Design and Research on Two-Phsse Numerical Calculation for Small Modular Pressurized Reactor Cavity Injection System

Residual heat from melting core located in the bottom of the reactor vessel could be removed by cavity injection system（CIS）. The consequence of severe accident can be mitigated. The method of two phase numerical calculation which could be used to predict the under head critical heat flux（CHF） has been researched in this paper. Through the research better geometry which could bring high CHF can be found. The CHF curves of flat ellipsoid and spherical has distinct difference. Despite the maximum value is similar, the CHF curves of flat ellipsoid geometry is larger than that of spherical geometry during the central section（30°~60°）. The flat ellipsoid geometry could enhance the safety margin of the cavity injection system.