Reference materials characterized for impurities in uranium matrices: An overview and re-evaluation of the NBL CRM 124 series

The characterized concentrations of 24 impurity elements in New Brunswick Laboratory (NBL) Certified Reference Material (CRM) 124 were reevaluated. A provisional certificate of analysis was issued in September 1983 based upon the “as prepared” values (gravimetric mixing). The provisional certificate does not state uncertainties for the characterized values, or estimate the degree of homogeneity. Since release of the provisional certificate of analysis various laboratories have reported analytical results for CRM 124. Based upon the reported data a re-evaluation of the characterized values with an estimate of their uncertainties was performed in this work. An assessment of the degree of homogeneity was included. The overall difference between the re-evaluated values for the 24 impurity elements and the “as prepared” values from the provisional certificate of analysis is negligible compared to the uncertainties. Therefore, NBL will establish the “as prepared” values as the certified values and use the derived uncertainties from this work for the uncertainties of the certified values. The traceability of the “as prepared” values was established by the gravimetric mixing procedure employed during the preparation of the CRM. NBL further recommends a minimum sample size of 1 g of the CRM material to ensure homogeneity. Samples should be dried by heating up to 110 °C for one hour before use.