Worldwide Open Proficiency Test: Determination of ... - Nucleus - IAEA

Figure 22: Part of the Thorium radioactive series LARA data Table page 227.
4.7. Lessons learned related to radiochemical determinations
In this PT, it was observed that the number of participating laboratories reported their results
using radiochemical procedures was three times less than those who used gamma
spectrometry (GS). It is obvious that the laboratory infrastructure and analytical skills in
radiochemical procedures (RCP) are more demanding.
In general, it was found that the level of performance of laboratories performing RCP was
lower than those performing GS.
For instance, Am-241 in the moss-soil was analyzed by the participating laboratories using
both GS and RCP; the percentage of not acceptable results was 19% and 38% for GS and
RCP respectively.
In the case of Sr-90, 48% of the reported results failed to meet the PT criteria, 25% of the
laboratories reported overestimated results with more than 100% bias as it can be seen in
Figure 23. The overestimation of Sr-90 results could be attributed to difficulties in the
radiochemical. During the radiochemical separation, if the Sr-Ra was not perfectly separated
and Ra remains in the Sr fraction, this could cause an overestimation in Sr-90 activity result.
Final Darft, page 35