Of the 54 nuclear reactors in Japan, 44 are being shut down because of periodic inspection and other reasons. The 10 operating units will also begin periodic inspection sequentially, leading to the shutdown of all units by April next year. While restart of a reactor after inspection requires final approval from local governments, the public distrust of nuclear power is growing after the Fukushima nuclear accident. To cope with this situation, the Japanese government introduced a scheme of stress tests to investigate the safety margins of nuclear reactors in July this year.
On October 28, Kansai Electric Power Co., Inc. submitted to the national government a primary report on the stress test of Ohi power station unit 3, which is being shut down. This was the first time a nuclear utility submitted a primary stress test report.
In the report, Kansai Electric Power analyzed whether damage to nuclear fuel can be prevented when the reactor is hit by an earthquake or tsunami whose extent is beyond expectation. It concluded that the fuel would not be damaged even if the reactor was subjected to a tremor 1.8 times the basic design earthquake ground motion (maximum motion beneath the power station assumed in the design) or subjected to a tsunami wave about four times the expected height.
The governmental Nuclear and Industrial Safety Agency (NISA) will review the primary report, and then the Nuclear Safety Commission will verify the adequacy of the review. On the basis of the Commission’s evaluation result, the government will decide on the restart of the reactor. It is expected by most that this review process will take at least two or three months, although its schedule is not set yet.
