ハイる知を

September 15,

Steps for decommissioning at Fukushima Daiichi NPSロ2019

Vol. 10

Next issue schedule: December 15, 2019

Fukushima Nuclear
Safety Measures 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.

CONTAMINATED WATER
Contaminated water refers to water that contains highly-concentrated
radioactive material which generated when rainwater, groundwater, or
water to cool the reactor touched the fuel debris that has melted down
due to an accident (formally stagnant water containing radioactivematerials). These are accumulated in the reactor building and theturbine building.

Remove the contamination source(radioactive materials)

In order to remove radioactive materials from the contaminated waterremaining in structures such as the reactor building, the contaminatedwater is treated in multiple purification facilities including multi-nuclide
removal apparatus (ALPS).
We see there arethree main processes
for treating
contaminated water.

１00 Bq / L

STEP. 2

To water desalinationequipment

TOSHIBA

4×1 system

SARRY ⅡMAX(4 vessels in total)

Simultaneous adsorption of cesium and strontium

600 t/dayTOSHIBA

CmovalReB(ALPS)

Return to reactor building

Reactor buildings
Turbine buildings(core circulation water injection)

Cesiumadsorption
device(excluding tritium)

Simultaneous adsorption of cesium and strontium

1,200 t/day

Multi-nuclide removal equipment

AUnit

4

Activity
concentration
up toUnit

Unit

2

3

S T E PP.. 21

WATER DESALINATION EQUIPMENTHITACHI

about

4,570

To multi-nuclide
removal equipment[ALPS]

m³/dayReturn to reactor building

Fresh water (+ radioactive material type)(core circulation water injection)

about

Cross section

40% to 50%

30 cm

Water desalination equipment

movalReⒸTEPCO

Approx.

CS T E P. 3

C-1.Multi-nuclide removal equipment(existing ALPS)TOSHIBARadioactive materials are removed by two precipitation
treatments and 7 types of 16 adsorption vessels. The officialname is a multi-nuclide removal equipment

orPretreatment
STEP. 2B

(iron coprecipitationtreatment)

Add chemicals Add chemicals

Fromdesalinationequipment

750Pretreatment(carbonate precipitationtreatment)

Iodine / Cobalt

Cesium｝ ｝

RemovalIodine / AntimonyIodine

m³/dayRuthenium
Ruthenium

Remove cobalt,manganese,etc.

Remove calcium,magnesium,etc.

Pass through 7 typesof adsorption vessels

To ALPS-treatedwater tank

Radioactivematerials can befurther removedby three types ofALPSs.

C-2.Extended multi-nuclide removal equipment TOSHIBA

C-3.High-performance multi-nuclide removal equipment HITACHIRadioactive materials are removed by one precipitation
treatment and 7 types of 16 adsorption vessels. The generation
amount of radioactive waste canbe reduced by performing
precipitation only once.

Radioactive materials are removed by 2 types of 4 filters and6 types of 18 adsorption vessels. The removal performance isthe same, but theamount ofradioactive
Remove suspended substances (waste)materials can begreatly reduced
Rough removal of cesium and strontium
as no precipitationis performed.

STEP. 2Strontium

Concentrated
salt water
Fresh water

4 - 6mMULTI-NUCLIDE REMOVAL EQUIPMENT (ALPS)(extended ALPS)(ALPS for Advanced Liquid Processing System)

C

50% to 60%

Overall maximum throughputⒸTEPCO

STEP. 3

Concentrated salt water,

Cesium adsorption device

１00

Ace water treatment(20 are installed on the 2nd floor of the No. 4 turbine building)

A1

Treated water
will go to the water
desalinationequipment

The seawater contained in contaminated water must be removed to prevent
corrosion of equipment and facilities. Water desalination equipment removes
salt by passing contaminated water through a reverse osmosis membrane.
The water from which salt has been removed is reused as cooling water for the* 50 desalination installations in total
reactor.

STEP. 1Unit

million Bq / L

High-performance ALPSB

5×2 system(10 vessels in total)

SARRY

C-1

１0 million Bq / L(16 vessels in total)

MAX

Cesium adsorption device (SARRY Ⅱ)

C-3

Activity
concentration
up to8×2 system

Cesium adsorption

Strontium adsorption

600 t/day

Kurion(US)C-2

B

Cesium and strontium are removed first since they are most of the radioactive
materials contained in the contaminated water.

KURIONⒸTEPCO(excluding tritium)

Strontium treatedwater tank
Water desalinationequipment

A CESIUM ADSORPTION DEVICES T E PP.. 1MAX

Radioactive materials derived from nuclear
fuel (uranium) such as cesium, strontium,iodine, manganese, cobalt, antimony, andruthenium.

From reactor building /turbine building

Activity
concentration
up toALPS-treated water tank

moval
Re

Main radioactive materials
contained in contaminated waterB

From
desalinationequipment

750

Pretreatment(carbonate precipitation treatment)

m³/dayAdd chemicals｝
Remove calcium,magnesium,etc.

Iodine / Cobalt
Strontium
Iodine / Antimony

RemovalIodineCesiumRuthenium
Ruthenium
Pass through 7 typesof adsorption vessels

To ALPS-treatedwater tank(High-performance ALPS)or

Cesium / Strontium

STEP. 2B

From
desalinationequipment

750

RemovalManganese / Cobalt
Iodine / Antimony
IodineRuthenium

m³/dayRuthenium

Pass through 2 types of filters and To ALPS-treated
6 types of adsorption vessels
water tank

See back for detailed explanation on ALPS-treated water

Fukushima Prefectureハイ

Learn about decommissioning

ロを 知る

10Vol.●

Steps for decommissioning at Fukushima Daiichi NPS

The amount of ALPS-treated water stored
ALPS-treated water is referred to water which most of the radioactive materials besides tritium (hydrogen-3) areremoved through the multi-nuclide removal equipment (ALPS). As of the end of June 2019, 1.01 million tons ofALPS-treated water have been stored.The activity concentration of ALPS-treated water meets national criteria
to be stored in tanks within the power plant site (effective dose less than 1 mSv/y at the site boundary), but mostof the concentration does not meet the concentration limit determined in the public notice (National criteria torelease radioactive materials to the environment). As the ALPS cannot technically remove tritium, thegovernment is currently working toward a solution on how to handle the tritiated water and the social aspects.

What is tritiated water?

What is tritiated water?

Normal water (Fig. 1) consists of one oxygen and two hydrogens, while
tritiated water (Fig. 2) consists of one oxygen, one hydrogen and one
tritium.
Fig. 1hydrogen

65,000tons

hydrogen1.01 162,000

tritium

Water molecule of tritiated water (HTO)

Fig. 3Fig. 4oxygenhydrogenhydrogenoxygenhydrogen

When you close up

Ratio to concentration limit: 100 - 20,000

TotalhydrogenoxygenWater molecules of normal water (H2O)

1000 tons tank x 10 units = 10,000 tons
The amount of ALPStreated water stored

Fig. 2oxygentritium

When you close up
electronneutron

protonelectron radiation

proton neutronradiation

Ratio to concentration limit: 10 - 100

million tons

Hydrogen atom

Tritium (Fig. 4) is a combination of one proton and one electron of hydrogen(Fig. 3) plus two neutrons.It looks like hydrogen, but it emits radiation
because of its unstable nature.

tons“How much is1.01 million tons?”

554,000
tons
Ratio to concentration limit: 1 - less than 10

Why is tritiated water generated?

When the nuclear fuel uranium undergoes fission, trace of tritium
atoms are generated, and they become tritiated water by getting
together with oxygen and hydrogen.

229,000
tons
Less than the concentration limit“It is about 80%of the volume ofTokyo Dome!”

Radioisotope of hydrogen atom
“tritium” = “hydrogen-3”

Why can’t it be removed?

Although tritium is slightly heavier than hydrogen, it has almost thesame chemical properties as hydrogen and is not easy to separate
or concentrate. It is considered difficult to remove only tritiated waterfrom ALPS-treated water with current technology.
* Data as of the end of June 2019

The 10 DATA MONITORED BY FUKUSHIMA PREFECTURE
In Fukushima Prefecture, various data, such aswhether fuel debris and spent fuel are properlycooled or whether there are no abnormalities in
the internal temperature and pressure aremonitored to confirm that the steps toward
decommissioning are proceeding safely.

Spent fuel pool and skimmer surge tankskimmersurge tankBA

* Data as of August 16, 2019

Nitrogen gas
separatorF

We monitor whether the nuclear fuel stored in
the spent fuel pool is cooled stably and whether
the circulating cooling is maintained.

Reactor pressure vessel

Spent fuel pool

Strontium
treated water

ExhaustI J
Hydrogenconcentration meter

CRadiation monitor

EInternal gas

H

Reactor containment vessel

Unit 1 34.4℃
Unit 1 36.9℃

B Skimmer surge tank water level●Spent nuclear fuelD

Unit 1 33.8℃

Spent nuclear fuel

Pump

Nitrogen injection

A Spent fuel pool water temperature●(appropriate range: Unit 1 60℃ or less, Unit 2 or 3 65℃ or less)Spent fuel pool

High performance
particle filter

GTurbine building
Fuel debrisWe monitor whether the spent fuel pool(hereinafter referred to as the pool) maintains afull water condition. A skimmer surge tank(hereinafter referred to as a tank) is a tank that is
installed next to the pool to collect overflow waterand return it to the pool. If the tank water level is
0m or higher, it indicates that the pool is full.

Unit 1 1.79m
Unit 2 3.57m
Unit 2 3.03m

C Bottom temperature●(appropriate range 80℃ or less)

Unit 1 26.4℃

We monitor whether fuel debris in the reactor
pressure vessel is stably cooled.

Unit 1 28.7℃

D Water injection status●

We monitor whether water is being injected soas not to increase contaminated water whilestably cooling the bottom of the pressure vessel.

Unit 1 34.1℃

Unit 1 3.00㎥ /h
Unit 2 3.04㎥/h
Unit 3 3.05㎥/h

E Reactor containment vessel pressure●
F Nitrogen injection amount●
We monitor whether a sufficient amountof nitrogen gas is continuously injected
to prevent hydrogen explosion.

Unit 1 28.13N㎥/h
Unit 2 13.35N㎥/h
Unit 3 16.87N㎥/h

H Gas management system exhaust flow rate
●The gas in the reactor containment vessel ispulled out through a filter and released, andthe internal pressure is adjusted bycontrolling this amount and the amount of
nitrogen injected into the vessel. We confirm
it by monitoring the exhaust amount.

Notice about
NuclearDisasterPrevention
Drill

Unit 1 20.8㎥ /hUnit 2 18.7㎥/h
Unit 3 18.3㎥ /h

G Reactor containment●Unit 1 26.5℃

vessel internal temperature Unit 2 32.0℃

We monitor whether the fuel debris
which leaked from the pressure
vessel is sufficiently cooled.

Unit 3 29.9℃

When the internal pressure is low, external air(oxygen) enters the interior and mixes with hydrogen Unit 1 0.72kPag
which will increase the risk of hydrogen explosion.
Unit 2 3.82kPag
Therefore, nitrogen is injected to increase the airpressure inside. On the other hand, if the internal
Unit 3 0.39kPag
pressure is too high, there is an increased risk ofinternal dust leaking outside, which is why we needto keep monitoring the pressure.

I Hydrogen concentration●(appropriate range 2.5 vol% or less)

J Activity concentration●(appropriate range 1Bq/cm3 or less)

We monitor whether theUnit 1 Less than detection limithydrogen concentration ismaintained at 2.5 vol% or less Unit 2 0.02vol ％as hydrogen explosion occurs
Unit 3 0.06vol ％when it exceeds 4.0 vol%.

We monitor the criticality by measuring
the activity concentration as the activity
concentration of the internal gas rises
when the fuel debris reaches criticality.

To be prepared in case we face a nuclear disaster, Nuclear Disaster Prevention Drill is carriedout every year in Fukushima Prefecture. This year, it is conducted the drill based on thescenario that the function to cool spent fuel was lost at the Fukushima Daiichi NPS due tothe earthquake. During the training, we will conduct an emergency information distribution
training using emergency alert email, publicity cars and local government wireless system.
We ask for your understanding and cooperation to this drill.

Fukushima Prefecture

Unit 1 0.00114 Bq/㎤Unit 2 Less than detection limit
Unit 3 Less than detection limit●Emergency alert email

October 16 (Wednesday) from 10:00 am to 4:00 pm/Naraha-machi and surrounding area

●Other emergency information distribution training

October 16 (Wednesday) from 10:00 am to 4:00 pm／Tamura City (Miyakoji-machi) and Naraha-machi
November 16 (Saturday) from 7:00 am to 8:00 am／Tamura City (Miyakoji-machi)