On-line fatigue monitoring and probabilistic assessment of margins Original Research Article

An on-line computer-aided system has been developed by Electricité de France, the French utility, for fatigue monitoring of critical locations in the nuclear steam supply system. This tool, called a fatigue meter, includes as input data plant parameters and is based on some conservative assumptions at several steps of the damage assessment (thermal boundary conditions, stress computation,...). In this paper we present recent developments performed towards a better assessment of margins involved in the complete analysis. The methodology is illustrated with an example showing the influence of uncertainty in plant parameters on the final stress computed at a pressurized water reactor 900 MW unit pressurizer surge line nozzle. A second example is shown to illustrate the possibility of defining some transient archetypes.