Reference Material: Main Accidents and Breakdowns Occurring at Nuclear Power Plants and Nuclear Fuel-Related Facilities (FY2023)

By Kamisawa Chihiro (CNIC)

Major accidents and breakdowns at nuclear power plants (NPPs) and nuclear fuel-related facilities in fiscal 2023 are summarized in this report. The data were obtained from the Japanese database system Nuclear Facilities Information Archives (NUCIA) and from press releases and reports from nuclear-related business operators. The cases reported here include items classified as “T” from NUCIA (reports of trouble, 6 items) and “M” (maintenance room information, 57 items), comprising a list of accidents and equipment breakdowns that have occurred. Among the “M” items, the one dated April 20 is actually a list of problems reported on that date by Kansai Electric Power Co. (Kanden) that had occurred recently to that time at the Mihama 3, Ohi 3 and 4, and Takahama 1, 3 and 4 reactors.

While it has not been reported on in Nuke Info Tokyo yet, a mishap occurred on October 4 at the high-level radioactive waste storage center in Rokkasho Village, resulting in the suspension or perhaps inoperability of the air supply and exhaust system throughout the center; quite a serious accident. A state has actually arisen now in which hydrogen could not be cleared from a facility where hydrogen accumulation was an issue. Although this state lasted only a very short time, what’s at issue is that the mechanism for maintaining negative pressure throughout the building to prevent radiation leakage to the outside could be so easily disrupted.