Level 3 probabilistic safety assessment (PSA) requires source term to determine the offsite consequence from a potential nuclear power plant accident. Source term comprises of the types and amounts of radionuclides released into the environment under various accident conditions. Conventionally, source term models such as TID-14844, alternative source term and mechanistic source term have been used in the safety assessment of nuclear power plants. TID-14844 provides the most conservative assessment of the fission product release while alternative source term provides representative accident specific fission product release. Mechanistic source term provides the most specific fission product release that considers reactor design and safety features. Although technological advancements have been made, many countries still adhere to the TID-14844 or alternative source term methods in their regulatory frameworks. Hence it may be worthwhile reviewing different source term models and providing an analysis of the impact on offsite consequences. In this study, the three source term models were investigated and applied to offsite consequence analysis for pressurized water reactor (PWR) to evaluate the potential impact. MELCOR Accident Consequence Code System (MACCS) developed by Sandia National Laboratories (SNL) was employed to perform offsite consequence analyses. The analysis will illustrate how the implementation of different source term models affects the offsite consequences for PWR. This study would provide insight to Level 3 PSA and emergency planning zone (EPZ) assessment, which could be adapted for advanced reactors and SMRs.

Keywords: Source Term Model, Offsite Consequence Analysis, Level 3 PSA, Emergency Planning Zone, MACCS