铀离心浓缩厂铀丰度在线监测仪本底自动测量方法研究

摘要

铀丰度在线监测仪是对铀浓缩厂工艺管道中UF6气体235U丰度进行在线监测的装置，本底是其核心关键技术指标，直接关系到丰度值的测量精度。原有本底测量方法需监测仪停止工作，人工将容器内的气体抽空进行测量。而本底自动测量方法通过改变测量容器内UF6气体的压力，用NaI(TI)探测器测量容器内UF6气体中235U发射的特征γ射线，利用压力传感器测量容器内UF6气体的压力值，最后对不同压力下的数据进行拟合获得监测仪的本底。实验结果表明，采用本底自动测量方法，监测仪铀丰度在线监测结果的相对标准偏差小于0.30%，与气体质谱计测量结果的最大相对偏差小于0.25%，表明该方法测量本底的准确度高；监测仪本底测量由软件自动完成，提高了监测仪的自动化程度，增强了监测仪的适用性。%Background: Uranium enrichment of on-line monitor (UEOM) is an equipment which is adopted to measure enrichment of UF6 flowing through the processing pipes at uranium enrichment plant. Background is the key parameter which directly influences the measurement precision. Traditional background measurement methods need to stop work of monitor and vacuum container. Purpose: This study aims to build up a method to measure the background of monitor automatically. Methods: A NaI(T1) detector is used to measure the count rates of γ-ray emitted from 235U and a pressure sensor is used to measure the pressure of gases in the container, the background of monitor is obtained by fitting the data of different pressures. Results:The experimental results show that the relative standard deviation is less than 0.30%and the maximum deviation is less than 0.25%comparing with the data from mass spectrometry method. Conclusion:The new method shows a better precision compared with the traditional and it increases automation of the monitor greatly.