Reliability investigation of the reactor safety system used to control a loss-of-coolant accident

Fault tree analyses are mostly carried out in Germany (Federal Republic) by separately considering the systems demanded in case of an accident (the mechanical system, the electric power supply and the reactor protection system). According to experience, however, such separate analyses remain often problematic, since neither interconnections are taken into account nor possibilities are provided to compare the interacting systems as to their reliability. This is illustrated by presenting a comprehensive analysis of the safety systems for the design basis accident 'Circumferential Primary Coolant Line Rupture' of a nuclear power with PWR. The analysis does not only consider the necessary mechanical systems required for the reflooding of the reactor pressure vessel and the subsequent residual heat removal, it also comprises the reactor protection system and the electrical power supply