Life extension of nuclear power plants

The life of nuclear power plants is considered to be 30-40 years, but for the reason of the difficulty in land acquisition, economy and others, the possibility of the life extension has been discussed. Secular change and life extension are explained. The new technique of probabilistic method has begun to be used for the design of structures, while probabilistic safety assessment has been carried out in nuclear power plants. The concept of probabilistic reliability assessment in equipment management is discussed. Preventive maintenance and time-planned maintenance, equipment diagnosis and equipment management technologies are explained. As the maintenance and the countermeasures to secular change for nuclear power plants, maintenance, regular inspection, the phenomena of secular change and so on are described. As the technologies for detecting material deterioration, the ultrasonic technology and the electromagnetic technology are used. As the preventive maintenance and diagnosis technologies for nuclear power plants, residual life diagnosis technology and in-operation diagnosis technology are explained. The risk assessment considering secular change is reported. (K.I.)