核活化法反应计算中的蒙特卡罗模拟

Monte Carlo simulation in the reaction rate's calculation with neutron-activation method

用MCNP／4B程序,对核活化法反应计算中的截断能量、通量计数方式、数据库、阈探测器之间的扰动等因素的影响作了分析。截断能量可选为有效反应阈能,不影响计算结果,但可减少计算时间。栅元通量计数方式稳定可靠,效率高,计算值略高。不同的数据库的计算结果可能有些差别。阈探测器之间的扰动对计算结果的影响很小。

With MCNP/4B code, the influence of cut-off energy, flux tallies, nuclear databases and perturbation on the reaction rate＇s calculation with neutron-activation method are analysed. When the effective reaction threshold is chosen as the cut-off energy, calculation time is considerably reduced and yet the results are not changed. Comparing calculations with cell tallies （F4） with those performed with detector tallies （F5）, the counting efficiency of cell tallies is higher and the results are slightly higher, but still credible. With different nuclear databases, calculated results can be different. The perturbation among the detectors doesn＇t effect on the calculated results.