钠冷快堆严重事故下熔堆事故以及钠火事故是安全评估中的重要关键现象，也是世界快堆安全研究的重点方向。为提升我国钠冷快堆安全评估能力，拟开展钠冷快堆严重事故下熔堆事故以及钠火事故分析方法与基础现象研究。本项目采用理论、实验与数值模拟相结合的方法，在钠冷快堆熔堆事故相关的关键模型研究基础上，建立快堆堆芯多相态、多组分物理热工结构耦合分析模型并应用于熔堆事故进程分析；基于机理实验研究，建立快堆堆芯碎片床分层无量纲判定准则以及碎片床分层模型并开展堆芯碎片床可冷却性分析；针对含绕丝燃料组件，建立两相流动全流型子通道热工水力分析模型，开展组件内沸腾传热以及不稳定性分析；建立液钠泄漏雾化机理模型，开展钠燃烧机理研究。通过本项目的研究，对钠冷快堆严重事故下熔堆事故以及钠火事故多态多相物理机理、对开发相应分析工具具有科学意义，对考虑经济性与安全性相结合的工程安全系统的设计具有实际应用价值。

The core meltdown accident and sodium fire accident are important phenomenon in safety evaluation of severe accident of sodium-cooled fast reactor (SFR),which are interesting topics of safety study of SFR in the world. In order to improve the ability of safety evaluation of SFR in China, the basic phenomenon and analytical methods of core meltdown accident and sodium fire accident will be studied in this project. Based on the study of key mechanism and model in the process of core meltdown accident, by using theoretical analysis, experiment and numerical simulation, a multi-phase and multi-component physical thermal coupling analytical method for SFR will be established , which will be used in the analysis of accident of SFR. Based on the experimental and theoretical study on the mechanism of the debris bed stratification, a criterion and a model for the debris beds stratification will be established, which will be used to coolability analysis of the debris bed during severe accident. A two-phase flow full-flow sub-channel thermal hydraulic analytical model will be developed for the study of liquid sodium boiling inside the wound wire fuel assembly. A liquid sodium atomization mechanism will be studied and related model will be established, used for development of the sodium spray fire analytical model which will be used to evaluation the risk of sodium spray fire. The research aided by this project, not only has theoretical significance to understand multphase thermal physical mechanism of special configuration during SFR severe accident and sodium spray fire and to develop corresponding analytical tool, but also has engineering importance for the development of engineering safety system.