小型移动式铅铋堆运输过程堆芯进水事故工况下临界安全问题研究

小型移动式铅铋堆由于在海岛、偏远地区等场景的应用需要，整堆运输的安全可行性成为必要设计目标之一。基于小型移动式铅铋堆自身特点，采用谱移吸收材料的反应性控制手段进行反应性控制方案研究，以确保整堆运输的临界安全。利用MCNP软件计算在运输过程、堆芯进水事故工况下表面涂覆不同厚度Gd2O3涂层的燃料芯块的有效增殖系数（keff），其中涂层厚度为50μm时满足临界安全要求；分析加入谱移吸收材料后堆芯的燃耗特性、功率分布和传热，验证表明其不影响堆芯正常运行，确定了此种反应性控制方案的可行性。

Study on Criticality Safety in the Case of Core Water Inlet Accident During Small Mobile Lead-bismuth Reactor Transportation

For the needs of application scenarios such as islands and remote areas, the safety and feasibility of the whole reactor transportation has become one of the necessary design objectives of small mobile lead-bismuth reactor. Based on the characteristics of small mobile lead-bismuth reactor, the reactivity control method of spectral shift absorber (SSA) is adopted to study the reactivity control scheme to ensure the criticality safety of the whole reactor transportation. MCNP software is used to calculate the effective multiplication factor (k_eff) of fuel rod pellets coated with Gd₂O₃ coating of different thickness during transportation and in case of core water inlet accident, where the coating thickness of 50 μm meets the criticality safety requirements; The burnup characteristics, power distribution and heat transfer of the reactor core after adding SSA are analyzed. The verification shows that it does not affect the normal operation of the reactor core, and the feasibility of this reactivity control scheme is determined.