非均匀变分节块法

Heterogeneous Variational Nodal Method

  • 摘要: 传统的节块方法均属于均匀节块法,要求节块内的材料必须是均匀分布的。对于传统的固体燃料核反应堆,该近似处理带来的误差是可接受的;但对于液体燃料的熔盐堆,流动的燃料由于空间上连续变化的温度和核密度分布而具有连续变化的宏观截面,使传统的节块方法无法在保证计算精度的同时取得较高的效率。为尝试解决该问题,本文在一维扩散近似的情况下,基于变分节块法推导了能处理空间连续变化截面的非均匀变分节块法,并开发了相应的计算程序Violet-Het1D。数值结果表明,在相同的节块划分和展开阶数条件下,非均匀变分节块法和均匀变分节块法计算时间相当,但前者的计算精度高于后者。

     

    Abstract: Traditional nodal methods all belong to homogeneous nodal method which requires homogeneous cross section in each node. The error introduced by the approximation of homogeneity can be accepted in solid nuclear fuel reactors. However, in molten salt reactor (MSR), the fluid fuel has continuous changing cross sections caused by the continuous temperature and nuclide density distributions which makes it difficult for traditional nodal method to obtain both high accuracy and efficiency. To solve this problem, the variational nodal method was generalized for heterogeneous node with diffusion approximation to handle continuous cross section in one dimensional slab geometry, and the code Violet-Het1D was developed. Numerical results show that with the same number of node and expansion order, the heterogeneous variational nodal method obtains higher accuracy than homogeneous variational nodal method without decreasing the efficiency.

     

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