An inter-comparison exercise on the application of ICP-MS techniques for measurement of long-lived radionuclides

Inductively coupled plasma (ICP) spectrometry techniques are widely used in the fields related to environmental monitoring, nuclear waste disposal and management, radioecology and tracer studies, as well as nuclear forensics and nuclear emergency preparedness. Especially ICP mass spectrometry (ICP-MS) is playing an important role for determination of low-level long-lived radionuclides and their isotopic ratios. ICP optical emission spectrometry (ICP-OES) is commonly used for determining stable elements (Al, Fe, Ca, etc.) and cannot perform isotopic ratio measurement with desirable precision and at low analyte concentrations. Therefore ICP-OES is often used as a supplementary technique to ICP-MS in the analysis, for instance, to screen the matrix composition of a sample, or to determine Sr and Y chemical yield in the Sr-90 analysis, etc.
Among the Nordic countries, there are probably less than 20 ICP-MS instruments which are currently applied in the nuclear field for the measurement of radionuclides and their isotopic ratios. Due to different application purposes and technical background of the analysts, each ICP lab has different set-ups and experiences in running these instruments. More efficient application of ICP-MS will be achieved when these experiences are well shared among these labs. Also, for newly established ICP labs or scientists/students in the Nordic countries to quickly build up the competence in operating their instruments in practice, hands-on experience is very valuable. Therefore, within the Nordic-ICP project, an inter-comparison exercise was performed during 2016, which was focused on the measurement of uranium and plutonium isotopes in certified reference material by ICP-MS in combination with radiochemical separation. This report summarizes the results and conclusions obtained base on this inter-comparison exercise.