Numerical Study of Two-Stage Safety Injection Tank in a Small Modular Reactor

Abstract

Numerical analyses were performed for a two-stage safety injection tank (TSIT), which is able to passively inject coolant with a single tank in two stages in case of a loss of coolant accident (LOCA) in a small modular reactor. At the early stages of the accident, coolant of the TSIT is injected at a high flow rate into the reactor. When the TSIT water level is reduced lower than the predetermined level, the TSIT injection flow rate is instantaneously reduced to a lower flow rate in a passive manner. Subsequently, coolant of the TSIT is injected at a low flow rate for a long period of time until the TSIT is depleted. The effects of the break size, installation height of the tank, installation height of the injection hole, and pressure-loss coefficient of injection line on the TSIT injection performance were examined numerically. With pertinent design parameters, the TSIT could satisfy its design requirements in an integral reactor, by providing two-stage coolant injection for at least 72 hours after a LOCA.