Research on failure model and safety boundary of ellipsoid lower head for SMR

In this paper, the common ellipsoidal lower head in SMR is taken as the research object, the original hemispherical lower head model is improved and developed, and the ellipsoidal lower head geometric model is established. Based on the failure mechanism of the ellipsoidal lower head, the stress failure model is established, and the accuracy of the model is verified by OLHF-1 experiment. Blackout accident and LOCA as the research objects of high pressure meltdown and low pressure meltdown respectively, the failure characteristics of ellipsoidal lower head in the late stage of severe accidents were analyzed, focusing on the stress, strain and temperature variation characteristics of lower head, and the safety boundary of head failure under typical accidents was calculated. Through the research of this paper, the technical problem of the lack of modeling ability of the ellipsoid lower head in the integrated program of severe accidents is solved, which lays a technical foundation for the design and development of the ellipsoid lower head and the coping strategy of the lower head failure.