MIT-Tokyo Tech Workshop on Innovative Nuclear
Energy System (MT-INES)

R&D activities for Fukushima Daiichi
Nuclear Power Station Decommissioning
27th October 2017
Naoaki Okuzumi
Senior Manager
International Research Institute for Nuclear Decommissioning(IRID)
This achievement is obtained from the Subsidy Project of Decommissioning and Contaminated Water
Managementby Ministry of Economy, Trade and Industry (METI).
無断複製・転載禁止 技術研究組合
国際廃炉研究開発機構©International Research Institute for Nuclear Decommissioning
Prohibiting Unauthorized Copy. All rights reserved @ International Research Institute for Nuclear Decommissioning (IRID)

Outline of IRID
1. NameInternational Research Institute for Nuclear Decommissioning(IRID)
http://www.irid.or.jp/en/

R&D

2. Date of Establishment
August 1, 2013

3. Membership (18 organizations)
IRID
2 Research Institutes
International
JAEA etc.
Entities
4 Manufacturers
Toshiba, Hitachi-GE,MHI etc.
12 Electric Utilities, etc.
TEPCO etc.
2HRD

©International Research Institute for Nuclear DecommissioningRole of IRID
R&D for decommissioning of the Fukushima Daiichi NPS,
with a view to strengthening the foundation of nuclear
decommissioning technologies.

EstablishmentofGovernment(METI)
Mid-and-long Term
Roadmap

Tokyo Electric Power Co.
(D&D Company)
Decommissioning ofFukushima Daiichi NPS

IRID

NDF

R&D
implementation

Strategy planning
R&D planning

FundNuclear Regulatory Authority
3©International Research Institute for Nuclear Decommissioning

IRID Research and Development Projects
2. Detection of Fuel Debris

1. Decontamination andDose Reduction◎Indirect method By analysis
 Using cosmic ray MUON
◎Direct methods
 Inside PCV and RPV

 Technology for remote operation

3,4. PCV Repair
 Development of Technology
 Full-scale test

5

5. Debris Retrieval
4 Development of fundamentalTechnology
 Development of access method andsystem Development of criticality controlmethod

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6.Debris Transfer and Storage

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 Development of technology forcollection, transfer and storage of debris©International Research Institute for Nuclear Decommissioning

Detection of Fuel Debris using Cosmic Ray MUON at Unit 1

Boundary of PCVBoundary of reactor
Boundary of coreHigh density material(fuel) is not detected at
the area where the reactor
core was originally located.

5©International Research Institute for Nuclear Decommissioning

Investigation using MUON at Unit 2
Height OP (m)Confirming the high density material shadow that is assumed to befuel debris at the bottom of RPV.

(Measurement result: as of July 22, 2016)* 1 pixel size is equivalent to approx.25 cm of crosssection of the reactor.

NorthSouth

Horizontal distance

Structure of lower part of RPV

Source: Publicized results by TEPCO Holdings, July 28, 2016

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©International Research Institute for Nuclear Decommissioning

Results of Muon Investigation at Unit 2 & 3
 Assuming the high density material that exists at the bottom of Unit 2 RPV.
 Not confirming the high density material at Unit 3 RPV that is assumed to exist atthe Unit 2 RPV.
Unit 2Unit 3
As of July 20, 2017)
Reactor Pressure Vessel

Reactor Pressure Vessel
Reactor core

Height OP (m)Height OP (m)Reactor core

TemporaryNorth

Horizontal (m)SouthSouth

Horizontal (m)North

Source: Publicized results by TEPCO Holdings, July 28, 20167

©International Research Institute for Nuclear Decommissioning

Investigation of inside the PCV using Robots
Investigation of outside the pedestal (Unit 1)○Shape-changing robot(B1,B2 investigation)

Investigation of inside the pedestal (Unit 2)○Remotely operated crawler robot forinvestigation (A2 investigation)
When driving
the narrow part

When driving thenarrowpart
狭隘部走行時Advancing direction

Crawlers(two units)
Camera for guide pipe advancement

Shape changing
Thermometer

Shape changing

CRD rail

During
調査時
investigation

Duringinvestigation
Duringinvestigation
Additionallighting

Investigation of inside the pedestal (Unit 3)
Camera forinvestigation

Dosimeter(Note) The robot for B1
investigation is shown in the above
photosThrusterfor upanddown

Thrusterfor driving
Light

Front camera

Rear camera andlighting

Duringinvestigation

Crawler

Front camera and lighting○Submersible Crawling Robot8©International Research Institute for Nuclear Decommissioning

B2 Investigation at Unit 1 (Videos)9©International Research Institute for Nuclear Decommissioning

A2 Investigation at Unit 2Accretion of the grating

Sediments on CRD rail

Crack of platform grating

Gap between platform
and CDR rail

Deformed platform
1010©International Research Institute for NuclearDecommissioning

A2 Investigation at Unit 2
Inside the pedestal (upper section of platform, middle-right side)
TIP guide pipe support（28-27）

CR34-43

LPRM28-37

CR30-43
LPRM28-45
LPRM guide tube

Cable
damageappears tobe limited
Area where PIP cables and LPRM cannot be confirmed*Image processing: TEPCO Holdings©International Research Institute for Nuclear Decommissioning

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Investigation of the inside the pedestal at Unit 3[Investigation method] Photo shoot by camera[Commencement] July 2017 (target)
CRD
Opening of Pedestal
X-53 penetration

Small underwater ROV
CRD rail

CRD slot
Platform

X-6 penetration
PCV[Investigation route](1) Access from the X-53
penetration.
(2) Going inside the pedestal.
(3) Checking the access route to thebasement floor of pedestal.
(4) Entering the basement floor of thepedestal.

Access opening forworkers[Investigation Items](1) Status of damage on the platform and the lower
CRD.
(2) Presence of obstacles at CRD slot opening.
(3) Conditions of debris accumulated at the bottom ofpedestal.
(4) Conditions of debris from the access opening forworkers to the outside pedestal.

12©International Research Institute for Nuclear Decommissioning

Investigation Device for Unit 3
Submersible Crawling Robot: ”Mini-mambo”
φ125mm、Size Length≦300mm

Thruster for upand-down
Cable

Thruster fordriving
CameraLED right（2.5W×12）
13©International Research Institute for Nuclear DecommissioningVideo images of Underwater ROV at Unit 3

14©International Research Institute for Nuclear Decommissioning

Fuel Debris Retrieval
Technical issues
 Confinement ofRadioactive dust Remote Operation
 Reduction ofradiation dose,
Prevention ofspreading ofcontamination

Submersion - Top entry

Dry – Top entry

Uppertable
上部プラットホーム

カバー吊具
Workingcell

R/B crane

Working cell

Shield plug

使用済燃料プール
SFP

Lower
table
下部プラットホーム

Development of key
technology

Dry – Side entry

SFP

Access device
inside RPV

X6Robot arm

D/S pitAccess rail

Robot arm

1515

©InternationalResearchInstitutefor Nuclear
Decommissioning©InternationalResearchInstitutefor Nuclear
Decommissioning

【PLAN-A】 Side Entry : Access Rail Method
Images of Fuel Debris retrieval (Videos)16©International Research Institute for Nuclear DecommissioningSafety Function

Decontamination

Debrisinvestigation

Safety Function Requirements

PCV repair

DebrisretrievalCollection, transfer andstorage②Nitrogen supply & exhaust gas treatment system

1. Cooling down
2. Confinement (control of negative pressure andwater level in torus room)
3. Deactivation (protection of fire and explosion)
4. Sub-criticality

Nitrogen supply system(RPV deactivation)

PCV gas managementsystem
Negative pressure control,hydrogen scavenging & release

Cleaning

Reactor building gascontrol systemtower

Mitigation of radioactive releaseduring normal operation：First boundary①Circulation cooling & criticality control
systemCirculation coolingsystemWater
treatment
systemBoric acidconcentration
controlsystemDebrisWater Stoppage in the buildings：Second boundary(gas)P

Torus room drainage
systemPrevention of groundwater
reverse, reduction of radioactivity,
prevention of criticality③Ventilation system for the building & cell

P

Undergroundwater

Debris cooling, reduction ofradioactivity

Exhaust system forbuilding and cell

P(Control and release ofnegative pressure)

P：Second boundary(liquid)

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Auxiliary building

Air supply system forbuilding(Maintaining workingenvironment)©International Research Institute for Nuclear Decommissioning

Collection, Transfer and Storage of Fuel Debris
Canister design⇒Response to 1F specific requirements
 High fuel exposure and enrichment → high reactivity
 MCCI → hydrogen generation caused by core concrete interaction
 Injecting sea water, melting cable → effects caused by salt and impurities

Transfer (Dry –side access method）
R/B
Maintenancecell
Storage cellfor fuel debris
retrieval

Carry-outport(additional)

Transport cell

Fuel debris transportbuilding

Handling cell for astorage canister

Storagefacility

Unit canFuel debris
retrieval

Storing incanister

CanisterTransport cart

Washing acanister
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Transport cask

Storing canisterin a transportcask

Trailer

Carrying outa transportcask©International Research Institute for Nuclear Decommissioning

Thank you for your attention!

19©International Research Institute for Nuclear Decommissioning