Rapid measurement of cesium-137 (137Cs) in seawater using an ionexchange resin (AMP-PAN resin, KNiFC-PAN resin)

Abstract

In this study, we attempted to optimize a rapid preconcentration method by cesium- 137 (137Cs) in seawater (100L) based on a commercial ion-exchange resins (AMP- PAN resin (Ammonium MolybdoPhosphate- polyacrylonitrile) and KNiFC-PAN resin (Potassium-Nickel Hexacyanoferrate (II)- polyacrylonitrile)). The concentrated 137Cs sample were measured using the High Purity Germanium (HPGe) Gamma-ray Spectroscopy System (Ortec Inc., USA) with relative detection efficiency of 100% (energy calibration error within ±1% range and within ±5% range). In this study, 137Cs preconcentration was conducted under various conditions. i) Time (1hour, 3hours, 4hours), ii) Amount of resin (5g, 19g, 25g) and iii) Stirring type (stir, cross-stir, air bubble). First, the sample was reacted with resin for at least 3 hours, the best recovery rate was 74.6 ± 1.6% for AMP-PAN resin and 94.5 ± 2.6% for KNiFC-PAN resin. Therefore, all preconcentration experiments were performed for 3 hours. Second, the amount of ionexchange resin (5g, 19g, 25g), when 25g used, AMP-PAN resin was 81.6 ± 2.4% and KNiFC- PAN resin was 93.8 ± 2.1%, which was 1- 4 times higher than that of 5 g and 19 g. Third, in the case of stirring type, AMP-PAN resin was 74.60 ± 1.6% and KNiFC-PAN resin was 93.8 ± 2.1% when cross-stirring, the recovery was more than twice as higher than other stirring-types. Regardless of the reaction experiment condition, when using KNiFC-PAN resin, it was consistently higher than (about 1.2 times) AMP-PAN resin. In comparison with AMP co-precipitation; it takes about >7 days after samples were moved to laboratory from the sea; our method 137Cs was able to reduce the to 6 hours for per-treatment and 8 hours for detection. Our results suggest that this optimized rapid 137Cs analysis in seawater can be used in the event of a radioactive accident requiring urgent monitoring in the ocean.