Simple determination of 90Sr in water in environmental radioactivity survey

A method is presented for the determination of 90Sr in environmental water samples by direct milking of its daughter product 90Y. An anionic complex between yttrium and dipicolinic acid is formed in situ in the water sample at pH 3. The complex [Y(dipic)3]3− is then extracted by an anionic exchanger (AG 1x4).The procedure is very simple and can be almost completely automatized and processed overnight. Technician working time is less than two hours for 6 samples and results can be obtained in less than 48 hours. The procedure gives yttrium recoveries above 80% for a water sample of one liter volume and needs an yttrium carrier of 10 mg. Very good decontamination factors are obtained and 90Y half-life measured on water samples with 90Sr activities above the detection limit or spiked with 90Sr is closed to 64 hours, indicating a very pure 90Y source. With using a low background gas flow proportional counter, a detection limit of 5·10−3Bq·l−1 has been achieved for one liter of water. If a lower detection limit is required, the volume can be increased up to 5 liters without any decrease in the performance of the method.