Japan's regulator says steam leak at Mihama Nuclear Power Plant Unit 3 was "avoidable"

On August 19, Japan's Nuclear Regulation Authority (NRA) released the results of its nuclear regulatory inspections for the first quarter of the current fiscal year, determining that the steam leak incident at Mihama Nuclear Power Plant Unit 3, operated by Kansai Electric Power Co., in May this year was "foreseeable within a reasonable range" and that the associated losses "could have been avoided."

The incident occurred in the high-pressure turbine area of Mihama Unit 3. A small hole approximately 8 centimeters long and 1 centimeter wide appeared in the metal cover atop the high-pressure turbine casing, causing a steam leak that forced a manual reactor shutdown.

In its assessment, the NRA concluded that the event was foreseeable and could have been prevented through appropriate management or maintenance measures. However, since no pipe rupture or fire occurred between the onset of the steam leak and the reactor shutdown, the NRA rated the significance and severity of the incident at the lowest of four levels.