蒙卡燃耗中的氙振荡现象分析及计算研究

Xenon oscillation analysis in Monte Carlo burnup calculation

根据氙振荡产生的机理,按照燃耗步长来划分:在短步长条件下会产生物理氙振荡,在长步长条件下会产生数值氙振荡。研究发现,当燃耗步长增大到19h,物理氙振荡的振幅最小,随着燃耗步长继续增大,表现为数值氙振荡,当燃耗步长27d,数值氙振荡振幅最小。采用平衡氙方法强制使中子通量与氙浓度平衡,在堆芯物理计算程序(RMC)的输运模块中运用平衡氙方法对碘氙的浓度进行不断的迭代更新,在保证收敛的情况下抑制了氙振荡现象的发生。

Burnup calculation is one of the corecontents in physical analysis of nuclearre actors.In Monte Carlo burnupcal culation,power oscillation might occur periodically in certain geometrical dimension and certain step length,namely xenon oscillation.Xenon oscillations might result in a serious deviation from the actual situation.The fundamental reason for the xenon oscil lation is that the neutron flux and xenon concentration in the regions of burn-up do not match.According to the mechanism of xenon oscillation,we classify xenon oscillations as physical xenon oscillations produced in short step conditions and numerical xenon oscillations produced in long time step conditions.Balanced xenon oscillation suppression method is forced to balance neutron flux with xenon concentration.In the RMC transport the article uses module a balanced xenon method for the calculation of iodine and xenon.In the RMC transpor tmodule,th eequilibrium xenon method was used to continuously update the concentration of iodine and xenon.In the case of convergence,the occurrence of xenon oscillation is suppressed.