适用于任意几何的特征线边界条件处理方法
Boundary Condition Processing Method for MOC Calculation in Arbitrary Geometry
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摘要: 边界条件处理是特征线方法（MOC）向任意三维几何拓展时遇到的难点之一。本文提出一种边界条件处理方法，既保留循环特征线中首尾相连的特性，又能像插值方法一样适用于任意几何。首先推导了平源近似下的特征线方程，提出了一种将源项和边界角通量分离处理的内迭代解法。然后证明了该解法具有唯一解，并类似于循环特征线方法给出解的构造方法。最后借助数值积分和权重插值给出迭代计算流程。采用Takeda算例、单铀球水腔模型和C5G7算例进行验证计算，keff的最大计算误差分别为21、319和138.8 pcm，表明方法可靠。该方法可应用于任意几何，且不需存储边界通量和进行边界迭代。Abstract: Boundary condition processing is one of the difficulties encountered in the application of method of characteristics (MOC) to arbitrary three-dimensional geometry. In this paper, a boundary condition processing method was proposed, which not only preserved the track continuity as cyclic track method, but also could be applied to arbitrary geometry as the interpolation method. The MOC equation was derived under the flat source approximation and an internal iterative method was proposed in which the source term and the boundary angular flux were processed separately. It was proved that the equation had a unique solution which could be constructed similarly to the cyclic track method. The iterative calculation flow was given by numerical integration and weight interpolation. Takeda benchmark, single uranium sphere model with water cavity and C5G7 benchmark were calculated to test the accuracy. The maximum error of keff is 21, 319 and 138.8 pcm respectively, which shows that the method is reliable. This method can be applied to arbitrary geometry without storing boundary fluxes and performing boundary iteration.
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