May 25, 2011
TOKYO (Kyodo) — Radiation released by the crippled Fukushima Daiichi nuclear power plant has caused soil contamination matching the levels seen in the Chernobyl disaster in some areas, a researcher told the government’s nuclear policy-setting body Tuesday.
“A massive soil decontamination project will be indispensable before residents in those areas can return,” said Tomio Kawata, a research fellow of the Nuclear Waste Management Organization of Japan, at the meeting of the Japan Atomic Energy Commission, which sets policies and strategies for the government’s nuclear power development.
According to Kawata, soil in a 600 square kilometer area mostly to the northwest of the Fukushima plant is likely to have absorbed radioactive cesium of over 1.48 million becquerels per square meter, the yardstick for compulsory migration orders in the 1986 Chernobyl catastrophe.
Kawata also said soil in a 700 square km area is likely to have absorbed 555,000-1.48 million becquerels per square meter, which was a criteria for temporary migration during the Chernobyl disaster.
Kawata estimated the soil contamination using data on radiation levels in the air monitored by the Ministry of Education, Culture, Sports, Science and Technology.
The size of the contaminated areas in the Fukushima crisis is one-tenth to one-fifth of those polluted in the Chernobyl disaster, Kawata said.
While the expected radiation exposure from 1.48 million becquerels of cesium is around five millisieverts a year, below the government’s benchmark of 20 millisieverts for evacuation orders, decontamination will still be necessary before evacuees can return as radioactive cesium binds strongly to soil, making it hard to reduce radiation levels, Kawata said.