Loss of coolant accident analysis of a supercritical-pressure water-cooled fast reactor with downward flow channels

This paper describes loss of coolant accident (LOCA) analyses on the supercritical-pressure water-cooled fast reactor called 'Supercritical pressure water-cooled fast reactor (SWFR)'. The features of the SWFR are the high power density and using the downward flow channels to increase the economic potential of SWFR with high outlet steam temperature. In LOCA event, the SWFR will have large pressure and coolant density change. This change influences the flow distribution among the downward flow parallel channels. It will affect the safety of the SWFR in LOCA event. The LOCA analysis is carried out by numerical codes 'SPRAT-F-DP' and 'SCRELA-M'. The SPRAT-F-DP can treat the blowdown phase of LOCA with one dimensional node junction model and momentum conservation model for flow distribution of the downward flow channels. SCRELA-M can calculate the reflooding phase of LOCA considering the flow distribution among fuel channels by solving the momentum conservation equation. Keeping adequate flow rate to the core is important for the safety of SWFR. In LOCA condition, it is difficult to keep adequate flow rate. Therefore, with the early actuation of Automatical Depressurization System (ADS), the SWFR can increase the flow rate under LOCA condition. Analysis results show that the SWFR can satisfy the safety criteria with the change of coolant flow distribution at normal operation. (author)