Design and construction of a Cerenkov counter for in situ monitoring of 90Sr in groundwater

Migration of groundwater contamination from beneath the Hanford Site into the Columbia River creates a need for in situ 90Sr monitoring. The prototype monitor discussed here was designed for deployment downwell and provides near-real-time determination of the 90Sr concentration in a two-liter groundwater sample. This manuscript discusses the design, construction and preliminary results for a prototype monitor. Calibration and testing results of the as-built system show qualitative agreement between simulated predictions and experimental results. Downwell and laboratory tests demonstrate a sensitivity to 90Sr at concentrations below 8 pCi/l (0.3 Bq/1) at a 90% confidence level in measurement times of less than four hours.