Japan's new nuclear industry watchdog acknowledged additional errors in its maps for the expected spread of radioactive substances from a serious nuclear accident, further exasperating local governments that must draw up evacuation plans.
The Nuclear Regulation Authority said Nov. 6 that it provided the wrong directions for the possible spread of radiation from the Genkai nuclear plant in Saga Prefecture and the Sendai nuclear plant in Kagoshima Prefecture. The NRA said it had been given incorrect weather data from Kyushu Electric Power Co., the operator of the two plants.
"We apologize for having to correct (the maps) once more," NRA Deputy Secretary-General Hideka Morimoto told a news conference on Nov. 6. "There are ways to conduct more rigorous verifications, including data cross-checks. I think we have to create a system to reconfirm the credibility of data."
The NRA, established in September to replace the now-defunct Nuclear and Industrial Safety Agency, created the maps to show where radiation would spread from the nation’s 16 nuclear power plants if they were hit by an accident as large as the one at the Fukushima No. 1 nuclear plant last year.
On Oct. 29, just five days after the initial release of the maps, the NRA admitted errors in the forecasts for six nuclear plants, including the Genkai and Sendai plants. Those errors came to light when Hokuriku Electric Power Co., one of the utilities that provided data, pointed them out.
The latest mistakes were found after a prefectural government raised questions.
The NRA plans to check for other potential errors and release corrected forecast maps for the two plants on Nov. 8.
Local government officials were dismayed by the errors.
"The NRA is not living up to our major expectations," said Yasushi Furukawa, the governor of Saga Prefecture, which hosts the Genkai plant.
The NRA presented the forecast maps as basic material to be used by prefectural governments to revise their nuclear contingency response plans. The NRA plans to expand the zones around nuclear plants, where local authorities must draft evacuation strategies for all residents, to a radius of 30 kilometers.
The maps show areas where weekly radiation doses are likely to reach the International Atomic Energy Agency standard of 100 millisieverts for recommending evacuation.
The repeated corrections are expected to affect the drafting of the contingency plans, which should be completed by the end of March.
The NRA said it received weather data at the nuclear plants from their operators before it created the forecast maps. Kyushu Electric’s data mixed up the windward and leeward directions for the Genkai and Sendai plants.
Kyushu Electric noticed the errors after it received an inquiry on Nov. 5 from the Kagoshima prefectural government. The utility informed the NRA of the mistakes on Nov. 6.
The previous radiation forecast maps will have to be turned about by 180 degrees.
Kyushu Electric officials apologized for the mistakes at a news conference in Fukuoka on Nov. 6.
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