Simulation of the Westinghouse AP1000 Response to SBLOCA Using RELAP/SCDAPSIM

Great interest is given now to advanced nuclear reactors especially those using passive safety components. The Westinghouse AP1000 Advanced Passive pressurized water reactor (PWR) is an 1117？MWe PWR designed to achieve a high safety and performance record. The AP1000 safety system uses natural driving forces, such as pressurized gas, gravity flow, natural circulation flow, and convection. In this paper, the safety performance of the AP1000 during a small break loss of coolant accident (SBLOCA) is investigated. This was done by modelling the AP1000 and the passive safety systems employed using RELAP/SCDAPSIM code. RELAP/SCDAPSIM is designed to describe the overall reactor coolant system (RCS) thermal hydraulic response and core behaviour under normal operating conditions or under design basis or severe accident conditions. Passive safety components in the AP1000 showed a clear improvement in accident mitigation. It was found that RELAP/SCDAPSIM is capable of modelling a LOCA in an AP1000 and it enables the investigation of each safety system component response separately during the accident. The model is also capable of simulating natural circulation and other relevant phenomena. The results of the model were compared to that of the NOTRUMP code and found to be in a good agreement. 1. Introduction Nuclear energy is increasingly considered as an attractive energy source that can deliver an answer to increasing worldwide energy demands. One of the most important public concerns, when dealing with nuclear energy, is the safety of nuclear power reactors. The main safety concern is the emission of uncontrolled radiation into the environment which could cause harm to humans at both the reactor site and off-site. Therefore, it is important to evaluate the safety performance of nuclear reactors. Great interest is now given to advanced nuclear reactors especially those using passive safety components. Passive safety systems are used to provide significant improvements to plant simplification, safety, reliability, investment protection, and capital costs. The Westinghouse Advanced PWR, AP1000, design includes advanced passive safety features and extensive plant simplification to enhance the safety, construction, operation, and maintenance of the plant. The Westinghouse AP1000 Advanced Passive pressurized water reactor (PWR) is an 1117 MWe 2-LOOP PWR based closely on the AP600 design. The AP1000 maintains the AP600 design configuration, the use of proven components, and the licensing basis by limiting the changes to the AP600 design to as few as possible [1]. The