Alex Luta:
The [40-year] limit on the life spans is legally binding, but it is distinct from the recent statement by the Cabinet.
RK:

Not so. In January, the Noda administration submitted a bill to the Diet that would have limited the life of all nuclear plants to 40 years, but caved to the LDP's demand to allow a 20-year extension if authorities ruled that the plant was still safe. The law came into effect in June. In July, NISA used the escape clause to grant an extension to 40-year-old reactor at Mihima operated by Kansai Electric. The head of the new NRA, Shunji Tanaka, a former vice chair of the Atomic Energy Commission--who says that "The most important thing is to recover confidence in the nuclear safety administration"--told a press conference that he would enforce the 40-year limit, saying that, "It would be extremely difficult [for a nuclear reactor] to get an extension." But, if he changes his mind, there is nothing in the law to prevent him from doing so. The first test is whether to rescind NISA's decision on Mihima.

PM: Not quite: In early June NISA used the old law to call for extending the life of the Mihama plant by 10 years. However, once the new law came into effect this was automatically reduced to 3 years. Any extension after that would require another review and more stringent standards. In the meantime NISA ordered a study of whether there is an active fault under Mihama.
If one is found, under the new law the plant must close. And this week the Noda cabinet used the 40 year rule as the basis for announcing its intention to close the Mihama reactors.

Paul Midford
Norwegian University for Science and Technology