Radionuclide-selective sensors for water monitoring: In situ sensor system for analysis of Tc-99 in Hanford groundwater


Oleg Egorov, Matt O'Hara, Jay W. Grate, Michael Knopf, and John Hartman. Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, P7-22, 902 Battelle Blvd, PO Box 999, Richland, WA 99352
Production of nuclear weapons materials and storage of nuclear wastes at the U.S. Department of Energy (DOE) Hanford site has lead to the radioactive contamination of soil and groundwater. Monitoring of the radionuclide contaminants such as 99Tc in groundwater represents an important element in support of the remediation and long-term stuardship activities. Direct, isotope-specific determination (sensing) of pure beta-emitting 99Tc in aqueous matrix represents a substantial challenge due to short radiation range and energy overlap or interference problems. The research in our laboratories has been directed at addressing the fundamental challenges of monitoring of low levels of non-gamma-emitting radionuclides (e.g.Tc-99) in groundwater. We will present results on the development and testing of the reagentless Tc(VII)-selective radiometric sensor concept for in-situ detection of Tc in groundwater. The concept is based on the use of a dual-function composite sensor column designed to incorporate radionuclide selective uptake and scintillating properties. Sensor element, scintillation detection, sample delivery, data acquisition and instrument control components were integrated into a single functional unit compatible with the 3.5-inch well geometry.