At the Savannah River Site (SRS) we are currently finalizing the design for a multi-system vitrification process that will be installed in the F-Canyon Multi-Purpose Process Facility (MPPF), an existing highly shielded, remotely operated facility. Authorization to proceed beyond the preliminary design based on the recommendation of a Formal Design Review Board was requested in May of 1999. The Savannah River Technology Center (SRTC) Process Development Group has been conducting research and developing a process to identify equipment design bases and process operating parameters since 1996. The goal of the project is to stabilize a tank of ~11,000 liters of nitric acid solution containing valuable isotopes of americium (Am) and curium (Cm). Vitrification has been selected as the most attractive alternative for stabilization and provides the opportunity for recovery and eventual reuse of the actinides. The final glass form will be placed in interim storage awaiting a disposition by the Department of Energy. This paper presents a brief history of the stabilization program and an overview of the entire Am/Cm stabilization process. This paper also provides details of a specific processing issue related to drain tube pluggage (devitrification) that was encountered during the development of the baseline batch vitrification process, and the remedy employed to reduce the potential for further drain tube pluggage.

Evaporation of High Level and Low Activity (HLW & LAW) radioactive wastes for the purposes of radionuclide separation and volume reduction has been conducted at the Savannah River and Hanford Sites for more than forty years. Additionally, the Savannah River Site (SRS) has used evaporators in preparing HLW for immobilization into a borosilicate glass matrix. The Hanford River Protection Project (RPP) is in the process of building the world’s largest radioactive waste treatment facility, Waste Treatment Plant (WTP), which will use evaporators to concentrate the liquid waste and plant recycles prior to immobilization into a borosilicate glass matrix. Radioactive waste is evaporated at each site using various evaporator designs (e.g., forced circulation, horizontal bent tube). While the equipment used to evaporate radioactive waste is relatively simple in design, the complexity in the evaporator processes in current service and in those currently in the design stages stems from the heterogeneous nature of the waste and the effects of seemingly minor components (e.g., Si) on the process. Aqueous electrolyte thermodynamic modeling and experiments have been conducted by the SRS Savannah River Technology Center (SRTC) in support of the SRS HLW and Defense Waste Processing Facility (DWPF) Evaporators and the Hanford RPP WTP. After 40 years of successful operation, accumulation of two solid phases (a nitrated aluminosilicate, Na8AL6Si6O24(NO3)2•4H2O and sodium diuranate, Na2U2O7) developed as an insoluble phase in the Savannah River Site (SRS) 2H evaporator in 1996. The aluminosilicate scale deposit caused the SRS 2-H evaporator to become completely inoperable by October 1999. Accumulation of the sodium diuranate phase on the aluminosilicate scale has caused criticality concerns. Modeling and experiments were conducted to develop a method to control the process chemistry in order to prevent the formation of aluminosilicate deposits in the future. The lessons learned from the development, design, and operation of the SRS waste treatment facilities and the currently operating 242-A Hanford HLW evaporators were applied by SRTC in support of the development and design of the Hanford WTP evaporators. Thermodynamic equilibrium modeling along with solubility and physical property experiments are being conducted to develop process control and flow sheet models. Additionally, lessons learned from the development of an advanced antifoam agent for the SRS vitrification process evaporators are being applied to the testing and development of an antifoam agent for the Hanford WTP evaporators. This paper will discuss the methodologies, results, and achievements of the SRTC evaporator development program that was conducted in support of the SRS and Hanford WTP evaporator processes. The “cross-pollination” and application of waste treatment technologies and methods between the Savannah River and Hanford Sites will be highlighted. The “cross-pollination” of technologies and methods is expected to benefit the Department of Energy’s Mission Acceleration efforts by reducing the overall cost and time for the development of the baseline waste treatment processes.

Isotopes of Am and Cm were produced in the past at the Westinghouse Savannah River Site (SRS) for research, medical, and radiological applications. These highly radioactive and valuable isotopes have been stored in an SRS reprocessing facility for a number of years. Vitrification of this solution will allow the material to be more safely stored until it is transported to the US Department of Energy Oak Ridge National Laboratory for use in research and medical applications. The Savannah River Technology Center (SRTC) research and development program supporting the stabilization of the Am-Cm solution began in 1995. SRTC is developing the equipment design bases and process operating parameters to vitrify the nitric acid-based Am-Cm solution. A full-scale pilot facility has been in operation since late 1995. Originally, the vitrification process was to be accomplished using a Pt-Rh, slab-geometry bushing melter similar to that used in the glass industry. Several equipment application challenges were addressed, and significant progress was made on the original feed system, melter, drain tube, and off-gas design. However, in October 1997, the bushing melter failed, and a batch flow sheet concept was proposed. The alternative of batch vitrification and the simplication of the melter system addressed many ofmore » the technical problems encountered in the earlier development efforts. While a new induction-heated cylindrical melter was being installed, vitrification experiments with the product slurry from a new pretreatment step were carried out in a resistance-heated platinum melter to validate the technical feasibility of the new flow sheet. These experiments demonstrated the initial feasibility of the process and provided the baseline for operations in the cylindrical induction melter (CIM).« less