The Test And Comparison Of Four Aerosol Sample Preparation Methods In γ-ray Spectrometer Analyze In Radiation Monitoring

An important task in environmental radiation surveillance is the use of gamma spectroscopy in the analysis of aerosol samples that are prepared with four common sample preparation methods:the ashing method, compressing method, holing method, and folding method. Presently, in domestic and overseas literature there is little information about specific studies of these sample preparation methods, resulting in a lack of reference data when preparing for aerosol samples. This study aims to provide a comprehensive evaluation of the reliability, the detection efficiency, the detection limit and the applicable scope of these four methods. First, an HPGe (High Purity Germanium) gamma spectrometer was used to evaluate and confirm the reliability using naturally-occurring 210Pb and 7Be radioisotopes as the measurement subjects. These four preparation methods were found to be generally reliable, with the error in radioactivity of 7Be and 210Pb being within ±6% and±9%, respectively, and with the assessed radioactivity differing less than 5% from same activity samples. Second, methods of experimental measurement and Monte Carlo simulation were used to calculate the gamma-spectroscopic counting efficiency for these four sample preparation methods. The results showed that, the ashing method yielded the highest counting efficiency, followed by the compressing method, holing method, and folding method. The variation range of gamma detection efficiency of the four methods was found to be 55% and 120% for the 260mm×210mm and 570mm×470mm sized filters, respectively. Furthermore, for the 260mm×210mm sized filter, the variation of detection efficiency with holing diameter (50mn、60mm、65mnu、75mm) was simulated. It turned out that, the efficiency reached the maximum when the holing size was approximately the same as the HPGe detector diameter. To consider the effect of sample height on detection efficiency for the 570mm×470mm sized filter, different sample heights were simulated. Third, taking the interested nuclide 137Cs in nuclear accidents as an example, the minimum detectable activity of the four methods were analyzed and compared. Last, suggestions on different technical levels about the suitability and conditions of these sample preparation methods were provided as a useful reference on how to choose, prepare and count radioactive aerosols samples.