Evaluation of uncertainty components associated with alpha-particle spectrometric measurements of uranium isotopes in water

Qualifications of uncertainties associated with the measurement of specific activity concentration of uranium radioisotope (238U) in water samples by alpha-particle spectrometry are presented. Possible sources of uncertainty are identified and quantified in the activity concentration measurements of 238U isotope; the major source being the statistical counting uncertainty as expected. The combined relative standard uncertainty U(a238U) of the measurement was calculated as 1.4 Bq kg−1 (7.9%) for the investigated NPL sample. The accuracy and precision of recommended procedure were checked analysing six spiked water samples supplied from IAEA-proficiency test exercises. The results were evaluated in terms of relative bias, z-score, u-score, trueness and precision. These results show that the activity values and their uncertainties are in good agreement with recommended values.