MSR Simulation With cGEMS: Fission Product Release And Aerosol Formation

The release of fission products and fuel materials from a molten salt fast reactor fuel in hypothetical accident conditions was investigated. The molten salt fast reactor in this investigation features a fast neutron spectrum, operating in the thorium cycle, and it uses LiF-ThF4-UF4 as a fuel salt. A coupling between the severe accident code MELCOR and thermodynamical equilibrium solver GEMS, the so-called cGEMS, with the updated HERACLES database was used in the modeling work. The work was carried out in the frame of the EU SAMOSAFER project. At the beginning of the simulation, the fuel salt is assumed to be drained from the reactor to the bottom of a confinement building. The containment atmosphere is nitrogen. The fission products and salt materials are heated by the decay heat, and due to heating, they are evaporated from the surface of a molten salt pool. The chemical system in this investigation included the following elements: Li, F, Th, U, Zr, Np, Pu, Sr, Ba, La, Ce, and Nd. In addition to the release of radioactive materials from the fuel salt, the formation of aerosols and the vapor phase species in the modeled confinement were determined.

本研究针对假想事故工况下熔盐快堆（Molten Salt Fast Reactor）燃料内裂变产物与燃料物质的释放行为开展了系统探究。本次研究涉及的熔盐快堆具有快中子能谱，运行于钍燃料循环体系，其燃料盐采用LiF-ThF4-UF4组分。本次建模工作采用了耦合更新版HERACLES数据库的严重事故分析程序MELCOR与热力学平衡求解器GEMS的联合求解框架，即cGEMS。本研究工作依托欧盟SAMOSAFER项目实施。模拟初始时刻，假设燃料盐从反应堆排放至安全壳建筑底部，安全壳内气氛为氮气。裂变产物与盐类物质受衰变热加热，进而从熔盐池表面蒸发逸出。本次研究的化学体系涵盖以下元素：锂（Li）、氟（F）、钍（Th）、铀（U）、锆（Zr）、镎（Np）、钚（Pu）、锶（Sr）、钡（Ba）、镧（La）、铈（Ce）以及钕（Nd）。除燃料盐中放射性物质的释放过程外，本研究还同步确定了模拟安全壳内气溶胶与气相物种的生成规律。