The Japanese government intends to limit the service life of nuclear power plants in Japan to 40 years. This line was set forth in the new policy on nuclear safety regulation announced January 6 by Goshi Hosono, Nuclear Disaster Minister and Minister of the Environment. He intends to explicitly note this limitation in a bill for revision of the Law on the Regulation of Nuclear Source Material, Nuclear Fuel Material and Reactors, and to place this bill before the ordinary session of the National Diet, which is to be convened as early as this month, in hope of early passage into law.
Although it leaves margin for exceptional cases in which operation past 40 years is allowed for reactors equipped for safety in conformance with the latest knowledge, Hosono made it clear at a press conference that operation extensions would be recognized only in “very exceptional” cases. He also stated that decisions would be made on the basis of scientific grounds, with no room for influence by political considerations. Nevertheless, he did not comment on the reasons for selection of 40 years for the limitation.
Asked about the grounds for the 40-year limit, the Nuclear Safety Agency Preparation Office, which is preparing for inauguration of a new nuclear safety regulatory organ (tentatively titled “Nuclear Safety Agency”) targeted for establishment in April, asserted that a 40-year period was the assessment guideline for reactor pressure vessel embrittlement due to neutron irradiation.
At the Fukushima I nuclear power station, which caused a severe accident last year, more than 40 years had passed since the start-up of unit 1 at the time. So far, there has not emerged any definitive evidence that the catastrophe was worsened by a deterioration of the facilities. The scientific grounds for selection of 40 years as the limit appear to be thin, and this is likely to stir subsequent discussion.
