PNNL

Abstract

Migration of groundwater contamination from beneath the U.S. Department of Energy’s Hanford Site into the Columbia River creates a need for in situ 90Sr monitoring. The prototype monitor discussed here is designed for deployment inside a monitoring well and provides near-real-time determination of the 90Sr concentration in a two-liter groundwater sample. The measurement is made by direct detection of Cerenkov light generated in the water by beta decay of the 90Y daughter. This manuscript presents results from a prototype monitor that was designed by a parametric Monte Carlo simulation study. Calibration and testing results of the as-built system show near perfect agreement between simulated predictions and experimental results. Downwell and laboratory tests demonstrate that the prototype monitor is sensitive to 90Sr at concentrations below drinking water standards of 8 pCi/l (0.3 Bq/l) at the 90% confidence level in measurement times of less than four hours.