Keynote 3 (August 26, 2015)
Prof. Toshiyuki Takagi*, Prof. Takayuki Aoki**
*Institute of Fluid Science, Tohoku University, JAPAN.
**Graduate School of Engineering, Tohoku University, JAPAN.

Plant Life Time of Nuclear Power Plants and Regulatory Limit in Japan

Maintenance activity of the plant sustains the reliability of the plant and the longtime plant operation becomes possible by the high level maintenance. The plant life time of conventional plant is usually decided from the economical reason. High quality maintenance activity assures both economical operation cost and reasonable safety margin. The highest safety is the first priority in the nuclear power plants (NPPs) and the higher risk should be avoided with rational safety measures and maintenance. The plant life time should also be decided considering the risk and maintenance costs of NPP.

In Europe and United States many plants have already been operated more than 40 years. Due to the research activities of material and system degradation, and the long effort of aging management it is now possible to evaluate accurately the risk of aged NPPs. The PSR (periodic safety review) and the rational back-fitting concept enable the longtime safe operation possible. Good and sufficient communication between utilities regulatory body also are the base of the safe operation.

In this lecture, we talk the plant life time of NPPs from the view point of maintenance activities and the survey results in Europe, United States and Japan. We also report the present situation of NPP operation and the regulatory limit in Japan, and also introduce the technical issues concerning demanded core internal structure inspections.