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--> 7 Findings and Recommendations The Committee on Mixed Wastes was requested by the Office of Science and Technology (OST, EM-50) to review and evaluate the state of development of the final waste forms of treated mixed wastes as they arise from current and emerging treatment technologies. The committee was also asked to identify the options the Department of Energy (DOE) might consider in technology development in order to achieve the desired waste forms that are cost-effective and safe for disposal. In carrying out the review, the committee received formal presentations from DOE staff and other individuals, and examined documents and data provided by DOE and from other sources. Some committee members visited waste contractors and DOE sites. In the committee's view, the successful operation of any technology-based system is the result of system design and management. Discrepancies between desired and actual performance provide the impetus for research and development (R&D) in both technology and management sciences. This concept is a continuum of efforts aimed toward a defined goal, namely matching the actual system performance to the desired performance. In practice, the desired performance is defined by legislation, federal regulations, DOE cleanup needs, and stakeholder values. The DOE Office of Environmental Management's (EM's) responsibility for cleaning up the weapons complex and disposing of the wastes makes the current mixed waste focus area (MWFA) program
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--> similar to an industrial R&D program focused on a fixed end point. Such R&D programs undergo a natural evolution of changing emphasis and scope. In the first stages, the R&D program is called on to define basic science and technology. As the program progresses, the role of R&D changes, shifting from a research mode to a developmental and demonstration mode and into a support mode. Having defined the technology, the R&D organization must then focus on supporting deployment of the technology. The committee views the role of OST and its MWFA as provider of scientific and technical support in all phases of this evolution. MWFA presentations to the committee described a clear strategy for resolving technology deficiencies that fits within the scope of a supporting R&D organization such as OST.1 However, the presentations indicated that MWFA is using only part of a comprehensive systems approach to waste management, which begins with the untreated waste and ends with closure of the disposal facility, and evolves stepwise from basic R&D to technical support for process deployment. The committee's recommendations discussed below reflect its view of the importance of the systems approach for technology development and deployment activities by the MWFA. General Findings and Recommendations The committee's primary recommendation is that MWFA should no longer emphasize the development of new classes of waste forms. After reviewing the technologies available to treat EM's mixed waste inventory, and considering the resulting waste forms, it is the committee's judgment that no new classes of waste forms are required. Clearly no single form is appropriate for all wastes, but collectively the variety of available waste forms and well-established waste form production technologies make it unlikely that any totally new class of waste forms will be necessary to complete EM's planned cleanup program. MWFA should now emphasize engineering design, integration, and scale-up of its proposed treatment processes and their demonstration and deployment at the DOE sites. Technology development and deployment 1 Presentations heard by the committee are described in Appendix B.
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--> must be cost-effective and commensurate with EM waste management strategy described in "Paths to Closure" (DOE, 1998c). Secondly, the committee recommends that MWFA should continue its practice of identifying, prioritizing, and responding to technology deficiencies. As discussed in Chapter 4, the MWFA has established a rational and systematic program that identifies and prioritizes deficiencies. The committee compliments MWFA on this effort and encourages continued updates of the Technical Baseline Report to document the state of its technology development and deployment activities. Thirdly, the committee recommends that MWFA should broaden its use of the systems approach, in selecting, developing, and deploying technologies. Such an approach would begin with characterization of the waste (development of cost-effective and efficient methods) and definition of the required performance of a proposed treatment technology, based on EM's needs, regulatory requirements, and stakeholder expectations. Using its technical and managerial resources, MWFA should develop and assist in the design, development, and deployment of the new technology to ensure that the technology meets its performance goals. An important aspect of a good systems approach is flexibility to accommodate new information experiences and reasonable changes in the desired output. Inevitably there are iterations between the actual and the desired performance of any waste management system as its technology matures and expectations change. In recommending that MWFA broaden its systems approach, the committee recognizes that the technical issues pertaining to waste management are often overshadowed by non-technical (e.g., political and social) issues. Public acceptance of a waste management strategy may be transient, which creates a moving target for engineers and program planners. An example of these conflicts can be seen in the present study of currently available waste forms. The MWFA is developing and proposing technological methods to convert EM's mixed inventory into stable waste forms for disposal on a time schedule to meet the EM's "Paths to Closure" commitments. However, many of the disposal sites that will receive mixed waste forms, waste acceptance criteria, and the actual disposal conditions for the waste forms are unspecified. A
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--> comprehensive systems approach must recognize these complicating, but real, factors. Waste Characterization The committee found that EM's mixed waste inventory is sufficiently well characterized for conceptual design of treatment processes but insufficiently characterized for detailed engineering design or process optimization. Detailed characterization, using currently available methods, will be expensive and may entail risks to operating personnel. The Committee has three recommendations: The MWFA should develop simplified methods to characterize the waste inventory, with emphasis on nondestructive examination and nondestructive assay techniques. Emphasis should be placed on developing better methods to determine heavy metals and solvent contamination. The MWFA should continue to develop, demonstrate and encourage deployment of techniques and procedures to ensure that all new waste streams are adequately characterized. The MWFA should strive for a balance between the risks, benefits, and cost of detailed characterization and the effort and cost to develop more robust treatment technologies that can handle a wide variety of waste compositions, thus reducing the required degree of waste characterization. There are two possible pathways to reduce costs and risks for which R&D would be valuable. The first is for simplified methods of examining and characterizing wastes through such vehicles as rapid scanning, non-intrusive identification of constituents. The other pathway is through development of robust treatment technologies that can adequately deal with a variety of feed materials, thereby reducing the need for extensive characterization. The committee noted that the MWFA's recent experience in developing "universal" treatment tech-
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--> nologies, such as the plasma torch, showed that these technologies still require adjustment according to waste composition. The committee therefore emphasizes the importance of waste characterization and encourages the MWFA to seek a reasonable balance in the development of characterization and treatment technologies. The committee recognizes the difficulties in determining the composition of mixed wastes when the waste is stored in many forms or in sealed containers. Detection and determination of some of the radioactive constituents by non-intrusive means is readily accomplished. Similar detection and determination of 'silent' hazardous materials such as toxic organic compounds and metals or characteristic waste components that could pose processing problems during the generation of acceptable waste forms continues to represent a major theoretical and practical challenge. The committee believes research efforts devoted to this problem could pay significant dividends, particularly in reducing the quantity of waste that must be treated as mixed waste that is, waste minimization. However, the committee also believes that the development of robust and comprehensive processing techniques that are insensitive to waste composition and yield satisfactory waste forms when the feed to the process is only poorly characterized should also be pursued. Treatment Technologies In its Technical Baseline Report, MWFA has drawn up process diagrams that conceptualize treatment for the majority of its varied waste streams. This effort has defined potential treatment systems and their final waste forms to meet the present regulations governing mixed wastes. In addition, volume reduction, cost reduction, and suitability for transportation have also been objectives of the work. The committee found that there are ample treatment technologies and waste forms for EM's mixed waste inventory. However, many of these technologies have not been demonstrated as part of an integrated production-scale system using actual wastes.
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--> The Committee has four recommendations: MWFA should integrate treatment technologies for its five treatment groups into a mixed waste treatment strategy. This strategy should consider the waste form as a part of an overall mixed waste management system that includes the following: compatibility of waste form with transportation and disposal options, trade-offs between risks to personnel associated with additional waste characterization and additional costs of a more robust treatment and stabilization system, and trade-offs between the increased number of disposal options for a very stable waste form, versus the lower costs but reduced disposal options for less stable waste forms. MWFA should demonstrate new treatment technologies on at least the pilot plant scale using real wastes or realistic surrogates before the technology is designated as ready for deployment. MWFA should continue to address technology deficiencies that it has identified through input from the Site Technology Coordinating Groups and update its Technical Baseline Report to reflect progress in addressing these deficiencies. MWFA should continue to provide research funding for developing robust processes that can treat and stabilize waste of poorly defined or variable composition, recognizing the trade-off between better waste characterization and development of improved treatment technology. The need for a treatment strategy follows from the committee's overall recommendation that MWFA adopt a more complete systems approach to its technology development, and from the committee's recognition of the trade-offs between the difficulties of developing broadly targeted, robust treatment technologies, and the potential risks to operators in sampling and analyzing the many and varied wastes that comprise the inventory. These were discussed in Chapter 2 and in the
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--> preceding recommendations on waste characterization. Trade-offs between grout and higher quality vitreous forms that are generally harder to make, as discussed in Chapter 4, are also recognized by the committee. The committee noted that the present plan for the privatized Advanced Mixed Waste Treatment Project is to produce grout forms, whereas early presentations by MWFA indicated that glass waste forms would also be produced. The necessary technology demonstrations that are being planned at several DOE sites will inevitably be constrained by time and budgets. Such constraints can set the stage for later technology failures if larger scale testing is not done with careful planning, care, and diligence. For example, process steps should be thoroughly tested and evaluated before any radioactive materials enter a new facility. The final products should be extensively analyzed to avoid such issues as inadequate waste form performance because of unexpected variations in feedstock composition. The MWFA should play an important role as a technology advisor during this very important demonstration phase. MWFA should also remain closely involved in the technology deployment phase to ensure successful technology transfer to the DOE sites or private contractors. Waste Form Characterization and Performance Assessment To determine if current waste forms are sufficiently developed to stabilize EM's inventory of mixed waste, test protocols to characterize the waste forms must be available. The committee found no established tests that can demonstrate the long-term (greater than a few hundred years) behavior of a waste form; however, present methods are adequate to evaluate short-term behavior. Performance assessment (PA) is required by the U.S. Nuclear Regulatory Commission (USNRC) to evaluate the long-term safety of waste disposal facilities. The committee found that current PA methodology does not recognize the significance of the waste form or take reasonable credit for the waste form's ability to reduce the release rate of hazardous and radioactive constituents. This is mainly because of the lack of methods to quantify the long-term behavior of waste forms.
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--> The committee's four recommendations in the areas of characterization and performance assessment are directed to OST because the recommendations apply to all DOE wastes: OST should continue to support programs aimed at fundamental understanding of waste form durability and degradation processes. These programs should lead to a better representation of the waste form in PA modeling. OST should work to promote consensus among the U.S. Environmental Protection Agency (EPA), USNRC, DOE, and the scientific community on waste form testing methods that will be generally acceptable for providing at least a qualitative evaluation of long-term waste form performance in disposal environments. OST should support efforts to obtain data that will allow a more realistic inclusion of waste forms in PA models, including inadvertent intrusion scenarios. Without such data the waste form will never receive proper credit in PA with the resulting cost penalties for additional engineered barriers and possible restriction in site selection. OST should play a more significant role in promoting (funding) cooperation among investigators who are characterizing waste forms and those who are developing PA models to help ensure that characterization data are useful for PA models, and that PA models properly incorporate this data. The credibility of performance assessments can be enhanced by better representation of waste form behavior in the disposal environment. More realistic assessments might allow more effective use of the capacity of disposal facilities by allowing them to accept a larger inventory of radionuclides or hazardous wastes. The EM Science Program (NRC, 1997) could provide a valuable mechanism for evaluating and funding research proposals for the fundamental studies recommended by the committee.
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--> Regulatory Guidelines The lack of available, licensed disposal sites for mixed waste and uncertainties in the waste acceptance criteria of future sites introduce a significant risk in judging the adequacy of EM's planned mixed waste treatments and waste forms. The committee recommends that EM work with EPA and the USNRC to agree on clear guidelines that describe acceptable waste forms for disposal of mixed waste in future, near-surface disposal facilities. This should be done as soon as possible to reduce the risk of EM deploying technologies that are later judged inadequate because of unanticipated regulatory requirements.
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