Intercalibrated radionuclide activities in spiked water samples of the IAEA worldwide open proficiency test

Proficiency testing is one of methods for regularly assessing the accuracy of the analytical data produced by laboratories for particular measurements. In 2008 and 2010, we participated in the IAEA 2008 and 2010 worldwide open proficiency tests on the determination of natural radionuclides in water spiked with ²²⁶Ra, ²³⁴U and ²³⁸U for activity analysis and with ⁹⁰Sr and ²³⁰Th for gross alpha/beta analysis. Feedback statistics from the IAEA final report showed that the radioactivities of all of the samples fell within an acceptable range according to the IAEA. For ²²⁶Ra analysis, our result showed that ²²⁹Th- ²²⁵Ra is suitable as a chemical tracer, although there are doubts that different co-precipitation efficient between parent ²²⁹Th and its daughter nuclide ²²⁵Ra in published literature. The impact factors of the analysis results, such as the lower limit of detection, standard substances, the background and efficiency for daily determination, are discussed in detail.