放射性同位素伽玛源准直照射辐射场模拟研究

Simulation of radiation field from isotopic gamma source collimation

针对各向同性伽玛源参考辐射场尺寸关键技术问题,GB/T 12162系列标准虽然进行了相关规定,但是该规定并未对准直照射状态下照射室尺寸提出具体要求。为减小用于辐射检测或监测类仪器仪表检定与量值校准时伽玛参考辐射场内散射影响,本文采用蒙特卡罗方法,研究了同位素放射源准直照射时,照射室尺寸变化对检验点处的剂量率值与能量分布的影响情况,获得了准直照射时伽玛辐射场照射室尺寸的边界条件,建立并完善了伽玛参考辐射场边界研究方法及相关标准细节,为准直照射状态下照射室尺寸设计提供了一种新方法或途径。

Aiming at the key technical issues of the reference radiation field size of isotropic sources,GB/T 12162 series of GB standards stipulates the size of the reference radiation field when using an isotropic source.However,there is no specific regulation for the size of the irradiation under collimation.To reduce the influence of scattering in the gamma reference radiation field when used for radiation detection or monitoring instrument verification and value calibration,Monte Carlo simulation was carried out to explore the effect of the size change of the irradiation chamber on the energy distribution and dose rate value during the radiation source collimation.The boundary conditions of the collimated gamma radiation irradiation chamber were obtained,and the details of the gamma reference radiation field boundary research method and related standards are established and improved.The study provides a new method or approach for the size design of the irradiation chamber under the collimated irradiation state.