Evaluation of measurement uncertainty components associated with results of radiochemical neutron activation analysis for determination of uranium traces
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Being aware of the importance to consider every step in the evaluation of the combined measurement uncertainty of the result, the purpose of this work was to evaluate the contribution of the radial thermal neutron flux gradient to the uncertainty budget for trace level uranium determination in biological materials by a radiochemical neutron activation analysis (RNAA). Determination of uranium via the short-lived nuclide 239U was based on solvent extraction with TBP and measurement of the chemical yield from the gamma-ray spectrum of the isolated fraction via 235U. It has been shown previously, that radial neutron flux gradient, could have a relevant effect on the final result obtained by RNAA. In the present work, radial neutron flux gradient within the irradiation assembly generally accepted in our lab (standards tapped beside the sample), varied between 93 and 108% around the mean value and contributes approximately 20% to the combined measurement uncertainty of the result.
KeywordsRadial neutron flux gradient Measurement uncertainty Radiochemical neutron activation analysis Uranium
This work was supported by Ministry of Higher Education, Science and Technology of the Republic of Slovenia within the research programme P1-0143.
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