Risks and benefits of evacuation in TEPCO's Fukushima Daiichi nuclear power station accident

摘要

One month after the TEPCO accident, the number of the disaster-related deaths in Fukushima Prefecture exceeded that in Miyagi and Iwate which were not affected by the radiation, due to increase in disuse syndrome during the prolonged evacuation by the accident. About 90% of the deaths were the elderly. The risk and benefit of the evacuation of 11 municipalities in Fukushima are analyzed using data published by the Japanese government. The total loss of life expectancy (LLE) of the disaster-related deaths is 5,100,000 person-days. The LLE avoided by the evacuation is estimated from the cumulative doses of 172 locations. The average cumulative dose avoided is 205 mSv in 10 years. Total LLE avoided for 100,000 evacuees is 1,850,000 person-days. It is 2.8 times less than that accompanies evacuation. The delay in lifting the evacuation orders caused many disaster-related deaths among the elderly. The long-term evacuation of the TEPCO accident followed the dose rate recommended by ICRP, but is not justified. Discussions are provided for future improvements: (1) Lifetime fatal cancer probability from radiation exposure in the elderly is one-fifth of the average. Current guidelines do not take that into account. The difference needs to be incorporated into the nuclear emergency guidelines. (2) Radiation protection measures cannot describe other health risks, but the present guides are developed from the perspective of radiation protection. (3) Need to revise emergency guides to consider other health risks such as disuse syndrome of Fukushima, unnecessary abortions of Chernobyl and mental and psychological problems. (4) Risk communication with the general public does not work in a nuclear accident. (5) Exempt the ALARA principle from the public in low-dose area in the event of a nuclear accident. (6) Allow evacuees to participate in decontamination and restoration work. The lesson is important for countries where nuclear power plants are located in agricultural areas and are aging.