MCCI过程中混凝土类型对安全壳的影响

Effect of concrete type on containment during MCCI process

堆芯熔融物-混凝土相互作用(Molten Corium-Concrete Interaction,MCCI)是安全壳晚期失效的重要影响因素之一,可能引起安全壳功能丧失并导致大量放射性物质向环境释放。因此有必要研究和分析混凝土类型对MCCI现象的影响,以评估MCCI过程中安全壳潜在的失效风险。应用严重事故一体化分析程序MELCOR2.1,建立了大功率非能动反应堆安全壳整体模型和堆坑模型,分别研究了熔融物与典型玄武岩混凝土和石灰石-沙混凝土的相互作用,评价了该作用对安全壳完整性带来的风险。分析结果表明:在MCCI过程中,两种典型类型的混凝土的消融速度明显不同,玄武岩混凝土具有更高的侧壁消融速度;但是石灰石-沙混凝土具有更高的不凝气体产气量。研究表明:安全壳底板失效时间远超过24 h,与混凝土类型无关;计算得到的安全壳压力均低于C级承载压力,满足保护安全壳裂变产物边界24 h的目标。

[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.