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Research Opportunities for Managing the Department of Energy’s Transuranic and Mixed Wastes Executive Summary The National Academies’ National Research Council (NRC) undertook this study to provide advice to the Department of Energy’s (DOE’s) Environmental Management Science Program on a long-term research agenda for managing and disposing of transuranic and mixed wastes. DOE’s inventory of transuranic and mixed wastes (TM wastes) includes about 155,000 cubic meters of waste stored on some 30 DOE sites and another 450,000 cubic meters of buried waste—at least some of which is likely to require retrieval in the course of DOE’s site cleanup program. Most of the stored inventory is in 55-gallon drums or other containers.1 Although some of the buried waste is similarly packaged, knowledge of the condition of the containers and their contents is limited. While DOE is making a concerted effort to accelerate the removal of TM wastes from its sites, the size of the inventory translates to a multi-decade effort that will require handling, characterizing, shipping, and disposing of hundreds of thousands of waste drums and other containers at a total cost of billions of dollars. Thus, there are sufficient time and strong incentives—safety, cost, and efficiency—for research toward developing new technologies for managing DOE’s TM wastes and improving the scientific basis for public and regulatory decision making. Transuranic (TRU) wastes comprise a variety of waste materials (e.g., trash, equipment, soil, sludge) that are contaminated with plutonium or other transuranic isotopes. Mixed low-level waste (MLLW) is similar to TRU waste except it contains small amounts of radioactive fission products as well as substances designated as hazardous by the Environmental Protection Agency (EPA). TRU wastes are intended for disposal at the Waste Isolation Pilot Plant (WIPP), which is in a deep salt formation in 1 One cubic meter is equivalent in volume to five 55-gallon (200-liter) drums, so the stored inventory amounts to about three-quarters of a million drums.
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Research Opportunities for Managing the Department of Energy’s Transuranic and Mixed Wastes southeastern New Mexico. MLLW can be disposed in facilities at or near the earth’s surface that are constructed in compliance with EPA and other applicable regulations. In 1995, Congress chartered the Environmental Management Science Program (EMSP) to bring the nation’s scientific capability to bear on the difficult, long-term cleanup challenges facing DOE. To fulfill its charter, the EMSP solicits proposals and selectively funds research on problems relevant to the needs of DOE’s Office of Environmental Management (EM). The objective of this study is to provide recommendations to the EMSP for the development of a research agenda to address challenges in managing TM wastes that are currently stored at DOE sites or will be produced as part of DOE’s site cleanup program. When this study was in its closing phases, DOE’s Office of Environmental Management completed a “top-to-bottom” review, which will result in significant changes within EM and its Office of Science and Technology (OST), the sponsor of this study, to be effective at the beginning of fiscal year 2003. The five OST focus areas—including the Transuranic and Mixed Waste Focus Area (TMFA)—around which OST had previously organized its research and development activities will be abolished and replaced by two science and technology “thrusts.” The EMSP will be removed entirely from EM and placed in the Office of Biological and Environmental Research within DOE’s Office of Science. The committee2 did not attempt to assess the effects that this reorganization will have on the EMSP. However, the committee did note that the TMFA provided much of the technology needs and development information used in preparing this report. Without the focus area structure it may be more difficult for the EMSP to identify site technology needs and, especially, to keep a perspective on long-term needs that can be addressed through scientific research. Maintaining the relevance of its funded research to site cleanup needs will be important for the EMSP after the reorganization is completed in fiscal year 2003—for example, by continuing the joint review of research proposals by both OST for relevance to EM’s needs and the Office of Science for scientific merit (see Appendix A). 2 The Committee on Long-Term Research Needs for Managing Transuranic and Mixed Wastes at Department of Energy Sites, which developed this report, is referred to as “the committee” throughout. The committee completed its work in May 2002, about five months before the reorganization was to be finalized.
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Research Opportunities for Managing the Department of Energy’s Transuranic and Mixed Wastes Challenges Radioactive waste materials began accumulating in the 1940s with the development of the atomic bomb and continued through the Cold War. Although DOE has halted its production activities, TM wastes continue to accumulate, albeit at a slower rate, mainly from site cleanup and deactivation and decommissioning activities. The challenges in managing and disposing TM wastes are largely attributable to the following: a large and highly diverse waste inventory, which is incompletely characterized; complex and evolving regulatory constraints from various agencies; and public concern and often opposition to technologies that are unfamiliar or that might change agreed-upon cleanup plans. These challenges will affect the priorities of any research agenda developed by the EMSP. DOE’s greatest technical challenges for managing and disposing of its TM wastes arise from the sheer size of the inventory—characterizing the contents of hundreds of thousands of waste containers, retrieving at least a portion of buried wastes, providing treatments as necessary, and shipping the wastes to designated disposal facilities. The number of regulatory agencies and myriad applicable rules can produce conflicting or excessive requirements that lead to delays and increase costs. DOE has begun seeking regulatory changes in several specific instances (see Chapter 2). Public opposition to incineration, the technology DOE intended to use to treat a large portion of its TM wastes, has forced DOE to seek alternatives. From these challenges, two clear roles for EMSP research arise: To provide the scientific basis for new technologies that will be necessary for improving management and disposal of TM wastes during the next 20 years, especially if regulatory changes that DOE expects to simplify dealing with problematic wastes are not forthcoming. To enhance the scientific information available for regulatory decision making and public involvement, including evidence that disposal systems are operating as intended.
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Research Opportunities for Managing the Department of Energy’s Transuranic and Mixed Wastes Findings and Research Recommendations After visiting DOE sites, considering the views expressed by a wide range of participants, and conducting internal deliberations, the committee concluded that the most significant research needs and opportunities lie in waste characterization and how the waste characteristics may change with time, location and retrieval of buried wastes, waste treatment, and long-term monitoring. The committee has been selective in its recommendations to encourage concentration of limited funding to a few specific areas believed to make the most significant contributions to meeting future waste challenges. The recommendations were developed from presentations to the committee, site needs, apparent knowledge gaps, the potential for future cost and schedule savings, and the possibility of achieving technological breakthroughs. These recommendations deliberately were cast to reflect the goals of the research rather than what research is to be done. The latter is better left to the ingenuity of the scientists who will submit EMSP proposals. Characterization The EMSP should support research to improve the efficiency of characterizing DOE’s TRU and mixed waste inventory. This should include research toward developing faster and more sensitive characterization and analysis tools to reduce costs and accelerate throughput. It should also include research to develop a fuller understanding of how waste characteristics may change with time (chemical, biological, radiological, and physical processes) to aid in decision making about disposition paths and to simplify the demonstration of regulatory compliance. Determining the physical, chemical, and radiological properties of TM wastes pertinent to handling, processing, transportation, and storage is costly and time-consuming. The problem is amplified by the wide variety of the wastes and their heterogeneity. Improving and simplifying waste characterization can reduce costs and increase the rate of shipping wastes to disposal facilities. The committee found needs for faster and more sensitive characterization technologies, for making automated sampling more reliable, and
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Research Opportunities for Managing the Department of Energy’s Transuranic and Mixed Wastes for improving statistical sampling methods. There is a lack in basic knowledge of how waste characteristics may change with time, including both short-term changes that affect storage and shipment and long-term changes that may occur in a disposal facility. This lack of knowledge drives conservatism in characterization, transportation, and disposal requirements. Possible microbial effects in waste have generally been ignored. The committee believes that the greatest challenges for the next generation of characterization technologies will be to provide the following: more rapid, automated nondestructive assay and evaluation methods; more sensitive nondestructive assay and evaluation technologies for larger containers and hard-to-detect contaminants; and improved methods, based on fundamental modeling, to derive present and future waste characteristics from a limited number of sampling parameters. Research toward new, noninvasive, remote imaging and image recognition methods and in-drum sensors to provide faster and more sensitive technologies for characterization could lead to significant savings in time, cost, and risk of worker exposure. While noninvasive diagnostics are ideal, the use of minimally invasive sensors also has promise. Research on microbial activity in TM waste may lead to new ways to control long-term changes in waste stability or toxicity. One of the most beneficial cost-saving tools would be the formulation of more reliable predictive models, validated by experimental data, of how waste characteristics may change with time. This would be most useful in predicting deleterious processes that might occur in the waste, such as gas generation or matrix degradation. Retrieval of Buried Waste The EMSP should support research that will facilitate management of buried TRU and mixed waste in anticipation that retrieval of some waste will become necessary. This research should emphasize remote imaging and sensing technologies to locate and identify buried waste and retrieval methods that enhance worker safety. Given the complex and changing nature of regulatory requirements and public perception, the committee believes that some buried wastes are likely to be retrieved in the future. Burial was largely in near-surface excavations—some wastes in containers and some in bulk.
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Research Opportunities for Managing the Department of Energy’s Transuranic and Mixed Wastes The committee believes that the greatest challenges for the next generation of retrieval technologies will be to provide improved, noninvasive means to locate and identify buried waste whether or not it is containerized; remote, noninvasive assessment of the condition of waste containers and of potential leakage from the containers; and remote intelligent machines (robots) for waste retrieval and repackaging or treatment as necessary. Before buried waste can be retrieved, it must be located and its condition determined. Determining the integrity of a waste container prior to retrieval extends the challenges of imaging science to objects below ground. In addition to improving image resolution, research is needed to improve identification of the object, the surrounding contamination, and the stability of the contaminants. Intact drums could be retrieved and characterized using the processes developed for stored waste; however, it would be preferable to perform characterization at the burial site as each drum is retrieved to minimize handling and ensure worker safety. Robotic devices would help protect workers by handling containers that emit radiation or have been breached and have radioactive contamination on their surface or in the surrounding soil. Microorganisms can have a profound impact on the chemistry and fate of buried waste. Although many biological studies have focused on a better understanding of the environmental fate of radioactive and toxic metals, few studies have investigated the complex relationships among microbes and the organic and inorganic constituents of TM waste. Understanding these relationships could lead to improved predictability of the long-term fate and risk of the waste materials. Treatment The EMSP should support research for treating TRU and mixed waste to facilitate disposal. This research should include processes to simplify or stabilize waste, with emphasis on improving metal separations, eliminating incinerator emissions, and enabling alternative organic destruction methods. Treatment includes operations intended to improve the safety and/or economy of managing waste by changing the characteristics of the waste—volume reduction, removal of radionuclides or other contaminants, and altering the waste composition. Treatment is necessary if
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Research Opportunities for Managing the Department of Energy’s Transuranic and Mixed Wastes waste does not meet shipping requirements or acceptance criteria at the intended disposal site. In the absence of effective treatment technologies, waste is simply repackaged to avoid the problem. Repackaging waste in order to meet shipping requirements is extremely inefficient, may increase volume manyfold, and presents hazards to workers. Phasing out incineration for the destruction of organic constituents requires the development of alternative technologies. Wastes classed as unique or problematic— including reactive materials, gas cylinders, and tritium-contaminated materials—comprise only about 10 percent of the inventory. They are often overlooked in site cleanup contracts, but they deserve special attention for research because some will be difficult to treat and may eventually become roadblocks to site closure. Application of biotechnologies for treating wastes has been largely overlooked. The committee believes that the greatest challenges for the next generation of treatment technologies lie in developing emission-free treatment processes, treatments for problematic or unique wastes, and methods to ensure the long-term durability of stabilized waste. Opportunities for basic research lie in chemical treatment, biological treatment, and waste stabilization. For chemical treatment, understanding the speciation of inorganic constituents, oxide-substrate interactions, and mechanisms of gas production and adsorption (especially hydrogen) is fundamental. In the biological area, research should include enzymatic or whole-cell approaches that target specific or broad categories of contaminants, biotransformations for removing mercury and heavy metals, bioaugmentation or biostimulation to remediate actinide-impacted soils, and development of hydrogen and methane scavengers. In the stabilization area, research should address new approaches to stabilizing buried waste prior to or in the early stages of excavation, smart materials that react with waste constituents, and very long term barriers against contaminant migration and methods to prove their longevity. Public concern about air emissions from incineration has created incentives for applied research toward large-volume, robust alternatives that are emission free, as well as to smaller-scale, portable devices that may have specialized applications. There are also opportunities to develop more efficient processes that yield smaller or easier-to-manage waste streams from DOE’s ongoing activities (e.g., isotope production, generation of secondary wastes from high-level waste processing, facility deactivation and decontamination).
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Research Opportunities for Managing the Department of Energy’s Transuranic and Mixed Wastes Long-Term Monitoring The EMSP should support research to improve long-term monitoring of stored and disposed TRU and mixed wastes. Research should emphasize remote methods that will help verify that the storage or disposal facility works as intended over the long term, provide data for improved waste isolation systems, and inform stewardship decisions. To ensure safety, wastes and the facilities that house them have to be monitored. This includes monitoring during storage, which could continue for decades for some wastes, and during the operating life of the disposal facility. For example, substantial deformation of the salt will occur during the operational phase of WIPP, and monitoring can help DOE understand and verify how lithostatic forces will seal the disposal rooms. Very long term monitoring will continue after the disposal facility is closed. DOE appears to have no firm plans for long-term monitoring of stored or disposed wastes. Research begun now can lead to reliable, cost-effective monitoring devices and methods. Data from monitoring can help ensure safety, reassure concerned citizens, and assist in the development of new disposal facilities. The committee believes that the greatest challenges for the next generation of monitoring technologies lie in providing long-lived, reliable sensors (and power supplies) that can be remotely interrogated, and airborne or satellite imaging. Research opportunities exist, for example, in developing smart sensors that self-analyze and report drum location and contents, and smart filters that monitor the type and amount of gas produced in a drum. In addition to being a repository, WIPP can be an important laboratory for repository science and sensor technology. Research should focus on potential biodegradation of the various organic components, reactions altering the geochemistry of the inorganic compounds, biogeochemical factors that affect leaching or migration of toxic and radioactive materials, and the effect of physical conditions and chemical composition on the biogeochemical processes occurring in the waste. Concluding Comments Accelerating site closure, a key feature of EM’s planning since the 1990s, has been emphasized by EM’s top-to-bottom review. DOE is
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Research Opportunities for Managing the Department of Energy’s Transuranic and Mixed Wastes presently making a concerted effort to remove TM wastes from its sites as rapidly as possible. Among the areas for EMSP research recommended by the committee, research in characterization that would expedite shipping wastes for off-site disposal is most likely to provide immediate payoffs. Research toward methods for treating wastes that do not meet shipping or disposal criteria might provide similar near-term payoffs. Nevertheless, closing the larger DOE sites will require decades. Problems that are not foreseen or appreciated today are likely to be encountered in buried waste retrievals. Monitoring WIPP during its operational period is a unique scientific opportunity. Demonstrating that WIPP behaves as expected could be invaluable as DOE seeks to open other geological waste repositories. Buried waste retrieval and monitoring of disposal facilities provide opportunities for the long-term, breakthrough research envisioned by Congress, and these opportunities should not be overlooked in DOE’s rush to meet short-term needs.
Representative terms from entire chapter: