Development and Applications of some Radioanalytical Procedures: Analysis of β- and α-Emitting Radionuclides Using Radiometric and ICP-MS Detection Methods

Doctoral thesis, 1998

Analyses of radionuclides are important in environmental monitoring and in research. However, as in the analysis of many other species, interferences may be a problem. In a-spectrometric detection, 238Pu interferes with 241Am, owing to their similar decay energies. In inductively plasma mass spectrometry (ICP-MS), species with the same mass-to-charge ratios will not be resolved by a quadrupole mass filter. However, if interferences are removed prior to measurement, the detection will be specific. Measurement of pure .beta.--emitting radionuclides with radiometric detection will suffer to a high degree from specificity. However, in the analysis of 90Sr, a measurement of the daughter nuclide, 90Y, offers an opportunity. This radionuclide is a high-energy .beta.--emitter, and its short half-life provides an opportunity to verify the half-life. Short-lived radionuclides are often more readily (by means of the detection limit) measured using radiometric detection, because a very small mass is connected to a high activity. On the other hand, long-lived radionuclides are more readily detected using mass sensitive detection, e.g. ICP-MS, if no natural radioactive nuclide of the element is present in the sample. The half-life at which the techniques will be most competitive with respect to the detection limit is of course floating, depending on the methods utilized. Analytical procedures for the assay of some radionuclides in bentonite clay were developed. The radionuclides included are: 90Sr, 99Tc, 236U, 237Np, 239Pu, 241Am and 244Cm. Both radiometric and ICP-MS measurements were used, depending on the half-life of the radionuclides. These analytical procedures were applied to bentonite clay samples from a radionuclide diffusion and spent nuclear fuel leaching experiment. Results regarding the transport of strontium, technetium and some actinides in bentonite clay, as well as the release of these radionuclides from spent UO2 fuel, are presented.