252Cf中子后装治疗室辐射防护的测量与分析

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。

Measurement and Analysis on Radiation Protection of A 252Cf neutron Afterloading Radiotherapy Room

Objective To analyze the entity protective effect of ²⁵²Cf neutron afterloading radiotherapy room as well as distribution and changing rule of neutron, γ radiation level in the maze, and to accumulate experimental data and experience of radiation protection as well as to provide a scientific basis for the control of occupational exposure by field measurement. Methods When the ²⁵²Cf neutron afterloader was on operation, neutron, γ radiation level at concerned points outside entity shielding wall and inside the maze were measured by neutron ambient dose meter and X-γ dose rate meter, respectively. Besides, the law among neutron, γ radiation level and location of concerned points were analyzed based on the nonlinear regression model, the entity protective effect of the radiotherapy room as well as the changing rule of neutron, γ radiation level at concerned points in the maze were also studied. Results The result shows that the neutron, γ radiation level outside the shield of ²⁵²Cf neutron afterloading radiotherapy room were around the background level. Meanwhile, neutron, γ radiation level in the radiotherapy room shows exponential decay trend with the increase of the distance to the entrance. Conclusion The protective effect of the ²⁵²Cf neutron afterloading radiotherapy room meets the relevant requirements. Long maze setting is an effective way to lower the radiation dose at the radiotherapy room door.