剂量率参考控制水平对加速器屏蔽设计的影响

Influence of dose rate reference control level on the design of accelerator shielding

目的 探讨剂量率参考控制水平对加速器屏蔽设计的影响.方法 根据GBZ 126-2011、GBZ/T 201.1-2007、GBZ/T 201.2-2011中关于加速器机房辐射屏蔽的要求,分别采用剂量率参考控制水平计算方法和周剂量控制水平计算方法对加速器机房的主屏蔽进行计算,并对计算的屏蔽厚度进行比较.结果 在周最大工作负荷相同的情况下,当计算的剂量率参考控制值大于剂量参考控制水平2.5 μSv/h时,计算结果会出现差异,屏蔽厚度差值最大达64 cm.15 MV能量的屏蔽厚度差值大于6 MV.同时,考虑了剂量率参考控制水平的情况下,加速器剂量率不同,所计算的机房的屏蔽厚度也不同.结论 在屏蔽计算时,首先要估算参考点的剂量率,满足剂量率参考控制水平的条件下再进行计算.

Objective To explore the influence of dose rate reference control level on the design of accelerator shielding.Methods According to the standards of GBZ 126-2011,GBZ/T 201.1-2007 and GBZ/T 201.2-2011,two different shielding calculation methods,based on the dose rate reference control level and week dose control level,were used to calculate and compare the thickness of accelerator room shielding.Results Under the same condition of maximum weekly workload,the obtained results were different when the calculated dose rate reference control value was larger than dose rate reference control level （2.5 μSv/h）.The maximum difference of shielding thickness reached 64 cm.Meanwhile,considering dose rate reference control level,the different accelerator rates could lead to different radiation shielding thickness.Conclusions The dose rate at reference point must be first calculated before calculating shielding thickness.The calculation should be made on the premise that dose rate reference control level is met.