Gross α/β Analysis of IAEA 2008 World-Wide Open Proficiency Test on Determination of Natural

In order to evaluate the analysis and determination technique of naturally occurring radioisotopes in our lab for environmental samples, we participated in the IAEA 2008 world-wide open proficiency test on the determination of natural radionuclides in phosphogypsum and spiked water. This paper mainly focuses on the gross α/β analysis in spiked water. According to the requirement of IAEA, Sample03, Sample04 and Sample05 were tested for the gross α/β radioactivity. Comparative determination method was chosen, and UO₂(NO₃)₂ and KCl were selected as sub-standard and standard reference substances for gross α analysis and gross β analysis, respectively, by determining radioactivity with MPC 9604 ultra low level α/β counter. The feedback statistics from IAEA final report show that the values of gross α/β of all of the three samples fell in the acceptable range of IAEA. The influence factors of gross α/β analysis such as the sensitivity of the α/β counter, the selection of standard reference substances and how to monitor the background and efficiency for daily determination and so on were also discussed. The results indicate that when one selected O₂(NO₃)₂ as sub-tandard reference substance for gross α analysis, the total α activity of O₂(NO₃)₂ is much lower than that of standard U₃O₈ which is recommended by B 5750—85, just because the ²³⁸U and ²³⁴U do not reach the secular equilibrium for our lab sub-tandard O₂(NO₃)₂ eagent. But no effect of such UO₂(NO₃)₂ on the analysis of gross α activity is observed after activity of ²³⁴U and ²³⁸U are qualitative measured by α pectrometry.