Fire alarms triggered nine times in four weeks at Japan's Fukushima Daiichi Nuclear Power Station

At 21:44 on September 3, a fire alarm was triggered in the water treatment control room building of Japan's Fukushima Daiichi Nuclear Power Station. Tokyo Electric Power Company (TEPCO) stated that no open flames or smoke were found at the scene. After firefighters arrived and conducted inspections, it was confirmed shortly after 22:30 that evening that this was “not a fire”. TEPCO said it would subsequently inspect the relevant detectors.

Including this incident, the Fukushima Daiichi Nuclear Power Station has triggered a total of nine fire alarms in the past four weeks. Previously, on August 8, a fire alarm was triggered in the maintenance building for Units 5 and 6; on August 12, an alarm sounded in the emergency diesel generator room for the high-pressure core spray system of Unit 6; on August 13, an alarm sounded in the main office building; on August 15, an alarm sounded in the southwest stairwell area of the turbine building for Unit 5; on August 18, an alarm sounded on the basement level of the turbine building for Unit 5.

In addition, on August 21, fire alarms were triggered in the access control building and the solid waste storage facility; on August 31, fire alarms also sounded in the new service building for Units 5 and 6. After each of the above alarms was triggered, fire departments confirmed within hours that no fire had occurred, and readings at the plant's monitoring stations showed no significant fluctuations.

TEPCO previously stated that the frequent triggering of fire alarms in recent days may be related to smoke detectors misidentifying water vapor as smoke. The company said that high humidity brought by approaching typhoons and rainfall could be one of the causes. Currently, the relevant detectors have been returned to the manufacturer for detailed investigation, and TEPCO is also considering replacing them with equipment more resistant to condensation.