An approach for the indirect determination of 238U and 232Th content in ceramic products based on gross alpha and gross beta measurement

The aim of this work was the development of a procedure for the indirect characterization of 238U and 232Th in ceramic products using the quantification of gross alpha and gross beta activities in a low background proportional counter, which is less time consuming and cheaper than the direct radiochemical methods and gamma spectrometry. The procedure was applied, first, to a reference material used to fine-tune the procedure and statistical techniques, and then, for two types of ceramic products: micronized zircon and zircon flour samples, and spray-dried ceramic powders (atomized). This procedure requires obtaining linear regression models for estimating the activity of 238U and 232Th as a function of specific gross alpha and gross beta measurements. Regression models must be obtained for each type of ceramic material together with the range of application of the model, which depend primarily on the ratio between 238U and 232Th activities. The applications to micronized zircon and zircon flours, and spray-dried ceramic powders demonstrated that the models obtained for the indirect characterization of 238U and 232Th activities explain more than 95% of the variability in the data. In addition, those models were used for predicting the results of new validation samples. Regarding the micronized zircon and zircon flours, predictions were good for the 238U activity with a relative bias of less than 10%, while they were not so accurate for the 232Th activity, with a relative bias of less than 15% for most of the samples. For spray-dried ceramic powders, the predictions were quite good for the 238U activity with a relative bias of less than 20% irrespective of the cluster to which the validation sample belongs, and similarly for the 232Th activity.