1.2(1)(ii)
4.1.2(1)(iii)
4.1.2(1)(iv)
4.1.2(2)4.2.1(1)Drafting of the cutting plan
(Not included in the scope of the goal achievement
indicators)

Completion of guide ring installation(Target TRL at completion: Level 6)

4.2.1(2)4.2.2©International Research Institute for Nuclear Decommissioning

TRL: Technology Readiness Level9

3. Implementation Schedule and Project Organization
3.1 Implementation schedule
FY2021
令和３年度（２０２１年度）

項目
Items

4

6

7

8

9

10

11

12

1

Commencement as▽自主事業として事業開始
IRID In-house Project

Masterschedule
マスタースケジュール
Drafting the investigation planand the development plan5

令和４年度（２０２２年度）～
FY2022
2

3

4

5

6

7

8

9

▽中間報告
Interim report

10

11

備考
Remarks▽最終報告
Final report

Drafting the investigation plan

Establishment of(1) アクセスル-ト構築
access routeand the development plan
調査計画・開発計画の策定
Review of the plan
計画の見直しOn-site demonstration of the access andinvestigation equipment and the investigation
technology

調査計画・開発
計画の策定
Drafting the investigation plan
Detailed
and the development plan
調査計画・開発計画の策定
ROVによるPCV内部
investigation(2)
詳細調査
inside PCV with
Review of the plan
計画の見直しthe help of ROVCountermeasures for
干渉物の対策Establishment of(1) アクセスルート構築
access route

アクセス・調査装置及び調査技術の現場実証interfering objects

Installation of guide pipe
ガイドパイプ設置

Work training
作業訓練
ROV preparation
ROV準備

Detailed
investigation
ROVによるPCV内部(2) inside PCV with
詳細調査
the help of ROV

Detailed investigation inside PCV with the help of ROV
ROVによるPCV内部詳細調査
Compilationof report
報告書まとめThe above-mentioned is the initial plan. The schedule is planned to be revised as needed depending on the situation of investigation, etc.
©International Research Institute for Nuclear Decommissioning10

3. Implementation Schedule and Project Organization
3.2 Project Organization
International Research Institute for Nuclear Decommissioning(IRID)(Headquarters)

Project teams to cooperate for technological development○ Development of overall plan and technology management○ Summary of technology management such as progress oftechnological development, etc.

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

Part of “On-site Demonstration of Access RouteEstablishment” and part of “On-site Demonstration of
Detailed Investigation inside PCV” during the “On-site
Demonstration of Technology for Detailed Investigation
Considering Deposit Measures”

Cooperation

Hitachi-GE Nuclear Energy, Ltd.

Development of Technology for Retrieval
Fuel Debris and Reactor Internal structuresofDevelopment of Sampling Technology for Retrievalof Fuel Debris and Reactor Internal Structures
Development of Technology for Increasing
the Scale of Fuel Debris Retrieval in Stages
Development of Technology for Collection, Transfer andStorage of Fuel Debris

Development of Analysis and Estimation Technology
for Characterization of Fuel Debris
Development
inside RPVofTechnology

forInvestigation

Research and Development for Treatment and Disposalof Solid Radioactive Waste©International Research Institute for Nuclear Decommissioning

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4. Implementation Details
4.1 On-site demonstration of access route establishment
4.1.1 Detailed planning for establishment of access route(1) Study of ROV insertion route(2) Study of cutting plan(3) Cutting plan
4.1.2 On-site demonstration of access route establishment(1) Countermeasures for interfering objects(i) Implementation of detailed investigation of interfering objects(ii) Removal of lead wool mat and cutting of grating(iii) Cutting of T type beam and middle crosspiece of handrail(iv) Cutting of conduits(2) Installation of guide pipe
4.2 On-site demonstration of detailed investigation inside PCV
4.2.1 Detailed planning for detailed investigation inside PCV(1) Study on impact of interfering objects(2) Study on impact of reduced water level inside PCV due to theearthquake off-shore of Fukushima Prefecture
4.2.2 On-site demonstration of detailed investigation inside PCV©International Research Institute for Nuclear Decommissioning

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4.1 On-site demonstration of access route establishment
4.1.1 Detailed planning for establishment of access route (1) Study of ROV insertion route (1/2)⚫ If conduit E-1 or A-1 is cut, there will be a risk of ROV cables getting caught in it, therefore, Plan 1, Plan 2-1 andPlan 3 were selected as prospective ROV insertion routes based on the results of the interfering objects
investigation.
⚫ The ROV insertion route was narrowed down based on the concept of making sure to avoid impact of cutting on
the PLR instrumentation piping, that the conduit A-1 is not cut off (thinning or partial cutting is permitted), andthat conduit E-1 is not cut, if it has remained while cutting the lead wool mat and the grating.

Plan 2-1

Plan 1
Part of the leadwool mat andgrating to be cut
Lead wool mat

Assumed tip of thebucket of theinstallationequipment

Part of the leadwool mat andgrating to be cut
Lead wool mat
Site that could pose a riskof cables getting caught in
it if it is cut.

Site that could pose a riskof cables getting caught in
it if it is cut.

Plan 3

Lead wool mat
Site that could pose a riskof cables getting caught in
it if it is cut.

T type beam

Part to be cut

Part to be cut

Pipe DT type beam

Part to be cut

Pipe D

Pipe D
Conduit F
PLR instrumentation piping(Cannot be thinned)

PLR instrumentation piping
Conduit F (Cannot be thinned)

Gap of approx.
9 mm wheninterfering with
Conduit B

Conduit F

Pipe αPLR
instrumentati
on piping(Cannot bethinned)Conduit B
Conduit E-1
Conduit E-1

Conduit E-1(Not to be cut off as far as possible*)(Not to be cut off as far as possible*)

Conduit A-1(Cannot be cut off)

*Presumed to be cut while cutting thelead wool mat and grating

Pipe C

Conduit A-1(Cannot be cut off)

Pipe C(If this is cut,conduit A could get
cut off)

Conduit A-1(Cannot be cut off)

©International Research Institute for Nuclear Decommissioning4.1 On-site demonstration of access route establishment
4.1.1 Detailed planning for establishment of access route (1) Study of ROV insertion route (2/2)
In the case of Plan 1 or Plan 2-1

In the case of Plan 3⚫

⚫

It was verified that the impact of cutting on the PLR
instrumentation piping can be avoided.
⚫ It is presumed that water discharged from AWJ while
cutting lead wool mat, etc. hits Conduit E-1 and it iscut.

⚫

It was verified that the water discharged from AWJ while cutting
the T type beam is likely to pass through the PLR
instrumentation piping.
The impact can be reduced (minor thinning) by using adischarge pressure of 80MPa.
Cutting location 3

While cutting the lead wool mat and grating
Dashed line: Area in which
the T type beams are passed(T type beams are presumed
to be passed through)
PLR instrumentation piping

The distance from the nozzle to Conduit E-1 isapprox. 1.1m, and hence it is presumed that a part ofthe conduit would get be cut and cut off due topassage of the water discharged from AWJ.

Minimum distance
114 mm
Cutting location 3

If the swivel accuracy (3σ) of
the nozzle is considered, thewater discharged from AWJ
passes through the PLR
instrumentation piping

Cutting location 2

Cutting
location 2

AWJ path at

T type beam

Instrumentation piping level
Lead wool mat removal
equipment

Instrumentation piping
AWJ path on the surfaceof the T type beams

Cutting location 1

Cutting area (1)-B

Path of water discharged from AWJ at
the center height of the PLR
instrumentation piping

Grating cutting line

Guidance center for cutting:Cutting location 2 - 203.5mm or
lower*

Cutting conditions
220MPa, 3”/min, back and forth cutting

Cutting area (1)-A*: The air lock [Illegible] is cut as far as possible

External appearance ofConduit E-1

While cutting T type beam
PLR instrumentation piping

Cutting location 3

Cutting area (3)PLR instrumentation piping

Cutting area (2)Minimum distance
99.6±5mm
T type beam cutting line

Minimum distance
109.6±6mm

Cutting location 3

Cutting location 3

Cutting location 2

Cutting location 2

T type beam cutting line

Cutting position 2

Guidance center for cutting:
0° guidance center - 10±1mm

Vertical rib of the T type beam

Guidance center for cutting:Cutting location 2 - 100±5mm

Cutting location 1

T type beam

Cutting conditions
80MPa, 11.5 °/min, back and forth cutting

Cutting conditions
80MPa, 11.5 °/min, back and forth cutting

Cutting area (4)Cutting area (5)Cutting location 1
Path of water discharged from AWJ at
the center height of the PLR
instrumentation piping

Path of water discharged from AWJ at
the center height of the PLR
instrumentation piping*Change in the inclination of thehead: equivalent to -1.5 ± 0.2⚫

Avoiding any impact of cutting on the PLR instrumentation piping was given priority and the ROV insertion route was narrowed down toPlan 1 and Plan 2-1.
©International Research Institute for Nuclear Decommissioning

AWJ: Abrasive Water Jet

13

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4.1 On-site demonstration of access route establishment
4.1.1 Detailed planning for establishment of access route (2) Study of cutting plan (1/2)(i) Confirmation of the situation of Conduit E-1⚫
⚫

Flex camera

The situation of Conduit E-1 was confirmed after cutting the lead wool mat andgrating and the T type beam.
It was found that the flexible side conduit had been cut and was hanging down.

Pipe βPedestal side

PLR instrumentation piping
T type beam
Conduit E-1 flexible pipe

Conduit A-1
Conduit B
Conduit C

Pipe D
Conduit F

T type beam
Cutting line
Cutting line
Lead wool mat

Grating

Air lock inner door side

Conduit E-1 flexible side
(Cut and hanging down)©International Research Institute for Nuclear Decommissioning

Conduit E-1 pipe material side15

4.1 On-site demonstration of access route establishment
4.1.1 Detailed planning for establishment of access route (2) Study of cutting plan (2/2)(ii) Conduit C cutting test⚫
⚫

Cutting would be difficult within the lifetime of the nozzle from a distance of 452mm. However, it was possible from a distance of 183mm
as well as 223mm.
In case that Conduit E-1 remained and is interfered with the AWJ head during cutting , it was decided that the conduit would be cut off.

(a) Realistic assumption
Pipe DCan be cut with 1 cycle ofback and forth
While cutting
Pipe D(b) Assuming that Conduit E-1 would not be cut
while cutting the lead wool mat, etc.

PLR instrumentation

Cannot be cut even with
2 cycles of back and forth

Pipe D

Pipe D cutting

Conduit F
While cutting Conduit E-1
While cutting Conduit F

Conduit F
Cutting of Conduit F
Cutting of Conduit C

If the AWJ head interferes with Conduit B

Conduit E-1

While cutting
Conduit C

183mm

PLR instrumentation

452mm

223mm

Conduit B

Conduit C

After cutting onwards

Conduit C

Operatinglifetime180min(B side)70° area x 2 cycles of back and forth
After cutting for 1 cycleof back and forth
After cutting for 2 cycles
of back and forth

After cutting backwards(B side)183mm(B side)Accumulated cutting time (min) when cutting is started

452mm

Accumulated cutting time (min) when cutting isstarted at the time of the first cycle of back and forthand the second cycle of back and forth©International Research Institute for Nuclear Decommissioning

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4.1 On-site demonstration of access route establishment
4.1.1 Detailed planning for establishment of access route (3) Cutting plan (1/4)(i) Cutting the lead wool mat and grating

Cutting in
backward direction

Handrail

Swivel head

NozzleCutting location 3

Cutting in onward
direction

Center of cutting
location 2⚫

The AWJ equipment that has been newly prepared for cutting the lead wool mat and grating will be used.
After performing cutting in the onward direction, the cutting status will be confirmed and if some part has not been cut, cutting will be
performed in the backward direction.
Cutting in the onward direction will be performed in two parts, and the cutting in the backward direction will be performed in one go.
The cutting will be performed in the order of washing with WJ, cutting in onward direction, and then cutting in backward direction. Afterevery step, the dust inside the PCV will be confirmed and the necessity of the subsequent step will be determined.

Center of cutting
location 1⚫
⚫

R200mmCameraCutting line

Simulated lead wool mat

Grating

Figure 4.1.1(3)(i)-2 Cutting plan drawing

Figure 4.1.1(3)(i)-1 AWJ equipment for cutting the lead wool mat and grating©International Research Institute for Nuclear Decommissioning

WJ: Water Jet

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4.1 On-site demonstration of access route establishment
4.1.1 Detailed planning for establishment of access route (3) Cutting plan (2/4)(ii) Cutting the T type beam⚫
⚫
⚫

In order to increase the distance between the water discharged from AWJ and the PLR instrumentation piping, the AWJ
equipment newly prepared with a changed nozzle angle will be used.
Since the cutting diameter is small, the cutting location will be changed and a wider cut will be taken so that the head of the long
AWJ equipment does not interfere with the T type beam while cutting the conduits.
After every cut, the status of the cut and the dust inside the PCV will be confirmed, and the necessity of the subsequent step will
be determined.

Air lock chamber

350A isolation valve Personnel air lock
AWJ
equipment

Inside PCV

Minimum distance

AWJ guide pipe

Isolated part

Rail

Outer
door

Name ofequipment

Lead wool mat
removalequipment

New AWJ
equipment (withchangednozzle angle)

Inner
door

Short
AWJ equipment

T type beam cutting line

AWJ head

Cutting location 3Long
AWJ equipment

Pipe
Seal caseCutting center: Cutting
location 2 – 100±5mm

0° guide line
0° guide line

Pipe

Structureof the AWJ
head

Pipe
Cutting location 1

Seal caseTo be cutCutting
location 2

Lead wool mat
and grating

T type beam andhandrail middle
crosspiece

Inner door, grating,and handrail
stanchion

Path of AWJ at the central
height of the PLR
instrumentation piping

Seal case

0° cutting

Minimum
distance
T type beam
cutting line

Conduits(Pipe D, Conduit F,
Conduit C)

Telescopic extension

Cutting location 3

Portion to be cut
Cutting diameter

Head

Outer
diameter
LengthSwivel radius

Cutting
location 2

CameraCutting center: 0° cutting
center – 10±1mm

Inclination

NozzleAngle ofattackCutting location 1

0°
Figure 4.1.1(3)(ii)-1 AWJ equipment with changed nozzle angle

Change in the inclination of thehead: Equivalent to -1.5 ± 0.2°

Note: The telescopic mechanism is retracted before rotating the pipe

-1.5°

-1.5° cutting

Figure 4.1.1(3)(ii)-2 T type beam cutting plan
©International Research Institute for Nuclear Decommissioning4.1 On-site demonstration of access route establishment

18

4.1.1 Detailed planning for establishment of access route (3) Cutting plan (3/4)(iii) Cutting the middle crosspiece of the handrail⚫
⚫

The middle crosspiece of the handrail will be cut at the stage when the AWJ equipment is pulled out after cutting the T
type beam, so as to reduce the duration of the schedule.
Since dust from inside the PCV tends to rise at the time of horizontal cutting, along with verifying the portion to be cut, theinside of the PCV will be washed by means of WJ, and after checking for dust inside the PCV, it will be determined
whether or not further cutting is required.
Step1: Pulling out / 90°rotation① Pulling out

Cutting (1)Reference +25°
(115°)

Reference② 90° rotation
STEP 2: Bending

Reference -25° (65°)③ Bending

The nozzle rotation angle in ( ) is thevalue monitored during the operation

Cutting (2)Reference (2) - 25°(-120°)

Reference (2)Step3: Telescopic extension

Reference (1)④ Telescopic extension
Figure 4.1.1(3)(iii)-1 Method of setting the AWJ head for cutting the middle
crosspiece of the handrail

Reference (1)+25° (-30°)
The nozzle rotation angle in ( ) is thevalue monitored during the operation
Figure 4.1.1(3)(iii)-2 Handrail middle crosspiece cutting plan drawing©International Research Institute for Nuclear Decommissioning

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4.1 On-site demonstration of access route establishment
4.1.1 Detailed planning for establishment of access route (3) Cutting plan (4/4)(iv) Cutting of conduitsLong AWJ equipment will be used.
Pipe D, Conduit E-1 (if it interferes), Conduit F and Conduit C will be cut based on the results of verification of the situationof Conduit E-1 and of the Conduit C cutting test, and circumvention of the risk of cables for ROV getting caught whicharises as a result of cutting off Conduit A-1.

Cutting Pipe D

Cutting location 3
Cutting location 2
MarginCutting location 3

At the time of
cutting Conduit D

Pipe D

Cutting of Conduit E-1

PLR instrumentation
piping

AWJ path at the heightof the PLR
instrumentation piping
Pipe D cutting line

PLR instrumentation piping

Cutting location 2

MarginConduit F△θ=50° x back and forth
Conduit E-1

At the time of cutting Conduit E-1

Cutting location 1
Conduit E-1 cutting line

Fitting⚫
⚫

At the time of cutting Conduit F

Pipe

Cutting location 1
PLR instrumentation piping

At the time of cutting Conduit C
If the AWJ head does not interfere with Conduit B

Cutting Conduit C

Cutting Conduit F

If the AWJ head interferes with Conduit B
Cutting location 3

Cutting location 3
Cutting location 2

Conduit C cutting line

Cutting location 2
Conduit C

Conduit B
Conduit A-2
Conduit A-1

Conduit C

Conduit E-1

Conduit F cutting line
Cutting location 1

Outer diameterof headFitting

ConduitE-1

Conduit F

Cutting location 1△θ(2) = 72.5° x 2 times

Figure 4.1.1(3)(v)-1△θ(1) = 72.5° x 2 times

Conduit cutting plan
©International Research Institute for Nuclear Decommissioning

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4.1 On-site demonstration of access route establishment
4.1.2 On-site demonstration of access route establishment (1) Interfering objects countermeasures (1/5)◼ Investigation of interfering objects is carried out for understanding the detailed location of the interfering
objects under the lower steel portion of the grating (PLR instrumentation piping and conduits).
Image of the investigation of interfering objects
X-2 penetration inner door

X-2 penetration inner door

3D image of the equipment

Supporting jig

Forward / backward(position alignment)

New camera
equipment
Stand
Extent to which camera can belowered: maximum 2500 mm

Lead wool mat

1FL grating(*T.P. 8, 234)

Reactor Pressure Vessel side

Conduit D

LED light
Conduit E-2 Conduit E-1

Conduit B
Conduit F(To be cut if it interferes with
the ROV insertion route)Conduit C(*T.P. 6,710)

Lower steel part of grating

Light turned ON
ConduitConduit A-1
A-1

ConduitA-2
AConduit2

PLR instrumentation piping(Lower steel part of the grating needs to be cut
at a location such that there will be no impact.)

Side camera

Conduits
ConduitsA-1,
A-1,A-2
A-2(If it interferes with the ROV insertion route, cutting
needs to be performed upon taking measures such as
Camera unit bundling 2 conduits together, etc.)(lowest position*T.P. 6, 767)
Water level on 4/21 Between T2 (T.P. 5,964) and L2 (T.P. 5, 664)

LED light±180° Rotation

Lower camera

Light turned ON Camera unit enlarged*Estimated height©International Research Institute for Nuclear Decommissioning

Cited from materials available on the website of Tokyo Electric Power Company Holdings, Inc. https://www.tepco.co.jp/decommission/
information/committee/ roadmap_progress/pdf/2021/d210427_09-j.pdf

21

4.1 On-site demonstration of access route establishment
4.1.2 On-site demonstration of access route establishment (1) Interfering objects countermeasures (2/5)(ii) Removal of lead wool mat / Cutting of grating
Removal of lead wool mat,and cleaning and cutting of
the grating were completed
as planned.

350A isolation valve

Personnel air lock

Inside PCV

AWJ
equipment

Isolation part

Outer
door

Inner
door

AWJ head

Figure 4.1.2 (1) (ii)-1 Status at the time of removal of lead wool mat / cutting of grating

86.5° (Start edge)

0°ｰ108° (End edge)
Cutting area

Low pressure water
Low pressure water

Figure 4.1.2(1) (ii)-2 Setting the lead wool mat / grating cutting area

Figure 4.1.2(1) (ii)-3 Status after cutting©International Research Institute for Nuclear Decommissioning4.1 On-site demonstration of access route establishment
4.1.2 On-site demonstration of access route establishment (1) Interfering objects countermeasures (3/5)22(iii) Cutting of the T type beam
⚫ The 0°cut (first time) was too close
to the longitudinal rib and the cut
could not be made. Hence theposition was moved 5mm and the cut
was performed again (second time).
⚫ Cutting was completed at positions
by and large as per the plan.

350A isolation valve
Isolation part

Personnel air lock

Inside PCV

AWJ
equipment
Outer door

Inner door

AWJ head

Figure 4.1.2 (iii)-1 Cutting the T type beam
Cutting line of the 0° cut

First time
Second time

NozzleT type beam

Cut part

Image from internal
cameraFigure 4.1.2 (iii)-2 Head at the time of cutting the T type beam

Cutting line of the -1.5° cut

Figure 4.1.2 (iii)-3 After cutting©International Research Institute for Nuclear Decommissioning4.1 On-site demonstration of access route establishment
4.1.2 On-site demonstration of access route establishment (1) Interfering objects countermeasures (4/5)23(iv) Cutting of the middle crosspiece of the handrail⚫ Cutting was completed at positions as per the plan.
⚫ At the time of cutting on the north side, dust inside PCV increased
beyond the operating value (1.7×10-2Bq/cm3), but it was lower thanthe maximum dust recorded in the past and there was no impact on
the outside.

Cutting on the north side

Figure 4.1.2 (iv)-1 After cutting the
middle crosspiece of the handrail

Cutting on the south side

Dust concentration (Bq/cm3)

While cleaning and cutting

While cleaning and cutting

Cleaning (175 →80°)
Cutting (175 → 75°)

Actual measurement( Upstream calculation (downstream x
7.0))
・WJ cleaning (1)・Cutting the middle crosspiece of thehandrail (1)・Overlap

Operating value

After cutting

Time from start of spray (min)Figure 4.1.2 (iv)-1 Status while cleaning / cutting
the middle crosspiece of the handrail and after cutting

Figure 4.1.2 (iv)-3 After cutting

After cutting©International Research Institute for Nuclear Decommissioning

24

4.1 On-site demonstration of access route establishment
4.1.2 On-site demonstration of access route establishment (1) Interfering objects countermeasures (5/5)(v) Cutting of conduits⚫ Cutting of Pipe D, Conduit F and Conduit C was completed as per the plan.
⚫ The conduits were cut continuously for a maximum of approx. 60 minutes, but
the dust level inside PCV was low on the whole.
Internal camera

When the telescopic
mechanism is retracted

T type beam(cut part)
NozzlePipe αConduit A-2
Conduit A-1
Conduit B

Pipe D

When the telescopic
mechanism is retracted

While cutting thePipe D(North side cut tip)

Conduit C(South side cut tip)

Conduit C

T type beam

(North side cut tip)

Conduit F(South side cut tip)

While cutting
Pipe D

While cutting Conduit F

Pipe D(North side cut tip)

Pipe D
Maximum extension
1200mmConduit F

ROV insertion
location

While cutting
Conduit F

Conduit F PLR instrumentation
While cutting
Conduit C(South side cut tip)

Conduit E-2

pipingConduitB

While cutting Conduit C(When telescopic mechanism
is fully extended)

Conduit A-1 Conduit A-2

Conduit C
Stagnant water
Status while cutting Conduit C

Figure 4.1.1 (v)-1 Equipment while cutting the conduits

Pipe

Pipe γPipe βConduit E-1

Writing in red ink:
part to be cut

Figure 4.1.1 (v)-2 After cutting the conduits©International Research Institute for Nuclear Decommissioning4.1 On-site demonstration of access route establishment
4.1.2 On-site demonstration of access route establishment (2) Guide pipe installation (1/2)

25⚫ Three guide pipes were installed as scheduled.
Installation of 350A guide pipe
Chain blocks
Supporting jig

Installation of 250A guide pipe
Installation of 200A guide pipe
Chain blocks
Supporting jig
Supporting jig Jig for pushing in the guide pipe

350A guide pipe

Jig for pushing in the guide pipe

Chain blocks

Jig for pushing in the guide pipe
Inner door

250A guide pipe

Inner door

200A guide pipe

Figure 4.1.2 (2)-1 Photos while and after installing the guide pipe
©International Research Institute for Nuclear Decommissioning

26

4.1 On-site demonstration of access route establishment
4.1.2 On-site demonstration of access route establishment (2) Guide pipe installation (2/2)
Hole opening
in the inner door

250A
isolation valve

Cut portion of
the handrail

Guide pipe for
250A
Guide pipe
for 200A

Cut portion of
the grating

Guide pipe
for 350A

350A
isolation valve

200A
isolation valve

250A
extension pipe

350A
extension pipe

350A
isolation valve

200A
extensionpipe

Cut portion of
the T type beam

250A
isolation valve

Figure 4.1.2(2)-2 External appearance after completion

ROV insertion
route

Status after
cutting the
conduits©International Research Institute for Nuclear Decommissioning4.2 On-site demonstration of detailed investigation inside PCV
4.2.1 Detailed planning for detailed investigation inside PCV (1) Study on impact of interfering objects

27

It was found that the ROV cable getting caught in Conduit E-1 does not depend on its flexibility, but depends on ① the distance X between the
cut end and water surface, and ② the distance between the ROV core and Conduit E-1.
A distance of 80mm between the ROV core and Conduit E-1 is assessed to be tough. It is believed that the cable does not get caught, as longas the position of ① the cut end and the water surface is such that when the cut end is above the water surface it is at a distance of 200mm ormore from the water surface, and when it is below the surface it is submerged 300mm or more. Further, with regards to the cable getting stuck inthe steel pipe part, since the location of the steel pipe at a height during AWJ cutting is generally above (or at the same level as) the flexible pipe
(is not hanging down), as long as the above conditions are satisfied, ROV cable does not get stuck in the steel pipe. Therefore, it is consideredthat there is no risk of getting stuck on the route towards the south.
*The cable has neutral buoyancy but sinks one time when it is right under the installation equipment bucket. Since it sinks up to 200 to 250mm, aslong as the flexible end is submerged approximately 300mm, the cable does not pass under the flexible pipe end.
Small ROV (ROV-A2): highly flexible(1) Distance between cut end and water surface: x (mm)Not getting caught
Getting caught*: Assumed based on test results

Large ROV (ROV-A): less flexible(2) Distance between ROV core and Conduit E-1
80mm (minimum)

150mm (maximum)

80mm (minimum)

150mm (maximum)

Flexible pipe

Conduit E-2
Conduit E-1
Hanging down
after cutting

Steel pipe part
Distance between
cut end and water
surface: x

Conduit E-2 side(air lock side)

Water
surface

Jet deflector
Installation positionside (Pedestal side)

Flexible pipe end(Conduit E-1)

It is determinedthat the cablegets caught if it
is on the E-2
side of theflexible pipe.

ROV cable

Distance up to the water surface: 200mm

As the cable does not
go to the E-2 side, itdoes not get stuck.

The test being conducted (200mm distance between the cut end and the water surface)*Photographed with a birds-eye view camera for the mock-up test.
(The photo has been flipped to match it with the figure)©International Research Institute for Nuclear Decommissioning4.2 On-site demonstration of detailed investigation inside PCV
4.2.1 Detailed planning for detailed investigation inside PCV(2) Study on impact of reduced water level
inside PCV due to the earthquake off-shore of
Fukushima Prefecture (2/13/2021)

Additional mock-up tests were conducted on anticipated matters of concern resulting from reduction in the water level inside Unit 1 PCV. Based on the constraints andoperating conditions pertaining to ROV movement in water and investigation in the obtained low water level, the operation during the investigation with actual equipment
was organized as follows:[Operation policy concerning ROV movement in water]■ As long as there are no interfering objects, normal movement in water and investigation shall be carried out.
■ Measures to be taken if there are interfering objects above or below shall be as follows:
1) As primary assessment, the camera images shall be confirmed to find out whether or not the object can be clearly avoided, and then the advisability of avoiding the object or thenecessity of measuring the dimensions shall be determined (*).
2) Assuming that the route for avoiding the object is on its lower side, the distance between the interfering object and the bottom surface shall be measured, and the advisability of
avoiding the objects shall be determined.
3) If the route for avoiding the object is only above it, the distance between the interfering object and the water surface shall be measured, and then advisability of avoiding the objects
shall be determined.
4) If avoiding the object from above it is difficult, the extent to which the water level needs to be raised for avoiding the object shall be calculated (while taking measurement errors into
consideration), and subsequent response actions (*2) shall be discussed with TEPCO.
*1: The decision about avoiding the object taken at the stage of primary assessment shall be finalized upon discussion with TEPCO while taking into consideration theoverall opinions of the Hitachi design personnel / ROV operators and other concerned persons.
*2: Subsequent response actions: The ROV stand-by location and schedule (considering exposure of workers) until the water level is raised, needs to be coordinated.
Test name

Test for verifying the water distance required for
ROV movement in water

Large ROV Water distance required for movement in water: 250mm or(ROV-A) more (If it is less than 250mm, the entire lower part of the

Direction of
travelWater distance
200mm

ROV comes in contact with the bottom and the ROV cannot
move.)

Condition when the entire lower part of ROV ismaking contact with the bottom and it cannot movethrough the water (large ROV, water distance 200mm)

Direction of
travelWater distance
150mm

Small ROV Water distance required for movement in water:(ROV-A2) 200mm or more (If it is less than 200mm, some of
the lower part of the ROV comes in contact with thebottom and the ROV cannot be controlled.)

Condition when some of the lower part of the ROV ismaking contact with the bottom and it cannot movethrough the water (small ROV, water distance 150mm)b) Test for checking the necessity to return
when the ROV runs aground on the depositsc) Test for determining whether or not it is possible to return
after having crossed over the mount of deposits

Even if the ROV runs aground on thedeposits, it can return by moving backwards.

If the ROV has levelled down the mount of deposits andmoved ahead, it can return by moving backwards.

Directionof travel

The front part of the ROV is covered with deposits and with its
driving force the ROV is unable to move any further, but it canmove backwards.
Condition when the ROV runs aground on the deposits (Large
ROV, angle of inclination 5°)

Directionof travel

Height of themount 50mm
Moving ahead by levelling down the mount of deposits with themain body of the ROV.
Condition when the ROV levels down the mount of deposits
and moves ahead. (Large ROV, water distance 200mm)

Even if the ROV runs aground on the If the ROV has levelled down the mount of deposits andmoved ahead, it can return by moving backwards.
deposits, it can return by moving backwards.

Direction of
travelLower pan tilt
cameraDirectionof travel
Height of themount 50mm

The lower pan tilt camera of ROV-A2 is covered withahead by levelling
down the Institutemount of deposits
with Decommissioning©International
Research
for Nuclear
deposits and with its driving force the ROV is unable Moving
the main body of the ROV
to move any further, but it can move backwards.
Condition when the ROV runs aground on the Condition when the ROV levels down the mount of deposits
and moves ahead. (Small ROV, water distance 100mm)
deposits (Small ROV, angle of inclination 5°)

28

29

4.2 On-site demonstration of detailed investigation inside PCV
4.2.2 On-site demonstration of detailed investigation inside PCV
The work of installing guide rings for the four jet deflectors on the southern route was safely completed.

Before installation

After installation

Before installation

After installation

Target guide ring
installation position

Target guide ring
installation position

Jet deflector H

Before installation

Jet deflector G

After installation

Before installation

After installation

Target guide ring
installation position

Target guide ring
installation position

Jet deflector F

Jet deflector E©International Research Institute for Nuclear Decommissioning

30

4.3 Level of achievement compared to the goal
Implementation items
Detailed planning forestablishment ofaccess route

On-site demonstrationof access routeestablishment

Detailed planning for
detailed investigation
inside PCV

On-site demonstrationof detailed
investigation inside
PCV

Goal achievement indicators (FY2021)

Study of ROV insertion route

Drafting the cutting plan
(Not included in the scope of the goal achievement
Study of cutting plan
indicators)
Cutting plan
Implementation ofCompletion of detailed investigation of interfering objects
detailed investigation of(Target TRL at completion: Level 6)interfering objects
Interfering
Removal of lead wool
objects
counterme mat and cutting of grating
asuresCutting of T type beam Completion of cutting
and middle crosspiece of (Target TRL at completion: Level 6)
handrail
Cutting of conduits
Completion of installation of guide pipe
Installation of guide pipe
(Target TRL at completion: Level 6)
Study on impact of interfering objects
Study on impact of reduced waterlevel inside PCV due to theearthquake off-shore of Fukushima
Prefecture

Guide ring installation(ROV-A)

Level ofachievement
Achieved
Achieved
Achieved
Achieved
Achieved
Achieved
Achieved
Achieved
Achieved

Drafting the cutting plan
(Not included in the scope of the goal achievement
indicators)

Completion of guide ring installation(Target TRL at completion: Level 6)

Achieved

Achieved©International Research Institute for Nuclear Decommissioning

31

5. Summary⚫ The detailed plan for access route establishment was revised, countermeasures
for interfering objects and guide pipes were installed, and on-site demonstration ofaccess route establishment was completed.
⚫ The detailed plan for detailed investigation inside PCV was implemented, andguide ring installation was completed.

©International Research Institute for Nuclear Decommissioning