Improvement in 90Sr measurements at very low levels in environmental samples

Various anthropogenic sources contribute to the inventory of long lived beta emitters in the environment. Studies have been carried out to obtain the 90Sr distribution in environment in order to estimate its impact in terms of radiation exposure to humans. Various environmental samples were collected and analysed for 90Sr activity concentrations. As natural beta emitters are present in all matrices, an incomplete radiochemical separation leads to over evaluation of the results. An accurate and reliable method has been routinely implemented to extract, purify, and analyse 90Sr in all types of environmental matrices by the Laboratory of Radioactive Measurement in Environment. The radiochemical procedure is combined with a proportional counting for 90Sr detection. After leaching the 20 g aliquot, different protocols have been tested. The effectiveness of Sr-spec resin for Sr isolation has been demonstrated and chosen for the protocol selected. Radiochemical procedure was tested using IAEA reference materials. Results are discussed in terms of recovery, purification efficiency and limit of detection. The influence of a filtrated atmosphere on proportional counting is also discussed.