Shimazaki on active fault (Aomori)

July 26, 2013

Nuclear regulator hints at possible active fault off Aomori peninsula

http://mainichi.jp/english/english/newsselect/news/20130726p2a00m0na016000c.html

Kunihiko Shimazaki, acting chairman of the Nuclear Regulation Authority (NRA), has hinted that a seabed fault off the Shimokita Peninsula in Aomori Prefecture, which is dotted with nuclear fuel cycle facilities, may be active.

In an interview with the Mainichi Shimbun on July 25, Shimazaki, an NRA commissioner who heads the authority's geological fault investigation team, said there is a possibility that the 84-kilometer fault on the edge of the continental shelf is active.

The NRA will make a final judgment on the fault's status after checking the results of an ongoing joint probe by Japan Nuclear Fuel Ltd. (JNFL), operator of the Rokkasho Reprocessing Plant, and other operators.

If the fault is determined to be active, the operations of nuclear fuel cycle facilities on the peninsula are expected to be affected. The fault lying east of the peninsula runs from north to south and could trigger a magnitude-8 level earthquake if it moves.

JNFL and other operators have ruled out the active-fault theory in past safety screenings. But multiple experts have pointed out that the fault may be active, leading JNFL and other operators including Tohoku Electric Power Co., operator of the Higashidori Nuclear Power Plant in Aomori, to jointly reinvestigate faults since last November.

"There is a special structure unseen in other faults," Shimazaki said in the interview, adding the JNFL's past data cannot rule out the possibility that the fault is active. He said officials would reach a decision after examining the results of the joint research by the operators, to be compiled as early as September.

"We need more accurate data to draw a conclusion," he said.

If the fault is deemed active, the operating schedule of the reprocessing plant and the Higashidori power station may be delayed.

Commenting on applications by four electric power companies to restart 12 reactors at six nuclear power plants, Shimazaki, a leading seismologist, said the utilities should be sincere in their efforts to protect nuclear safety.

"We want them to be dead serious about making preparations for a tsunami," he said. He pointed out that nuclear power plant operators varied in their levels of preparedness for future natural disasters.