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目的通过现场测量,对某252Cf中子后装治疗室的实体防护效果和迷路内中子、γ辐射水平分布与变化规律进行分析,积累辐射防护屏蔽实验数据与经验,为职业照射的控制提供科学依据。方法在252Cf中子后装治疗机运行时,分别采用中子周围剂量当量仪和X-γ剂量率仪测量治疗机房实体屏蔽墙外、迷路内各关注点的中子、γ辐射水平,并利用非线性模型对迷路内各关注点的中子、γ辐射水平与所处位置进行回归分析,分析治疗室的实体防护效果和迷路内各关注点的中子、γ辐射水平的变化规律。结果结果表明,252Cf中子后装治疗室实体屏蔽外侧的中子、γ辐射水平处于本底水平。同时,治疗室迷路内中子、γ辐射水平随着与内入口的距离增加呈指数衰减趋势。结论252Cf中子后装治疗室的实体防护效果符合相关辐射防护要求。较长的迷路设置是降低治疗室防护门处剂量负担的一个行之有效方法。
Objective To analyze the physical protective effect of neutrons and gamma radiation in a 252Cf neutron afterloading treatment room and the variation rules of neutron and gamma radiation by field measurement and to accumulate the experimental data and experience of radiation protection shielding to provide scientific control of occupational exposure in accordance with. Methods In the operation of 252Cf neutron afterburner, neutron and γradiation were measured by neutron dosimeter and X-γ dose meter respectively. Nonlinear models were used to analyze the neutron and gamma radiation levels and the locations of the neutrons and gamma rays in each point of concern in the lost track. The effect of physical protection in the treatment room and the changes of the neutron and gamma radiation levels of the concerned points in the lost track were analyzed. The results show that, 252Cf neutron afterloading treatment room solid shielding outside the neutron, γ radiation levels at the background level. In the meantime, neutrons and gamma radiation level in the treatment room labyrinth were exponentially decayed with increasing distance from the inner entrance. Conclusion The physical protection effect of 252Cf neutron afterloading treatment room meets the relevant radiation protection requirements. A longer labyrinthine setting is an effective way to reduce the dose burden at the treatment room door.