Experimental Research on Passive Residual Heat Removal System of Small Modular Reactor under SBO

Based on the design characteristics of the passive residual heat removal system（PRHRS） for small modular reactor, a scaled experimental facility of passive safety system CREST was constructed. A short-term residual heat removal experiment under the station blackout accident（SBO） was performed in the CREST facility, and the cooling capacity and operation characteristics of the PRHRS was studied. The results show that, after the station blackout accident, the PRHRS can be started effectively, in which a stable two-phase natural circulation between the steam generators and the heat exchanger was established with a mass flow of 0.4T/h, thus the core decay residual heat and the sensible heat were removed to the water in the containment water tank（CWT） effectively. The cold water from the core makeup tanks（CMTs） was injected into the reactor pressure vessel for core cooling. During this period, the peaked primary pressure was 16.3 MPa and less than the relief valve opening pressure 16.9 MPa. In addition, the average coolant temperature of the reactor core reduced below 210 ℃, and the operation of the reactor was in safe condition..