Research Opportunities for Managing the Department of Energy's Transuranic and Mixed Wastes (2002) / Chapter Skim
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3 Research Needs and Opportunities
3 Research Needs and Opportunities
Pages 35-74
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From page 35... ...
, the committee concluded that the most significant needs and opportunities lie in · waste characterization and how waste characteristics may change with time, · location and retrieval of buried wastes, · waste treatment, and · Iong-term monitoring. The committee has been selective in its recommendations to encourage the EMSP to concentrate its limited funding in a few specific areas where the committee believes research can lead to the most significant improvements.
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Most transuranic and mixed wastes (TM wastes) are packaged in 55gallon drums hundreds of thousands of them as noted in Chapter 2.
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, the current baseline requires the same characterization steps as CH-TRU. DOE is seeking to change this requirement because of the difficulty of making such detailed characterization in remotely operated facilities and the increased risks of worker exposure (NRC, 2002b)
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and to provide characterization information on the waste constituents.The DOE Carlsbad Area Office and the EPA use acceptable knowledge documentation to certify each waste stream (i.e., waste-generating process)
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DOE proposed that 2 percent of the initial population of containers of each waste stream be examined visually, and if these evaluations resulted in few miscertifications, then the percentage of subsequent waste containers to undergo visual examination would be reduced. In October 1999, New Mexico in its Resource Conservation and Recovery Act (RCRA)
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DOE wou Id I Ike to simpl ify the characterization basel ine for TRU wastes in order to increase the rate of shipping these wastes to WIPP. The main approach is to seek changes in current transportation and disposal requirements, for example, to reduce the many detailed characterization steps illustrated in Sidebar 3.1.
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28) involve research to reduce uncertainties in waste and system performance driving conservatism in characterization and transportation requirements for TRU wastes.
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Conversely, much has been done toward characterizing and exploiting the microbiota of more traditional hazardous wastes, resulting in significant cost savings over traditional disposal and remediation technologies (Harkness, 2000; Steffan et al., 2000~. Microbial effects may be important in organic materials stored for long periods or in mixed waste landfills.
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Neutron activation analysis, however, suffers from the same turnaround, expense, calibration, and inhomogeneity problems associated with gamma-ray spectroscopy. Neutron activation analysis C h a p t e r 3 43
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DOE is presently developing new technologies for facility deactivation and decommissioning and subsurface contamination applications that are equally relevant for the characterization of containerized waste. Examples include portable "laboratory-on-a-chip" sensor technology for the quantitative identification of radionuclides and metals such as uranium, plutonium, cesium, strontium, mercury, and lead (Collins and Lin, 2001; Collins et al., 2002~; the microcantilever sensor array technology for real-time characterization of the chemical, physical, and radiological content of ground water and mixed waste (li et al., 2000, 2001~; and the micro-chemical sensor for in situ monitoring and characterization of volatile contaminants (Ho et al., 2001~.
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Research Opportunities Research opportunities include noninvasive standoff imaging and image recognition methods and in-drum sensors to provide faster and more sensitive technologies for waste characterization. Research to develop predictive models of how waste characteristics may change with time, including microbial effects, can reduce the need for detailed waste analysis and provide better decision-making tools for storing, shipping, and disposing of TM wastes.
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When compared to conventional analytical methods that require withdrawing a sample, in situ probes could improve the speed of data acquisition and reduce associated secondary waste streams from the laboratory analyses. Examples of such probes could include fiber-optic windows for optical or spectroscopic characterization of drum contents ("optrode" approaches have been developed at Lawrence Livermore National Laboratory)
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L) Research also should evaluate the effects of microbial activity on waste forms for disposal, including polymers and grouts, macroencapsu ration matrices, and containers.
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Predictive Modeling One of the most beneficial cost-saving tools in the management of TM wastes would be the formulation of more reliable predictive models of how waste characteristics may change with time, well validated by experimental data. Ideally, models could predict such factors as gas generation rates (e.g., matrix effects on rates of radiolysis, microbial effects)
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This research should emphasize remote imaging and sensing technologies to locate and identify buried waste and retrieval methods that enhance worker safety. Substantial quantities of TRU waste were disposed in near-surface excavations (shallow land disposal)
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Challenges for Next-Generation Retrieval Technologies From its fact-finding visits to DOE sites and committee members' experience and judgment, the committee believes that the greatest challenges for the next generation of waste retrieval technologies will be to provide '2A recent report on remediating a waste site at Sandia National Laboratories stated "the largely unknown characteristics of the buried waste material created uncertainties that could only be addressed during the excavation, rather than during the planning stages" (Methvin, 2002, p.1)
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There is a specific need for robotic technology to retrieve RH-TRU wastes, some of which produce potentially lethal levels of radiation, from caissons located in the Hanford 618-11 waste burial grounds (Leery, 2002~. One of the best examples of next-generation robotics technology that might be further developed to retrieve buried waste drums is the HAN DSS-55 system being assembled by the TMFA (see Sidebar 3.5~.
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Wastes from other DOE sites were also buried there, including transuranic waste from Rocky Flats. Wastes were disposed in pits, trenches, soil vaults, an above-ground disposal pad, a transuranic storage area release site, and three septic tanks.
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are available for quick identification of contaminants and they eliminate the need for sample collection and laboratory work.The SAMS radiation detection system provides real-time isotope analysis in addition to radiation field strengths. Following excavation of the desired materials, automated radiation survey systems deployed either from the excavator or by other remotely operated devices are planned to perform detailed surveys of the excavated pit to allow proper backfilling and monitoring.
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, or by other technologies (e.g., acoustic or seismic, biosensors, neutron activation analysis, trace vapor)
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HANDSS-55 is being developed at the Savannah River Site, which has about 10,000 drums of Pu-238 and Pu-239 waste that must be handled in a contained facility for contamination control. The HANDSS-55 system remotely opens 55-gallon drums and their polyethylene liners, gains access to the waste, removes items that are noncompliant for shipment to WIPP, and repackages the waste into polyethylene canisters.The used drums are shredded.
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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.
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. Baseline Technologies and Technology Gaps For TRU waste that does not meet shipping requirements, the baseline treatment is repackaging the waste.
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Macro- and microencapsulation have become important baseline technologies for waste stabilization, i.e., treatment to prepare wastes for further handling or disposal (see Figure 3.3~. Stabilization of mixed waste for disposal usually relies on its incorporation into one of several matrices grouts or cements, glass, polymer, or ceramic to produce a relatively homogeneous waste form, although some wastes are simply compacted.34 Macroencapsulation yields a heterogeneous waste form '4Matrices for stabilizing TM wastes ("waste forms")
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as feed for the extruder to produce pellets of intimately mixed waste and matrix. Versions of these technologies are used to stabilize approximately 20 percent of the waste requiring treatment for disposal at Envirocare, Utah.
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Gases that are released are usually condensed or trapped, for example, on carbon. Thermal Resorption is among the three leading options recommended as alternatives to incineration by the Blue Ribbon Panel, although the technology does not apply to all types of TM waste or reduce the waste volume (see Appendix C)
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Mercury is present in a broad range of concentrations in several of DOE's mixed waste streams, including large volumes of soil and debris and several types of process residues (see Table 2.3~. Because it is mobile and easily vaporized, the presence of mercury creates additional effluent monitoring and control concerns in incineration and can reduce the efficiency of MLLW stabiI ization processes.
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Challenges for Next-Generation Treatment Technologies Based on the committee's fact-finding visits to DOE sites, recent approaches to developing alternatives to incineration, and committee members' own expertise, the committee believes that the greatest challengesfornext-generationtreatmenttechnologieslieindeveloping . emission-free treatment processes, · treatments for problematic or unique wastes, and · methods to ensure the long-term durability of stabilized waste.
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During its visit to Oak Ridge's isotope production facility the committee was reminded that greater efficiency in separating highly radioactive products means a less radioactive and easier-to-manage waste stream. Understanding factors that affect durability of matrices for mixed wastes disposed in near-surface, RCRA-compliant landfills will be especially important as DOE moves its MLLW from storage to disposal in site closures.
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, biological treatments, stabi I Cation, and waste form d u rabi I ity. Chemical Treatment Essential to developing publicly acceptable alternatives to incineration is research to develop sensitive, reliable, and practical detection methods to track both radionuclide and hazardous chemical materials during the treatment processes.
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This raises several interesting technical challenges, such as ensuring efficient removal of finely divided powders, controlling particle dispersion and perhaps inducing agglomeration, and avoiding the generation of additional waste streams. Hydrogen generation remains a factor in the shipment of containerized waste to WIPP.
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Fundamental research may identify biological treatment processes that can facilitate the removal of RCRA wastes (e.g., Hg, Pb) and radioactive metals from contaminated media.
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ng TM wastes. Biotechnology research opportunities include the identification and development of improved hydrogen and methane scavengers that can be added to waste drums.
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Promising biocatalysts may be obtained by applying traditional microbial selection and enrichment approaches to target waste materials or by "biomining" other radioactive waste materials to identify promising radiation-resistant degradative microbes. Genetic engineering could be applied to improve the metabolic capabilities of radiation-resistant organisms to develop improved biocatalysts for treating mixed waste (Brim et al., 2000; Lange et al., 1998~.
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Long-Term Monitoring The EMSP should support research to improve long-term monitoring of stored and disposed TRY 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.
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O O Challenges for Next-Generation Technologies Based on its fact-finding visits to DOE sites and committee members' own expertise and judgment, the committee believes that future challenges for long-term monitoring technologies will be to extend the next-generation technologies described in the section on characterization to enhance reliability, stability, and remote operation, including long-lived, reliable sensors (and power supplies) that can be remotely interrogated, and airborne or satellite imaging.
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These needs include environmental and safety monitoring, preventive maintenance, global positioning, antitheft measures, and real-time engine sensor data. Platform mobility and the lack of cost-effective wireless connections have been the limiting factors in developing sensor systems for mobile platform services.
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The Internet and wireless technologies can monitor these and other distributed sensors remotely during all phases of waste disposition, including storage, transportation, and disposal. The availability of inexpensive and reliable sensors for chemical and radiological hazards in the drums would also be beneficial.
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A better understanding of these microbes and their activities will help predict the long-term fate of the different waste forms and their components. Microbial activity may destroy or immobilize some waste components while increasing the motility or toxicity of others.
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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.
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