海水原位伽马能谱仪稳谱方法研究

Research on Spectrum Stabilization Method of Seawater In-Situ Gamma Spectrometer

基于NaI(Tl)闪烁晶体探测方法的海水原位伽马能谱仪,在实测工作中伽马能谱容易受到环境温度变化的影响产生漂移,给海水放射性核素的活度分析带来困难。目前针对陆地环境伽马能谱仪的稳谱方法通常引入放射性参考源,不适用于海水低水平放射性环境测量。本文采用实验设计和分析方法研究了伽马能谱温度漂移的规律,发现不同特征峰随温度发生的峰位道址漂移比例基本一致,而且峰位道址随温度变化的趋势一致且都存在拐点,低于15℃时峰位道址随温度的升高而增大,高于15℃时峰位道址随温度的升高而减小。在研究和总结海水原位伽马能谱仪的增益与峰位道址的关系基础上,提出了以海水中大量存在的天然放射性核素形成的天然特征峰为参考的海水原位伽马能谱仪稳谱方法。经实验室水体环境实验验证,使用稳谱方法后不同温度条件下测量得到的伽马能谱重合性较好,能谱峰位道址最大漂移道数为-1~+1道。该方法能够有效稳定海水原位伽马能谱仪的温度漂移,满足海上长周期自动运行对实测伽马能谱的要求。

In the process of working,the measured Gamma spectrum of in situ seawater Gamma spectrometer based on NaI(Tl)scintillation crystal detection method is prone to drift under the influence of ambient temperature changes,which brings difficulties to the radionuclides’activity analysis.At present,spectrum stabilization methods for terrestrial environmental Gamma spectrometer usually introduce radioactive reference sources,which are not suitable for the measurement of low-level radioactive environment in seawater.In this paper,experiments are designed to study the rule of temperature drift of Gamma spectrum.It is found that the proportion of peak channel address drift with temperature of different characteristic peaks is basically the same,and the trend of peak channel address change with temperature is the same,and there are inflection points.When the peak channel address is lower than 15℃,it increases with the increase of temperature,while when it is higher than 15℃,it decreases with the increase of temperature.According to the study of the relationship between the gain and the peak channel address of the in situ seawater Gamma-ray spectrometer,a spectrum stabilization method based on the natural characteristic peak of radionuclides in seawater is proposed.The experimental results show that the Gamma-ray spectrum obtained by using the spectral stabilization method have good coincidence under different temperature conditions,and the maximum drift channel number of peak channel address is−1-+1 channel.This method can effectively stabilize the temperature drift of the in situ seawater Gamma spectrometer and meet the requirements of the long-term automatic operation for Gamma spectroscopy measurements in seawater.