Determination of low-level 90Sr in large volumes of seawater

Abstract

The release of radioactive substances into the environment, particularly the discharge of contaminated water from the Fukushima Daiichi Nuclear Power Plant, has raised public concern. 90Sr, a highly hazardous radionuclide, remains a significant challenge for accurate determination in environmental seawater due to its low concentration. In this work, an effective co-precipitation of 90Sr with SrCO3 and CaCO3 was established for preconcentration of 90Sr from a large volume of seawater up to 45 L by using an appropriate concentration of (NH4)2CO3 instead of Na2CO3 followed by removal of calcium by hydroxide precipitation. A chemical yield of (88 +/- 2)% was achieved for strontium from 45 L of seawater, and the decontamination factors for most radionuclides were higher than 104. The 90Y ingrown from 90Sr decay was used for the determination of 90Sr, and sulfate precipitation was employed to remove radionuclides of Sr, Ba, Ra, and Pb, and the Y was further purified by hydroxide precipitation. The chemical yield of Y was higher than 90% in this step, and the counting efficiency of 90Y by liquid scintillation counting reached 100%. The detection limit for 90Sr was estimated at 0.11 mBq/L for 45 L seawater, an order of magnitude lower than surface seawater levels without direct human nuclear contamination. The method was validated by the standard addition method and successfully applied to determine 90Sr in seawater collected from China seas. The developed method is simple and cost-effective compared to the reported methods and robust for routine analysis of seawater for 90Sr