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铅铋堆瞬态安全分析程序MPC_LBE换热器模块开发

Development of a Heat Exchanger Module for a Transient Safety Analysis MPC_LBE Program for Lead-bismuth Reactors

  • 摘要: 铅铋堆作为第四代先进核能系统之一,具有优良的中子经济性、固有安全性。为提高其紧凑性、安全性,铅铋堆主冷却剂系统倾向于采用一体化池式结构设计理念,但该设计理念同时也造成了复杂的热工水力问题。铅铋堆多物理耦合瞬态安全分析程序MPC_LBE在此背景下开发,但该程序的换热器模块采用了定温简化模型,无法模拟换热器一、二次侧之间的换热过程,事故瞬态模拟过于保守,偏离实际工况。为此,开展了铅铋堆换热器模块数值模拟方法研究,换热器一次侧、管壁以及二次侧均采用了一维通道等效处理手段,构建了其数值传热模型,编制了程序代码,并与MPC_LBE实现了外部显式耦合。对于该数值传热模型,单独进行了稳态验证及时间步长敏感性分析,结果显示,显式耦合策略的时间步长敏感性较大,而隐式耦合策略时间步长设置对模拟结果几乎无影响。对耦合了该数值传热模型的新MPC_LBE程序,开展了自然循环铅铋反应堆稳态模拟应用,同时添加了以一次侧出口段的设计温度为基准的二次侧冷却剂流量调节系统。

     

    Abstract: As one of the fourth-generation advanced nuclear energy systems, Lead-Bismuth Eutectic(LBE) cooled reactor has excellent neutron economy and inherent safety. To improve its compactness and safety, the main coolant system of LBE-cooled reactor tends to adopt the integrated pool structure design concept, but this design concept also introduces complex thermal hydraulic problems. To solve the above issues, the multi-physics coupling transient safety analysis code for LBE-cooled reactor MPC_LBE was developed, but this code uses a constant temperature simplified model which are not able to simulate the heat exchange process between the first and second circuits, and the accident transient simulation is rather conservative which deviating from the actual condition. To solve this problem, the numerical simulation method of the heat exchanger module for LBE-cooled reactor was carried out in this paper. A one-dimensional numerical calculation models were employed for the primary side, pipe wall and secondary side of heat exchanger, and the numerical heat transfer model was constructed. Finally, the heat exchanger module was coupled with the MPC_LBE code by external explicit means. For the heat exchanger numerical calculation module, steady-state verification and time step sensitivity analysis were performed separately, and the results show that the time step sensitivity of the explicit coupling strategy is large, while the time step setting of the implicit coupling strategy has almost no effect on the simulation results. For the new MPC_LBE program coupled with the numerical calculation module of the heat exchanger, the steady-state simulation application of the natural cycle lead-bismuth reactor was carried out.

     

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