基于点截面的快堆组件均匀化参数计算方法

Method of generating homogenized fast reactor assembly constants based on point-wise cross section

快中子反应堆的中子学计算中,少群参数的计算精度直接影响最终的计算精度。通过直接利用点截面的方法产生具体问题的精细群截面,随后进行组件输运计算并以获得的中子通量密度分布归并能群从而得到组件的均匀化少群参数,可以较精确地考虑中等质量核素在中高能量段具有的非常强烈的弹性散射共振效应以及全能量段存在的多核素共振干涉效应等问题。计算结果表明,由点截面产生的细群截面误差均在1%以内,进行能谱计算并利用该能谱归并能群得到少群参数的误差也在1%以内。随着截面精度的改善,最终堆芯计算的精度得到明显提升。

In the fast reactor analysis, one of the most important things is generation of homogenized cross sections starting from the evaluated nuclear data files. By using point-wise cross section directly during the generation of problem dependent ultra- fine group cross section, the treatments of the elastic scattering resonance effect of intermediate atom weight nuclide and the inter- ference effect of all nuclides would be more accurate. Therefore, the neutron spectrum obtained from solving neutron transport e- quation could be more accurate and it would be the weight function for group condensation. Comparing with Monte Carlo continu- ous energy calculation, the results obtained by using point-wise cross section directly show that the relative differences of ultrafine group cross sections and few group cross sections after group condensation are both less that 1%. Consequently, the core analysis could get better results.