The 5th International Forum on the Decommissioning of the Fukushima Daiichi Nuclear Power Station

Efforts to Ensure Safety in Decommissioning (No.2)
Spent Fuel Removal
November 1, 2021

Kenji Shimizu
General Manager of ALPS treated water Program

Fukushima Daiichi Decontamination &Decommissioning Engineering Company
Tokyo Electric Power Company Holdings, Inc.

Situation of stored fuel assemblies in SFP (at time of 2011 disaster)

Unit 1

Unit 2

Unit 3

Unit 4

Stored fuelassemblies: 392

Stored fuelassemblies: 615

Stored fuelassemblies: 566

Stored fuelassemblies: 1,535

Spent fuel pool (SFP)Assemblies stored in pool

Example Unit 2

Unit 5

1,542

Unit 6

1,7041

Overview of pool fuel removal
Transport/Storage
Multi purpose cask

Assemblies stored in pool
Unit 5

1,542

Unit 6

1,704

On-Site transport cask
Secure the poolstorage capacity

Unit 1

Unit 2

Unit 3 Unit 4

Common pool

T.P. 8.5 m

Common pool

T.P. 33.5 m

Temporary dry cask
storage facility

Temporary dry cask storage
Concrete modulefacility
Crane2
Dry storage cask

Overall schedule (As of Oct. 2021)
Dec. 2014
Completeremoval▼

Feb. 2021
Completeremoval▼Unit 4Unit 3

FY2024–2026
Start removal▽

Units 1–3: High dose (when fuelremoval roadmap was developed)↓Prioritize Unit 4, which has low
dose levels and large amounts of
SFP-stored fuelUnit 2

Units 1–6
FY2027–2028
Complete
Start removal
removal by end▽of 2031▽
Unit 1

Unit 1: Building coverinstalled
Unit 2: Building escaped
explosion↓
Prioritize Unit 3 after Unit 4

 Units 1/2: Start with Unit 2 before moving to Unit 1, as work preparation
demands
 Units 5/6: Remove within range that has no impact on work of Units 1/2
 All units: Complete removal by end of 2031 (Goal)
3

Unit 4

Schedule for Unit 4
Mid-and-long-term Roadmap (2011): Start removal in 2013
FY2011FY2012FY2013

Start removing fuelPlan▼
Dismantle upper part ofreactor building (R/B)

ResultFY2014

InstallcoverComplete removal▼

Install FHM
Fuel removal

Fuel removal was completed as per goal (Mid-and-Long-Term Roadmap)(1) 7-day/week schedule(2) Shortened inspection process for FHM, crane, etc.
(3) No deficiencies were found in particular(4) No rubble galling, which had been a concern, was confirmed

4Dismantling upper part of R/Band installing cover (1)Area of R/BremovalUnit 4

Area of R/BremovalRefueling floor(5th floor level)

Post-3.11 disaster

Refueling floor(5th floor level)

After removing R/B Despite a hydrogen explosion, Unit 4 had lower radiation doselevels than other units Materials left at the top floor were removed by manned
operations, as such operations were possible.
 The explosion damaged the building framework above theuppermost floor. The upper part of the R/B was dismantled bymanned heavy machinery for dismantling.
5Unit 4

Removing rubble and installing cover (2)FHM
Supportingframe

Approx.
FHM 69 m

CraneSFP
Approx. 53 m

Crane supporting frame

After cover installation
Overview of fuel removal cover The R/B vicinity has relatively low dose levels, which allows for using
common construction methods.

 A cantilever-type cover was used as the cover for fuel removal to prevent
any load on the damaged R/B.
 The pillars and beams had 3 m x 3 m sizes to reduce worker exposure.
Elevator equipment and walkways were installed inside the materials.

6Removing rubble in the pooland installing FHM

Unit 4

Rubble was retrieved piece by piece, using jigs of various sizes/shapes

Rubble retrieval
jigs(21 types in total)
Retrieval of large rubble

FHM installation

Rubble suction

After suction

Manned fuel transfer operations

7

Unit 4

Number of cask transports
Unit 4
1,535 assemblies
71 transfers in total

Common pool

(Most of the new fuel was transferredto Unit 6)

Cannot meet Roadmap schedule withoriginal transfer schedule

Shortened schedule

Removal completed in Dec. 2014!

8Remarks made later by Unit 4 manager

Unit 4

Unit 4 was able to achieve theoriginally scheduled TEPCO’s
Decommissioning Roadmap

Key points for achievement
Relationship of trust is vital to cooperation

Cooperation creates unity
With unity, staff can deliver full performance

TEPCO and 4 othercompanies
cooperated

9Unit 3 had high dose levels

Unit 3

Unit 3 R/B(at time of accident)

Mar. 14, 2011
Unit 3 explodes

mSv/h
Dropped FHM (approx. 20 t)
Dropped roofing

Sediment on fuel10

Unit 3

Fuel removal coverPortal frame and notchedfoundation adopted
Reduce load on upper part of R/B

Crane

Trussed structure anddome roof adopted

FHM

WeightreductionrequiredPortal frame

Notched foundation

Assembly test(Onahama yard)

Reduced 100 t by remodelingfrom blue to orange

11Transition of cover installation

Unit 312

Fuel removal system (Entirety)

Unit 3

Fully-remote-controlled fuel removal[First-ever achievement in the world]

Remotecontrol room
(Main officebuilding)13

Unit 3

Fuel removal system (FHM, crane)
FHM
Moves fuel with fuel gripper
Removes rubble with manipulatorCraneTightens transport cask lid
Lifts transport cask

Fuelgripper

Manipulator

GripperCutter

Transport casket
lifting accessory

Lid tightener

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Unit 3

Schedule (Plan)
Start removal (Original plan)

FY2012FY2013

FY2014FY20154-year delay
FY2016Retrieve rubble,
Install coveretc.
Install FHM

FY2017

Reviewed plan

FY2018FY2019FY2020

Original plan
Fuel removal

Retrieve rubble, decontaminate, etc.

Behind schedule

Install coverInstall FHM

Reviewed plan
Fuel removal

 The plan was to remove fuel from late FY2014 (in Roadmap announced in 2011) Delay in rubble retrieval, decontamination, shielding->Fuel removal started 4
years behind schedule15

Unit 3

Rubble removal and decontamination
Jul. 2013
During rubble retrieval
920 mSv/hNov. 2013
Rubble retrieval
complete
146 mSv/hNov. 9, 2013

Dec. 2016
Shieldingcomplete
1.9 mSv/hMar. 30, 2016

Jul. 2017
During coverinstallation
0.5 mSv/hDec. 16, 2016

 Manned work was impossible before rubble removal, because of high dose
 With rubble retrieval, decontamination, and shielding, dose levels dropped
from 920 mSv/h to 0.5 mSv/h16On-site work(Further revision)
Start removal(Original plan)

Unit 3

Start removal(Actual result)

FY2018About 10 monthCommissioning

FY2019FY2020
Removal complete(Extended)

Fuel removal

Deficiency found in commissioning
BurnFinding from initial removal

Wire
snap

Incorrect voltage setting

Cable quality

Jul. 2018–Mar. 2019

Apr. 2019

Response todeficiency

Start removal
at
1 unit(Voltage setting)(Cable replacement)▼(7 assemblies)

FuelApr. 2019–

Reflection

Interferes withcask and
consumes time

Removalrestarted butwith about 10month delay17Fuel removal (1) (DLTG)
Reflections and KAIZEN (improvement efforts) weremade after removing 1 transport fuel unit (7assemblies)(1) Made general inspection of equipment

Unit 3(2) Moved fixed location ofsuction hose out of fueltransport route(2) Incorporated operational findings intoprocedures(2) Moved monitor to aplace with better visibility

Grow
DLTG cycle
Useful in decommissioning work, in which many variables
are involved and how things turn out are difficult to expect.
Do, Look, Think, Grow

(Do the work and observe/think for better results next time)

DoFuel removal

Reflect Observe
behavior

ThinkLook18

Fuel removal (2) (KAIZEN) Recovered 10-month delay

Unit 3

Changed loading steps
Original plan: Interfered with cask

Interfered with opening
Numerous re-dos

Original plan: Nonspecific procedures
Procedures
1. Visually align2. Lower

Relied on operator
competence･･･

1 hour or moredifference in speed

FuelCask

KAIZEN
After review: Changed shape ofcask opening

Fuel

After review: Procedures do not relyon personnel
Procedures
1. Confirm with camera 105
2. Align with coordinate 12-34･･･

Tapered the shapeof cask opening

KAIZEN
Standardized
used camera
and camerawork
19Fuel removal (2) (KAIZEN) Recovered 10-month delay

Unit 3

Changed tools
Original plan: Install with manipulator

After review: Install with auxiliary hoist

Free movement
Convenient
Fuelpool

Cask

Manipulator
Flange protector(Installed location needsadjustment)

However:
Free movement

More interference/contact
Takes time to check interference

Only elevation,no interference
Plus:
Modified protector(360° installation
now possible)
No need for
adjusting installed
location

KAIZEN(Changed tools)
20Fuel removal (2) (KAIZEN)

Recovered 10-month delayUnit 3

Stopped suction work
After review: Suction onlyflange surface

Original plan: Suction all rubble

Suction unit

Suction in all processes

Cask
Protector

NoleakCask
Cask

Cask

Cask

Maintain
Only flange surface sealing function

Suction: Meant for sealing function
Sealing function: Only flange surface

Suction: Unnecessary for protector surface

KAIZEN(Review procedures)
21

Fuel removal (2) (KAIZEN)

Recovered 10-month delay

Unit 3

Changed operational transitions
Initial plan: (Day) Fuel removal(Night) Retrieve rubble

toTransition

Fuel removal

RemovefuelRetrieverubble

RemovefuelReviewed plan: Day/Night
Fuel removal continuallyRetrieverubble

RemovefuelTransition

Rubble retrieval: All completed in advance
Fuel removal: Done intensively and continually

Reduced time taken in operational transitions

KAIZEN(Changed cycle time)22

Fuel removal (3) (New problem) KAISEN to simple measure
11 fuel assemblies
stuck in racks wereInsertion ofchisel between
rack and fuelunremovable
rack
Fuelrubble

Unit 3ChiselPulling out measuresconsideration

Measure(1)Measure(2)Measure(3)Vibration
generation
Air injection

Rack narrow part
cutting device

Rack cutting
deviceVibration

FuelAir

FuelNarrow
part23

Fuel removal

Unit 3

Recovered 10-month delay
Removal completed in lateFeb. 2021
24

Summary video

Unit 3

Rubble retrieval with manipulator

5x playback speed25Remarks made later by manager (of the time)

Unit 3

With the collective wisdom of the international community, the firstever fully-remote-controlled device was developed for Unit 3. Initial
deficiencies occurred but were recovered through removal operations.

Key points for achieving the planOn-site reflections(Do, Look, Think, Grow)
Determination to follow throughAbove all, unity with partner companies

26

Unit 2

Fuel removal strategy for Unit 2
Install working platform

Install fuelhandling system

Decontamination/Shielding

Start removing fuelFY2024–2026

 Capitalize on existing building and install minimal wall opening
Take in/out fuel removal system through wall opening: Prevent
contamination spread Install fuel removal system after decontamination/shielding
Remotely fuel removal: Reduce exposure
Fuel removal system
On-Sitetransport
cask

Cask handling crane

Front chamber

FHM

Travel cart
Runway girder

Fuel removal platform
SFP27Unit 1

Fuel removal strategy for Unit 1
Install large cover

Retrieve rubble
Decontamination/shielding

Install fuelhandling system

Start removing fuelFY2027–2028

Install large cover for top of R/B: Prevent contamination spreadIn order to reduce exposure, rubble retrieval and decontamination/shielding
before install fuel removal system and fuel removal by local operation

How to safely remove the fuel is a challenge, because some fuel rods havedamage in their cladding tube
Large cover

NN

Fuel removal system

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Final remarks

 Using insights gained through Units 3 and 4, steady efforts
will be made for subsequent fuel removal efforts of Units 1and 2.
 The fuel removal process will be improved daily while
giving top priority to safety.
 TEPCO will follow through on the Roadmap that thecompany promised with society to achieve.
TEPCO and contractors will engage in the decommissioning
work united as a team to keep fulfilling TEPCO’s
responsibilities to Fukushima.

29