April 12, 2011

The Lesson learned from the Chernobyl Accident
and the Data from Atomic Bomb Survivors― For Understanding the Fukushima Daiichi Accident and the Robustness of theHuman Body to Ionizing Radiation ―Prof. Ken-ichiro SUGIYAMA
Graduate School of Engineering
Hokkaido University

1. The Accident of Chernobyl Unit 4 of 1,000 MWe
Graphite-Moderated Boiling Water Pressure Tube Reactor
in 1986
1. The worst nuclear power excursion ( supercriticality ) ,which led a large-scale reactor (pressure tubes) explosion,
was caused.
2. A hydrogen explosion was involved due to water reaction
with overheated fuel-rod claddings (zirconium metalcladdings).
3. The large amount of energy release caused the ignition ofa large amount of graphite moderators, resulting in alarge-scale fire.

The Chernobyl accident as a type of uncontrolled nuclear power
excursion was caused by many violations of no educated and notrained operators in the former Soviet Union. All radioactive fission
products and core materials were exposed to the atmosphere andcaused the fire. The fission products were carried not only to a large
area in the former Soviet Union but also to northern European countries
and to Scandinavian countries by prevailing wind.
The Chernobyl reactor wascompletely exposed to theatmosphere shortly after theaccident.

100% of Krypton andXenon,~50% of Iodine,~30% of Cesium, and3~4% of the fuel wasreleased into theatmosphere .

The Distribution of Cesium 137
All inhabitantsin an arealarger than
555kBq/m²
were told toevacuate.

Minsk ~330km

Gomel ~130km

Chernobyl

1480~3700kBq/m 2
185~555kBq/m2

555~1480kBq/m2
37~185kBq/m2

Kiyef ~110kmEffects of Radiation from the Chernobyl Disaster
1. When the accident happened, two workers died immediately, one
from the explosion, and one by a coronary heart attack.
2. 134 workers received acute doses ranging from 0.8 to 16 Grays andsuffered radiation sickness, resulting in emergency hospitalization.
3. Of the 134, 27 workers received 4.2 to 16 Grays of and 1 worker
exposed to 2.2 to 4.1 Grays died in the next few months. The 106
workers including 90 workers receiving less than 4.1 Graysrecovered.
4. There had been about 1,800 cases of thyroid cancer in children
according to UNSCEAR 2000 report. Thyroid cancer can be treatedsurgically.
5. There is no scientific evidence of increases in overall cancer
incidence or mortality or non-malignant disorders to radiation
exposure 14 years after such an accident.
6. Owing to its short latency time, the risk of leukemia, which was amajor concern did not appear even among the 106 recoveryworkers.

Fukushima Daiichi
Power Station
Hydrogen Explosionin Units 1 to 4
Water-Zirconium
Reaction andFuel Bundle Melt

Degraded Reactors
Small or Medium ScaleHydrogen Explosion inUnits 1 to 3

DegradedContainments

Hydrogen Explosionin Unit 2

2. Data from the Atomic Bomb Survivors:
Instantaneous Exposure to High Radiation Doses
1. The bombs dropped on Hiroshima and Nagasaki took ahorrendous death toll of 200,000.
2. 86,572 survivors have been monitored. About half ofthem were within 2.5km from the epicenter of the atomic
bomb blasts, and about 8,500, or 10% suffered radiation
doses from 1 to 6 Sieverts.
3. Up to the end of 1997, it is estimated that only 450
cancer deaths occurred as a result of radiation exposure
from the bombs.
4. The projection for when all survivors have died is thatabout 800, or 0.9% will have died as a result of cancerfrom radiation of the bombs.

The life-span data of survivors clearly show a robustness ofhuman body. The joint Japanese/US study shows nosignificant differences among groups from 0 to 0.8 Gray at
the median age of life span. No genetic effects were causedby radiation in the children born to the survivors.

Data of 120,000 Radiation Workers in the UK :Long-Term Exposure to Low Radiation Dosage
There is no significant additional risk from radiation received.

DNA Repair Mechanism to Low Radiation Doses
DNA damage occurs naturally from a variety of processes other thanradiation. The repair mechanism repairs 99.99 percent of singlestranded breaks and 90 percent of double-strand breaks. Severe DNA
damage and error-prone
repair disappear
through apoptosis.
The accumulation of
mutated cells with aging
gradually impairs DNA
Recent finding
repair processes andleads to the increased
Recent finding
probability of cancerwith age.
With aging

Recent finding3. Recommendation on Ionizing Radiation
Effects to Human Body
from International Organizations
5 00 m Sv : Safe limits of workers in emergency recommended by theInternational Commission on Radiological Protection (ICRP)
250 m Sv : Present safe limits of workers in emergency at Japan
100 m Sv : Safe limits on indoor stay of general public living near
nuclear plants in emergency recommended by theInternational Commission on Radiological Protection (ICRP)
50 m Sv : Safe limits for foods as established by the International
Atomic Energy Agency (IAEA) and the World HealthOrganization (WHO)20 m Sv : The current safe limit for indoors of general public livingin the nuclear power plant zone.
5 m Sv : Present safety limit on foods in Japan

Safety Limits on Foods
between IAEA and Japan for Adults

Radioactive
IodineRadioactive
Cesium

Japan

IAEA

milk

300Bq/kg

3,000Bq/kg

vegetables

2,000Bq/kg

3,000Bq/kg

Meat, fish, dairy products

2,000Bq/kg

30,000Bq/kg

milk

200Bq/kg

3,000Bq/kg

vegetables

500Bq/kg

3,000Bq/kg

meat, fish, egg

500Bq/kg

30,000Bq/kg(meat and dairyproducts)

4. Onagawa BWR Power Station Unit No.1 to No.3OnagawaFukushima

The Nearest Nuclear Facility to the Earthquake Center
The Earthquake and Tsunami presented no problem because it issituated 15 meters above sea level.

5. The Lesson Learned from the Tsunami Causedby M9 Earthquake
1. Provided power station has a good base rock layer and ahigh location, catastrophic damage from these kinds ofnatural disasters will be dramatically decreased.
2. A passive air-cooling system not using electric power isrequired for preventing fuel rod damage.
3. An Ignition system should be standard to preventhydrogen explosions in fuel rod-damaged reactors.
4. A passive filtered-venting system that doesn’t use electric
power should be standard to release volatile fission
products from severely core-damaged reactors.

The white dots show the centers of 42,000 earthquakes
occurred between 1961 and 1969 from C.Kissinger

The Relation between Energy and Magnitude
The energy E in ergs is related to the magnitude M
by the following empirical formula :log10 E = 11.4 + 1.5M .

The energy E increases logarithmically with M :EM +1= 101.5 = 31.6
EM

What scale of Earthquake
Occurredin Fukushima and Onagawa
Nuclear Power Stations

Definition of Becquerel, Gray and Sievert
Becquerel ( symbol : Bq )One Bq is defined as the activity of a quantity of radioactive
material in which one nucleus decays per second.
The unit of Bq is [s-1].
Gray ( symbol : Gy )The Ggray is the SI unit of absorbed radiation dose of ionizing
radiation (for example, X-rays), and is defined as the absorption of
one joule of ionizing radiation by one kilogram of matter (usuallyhuman tissue).
The unit of Gy is [ J/kg ].
Sievert ( Sv )The Sievert (symbol : Sv ) is the SI derived unit of dose equivalentradiation. It attempts to quantitatively evaluate the biologicaleffects of ionizing radiation as opposed to the physical aspects,
which are characterized by the absorbed dose, measured in gray.
The unit of Sv is [ J/kg ].

Conversion from Gray to Sievert• α-rayＺ [Sv］ = 20 × Ｙ [Gy］
• β-ray, γ-ray, X-ray
Y ［Sv］ = 1 × Y ［Gy］
• Neutron
Z ［Sv］ = ( 5 ~ 20 ) × Y ［Gy］

Recommendation and Estimation on Ionizing
Radiation Effects to Human Body from International
Organizations(cont’d)
50 m Sv : Safe limits for foods as established by the International
Atomic Energy Agency (IAEA) and the World HealthOrganization (WHO)20 m Sv : The current safe limit for indoors of general public livingin the nuclear power plant zone.
5 m Sv : Present safety limit on foods in Japan2.4m Sv : Average worldwide annual radiation dose from cosmic
rays, soil and produce, with a typical range in different partsof the world from 1 mSv to 10 mSv

3. Recommendation and Estimation
on Ionizing Radiation Effects to Human Body
from International Organizations~10,000 m Sv : 100% mortality estimated from Japanese atom bomb
survivors by the UN Scientific Committee on the Effects ofAtomic Radiation (UNSCEAR estimates 11 excess deaths per
100person Sv at high and medium doses)
5 00 m Sv : Safe limits of workers in emergency recommended by
the International Commission on Radiological Protection(ICRP)
250 m Sv : Present safe limits of workers in emergency at Japan
100 m Sv : Safe limits on indoor stay of general public living near
nuclear plants in emergency recommended by theInternational Commission on Radiological Protection (ICRP)