Fatigue monitoring in nuclear power plant

For several years, Electricite de France has been developing a system for monitoring the fatigue of the critical zones of the primary circuit of its PWR plants, named 'Fatiguemeter'. A prototype was installed in January 1985 at the Bugey 2 power plant for the ongoing study, in real time, of the charging line nozzle of the cold leg. This experiment is to be extended to other zones of the reactor coolant system in 1987. The discussion here only covers the main ageing mechanism which affects the reactor coolant system, i.e. fatigue, basically originating from thermal stresses, and neglects such other aspects as irradiation, corrosion, friction and vibration, whose impact, limited, cannot be estimated with accuracy. (orig./GL)