Abstract: [Background] Molten corium-concrete interaction (MCCI) would cause the containment to lose its protection function and result in considerable radioactive fission products release into atmosphere. [Purpose] This study aims to assess the potential failure risk of containment during MCCI process by investigating and analysis the effect of concrete type on the MCCI phenomenon. [Methods] The integrated containment and cavity models for large power passive reactor were built with MELCOR 2.1 code, a fully integrated, engineering-level computer code for severe accidents. The interactions of molten corium with typical basaltic concrete and limestone-sand concrete were investigated, respectively. The potential failure risk of containment due to the MCCI phenomenon was evaluated. [Results] The analysis results show that the ablation rates of those two typical kinds of concrete are apparent different during MCCI process, and the basaltic concrete has higher ablation rate on the side of the cavity than the limestone-sand concrete whilst the letter has more non-condensible gas production. [Conclusion] The failure time of containment basement far exceeds 24 h after MCCI starts, independent of the concrete type. All the calculation values of the containment pressure are below the pressure load level "C", which satisfies the goal in protection the fission products boundary for 24 h.

Key words: MELCOR 2.1, Containment, MCCI, Non-condensible gas, Severe accident