Measurement of trace elements in uranium oxide materials using external calibration - An uncertainty study

Nuclear forensics is a scientific discipline that aims to e.g. investigate nuclear and other radioactive material found out of regulatory control such as smuggling incidents and thefts. Nuclear forensics can be used to study different characteristics in order to help establishing the origin and intended use of a nuclear material. One such characteristic is the concentrations of trace elements in the material. These trace elements are present in the material as impurities that have followed the uranium from the mining or have contaminated the material during the process to produce e.g. nuclear fuel and are present at very low concentrations. Therefore, inductively coupled plasma mass spectrometry (ICP-MS) is a suitable analysis method. ICP-MS can be used to measure elements at the pg/g level with good precision and accuracy. In nuclear forensics it is important that the measurements are followed by measurement uncertainties that are fit-for-purpose enabling relevant comparisons between e.g. different materials. The aim of the project was to develop a method to measure the concentration of a number of elements in dissolved uranium oxide with low measurement uncertainties. The work shows that measurement uncertainties less than 2% (k=2) are possible for certain elements, while other elements are measured with substantially higher measurement uncertainties, up to 20% depending on concentration and background of the measured element.