开环式氡析出率连续测量中抽气流率的影响

摘要

Background: The research on radon exhalation rate mainly focuses on the influence factors of radon exhalation rate on the media surface, while research is still lacking with respect to equilibrium radon concentrations in radon cover sets, gas flow rate and other factors affecting the measurement accuracy of radon exhalation rate. Purpose: This study aimed to explore the relationship of the open-loop air-bleed rate, equilibrium radon concentrations and radon exhalation rate through theoretical calculations and actual measurements. Methods:MATLAB was used to simulate the variations of radon concentrations with time at different air-bleed rates during the open-loop measurement of radon exhalation rate in radon cover sets. The results were further proven by experiments. Results: In the case of constant parameters in radon cover sets in the measurement of radon exhalation rate, the equilibrium concentrations of radon decreased with the increase of air-bleed rates, and the time to reach the equilibrium concentrations was also shortened. The decrease of equilibrium concentrations of radon minimized the effect of the leakage and counter diffusion. The increase of air-bleed rates shortened the time for radon concentrations to reach equilibrium with better inlet gas uniformity in the radon cover sets. Conclusion:Reasonable parameters were obtained in this experiment with 1.94−3.0 L·min−1 for air-bleed rates, 299 cm2 for basal area and 1.79×10−3 m3 for the volume of radon cover sets.%应用MATLAB对开环式氡析出率测量过程中不同抽气流率下集氡罩内氡浓度随时间的变化规律进行模拟计算，并用实验对计算结果进行了验证。结果表明，在氡析出率测量时保持集氡罩参数不变的情况下，随着抽气流率的增大，集氡罩内平衡氡浓度值减小，达到平衡氡浓度的时间也缩短。实验表明，集氡罩内的平衡氡浓度的减小可最大限度地减小泄露与反扩散的影响；抽气流率的变大使集氡罩内达到平衡氡浓度时间缩短以及集氡罩内的充气均匀性愈好。通过本次实验，获得的抽气流率为1.94−3.0 L·min−1，集氡罩底面积为299 cm2，体积为1.79×10−3 m3。