DETERMINATION OF DESIGN ALTERNATIVES AND PERFORMANCE CRITERIA FOR SAFETY SYSTEMS IN A NUCLEAR-POWER-PLANT VIA SIMULATED ANNEALING

This study presents an efficient methodology that derives design alter natives and performance criteria for safety functions/systems in comme rcial nuclear power plants. Determination of the design alternatives a nd intermediate-level performance criteria is posed as a reliability a llocation problem. The reliability allocation is performed in a single step by means of the concept of two-tier noninferior solutions in the objective and risk spaces within the top-level probabilistic safety c riteria (PSC). Two kinds of two-tier noninferior solutions are obtaine d: desirable design alternatives and intolerable intermediate-level PS C of safety functions/systems. The weighted Chebyshev norm (WCN) appro ach with an improved Metropolis algorithm in simulated annealing is us ed to find the two-tier noninferior solutions. This is very efficient in searching for the global minimum of the difficult multiobjective op timization problem (MOP) which results from strong nonlinearity of a p robabilistic safety assessment (PSA) model and nonconvexity of the pro blem. The methodology developed in this study can be used as an effici ent design tool for desirable safety function/system alternatives and for the determination of intermediate-level performance criteria. The methodology is applied to a realistic streamlined PSA model that is de veloped based on the PSA results of the Surry Unit 1 nuclear power pla nt. The methodology developed in this study is very efficient in provi ding the intolerable intermediate-level PSC and desirable design alter natives of safety functions/systems.