Sensitivity of and influences on the reliability of an HTR-module primary circuit pressure boundary

The reliability of HTR-Modules for process-heat application and for electricity and steam generation was analysed for normal operation and under accident conditions. The probabilistic fracture mechanics assessment was performed with FORM/SORM on the basis of the widely used data. The calculated failure probabilities may thus be compared with similar investigations. The HTR-Module primary circuit pressure boundary as a unit showed leak-before-break behaviour in a probabilistic sense although not all of its parts did so. However, the findings may strongly depend on the stochastic data. Therefore a stochastic reference problem is defined and the results are compared to the Japanese Round Robin on a PWR section /6/. Possible changes of failure probabilities and of the leak-before-break behaviour are discussed for different criteria for the occurrence of a leak and for deviations from the stochastic reference problem such as the inclusion of NDE. The results may be used to identify those stochastic variables which have the greatest influence on the computed failure probabilities and to perhaps justify further work to provide more detailed information on them. (author)