Application of Probabilistic Method in the EPZ Determination of SMR

A probabilistic method involving accident frequency is considered to be applied in the emergency planning zone (EPZ) determination for a small modular reactor (SMR), taking the ACP100 demonstration project as a case study. Two categories of severe accident spectrum are determined. One is the more probable accident of total spectrum of level 2 PSA; the other is the more severe accident of early containment failure or bypass with very low frequency. Complementary cumulative distributions (CCDF) are calculated in this probabilistic EPZ determination method, indicating dose exceeding probabilities at different distances, with the consideration of weighted accident frequencies. The results show that based on the low radioactivity inventory, high inherent safety, and enhanced aerosol deposition capability, the EPZ size of ACP100 can be significantly reduced in contrast with current large pressurized water reactors (PWR). For the more probable accident, off-site emergency protection actions for public can be avoided for ACP100. For more severe accident proven to be "practically eliminated", the resulting influence area of deterministic health effect can also be confined to a radius of 2.5 km. The research in the paper demonstrates the feasibility of the EPZ size of SMR being less than 3 km, and provides a technical basis for the simplification of emergency arrangements for SMRs.