Results of a German probabilistic risk assessment study for the HTR-1160 concept

The paper reviews ''Accident Initiations and Progression Analysis'' methodology and results which applied to the German equivalent of the HTGR-1160 and German site conditions. The investigation of accidents contributing to risk was concentrated on those event sequences which lead to major release of core inventory or - with less importance - to release of plate-out activity together with coolant gas activity. With regard to release mechanisms severe HTR-accidents were grouped into: a) water ingress events with fission product release due to hydrolysis of defective coated particles and desorption of plate out activity and b) core heating events with fission product release after coated particle failure due to excessive temperatures