基于共轭通量的蒙特卡罗临界硼浓度搜索方法

Monte Carlo critical boron concentration search method based on adjoint flux

临界硼浓度搜索是反应堆设计和物理分析的重要组成部分。本文针对传统搜索方法需要多次临界计算、效率低的问题,发展了一种基于共轭通量的蒙特卡罗临界硼浓度搜索方法。该方法将临界硼浓度搜索视为微扰问题,采用共轭通量法进行微扰计算,并在蒙特卡罗模拟中使用反复裂变几率法计算共轭通量,只需对系统进行一次临界计算,就可以得到系统初始的共轭通量以及有效增殖因子对硼浓度变化的响应系数,使用该响应系数可直接计算得到系统临界硼浓度。西屋公司标准17×17组件模型的数值验证结果表明:本文方法可以有效应用于临界硼浓度搜索。

[Background] Critical boron concentration search is considered as an important part of reactor design and analysis, but traditional search method requires multiple criticality calculations, hence low efficiency. [Purpose] In order to overcome the disadvantages of the traditional search method, a highly efficient Monte Carlo critical boron concentration search method is developed and verified. [Methods] First of all, the critical boron concentration search is treated as a perturbation problem. Then the adjoint flux method is adopted for perturbation calculation whilst the adjoint flux is calculated by the iterated fission probability method in the Monte Carlo simulation. The adjoint flux and the effective multiplication factor on the boron concentration response coefficients of the initial state can be obtained by only one criticality calculation, and the critical boron concentration is directly derived from the response coefficients. Finally verification is made on the standard Westinghouse 17×17 assembly model. [Results] The numerical results of verification show a good agreement with reference results. [Conclusion] This method can be effectively applied to critical boron concentration search.