The 8th European Nuclear Industry Congress 2023

IRID’s R&D Results for Fukushima Daiichi
Decommissioning andFuture Challenges and Expectations
5 Dec 2023
Toyoaki Yamauchi
President of International Research Institute for Nuclear
Decommissioning (IRID)
This achievement is obtained from the subsidy project of Decommissioning andContaminated Water Management by Ministry of Economy, Trade and Industry (METI).
Prohibiting Unauthorized copy. All right reserved @International Research Institute for Nuclear Decommissioning (IRID)©International Research Institute for Nuclear DecommissioningRoles of Organizations in Decommissioning of Fukushima-Daiichi

R&D organizations

Budget support

R&D implementationin complex areas
Technological development

Japanese government
Formulation of a major policy (Mid-andLong-Term Roadmap) and progress
management
R&D support (budget)
Human resource development support

Progressmanagement

Tokyo Electric Power Company Holdings,
Inc. (Fukushima Daiichi Decontamination
and Decommissioning Engineering
Company)

ReportApplication

Implementation of decommissioning
Monitoring
Assessment

ReportTechnical
adviceFunddisbursement*Independent agency outside of
the Cabinet Office
Nuclear Regulation Authority
Implementation of safety
regulations
Assessment of implementation plandeveloped by TEPCO

Fundreserve

Nuclear Damage Compensation andDecommissioning Facilitation
Corporation (NDF)

Development of the TechnicalStrategic Plan
Management of reserve funds fordecommissioning

Reference: The Agency of Natural Resources Energy, Ministry of Economy, Trade and Industry of Japan website©International Research Institute for Nuclear Decommissioning

Overview of IRID
[Basic principles]

IRID commits to research and development of technology for the decommissioning of the
Fukushima Daiichi Nuclear Power Station as a current urgent issue from the standpoint ofstrengthening the foundation of nuclear decommissioning technology

 Name of organization:

International Research Institute for Nuclear Decommissioning (IRID)

 Establishment: August 1, 2013 (approved by the Minister of Economy, Trade and Industry of Japan)
 Member organizations: Number of IRID members: 766 people（As on March 31, 2023, excluding directors）• Research Institutes: ２ Organizations
Japan Atomic Energy Agency (JAEA), National Institute of Advanced Industrial Science and Technology (AIST)• Manufacturers, etc.: 5 Companies
TOSHIBA Energy Systems & Solutions Corporation, Hitachi-GE Nuclear Energy, Ltd., Mitsubishi Heavy Industries,
Ltd., ATOX Co., Ltd., Tousou Mirai Technology, Co. Ltd.
• Electric Utilities, etc.: 12 Companies
Hokkaido Electric Power Co., Inc., Tohoku Electric Power Co., Inc., Tokyo Electric Power Company (TEPCO)
Holdings, Chubu Electric Power Co., Inc., Hokuriku Electric Power Company, Kansai Electric Power Co., Inc., The
Chugoku Electric Power Co., Inc., Shikoku Electric Power, Incorporated, Kyushu Electric Power Co., Inc., The Japan
Atomic Power Company, Electric Power Development Co., Ltd., Japan Nuclear Fuel Ltd.

 Project costs

Unit: 100 million Yen

Fiscal
year

2013

2014

2015

2016

2017

2018

2019

2020

2021

2022

Project
costs

46

122

147

143

148

140

142

145

170

155

3

©International Research Institute for Nuclear Decommissioning

R&D projects conducted by IRID
1. R&D for fuel removal from spent fuel pool
Evaluation of Long-term Structural Integrity ofFuel Assemblies Removed from Spent Fuel Pool

2 R&D for Fuel Debris Retrieval
Technology for
Decontamination and Dose
Reduction
Remotely Operated
Decontamination
Technology in R/B

3 R&D for Radioactive Wastes
Treatment andTechnology for Proceeding
Disposal of Solid
Process Methods of Radioactive
Radioactive
WastesWastesFuel Debris Retrieval Technology
Retrieval Technology for Fuel Debris and Internal Structure:
Criticality Control/Fundamental Technology/ Small Neutron Detector

Development of Retrieval Dust collection System Technology for
Containment,
Technology and Method
for Retrieval ofTransfer
For Fuel debris and Internal
Fuel debris andAnd
Storage ofStructures
Internal structures

Development of Safety
System for fuelDebris retrieval

Fuel Debris

Technology for Environmental
Improvement<Ensuring of the stable state>
Corrosion Control Technology
in RPV/PCV

Full-scale test for Repair
Technology for PCV Leak Points

Full-scale Test for Water Circulation
Technology in PCV

Investigation and Analysis Technology＜Direct Investigation＞＜Indirect Investigation＞
Fuel debris detection Technology
for RPV
Upgrading for Identifying Conditions
Insides the Reactor

Investigation
Technology
Inside the RPVTechnology for Detailed Investigation
Inside PCV

PCV detailed
Fuel Debris
PCV Detailed
Investigation:
Fuel Debris Sampling Technology/
Investigation: Characterization
Demonstration/Increase ofDemonstration
Through
Retrieval Scaleand Analysis
of Deposits
X-6 penetration
for Fuel Debris

Progress of IRID’s R&D projects
R&D items
1 R&D for spent fuelremoval from pool
Recontaminationand dose reduction

2013

2014

2015

2016

2017

2018

2019

2020

2. R&D forfuel debris
retrieval2022～

Long-term integrity evaluation on fuel assembly removed from spent fuel pool

Remote decontamination technology forinside the R/B
Development of safety system

Criticality control and fundamental technology for small neutron detector

Fuel debris
retrievaltechnology

2021

*
*

Development of technology for fuel debris retrieval method
Dust collection system*

Development of technology for containing , transferring and storing fuel debris
Development of fuel debris detection technology for inside the RPVDevelopment of technology for identifying the reactor internals

Investigation andanalysistechnology for
PCV interiors

Development of technology for detailed
investigation inside PCV (X-6 penetration)

Development of technology for detailed investigation inside PCVDevelopment of technology for detailed investigation inside PCV (for deposits)*

Characterization of fuel debris
Development of investigation technology for inside the RPV*Development of technology for sampling and increasing the retrieval
scale of fuel debris

Technology for
improvingenvironment
3 R&D for waste
management*

Development of technology for corrosion control and evaluation of seismic resistance
Development of repair technology for stopping waterleaks in PCV and full-scale mockup test

Development of technology for water circulation in PCV andfull-scale mockup test

Development of technology for treatment and disposal of solid waste
Development of preceding processing methods for solid waste*To be continued
by otherorganization©International Research Institute for Nuclear Decommissioning

Technologies for decontamination,dose reduction and environmental
improvement (repairing PCV to stop
water leaks)©International Research Institute for Nuclear Decommissioning

Remote Decontamination Technology
Needs for technologicaldevelopment
Humans cannot access the R/B
because radiation levels arehigh in the R/B. It is necessary
to improve work
environments (dose
reduction).

For low places (floors andlower partRadiationof walls) dose in R/B
(1st
floor
of Unit 1)For
highplaces*As of March 22, 2013

4.5

3.0
2.5

2.0
4.5
X100B

Suction and blast
3.5

Reactor building (R/B)
Spent
fuel
pool

1.2

1.9

3.5 3.5

8.0

50

Upper

1700

X40B surface

MAX 23

X49 surface

Rotation arm

MAX800

4.5

100

9.0
1200

3.5

7.0
4.0

Upper

arm Upper

22.0
7.0

3.5

11.4

20
3.0
Extended
1.５

High5.0
pressure
3.5
Near the
water
floor
injection
4.0

2100
100
230
5.0
5.0
6.0
Dry7.0ice 20
4.5
15
40
blast
7.0
7.5
6.5
95
7.0
6.5
8.0
54
120
90
5.0

6.0

Decontamination ofwork and moving
RPVareas

PCV

For upper floors
100m

15Compressor
cart
60

40m
Less than 3mSv/h

Above funnel

2200

Floor
penetration

4700

247 300 220 1100

1280

290 800 1820
138
290
Decontamination
unit
cart
26
600
127
48
Work cart

20m

3mSv/h ～10mSv/h

20mSv/h ～50mSv/hMore than 50mSv/h

10mSv/h ～20mSv/hTechnology for repairing the primary containment vessel(PCV) and stopping water leaks
Test for stopping waterleaks in vent pipe

:Area for repairing PCV
and stopping water leaks

Test
using a full-scale test facility
楢葉遠隔技術センターでの実規模試験
Full-scale test facility (1 / 8 sector)
Vent pipe

Vent pipePlugmaterial

Down
comer
QuencherTorusroom wall
The test facility was built in the JAEA Naraha
Center for Remote Technology Development.

Sealed ventpipe
Remote-operated
manipulator

Work floor
Approx. 13m

Performance of water stops
was confirmed by using the
1/2 scale test facility (infactory test).
Test for stopping water leaks
using plug material

Suppression
chamber

Vent pipe
Plug material
Performance of water stops using
a plug material was confirmed byusing the 1/2 scale facility(outdoor test).

Test
piece

8

All right reserved @International Research Institute for Nuclear Decommissioning (IRID)

Investigation technology for inside
the PCV*and investigation results*PCV: Primary containment vessel
9Muon transmission measurement to identify the location of fuel debris
 Muons are secondary cosmic rays, which generate when radiation from space collides with theatmosphere of the Earth. The cosmic ray muons are high-energy particles and can pass through materials.
 Muon tomography can measure the number of muons that pass through the reactor building to image thedensity of materials such as X-ray. It can be used to image the distribution of fuel debris in the reactor
pressure vessel (RPV). (Smaller number of muons will pass through high density regions so higher density
regions show dark shadow).
Reactorbuilding (R/B)

Spent fuel pool
（SFP）
South

Estimated reactor
core region

West

North

Turbinebuilding
Measurement equipment

East
Measurement equipment

Illustration of measuring muons passing through the reactor building(horizontal cross section)

Illustration of measuring muons passing through thereactor building(vertical cross section)<Measurement principle of the muon transmission
method (illustration)>
Two panel detectors (plastic scintillator) that areplaced in the measurement equipment can detectmuons falling from space and calculate their trace on
where they have passed through from thecoordinates (X and Y axes) on the panel.
Reference: The TEOCO Holdings, Inc. website

10

Panel①Panel②X axisX axisMuon
Y axis

Y axisPanel interval approx. 50cm
©International Research Institute for Nuclear Decommissioning

Measurement results of the muon transmission method (2014 - 2017)
No high-density substances were confirmed in the core region of the Fukushima
Length of density
Daiichi Units 1-3.
（g/cc・m）(As of September 8, 2017)
Measurement image of inside the unit 3
Height（OP）[m]Reactor wall (main steam isolation valve)
ReactorPressure Vessel(RPV)
Reactor core region

Spent fuelpool

PCV surrounding
concrete

Mountain side hill

Horizontal

South

North

Reference: The TEPCO Holding Inc. website.

11©International Research Institute for Nuclear Decommissioning

Robots developed for investigation of PCV interiors
Investigation of inside the pedestal (Unit 2)

Investigation of outside the pedestal (Unit 1)○ Shape-changing robot (B2 investigation)○ Crawler type remote-operated investigation robot (A2investigation)

Crawler

When investigating
Additional
lighting

Winch

Back camera andlighting
Camera for travellingthrough guide pipe

Duringinvestigation

Type Ⅰ(when travellingthrough guide pipe)

Front camera and lighting

Camera for travelling

CRD railWinch confirmation
camera (inside)
Sensor Unit measuring
cameraCrawler○Suspension type
investigation equipment (A2’
investigation)

Investigation of inside the pedestal (Unit 3)
Thruster for upand-downCameraInvestigation of inside the pedestal (Unit 1)

Thruster for
driving
Light○Submersible robot○Submersible robot

12©International Research Institute for Nuclear Decommissioning

Investigation results of the Unit 2 lower pedestal interior(A2’ investigation on Jan.2018)
Photo: Near the pedestal inner wallat the Unit 2 PCV bottom(A fuel assembly handle was found.)Photographingplace

The Unit 2 PCV bottom(An overhead view)

Reference: The TEPCO Holding Inc. website.

13

13©International Research Institute for Nuclear Decommissioning

Investigation results of the Unit 2 upper pedestal interior(A2 investigation: January – February 2017)

Upper pedestal interior (after image processing)

Reference: The TEPCO Holding Inc. website.
14

Investigation results of the Unit 2 pedestal floor(February 2019)
Pedestal opening
Telescopic
investigationequipment

Direction to
the pedestal
center

CRD housing
Platform

CRD exchanger
CRD replacement
rail
Upper platform surface

Worker access
portWork platform
Pedestal bottom

Cable tray

*Investigation spots are tentative.

Pedestal floor

Investigation area (Photo taken in Jan. 2018)

Before touching deposits

Touching deposits

After touching deposits

無断複製・転載禁止 東京電力ホールディングス株式会社

Reference: The TEPCO Holding Inc. website.

15

Investigation results of the Unit 3 PCV interior (in July 2017)
2. Investigation results
2.3. The lower pedestal
Access opening forworkers

Platform
frame

Area C5 where a photo was taken<Camera position: Lower>

Photo area C1
Rotation rail bracket

Photo area C5
Photo area C3
Area C1 where a photo was taken<Camera position: Lower>
Grating

Deposit (pebble-like)

Photo area C4

Photo area C2
Fallen object
Massive form
depositDeposit (sandy
form)
Area C2 where a photo was taken<Camera position: Horizontal>

DepositDirection of access opening
for workers

Massive form
depositArea C3 where a photo was taken Area C4 where a photo was taken<Camera position: Upper><Camera position: Lower> The investigation has revealed that deposits in sandy, pebble-like and massive form has
accumulated.
 The access opening for workers was not confirmed visually (Deposits were found nearby thepedestal).

16
Reference: The TEPCO Holding Inc. website.

©International Research Institute for Nuclear DecommissioningReport of the 107th study committee of specific nuclear facility monitoring and evaluation on April 14, 2023.

Investigation results of the Unit 1 pedestal interior
Inner skirt
Drain sump pit

A panoramic view of the pedestal interior(image processing by TEPCO HD)
Opening

⑦

⑧

⑨

⑩

⑪

⑫

⑬

無断複製・転載禁止 東京電力ホールディングス株式会社

Reference: The TEPCO Holding Inc. website.

17

Investigation results of the Unit 1 pedestal floor(March 2022)
Tokyo Electric Power Company (TEPCO) Holdings, Inc.
investigated the pedestal opening. The first-half investigation on
March 2022 confirmed that the pedestal wall of the opening partwas damaged. The second-half investigation on March 2023
confirmed that the entire circumference of the pedestal interior was
also damaged.

インナースカート
Inner skirt

 TEPCO assumes that the lost concrete area of the pedestal
inner wall (only concrete remains) is approximately 1meter inheight and 50cm in depth.

Photo 1

Photo 2

Opening
開口部

 The lost of the pedestal outer wall opening would be limited.
A ROV frame can be seen,

Remains ofconcrete walls ?

Photo 1: Concrete remains seen from the pedestal opening
Photo 2: Concrete remains seen from the pedestal opening

無断複製・転載禁止 東京電力ホールディングス株式会社

Reference: Study committee of monitoring and evaluating specific nuclear facilities (the 107th), April 14, 2023

Photos processed by TEPCO Holdings Inc. 18

Technological development for fueldebris retrieval

19

A concept of fuel debris retrieval for the Unit 2 ofFukushima Daiichi

Isolation valve
Extension pipe

X-6 penetration flange

Access and enclosure

X-6 penetration

Arm

X-6 penetration
connection structure

・A long cantilever arm with 22 meter in length and 4.6 ton in weight is designed to passthrough a narrow X-6 penetration (55 cm in inner diameter and some deposits haveaccumulated inside the X-6 penetration).
・Fuel debris which is located on the pedestal floor 5 and 10 meters below the X-6
penetration end can be retrieved by using a tool operated with the program control system.
・Collected fuel debris will be stored in a container designed for duel debris, which isremotely operated in the enclosure.
20

All copy rights are reserved by IRID.

Development and demonstration of the robot arm
Trolley
トロリ The arm type access equipment was
manufactured which can access on a wide
range through the PCV penetration formaintenance of a control rod drive
mechanism.
 Total length of the arm: Approx. 22m
 Investigation equipment up to 10kg
can be loaded.

ブーム
Boom

テレスコアーム
Telescopic
arm

チルト機構
Tilt
mechanismTwo-axis
joint
2軸関節
Wand*
ワンド※

アーム先端にセンサを搭載
Mountedsensor on the arm head*The
can be replaced an
代わりにツールの搭載も可能※wandalternative tool.

Demonstration test at the JAEA Naraha Center for Remote Technology Development
Mock-up steel X-6
penetration

Light

CameraPedestal
Robot arm

AWJ tool
Reference: Report of the preparation status of investigation inside the Unit 2 PCV and trial retrieval of fuel debris issued by the Team Meeting and Countermeasuresfor Decommissioning and Contaminated Water Treatment Conference (the 115th).

21©International Research Institute for Nuclear DecommissioningHatch opening of the Unit 2 PCV penetration
 Opening of the PCV penetration (X-6 penetration)
Technology for opening and cleaning the X-6 penetration was developed toinsert the arm type access equipment.
 Hatch opened by remote operation at 16 Oct, 2023
 Plan to clean the through penetration by AWJ
X-6 penetration

Hatch opening equipment:
Confirmation of opening
operation, etc.

Isolation room: Confirmation of
performance for carry-in, assembly andcarry-out.

Imaging view of carrying to an
isolation room

Assembled isolation room

Isolation room

Hatch opening equipment:
Confirmation of driving performance,etc.
X-6
penetration

X-6 penetration

Hatch opening
equipment

Photographing direction
Unauthorized copy and reproduction prohibited.
©International Research Institute for Nuclear Decommissioning

22

Wire tool for
rescueWire tool for
rescueDevelopment of fuel debris retrieval methods
Technological issues
 Ensuring confinement
functions ofradioactive dust
 Establishing remoteoperation technology
 Establishingtechnologies for
reducing radiation
exposure andpreventing the spreadof contamination

Full-submersion top accessmethod (concept)
Upper table

Work cell

Partial-submersion top
access method (concept)
Ceiling craneWork cell

Shield plug
Spent fuel pool
Lower table

Dryer, separator
pool

Partial-submersion side accessmethod (concept)
X-6 penetration

Access rail
Robot arm

23

Spent
fuel
pool
Access equipmentfor RPV

Development of technology for containing, transferring and storing
fuel debris
Design of canister⇒Responding to issues specific to Fukushima Daiichi
High burnup and concentration level → High reactivity
Molten products mixed with concrete → Hydrogen generation caused by radiolysis of water containing
in concrete
Sea water injection and molten with instrumentation cables, etc. → Effect from salt contents and mixtureof impurities

Transfer method (Ex. Partial-submersion side-access method)
Reactor building

Maintenance cell
Cell forcontaining
retrieved fueldebrisTransport
entrance(extension)

Transport cell

Fuel debris
transport building

Cell for handling
container

Storagefacility

Unit canFuel debris

Collect it incanisterCanisterTransfer cart

Clean
canisters, etc.

Unauthorized copy and reproduction prohibited.
©International Research Institute for Nuclear Decommissioning

Transfer container Trailer

Store the canisterin the transfer
container

Transport thetransfer
container©International Research Institute for Nuclear
Decommissioning

Technology for waste management©International Research Institute for Nuclear DecommissioningWaste characterization : Analysis and database establishment
Sampleγ ray analysisGesemiconductor

Drying byheating
Pyrolysis

70° 180 min.
4M nitric acid

Dissolution
residue
γ ray analysisGesemiconductor

Heating

Accumulated
300 min.

Filtering

Membrane filter

Chemicalprocessing
β ray analysis
Gas flow

Debris-Wiki
The Debris-Wiki is a simple data interface to narrow the search fromclassification of waste and analysis items. It is easy to use for beginners. The
Japan Atomic Energy Agency (JAEA) has developed the wiki-style databaseplatform.

Chemicalprocessing
α ray analysis
Sisemiconductor

The FRAnDLi top page and search
performanceSupervisor

Data update,uploadWeb server
Configuration and functionsof FRAnDLi

PHP program
CSV data

User
KURION

Sample collection equipment

26

Data viewing,
downloadSummary©International Research Institute for Nuclear Decommissioning

Summary of the investigation results until now (Unit 1)
・Unit 1 has almost no fuel in the RPV, and deposits
have spread outside the pedestal. The inner walls of
the pedestal were also damaged.
(The Unit 1 reactor core was damaged about eight
hours after the loss of power.)

Composite image of the Unit 1 entire pedestal floor(Reference: the TEPCO Holdings website)

Shelf-shaped deposit
outside the Unit 1 pedestal(Reference: TEPCO Holdings
website)Damage estimation of the Unit 1 RPV/PCV(From TEPCO website)©International Research Institute for Nuclear Decommissioning

All Copy Rights Reserved by IRID

Summary of the investigation results until now (Unit 2)・Unit 2 has a lot of fuel left in the reactor pressure
vessel (RPV). Although there is 1 meter-depositon the pedestal floor. The RPV substructure
retains its original form.
(The Unit 2 reactor core was damaged about 3days after the loss of power.)

Platform

Cable tray
CRD
exchanger

Wide angle photo of the Unit 2 entire pedestal floor(Reference: the TEPCO Holdings website)

Damage estimation of the Unit 2 RPV/PCV(From TEPCO HP)©International Research Institute for Nuclear Decommissioning

All Copy Rights Reserved by IRID

Summary of the investigation results until now (Unit 3)
・ Unit 3 have some fuel left in the RPV. There is 2-3
meters of deposits on the pedestal floor.
(The Unit 3 reactor core was damaged about one
and half day after the loss of power.)
Grating
Rotating rail bracket

Fallen object

Sandy deposit
Deposit

Massive deposit

Photos taken frominvestigation inside the Unit 3
pedestal(Reference: the TEPCO Holdings
website)Damage estimation of the Unit 3 RPV/PCV(From TEPCO HP)©International Research Institute for Nuclear Decommissioning

All Copy Rights Reserved by IRID

Future Challenges and Expectations
・IRID has been conducting research and development for the investigationof inside the PCVs. The results of R&D revealed that the situation of inside
the PCVs was clarified by photography taken by camera.
・Further investigation and clarification of the accident occurrence areneeded to develop the future plan and to proceed with engineering for thedecommissioning.
・We will continue working together for the decommissioning of the
Fukushima Daiichi by sharing knowledge and experience with relevant
parties from Japan and overseas.
・Clarification of the accident occurrence would be useful for responding toan accident during operating reactors and designing the safety system for
new reactors. We will continue sharing these useful information with theworld to contribute the safety of the nuclear power plant.

All Copy Rights Reserved by IRID

©International Research Institute for Nuclear Decommissioning

Thank you for the attention.
IRID’s R&D reports are available on the following IRID
website.
https://irid.or.jp/en/research/©International Research Institute for Nuclear Decommissioning