2nd Japan –U.S. Decommissioning and Remediation Fukushima Recovery Forum
Tokyo, Japan

R&D activities related to the fuel debris retrieval
from the Fukushima Daiichi NPSInternational Research Institute for Nuclear Decommissioning (IRID)APRIL 9, 2015
*The contents of this presentation include the results of “Establishment of basic technology for decommissioning and safety of nuclear reactors for power generation in 2013(technological study and research concerning forming an idea for processing and disposing of radioactive waste resulting from the accident)“, a project commissioned by the
Ministry of Economy, Trade and Industry, and the 2013 subsidiary for decommissioning and contaminated water measures (development of technologies for processing anddisposing of waste resulting from the accident).
*Plant information included in this document is taken from TEPCO’s official website.

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

Concept image of work steps for fuel debris retrieval■Retrieving the fuel debris submerged in water is a favorable approach fromthe standpoint of minimizing exposure of workers.
■Investigation and repairing methods for filling the PCV with water havebeen studied.
■ Furthermore R&D for the retrieval, packing and storage of fuel debris is inprogress.
■Retrieval method will be chosen from among candidate methods(submersion, in-air, upper-entry, side-entry, etc.,) in 2016.
Retrieval of fuel debris

Repair of lower part of PCV
Water stoppage →Water filling

Overhead crane

Building cover
Fuel debris can container
RPV lid

Spent Fuel
Pool (SFP)

Spent Fuel
Pool (SFP)

Reactor RPV

Filling water

Retrieval

Reactor RPV

PCVStopping water
Torus room

PCV

Torus room

PCV

Torus room
©International Research Institute for Nuclear Decommissioning

2

Fuel removal from spent fuel pool and storage
Removal of
spent fuel etc.
(FY2013-)

Storage of spent
Reprocessing offuel etc.
spent fuel etc.
(FY2013-)
Assessment ofTreatment oflong-term integrity
damaged fuel etc. (1-2)(-FY2017) (1-1)(-FY2017)

Flowchart of R&D on decommissioning /contaminated water
countermeasures in Fukushima Daiichi NPS<Legend>
R&D programs
subsidized by Agency
for Natural Resources
and Energy

Securing work environment (dose reduction etc.)

Secure stable state of the site

Establish does reductionplan(2-(1) 1b)

Develop remotedecontamination system

PCV/RPVstructural integrity
assessment(2-(1) 1a)(-FY2015)(-FY2014)
Complete reduction of dose
inside the reactor building.
(-FY2019)
Supply power source,
communication means, water, etc.

Introduction of decontamination
system to the site.

(FY2014-)

R&D programs founded bysupplementary budget ofAgency for Natural
Resources and Energy
started from 2014

(2-(1) -8)(-FY2016)

Anti-corrosion
measurement(FY2017-)

Debriscriticality control(2-(1) -9)(-FY2019)

Establishmeasures toprevent
criticality(FY2019-)

Conducted by TEPCO(utilizing R&D results)

Flow ofproject

Input
information

The numbers in the brackets, such as(2-(1) -9) indicates project No.

<submersion method (fuel debris retrieval underwater)>(1) Full submersion method (if water can be filled up to the upper portion of PCV)
(2) Partial submersion method (if water cannot be filled up to the upper portion of PCV but handling of fuel debris will be carried out underwater.)Investigation /repair of PCV leakage
Bottom of PCV(vent tube, S/C, torus room etc.)
Development of
Investigation on
investigation
relevant portions
system (2-(1) -2)(FY2014-)(-FY2014)
Development of
repair method(2-(1) -3)(-FY2016)

Identify conditions inside the reactor(debris location, amount etc.)

Repairconstruction(FY2017-)

Upper portion of PCV(hatch, pipe penetration, cooling system etc.)
Development of
Investigation on
investigation
relevant portions
system (2-(1) -2)(FY2016-)(-FY2017)

Internal PCV
Detection of
investigation (2-(1) -4)
radioactive material,(-FY2016)
such as, in S/C.
Investigation
inside(2014-FY2015)
the reactor
Detection of debris(FY2016-)
in the reactor (2-(2)-2)
Internal RPV(2014-FY2016)
investigation(2-(1) -5)
Upgrading of accident(-FY2019)
progress analysis

Fuel debris retrieval*Retrieval method will be determined by 2018.

(-FY2016)
Debris sampling
Debris
Debris characterization (as part of internal
RPV investigation
loading/
RepairDevelopment of
Characterization by
project) (2-(1) -5) transfer/storage
repair method
construction
simulated debris(2-(1) -3)(2-(1) -7)(FY2019)(2-(3)-1)(-FY2018)(-FY2015)(-FY2019)(-FY2017)
Determination<Method applied when submersion method is not applicable Treatment of fueldebris (2-(3)-3)
of actual debris(retrieval in the air)>

RFI fortechnology
information

FS for innovative
approach(FY2014)

Shielding walls on theland side byground freezing method(-FY2014)
ALPS

Maintenanceand control(FY2015-2020)
Start operation(-FY2014)(-FY2019)(-FY2019)(FY2014-)

RFI fortechnology
information

Retrieval of fuel debris/reactor internals (2-(1) -6)(FY2014-2019)

Retrieval of fueldebris(FY2020-)
Carrying-out offuel debris(FY2020-)
Material accountancy(conducted by JAEA withsubsidies granted for
operating expenses)(-FY2019)

Waste treatment
and disposal
Storing of fuel debris(FY2020-)
Storing ofgenerated waste(FY2011-)
Waste treatment
and disposal(3)(FY2011-)

Stable storage ofdebris and wastematerials*S/C: Suppression Chamber

FS for contaminatedwater measurement

S/C: Suppression Chamber(FY2014)・Seawater purification©International
・Capturing radioactive substancesfrom soil.Research Institute for Nuclear Decommissioning
・Decontamination of contaminated water tank storage
・Unmanned Boring3

Development of technology for remotedecontamination inside reactor building(2-(1)-1)

Securing work environment inside the reactor building (dose reduction etc.)
Develop remote decontamination
system(2-(1) 1a)(-FY2015)
Introduction of decontamination
system to the site.

(FY2014-)

Establish does reduction plan(2-(1) 1b)(-FY2014)
Complete reduction of dose inside thereactor building.
(-FY2019)
Supply power source,
communication means, water, etc.

©International Research Institute for Nuclear Decommissioning

4

Dose rate goal for decontamination equipment
 Development goal of the decontamination equipment(the needs for PCV leakage investigation repairing work, and overall dose reduction scenario)

3 mSv/h for work area

5 mSv/h for access route

Unit 1

Unit 2

Unit 3

Used to be 2～60mSv/h(In 2014 Oct, the rates were about

The dose rates are high in whole; about

Needs for
dose
reduction*and thedose rate

The dose rate s are low in whole;
Building
conditions

about 1 to 10mSv/h
The rates have been high in south area,some parts in southeast area
measures5,000mSv/h

5~10mSv/h because of

20～100mSv/h

decontamination in lower/middle
parts and shielding )＊mapping results of the dose rates at planned operation area( with needs of dose reduction) derived from PCV investigation and repair project：3mSv/h to10mSv/h：20mSv/h to 50mSv/h：10mSv/h to 20mSv/h：more than 50mSv/h：out of study due to the lack of data

©International Research Institute for Nuclear Decommissioning

5

Overall Plan（Developed decontamination equipment and development status）
Decontamination equipment for high places
Decontamination
floorsequipment

for

upper

・FY2013：design
・FY2014-2015：production, verification test, applicability study of actual device

・FY2013：design, production
・FY2014-2015：improvement, verification test, applicability
study of actual device

Dry ice blast

Equipment for underground・FY2014：Study of technicalchallenges ,development
planning

High pressure water jet

Suction /blast
Decontamination equipment for low
places＜Development completed＞
・FY2011-2012：design, production, test in 2F
・FY2013 ：improvement, verification test (factory, 1F)

吸引･ブラスト除染装置
Suction/blastHigh高圧水ジェット除染装置
pressure water jet

Dry ice blast

ドライアイスブラスト除染装置©International Research Institute for Nuclear Decommissioning

6

Development of technologies for investigation
and repair (stopping water) toward filling PCV
with water (2-(1)-2 & 3)
Bottom of PCV(vent tube, S/C, torus room etc.)
Development of
Investigation on
investigation
relevant portions
system(2-(1) -2)(FY2014-)(-FY2014)
Development of
repair method(2-(1) -3)(-FY2016)

Repairconstruction(FY2017-)

Upper portion of PCV(hatch, pipe penetration, cooling system etc.)
Development of
Investigation on
investigation
relevant portions
system (2-(1) -2)(FY2016-)(-FY2017)

Identify conditions inside the reactor(debris location, amount etc.)

Internal PCV
Detection of
investigation (2-(1) -4)
radioactive material,(-FY2016)
such as, in S/C.
inside(2014-FY2015) Investigation
the reactor
Detection of debris(FY2016-)
in the reactor (2-(2)-2)
Internal RPV(2014-FY2016)
investigation(2-(1) -5)
Upgrading of accident(-FY2019)
progress analysis(-FY2016)

Fuel debris retrieval*Retrieval method will be determined by 2018.

Debris sampling
Debris
Debris characterization (as part of internal
RPV investigation
loading/
RepairDevelopment of
Characterization by
project) (2-(1) -5) transfer/storage
repair method
construction
simulated debris(2-(1) -3)(2-(1) -7)(FY2019)(2-(3)-1)(-FY2018)(-FY2015)(-FY2019)(-FY2017)
Determination<Method applied when submersion method is not applicable Treatment of fueldebris (2-(3)-3)
of actual debris(retrieval in the air)>

RFI fortechnology
information

FS for innovative
approach(-FY2019)(-FY2019)

Waste treatment and disposal

Retrieval of fuel debris/reactor internals (2-(1) -6)(FY2014-2019)

Retrieval of fueldebris(FY2020-)
Carrying-out offuel debris(FY2020-)
Material accountancy(conducted by JAEA withsubsidies granted for
operating expenses)(-FY2019)

Storing of fuel debris(FY2020-)
Storing ofgenerated waste(FY2011-)
Waste treatment
and disposal(3)(FY2011-)

Stable storage ofdebris and wastematerials©International Research Institute for Nuclear Decommissioning

7

Development of investigation equipment for PCV water leakage
Details of portions to be investigatedOpening outside D/W

７．

Narrow portion
outside D/W

Checking leakage by
raising to aroundopening

Opening outside

Upper portion of
S/C
Operation rack

Inserting long arm through drilledhole to observe opening withcamera

X105B

X106

X54
X53

Equipment
hatch

Reactor building
cross section

Vent tube-D/W joint
Confirming joint by absorbing to vent tube from hole on firstfloor and moving

Torus room wall

Vent tubeD/W joint

S/C

Checking waterleakage by indirect
visual investigation

Vent tube
bellows

Confirming lower portion of S/C
by absorbing it to shell

Upper portion of S/C

Vacuum breaker

S/C
S/C manhole

X2

Checking opening on wall of torus room by moving in the water
Opening on
torus room wall

Checking opening
on torus room
wall with camera
for damage

Checking leakage
by detecting
tracer withultrasonic wave

Water staying

Visually checking
damage thatprevents flooding

Water
staying

X100C X100B X100A

Torus room wall andtriangular corner

Outer surface atlower portion of
S/C

Outer surface atlower portion of S/CDrilling hole on ceiling of small
room and observing opening
through hole

R/B, 1st floor: Position of drilling

R/B, 1st floor

Vent tube-D/W joint

Narrow portion
outsideD/W・エアロック室Checking water at upper portion of S/C
by moving on catwalk

Triangular corner

Checking leakage at
triangular corner

Catwalk

Checking object at
Inserting long arm
upper portion of S/Cthrough drilledwith camera on top of
mast that stretches inhole to checkvertical direction
damagewith©International Research Institute for Nuclear
Decommissioning

Water
staying

camera8

Development of PCV repair technology
Penetration partProtective cover

Cable connector
seal part

Penetration sleeve

PCV upper part
Bellows
Joint box

Electric wiring penetration

Bellows of tube penetration

PCV lower part

Part for repair of PCV upper part
Flange
PCV upper part

Part for repair of PCV lower part
Drywell (D/W)

Vacuum brake line (only UNIT-1)
Vent tube

Suppression chamber

Main steam safety valve vent line

Quencher

PCV wall

Apparatus hatch

Water path
Stopping water part©International Research Institute for Nuclear Decommissioning

9

Development of technologies for investigating
inside of PCV(2-(1)-4)

Bottom of PCV(vent tube, S/C, torus room etc.)
Development of
Investigation on
investigation
relevant portions
system (2-(1) -2)(FY2014-)(-FY2014)
Development of
repair method(2-(1) -3)(-FY2016)

Repairconstruction(FY2017-)

Upper portion of PCV(hatch, pipe penetration, cooling system etc.)
Development of
Investigation on
investigation
relevant portions
system (2-(1) -2)(FY2016-)(-FY2017)
RepairDevelopment of
repair method
construction(2-(1) -3)(-FY2018)(-FY2017)

Identify conditions inside the reactor(debris location, amount etc.)

Internal PCV
Detection of
investigation (2-(1) -4)
radioactive material,(-FY2016)
such as, in S/C.
inside(2014-FY2015) Investigation
the reactor
Detection of debris(FY2016-)
in the reactor (2-(2)-2)
Internal RPV(2014-FY2016)
investigation(2-(1) -5)
Upgrading of accident(-FY2019)
progress analysis

Fuel debris retrieval*Retrieval method will be determined by 2018.

(-FY2016)
Debris sampling
Debris
Debris characterization (as part of internal
RPV investigation
loading/
Characterization by
project) (2-(1) -5) transfer/storage
simulated debris(2-(1) -7)(FY2019)(2-(3)-1)(-FY2015)(-FY2019)
Determination<Method applied when submersion method is not applicable Treatment of fueldebris (2-(3)-3)
of actual debris(retrieval in the air)>

RFI fortechnology
information

FS for innovative
approach(-FY2019)(-FY2019)

Retrieval of fuel debris/reactor internals (2-(1) -6)(FY2014-2019)

Retrieval of fueldebris(FY2020-)
Carrying-out offuel debris(FY2020-)
Material accountancy(conducted by JAEA withsubsidies granted for
operating expenses)(-FY2019)

Storing of fuel debris(FY2020-)
Storing ofgenerated waste(FY2011-)
Waste treatment
and disposal(3)(FY2011-)

Stable storage ofdebris and wastematerials©International Research Institute for Nuclear Decommissioning

10

Development plan for investigation method and device
Set the development plan based on estimated condition of RPV and PCV of Unit 1 to Unit 3 (*1)
Unit 1

Unit 2・Almost all of melted fuel havebeen fallen down to the bottomof RPV plenum and little fuelhave left in RPV.
Development plan
・There is a possibility that fueldebris exists even outside of thepedestal, and investigation
outside the pedestal should be
conducted as priority.

Unit 3・While some part of melted fuels has fallen down to the bottom of RPVlower plenum and PCV pedestal, the other part may have been left
inside RPV.
・Presumed that more fuel than having estimated may have fallen
down to PCV in Unit 3.
Development plan・As the possibility that fuel debris spread outsides the pedestal islower compare with Unit 1, investigation inside the pedestal should be
developed as priority.
・As in Unit 3, the water level inside the PCV is high, penetration which
will be used in Unit 1 and 2 must be submerged, other methods should
be examined.

©International Research Institute for Nuclear Decommissioning*1：[Reference] TEPCO’s webpage Dec. 13, 2013 “The first progress report related to estimated state of reactor core and RPV of Fukushima
Daiichi NPS Unit 1, 2 and 3, and unsolved issues”

11Development Steps of Each Unit (Unit 1)[Investigated area] :- Outside the pedestal on the basement floor- Near the access entrance of RPV pedestal(1) Investigations from the X-100B penetration （～FY2015）: B1, B2(Currently, dose rate near the X-6 penetration is very high.)(2) Investigation from X-6 (FY2016～FY2017): B3(After decontamination near X-6 penetration)

Investigation to obtain information using debris shape measurement apparatus
outside the pedestal on the basement Fl.
B1．Investigation outside thepedestal on the first Fl (grating).

B2．Investigation outside thepedestal on the basement Fl.
X-100BPenet.

Depending on resultof B2 investigation, B3
may be conducted.

Grating(Narrow)opening on
1st Fl.

B3. Investigation outside thepedestal on the basement Fl.
And workers entrance

X-6Penetration(Wide)

Investigation inside the pedestal may
be conducted depending on theinvestigation of Unit 2.

©International Research Institute for Nuclear Decommissioning

Access entrance

12Status of Development (Equipment for outside pedestal)(1)Overview of equipment- Shape-changing crawler equipment- Inserted from the narrow access entrance (X-100B penetration ：φ100mm)- Travel on grating stably.
(2) Image of investigation route
X-100BD/W 1st Fl. grating

X-100B

Traveling through piping

Existing guide piping

Traveling direction
Board camera*Use whentraveling
throughpiping.

Existing guide piping

Composite cable
Crawlertransformation

Traveling on grating
D/W basement Fl
ＰＣＶ
X-6：Investigation route (Plan) （※１）

[Cross Section of PCV]

*１ Investigation route and area are images andmay change depending on the condition of the PCV.

Dosimeter*Installedinside cover

Camera forinvestigation

High dose
rate【Ｄ/W 1st Fl.】

Thermometer*Installedinside cover

Features of equipment

Internal PCV investigation route (Plan)©International Research Institute for Nuclear Decommissioning

13

Development Steps of Each Unit (Unit 2)[Investigated area] : - On the platform (Upper surface of platform, CRD housing)- Basement floor(1) Investigation from X-6 penetration （Φ115mm）（Early FY2015） : A2
(2) Investigation from X-6（Enlarge hole）（FY2016～2017）：A3,A4
・Insert debris visualization system, investigate inside pedestal.
A1. Investigation on
CRD rail(Conducted inAug.2013)

A2. Investigation on
platform inside pedestal

A3. Investigation of CRD Hsg
and on platform(detail)
ＲＰＶ
ＣＲＤ
Pedestal
Opening

A4. Investigation on
basement insidepedestal

CRD railX-6
penetration
Step to use X-6 penetration
・Remove shield in front of penetration
・Pierce a hole to penetration hatch・Remove inclusions inside penetration

Platform

ＰＣＶ

Traveling on
grating of 1st Fl.

Based on the result of internal investigation from A2 to A4, investigation outside pedestal may be conducted.
©International Research Institute for Nuclear Decommissioning

14

Development of technologies for investigating
inside of RPV(2-(1)-5)
Bottom of PCV(vent tube, S/C, torus room etc.)
Development of
Investigation on
investigation
relevant portions
system (2-(1) -2)(FY2014-)(-FY2014)

Identify conditions inside the reactor(debris location, amount etc.)

Fuel debris retrieval*Retrieval method will be determined by 2018.

Internal PCV
Detection of
investigation (2-(1) -4)
radioactive material,(-FY2016)
such as, in S/C.
RepairinsideDevelopment of(2014-FY2015) Investigation
the reactor
repair method
construction(2-(1) -3)
Detection of debris(FY2016-)(FY2017-)(-FY2016)
in the reactor (2-(2)-2)
Internal
RPV(2014-FY2016)
Upper portion of PCV(hatch, pipe penetration, cooling system etc.)
investigation(2-(1) -5)
Upgrading of accident
Development of(-FY2019)
progress analysis
Investigation on
investigation
relevant portions(-FY2016)
system (2-(1) -2)
Debris sampling(FY2016-)(-FY2017)
Debris
Debris characterization (as part of internal
RPV investigation
loading/
RepairDevelopment of
Characterization by
project)(2-(1) -5) transfer/storage
repair method
construction
simulated debris(2-(1) -3)(2-(1) -7)(FY2019)(-FY2018)(-FY2015) (2-(3)-1)(-FY2019)(-FY2017)
Determination<Method applied when submersion method is not applicable Treatment of fueldebris (2-(3)-3)
of actual debris(retrieval in the air)>

RFI fortechnology
information

FS for innovative
approach(-FY2019)(-FY2019)

Removal of fuel debris/reactor internals (2-(1) -6)(FY2014-2019)

Retrieval of fueldebris(FY2020-)
Carrying-out offuel debris(FY2020-)
Material accountancy(conducted by JAEA withsubsidies granted for
operating expenses)(-FY2019)

Storing of fuel debris(FY2020-)
Storing ofgenerated waste(FY2011-)
Waste treatment
and disposal(3)(FY2011-)

Stable storage ofdebris and wastematerials©International Research Institute for Nuclear Decommissioning

15

Study of access route to inside RPVTable Development plan of access technology (sample of access by drilling on the upper section of RPV)No

Development technology
element

1

Boring technology

2

Tube hole expansion technology

3

Remote control technology

4

Boundary constructing technology

Access through piping systems

Issues

2014

2015

2016

2017

2018

Creating access hole for the steam dryer
and separator
Tube expansion for the hole diameter ofsteam dryer and separator
Monitoring the passing on the curve andnarrow part of access route, and operating
condition
Boundary constructing on the operation
floor (sealed plug)

Access via drilling hole on
the upper section of RPV

Access after RPV opened©International Research Institute for Nuclear Decommissioning

16

Access route to investigate inside RPV
Planning investigation of inside RPV (routefor accessing via piping systems)
Feed water system A(Feed water supply
nozzles N4A and B)
OP26601

Result of selection (example of Unit 3)•As systems that have opening to RPV,
- jet pump instrument line,- feed water piping- core spray piping, etc.
•The challenges are- bending of the system piping- opening or closing of the valves of access piping- securing dimensions that allow passage

Core spray (CS) system A(CS nozzle N5A)
OP26131

Jet pump instrumentation
piping (jet pumpinstrumentation nozzle N8)
OP17673

OP14320（Vessel0）©International Research Institute for Nuclear Decommissioning

17

Development of technologies for detecting fueldebris in Reactor(2-(2)-2)
Bottom of PCV(vent tube, S/C, torus room etc.)
Development of
Investigation on
investigation
relevant portions
system (2-(1) -2)(FY2014-)(-FY2014)

Identify conditions inside the reactor(debris location, amount etc.)

Fuel debris retrieval*Retrieval method will be determined by 2018.

Internal PCV
Detection of
investigation (2-(1) -4)
radioactive material,(-FY2016)
such as, in S/C.
RepairinsideDevelopment of(2014-FY2015) Investigation
the reactor
repair method
construction(2-(1) -3)
Detection of debris(FY2016-)(FY2017-)(-FY2016)
in the reactor (2-(2)-2)
Internal
RPV(2014-FY2016)
Upper portion of PCV(hatch, pipe penetration, cooling system etc.)
investigation(2-(1) -5)
Upgrading of accident
Development of(-FY2019)
progress analysis
Investigation on
investigation
relevant portions(-FY2016)
system (2-(1) -2)
Debris sampling(FY2016-)(-FY2017)
Debris
Debris characterization (as part of internal
RPV investigation
loading/
RepairDevelopment of
Characterization by
project)(2-(1) -5) transfer/storage
repair method
construction
simulated debris(2-(1) -3)(2-(1) -7)(FY2019)(-FY2018)(-FY2015) (2-(3)-1)(-FY2019)(-FY2017)
Determination<Method applied when submersion method is not applicable Treatment of fueldebris (2-(3)-3)
of actual debris(retrieval in the air)>

RFI fortechnology
information

FS for innovative
approach(-FY2019)(-FY2019)

Retrieval of fuel debris/reactor internals (2-(1) -6)(FY2014-2019)

Retrieval of fueldebris(FY2020-)
Carrying-out offuel debris(FY2020-)
Material accountancy(conducted by JAEA withsubsidies granted for
operating expenses)(-FY2019)

Storing of fuel debris(FY2020-)
Storing ofgenerated waste(FY2011-)
Waste treatment
and disposal(3)(FY2011-)

Stable storage ofdebris and wastematerials©International Research Institute for Nuclear Decommissioning

18

Overview of muon project (muon observation technology)
Transmission method

Muon

Scattering method

Muon

Muon detector
Incidence
angle

Muon
detector
Object to bemeasured

Object to bemeasuredTransmission ratio is measured.

Emitting
angle: Detection element

Scattering angle is measured.

Identifying ability (fuel debris): About 1 m

Identifying ability (fuel debris) ： About 30 cm

Small-size muon detectors (applicable early)

Large-size muon detectors©International Research Institute for Nuclear Decommissioning19

【Ref.】 Installation image of Transmission method
 Two detectors were installed at thecorner of north side and northwest side
タービン建屋of the Unit 1NR/B
 Measurement started in February, 2015.
Detector Detectors are shielded by 10cm-thickiron plate.

Muon

GroundInstallation
points
設置予定位置
Reactor Building
原子炉建屋
3 layered XＹ detector unit
（１m×1m×1cm）

Detector

Iron shielding

Network switch

Coverbuilding
カバー建屋

Permanent Power Supply

Detector
Y direction

Detector
X direction

20©International Research Institute for Nuclear Decommissioning

The result of estimation of fuels distribution in unit-1
using Transmission method
core
reactor
PCV

The high-density materials (fuels )could not be observed at original
position in core.

21©International Research Institute for Nuclear Decommissioning【Ref.】 Installation image of Scattering Method Detectors will be installed in front of the R/B
and 2 nd Floor in T/B (Operation Floor) at Unit 2
 Background radiation should be eliminated byshielding and algorism.
 The detector in front of the R/B should beshielded by 8cm-thick iron plate.
 Shielding material will not be used in T/B 2 nd
Floor because of the low background radiation.

Measurement sytem2
Measurement system1

Detector X direction
1unit

Block

Data Aggregation PC

Muon

Detector
Y direction

22©International Research Institute for Nuclear Decommissioning

Development of technologies for fuel debris
containing/transfer/storage (2-(1)-7)
Bottom of PCV(vent tube, S/C, torus room etc.)
Development of
Investigation on
investigation
relevant portions
system (2-(1) -2)(FY2014-)(-FY2014)

Identify conditions inside the reactor(debris location, amount etc.)

Fuel debris retrieval*Retrieval method will be determined by 2018.

Internal PCV
Detection of
investigation (2-(1) -4)
radioactive material,(-FY2016)
such as, in S/C.
RepairinsideDevelopment of(2014-FY2015) Investigation
the reactor
repair method
construction(2-(1) -3)
Detection of debris(FY2016-)(FY2017-)(-FY2016)
in the reactor (2-(2)-2)
Internal
RPV(2014-FY2016)
Upper portion of PCV(hatch, pipe penetration, cooling system etc.)
investigation(2-(1) -5)
Upgrading of accident
Development of(-FY2019)
progress analysis
Investigation on
investigation
relevant portions(-FY2016)
system (2-(1) -2)
Debris sampling(FY2016-)(-FY2017)
Debris
Debris characterization (as part of internal
RPV investigation
loading/
RepairDevelopment of
Characterization by
project)(2-(1) -5) transfer/storage
repair method
construction
simulated debris(2-(1) -3)(2-(1) -7)(FY2019)(-FY2018)(-FY2015) (2-(3)-1)(-FY2019)(-FY2017)
Determination<Method applied when submersion method is not applicable Treatment of fueldebris (2-(3)-3)
of actual debris(retrieval in the air)>

RFI fortechnology
information

FS for innovative
approach(-FY2019)(-FY2019)

Retrieval of fuel debris/reactor internals (2-(1) -6)(FY2014-2019)

Retrieval of fueldebris(FY2020-)
Carrying-out offuel debris(FY2020-)
Material accountancy(conducted by JAEA withsubsidies granted for
operating expenses)(-FY2019)

Storing of fuel debris(FY2020-)
Storing ofgenerated waste(FY2011-)
Waste treatment
and disposal(3)(FY2011-)

Stable storage ofdebris and wastematerials©International Research Institute for Nuclear Decommissioning

23

Comparison : Fuel debris in Fukushima Daiichi and TMI 2
・Burnup and enrichment are higher in 1F⇒Radiation, decay heat and reactivity are higher
・Fuel debris in 1F contain molten core concrete interaction product⇒Concern of hydrogen generation due to water radiolysis in concrete
・Seawater injection to the reactor, melting along with the instrumentation cables⇒Effect of salt and kinds of impurities contaminated in the fuel debris
Need to be addressed when designing fuel debris loading, transfer and storage system

Burnup （Reactor core average）
Enrichment（bundle average（max））
Cooling period （minimum）
Fuel debris location

Quantity

Others

１F

TMI-2

About 25.8GWd/t

approx. 3.2GWd/t

3.7 wt%2.96 wt%

About 9 years (as of June 2020）

About 6 years

Inside RPV and PCV （supposition）⇒Molten interaction with concrete andinstrumentation cables as well as fuelconstructional material and internal
structures are supposed to exist.

Inside RPV⇒Molten interaction with fuel constructional
material and internal structures.

－

134.4t（Fuel Assembly）

About more than 450t in total of 3 units

About 122t

（Uranium）（unirradiated）

About more than 260t in total of 3 units

About 82t

Seawater was injected to the reactor－

Debris©International Research Institute for Nuclear Decommissioning

24

Containing, transfer and storage of damaged fuel at TMI-2(Overview of fuel debris handling at TMI-2)
Fuel canister
handling crane(shielded)

Fuel canister handlingcrane (shielded)

Packing fuel debris
Closing cover
Plugging

Fuel canister
handling
crane(shielded)

Decontaminati
on of fuelcanister surface
by spraying
boron water

INL work

TMI-2 work

Transportation cask

Draining water
Injecting inert gas
Plugging

Drain/vent hole

Attaching venttube
Injectingdesalinatedwater

BufferFuel canisterO-ringWork block(Level allowing drainage)

RecoverytankFule canister

Vent tubes

Fuel canisters

Canisters
Shielding coverTransportation cask

Fuel canisters

Transportation cask
Dual container(Sealing canister was notexpected but dual can was
required.)

DebrisFuel canisters

Fuel canister(100Ｗ/can)Reactor vessel

Fuel pool
Fuel canalPacking debris (in water, remote
Loading fuel canister to
Taking out fuel canister
Moving fuel canister Making fuel canister
1979: Accident occurred.
cask(in air, remote)(inair,
remote)(in water, remote) (in water, remote) Moving fuel canister
1985-1989: Fuel taken out(in air, remote)

Fuel container for heating andvacuum drying

Transporting out of site
(Railroad & vehicle)

Taking out canister (in air, remote) & wet storage
1985-2001: Wet storage

Cover
Vacuum drier

Fuel container forheating and vacuum
dryingCanister

FilterHorizontal silo

Canister cover

CanisterCanister coverTransported
Vent tube

Canisters(70Ｗ/can)Sampling hole

Fuel container
for heating andvacuum drying

Fuel canisters
Canister

Fuel canisters
Fuel canisters

Retrieval of fuel canister(in air, remote)1999-2001: Taking out

Fuel canisters

Fuel canisters
Fuel canisters

Heating & vacuum drying

Loading fuel canister to canister(in air, remote)Welding primary & secondary
coversDry storage (horizontal silo)
1999: Dry storage started©International Research Institute for Nuclear Decommissioning25

【Ref.】 Scenario for fuel debris loading, transfer and storage (1/2)
2. Transfer 3. Categorization 4. Transfer(inside the building)(outside the building)

１. Retrieval
TMI-2
experience

1F Planned
scenario：Present distinctiveroute

Submerged
From above

Transfer in
the air

Categorization/
No volume
reduction(1) Submerged
From above(1)Transfer inwater(1)Categorization/
Volume reduction(1)Wettransportation(Outside)(2)Transfer in
the air(2) Categorization/
No volume
reduction(2) Half-dry
transportation(Outside)：Route of possible present
technology：Unreasonable route：Route that needs
technology development：Route of possible present
technology：Route of possible present
technology yet with otherchallenges：Route that needs
technology development
・Major challenges are
written in red(1)Categorization/
Volume reduction(2)Nonsubmerged
From above(3) Nonsubmerged
From side（Same as above(1))（Same as above)(2) Categorization/
No volume
reduction

Half-drytransfer(Out of the site)

Interimstorage(Wet storage)

Temporarystorage(Wet storage)

・Fire management from Hydrogen
・Eluted material from debris
Long-term
direct storage(Dry storage)

When to・establish dry technology（Same as above(2))（Same as above)・construct storage facility
・Securement of storage location
・Technology for categorization and volume reduction©International Research Institute for Nuclear Decommissioning26

【Ref.】 Scenario for fuel debris loading, transfer and storage (2/2)
TMI-2
experience
Half-drytransfer

1F Planned
Scenario
Wet transfer

Half-drytransfer

5. Temporary storage
preprocessing

6. Temporary storage(a few to 30 years)

7. Storage
preprocessing

Vent pipe installation,
desalinated water
injection

Wet storage(wet inside thecanister)(1)Vent pipe
installation,
desalinated water
injection(1)Wet storage(wet inside thecanister)(2) Desalinatedwater injection(2) Wet storage(wet inside the canister)/Pool water wetted part）(3)Water
Injection

・corrosion resistance ofthe canister
・Contaminated water
because of eluted
material from debris(4) Vent pipe
installation(3) Wet storage(half dry inside thecanister)(1)-②Categorization/
No volume
reduction

・Methodestablishment in caseof re-submersion
・Securement ofoperating facility

・Fire management from
Hydrogen・When to constructstorage facility
・Evacuating equipment

・Securement ofstorage location
・Technology for
categorization andvolume reduction

Categorization/
No volume
reduction

Drying

8. Transfer

9. Long-term
storageDry transfer

Horizontal silo
(Vent type)(inside the site)(1)Long-term
storage as wet
・Long-term integrity of the pool

When to・establishment Dry technology
・Construct storage facility(1)-①Categorization/
Volumereduction(1)-①Drying(completedrying)(1)-②Drying(completedrying)(1)-③Drying(in-complete
drying)(1)-④Drying(in-complete
drying)・Establishmentof complete dry
method(2)-①

Dry transfer(inside the site)(2)-②

Dry transfer(inside the site)(2)-③Drytransfer(inside the site)(2)-④Drytransfer(inside the site)(2)Metal cask
(Sealed)(3)Canister(Sealed)(4)Metal cask
(Vent type)(5)Canister(Vent type)・Long-term integrityof vent type canisterand others

Long-term direct storage (Dry storage)(Each step is same as above)©International Research Institute for Nuclear Decommissioning27

Understanding of characteristics by using
simulated fueldebris and development of fuel debris
processing
technologies (2-(3)-1 & 3)
Bottom of PCV(vent tube, S/C, torus room etc.)
Development of
Investigation on
investigation
relevant portions
system (2-(1) -2)(FY2014-)(-FY2014)

Identify conditions inside the reactor(debris location, amount etc.)

Fuel debris retrieval*Retrieval method will be determined by 2018.

Internal PCV
Detection of
investigation (2-(1) -4)
radioactive material,(-FY2016)
such as, in S/C.
RepairinsideDevelopment of(2014-FY2015) Investigation
the reactor
repair method
construction(2-(1) -3)
Detection of debris(FY2016-)(FY2017-)(-FY2016)
in the reactor (2-(2)-2)
Internal
RPV(2014-FY2016)
Upper portion of PCV(hatch, pipe penetration, cooling system etc.)
investigation(2-(1) -5)
Upgrading of accident
Development of(-FY2019)
progress analysis
Investigation on
investigation
relevant portions(-FY2016)
system (2-(1) -2)
Debris sampling(FY2016-)(-FY2017)
Debris
Debris characterization (as part of internal
RPV investigation
loading/
RepairDevelopment of
Characterization by
project)(2-(1) -5) transfer/storage
repair method
construction
simulated debris(2-(1) -3)(2-(1) -7)(FY2019)(-FY2018)(-FY2015) (2-(3)-1)(-FY2019)(-FY2017)
Determination<Method applied when submersion method is not applicable Treatment of fueldebris (2-(3)-3)
of actual debris(retrieval in the air)>

RFI fortechnology
information

FS for innovative
approach(-FY2019)(-FY2019)

Retrieval of fuel debris/reactor internals (2-(1) -6)(FY2014-2019)

Retrieval of fueldebris(FY2020-)
Carrying-out offuel debris(FY2020-)
Material accountancy(conducted by JAEA withsubsidies granted for
operating expenses)(-FY2019)

Storing of fuel debris(FY2020-)
Storing ofgenerated waste(FY2011-)
Waste treatment
and disposal(3)(FY2011-)

Stable storage ofdebris and wastematerials©International Research Institute for Nuclear Decommissioning28

Analysis of characteristics by using simulated fuel debris
Basic policy● Estimating chemical form of fuel debris in reactor, reflecting theresults of the latest plant data at 1F and event progression
analysis● Reviewing items to meet needs by exchanging information withsite and fuel debris retrieval project (same applies to (2) to (5))● Reviewing necessary items in light of needs of other projects
under adjustment (storage/preservation, criticality safety,
measurement management)● Reflecting information and opinions from overseas (SA research,
TMI-2, etc.)● Studying physical properties heavily influencing necessary
methods (such as for drilling) and selecting physical properties
that serve as criteria for selecting simulated fuel debris suitable
for methods● Collecting mechanical property data from major materials offuel debris, by using simulated fuel debris● Gathering wide range of data including composition andinfluences of impurities● Collecting wide range of data in advance, taking various
possibilities into consideration, as many data are needed inearly stage● Assessing influences of reaction specific to 1F by using simulated
fuel debris● Collecting wide range of data, taking various possibilities into
consideration, as analysis of situations in reactor proceeds inparallel● Getting information on MCCI phenomenon and products byeffectively using information and opinions from overseas andinternational cooperation● Obtaining physical property data by using fuel debris from TMI-2●

Estimating fuel debris characteristics based on data andinformation gathered to create a characteristics list

● Proposing simulated fuel debris materials for each method andtechnology by selecting general materials with similar
characteristics that have heavy influence

How to proceed with research(1) Examining TMI-2 information,
SA research information, andFukushima information
Selection of fuel debris whose characteristics
are to be analyzed(2) Study of physical property
of debris needed to besampled and retrieval
Characteristics of fuel debris influencing eachmethodStudy of items of fuel debris
characteristics list (database)Simulated fuel debris characteristics data

Fuel debris characteristics list format(3) Analysis of reaction specific to
1F accident
Data on fluctuation due to reaction at 1F(4) Analysis of property of MCCI
productof MCCI product
Data on characteristics

Estimating and accessing fueldebris characteristics

Fuel debris characteristics
estimating method
Estimated fuel debris
characteristics value(5) Comparison with TMI-2 debris
Physical property data of TMI-2 debris

Creating fuel debris characteristics
list (database)Comparison of characteristics ofgeneral materials

Fuel debris characteristics list

Proposal of simulated fuel debris ©International Research Institute for Nuclear Decommissioning
material for each method andReflecting on debris retrieval Pj, etc.
technology

29

【Ref.】Analysis of characteristics by using simulated fuel debris
Fe-Cr-Ni

ZrB2（Foil-like or (Fe,Cr,Ni)2(Zr,U)flat crystal structure) (Fe2ZrType Cubic）(Fe,Cr,Ni)2B

Arc melting

Oxidative atmosphere(annealing)（ Ar-0.1%O2,1500℃）

Fe-Cr-Ni(Zr,U)O2 (Zr-rich)（Alloy andZrB2Oxidized）

Reaction with control material（ B4 C+SUS) （Example of the melt-solidified material from sectional observation image（Obtained knowledge regarding the composition of solidified material generated when control rod and molten fuel are mixed ）（Estimate hardness distribution for each chemical system of fuel debris (boride, oxide, metal）©International Research Institute for Nuclear Decommissioning30

Development of the criticality management offuel debris(2-(1)-9)

Secure stable state of the site
PCV/RPVstructural integrity
assessment(2-(1) -8)(-FY2016)

Anti-corrosion
measurement(FY2017-)

Debriscriticality control(2-(1) -9)(-FY2019)

Establishmeasures toprevent
criticality(FY2019-)©International Research Institute for Nuclear Decommissioning31

Monitoring sub-criticality and detecting re-criticality
Reactor re-criticality
detection system using
Gas processing FP
gamma
Xe, KrReactor re-criticality
detection system using
neutronSub-criticality monitoring Workers should be protected fromrisk of exposure due to criticality.

R/B

PCV gasprocessing
systemSuction fan

Processbuilding
T/B

Detector
Criticality

Detector

Staying water
Present

FutureReactor sub-criticality
monitoring system using
neutronU, Pu

Re-criticality detection
 Even if criticality isreached in PCV/RPV,
risk of exposure is
extremely low.
 Still, monitoring thesituation in a relatively
wide range is important.

格treatment
Water
本設水処理
system
設備

Criticality
臨界Sub-criticality monitoring
system of liquid waste
treatment and cooling facility

Neutron beam distribution incase criticality in PCV©International Research Institute for Nuclear Decommissioning32

Development of technologies for assessing
structural integrity of RPV/PCV(2-(1)-8)

Secure stable state of the site
PCV/RPVstructural integrity
assessment(2-(1) -8)(-FY2016)

Anti-corrosion
measurement(FY2017-)

Debriscriticality control(2-(1) -9)(-FY2019)

Establishmeasures toprevent
criticality(FY2019-)©International Research Institute for Nuclear Decommissioning

33

Overall structural integrity assessment flow
Building behavior analysis*(building damage simulation)(a) PCV flooding status (example)(assessed in 2012)

Model creation*Input condition proposedby Tepco.

Building-equipment
coordination behavior
analysis・Water level・Basis ground motion Ss
・Damage to equipment
・Influence of corrosion

Putting in order items to be checked
and results expected by conducting
examination when conditions
leading to improvement of accuracyof remaining life assessment, such as
damage of buildings and current
water level (coordination with otherprojects such as to inspect inside
PCV is needed.)

Assessment condition

Organizing loading conditions

・Allowable value・Corrosion wall
thinning (test data)

Equipment strength assessment

・High-temperaturestrength deterioration(test data)

Listing & updating list ofequipment with low
permissible value

Application of corrosion
inhibition(b) Plant condition assumed atpresent (example)

Study of scenario and risk
assessment in case equipmentwith low allowable value bedamagedNo effect(c) Plant condition assumed until
PCV flooding (example)***Stopping water (repair
with grout)

Inputting information to otherprojects (requesting study ofinternal investigation andrepair method**)**Study by experts in equipment design and structure isindispensable and current research and development
system should be reviewed.

: Done in 2012

: Assessed in 2013***Information input from other project “development of technologies for stopping water leaking fromreactor building and repairing lower portion of PCV”

: Conducted or to be conducted from 2012 to 2015

Outline flow of remaining life assessment (example)

Water level in PCV estimated from present
situation and until PCV is flooded (example)©International Research Institute for Nuclear Decommissioning34

Development of technologies for retrieval offuel debris and reactor internals (2-(1)-6)
Bottom of PCV(vent tube, S/C, torus room etc.)
Development of
Investigation on
investigation
relevant portions
system (2-(1) -2)(FY2014-)(-FY2014)

Identify conditions inside the reactor(debris location, amount etc.)

Fuel debris retrieval*Retrieval method will be determined by 2018.

Internal PCV
Detection of
investigation (2-(1) -4)
radioactive material,(-FY2016)
such as, in S/C.
RepairinsideDevelopment of(2014-FY2015) Investigation
the reactor
repair method
construction(2-(1) -3)
Detection of debris(FY2016-)(FY2017-)(-FY2016)
in the reactor (2-(2)-2)
Internal
RPV(2014-FY2016)
Upper portion of PCV(hatch, pipe penetration, cooling system etc.)
investigation(2-(1) -5)
Upgrading of accident
Development of(-FY2019)
progress analysis
Investigation on
investigation
relevant portions(-FY2016)
Debris samplingsystem (2-(1) -2)(FY2016-)(-FY2017)
Debris
Debris characterization (as part of internal
RPV investigation
packaging/
RepairDevelopment of
Characterization by(2-(1)-5)project)transfer/storage
repair method
construction
simulated debris(2-(1) -3)(2-(1) -7)(FY2019)(2-(3)-1)(-FY2018)(-FY2015)(-FY2019)(-FY2017)
Determination<Method applied when submersion method is not applicable Treatment of fueldebris (2-(3)-3)
of actual debris(retrieval in the air)>

RFI fortechnology
information

FS for innovative
approach(-FY2019)(-FY2019)

Retrieval of fuel debris/reactor internals (2-(1) -6)(FY2014-2019)

Retrieval of fueldebris(FY2020-)
Carrying-out offuel debris(FY2020-)
Material accountancy(conducted by JAEA withsubsidies granted for
operating expenses)(-FY2019)

Storing of fuel debris(FY2020-)
Storing ofgenerated waste(FY2011-)
Waste treatment
and disposal(3)(FY2011-)

Stable storage ofdebris and wastematerials©International Research Institute for Nuclear Decommissioning35

R&D policy
1 Method for fuel debris retrieval
The status differs from unit to unit.
→In addition to the method in which the PCV is submerged(full submersion),partial
submersion (the upper part of the PCV is not submersed) or retrieval in the air (partial
in-air, full in-air) should be evaluated for comparison.
→ After sorting out the status and presumption, applicability of each method for theeach unit will be evaluated.

2 Technologies for fuel debris retrieval
There is not evidently applicable or confirmed technologies to the plants in Fukushima
daiichi NPS.
→There are some examples such as the fuel debris retrieval conducted in TMI-2 andlarge repair works in domestic plants. Proven technologies will be focused.
→ However, since the core internals might not be in the form of the original design,development of applicable technologies will be implemented presuming such situation.
©International Research Institute for Nuclear Decommissioning36

Development of technologies for retrieving fuel debris and core internals◎ Retrieval method study
Based on required information on the plant status,
development of related technologies, andinvestigation results, etc.., to study total scenario.
→ Many information will be comprehensively
evaluated and unclear points should beassumed.
→ To be studied by the national project , including
existing technical investigation.

Cell, etc.

◎ Problems to development oftechnologies to retrieve fuel debris
Problems common to retrieval of fuel debris,regardless of the technical methods, are as follows:

Work cart

1) Cutting fuel debris
2) Remote operation
3) Prevention of expansion of contamination
4) Shielding5) Criticality prevention

SFP debris
canister

DSPLong arm◎ Element test

Cutter, camera,
handling tools

Of the above problems, elements for cutting fueldebris, remote operation, and prevention of
expansion of contamination to be tested.
(1) Cutting fuel debris
1) Test to cut ceramic specimen
2) Production of specimen(2) Remote operation
1) Long arm control technology
2) Test models production of remote operatedarm (including in cell)(3) Prevention of expansion of contamination
1) Selection of isolation film sheet

Isolation film sheet
Shielding

Remotely operated arm（

Image of Retrieval method©International Research Institute for Nuclear Decommissioning37

Fuel Debris Retrieval
Operating device(Shielding plug)

100t class polar craneBarrierContainer

Ventilationequipment

Operation floor
Operating device(telescope etc)

Spent fuel pool

DS pitOperatingdeviceCutting device
Visual device
etc.

RPV

Ventilation equipment

PCV
約35m

Extension/contraction

Major issues
・Ensure boundaries
・Setting precision of therotating plug・Control of repulsive force
during cutting

Torus room

Research InstituteFig. Method to retrieve fuel debris in air by©Internationalrotating
plugfor Nuclear Decommissioning

38

Fuel debris retrieval
100t class polar craneOperating device(gate type crane etc. )Ventilationequipment

Container
Operation floor
Spent fuel pool

Barrier with shielding
function

DS pitCutting device
OperatingdeviceVisual device
etc.

Descending platform

RPV
Ventilation equipment

PCV

Major issues
・Ensure boundaries
・Radiation shielding
during operations

Torus room

Fig. Method to retrieve fuel debris in air by descending
work platform©International Research Institute for Nuclear Decommissioning
39

Fuel debris retrieval
100t class polar crane

Major issues
・Ensure boundaries
・Radiation shielding
during operations
・Location of entrance
opening

Container
Operation floor

DS pitSpent fuel pool

Existing equipment hatch/new
opening

Operating device
Cutting device
Visual device etc.

Barrier with shielding
function

RPV

Ventilationequipment

PCV

Torus room

Ventilationequipment
Operating device
Operating device

Access routeFig. Method to retrieve fuel debris in air from
theside©International
Research
Institute for Nuclear Decommissioning40

Finally, - Toward retrieving fuel debris Retrieving fuel debris of Fukushima Daiichi is expected to be
more difficult than TMI-2. It is therefore necessary to gather
knowledge and information domestically and internationally fordeveloping overall strategy for fuel debris retrievable.
 To retrieve fuel debris, it is necessary to make a plan bestsuited for the entire related projects and to develop
technologies flexibly while making clear the purpose and goalof each project.
 To formulate a strategy, it is important to consider the end
state (what should be done in the end) and study various
feasible options. As a result, it is important always to prepare
alternatives, as well as the first idea.
©International Research Institute for Nuclear Decommissioning

41

Backup Material

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 Decommissioning42Current status of lower
part of PCV 【Unit 1】
LeakageVacuumdestructionline

Ｄｒｙ ｗｅｌｌ（D/W）

【ｐｉｃ①】①Confirm Leakage from thebellows portion of
vacuum break line
(See pic①)

R/B １ｓｔ OP.10200

Ｗａｔｅｒ ｌｅｖｅｌ
OP.9000（Ｄｅｐｔｈ 3m）

１

Vacuum break line

Suppression
chamber（S/C）②Confirm running water fromthe sand cushion drain line
(See pic②）

Fuel debris(Place , distributionand , shape areunknown２

Sand cushion drain
line
Confirm
runningwater【ｐｉｃ②】→To pump
Torus room

Strainer（R/B basement FL)TEPCO data

©International Research Institute for Nuclear Decommissioning

43Current status of lower part of PCV 【Unit ２】

Water level

R/B 1st FL OP.10200

OP.5824（Depth 30cm）

300A-AC-10

Dry well（D/W）

Not confirm running waterleakage from
①Vent tube sleeve（See pic①）②Sand cushion drain line
（See pic②）③ Bellows cover（See pic③）

Fuel debris
500A-AC-1(Place , distributionand , shape areunknown

Suppression
chamber（S/C）
１
３

４

２

④Confirm that the waterlevels of inside and outside
S/C are almost the same

Strainer【Pic①】→To pump（R/B basement FL)【Pic②】

Torus room
【Pic③】TEPCO data

©International Research Institute for Nuclear Decommissioning44Current status of lower part of PCV 【Unit ３】
Main steam pipeＣ

Dry well（D/W）

bellowsＣ

Water level１

R/B １ｓｔ OP.10200

OP.12000（Depth 6.5m）
Assumed from pressure【Pic①】

difference between
D/W and S/C

Suppression

Leakage①Confirm leakage frombellows of the main steam
pipe in the room of main
steam isolation valves( See pic①）

chamber（S/C）
Fuel debris(Place , distributionand , shape areunknown

Strainer

Torus room

→To pump（R/B basement FL)

Sump Pit
TEPCO data

©International Research Institute for Nuclear Decommissioning45