A panel advising the Nuclear Regulation Authority said Monday it can’t rule out the possibility that key geological faults running under the Higashidori nuclear power plant in Aomori Prefecture are active.
This won’t immediately force Tohoku Electric Power Co. to scrap the sole reactor at the plant as the faults don’t run directly beneath the unit, but it will probably have to remain offline much longer than was expected so further safety measures can be taken.
In compiling a new report on the assessment of geological faults at the plant, the panelists agreed that explanations and data submitted by Tohoku Electric are not sufficient to prove that two major faults, called F-9 and F-3, are not active.
The panel already acknowledged in May 2013 that the faults are likely to be active, but it has continued discussions after the utility conducted an additional probe in an effort to have the view overturned.
“The draft report does not show sufficient evidence to deny our claim,” Tohoku Electric Executive Vice President Nobuaki Abe told a news conference Monday. “We would like the NRA to create an opportunity for (more) debate.”
In quake-prone Japan, building reactors or other important safety facilities directly above active faults is prohibited.
The experts were divided over the activity of the f-1 fault, which runs directly beneath an important safety facility at the plant, and left open both possibilities. But they concluded that the f-2 fault, which lies right under the reactor building, is not active.
Despite the problem of geological faults, Tohoku Electric has already applied for a safety screening by the NRA, a necessary process for a reactor to be reactivated.
The regulator is expected to start full-fledged safety screening once the report is finalized.
In a related move, it has become highly likely that a reactor at Japan Atomic Power Co.’s Tsuruga nuclear plant in Fukui Prefecture will be shut down permanently after experts acknowledged that it is sitting right above an active fault.
Currently, all of Japan’s 48 commercial reactors remain offline amid heightened safety concerns following the Fukushima crisis. The administration of Prime Minister Shinzo Abe is aiming to restart reactors that have cleared the NRA safety review based on new regulations introduced following the crisis.