中文摘要：

点通量估计方法广泛应用于探测区域远小于系统的模型。对于平行面源，MCNP5计算源粒子的直穿贡献部分的代码有错误，导致点通量计算结果与体通量计算结果差异较大。此外，MCNP程序（包括MCNP5和MCNP4C）对平行面源的直穿贡献进行多次重复计算，浪费计算资源，本文通过对算法进行改进，使计算时间大幅缩短。

英文摘要：

Point detector flux estimation method is widely applied in the model that volume of detected region is far smaller than that of system. Because of some bug in MCNP5 code on calculating the direct contribution from mono-directional surface source, the result of point detector flux usually differs from that of cell flux. Moreover, the direct contribution of mono-directional surface source is computed repeatedly in MCNP program which includes MCNP5 and MCNP4C, so the computation efficiency is very low. A simplified method was introduced in this paper, and the efficiency is greatly increased.