NRA corrects own projections

October 30, 2012

Errors found in projections for spread of radiation in severe accidents

http://mainichi.jp/english/english/newsselect/news/20121030p2g00m0dm012000c.html

TOKYO (Kyodo) -- Japan's nuclear regulatory authority apologized Monday after finding errors in its recently announced projections for the spread of radiation from reactors nationwide in the event of severe accidents.

The Nuclear Regulation Authority corrected the projections to show that the city of Nagaoka, rather than Uonuma, both in Niigata Prefecture, would be the most distant point from Tokyo Electric Power Co.'s Kashiwazaki-Kariwa plant where the amount of radiation released a week after an accident could reach 100 millisieverts, the level where evacuation is recommended.

The authority initially said the amount of radiation could reach that level in locations around 40 kilometers from the plant, reaching Uonuma, about 40.2 km away from the plant.

The NRA also revised the projections for Japan Atomic Power Co.'s Tokai Daini plant in Ibaraki Prefecture and Tsuruga plant in Fukui Prefecture, Hokuriku Electric Power Co's Shika plant in Ishikawa Prefecture, Kyushu Electric Power Co.'s Genkai plant in Saga Prefecture and Sendai plant in Kagoshima Prefecture.

An official of the NRA secretariat said many of the mistakes had occurred during the conversion of weather data received from each utility for use in a computer program.

The NRA detected the mistakes after being notified by Hokuriku Electric, the official said.

The regulatory body announced radiation projections for 16 atomic plants on Wednesday to provide references for local governments to expand areas that should be subject to special preparations against nuclear disasters following the meltdowns at Tokyo Electric's Fukushima Daiichi complex last year.

The simulation showed the distances at which doses could reach 100 millisieverts a week after severe accidents at the plants like the one at the Fukushima Daiichi complex last year.

The International Atomic Energy Agency calls for evacuation when effective doses exceed 100 millisieverts in the first seven days of an emergency exposure situation.