Abstract: Diluting the core melt with oxide sacrificial material (OSM) during in-vessel retention (IVR) is a promising severe-accident-management strategy of advanced LWRs. When the relocated core melt is diluted by OSM, the mass and volume of the core melt mixture increase and the oxide layer locates in the cylindrical portion of RPV due to the inverse stratification of melt pool configuration. Therefore, researches on the structural integrity are essential to evaluate the effectiveness of the strategy. In this paper, elastic-plastic finite element analyses of RPV during IVR with and without OSM were investigated. The results show that structural failure prefers to occur in the discontinuous part of RPV. The discontinuous part reaches ultimate limit state during IVR without OSM. However, the local maximum principle strains in the direction along the wall meridian (longitudinal bending) are about 3.9%, indicating margins to tearing. When OSM is used during IVR, a core of strong (below yield) material appears everywhere, which means that the ultimate limit state does not appear even in the discontinuous zone. Moreover, the thickness of the core material below yield becomes larger in the positions far away from the discontinuous part. Tearing will also not happen in the discontinuous zone. Therefore, the RPV can suffer enhanced load during IVR with OSM.