Analysis of background variations in low-background γ-ray spectrometer with lead shielding / 中华放射医学与防护杂志

Objective To study the variation in net count rates of natural radionuclides in background of gamma-ray spectrometer,so as to provide a scientific basis for reducing the effect of background fluctuations on sample measurement.Methods The unscheduled background spectrum obtained using two high-purity gamma-ray spectrometers during 2013-2017 were collected,and then the net count rates of 210pb,234Th,212Pb,214pb,208Tl,214Bi,228Ac and 40K were calculated and analyzed by aid of statistical method.Results There was a significant difference in the net count rates of 210Pb,234Th,212Pb,214Pb,208Tl,214Bi,228Ac and 40K in the background spectrum of gamma-ray spectrometer,and the net count rates of 214Pb,214Bi and 40K was significantly higher than those of 210Pb,234Th,212pb,208Tl and 228Ac.There were no significant differences in the net count rates of these eight natural radionuclides from 2013 to 2017,respectively (P ＞ O.05).However,the coefficients of variation in the net count rates for 214pb and 214Bi were both greater than 50％.Conclusions When the activity concentration of natural radionuclides is determined in a sample by gamma-ray spectrometer,it is critical to subtract the background spectrum obtained recently to ensure the accuracy of the measurement,especially for the low activity concentration of natural radionuclide to be measured.

Nationwide intercomparison of 226Ra,232Th and 40K for soil and building material by γ-spectrometry analyses in 2008 / 中华放射医学与防护杂志

Objective To assess the accuracy and precision of γ-spectrometry analysis, and to obtain accurate and valid measurement results in the middle term and long term. Methods A nationwide intercomparison on gamma-ray spectrometry measurement of activity concentration of 226Ra, 232Th and 40K in soil and building material was organized by National Institute for Radiological Protection( NIRP) , China CDC. Results 15 laboratories participated in this intercomparison, with 13 laboratories produced acceptable results. Only 2 laboratories were classified as " not acceptable" , including one for inappropriate accuracy in determination of 40K and another for inappropriate precision determination of 226Ra in both kinds of the samples. Through comment and discussion, the second round intercomparison got satisfactory results. Conclusions The overall measurement results of samples for intercomparison are in close agreement with the reference values. Most of the laboratories involved in the intercomparison have good ability in γ-spectrometry analysis.