环境γ辐射剂量率仪现场校准用辐照装置的研制

Development of an irradiation device for on-site calibration of environmental gamma radiation dose rate meter

为开展环境γ辐射剂量仪的现场校准,研制了一套辐照装置,其辐射场空气比释动能率可在0.27-34.86μGy·h^(-1)范围内通过距离与减弱器来调节。基于大量Geant4蒙特卡罗模拟设计了一种轻便型辐射准直器,在保证辐射场品质的前提下,大大降低了准直器重量,更适用于现场校准。此外,还研制了一套自动化支撑平台与三片曲面辐射减弱器,可远程实现辐射装置空间定位以及辐射场强度和空间的调节,曲面辐射减弱器有利于保证辐射场均匀性。测试实验及蒙特卡罗模拟结果显示,该辐射装置辐射场再现性、自散射、均匀性等性能良好,通过系统地计算地面散射对辐射场的影响,可为现场校准提供指导。

Background： With the development of the nuclear safety technology in China, more and more environmental gamma radiation dose rate meters were fixed in the field to monitor the environmental radiation in real time. Calibration of these meters is inconvenient to do on-site. Purpose： This study aims to design and implement a portable irradiation device for on-site calibration of these dose rate meters. Methods： An irradiation collimator was designed through Monte Carlo simulation as the kernel component of the irradiation device, and an automated supporting platform with functionalities of ranging, shifting, switching attenuation plates and remote control of intensity and position was developed as the additional component. Experiments and Monte Carlo simulations were conducted to test the performance of the irradiation device and calibrate the air kerma rate in the radiation filed of it. Field-testing was also performed to check the practicability of this irradiation device on condition of on-site calibration. Results： The adjustable range of the air kerma rate in the reference radiation filed was 0.27-34.86 tGy.h-a. The self-developed irradiation device had good performance on reproducibility, self-scattering,homogeneity and practicability in field application. Conclusions： A portable irradiation device was designed and developed through Monte Carlo simulation for the calibration of on-site dose rate meter, it can be nsed to achieve the traceability of the fixed environmental gamma radiation dose rate meter.