Rapid determination of 90Sr/90Y in water samples by liquid scintillation and Cherenkov counting

Abstract

Strontium-90 ( 90 Sr) is a ubiquitous contaminant at nuclear facilities, found at high concentrations in spent nuclear fuel and radioactive waste. Due to its long half-life and ability to be transported in groundwater, an accurate method for measuring 90 Sr in water samples is critical to the monitoring program of any nuclear facility. To address this need, a rapid procedure for sequential separation of Sr/ Y was developed and tested in groundwater samples col- lected from an area of riverbed affected by a 90 Sr groundwater plume. Sixteen samples, plus spike and water blanks, were analyzed. Five different measurements were performed to determine the 90 Sr and yttrium-90 ( 90 Y) activities in the samples: direct triple-to-double-coin- cidence ratio (TDCR) Cherenkov counting of 90 Y, liquid scintillation (LS) counting for 90 Sr following radiochemi- cal separation, LS counting for 90 Y following radiochem- ical separation, Cherenkov counting for 90 Y following radiochemical separation and LS counting of the Sr sam- ples for 90 Y in-growth. The counting was done using a low- level Hidex 300SL TDCR counter. Each measurement method was compared for accuracy, sensitivity and effi- ciency. The results following Cherenkov counting and radiochemical separation were in very good agreement with one another.