Thorium in the workplace: the preparation and validation of comparison samples for a European-based measurement...

The quality of any comparison exercise depends critically on the quality. accuracy and fitness for purpose of the comparison samples. The comparisons were designed to move progressively from the testing of the analysis capabilities for relatively simple. aqueous solutions through to the more complex natural matrix materials encountered in the workplace. In each case, it was imperative that the comparison samples were prepared and validated in such a way as to ensure traceability of their activity values to national and international standards of radioactivity, to enable a reasonable estimate to be made of the uncertainty on those values and to ensure homogencity both within and between samples. The processes involved are discussed.