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Rising Seawater Temperatures Prompt New Nuclear Safety Rules: TEPCO Sets Temporary Shutdown Criteria for Kashiwazaki-Kariwa Plant

Tokyo Electric Power Company Holdings announced on August 7 that it has established a set of self-determined criteria for evaluating whether to temporarily halt nuclear reactor operations at the Kashiwazaki-Kariwa Nuclear Power Plant in Niigata Prefecture, in response to rising seawater temperatures in the surrounding area. These criteria are not mandatory requirements directly imposed by external regulatory authorities, but rather proactive measures voluntarily implemented by TEPCO based on safe operational needs. According to the conditions announced by TEPCO, the company will consider temporarily shutting down the relevant nuclear facilities when the 7-day average seawater temperature in the waters surrounding the plant exceeds 31 degrees Celsius, when water temperatures above 34 degrees Celsius are observed, or when water temperatures above 33 degrees Celsius persist for 12 hours. These numerical thresholds indicate that seawater temperature has been incorporated as a key variable in nuclear power plant operational risk management.

2026-08-08

TEPCO says cooling interruption of spent fuel pool at Fukushima Daini Unit 1 due to human error

Tokyo Electric Power Company (TEPCO) announced on July 29 that the event in April 2026, where the spent fuel pool cooling system at Unit 1 of the Fukushima Daini Nuclear Power Plant was shut down for approximately 32 hours, was determined to be caused by human error. At the time of the incident, the plant was in the decommissioning phase. On April 5, a fault alarm was triggered by the cooling water circulation pump of Unit 1 at Fukushima Daini. After on-site personnel confirmed smoke from the equipment, the pump was stopped, resulting in an interruption of the spent fuel pool cooling system for about 32 hours. TEPCO previously stated that the cause was damage to the cable connecting the pump motor. According to TEPCO's latest explanation, the cable melting may be related to the installation method when the cable was replaced in 2012...

2026-07-30