The Nuclear Regulation Authority said Thursday a thorough review of its mistake-plagued projections for the spread of radiation turned up errors in the data for every atomic power plant in Japan.
The regulatory body examined the data in detail to ensure there would be no more mistakes in the projections. Local governments are expected to use the information to craft plans to prepare for nuclear disasters.
The NRA said there were significant changes in diagrams for how radiation could spread in the event of crises at Kyushu Electric Power Co.’s Genkai and Sendai power plants and Hokkaido Electric Power Co.’s Tomari nuclear complex, compared with the previously revised projections released Oct. 29.
The three projections had to be revised either because the plant operators supplied erroneous weather information or because the data were incorrectly processed by the Japan Nuclear Energy Safety Organization, which was tasked with creating the projections.
The process of calculating the projections for the remaining 14 plants across the country, including disaster-hit Fukushima No. 1 operated by Tokyo Electric Power Co., also contained errors or was mishandled, although this did not result in drastic changes in the projections, according to the NRA’s secretariat.
The simulation showed the distances at which doses could reach 100 millisieverts a week after a severe crisis like last year’s three meltdowns at Fukushima No. 1. At that dose level, evacuation is recommended by the International Atomic Energy Agency.
The latest projections show the most distant point where such severe radiation could spread is 40.1 km east of Tepco’s Kashiwazaki-Kariwa plant in Niigata Prefecture. That point is in the city of Nagaoka.
In the earlier projections, the NRA said the most distant point would still be in Nagaoka, but 40.2 km from Tepco’s facility, the largest nuclear plant in the world.