Chernobyl - Fukushima

LESSONS ARE LEARNT FROM NUCLEAR DISASTERS?

Chernobyl and Fukushima: similarities and differences about theaccident process, the radioactivity release and the consequences
Cs137 deposition
Bq/m2
１0k～３0k
３0k～100k
100k～300k
300k～1M>1M

200km

Cs-137 contamination aroundthe Chernobyl NPP

Imanaka T.

Tokyo
200km

Cs-137 contamination around theFukushima-1 NPPKURNS, Kyoto University
April 9, 2019
European Parliament
Brussels, Belgium

1Self-introduction

5048

2011 Fukushima accident

2016 Retirement201634201120062001

1986 Chernobyl accident

1979 TMI accident

1999 Tokai-mura JCO accident

19960555 54 54

42131081991

13442403828

1986

10363333

494653 52 53 53181981

202523221976

30

1971

40

1973 Graduate school of TIT

I969 Entrance into Osaka Uniersity

50

1966

Total output of NPP in Japan, GW

60

1976 Researcher of Kyoto Univesity

Born in Hiroshima in 1950
Entered into Nuclear Engineering Course of Osaka University in 1969
Started a researcher of Research Reactor Institute, Kyoto University in 1976
Retired Kyoto University in 2016. Since then, a part-time researcher of thesame institute1950 Born in Hiroshima City-Total output and number of nuclear power plants in Japan2

14:46 on March 11, 2011, a giant earthquake(M9.0) occurred at 180 km from Fukushima-1
NPP.

Three simple slogans at the time ofreactor emergency in Japanese
1. TOMERU: stop fission chain reaction atthe reactor core

2. HIYASU: cool residual heat in the reactor
vessel

3. TOJIKOMERU: contain radioactivity
inside the containment

15:36 March 12.
Hydrogen explosion at #1

A vanished plan to construct coastal dyke
against tsunami in 2008

Two years ago, at the criminal trial for three executives of TEPCO,
it became uncovered that a plan was considered in 2008 against
tsunami over 10 m, but it was crushed away by those executives.

11:01 March 14,
Hydrogen explosion at #3

In case coolant water could not be sent
to the reactor core
Temperature and pressure rise

Safety release valve open andcoolant decrease

Containment rupture or Steam explosion（or China syndrome）

Melt-through（Pressure vessel melt)

Decrease of core water level

Fuel rod exposure and temperature rise

Melt-down（Fuel core melt）

Zr-water reaction, H2 productionRadioactivity release in the coolant
8Structure of BWR

911am on March 15th, 2011

Press conference by the prime minister andthe cabinet secretary“Hydrogen explosion occurred also at #4 and thecontainment of #2 was ruptured”
I was convinced that Fukushima accident became
like Chernobyl.
10

Evacuation instruction from thegovernment
21:23 March 11. Evacuation within 3 km
 05:44 March 12. Evacuation within 10 km
 17:39 March 12: Evacuation within 20 km
 11:00 March 15: Stay inside houses between 20-30km
Fukushimaprefecture11

Daily release of radionuclides intothe atmosphere. PBq=1015 Bq
30I-131

25

Cs-134 + Cs-137

20
15
10
50

12th
13th
14th
15th
16th
17th
18th
19th
20th
21th
22th
23th
24th
25th
26th
27th
28th
29th
30th
31th

Daily release, PBq /day35

March 2011
Based on the data by Katata et al, 201512

It was clear that serious
contamination occurred around theFukushima-1 NPP.
However, strangely almost noinformation was released from theauthorities!

We decided go to measure thecontamination by ourselves!
13First visit to Iitate village on March 28, 2011

Radiation survey team14Radiation Survey in Iitate Village
on March 29th, 2011

Nagadoro-magata 30μSv/h

I have been working at a small research reactor of Kyoto
University. Inside the reactor, places where dose rate exceed
20Sv/h, are “High radiation zone”.
Iitate villagers were living in such a radiation condition!
15

Radiation level map of Iitate village
March 29, 2011

Measured with ALOKA-PDR-111
16

Evacuation of Iitate village was issued on April 22, morethan 1 month later the contamination happened

Cs137 contamination map on the ground.
Made from US NNSA aerial survey data,Evacuation area

Total evacuated area: 1,150 km2 81,000 persons 17

Radiation survey in Iitate village
2011～2015

2011/3/29

2011/10/5

2012/3/27

2013/3/17

2014/4/26

2015/3/26
18

Average dose rate in village、
μSv/h

Temporal change of average dose rate inIitate village
12.0
11.0
10.0
9.0
8.0
7.0
6.0
5.0
4.0
3.0
2.0
1.0
0.0

10.8

Measured
Theoretical decrease

2.76
2.61

2011

2012

2.17

2013

1.74

1.24

0.82

0.60

0.55

2014

2015

2016

2017

2018

-Radiation level decreased to 1/20 during these seven years.
-Black dot line indicate theoretical decrease due to physical decay ofradionuclides.
-The effect of decontamination seems to be about 2.

19

Transition of evacuation and evacuation
preparing zones

April 22, 2011
Evacuation zone:1,150 km2
81,000 persons

April 1, 2017
Evacuation zone: 370 km2
24,000 persons

20Radiation survey around houses after
decontamination in order to prepare lifting
evacuation in spring of 2017



May 20, 2016: 55 houses in MAEDA
Oct 9, 2016: 125 houses in KAMI-IITOI
Nov 24, 2016: 48 houses in WARABIDAIRA
Nov 24, 2016: 21 houses in
KAYAKARINIWA
We measured 4 points
around every house Front road
 Entrance Garden Back of main house21Summary of house survey in 2016
Average dose rate、 μSv/hSettlement

No ofhouses

Maeda

55

0.68

0.42

0.60

0.78

Kami-Iitoi

125

0.48

0.37

0.51

0.68

Warabi-Daira

48

0.99

0.79

1.01

1.13

Kayakariniwa

21

0.86

0.65

0.93

1.09

FrontroadIn frontofGarden
Entrance

Back ofmainhouse-Current (2019) radiation level around decontaminatedhouses is 0.4 – 0.8 Sv/h.
-Annual dose of people living such areas is estimated to be2 – 4 mSv.

22

Current situation of Iitate village
Before the accident: 1700 families 6200 persons
 April 22, 2011 designated as evacuation area
 2014～2016
Full-scale decontamination by the government

Cost: about 350 billion yen (about 24 billion Euro) 2.3 million of flexible container bags
March 31, 2017 Lifting of evacuation instruction (excluding
one settlement of difficult-to return area) Currently about 10 % of residents returned, mainly oldpeople

Before the accident23Decontamination（2012） Tentative storage(2016)

2.3 Million of FLECON BAGS remain in Iitate village
after lifting evacuation.

Government promised to bring out these bags to the Interim
24
Storage Site within 5 years.....

Forecast of radiation level for 50 years in cases;
1.0 μSv/h on Jan 1, 2019
0.5 μSv/h on Jan 1, 2019

Radiation dose rate, μSv/h

1
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1

Natural radiation level02019

2029

2039

2049

2059
25

Comparison between Chernobyl and Fukushima

Chernobyl: April 1986

Fukushima: March 2011

●Two types of severe accident at NPP:Accident-1: Failure of fission chain reaction→ power surge accident. Chernobyl
Accident-2: Failure of core cooling→ meltdown accident. Fukushima 26

Radioactivity release into the atmosphere- Chernobyl: The reactor and the building were destroyed at a moment of thepower surge. Radionulides similar composition to the reactor core were released.
- Fukushima: The reactor did not explode. Gaseous and volatile radionuclides
were released escaping from melt-down cores.
27

Comparison of contaminated land area andpopulation between Fukushima and Chernobyl
Zone classification by 137Cs contamination level> 555 kBq m-2> 37 kBq m-2
Area,
km2Population,
persons

Area,
km2

Population,persons

Fukushima

8,400

1,590,000

767

82,000Chernobyl

145,000

5,910,000

10,300384,000

Cher/Fuku
ratio

17.2

3.7

13.4

4.7

28

Decommissioning is more difficult for
Fukushima than Chernobyl

Field inspection inside three melt-down reactors is just at thebeginning stage in Fukushima. It is difficult to say how manyyears we need to stabilize the situation.
29Although TEPCO proposed a road-map ofdecommissioning in 40-50 years, it is theiroptimistic desire.

30Private opinion: It is clear misjudge that nuclear power plants
were constructed on Japanese islands of frequent earthquake

Earthquake larger than M4: 1900～2000

31

Total energy supply in Japan
50000040000020000
Nuclear power
OthersNatural gas
Oil
Coal
Hydro power
Wood

15000

Population→
10000

300000200000Population, 10000

Primary energy supply、1010 kcal

600000

5000
100000001950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010 2015

The most important question:- Do we need to produce electricity even by using a techniquepeople living within 30 km should be ready to evacuate?

Thanks for your attention!
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