Mahdi Saghafi

This paper deals with determination of the minimum number and identification of the best configurations of passive autocatalytic recombiners (PAR) for the effective design of the containment in a pressurized water reactor (PWR). It considers the current design of PAR in the containment of a PWR and for that tries to identify, through a large number of sensitivity analyses, the minimum required number of PARs in different compartments. In this regard, a qualified nodalization has been developed for best estimate modeling by MELCOR integrated code. The developed model includes primary and secondary systems, containment, and related safety systems. A large number of simulations including the plant specific probabilistic safety assessment and success criteria analysis are used to identify the accident scenario with the highest amount of hydrogen production and risk. We first screened postulated accidents based on the PSA results and then based on the deterministic severe accident computations. It is found that the large break loss of coolant accident (LB-LOCA) without emergency core cooling system (ECCS) actuation is the bounding case from the hydrogen hazard point of view. To find the optimal configuration with minimum number of PARs in the containment, 40 different configurations are analyzed for the selected accident for a Westinghouse type PWR. The main finding of this work is identification of the minimum required number of PARs and their best distribution among the associated compartments. The obtained configuration is equally effective for the hydrogen risk mitigation with 36% reduction in the number of PARs in comparison to the base case design. The methodology of the analysis can be used for other plants.