Monday, June 18, 2007 - 11:30 AM
Snake River (Boise Centre on the Grove)

Automated radioanalytical system for the determination of Sr-90 in environmental water samples: development of a prototype groundwater monitor for autonomous field operation

Matthew J. O'Hara, Pacific Northwest National Laboratory, Richland, WA and Scott R. Burge, Burge Environmental, Inc., Tempe, AZ.

An automated radioanalytical system has been developed for the determination of Sr-90 in groundwater. Through the use of simple valving and a fluid delivery pump, Sr-90 is selectively and quantitatively concentrated from a groundwater sample onto a sorbent column packed with SuperLigŪ 620. The groundwater has been matrix adjusted so that 1) Sr-90 affinity for the sorbent is high, and 2) its daughter product, Y-90, has no retention on the sorbent media. After a brief ingrowth period, the Y-90 daughter is eluted from the column and delivered to a customized Cherenkov detection flow cell. The Sr-90 activity concentration in the groundwater can be calculated from the Cherenkov signal, the known Y-90 ingrowth, and the known volume of groundwater originally concentrated onto the sorbent column. We have demonstrated that the sorbent column can be automatically regenerated (i.e., Sr-90 eluted) and the column can be re-used over the course of many analysis cycles. The system has shown good linear performance over a wide range of Sr-90 activity concentrations which exist in contamination plumes at the Hanford Site (up to 5000 pCi/L). Furthermore, the system is capable of measuring Sr-90 below the drinking water limit of 8 pCi/L. The characterization of this analytical method has enabled the development of a prototype field deployable Sr-90 analyzer. It is capable of automated well water sampling, sample acidification and matrix spike addition. It operates on a 12 Volt system, which is conducive to solar / battery power operation in the field.