The United States Department of Energy (DOE) has generated and stored significant amounts of low-level mixed wastes consisting of radioactive materials mixed with hazardous chemical substances in various forms. The DOE is in the process of beginning a cleanup of these mixed wastes at many of its facilities. Many of these waste streams had been previously disposed of by methods acceptable at the time but with the passage of very stringent laws affecting migration of hazardous components, now the disposal areas constitute remediation sites. Disposal of low level radioactive waste potentially containing hazardous materials have also fallen under land disposal restrictions and currently no mixed waste is going to low level disposal facilities. The paper will address why the DOE is just now starting to comply with environmental laws, why there is a need to find more effective and less expensive means of cleaning up wastes, how the DOE is organizing to accomplish this cleanup, and several plasma technology development efforts in the DOE Complex that show promise of meeting these needs.

About 155,000 cubic meters of waste contaminated with both radioactive isotopes and hazardous chemicals are stored at some 30 DOE sites, and another 450,000 cubic meters are buried. While DOE is making a concerted effort to properly dispose of this waste, the amount translates to a multi-decade effort that will require handling, characterizing, and shipping hundreds of thousands of waste containers at a total cost of billions of dollars. This report describes basic scientific research that can lead to new technologies for performing these tasks more safely and cost effectively.

The US Department of Energy (DOE) stores and generates significant amounts of low-level mixed wastes (LLMW) consisting of radioactive materials mixed with hazardous chemical substances. Many of these wastes are regulated under the US Environmental Protection Agency (EPA) Land Disposal Restrictions and must be treated and disposed in compliance with applicable state and federal requirements. In general, treatment requirements include elimination of organic hazardous constituents and stabilization of inorganic hazardous constituents. Final waste forms must meet both EPA leach testing and DOE disposal acceptance criteria. The DOE currently does not have an adequate capability to meet these treatment objectives. The Mixed Waste Treatment Project has been established by the DOE to define needed LLMW treatment capabilities as a basis for either a prototype plant design or an existing facility modifications. Existing DOE mixed waste data bases were analyzed to identify the range of waste quantities and types and to define broad treatment categories needed to bring these wastes into compliance. Using these treatment categories as a starting point, we constructed a baseline flow sheet defining process steps from receipt through final form. From this baseline flow sheet, we developed functional and operational requirements (F & ORs) for each process train. An initial set of near-term technologies was identified for each process step, and alternative near- and long-term options were listed. Based on these analyses, we identified technology gaps and improvement needs in the areas of characterization, waste handling, segregation and sorting, size reduction, decontamination, materials recycle, primary and secondary treatment for RCRA compliance, offgas treatment, and final waste forms.

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This paper describes a new process for treating mixed hazardous and radioactive waste, commonly called mixed waste. The process is called the Hybrid Treatment Process (HTP), so named because it is built on the 20 years of experience with vitrification of wastes in melters, and the 12 years of experience with treatment of wastes by the in situ vitrification (ISV) process. It also uses techniques from several additional technologies. Mixed wastes are being generated by both the US Department of Energy (DOE) and by commercial sources. The wastes are those that contain both a hazardous waste regulated under the US Environmental Protection Agency's (EPA) Resource, Conservation, and Recovery Act (RCRA) regulations and a radioactive waste with source, special nuclear, or byproduct materials. The dual regulation of the wastes increases the complexity of the treatment, handling, and storage of the waste. The DOE is the largest holder and generator of mixed waste. Its mixed wastes are classified as either high-level, transuranic (TRU), or low-level waste (LLW). High-level mixed wastes will be treated in vitrification plants. Transuranic wastes may be disposed of without treatment by obtaining a no-migration variance from the EPA. Lowlevel wastes, however, will require treatment, but treatment systems with sufficient capacity are not yet available to DOE. Various facilities are being proposed for the treatment of low-level waste. The concept described in this paper represents one option for establishing that treatment capacity.