Total optimization of a measurement method for 90Sr

When measuring radioactive strontium isotopes, the primary nuclide of interest is the long lived 90Sr. The general aim of this work is to contribute to a more rapid determination by making the Cherenkov measurement of the daughter nuclide 90Y more efficient. There are many instances when such an optimization might be favourable, such as: situations requiring rapid results in order to make decisions or to optimize the utilization of a certain instrument. This work is aimed at the first; to offer an effective method for analysis in preparedness situations. This work has been developed as an assignment from the Swedish Radiation Safety Authority (SSM), in which total optimizations for two separate cases are investigated: ? The first case, where 90Sr is the only radioactive strontium isotope. In this case, the nuclide to be measured is 90Y, which will continue to grow into the sample during the analysis. ? In the second case, both 90Sr and 89Sr are present. To allow a measurement of 90Y that is interference-free from 89Sr there is a need to remove 90Y from its mother nuclide by solid phase extraction. This means that 90Y will be measured The assumed detection limits are based on the action limit for 90Sr in milk (100 Bq/l) as defined by the International Atomic Energy Agency (IAEA). This assumption ensures that the methods presented in this work are applicable in a preparedness situation. Results show that there is a lot to gain with regards to time for both cases. This means that more samples can be measured over a set time, or that measurement results can be obtained faster. This in turn leads to a more rapid process for decision making.