Effects of Radiation on Human In the Face of Fukushima Daiichi

Nuclear Power Plant Accident

At Sophia University

11 May 2011

Presented by:

Tokyo Institute of Technology

Research Laboratory for Nuclear Reactors

Associate Professor (PI)

Yoshihisa Matsumoto, Ph.D.

Today’s Topic

1. Current Status at Fukushima Daiichi

2. Measure of Radiation and Radioactivity

3. Biological Effects of Radiation

4. Radiation from Fukushima Daiichi

5. Protection from Radiation Exposure

What happed in Fukushima Daiichi?

Unit 1 2 3 4 5 6

Before

Quake

Upon

Quake

Pressure

Vessel

No

Fuel

Fuel

Pool

In Operation Not In Operation

Auto shut-down

Successful

Fission reaction is completely shut down.

No further production of fission products (FP).

However, there is already produced FP,

Which emits “heat” with radiation upon decay.

Therefore,

Continuous cooling of fuel materials is necessary.

Safely ControlledCooling Ongoing

Safely ControlledCooling Ongoing

1. Before earthquake Unit 1-3 were in operation and

Unit 4-6 were not in operation.

2. Upon earthquake (March 11, 14:46PM), Unit 1-3

shut down automatically. Fission reaction

stopped successfully but heat production of ~7%

remained.

3. At 15:41PM, Tsunami attacked and damaged the

emergency power supply.

4. Temperature of reactor core and fuel pool

increased, leading to hydrogen explosion.

5. Radioacitive materials released because of

ventilation and hydrogen explosion between 12-

15 March.

What happed in Fukushima Daiichi?

Safety Control of Nuclear Power Plant

Step 1. Stop: SuccessShut down automatically upon earthquake

Step 2. Cool: FailCooling system destroyed by tsunami

Step 3. Confine: FailRadioactivity released by ventilation and hydrogen

explosion

Road Map to Safe Status

TEPCO Announced on 17 April

Step 1・・・3 monthsEnable continuous cooling with minimal manpower

Step 2・・・3 to 6 monthsAchieve “Cold Shutdown” status

i.e., keep the temperature stably below 100oC.

Decommission・・・10~20 yearsCooled fuel material moved to storage place

Today’s Topic

1. Current Status at Fukushima Daiichi

2. Measure of Radiation and Radioactivity

3. Biological Effects of Radiation

4. Radiation from Fukushima Daiichi

5. Protection from Radiation Exposure

What are “Becquerel” and “Sievert”?

Becquerel

Lightness of the Source

Sievert

Energy Received by Person

What is “Becquerel”?

“Becquerel” is a unit of radioactivityIndicate “how many times radiation is emitted from radioactive substance” per second.=Frequency of radiation emission.[Bq] = [s-1]

Henri Becquerel(1852-1908, France)Nobel Prize for Physics in 1903

Wikipediaより

What is “Gray”?

“Gray” is a unit of absorbed dose

Indicate “how much energy is

absorbed by the unit mass of matter

from radiation” or “how much energy

the radiation gives to the unit mass of

matter”

=Energy per mass

[Gy] = [J/kg]

Named after Louis Harold Gray (1905-1965, UK)

What is “ Sievert ”? (1)

“Sievert ” is a unit of equivalent doseEquivalent dose is the dose of radiation, taking into consideration difference in the magnitude of biological effects among various types of radiation.

Equivalent dose （Sv)= Absorbed dose ( Gy ) × Radiation Weighting Factor

Rolf Maximilian Sievert(1896-1966, Sweden)

Wikipediaより

What is “Radiation Weighting Factor”?

Radiation Factor Equivalent dose of 1Gy

X-ray 1 1Sv

γ-ray 1 1Sv

β-ray 1 1Sv

α-ray 20 20Sv

Neutron 5-20 5-20Sv

What is “Sievert”? (2)

“Sievert” is also a unit of effective dose

Effective dose is the dose of radiation, taking

into consideration that some parts of the

body are more sensitive to radiation than

others.

Effective dose （Sv)

= Σ Equivalent dose (Sv)

× Tissue Weighting Factor

Tissue Factor Tissue Factor

Bone marrow 0.12 Liver 0.04

Colon 0.12 Thyroid 0.04

Lung 0.12 Bone surface 0.01

Stomach 0.12 Brain 0.01

Breast 0.12 Salivary grand 0.01

Gonads 0.08 Skin 0.01

Bladder 0.04 Other tissues 0.12

Esophagus 0.04 Total 1.00

What is “Tissue Weighting Factor”?

What are α-ray, β-ray and γ-ray?

Paper

α-ray

β-ray

γ-ray

Aluminum Lead

Radioactive Nuclides Released

Major

Iodine-131, Cesium-137

Others:

Cesium-134, Strontium-90 and 89

Tellurium-132, Ruthenium-106,

Xenon-133, Krypton-85, etc.

Plutonium detected inside the

plant area only.

Radioactivity decreases by time

“Half Life”

50%

25%

3.1%

Iodine-131Half Life: 8.02 days

8days: 50%

60days: 0.55%

160days: 0.0001%

Others

Cesium-137: 30 years

Cesium-134: 2 years

Strontium-90: 29 years

Radioactivity decreases “half by half” (exponentially)

Today’s Topic

1. Current Status at Fukushima Daiichi

2. Measure of Radiation and Radioactivity

3. Biological Effects of Radiation

4. Radiation from Fukushima Daiichi

5. Protection from Radiation Exposure

Categorization of Radiation Effects

Deterministic effectsEffects other than carcinogenesis and genetic

effects.

Can be seen only after exposure to the radiation

dose above the thereshold.

Stochastic effectsCarcinogenesis and genetic effects.

Thought to occur after exposure to even small dose of radiation, i.e., no threshold is assumed.

The incidence is thought to increase with radiation dose.

Acute, Deterministic Effects

Dose Effects

<250mSv None

500mSv Lymphocyte decrease (transient)

1,500mSv Sickly feeling

(nausea, vomiting, weakness,…)

4,000mSv

(Half lethal

dose)

50% of people die within 1~2 months

Due to hematopoietic failure

without aceptic treatment or bone

marrow transplantation

Deterministic Effects on Various Tissues

Threshold dose of organs and tissue effects

Infertility

Male Transient: 150mSv

Permanent: 3,500~6,000mSv

Female Transient: 650~1,500mSv

Permanent: 2,500~6,000mSv

Fetus

Malformation 100mSv (8d to 8w)

Growth retardation 200mSv (8w to birth)

Mental retardation 500mSv (8w to 25w)

Skin

Hair loss, skin reddening 3,000mSv

Occur only above 100mSv

Stochastic Effects of Radiation

Cancer Risk

-Assumed to increase

at the rate of +0.0005%/mSv

-However, no actual increased risk

observed below 100mSv

-The risk is smaller than other factors,

e.g., cigarette smoking.

Genetic Effects

-Not detected in human.

Solid tumor

Leukemia200 mSv

100 mSv

【RERF 1996】

Carcinogenesis in A -bomb SurvivorsSolid tumorAbove 100mSv:Linear increaseBelow 100mSv:Statistically insignificant

LeukemiaAbove 200mSv:Quadratic increaseBelow 200mSv:Statistically insignificant

放射線影響研究所1996年報告書より

High Radiation Background Area

Is there any rise in cancer risk ? -No!

体質研究会のホームページより

Summary of Radiation Effects

Deterministic effectsOther than carcinogenesis and genetic effects.

→Threshold for any effect larger than 100mSv

Stochastic effectsCarcinogenesis and genetic effects.

→Increased cancer incidence been seen only

above 100mSv.

Genetic effects have not been seen in human

Natural Exposure to Radiation

Total: 1.4mSv/year in Japan

2.4mSv/year in world

World average (per year)

Air Inhalation

１．３ｍSv

Food

Ingestion

0.35mSv

Ground,

Building

0.4mSv

Cosmic

0.35mSv

Major nuclides

Potassium-40

(Food)

Radon-222

(Air)

Radium-226

(Ground)

Ordinary Exposure to Radiation

Medical Exposure:Chest X-ray: 0.05mSv

CT scan: 7mSv

Other Exposure:Flight: 0.2mSv (Tokyo-New York)

Space station: 0.5mSv/day

FAQ about Radiation Effects (1)

Q) Is there a difference in danger

when the source of radiation is

different- Soil, cosmic, human

produced (artificially produced)?

A) No. Radiation effects depends

solely on the quantity of radiation or

radioactivity and the physical

properties of radiation.

Q) Why is radioactivity more dangerous for

children than adults?

A)Radiation affects “cell proliferation”,

which is vigorous in childhood. Additionally,

Iodine tends to accumulate in thyroid. This

organ produces and secretes iodine-

containing hormone, thyroxin, which is

essential for growth and development. As

thyroid is more active in childhood, it

uptakes more iodine and more susceptible

to thyroid cancer than in adulthood.

FAQ about Radiation Effects (2)

Today’s Topic

1. Current Status at Fukushima Daiichi

2. Measure of Radiation and Radioactivity

3. Biological Effects of Radiation

4. Radiation from Fukushima Daiichi

5. Protection from Radiation Exposure

Rome(0.25μSv/hour）

Tokyo usual(0.028-0.079μSv/hour）

France average（0.09μSv/hour）

Increased Spacial Radiation Dose in Tokyo

Dose at Shinjuku

Radiation exposure is reflected by the “surface” rather than the height!

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

Radiation dose (μSv/hr) at Shinjuku

Rain

Release

学内の研究者(中村隆司教授)がまとめたもの。

FAQ about Air-carried Radioactivity (1)

Q) What are the dangers of the wind carrying

radioactivity to Tokyo?

A) Presently need not worry.

<Time sequence>

1. Radioactivity released between March 12-15. No

gross release of radioactivity thereafter.

↓2. Radioactivity carried by wind and detected in

Tokyo from March 15. [Radioactivity in Air]

↓3. Radioactivity fell to ground with rain around

March 20. [Radioactivity on Ground]

Q) Is airborne radioactivity more

dangerous when it rains?

A) Presently need not worry. Rain falls

with tiny particles, which may contain

radioactivity. However, now most of

the radioactivity has fell to the

ground. It is sufficient to have an

umbrella or to wear coat to avoid

get wet.

FAQ about Air-carried Radioactivity (2)

What is “Provisional Regulation Level”?

Foods with radioactivity below this level is allowed to

be shipped to market.

Foods with radioactivity above this level is banned

to be shipped to market

Expressed as Bq/kg

↓ How is it determined?

Assume to start eating food with this radioactivity

and to continue eating for one year

And

Keep the effective dose below 5mSv

(for Iodine, equivalent dose at thyroid below 50mSv)

Thus it is a conservative, safety standard.

Cesium, Uranium

Effective

Dose

5mSv

Water

1mSv

Milk

1mSv

Vegetables

1mSv

Grain

1mSv

Meat, Fish,

Egg

1mSv

Iodine

Thyroid

Eq. Dose

50mSv

Water

11.1mSv

Milk

11.1mSv

Vegetables

11.1mSv

Others

16.7mSv

Determine “Provisional Regulation Level”

Radioactivity calculated according to food consumption data

What is the Risk of Contaminated Food (1)?

Spinach: Iodine-131 54,100Bq/kg

(March 18, Hitachi, Ibaraki)

What is the risk of this food?

- Consumption of spinach: 6.6kg/year

- Effective dose per year: 7.9mSv <<100mSv

Even if this radioactivity continues for one

year. However, actually, Iodine-131 is

decreasing rapidly and will never reach this

value.

Provisional regulation level considers that we

take many sorts of vegetables.

What is the Risk of Contaminated Food (2)?

Fish (Kounago): Cesium 14,400/kg

(April 18, Ibaraki)

What is the risk of this food?

- Effective dose per 1kg: 0.234mSv<<100mSv

-For 100mSv, 426kg!

What is the risk for long term?

- Above estimation takes it into consideration.

Although Cesium-137 has the half life of 30

years, it is excreted from our body by the half

life of ~100days.

What is the Risk of Contaminated Water? (1)

Water contamination detected at Kanamachi

water purifying facility on March 22-23.

Iodine-131: 210Bq/kg

Provisional reference level for infants: 100Bq/kg

Metropolitan Government advised “to refrain from

feeding infants as possible”

What is the risk for infants?

- Water drinking of infants: 0.7kg/day

- Thyroid effective dose: 0.54mSv

- Risk is negligible. Dehydration will be more risky.

１ yearTime→

０

↑R

ad

ioa

ctiv

ity (B

q/k

g)

Effective dose is represented by

“surface” rather than height

What is the Risk of Contaminated Water? (2)

What to do in case it happens again?

-Continue watch

-Continue drinking avoid dehydrationExceed

“Surface” becomes

Equal to that given by

Provisional regulation level

Today’s Topic

1. Current Status at Fukushima Daiichi

2. Measure of Radiation and Radioactivity

3. Biological Effects of Radiation

4. Radiation from Fukushima Daiichi

5. Protection from Radiation Exposure

Protection from Radiation Exposure

External Exposure Internal Exposure

Protection is different for External and Internal Exposureやさしい放射線とアイソトープ　４版　社団法人日本アイソトープ協会

Protection from “External” Exposure

1. Shorten Time

2. Keep Long Distance

3. Place Shield between Source and Body

やさしい放射線とアイソトープ　４版　社団法人日本アイソトープ協会

Protection from “Internal” Exposure

1. Reduce Inhalation

- Wear Mask

2. Reduce Ingestion

- Wash food

3. Reduce intake through skin

- Wear gloves

- Avoid exposure of skin

- Put bandage on wound

4. Others

- Wear coats outdoors and take it off at home

- Wash hands and gargle

Special caution is not

necessary in Tokyo area!

But protection from virus

and pollen will protect you

further from radiation!

Thank you very much

for kind attention