Experimental research on the influence of rolling motions on the convection behaviors inside two-layer corium pools

Abstract

In realms of nuclear safety analysis, In-vessel retention (IVR) has been a research focus as it is a promising mitigation strategy for the postulated severe accidents in pressurized water reactors (PWRs). However, the recent development of ocean floating reactors for civil use has greatly motivated the pertinent studies under motion conditions, which can be much different from the known investigations conducted under static condition without the additional acceleration forces induced by motions. Thus, through experimental research, this paper extensively studied the influence of rolling motions on the convection behaviors inside two-layer corium pools, which are the major concerns for IVR research. Transient behaviors of the layered corium pools were obtained, and sensitivity analyses were conducted on three critical parameters, i.e. maximum rolling angle, rolling period and the thickness of metal layer. Experimental results show that the two-layer fluids can stay basically stratified under rolling conditions but mixing phenomena can be observed in the interface nearby region when rolling motions become intense enough. Generally, rolling motions can weaken the thermal stratification inside the layered corium pool, and enhance heat removal capacity from the corium pool to the outside cooling boundary. These phenomena indicate a good chance for the efficient decay heat removal from the corium pool under rolling motions. This study is supposed to provide valuable references to assess the success probability of IVR design applied in reactors operated under ocean conditions.