ICONE23-1415 STABILITY OF IRWST INJECTION IN A PASSIVE SAFETY PWR

Abstract

The passive safety PWR, such as AP1000 and CAP1400, becomes a mainstream model to be built around the world. The largest part of coolant inventory of passive core cooling system (PXS) is stored by In-containment refueling water storage tank (IRWST). And the stability of its draining to the core is very important for the core cooling under accident condition. And the relationship between flow rate and pressure drop plays an important role on the two-phase flow oscillation. This study will investigate the relationship and its impact on the gravity draining stability. An analytic model is built for the purpose of analysis based on a quasi-steady state, in which the flow path is divided into two sides which are IRWST injection single-phase side and ADS4 riser two-phase side. Through the analysis, the pressure and the flow rate is substantially a concave curve, and this possesses the system a potential for oscillation instability. The stability is also determined by the system boundary conditions, which includes the core decay power, injection and venting line resistances, coolant subcooled temperature and other parameters. The analysis result shows a good agreement with the ACME test result.