Abstract:  In this study, based on the design characteristics of the small modular PWR, the emergency core cooling system (ECCS) scheme was analyzed for accident cases by applying the deterministic and probabilistic methods. The primary analysis shows that there is quite different requirement for the system scheme of the accumulator by deterministic and probabilistic methods. When the safety goal is ensured, it is suggested to eliminate the safety class accumulators (ACC) for ECCS simplification and other existing source water, such as IRWST in residual remove system, can be used after CMT failure.