He jishu (Oct 2021)
Optimal selection of sampling filter membranes for alpha radioactive aerosols based on spectrum tailing and detection efficiency tests
Abstract
BackgroundSampling filter membrane is an important part of the continuous monitoring system for radioactive aerosols. The performance of the sampling filter membrane directly affects detection efficiency of the system. In addition, tailing effect in α spectra increases the difficulty of identifying nuclides, reduces the accuracy of aerosol measurement, and elevates the minimum detectable activity.PurposeThis study aims to find a sampling filter membrane with high detection efficiency, small α spectrum tailing and the pore size suitable for actual environmental measurement.MethodsThe detection efficiency and spectrum tailing performance of the three most commonly used filter membranes at present, i.e., mixed cellulose ester membrane (MCEM), hydrophobic polytetrafluoroethylene (PTFE) and polypropylene (PP) filter membranes, were tested under different radon concentrations and various pore sizes. Then, based on obtained data of the tests, the comprehensive evaluation was performed on their adsorption performances to determine the optimal sampling filter membrane.ResultsThe results show that the MCEM filter membrane has the highest detection efficiency and the hydrophobic PTFE filter membrane has the least tailing effect in the three kinds of filter membranes. In comparison of other pore sizes under different radon concentrations, the MCEM filter membrane or hydrophobic PTFE filter membrane has the highest detection efficiency when its pore size is 0.45 µm, which is close to the maximum particle size of natural radioactive aerosols. No obvious effect of the pore size of the filter membrane is observed on the α spectrum tailing. In addition, for one filter membrane with the same pore size, the detection efficiency decreases with the increase of aerosol concentration and vice versa.ConclusionsThis study provides a useful reference for the optimal selection of filter membranes for natural radioactive aerosols under various conditions.
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