考虑有效共振积分不确定度的抽样方法研究

在核反应堆物理计算中,核数据库中的截面是影响计算结果的重要因素,研究其不确定度对结果的影响具有重要意义。本文基于3个核评价数据库,利用NJOY程序制作了70种主要锕系核素和部分裂变产物的69群协方差数据库。开发了不确定性分析程序SUACL,该程序利用上述协方差数据库和国际原子能机构制作的69群WIMSD数据库,基于随机抽样的方法产生微扰后的多个核数据库样本;然后利用DRAGON程序对NEA/OECD基准中的PWR栅元进行了计算,计算结果表明,~(235)U和~(238)U两种核素裂变-裂变、辐射俘获-辐射俘获和弹性散射-弹性散射参数对对栅元k∞的相对不确定度与其他程序的吻合良好,验证了程序和理论方法的正确性。同时利用随机抽样方法对5个制作参数的不确定度进行了研究,发现包壳厚度的不确定性对无限增殖因数有较大影响,主要原因是其本身的相对不确定度较大。

Uncertainty Analysis by Concerning Effective Resonance Integral Based on Sampling Method

The cross section is the important uncertainty source of the reactor physics calculation. It is of great significance to study the contribution of its uncertainty to the simulation results. Based on three nuclear evaluation data libraries, the 69 groups covariance library containing 70 kinds of main actinium nuclides and part of the fission products was generated using the NOJY code. The uncertainty analysis code SUACL was developed. The perturbed nuclear evaluation data libraries were generated using random sampling method based on the covariance library SUACL1.0/NCEPU developed by NJOY and 69 groups WIMSD library which can be downloaded from IAEA website. The PWR cell of NEA/OECD benchmark analysis was performed using perturbed nuclear evaluation data library and SUACL code. The result shows that the parameter pair of fission cross section, capture cross section and elastic scattering cross section for ²³⁵U and ²³⁸U contributed to the uncertainty of k_∞ agrees with that calculated by other well-known code, and the theoretical method is right and the SUACL code is developed correctly. The manufacturing parameters were also discussed based on random sampling method. The result indicates that the uncertainty of clad thickness has large effect on k_∞ because of its own large uncertainty.