An expert panel with the nation's nuclear watchdog remains unswerving in its assessment that fault lines running under the Shika nuclear power plant in Ishikawa Prefecture may well be active.
An expert panel with the nation's nuclear watchdog remains unswerving in its assessment that fault lines running under the Shika nuclear power plant in Ishikawa Prefecture may well be active.
The position, stated in a draft report compiled July 17 that reflects an earlier finding, throws the prospect of restarting the facility's reactors into doubt.
The plant's operator, Hokuriku Electric Power Co., will have to decommission the No. 1 reactor at the plant if it is unable to overturn the finding by the expert panel of the Nuclear Regulation Authority.
The utility is set to dispute the veracity of the panel’s analysis by citing “factual error” in the assessment.
Under new safety regulations for nuclear power plants introduced after the 2011 Fukushima nuclear disaster, no key facility or plant equipment--such as a reactor building or piping for cooling water--may be built on an active geological fault.
The report followed a tentative assessment the panel made in May. The panel comprises four outside specialists of geological faults and an NRA commissioner, Akira Ishiwatari.
The panel members will seek the advice of other experts before issuing an official report on the assessment of the fault at the Shika plant.
The fault in question, S-1, runs beneath the No. 1 reactor building.
The panel concluded it was impossible to rule out the possibility that the fault is active, citing evidence in the ground strata at the time of plant's construction.
Panel members also pointed out that other faults, S-2 and S-6, both of which run under the piping for cooling water used by the No. 1 and No. 2 reactors, may also be active.
However, they concluded that the impact of slippages of those faults on the equipment could be limited as the faults lie deep below the surface.
The NRA will also screen the No. 2 reactor, the other reactor at the Shika plant, to assess whether the facility can clear the new safety hurdles if Hokuriku Electric takes additional measures to reinforce the site.
A geological fault right beneath a key nuclear power facility could destroy the site simply because of slippage. A catastrophe would not necessarily be caused by the shaking of an earthquake.
Under the new regulations, an active fault is defined as one that has likely shifted during the past 120,000 to 130,000 years.
The Shika nuclear power plant is one of the nation’s five commercial nuclear power plants that experts have looked into to assess if they have active faults.
The panel’s conclusion marked the second time that an active fault has been suspected under a reactor building. The same problem affects the Tsuruga nuclear power plant operated by Japan Atomic Power Co.