The Nuclear Regulation Authority said Tuesday it has found more errors in its recently announced projections for the spread of radiation from reactors in the event of a severe accident.
The errors surfaced about a week after the NRA had corrected simulation results for six nuclear power plants and Chairman Shunichi Tanaka had instructed the secretariat staff to make sure they would prevent a recurrence.
The latest errors were found in the projections for the Kyushu Electric Power Co. Genkai power plant in Saga Prefecture, and Sendai plant in Kagoshima Prefecture. The NRA secretariat said wind direction data submitted by Kyushu Electric were in error.
Spokesman Hideka Morimoto, however, said the blame is on the secretariat and the Japan Nuclear Energy Safety Organization, which were tasked with creating the projections, because they relied on utilities to secure firsthand information and did not have sufficient checking functions on their own.
In Fukuoka, Kyushu Electric Executive Vice President Masanao Chinzei had to hold the obligatory news conference.
"We sincerely apologize for causing trouble" by providing the erroneous data, Chinzei said.
The simulation results were announced Oct. 24 to provide references for local governments to expand areas that should be subject to special preparations against nuclear disasters to 30 km from a facility.
It is the third time the NRA corrected the results. The authority revised part of its initial presentations immediately after announcing them Oct. 24.
As the current simulation results have limitations in that they do not take into account geological formations in areas around the plants, Morimoto said Tanaka also ordered the secretariat staff to swiftly develop an "advanced" version.
The NRA hopes to provide new projections that will be useful for local governments to craft nuclear disaster mitigation plans by March, Morimoto added.