Measurement of 89Sr and 90Sr in samples with high amounts of chemical interferences

When measuring samples containing radioactive strontium it is important to consider for example: the age of the sample (i.e. time passed since the end of the fission process), its matrix and possible interferences. In the case of a nuclear weapons detonation there will be a need to measure samples with a multitude of radioactive interferences, but also with high calcium content, e.g. milk or other dairy products. These measurements are primarily performed in order to make decisions regarding our livestock and their grazing, but also to make sure that no dairy products with an activity higher than the current action level are distributed to and consumed by the population. With this work we aim to investigate how double strontium separation, in methods based solely on strontium separation chemistry, could provide reliable results when dealing with samples of high calcium concentration originating from nuclear weapons detonation. Previous studies have shown that samples of high calcium content are difficult to measure due to the chemical similarities between calcium and strontium. There have also been investigations showing that high 89Sr/90Sr ratios makes determination of the longer lived 90Sr problematic for a number of methods presented in the literature. This is due to insufficient decontamination of interferences when measuring 90Sr via the daughter nuclide 90Y. And finally, short lived interferences are known to cause a positive bias to radioactive strontium measurements if not considered and dealt with properly. These are all points to be addressed and overcome within the scope of this project.