基于FLUENT 的UDS和UDF功能的中子扩散耦合计算研究与快堆应用分析

Research on neutron diffusion coupling calculation based on the UDS and UDF functions of FLUENT and its application analysis on fast reactor

摘要:

随着计算机性能的不断提高，用CFD与中子学相结合的方法分析复杂的流动与传热现象引起了人们的广泛关注. 本文基于FLUENT的UDF(User Defined function)和UDS(User Defined Scalar)功能对中子扩散方程进行定义，利用FLUENT内基于有限容积法的求解器对中子扩散方程进行迭代求解，同时耦合质量，动量，能量方程的迭代求解，在每次迭代计算时，将中子扩散方程迭代计算得到的功率分布（中子通量分布）传递给热工水力计算作为热源项，同时将热工水力计算得到的温度分布传递给中子扩散计算，修正材料的宏观反应截面，实现中子扩散和热工水力在同一求解器和同一套网格下的耦合计算. 通过对5×5压水堆组件模型进行建模和计算，将计算结果与其他程序计算结果进行对比，验证该耦合计算方法的可行性和数据传递的正确性. 然后将该耦合方法应用到模块化铅冷快堆(M2LFR-1000)热组件计算中，证明热工水力学参数(燃料最高温度，包壳外表面最高温度)在设计限值范围内.

Abstract:

With the great improvement of computer performance, analyzing the complex flow and heat transfer phenomenon by coupling CFD and neutronics has attracted lots of attentions nowadays. The study aims to investigate the neutron diffusion coupling calculation based on the UDF and UDS functions of FLUENT and its application analysis on fast reactor. The neutron diffusion equation is defined based on the UDF (User Defined function) and UDS (User Defined Scalar) functions of the FLUENT. The neutron diffusion equation is solved iteratively by using the solver of the FLUENT based on the finite volume method. At the same time, the mass, momentum and energy equations are solved iteratively. At each iteration, the power distribution (neutron flux distribution) obtained by the iteration of the neutron diffusion equation is transferred to the thermal-hydraulics calculation and is used as the heat source term. At the same time, the temperature distribution obtained from the thermal-hydraulics calculation is transferred to the neutron diffusion calculation and the macroscopic cross sections of the materials are corrected to realize the coupling calculation of the neutron diffusion and the thermal-hydraulics under the same solver of the FLUENT. Through the modeling and calculation of the 5×5 PWR assembly model and the hot assembly of a modular lead-cooled fast reactor (M2LFR-1000). It is proved that this method is feasible to realize the neutron diffusion and thermal-hydraulics coupling and the data transfer is correct. And the thermal hydraulics characteristics (the maximum fuel temperature and the maximum cladding outer surface temperature) of the M2LFR-1000 are all within the corresponding thermal‐hydraulics design limits.