Winterization Salt Effects on Strontium-90 Transport at the West Valley Demonstration Project, West Valley, New York
1 PDH Credit Available
presented by William T. Frederick and Francine Cohen
Department of Energy - West Valley
Abstract -
The West Valley Demonstration Project (WVDP) includes a Main Plant Processing Building (MPPB) that experienced a historical release of process fluids containing an array of fission-product radionuclides, including strontium-90 (Sr-90). This radiological discharge impacted site groundwater and created a 300-meter-long Sr-90 plume that flows from the MPPB to groundwater discharge points along surface-water courses that bound the site. The site installed a 260-meter-long passive permeable treatment wall (PTW) composed of clinoptilolite (zeolite) in the path of the plume to mitigate the transport and off-site discharge of Sr-90. The granular zeolite in the PTW preferentially exchanges sodium and potassium for Sr-90 (and other natural cations) through a cation-exchange process.
Analytical and field data from PTW performance monitoring and site-wide groundwater monitoring programs indicate that the PTW is performing as designed, with an expected reduction in performance due to the saturation of cation-exchange sites in the zeolite. An increase in total dissolved solids in site groundwater emerged in 2020 after that site used a 100% salt (NaCl) product for road winterization in lieu of previous mixtures of 70% sand with 30% salt. The subsequent salt-rich recharge to groundwater increased the salinity, ionic strength, and chloride content of site groundwater. Sr-90 concentrations in multiple monitoring wells also increased due to the higher anionic chloride that apparently desorbed weakly bound Sr-90 (and other divalent cations) from soils in the plume. This process elevated sodium, calcium, magnesium, barium, and “cold” strontium in groundwater, which also competes with Sr-90 for exchange sites in the PTW zeolite. These conditions prompted a geochemical investigation that resulted in reverting back to a 70% sand and 30% salt mix for winterization. The resulting effect on groundwater includes lower salinity, cation concentrations, and free chloride, which are accompanied by reduced Sr-90 concentrations in both the ambient groundwater and PTW groundwater (both inside and downgradient of the PTW). The reductions in cations and chloride continue in site data, with Sr-90 lagging likely due to continued cation competition for adsorption to site soils and exchange in the PTW zeolite. The site expects the exchange of Sr-90 into the PTW zeolite to rebound and reflect the robust attenuation of the Sr-90 plume that occurred earlier in the PTW lifecycle.
Speaker Bios -
William T. Frederick
Bill Frederick is a licensed Professional Geologist in Pennsylvania and the Lead Physical Scientist with the Department of Energy at the West Valley Demonstration Project. He is a graduate of Binghamton University and the University at Buffalo. Bill has over 30 years of private- and public-sector experience in hydrogeologic investigations, numerical groundwater flow and contaminant-transport modeling, remedial action design, and project management.
Francine Cohen
Francine Cohen is an environmental geologist with CH2M Hill BWXT West Valley LLC (CHBWV) at the West Valley Demonstration Project and is the lead scientist for the groundwater monitoring program. She is a graduate of Binghamton University and attended Western Michigan University in Kalamazoo, MI. Francine has spent the majority of her career working at various U.S. Department of Energy sites across the county and has over 30 years of experience in groundwater monitoring and evaluation, hydrogeologic investigations, regulatory compliance, and radioactive and hazardous waste management.
