Abstract
The purpose of nuclear regulation is not to impede the sound development of industry's competitiveness. Therefore, the regulations must be coherent, transparent and most of all, logical. On May 31st, 2023, a bill including rules to change the legal lifetime of nuclear power plants was approved and endorsed at the 211th ordinary session of the National Diet in Japan. An important characteristic of this legislative change is that it does not simply grant additional operating years to the original lifetime; rather, it considers the length of time that the plant was under shutdown status due to reasons not attributable to the plant owners and excludes this period from the countdown of the predetermined lifetime, thus extending the original legal lifetime. Three major problems could be listed in the procedures for changing the rules and in the new rules themselves. Firstly, the period during which this matter was discussed was too short to discuss issues raised by the change in detail. Secondly, the definitions of the period to be excluded from the predetermined lifetime are neither scientifically logical nor clear and would likely cause a great deal of confusion for both licensees and regulators when the new rule comes into effect. Thirdly, under this rule, the legal lifetime of a plant which performance is worse would be longer than that of the one with better operating performance. In particular, the second and the third problems deviate greatly from the purpose of nuclear regulation, which is not to impede the sound development of industry's competitiveness. The author strongly urges all parties involved to reconsider their decisions even after the bill has got an official approval at the National Diet.