The Nuclear Regulation Authority said Thursday it would require Kansai Electric Power Co., operator of the Oi nuclear plant, to close it down if the fault beneath key equipment is found to be active, Asahi Shimbun reported.
The government's nuclear safety standards stipulate no key component of a nuclear plant should be installed directly above an active fault.
Japan's new coalition government, which took office Wednesday, said it would decide within three years whether operations could resume at Japan's 50 nuclear reactors.
NRA Chairman Shunichi Tanaka said that timeline is too short for safety screenings to be completed for all 50 reactors.
"We cannot enter safety screenings (that should precede a restart) if it is officially decided that (an active) fault runs directly beneath a nuclear reactor building," Tanaka said.
He acknowledged a report on the Oi plant has yet to be published and a formal conclusion has yet to be reached.