In December of 2012, Japan’s Nuclear Regulation Authority determined that the Urazoko fault, which runs near the Tsuruga nuclear power plant, was likely active. At a press conference at the time of the announcement, NRA Chairman Shunichi Tanaka, told reporters he felt the authority could not allow the restart of the reactors, because they could not implement safety assessments for the resumption (of the plant) given the risk from the Urazoko fault. “The existence of the active (Urazoko) fault raises serious concerns. And I can’t imagine what kind of measures could be taken (by the company) for the safe operation of the two reactors” if it is found to be connected to faults running directly underneath them, NRA Chairman Shunichi Tanaka said. When asked how long Japan Atomic Power could be prohibited from resuming operations at the plant in such an event, Tanaka said it might have to wait “until the active fault is gone” — meaning that the plant would need to be decommissioned.
In May of this year the NRA confirmed Tanaka’s fears when they released a report which determined that the Tsuruga Nuclear Power Plant Unit 2 reactor in Fukui Prefecture was constructed upon an active underground fault named D-1, which did in fact run directly from the Urazoko fault underneath reactor 2. At the time that the report was released, the head of the panel which conducted the investigation and wrote the report claimed that safety at Tsuruga was low and that it was a “matter of luck” that there had not been an accident there.
After the release of the report, the NRA issued an instruction to Japan Atomic Power, the utility which operates the Tsuruga nuclear power plant that instructed them to assess how the underground fault could affect spent-fuel assemblies. Instead of complying with the request, the utility stalled for two months before they filed a petition seeking to revoke the safety regulator’s orders, arguing that there was no fault active or dormant under the facilities.
In the objection filed by the utility, Japan Atomic Power argues that providing such an assessment of the risk to spent fuel would be akin to concluding that the fault is active, which they fervently deny. If the utility is unable to convince regulators that there is no fault under the reactor then they will be forced to decommission the reactor.
Source: JiJi Press