向后微分公式在六角形几何物理-热工耦合上的应用

Application of Backward Differentiation Formula on the Coupling of the Neutron and Thermal-Hydraulics in the Hexagonal Geometry

针对六角形几何物理-热工耦合求解问题,提出了一种二阶变步长向后微分公式,物理和热工采用相同的步长和时间离散格式,并利用变步长技巧,提高计算效率。物理-热工采用模块化方式耦合,物理模块采用基于六角形几何的节块法,热工采用子通道程序,2个模块之间的数据传递通过共享内存的方式实现,开发了基于向后微分公式的HEXCOB-BDF程序。利用两个VVER堆芯弹棒事故验证该方法在物理-热工耦合上的准确性和计算效率。计算结果表明,HEXCOB-BDF程序与KIKO3D,DYN3D,PARCS计算结果相符,同时计算时间约为隐式Euler法计算时间的1/4。表明本文算法具有较好的准确性和较高的计算效率,可为六角形几何物理-热工耦合求解提供参考。

A second order variable time step backward differentiation formula is proposed to solve the transient coupling system of the neutron kinetics and thermal-hydraulics in the hexagonal geometry.The neutronics and thermal-hydraulics adopt the same time step and time discrete format,and use the variable time step technique to improve the computational efficiency.The coupling system is programmed in the modular way.The neutron kinetic is solved by the nodal method for the hexagonal geometry,and the thermal-hydraulic part is solved by the sub-channel code.The data is communicated between these two parts in the shared-memory way.These two parts adopt the same time step and are discretized in the time direction with the same scheme,i.e.the backward differentiation formula.The variable time step technique is also used to improve the efficiency of the calculation.The two examples of control-rod ejected accident for the VVER reactor are used to verify the accuracy and the efficiency of this method.The results given by this method are in good agreement with the results given by the reference codes.