Probabilistic assessment of the fracture mechanics behaviour of an HTR-module primary circuit pressure boundary

In this paper the fracture mechanical behaviour of the primary circuit pressure boundary of a planned HTR-module reactor for electricity and steam generation under normal operation is assessed probabilistically. First and second order reliability methods (FORM-SORM) are used to calculate failure probabilities. They also allow a simplified analysis of the leak-before-break (LBB) behaviour. No LBB was probabilistically identified for the reactor pressure vessel. However, failure of the pressure vessel unit in normal operation probably originates from the connecting pressure vessel or the steam generator pressure vessel. They show LBB in probabilistic terms.