Speaker
Description
Authors (affiliation): Emma Braysher (NPL, UK), Heather Thompkins (NPL, UK), Saskia Burke (NPL, UK), Hibaaq Mohamud (NPL, UK), Frankie Falksohn (NPL, UK).
A number of long-lived radionuclides suffer from half-life measurements that are outdated, have inconsistencies in the values obtained and/or limitations with regards to the uncertainty budget. When used in combination with absolute counting techniques, inductively coupled plasma mass spectrometry (ICP-MS) is a potentially powerful metrological tool for providing updated and precise half-life measurements. This work shows the development of a consistent approach to measurement of the number of atoms using ICP-MS/MS for the first time for this purpose to contribute to updated, precise half-life measurement of long-lived radionuclides. ICP-MS/MS has unique interference removal capabilities, the advantages of which have been demonstrated for improved sample throughput for nuclear decommissioning and environmental monitoring applications. However, this technique also has the potential to enable half-life measurement for usually difficult to measure radionuclides.
Results are shown for several radionuclides (32Si, 36Cl, 93Zr, 238U and 239Pu), each with a range of isobaric, tailing and polyatomic interferences that must be removed using offline chemical and/or ICP-MS/MS separation. In all cases, ICP-MS/MS measurement was performed using a series of isotope dilutions using standardised solutions. The importance of suitable isotopic ratio reference materials for correcting the instrument mass bias is also highlighted for each radionuclide. Instrument setup is a key consideration, including the sample introduction system and the use of the collision-reaction cell for optimising interference removal without compromising sensitivity. The optimised setup for each radionuclide was used to derive the number of atoms, which is combined with the absolute activity values to obtain a remeasured half-life value.
The advantages and limitations of ICP-MS/MS compared to alternative instrument designs (specifically multi-collector ICP-MS) is discussed, as well as further radionuclides of interest that could benefit from ICP-MS to contribute to update half-life measurements.
