一、方法简介用离散坐标法求解一维、二维多群定常输运方程的过程中采取下列措施。为解决角通量外推时出现负值的问题,使用了几种差分格式:在一般情况下用菱形外推,出现负值时置零并用平衡方程修正(菱形格式),或出现负值时用阶梯外推(出负阶梯格式);计算中始终用阶梯外推(全阶梯格式);在空间和角度上各以某一权量进行外推,使角通量为正(变权1格式);在角度方向用菱形外推,只在空间上选取权(变权2格式),若变权2格式的求权过程忽略源项则称变权3格式。 First, the method profile Discrete coordinate method to solve one-dimensional, two-dimensional multi-group constant transport equations in the process to take the following measures. To solve the problem of negative extrapolation of angular fluxes, several differencing schemes are used: extrapolation with diamonds in general, zeroes with negative values ​​and correction with a balance equation (diamond format), or negative values Extrapolate with ladders (take negative ladders); always extrapolate with ladders (full ladders); extrapolate both by space and by angles with a certain amount of power, making the angle flux positive (variable weight 1 format ); Extrapolated in the direction of the diamond, only the right to select the space (variable weight 2 format), if the weight 2 format of the right to ignore the source of the project is said to change the weight 3 format.