The 5th International Forum on theDecommissioning ofthe Fukushima Daiichi Nuclear Power StationIssues at the TEPCO’s Fukushima Daiichi NPSfrom the Nuclear Regulator’s Perspective

1st, November, 2021
Shuichi Kaneko
Nuclear Regulation Authority, Japan

１．Major Risk Issues
Countermeasures for Risks which would have an effect on the human and the environment〇Treatment of Stagnant Water in Reactor Buildings etc.
〇Removal and Stabilization of Zeolite Sandbags in basement floors of Process Main Building etc.
〇Transfer and Stabilization of Sludge from Decontamination Equipment〇Measures to prevent structures from collapsing or being damaged by earthquake, tsunami, etc.
〇Countermeasures for other risks which should pay attention to （Risks which effect on offsite are smaller than the above）
・Stabilization of ALPS slurry
・Stable storage of spent cesium adsorption vessel
・Removal of fuels from SFPs of Unit 1 and 21

１．Major Risk Issues
Location of radioactive materials（Mainly Cs-137 ）（spent fuels not included）（unit；PBq） ＊：listed up in the ascending order of stability⑥ 12① 0.4

Process Main Building andHigh Temperature Incinerator BuildingUnit 1～3Cesium adsorption vessel temporary storage facility

22070② 1010250
0.4

⑤ 220
Total amountof Cs-137
560

10～100PBq③ 250<0.001<0.001④ 70

Larger than
100PBq

1～10PBq

Tank area

Concentrated liquid
wasted tank area

①stagnant water

0.1～1PBq
smaller than
0.1PBｑ②Sludge③Adsorption vessel④Shield Plug• Reduction of radioactivity is taken into account assuming that the radiation reduced for 10 years (11th March 2021) from the accident• Total amount of Cs-137 is estimated using 「JAEA-DATA／Code2012-018」 considering reduction• Amount of Cs-137 released to the environment is estimated, referring to 「Additional report of the Japanese government to IAEA－about
the TEPCO Fukushima Daiichi Nuclear Power Station accident －（the second report）」 and considering reduction• This material shows the location of Cs-137 except for spent fuels. However, besides Cs-137, 36 PBq of Sr-90 （in process main building
and concentrated liquid waste tank area）、0.69 PBｑ of H-3 （in tank area） exist.
• Since fraction is rounded up or down, sum of ①～⑥ doesn’t match the total amount.

⑤Cs-137 not included in any of category①～④ and ⑥ （fuel debris, etc.）⑥Cs-137 released to the environment
Concentrated liquid waste
ALPS treated water2

１．Major Risk Issues

Measures for Mid-term Risk Reduction at TEPCO’s Fukushima Daiichi NPS (Main Goals)

Issue

Liquid Radioactive
Material

Spent FuelFiscalYear

Approach toward stopping
water injection to reactor

Design of shielding related tofuel removal from Unit 2, etc.

2021

Advanced approach todecrease the water level in S/Cof Unit 1 and 3

Start installation of additional
dry storage casks

2022

Start fuel removalfrom Unit 6
Process untreatedwater in tanks（continues on and after 2023）

2023

Half the amount and treat
stagnant water in R/B（Establish method to remove α
nuclides until FY 2021）
Furtherfuturegoals

2024
～
2032

Dry up
Process Main Building, etc.
Treat all stagnant water in R/B

Provide shielding in Unit2
R/B Operating Floor andsuppress dust scattering(completed in FY2023)

Solid Radioactive
Material
Install large waste
storage facility (Csadsorption vessel)

Countermeasures forExternal Events

Important Issues to Progress
Decommissioning

Operate analysis facility
on full-scale and build
up structure for analysis

Block the openings ofbuildings, etc.
【tsunami】

Improve workplace environment continuously

Investigate inside
Unit 1 PCV

Widen the paving areaaround buildings【rainwater】(completed in FY2023)

Start operating
additional incinerator

Retrieve fuel debris from
Unit 2 experimentallyand investigate inside
PCV and analyze debris

Install ALPS slurry (HIC)stabilization facility

Install volume reduction
facility and 10th solid
waste storage facility

Reinforce quality management structure ofDecommissioning Project
Investigate and grasp the contamination around theshield plugs

Remove high-dose SGTS pipes in lower
part of exhaust stack of Unit 1 and 2, etc.
Dose reduction under high-dose environment
Take measures to suppress dust scattering frombuildings, etc.

Handle the ALPS treated water (e.g. Discharge
into the sea)(Timing has not been decided)
Consider the effect of the contamination beneaththe shield plugs to each decommissioning works

Start removing Sludge from Decontamination Facility

Install Unit 1 R/B coverStart fuel removal from Unit 5
Expand dry storage cask area
to install additional dry casks
Fuel removal fromUnit 1 and 2
Fuel removal from spent fuelpool of all units

Safety measures for fuel debris retrieval (Timing has not been decided)

Start removal of Zeolite etc. in Process Main
Building, etc.（decide method until FY 2021）
Install analysis building No.2 and other fueldebris analysis facility
Remove rubble stored
outsideControl waste in safer
and more stable stateStore retrieved fueldebris in stablestate

Prevent deterioration andmaintain soundness ofbuildings

Seal outer wall ofbuildings【groundwater】

Countermeasures for Risks which would have an effect on the human and the environmentCountermeasures for Risks which effect on offsite is relatively small, but still should pay attention

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１．Major Risk Issues : Stagnant Water Processing
200 m3/day

100 m3/day

Reverseosmosis
ALPS treated water: Approx. 400m3/day

Source: TEPCO’s material Edited by the NRA

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１．Major Risk Issues : Zeolite Sandbags in PMB and HTI・In Dec. 2018, TEPCO investigated dose rate of the basement floors of PMB and HTI buildings, and detected high dose rate at
the bottom then: 2,600mSv/h in PMB, 800mSv/h in HTI.
・The cause of high dose rate was sandbags containing zeolite installed right after the accident to decrease concentration ofnuclides in contaminated water temporarily stored in PMB and HTI. The highest measured surface dose rate of sandbag wasapprox. 3000mSv/h in PMB and approx. 4000mSv/h in HTI・In PMB and HTI stagnant water shields radiation from the sandbags; therefore, to remove stagnant water alternative shields
are required with the sandbags exposed to the air.
Options to remove or shieldSandbags(when installed)

Status of sandbags in Dec. 2019

investigation in HTI
sandbags
sandbags
openingground floor

Black particles considered to
Status of sandbags in Dec. 2019
be charcoal

first basement floor

second basement floor(bottom floor)① Remote collection
Advantage
・Able to collect at once
Disadvantage
・Need prepare shieldedcontainer and place to store
・Equipment to collectsandbags become high dose

② Remote accumulation toprovisional container
Advantage
・Able to secure storage
space for the time being
Disadvantage
・Need to collect thecontainer later③ Solidification
Advantage
・Able to implement early
Disadvantage
・Difficult to collect later・Sandbags exist in wide
range and difficult to fill all
the area5１．Major Risk Issues : Treatment of Sludge from AREVACountermeasure for 2011 level Tsunami（Block openings etc.）

Plan

Completed on
28/9/2018

Facility to pack sludge
into containers(outside facility)

High dose area
AREVA installed
area

Concrete pit

T.P.8.5m

Pit Ｄ
Basement Floor（Stagnant waterexisting）

sludgeCross-sectional view of PMB
around Pit D

brickcontainer

Above T.P.24.9m

Assumed operation period of outdoor
facility：４～６months

Planning to extract sludge from Pit D, send sludge into
containers outside the building where radiation dose is low,
and then transfer them to higher ground area whose level ishigher than the tsunami height (T.P. 24.9m)

polymermicro-sandsludge

spent adsorption vessel temporary storage
facility（No.4 facility）etc.

Example of contaminated precipitate【Sludge】
Precipitate adsorbed nuclides such as Cs-137 inadsorbent solution.
・Main components ：Barium sulfate(66%)
Ferrocyanides
90
・Major nuclide： Sr（Approx. 3×108Bq/cm3）
・Water content：Approx. 80%
・Amount of sludge：37m3 Source:TEPCO,Edited by NRA

6１．Major Risk Issues : Slurry from ALPSAt ALPS, contaminated water is treated with pretreatment facility and ALPS equipment
in sequence, and 62 radioactive substances are removed (except for tritium).
※ 1：High Integrity Container

System diagram of ALPS (original)

ALPS

Pretreatment facility
Iron coprecipitation
treatment facility
Iron co-precipitation
slurryHIC

Carbonate
precipitation
treatment facility

16 Adsorbents

2 column typeadsorption towers

Iron co-precipitation
Carbonateslurryprecipitation slurry

Carbonate precipitation
slurryHICHIC

Spent adsorbents(water removed after stored in HIC by type)

Main component

System diagram of expanded ALPS

ALPS

Pretreatment facility
Carbonate
precipitation
treatment facility
Carbonate precipitation
slurry

HIC

Source:TEPCO,Edited by NRA

ALPS

18 Adsorbents

Spent adsorbents
HIC (water removed after stored in HIC by type)

expanded
ALPS

Iron co-precipitation
slurry：FeO(OH)･H2O(75%)
Carbonate slurry：
CaCO3

HIC※1
(PE body)

HIC※1（after attaching stainlessreinforcement body）

Concentration ofrepresentative
nuclideAmount ofSlurry※2

90Sr：

1×106Bq/cm3

HIC：386
1008m390Sr：

HIC：9712535m3

4×107Bq/cm3

HIC：11212926m3※ 2：Amount as of 28 May, 2018. The recent number of HICs is 3,632
in total as of 5 Nov. 2020 which store slurry and spent adsorbents.

72．Issues Recently Identified
Basing on the assumption that Cs-137 concentrates under-surface of the upper shieldplug, analytical calculation was made.
Cause of High-Dose Rate at Operating Floor of Unit 1-3
Calculated Amount of Cs-137 beneath the Shield Plug
※1 The shield-plugs had
been dis-located (may be thetime of Hydrogen Explosion.)

0.1-0.2PBq※120-40PBq

30PBq

Unit 1

Unit 2

Unit 3※Analytical calculation ; NRAJ, “Investigation and analysis of the TEPCO's Fukushima Daiichi NPS Accidents”,
Appendix 7-1, p.185, (2021.3.5)
https://www.nsr.go.jp/data/000345595.pdf

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2．Issues Recently Identified
Current Status of Contamination of Hardened Vent System
air conditioning machine room

Unit 1←High dose

Several 1000mSv/h

air conditioning machine room

Unit 2under
0.04mSv/h

0.05mSv/hRD no operated
Hardened Vent System

Base of Main Stack
2～3000mSv/h

RD operated
Hardened Vent System
GD

20～60mSv/h

SGTS pipe merge～6000mSv/h

SGTS

10～50mSv/h

GD～Several～Several mSv/h
1000mSv/h

HEPA

HEPA

Flow of vented gas
Main exhaust duct system（vent system）～2000mSv/h

Main exhaust duct system（vent system）

Contamination level is two orders of magnitude lower compared with Unit
1 and 2.

air conditioning machine room

Unit 3

Unit 4

20mSv/h

50mSv/hRD no operated
Hardened Vent System

RD operated
Hardened Vent System

Base of Main Stack
3mSv/h

0.7mSv/h 3mSv/h GD

HEPA

HEPA

SGTS pipe merge

2mSv/h

5mSv/hNo GD 1.5mSv/h

HEPA

0.04mSv/h

HEPA

Flow of vented gas
Main exhaust duct system（vent system）
air conditioning machine room

10mSv/hMain exhaust duct system（vent system）

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3．Coming Decommissioning Issue : Release of ALPS-treated Water
Measurement/confirmation facility (K4 tank group)

Secondary treatment facility（ALPS）
Secondary treatment of Treated water to be repurified (sum of ratios of legally required
concentrations, excluding tritium, is 1 or higher)

ALPS treated water, etc. tanksComprised of three sets of tank groups each with therole of receiving, measurement/confirmation anddischarge, and continuous discharge is possible（approx. 10,000m3×3 groups）

Transfer pumpRotation

North-South fishing is conducted
3.5km
on a daily basis

UnderseatunnelDischarge
Measurement/Receiving confirmation

Seawall

Flow meter/water flow rate control valve/
Emergency isolation valve(tsunami prevention measure)
Header pipe
(diameter approx. 2m by length approx. 7m)

EL. 33.5m

An area where noN

EastWest
1.5km

Secondary treatment facility（newly installed reverse
osmosis membrane facility）
Secondary treatment of Treated water to be repurified (sum of ratios of legally required
concentrations, excluding tritium, is between 1 and10)

Source: Developed by Tokyo Electric Power Company Holdings, Inc. based on themap developed by the Geospatial Information Authority of Japan (electronicterritory web)https://maps.gsi.go.jp/#13/37.422730/141.044970/&base=std&ls=std&disp=1&vs=c1j0h0k0l0u0t0z0r0s0m0f1

Seawater flow meter

Installed aroundemergency
isolation
valvesandtransferpipes

FutabaTown

The outlet of the undersea tunnel isinstalled within the area where nofishing is conducted on a daily basis,and the assumed quantity of water
within the subject area is approx. 60
billion liters.

Emergency
isolation valve
Discharge pipe

Okuma
Town

Road

EL. 11.5m

Utilize the vertical shaft for thetime being, and initiate discharge
after confirming directly thatseawater and ALPS treated water
has mixed and diluted.

EL. 2.5m

Newly installedseawater pumps(3 units)

Source:TEPCO

Unit 5 intake

Discharge
vertical shaft
Seawater used for dilution（intake from outside the harbor)

Underseatunnel(approx. 1km)

*Area where common
fishery rights are not set10

3．Coming Decommissioning Issue : Release of ALPS-treated Water
NRA’s Review for TEPCO Fukushima Daiichi NPS
Viewpoints of the NRA’s review for ALPS treated water discharge equipment(Tentative)
Review based on the Reactor Regulation Act

The NRA will review the TEPCO’s implementation plan whether it conforms to the regulatory requirements*
including the following (* “Items required for Measures which should be taken at Tokyo Electric Power Co., Inc.’s Fukushima DaiichiNuclear Power Station in line with the Designation as the Specified Nuclear Facility” ):II.9 Treatment, storage, and management of radioactive liquid waste
II.11 Radiation protection, etc. in the area surrounding the site by restricting release of radioactive
materials, etc.
II.14 Design considerations

Confirmation along with the government basic policy

The NRA will confirm whether the TEPCO’s implementation plan is in line with the government basic policy.

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４．Concerns on Future Decommissioning Progress
Waste Generations at 1F Site
Stagnant Water
Water from Underground
Rain Water
Secondary Waste from Water Treatment
Contaminated Rubbles
Fuel Debris and Reactor Structures

Identify human and environmental impact
Control water intake and treated water quality

Requires constant analysis ofwater characteristics

Identify radiological/chemical status
Consideration on handling methodology
Consideration on approaches to tackle core structures

Large increase of analysis
needs anticipatedCapacity of human resource and facility/equipment has to be expanded.
Number of professional staff - recruitment
Capability of skilled staff - training

On-site facility, JAEA (several facilities), and private corporations arecontinuously available; in addition, two facility plans are on going at 1F site.
Adequate deployment of facilities with analyzing capacity is required.

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