SIMBRASS : A MONTE-CARLO Model for the Assessment of the Unavailability of Reactor Regional Overpower Trip Systems

Abstract

Due to the many uncertainties associated with the chain of actions which lead to a reactor trip in the event of an overpower condition, a statistical evaluation of shutdown system unavailabilities is necessary. In this paper, the general framework of a mathematical model to evaluate the unavailabilities of shutdown systems for a preselected class of Loss-of-Regulation (LOR) incidents is develop ed. The application of this model to the Bruce NGS-A Regional Overpower Trip (ROPT) shutdown systems is demonstrated, and a computerized Monte Carlo simulation code (SIMBRASS) is used to calculate shutdown system unavailabilities.