Effects of Radiation on Human In the Face of Fukushima Daiichi Nuclear Power Plant Accident

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1 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.

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

3 What happed in Fukushima Daiichi? Unit Before Quake Upon Quake Pressure Vessel Fuel Pool In Operation Auto shut-down Successful No Fuel Not In Operation 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. Cooling Ongoing Cooling Ongoing Safely Controlled Safely Controlled

4 What happed in Fukushima Daiichi? 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 March.

5 Safety Control of Nuclear Power Plant Step 1. Stop: Success Shut down automatically upon earthquake Step 2. Cool: Fail Cooling system destroyed by tsunami Step 3. Confine: Fail Radioactivity released by ventilation and hydrogen explosion

6 Road Map to Safe Status TEPCO Announced on 17 April Step 1 3 months Enable continuous cooling with minimal manpower Step 2 3 to 6 months Achieve Cold Shutdown status i.e., keep the temperature stably below 100 o C. Decommission 10~20 years Cooled fuel material moved to storage place

7 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

8 What are Becquerel and Sievert? Becquerel Lightness of the Source Sievert Energy Received by Person

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10 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 ( , UK)

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12 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 Sv

13 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

14 What is 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

15 What are α-ray, β-ray and γ-ray? Paper Aluminum Lead α-ray β-ray γ-ray

16 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.

17 Radioactivity decreases by time Radioactivity decreases half by half (exponentially) 50% Iodine-131 Half Life: 8.02 days 8days: 50% 60days: 0.55% 160days: % Half Life 25% 3.1% Others Cesium-137: 30 years Cesium-134: 2 years Strontium-90: 29 years

18 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

19 Categorization of Radiation Effects Deterministic effects Effects other than carcinogenesis and genetic effects. Can be seen only after exposure to the radiation dose above the thereshold. Stochastic effects Carcinogenesis 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.

20 Acute, Deterministic Effects Dose <250mSv 500mSv 1,500mSv 4,000mSv (Half lethal dose) Effects None Lymphocyte decrease (transient) Sickly feeling (nausea, vomiting, weakness, ) 50% of people die within 1~2 months Due to hematopoietic failure without aceptic treatment or bone marrow transplantation

21 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

22 Stochastic Effects of Radiation Cancer Risk -Assumed to increase at the rate of %/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.

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25 Summary of Radiation Effects Deterministic effects Other than carcinogenesis and genetic effects. Threshold for any effect larger than 100mSv Stochastic effects Carcinogenesis and genetic effects. Increased cancer incidence been seen only above 100mSv. Genetic effects have not been seen in human

26 Natural Exposure to Radiation Total: 1.4mSv/year in Japan 2.4mSv/year in world World average (per year) Ground, Building 0.4mSv Cosmic 0.35mSv Food Ingestion 0.35mSv Air Inhalation 1.3mSv Major nuclides Potassium-40 (Food) Radon-222 (Air) Radium-226 (Ground)

27 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

28 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.

29 FAQ about Radiation Effects (2) 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 iodinecontaining 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.

30 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

31 Radiation dose ( /hr) at Shinjuku

32 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 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]

33 FAQ about Air-carried Radioactivity (2) 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.

34 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.

35 Determine Provisional Regulation Level Iodine Cesium, Uranium Others 16.7mSv Thyroid Eq. Dose 50mSv Vegetables 11.1mSv Water 11.1mSv Milk 11.1mSv Grain 1mSv Meat, Fish, Egg 1mSv Effective Dose 5mSv Vegetables 1mSv Water 1mSv Milk 1mSv Radioactivity calculated according to food consumption data

36 What is the Risk of Contaminated Food (1)? Spinach: Iodine ,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.

37 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.

38 What is the Risk of Contaminated Water? (1) Water contamination detected at Kanamachi water purifying facility on March 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.

39 What is the Risk of Contaminated Water? (2) Radioactivity (Bq/kg) Exceed What to do in case it happens again? -Continue watch -Continue drinking avoid dehydration Surface becomes Equal to that given by Provisional regulation level 0 Time Effective dose is represented by surface rather than height 1 year

40 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

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43 Protection from Internal Exposure 1. Reduce Inhalation - Wear Mask 2. Reduce Ingestion - Wash food Special caution is not necessary in Tokyo area! But protection from virus and pollen will protect you further from radiation! 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

44 Thank you very much for kind attention