SMiRT 27
27th International Conference on Structural Mechanics in Reactor Technology

IRID’s R&D Results for Fukushima Daiichi
Decommissioning andFuture Challenges and Expectations
6 March 2024
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

ReportTechnicaladvice

Funddisbursement*Independent agency outside of
the Cabinet Office
Nuclear Regulation Authority
Implementation of safety
regulations
Assessment of implementation plandeveloped by TEPCOFundreserveNuclear 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 theFukushima 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., TheChugoku 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

Fiscalyear

2013

2014

2015

2016

2017

2018

2019

2020

2021

2022

Projectcosts

46

122

147

143

148

140

142

145

170

155

3

©International Research Institute for Nuclear DecommissioningProgress of IRID’s R&D projects
R&D items
1 R&D for spent fuelremoval from pool
Recontaminationand dose reduction

20132014

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 andanalysis
technology 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 stopwater leaks)©International Research Institute for Nuclear Decommissioning

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

For low places (floors andlower partRadiationof walls) dose in R/B(1stfloorof 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)
Spentfuelpool

1.2

1.9

3.5 3.5

8.0

50Upper

1700

X40B surface

MAX 23

X49 surface

Rotation arm

MAX800

4.5

100

9.0
1200

3.5

7.0
4.0Upperarm Upper

22.0
7.03.5

11.4

20
3.0
Extended
1.５

High5.0
pressure
3.5
Near thewaterfloor
injection
4.0

2100
100
230
5.0
5.0
6.0
Dry7.0ice 20
4.5
1540
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 PCVand stopping water leaks

Testusing 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 pipe

Plugmaterial

Downcomer
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 the1/2 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).

Testpiece7

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

Investigation technology for inside
the PCV*and investigation results*PCV: Primary containment vessel8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 regionWestNorthTurbinebuilding
Measurement equipment

EastMeasurement 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

9Panel①
Panel②X 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

SouthNorth

Reference: The TEPCO Holding Inc. website.

10©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

11©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.

1212©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.
13

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 (sandyform)
Area C2 where a photo was taken<Camera position: Horizontal>

DepositDirection of access openingfor 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).

14
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)
Opening⑦⑧⑨⑩⑪⑫⑬

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Technological development for fueldebris retrieval

16

Development and demonstration of the robot arm
Trolley
トロリ The arm type access equipment wasmanufactured 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-6penetration

LightCamera

Pedestal
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).

17©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 the X-6 penetration was developed to insert the arm
type access equipment.
 Confinement functions when opening the hatch
 Hatch opening by remote operation
Hatch opening equipment:
Confirmation of opening
operation, etc.

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

Imaging view of carrying to an
isolation room
Hatch opening
equipment

Assembled isolation room

Isolation roomX-6 penetration

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

X-6 penetration

Hatch opening
equipment

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

18

Wire tool forrescue

Wire tool forrescue

Access route of fuel debris retrieval for the Unit 2

Cables etc
After Cleaning by low-pressure water ①
CRD rail

X-6 Penetration Before Cleaning

After Cleaning by low-pressure water ②
All copy rights are reserved by IRID.

19

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

Drying byheatingPyrolysis

70° 180 min.
4M nitric acid

Dissolution
residue
γ ray analysis
Gesemiconductor

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 dataUser
KURIONSample collection equipment

21

Data viewing,download

Technology for storing and handling high level
radioactive waste
Reactor building

Contamination
measurement byusing α camera

Lifting machine

Expanded building

Lifting machine

Waste
treatment cell
Fuel debris retrieval
equipment

Innercontainer

Dose levelmeasurement

AccesstunnelManipulator

Fuel debris

Transport crane for
HIC, etc.

Work house(dust proof area)
Maintenance craneStorage container(200 liter drum can)Innercontainertransfersystem

For Analysis facility

Drainer
Measuringequipment

Dryingequipment

Hydrogen(gas)generation
measurement

Filterventilation

HydrogenDust (including α)

Walkway

Tank area (pit structure)

Filling equipment(with pulverization
mechanism
Inspection platform
Filter pressingmachine (with scatteringprevention cover)Illustration of pressurized compression filtering method system
Unauthorized copy and reproduction prohibited.
©International Research Institute for Nuclear Decommissioning

Storagecontainer

Process flow from retrieving fuel debris
to storing it (excerpt)(Dry storage withventilation)
Transport unit for・Pump・Agitator
・High pressurecleaning machine

Samplingcontainer
PADIRAC

Waste
Storagecontainer(Dry storagewithout ventilation)

Hydrogencontrol

Dust(including α)

Dried waste
Storagecontainer

Example of storing high level radioactive waste inJapan (illustration of storage methods)©International Research Institute for Nuclear Decommissioning

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 ofthe 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 Holdingswebsite)

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
CRDexchanger

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 3pedestal(Reference: the TEPCO Holdingswebsite)

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 theFukushima 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 IRIDwebsite.
https://irid.or.jp/en/research/
A booklet “The 10-year path of research development forthe decommissioning” was released in July 2023.
*Only Japanese version is available.

©International Research Institute for Nuclear Decommissioning