A panel under the Nuclear Regulation Authority agreed Thursday that faults under Tohoku Electric Power Co.'s Higashidori atomic plant in Aomori Prefecture are probably active, rejecting earlier arguments to the contrary by the utility.
The situation does not violate the nation's nuclear plant laws because the faults do not run directly beneath the sole reactor at the Higashidori complex, but it may make it difficult for the utility to have the reactor restarted anytime soon.
The Higashidori plant is the third site where the NRA, which debuted in September, has sent experts to check faults suspected of being active.
The focus of the discussion has been the fault F-3, which runs vertically through the plant's premises, and fault F-9, which parallels F-3.
Tohoku Electric has said deformations observed in geological layers were created by clay minerals that swelled on exposure to water, and not because active faults exist under the complex.
The reactor at the Higashidori plant started commercial operations in December 2005 and went offline for regular checks in February 2011, shortly before the nuclear crisis erupted at Tokyo Electric Power Co.'s Fukushima No. 1 plant.
The area just north of the Higashidori plant is also where Tepco plans to build its own Higashidori plant.
Another team of experts led by the regulatory body has already agreed that a fault running directly underneath a reactor at Japan Atomic Power Co.'s Tsuruga plant in Fukui Prefecture is probably active, an assessment that could leave the utility with no option but to scrap the unit.
A similar team appointed by the NRA visited Kansai Electric Power Co.'s Oi plant, also in Fukui Prefecture, for an assessment, but it has not yet reached a conclusion. Two reactors at Kepco's Oi plant are the only units now operating in Japan.