在临界实验中墙壁对散射中子贡献的计算

为了得到临界实验中临界装置周围的散射中子强度分布特性,以便为减小散射中子对临界测量准确性的影响提供依据,本文采用蒙特卡罗方法,计算了实验大厅内不同位置处来源于墙壁的散射中子强度和份额.计算结果表明:对单一墙壁而言,墙壁对散射中子的贡献随墙壁厚度的增加而增加,但是厚度达到60cm后散射贡献不再明显变化;在实验大厅内,散射中子强度随离开临界中子源距离先是减小然后增加,呈现明显的"W"形状;而散射中子数所占份额随离开源的距离增加变大;墙壁内表面添加一层含硼材料后散射中子强度明显减小.上述结果对于分析和减小临界实验测量中的散射中子影响具有明显的指导意义.

Calculation of scattering neutrons from the concrete walls in critical experiment

In order to provide evidence how the scattering neutron influences the measurement accuracy during the critical experiment, this paper calculates, by using Monte Carlo method, the space distribution of scattering neutron from the walls of laboratory. The calculation shows that the intensity of scattering neutron increases with the thickness of the wall when the wall is less than thickness of 60cm ; that the intensity of scattering neutron increases first and decreases then with distance from the neutron source, showing a W like shape ; that a boron layer added to the wall surface can effectively reduce the neutron scattering intensity.