Kazuo Sakai National Institute of Radiological Sciences Research Center for Radiation Protection

Transcription

1 Fukushima Experience Kazuo Sakai National Institute of Radiological Sciences Research Center for Radiation Protection

2 Fukushima Experience 1. Earthquake, Tsunami, and the NPP Accident 2. Radioactivity Released 3. Exposure to Workers 4. Exposure to the Public 5. Emotional Impact 6. Emergency to Recovery

3 Fukushima Experience 1. Earthquake, Tsunami, and the NPP Accident 2. Radioactivity Released 3. Exposure to Workers 4. Exposure to the Public 5. Emotional Impact 6. Emergency to Recovery

4 Earthquake Fukushima Dai-ichi NPP (1F) Epicenter Source: pc o.co.jp Fukushima Dai-ni NPP (2F) 14:46 March 11, 2011 Magnitude: 9.0 Mw Huge tsunami of 15 m height attacked Fukushima NPPs. Source: pc o.co.jp

5 Fukushima Dai-ichi NPP Source: 5

6 Tsunami Casualties : 18, 550 Death Missing 15, 882 2,668 (As of March 11 th, 2013) KYODO NEWS KYODO NEWS NOAA/US Dept of Commerce,

7 Earthquake Sequence of the Accident Reactors Loss of Offsite Power Emergency Backup Power Generators Automatic Shutdown Cooling Continued

8 Earthquake Sequence of the Accident Reactors Loss of Offsite Power Emergency Backup Power Generators Automatic Shutdown Cooling Continued Tsunami

9 Earthquake Sequence of the Accident Reactors Loss of Offsite Power Emergency Backup Power Generators Automatic Shutdown Cooling Continued Tsunami Loss of Power Supply Lack of Cooling Capacity Unusual increase in vessel pressure Hydrogen Explosion Vent to reduce the pressure Release of Radioactive Nuclides

10 Accident progression at Unit1 Hydrogen explosion in the operation floor Plaster board Accumulation of Hydrogen Explosion Reinforced Concrete Reactor building Reactor building 10

11 Accident Progression at Unit2-4 Unit 3 Unit 4 Unit 2 11

12 Fukushima Experience 1. Earthquake, Tsunami, and the NPP Accident 2. Radioactivity Released 3. Exposure to Workers 4. Exposure to the Public 5. Emotional Impact 6. Emergency to Recovery

13 Release of radioactivity < 1.0 No Data 1F NPP MEXT and DOE assessed the ambient dose rate on 1m from the ground surface inside the zone of 80 km of 1F was carried out with a aerial monitoring system. The map was prepared based on results obtained from April 6 th to 29 th by a small airplane and two helicopters, in total 42 flights. Decay of radioactive substances was considered and actual readings were converted into values as of the last survey date of April 29 th. 20km 30km 60km 80km Results of ambient dose rate inside the zone of 80km of 1F Source: MEXT

14 Release of radioactive nuclides (INES Rating) Assumed amount of the discharge from Fukushima Dai-ichi (1F) NISA s estimation *1 NSC s estimation *2 (Reference) Amount of the discharged from the Chernobyl accident 131 I (a) 1.3x10 17 Bq 1.5x10 17 Bq 1.8x10 18 Bq 137 Cs 6.1x10 15 Bq 1.2x10 16 Bq 8.5x10 16 Bq (Converted value to 131 I) *3 (b) 2.4x10 17 Bq 4.8x10 17 Bq 3.4x10 18 Bq (a)+(b) 3.7x10 17 Bq 6.3x10 17 Bq 5.2x10 18 Bq (notes) *1: Estimation by NISA is based on the numerical analysis of accident transient *2: NSC calculated backward of monitoring data to estimate the amount of discharge *3: multiplication factor of radiological equivalence to 131 I is 40 The scale of the accident was rated Level 7.

15 Fukushima Experience 1. Earthquake, Tsunami, and the NPP Accident 2. Radioactivity Released 3. Exposure to Workers 4. Exposure to the Public 5. Emotional Impact 6. Emergency to Recovery

16 Total Dose Distribution among Plant Workers msv March April May > < Total Max (msv) Av.(mSv)

17 Internal Exposure and External Exposure In Highly Exposed Plant Workers Case Total (msv) External (msv) Internal (msv) A (13%) B (16%) 590 (87%) 540 (84%) 17

18 Acute effects were not observed in workers directly involved in the accident.

19 TEPCO Fukushima Daiichi Nuclear Power Plant A database is constructed for the long term health management. Personal Data ID Dose Tasks involved Health check-up results Database Health Consultation etc. 19

20 Fukushima Experience 1. Earthquake, Tsunami, and the NPP Accident 2. Radioactivity Released 3. Exposure to Workers 4. Exposure to the Public 5. Emotional Impact 6. Emergency to Recovery

21 External Dose Assessment of Residents Based on questionnaires for residents about behavior in Fukushima prefecture after the earthquake Time sequential maps of radiation dose rate near 1F with intervals of 1hour for initial phase and 1day for the remained period. March 12 11:00 a.m. Completing evacuation March 12 10:00 a.m. Starting evacuation Calculation of doses in residents during the period of 12 March 11 July, 2011

22 External exposure estimation among 411,922 evacuees (except radiation workers) ~ 1mSv 66.0 % ~ 2mSv 94.9 % ~ 5mSv 99.8 % Max. 25 msv msv

23 Measurement of Radioactivity in Thyroid in Children. The survey was conducted from March 26 to 30 in Iwaki City, Kawamata town, and Iitate village, where the high probability of internal radiation exposure at the thyroid gland was suspected. 1,080 children aged zero to 15 were measured. 23

24 Dose Rate Distribution in the Thyroid of Fukushima Children For 99% of the children tested, the dose rate was 0.04 μsv/h or less. the highest dose was 0.1 μsv/h (Equivalent dose of 50 msv/y at thyroid gland for 1 year old). The radiation level was not the level that required more detailed examination. 24 (From NSC website)

25 Radioactivity in daily food in Fukushima Bq/kg Measurement of extra dishes of Fukushima households I-131 Cs-134 Cs-137 K-40 Detection limit (1Bq/kg)

26 Dose Received through Food (June 2012) Annual Internal Exposure (msv) (Maximum Value) Radioactive Cesium Naturally Occurring Radioactivity Based on Monitoring of Daily Food in Fukushima

27 100 msv (Gy)

28 Harmful Tissue Reaction Significant Increase in Cancer Risk

29 Harmful Tissue Reaction Significant Increase in Cancer Risk Dose to Fukushima Residents

30 The levels of exposure estimated for the general public are not the level where serious health effects are suspected. 3/12 11:00 3/12 10:00 避難開始

31 Fukushima Experience 1. Earthquake, Tsunami, and the NPP Accident 2. Radioactivity Released 3. Exposure to Workers 4. Exposure to the Public 5. Emotional Impact 6. Emergency to Recovery

32 Public Concern General public who had not been aware of radiation and its effects, has been emotionally affected and confused by some exaggerated stories on radiation effects provided by various information sources, including the media and radiation experts. 32

33 Catchy Phrases on Cover of Popular Magazines Radioactivity is coming to you! Internal Contamination Induces Brain Damage - from Chernobyl Experience 20 years later Malformation, Strange Diseases, Mental Retardation in Fukushima 33

34 Trend of telephone consultation (Number of calls) Detection of 131 I from tap water in Tokyo

35 Lack of Precise Information on Radiation Effects Radiation and Pregnancy I was told to terminate my pregnancy. Lack of knowledge is responsible for great anxiety and probably unnecessary termination of pregnancies. Termination of pregnancy at fetal doses of less than 100 mgy is NOT justified based upon radiation risk. (ICRP Publication 84) 35

36 Perception of Radiation among General Public Direct connection between Radiation and Severe Effects, Cancer, Death Radiation Severe Effects

37 Shift of Thinking: Need for the Concept of Dose-Effect Relationship Radiation Severe Effects How Much? No effects

38 Messages to Share We should NOT discount Biological Effects of Ionizing Radiation when a Dose Is High We should NOT be too much concerned about the Biological Effects of Ionizing Radiation when a Dose is Low

39 Fukushima Experience 1. Earthquake, Tsunami, and the NPP Accident 2. Radioactivity Released 3. Exposure to Workers 4. Exposure to the Public 5. Emotional Impact 6. Emergency to Recovery

40 30 km 20 km Zoning as of April 2012 Brown and Red (25,000 residents) Areas difficult to return. Higher than 50mSv/a Yellow Continued off limit area Shift to the above category after decontamination msv/a Green and Blue within 20 km radius. To prepare lifting evacuation order <20 msv/a 40

41 Zoning as of May 2012 Areas difficult to return. Higher than 50mSv/a Continued off limit area msv/a To prepare lifting evacuation order <20 msv/a To be determined

42 Emergency Phase to Recovery Phase - More and more issues, one after another- Decontamination Radioactive waste Radioactivity control in food Returning home 42

43 Thank you for your kind attention.