Abstract
A conceptual design of 4S (Super-Safe, Small and Simple) is a sodium cooled fast reactor. In order to evaluate the RVACS (Reactor Vessel Auxiliary Cooling System) performance in 4S reactor (10MWe, pool-type) under the loss of RVACS stacks condition, a three-dimensional thermal-hydraulic analysis inside the reactor vessel was conducted by PHOENICS. A protected loss of heat sink accident is selected and simulated to evaluate the capability of RVACS to cool the plant safely under such an unusual condition. Analytical results show that the loss of one out of two outlet stacks has much effect on RVACS performance than that of one out of two inlet stacks. The hot plenum maximum temperature is below 480℃ even under the condition that both one inlet and one outlet stacks are lost. This result indicates that the safety criteria for the fuel element and the structure of the primary coolant boundary are satisfied enough.
