Analysis of 3-layer corium pool models in CISER2.0 code

Abstract

In present work, the corium pool stratification models in CISER2.0 code for the validity analysis of In-vessel retention (IVR) strategy were performed, and the heat flux distributed on the outside wall of the lower head were calculated. The 3-layer models in CISER2.0 code consist of three models developed by Esmaili & Khatib-Rahbar (EK), Seiler and Salay & Fichot (SF) respectively and a self-developed New Model. Among these models, Seiler Model is more conservative. The SF Model treats the composition of oxide and metal phases based on the corium thermodynamic properties. Different from the previous three models, the New Model can calculate the transient configuration of the corium pool during the process of the core melt falling into the lower plenum. The heat flux on the outside wall of the lower head was calculated for a typical 1000 MW power plant in China. It was found that the 3-layer pool predicted by Seiler Model was not formed due to the insufficient amount of stainless steel in the corium. Since both EK and SF Model require more user input parameters, when one of them changes, the configuration of the corium pool and the heat flux on the outer wall of the vessel may change significantly. The New Model has the minimum initial input parameters, resulting in consistent results for different users, and the transient corium stratification can be obtained by assuming that the corium is completely mixed and reaches thermodynamic equilibrium as it relocating in the lower plenum.