The Nuclear Regulation Authority (NRA) is set to relax regulations on dry storage facilities for spent nuclear fuel generated at nuclear power plants, including their quake resistance, it has been learned.
The move is aimed at promoting the dry storage of spent nuclear fuel across the country as the method poses extremely low accident risks in the event of earthquakes. The NRA will also look into eliminating the need for power companies to forecast basic earthquake ground motion for dry storage facilities when designing them and even allowing outdoor storage of casks containing spent nuclear fuel.
Unlike spent nuclear fuel pools where the fuel is cooled by water, dry storage does not require power sources as casks containing spent fuel are cooled down by the outside air. In the case of the Fukushima No. 1 Nuclear Power Plant disaster, there were fears that water in the pools at the No. 1 through No. 4 reactors could have vaporized due to the loss of power, making it impossible to cool down the large volume of spent fuel in them and leading to another serious accident. Meanwhile, the spent nuclear fuel kept in dry storage on the plant's premises was intact despite the tsunami attacks on its casks.
In Japan, most of the approximately 17,000 metric tons of spent nuclear fuel is stored in pools at nuclear plants. While the NRA has requested that utilities transfer spent nuclear fuel to dry storage, none of the plant operators have abided by the request since the Fukushima meltdowns. Behind the reluctance apparently lie local residents' concerns that storage of spent nuclear fuel could be prolonged if it is kept in dry storage, compared to the fuel being "temporarily stored" at nuclear plant pools.
The NRA is currently screening the safety of two dry storage facilities -- an interim storage facility under construction in Aomori Prefecture, which is jointly funded by Tokyo Electric Power Co. and the Japan Atomic Power Co., and a dry storage facility at Chubu Electric Power Co.'s Hamaoka nuclear plant in Shizuoka Prefecture. The screenings are taking a long time because the new regulatory standards introduced after the onset of the Fukushima crisis require utilities to anticipate basic earthquake ground motion for nuclear plant facilities and make sure buildings accommodating fuel-containing casks do not collapse and the casks fixed to the floor do not fall over.
The NRA deems that there will be low risks of accidents at dry storage facilities even in case the facilities collapsed, as casks are supposed to be designed to withstand the impact of being dropped from a height of 9 meters and are used in the transport of spent nuclear fuel. The NRA believes that excessive regulations are keeping utilities from adopting the dry storage method.
"It is not particularly necessary to require strict quake resistance at buildings (for dry storage)," said NRA Chairman Shunichi Tanaka.
It is not uncommon abroad for casks containing spent nuclear fuel to be kept out in the open.