ハ2021

る知をSteps for decommissioning at Fukushima Daiichi NPSイロSPECIAL ISSUE
Fukushima PrefectureNuclear Safety
Management Division

L ear n ab o u t deco mmi ssi o n i n g

http://www.pref.fukushima.lg.jp/
sec/16025c/

What is happening NOW in Fukushima.

10 years from the nuclear disaster, efforts for decommissioning at
Fukushima Daiichi Nuclear Power Station

We will look back on the timeline of the accident at TEPCO's Fukushima Daichi Nuclear Power Station and the efforts made over the past 10 years toward decommissioning.

of the accident at1 Timeline
Fukushima Daiichi Nuclear Power Station

Unit1

2011
March 11–15

Unit 2

Unit 3On March 11, 2011, being hit by the powerful earthquake, Fukushima Daiichi Nuclear Power Station lost its
external power supply and the huge tsunami that struck afterwards created damage to the power supply
equipment and cooling equipment. Due to reactor cooling problems in Units 1, 2, and 3, the nuclear fuel wasdamaged, and a large amount of radioactive material was released.

2011Mar11

Mar12Mar13

March 20, 2011 9:30 AM Photo by JASDF

Unit 1

Unit 2

Unit 3

Unit 4Reactor emergency shutdown
Loss of off-site power supply due to earthquake

Reactor emergency shutdown
Loss of off-site power supply due to earthquake

Reactor emergency shutdown
Loss of off-site power supply due to earthquake

Not in operation (no fuel in reactor core)
Loss of off-site power supply due to earthquake

Powerful M9.0 earthquake occurs

Huge tsunami struck (maximum 15.5 m)

Total loss of electricity Loss of cooling/water injection function

Loss of emergency generation

Loss of emergency generation

Total loss of electricity

Mass generation of hydrogen and core damage

Water injection started

Water injection started

Loss of spent fuel pool cooling function

PCV venting (release of radioactive materials) Hydrogen explosion
Loss of water injection function

PCV venting failure

Mass generation of hydrogen and core damage

14Mar 15
Mar

Water injection stopped Mass generation of hydrogen and core damage

PCV venting (release of radioactive materials)

Hydrogen explosion

Release of radioactive materials©TEPCO

Current
status
10 years has changed
the appearancecompletely.

©TEPCOTop floor (Operating floor)

Top floor (Operating floor)

Spent fuelpool

PCVFrontchamber

PCVRPV

RPVShieldApr

Step 1

RPV

Spent fuelpool

Unit 4

Steady decline of radiation dose (Apr 17– Jul 19)

Measured in December 2012
065

©TEPCO©TEPCO©TEPCO0

Jun 27 Reactor circulating water injection started (for fuel debris cooling)

Step 2Started operation of cesium
adsorption device
Completed spraying
anti-scattering agent(to prevent scattering of radioactive materials)(to prevent scattering ofradioactive materials)©TEPCO0

Started sea-side impermeable
wall construction©TEPCO0000000

Site plannedfor waste facilities

0Unit Unit

60Unit Unit Unit Unit

51 2 3 4000000000000000Tank area

00000

● Oct 28©TEPCO0

Measured in January 2021

Soil dump(to start spent fuel removal)

Complete reactor
building cover00● Jun 17

Started rubble removal ● Sep 21(to start spent fuel removal)
Started rubble removal©TEPCO0(Interim storage facility)● Sep 10

● Oct 280000

● Jun 28

Control radioactive material release ;Significant reduction of radiation dose (Jul 19– Dec 16)

1 2 3 40 0 000● Apr 11©TEPCO

Unit Unit Unit Unit

00Unit Unit

Contaminated water managementand other(to prevent diffusion of contaminatedwater outside the port)

OctDecRadiation measurement map (Fukushima Daiichi NPS site)

Installed silt fence

Sep

Nov

Spent fuelpool

Fuel debris

2011 Apr–DecJulAug

PCV

PCV: Primary Containment Vessel RPV: Reactor Pressure Vessel

MayJuneCover for fuel removal

FuelhandlingmachinePCVTEPCO has taken measures for cooling of the spent fuel pool and the reactor and reduction of theradioactive materials release. As a result, temperature of the bottom of the reactor pressure vessel inUnits 1, 2, and 3 have reached under 100°C in December.
Unit 3©TEPCO

Crane

Dome roof

Fuel debris

2 Efforts for reactor stabilization
Unit 2from Unit 3

Hydrogen explosion

RPV

Fuel debris

Unit1

Hydrogen inflow©TEPCO

Spent fuelpool

2011

Unit 40

Multi–nuclide
removal equipment(ALPS)

000(Interim storage facility)(to prevent marine pollution)

Dec 16 Transition to cold shutdown state (RPV bottom temperature approx. 100 °C or less)

Fukushima Prefecture●0 to less than 10 ●10 to less than 20 ●20 to less than 50

Unit: μSv/h ●50 to less than 100 ●100 to less than 500 ●500 and overハLearn about decommissioning

イを 知るロ

Steps for decommissioning at Fukushima Daiichi NPS

1: Dec 2011–Nov 2013
3 Efforts for decommissioning (Mid-and-Long-Term Roadmap) Phase
Phase 2: Nov 2013– present
In December 2011, the national government established the Mid-and-Long-Term Roadmap that defines the basic concept for decommissioning,major efforts necessary to reduce the risk of radiation, and the target processes to be implemented. Currently, the status is in the second phase ofthis Mid-and-Long-Term Roadmap, and continuous efforts toward decommissioning are underway.
2011

Unit 1

2012

Unit 2

Unit 3

Unit 4

Started cover installation[Official name: Mid-and-Long-Term Roadmap towards the Decommissioning of TEPCO’s
Fukushima Daiichi Nuclear Power Station]

Completed removing rubble
on top floor▼ Dec 2021 30–40 years after Dec 2011 ▼▼ Dec 2011

▼ Nov 2013

Until start of spent fuel removal

Until start of fuel debris retrieval Until completion of decommissioning

Phase 1

Phase 2Phase 3©TEPCO● Jul 2012

● Phases defined in the Mid-and-Long-Term Roadmap
Today

Contaminated water management● Apr 2012

Mid-and-Long-Term Roadmap

2013

It is in phase 2,now.

● Nov 2013

Complete● Mar 2013

Completed cover installation● 4 efforts in the Mid-and-Long-Term Roadmap

Started operation of multi-nuclide
removal equipment (ALPS)(full-scale removal of radioactive
material started)

Started spent fuel removal● Dec 2014

Contaminatedwatermanagement

2014

Spent fuelremovalEfforts to remove
nuclear fuel fromthe spent fuel pool

Efforts to suppress
the amoun ofcontaminated water
generation and remove
radioactive materials

2015

Fuel debris
retrieval

Efforts to remove
fuel debris fromthe reactor

Wastemanagement©TEPCO

Started dismantlingbuilding cover● Sep 2015

● Oct 2015
● Nov 2015

©TEPCO● Mar 2017

Completed installation ofaccess gantry andfront chamber

Completed dismantlingbuilding cover

2018

Started freezing land-side
impermeable wall(frozen-soil wall)
Started operation of
miscellaneous solid waste
incineration facility

Started internal
investigation on top floor● Feb 2019

● Apr 2019

First contact with
fuel debris

Started hole drilling workfor PCV internal investigation

2020

Established Prefectural SafetyAssurance Conference● Apr 2019

Completed spent fuel removal(566 assemblies)

3,500

Status on contaminated water generation control（％）
100

3,000

9080

Progress rate

Unit 2500

Unit 1FY2011FY2012FY2013

FY2014FY201560

Monthly average
Annual average
1000

40600

2010392 assemblies
FY2017

Amount of contaminated water generated (m3/day)

5030615 assemblies

FY2016

In order to reduce the inflow of groundwater and rainwater into the reactor
building, multi-layered efforts such as pumping up groundwater and creatingland-side impermeable walls
Layout of Fukushima DaiichiGroundwater flow from
NPS building sitethe mountain side (image)(frozen-soil walls) were taken,
which has helped decrease theGroundwater
Groundwater drain
bypassamount of newly generated
contaminated water to less thanReactor building
Turbine building
one third of that of FY2014 average. Sub-drain

70

Unit 3 566 → 0 assemblies (completed in Feb 2021)

1,000

FY2018FY2019Minami-soma / Naraha Nuclear Disaster
Response Centre opened(Fukushima Prefecture,
11 surrounding municipalities, TEPCO)(assemblies)

1,500● Jul 2016

Concluded a safety assurance agreementAt the time of the accident, a total of 3,108 nuclear fuel assemblies were stored in
the spent fuel pools of Units 1 to 4. Fuel removal in Unit 4 completed in December
2014, and in Unit 3 in February 2021, leaving 1,007 assemblies today, which has
decreased to one third compared to the beginning. (As of March 5, 2021)(completed in Dec 2014)

Completed replace withwelded-type tank

● Sep 2016

Status on spent fuel removal process

Unit 4
1,535 → 0 assemblies● Mar 2019

(Fukushima Prefecture, Futaba-machi,Okuma-machi, TEPCO)

Conducted spent fuel poolinternal investigation

Document provided byInternational Research Institute for
Nuclear Decommissioning (IRID)

Completed freezing land-side
impermeable wall(frozen-soil wall)

Concluded a safety assurance agreement● Jun 2020

Robot for PCV internal investigation● Mar 2018

● Jan 2015

Started spent fuel removal

Completed moving andpacking the equipment
left on top floor

Started operation of solid
waste storage

Assigned local representatives● Feb 2021

● Jan 2020

● Feb 2018

● Apr 2014

Completed dome roofinstallation● Jul 2018

Started removing
rubble on top floor2019● Aug 2013

● Feb 2018

● Jan 20180● Mar 2016

● Dec 2012

Established Safety Monitoring Council● Dec 2017

2,000

Started groundwaterdrain operation
Completed sea side
impermeable wall construction

Efforts by Fukushima
prefecture

Completed removing rubble
on upper part of building

2017

2,500

Started groundwater
bypass operation

Efforts to store
and manage radioactive
waste generated fromthe decommissioningprocess©TEPCO

2021● May 2014

©TEPCO

Started sub-drain operation● May 20152016

Completed spent fuel removal(1,535 assemblies)

FY202000

Land-side impermeable wall
(Frozen soil wall)

Started groundwater drain operation
Started sub-drain operation
average
470 m3/day
average
490 m3/day
Started groundwater bypass operation
FY2014

Fukushima Prefecture

FY2015

Ocean

Sea-side impermeable wall

Started freezing frozen soil wall
Completed freezing frozen soil wall
average
400 m3/day
FY2016average
220 m3/day
FY2017average
170 m3/day
FY2018average
180 m3/day
FY2019average
140 m3/day
2020 Apr–Dec