基于RESYS程序的TOPAZ-Ⅱ反应堆系统模拟

Simulation of TOPAZ-Ⅱ Reactor System Based on RESYS Code

本文使用C++语言开发了面向先进核反应堆的通用反应堆系统分析程序RESYS,在该程序的基础上建立了热离子核反应堆电源TOPAZ-Ⅱ的模型,并对其启动瞬态和稳态工况进行了模拟。建立的TOPAZ-Ⅱ反应堆系统模型包括反应堆堆芯热工模型、热离子静态热电转换系统模型、热排放辐射散热器模型。铯热离子转换器电流密度使用Rasor模型,并使用6组缓发中子点堆动力学模型计算反应堆堆芯裂变功率随时间的变化,考虑各结构部件对反应性的影响。计算得到的稳态电功率输出与TITAM程序的计算结果较为一致,反应堆系统热电转换效率为5.04%。计算结果验证了所开发的RESYS程序以及建立的TOPAZ-Ⅱ系统模型的正确性。

A versatile reactor system analysis code RESYS for advanced nuclear reactor was developed by using object-oriented language C++.Based on RESYS code,the model of thermionic nuclear reactor TOPAZ-Ⅱdeveloped in the former Soviet Union was established,and its start-up process was simulated.The established TOPAZ-Ⅱreactor system model included reactor core thermal model,thermionic conversion system model and the radiator model.The current density model of cesium thermionic converter used model by Rasor.And the 6 groups of delayed neutron point reactor kinetic model was used to consider the influence of various structural components on reactivity.The point reactor equation with strong rigidity was solved using the Gear algorithm in the RESYS code.The reactivity feedback model of TOPAZ-Ⅱreactor took into account the Doppler reactivity feedback of the fuel,the reactivity feedback of the electrodes,the reactivity feedback of the moderator and reflector,and the introduction of reactivity control drums.The steady state and start-up transient were simulated based on established thermal-hydraulic model and RESYS code.At steady state,the maximum temperature on the inner surface of the central thermionic fuel element is 2291 K,the maximum temperature on the outer surface is 2066.55 K,the maximum temperature on the emitter is 1961 K,the maximum temperature difference between the electrodes is close to 1200 K,the temperature at the coolant inlet is 743 K,and the temperature at the core outlet is 837 K.The comparison between the steady-state operating conditions calculated by the RESYS code and the TOPAZ-Ⅱdesign values was carried out.The calculated steady-state electric power output is consistent with the calculation results of TITAM code.The calculation results verify the correctness of the developed RESYS code and the established TOPAZ-Ⅱsystem model.During the startup process,the reactivity feedback of the moderator and reflection layer is positive feedback,which dominates all feedback effects.The overall reactivity feedback of the TOPAZ-Ⅱreactor core is positive and does not have a self-stable negative feedback effect,which increases the difficulty of reactor control.During the start-up process of TFE,due to changes in the gas thermal conductivity of the electrode gap,the temperature of the fuel pellets and emitter rapidly increases.At this time,some of the thermal energy generated by fission is stored in the fuel pellets,causing a decrease in coolant temperature and the power of the radiation radiator.