The Nuclear Regulation Authority determined Wednesday that a reactor at Japan Atomic Power Co.’s Tsuruga nuclear plant on the Sea of Japan coast in Fukui Prefecture sits directly above an active geological fault — which may force the unit to be shut down permanently.
The NRA’s decision-making panel approved a report compiled by experts saying that at least one of the faults running under the No. 2 reactor, including one fault called “D-1,” could move in the future.
Despite the report, Japan Atomic Power is expected to apply for an NRA safety screening, which is required to resume operations of the reactor.
But the regulator’s decision is unlikely to be overturned unless Japan Atomic Power can submit new data that could put the report’s conclusion in doubt.
Under current nuclear safety requirements, plant operators are barred from building reactors and other important safety facilities directly above active faults, which are defined as those that have moved in the last 120,000 to 130,000 years.
The NRA first identified D-1 an active fault in 2013, but it conducted an additional probe after Japan Atomic Power submitted more data in trying to have that evaluation overturned.
Also Wednesday, the NRA concluded that at least two key geological faults running under the premises of Tohoku Electric Power Co.’s Higashidori nuclear plant in Aomori Prefecture could move in the future.
Unlike with the Tsuruga reactor, the decision won’t immediately force Tohoku Electric to scrap the sole reactor at the Pacific coast plant, as the faults do not run directly beneath the unit.
Still, the facility could remain offline for quite a while, as Tohoku Electric will likely be required to take further measures to enhance the plant’s safety before any restart.
The assessment report also said the experts were not able to obtain enough data to judge whether another fault, which runs directly beneath an important facility at the plant, is active.
Tohoku Electric has already applied for the Higashidori plant’s safety screening, a process necessary for any reactor to be allowed to go back online. The regulator is expected to resume a full-fledged review of the plant taking the report into account.
Currently, all of the nation’s 48 commercial reactors are offline amid heightened safety concerns following the Fukushima nuclear crisis triggered by the massive March 2011 earthquake and tsunami.
The administration of Prime Minister Shinzo Abe is seeking to restart reactors that have cleared the NRA’s safety review, which is based on regulations introduced after the crisis.
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