摘要
为建立一种准确实用的环境γ谱仪对大气中放射性核素活度浓度响应系数的测量方法,构建活度浓度响应系数理论估算模型,并基于探测效率空间分布的两条假设,推导出两种简化估算模型。蒙特卡罗方法模拟结果显示:模拟结果与实验室测量结果相符,在所有测量点位两者差异均小于6%;对于一款典型Na Iγ谱仪,采用两种简化估算模型引入的误差分别不超过0.1%和10%。现场测试结果显示:该方法现场适用性良好,两台环境γ谱仪对大气中^(137)Cs的活度浓度响应系数分别为6.49 min^(-1)·Bq^(-1)·m^3和2.62 min^(-1)·Bq^(-1)·m^3。
[Background] In the last decade, a large number of environmental gamma spectrometers have been installed to monitor ambient radionuclide in the environmental radiation monitoring stations in China. However, the response coefficients to airborne radionuclide concentration of most facilities were unknown. [Purpose] This study aims to establish an accurate and practical method for determining the response coefficient to airborne radionuclide concentration of the environmental gamma spectrometers. [Methods] Based on two assumptions on the spatial distribution of the facility＇s detection efficiency, a theoretical model was proposed and simplified. Subsequently. Monte Carlo simulation method was utilized to analyze the deviation contributed by the two assumptions for several common radionuclides quantitatively. Simultaneously, the detection efficiency spatial distribution of a self-developed gamma spectrometer which consists of a typical Na I（Tl） crystal（76.2 mm×76.2 mm） was measured in an ^137 Cs expose experiment to verify the accuracy of Monte Carlo simulation method. Lastly, the method for determining the response coefficient was established by using the simplified theoretical model, and applied to two environmental gamma spectrometers in field. [Results] The relative difference between the experimental and simulated detection efficiency of the self-developed gamma spectrometer was less than 6% at every measurement position. According to the Monte Carlo simulation results of the typical gamma spectrometer, relative deviations of response coefficients to several common airborne radionuclides contributed by the two assumptions were less than 0.1% and 10% respectively. In the field test, the changing trend of the detection efficiency was similar to the simulated results, and the response coefficients to airborne ^137 Cs of the two facilities were 6.49 min^-1·Bq^-1·m^3 and 2.62 min^-1·Bq^-1·m^3 respectively. [Conclusion] The results of Monte Carlo simulation indicated that the simplified model was acceptable for environmental radiation monitoring field, and the applicability of this method had been validated through field test.
作者
何林锋
唐方东
赵超
HE Linfeng;TANG Fangdong;ZHAO Chao(Shanghai Institute of Measurement and Testing Technology,Shanghai 201203,China)
出处
《核技术》
CAS
CSCD
北大核心
2018年第8期27-33,共7页
Nuclear Techniques
基金
上海市科学技术委员会科研计划项目(No.16DZ2292300)
上海市质量技术监督局科技计划项目(No.2015-ZX001)资助~~
关键词
环境γ谱仪
活度浓度响应系数
蒙特卡罗模拟
Environmental gamma spectrometer
Response coefficient to activity concentration
Monte Carlosimulation
