电子加速器屏蔽室空间散射的蒙特卡罗计算

Monte Carlo Method for Calculating the Skyshine of Electron Accelerator Shielding Room

为解决电子直线加速器屏蔽室的空间散射计算相关问题 ,采用蒙特卡罗程序MCNP4B进行模拟 ,使用分步计算的方法 ,结合分裂和轮盘赌技巧 ,计算出 9MeV驻波直线加速器运行时的空间散射剂量率大小 .并实际测量了加速器运行时屏蔽室周围距地面上方 1m处的空间散射剂量分布 .将计算得到的结果、计算空间散射的经验公式结果和实际测量的结果三者进行了比较分析 .结果表明 :蒙特卡罗方法计算值比较符合实际测量值 ,经验公式计算值则存在一定的偏差 .

Using the Monte Carlo code MCNP4B, skyshine of 9MeV electron linear accelerator was calculated with a multi-step method combining the split and roulette variance reduction technique. Dose distribution of the skyshine was measured around the accelerator room. Results of the Monte Carlo simulation, empirical formulas and dosimetric measurement were compared and analyzed. In conclusion, the dosimetric measurement agrees with the results computed by Monte Carlo method reasonably, but deviates with computational results from empirical formulas. It shows that Monte Carlo method is a good way to analyze skyshine.