Waste Characteristics of the Former S-3 Ponds and Outline of Uranium Chemistry Relevant to NABIR Field Research Center Studies

Abstract

The Environmental Sciences Division at Oak Ridge National Laboratory (ORNL) was awarded the first Naturaland Accelerated Bioremediation Research (NABIR) Program, Field Research Center (FRC) based upon the recommendation of a review panel following a competitive peer-reviewed proposal process. The contaminated FRC site at ORNL is centered on groundwater plumes that originate from the former S-3 Waste Disposal Ponds located at the Y-12 Plant and the Y-12 Bone Yard/Bum Yard. Proposals for individual science research projects at the FRC were submitted in the spring of 2000 in response to a solicitation issued by the Department of Energy (DOE). Proposals selected for funding began work in Fiscal Year 2001 (October 1, 2000). The FRC staff have initiated several characterization efforts intended to support, inform, and educate individual FRC investigators, NABIR principal investigators (PIs), and the broader community of the specific conditions, opportunities, and challenges of this site. These efforts include both physical site characterization as well as numerical simulation (modeling) studies. Geochemical modeling has been conducted with the goal of: (1) providing a baseline understanding of the geochemical behavior of uranium (U); (2) examining the interaction of geochemistry and uranium transport in the subsurface; (3) elucidating some potential pitfalls for researchers with respect to manipulating subsurface environments for the purpose of demonstrating bacterially induced U immobilization. The geochemical modeling effort focused on using existing data and resources and did not involve the collection of new data or samples from the field site. Specifically, the following three tasks have been performed to date. (1) Searching for information on the wastes disposed in to the S-3 ponds. These data are typically found in internal technical reports at the labs and are rarely published in the peer-reviewed literature; thus, this information can be very difficult for the scientific community to access. Therefore, these searches may provide a nontrivial resource to investigators. To that end, some analytical data have already been located and the search for more data will continue. (2) Critical evaluation of thermodynamic data that are needed in the modeling calculations. (3) Generating model simulations to illustrate important aspects of U geochemistry and transport behavior in idealized solutions. This report summarizes the results of the geochemical modeling efforts.