高能X射线探伤机房屏蔽计算

摘要

Shielding calculations were performed for the room of a linear accelerator of model DZ-12/5500 , with NCRP Report No .151 ,GBZ/T 220 .2—2009 and etc as references ,to illustrate how to select a suitable calculation method to determine the optimal shielding thickness of room for industrial flaw detecting linear ac-celerator of energy above 10 MV .It shows that a 278 cm thick concrete shielding wall is needed in the useful beam direction ,while the concrete thickness in other 3 sides should be 182 ,195 and 204 cm respectively . With a roof of 110 cm thick concrete ,sky inverse scattering results in an extremely small dose equivalent rate in any location 20 m away from the nose of the accelerator .The ambient dose equivalent is 115 .69μSv in the Z-shaped labyrinth entrance ,in which X-ray scattering and leakage ,neutron irradiation ,and neutron capture of X-ray give rise to 2 .43 ,102 .96 and 10 .30 μSv/week respectively .Analysis of test results upon operation indicates that calculated and tested values agree well ,our calculation method and parameters selected are via-ble .%目的：选用一个合适的计算方法对X射线能量大于10 MV的工业探伤用直线加速器机房进行屏蔽计算，确定屏蔽厚度。方法以一台DZ-12/5500型工业探伤用直线加速器机房为研究对象，参考NCRP 151号报告、GBZ/T 220．2—2009等资料中提供的计算方法进行计算和分析。结果该加速器机房有用线束方向混凝土屏蔽墙厚度需278 cm ，其它三面墙分别需要182、195、204 cm；顶盖厚度为110 cm混凝土时，天空反散射在距机头20 m处造成的剂量当量率非常小；“Z”字型迷道入口处总周剂量当量为115．69μSv ，其中X射线的散射和泄漏辐射总剂量当量为2．43μSv/周，中子辐射剂量当量为102．96μSv/周，中子俘获γ射线剂量当量为10．30μSv/周。结论对实际建成运行的机房检测结果的分析后发现，上述计算值与检测值比较吻合，说明本文选用的计算方法和选取的参数可行。