Reference Material: Main Accidents and Breakdowns Occurring at Nuclear Power Plants and Nuclear Fuel-Related Facilities (FY2021)

By Kamisawa Chihiro (CNIC)

These materials summarize the main accidents and breakdowns that took place at nuclear power plants and nuclear fuel-related facilities in FY2020. The materials are based on reports from the Nuclear Regulation Authority, reports issued under the Nuclear Reactor Regulation Act or the Radioisotope Regulation Act, excerpts from the Nuclear Facilities Information Disclosure Library NUCIA, and information taken from the press releases and reports of each company. Of these cases, 40 cases considered to be important for safety were taken up. Three cases requiring a report to the NRA are indicated by a “○” in the report classification (RC*) column.

The reason why the four incidents, judged to fall under the items requiring safety inspection, at the Fukushima Daiichi Nuclear Power Station (FDNPS) are dated November 11 is because they are based on the results of the inspection of the implementation plan for the second quarter of FY2020 at FDNPS, conducted by the Nuclear Regulation Authority (NRA), and were reported at the NRA meeting on November 11, 2020.

The “orifice,” which was installed in the reverse direction in Shimane Unit 3 and others, is a metal disk with a hole in the center to restrict the flow rate in the pipe. (This installation of an orifice in the reverse direction played the role of promoting pipe wall thinning in the condensate piping explosion accident at Mihama Unit 3 on August 9, 2004.)

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