Impurities as fingerprints in nuclear forensics analysis – The role of certified reference materials and NBL CRM 124 series

Trace element signatures (impurities) can provide crucial ‘fingerprints’ in the investigation of illicit trafficking of nuclear materials, nuclear safeguards and forensics analysis, and non-proliferation control. Impurity signatures potentially reflect the origin of the nuclear material and/or the nature of the processing. The determination of impurities in uranium matrices (e.g., ores, oxides, metals) at various stages in the uranium fuel cycle also plays an important role in material characterization, process control, and the verification of chemical and metallurgical requirements. For example, impurities such as Cd, B, Gd, and Sm are strong neutron absorbers, their concentration in nuclear fuel need to be in compliance with specifications, and increased concentration of other impurities may alter the physical or chemical characteristics of the uranium fuel. Therefore, actinide reference materials certified for impurities are needed for measurement quality assurance/quality control, traceability, method development, and instrument calibration purposes. However, the availability of certified reference materials (CRM) which can be utilized for the above mentioned purposes is limited. NBL has re-evaluated the NBL CRM 124 series – a uranium reference material with 24 trace elements in seven different concentration levels – and certified the trace element concentrations. These results, and the need for future certified reference materials, will be discussed.