Dissolution experiments were performed on actual samples of NWCF Run H-4 radioactive calcine in fiscal years 1998 and 1999. Run H-4 is an aluminum/sodium blend calcine. Typical dissolution data indicates that between 90-95 wt% of H-4 calcine can be dissolved using 1gram of calcine per 10 mLs of 5-8M nitric acid at boiling temperature. Two liquid raffinate solutions composed of a WM-188/aluminum nitrate blend and a WM-185/aluminum nitrate blend were converted into calcine at the NWCF. Calcine made from each blend was collected and transferred to RAL for dissolution studies. The WM-188/aluminum nitrate blend calcine was dissolved with resultant solutions used as feed material for separation treatment experimentation. The WM-185/aluminum nitrate blend calcine dissolution testing was performed to determine compositional analyses of the dissolved solution and generate UDS for solid/liquid separation experiments. Analytical fusion techniques were then used to determine compositions of the solid calcine and UDS from dissolution. The results from each of these analyses were used to calculate elemental material balances around the dissolution process, validating the experimental data. This report contains all experimental data from dissolution experiments performed using both calcine blends.

The purpose of LDRD #2349, Characterize and Model Final Waste Formulations and Offgas Solids from Thermal Treatment Processes, was to develop a set of tools that would allow the user to, based on the chemical composition of a waste stream to be immobilized, predict the durability (leach behavior) of the final waste form and the phase assemblages present in the final waste form. The objectives of the project were: • investigation, testing and selection of thermochemical code • development of auxiliary thermochemical database • synthesis of materials for leach testing • collection of leach data • using leach data for leach model development • thermochemical modeling The progress toward completion of these objectives and a discussion of work that needs to be completed to arrive at a logical finishing point for this project will be presented.

Plans for disposing of the high-level radioactive wastes at the Hanford Site call for retrieving, pretreating, and finally immobilizing the wastes in a glass matrix. Since the cost for vitrifying and disposing of high-level wastes will be very great, pretreatment processes are being developed to reduce their volume. The baseline method for pretreating Hanford tank sludges is caustic leaching. Earlier studies with Hanford tank-sludge simulants and with actual Hanford tank sludges have indicated that treating water-washed and caustic-leached solids with oxidants can significantly increase the removal of Cr. Permanganate and ozone have been shown to be generally the most rapid and effective chemical agents for this purpose. The work described in this report continues to examine the effectiveness of solubilizing additional Cr from Hanford tank wastes by oxidation of the water-insoluble solids from tanks U-108, U-109, and SX-108 under alkaline conditions. The current study confirms that permanganate is highly effective at removing chromium from water solids under alkaline conditions, with Cr removals of up to 99+%. Elemental oxygen can also be highly effective, with removals up to 97+%.

The U.S. Department of Energy (DOE) continues to face a major tank remediation problem with approximately 332 tanks storing over 378,000 ml of high-level waste (HLW) and transuranic (TRU) waste across the DOE complex. Most of the tanks have significantly exceeded their life spans. Approximately 90 tanks across the DOE complex are known or assumed to have leaked. Some of the tank contents are potentially explosive. These tanks must be remediated and made safe. How- ever, regulatory drivers are more ambitious than baseline technologies and budgets will support. Therefore, the Tanks Focus Area (TFA) began operation in October 1994. The focus area manages, coordinates, and leverages technology development to provide integrated solutions to remediate problems that will accelerate safe and cost-effective cleanup and closure of DOE`s national tank system. The TFA is responsible for technology development to support DOE`s four major tank sites: Hanford Site (Washington), INEL (Idaho), Oak Ridge Reservation (ORR) (Tennessee), and Savannah River Site (SRS) (South Carolina). Its technical scope covers the major functions that comprise a complete tank remediation system: safety, characterization, retrieval, pretreatment, immobilization, and closure.