Overview of Events at Fukushima Dai-ichi Nuclear Power Plant 23 March 2011 Luis Echávarri Javier Reig John Nakoski Ted Lazo 2011 Organisation for Economic Co-operation and Development 1
Outline of Presentation 1. Introduction and Role of NEA 2. Site and INES Information 3. Plant Design and Accident Description 4. Radiological Protection and Emergency Response 2011 Organisation for Economic Co-operation and Development 2
Fukushima Dai-ichi Nuclear Power Plant Unit 5 Unit 6 Unit 2 Unit 1 Unit 4 Unit 3 Source: http://www.tepco.co.jp/en/news/gallery/nuclear-e.html 2011 Organisation for Economic Co-operation and Development 3
Fukushima Dai-ichi Nuclear Power Plant 2011 Organisation for Economic Co-operation and Development 4
International Nuclear and Radiological Event Scale Chernobyl, 1986 Three Mile Island, USA, 1979 2011 Organisation for Economic Co-operation and Development 5
Basic Design Information (BWR3 & BWR4) 2011 Organisation for Economic Co-operation and Development 6
Percent of full power NUCLEAR ENERGY AGENCY Decay Heat Generation After Shutdown decay heat at Fukushima Daiichi units 1, 2, and 3 is less than 0.5% of full power 2011 Organisation for Economic Co-operation and Development 7
BWR3 & BWR4 Containment Configuration Typical for Fukushima Dai-ichi Units 1, 2, 3, & 4 Spent fuel pool Fukushima Daiichi: Location of Explosions in Units 1 and 3, location of fires in Unit 4. The explosion in Unit 2 occurred somewhere in the reactor building near the suppression chamber. 2011 Organisation for Economic Co-operation and Development 8
Status of Fukushima Dai-ichi as of 23 March 2011 Organisation for Economic Co-operation and Development 9
Fukushima Dai-ichi Nuclear Power Plant 2011 Organisation for Economic Co-operation and Development 10
Radiation Risks at Low Doses (<100 msv) Cancer and leukemia can be caused by exposures that result in misrepair of cells. Such effects generally do not appear for 10 or more years after exposure. The risk of such effects, called stochastic effects, is proportional to the dose incurred, with an overall risk of 5% per Sievert of exposure. Stochastic effects are generally only statistically visible when individual exposures to a large population exceed about 100 msv. 2011 Organisation for Economic Co-operation and Development 11
Radiation Risks at High Doses (> 1 Gy) Sufficiently massive cell killing will cause the entire tissues to fail or die (Deterministic effects). Threshold: about 1 to 2 Gy of exposure. At doses of 5 to 10 Gy whole body, rapid death is very likely even with extensive medical treatment. The severity of the effect will be proportional to the dose above the threshold 2011 Organisation for Economic Co-operation and Development 12
International Worker Dose Limit Recommendations Workers are normally allowed to receive 100 msv over a 5-year period, with a maximum of 50 msv in any single year. In emergency situations, workers are allowed to receive up to 500 msv as a result of emergency work to: Save Lives Prevent Deterministic Health Effects Avert Large Collective Doses 2011 Organisation for Economic Co-operation and Development 13
Japanese Worker Dose Limits Japanese regulations follow international recommendations for the control of normal worker doses The current Japanese regulations allow worker s emergency exposures to reach 100 msv, however, METI and the Ministry of Health, Labor and Welfare have declared, on 15 March, that emergency workers were for this situation allowed up to 250 msv. 2011 Organisation for Economic Co-operation and Development 14
Radiation release chronology Fukushima Dai-ichi 2011 Organisation for Economic Co-operation and Development 15
Dose Rates in Prefectures Near Fukushima plant as of 23 March at 8:00 Prefecture/ Map reference Dose Rate 23 March At 8:00-9:00 (µsv/h) Normal Natural Radiation Dose Rate (µsv/h) Surface Contamination (kbq/m 2 ) I-131 Cs-137 Yamagata (6) 0.086 0.025-0.082 0.59 0.14 Ibaraki (8) 0.322 0.036 0.056 85 12 Tochigi (9) 0.145 0.030 0.067 25 0.44 Gunma (10) 0.102 0.017 0.045 1.5 0.072 Saitama (11) 0.123 0.031 0.060 22 1.6 Chiba (12) 0.097 0.022 0.044 0.71 0.15 Tokyo (13) 0.1465 0.028 0.079 32 5.3 Kanagawa (14) 0.099 0.035 0.069 0.34 0.11 Niigata (15) 0.046 0.031 0.153 NA NA 2011 Organisation for Economic Co-operation and Development 16
Public Health Risks Radiation Risks are assumed to exist as a result of ANY exposure, no matter how small. Exposure to natural radiation is, on average, 2.4 msv per year. At the current dose rates offsite, approximately one year of exposure would be needed to reach 1 msv. It is not possible to see statistical evidence of public health risk at exposures of less than 100 msv. 2011 Organisation for Economic Co-operation and Development 17
Evacuation Status Evacuation zones around Fukushima Dai-ichi and Fukushima Dai-ini, are 20 km and 10 km respectively, with overlap. Approximately 185 000 people living in the these zones have been evacuated. Slightly Contaminated Individuals 23 of 133 monitored individuals leaving the area showed some level of contamination. These individuals were decontaminated (using soap and water) and sent to the evacuation center. 2011 Organisation for Economic Co-operation and Development 18
Sheltering Status A sheltering zone was established on 15 March for Fukushima Dai-ichi between 20 km and 30 km from the plant. Sheltering continues. 230,000 units of stable iodine distributed to evacuation centres. The iodine not yet administered it should be taken within about 1 hour of exposure for maximum effectiveness Distribution is a precautionary measure Stable Iodine (KI) Status 2011 Organisation for Economic Co-operation and Development 19