The new regulator was set up in the wake of the 2011 Fukushima disaster and it is reviewing whether any nuclear plants sit on active earthquake fault lines, which is prohibited under Japanese law.
One such plant that falls into this category is the country’s oldest reactor, Tsuruga, operated by Japan Atomic Power.
Tsuruga is one of six plants the regulator is investigating – the others include facilities run by Kansai, Hokuriku and Tohoku electric power companies.
If the plant is shut down, it could spell the end for its operator. “Japan Atomic’s survival is now in doubt,” Takashi Aoki, a Tokyo-based fund manager at Mizuho Asset Management Co, told Bloomberg.
He said the company would suffer $2.5bn in losses if ha to close its two reactors in Tsuruga and another at its Tokai Dai-Ni plant.
However Japan Atomic, which is owned by the country’s 10 regional utilities, insists the fault line below Tsuruga is not active and has branded the regulators conclusions “regrettable and unacceptable”.