Flood-prevention measures are lacking at 10 nuclear power plants — especially at connecting sections — utilities’ inspections have revealed.
The results of the ordered inspections were reported at Wednesday’s regular meeting of the Nuclear Regulation Authority.
Among the 10 are Tokyo Electric Power Company Holdings Inc.’s Kashiwazaki-Kariwa nuclear power station in Niigata Prefecture, its Fukushima No. 2 nuclear plant in Fukushima Prefecture, and the Japan Atomic Energy Agency’s Monju prototype fast-breeder reactor in Fukui Prefecture.
The NRA told the power companies last November to inspect reactor buildings and on other important equipment after some 6.5 tons of rainwater entered the No. 2 reactor building at Hokuriku Electric Power Co.’s Shika plant in September 2016.
At the Shika plant, a power panel for lighting equipment shorted out due to the water. The section connecting the No. 2 reactor building and an underground trench for power cables and other equipment was later found not to have been waterproofed.
On Wednesday, the NRA urged the utilities to take steps to make all connecting sections waterproof, except for areas where impossible due to design constraints.
“We can’t predict when rainwater inflows will occur,” NRA Chairman Shunichi Tanaka said, urging them to take the necessary steps swiftly.
According to the inspection results, connecting sections lacking water shut-off measures were found at the Kashiwazaki-Kariwa plant, Fukushima No. 2, the Monju reactor, Tohoku Electric Power Co.’s Onagawa plant in Miyagi Prefecture, Chubu Electric Power Co.’s Hamaoka plant in Shizuoka, Chugoku Electric Power Co.’s Shimane plant in Shimane, Japan Atomic Power Co.’s Tsuruga plant in Fukui, the JAEA’s Tokai nuclear fuel reprocessing plant in Ibaraki, and Japan Nuclear Fuel Ltd.’s Rokkasho fuel reprocessing plant in Aomori.
The reactors found with insufficient water stop measures were mainly boiling-water reactors.
Flood-prevention steps have already been taken at pressurized water reactors, including at Kyushu Electric Power Co.’s Sendai plant in Kagoshima. Two reactors there have cleared the NRA’s safety screenings under the new post-3/11 standards.