Japan’s Nuclear Regulation Authority (NRA) has said there are no active faults underneath Hokuriku Electric Power Company’s Shika NPP, contrary to a previous view presented by an NRA expert panel in 2016. NRA generally accepted Hokuriku Electric’s view that none of the faults are active.
Hokuriku Electric applied for a screening of the Shika 2 reactor under in August 2014 under the new stricter safety standards introduced after the Fukushima accident. In April 2016, the NRA team said that there was a possibility that the S-1 fault underneath the unit 1 reactor building and the S-6 fault underneath the pipes carrying coolant seawater to the unit 2 reactor could be active. The team requested more data.
Hokuriku Electric then conducted borehole investigations at 420 locations. It analysed 10 faults, examining the ages of mineral veins crossing through the faults in addition to those of the strata on top of them. It concluded that none of the faults were “active faults with possibilities of moving in the future.”
Akira Ishiwatari, the NRA commissioner in charge of screenings, said “many pieces of evidence were gathered to determine (that the faults were not active) as a result of the re-evaluation using large amounts of data.” Active faults are defined as faults which experienced activity 120,000 or 130,000 years ago.
Hokuriku Electric described the NRA’s decision as a “big step forward in the screening process toward the restart of operations,” as it will lead to a sense of safety among locals.
Image: Shika nuclear power plant in Ishikawa Prefecture, Japan