Research Opportunities for Deactivating and Decommissioning Department of Energy Facilities (2001) / Chapter Skim
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4. Research Recommendations
4. Research Recommendations
Pages 49-70
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From page 49... ...
problems not addressed effectively by existing technologies. Based on its discussion of future D&D challenges and their underlying causes in Chapter 2, the committee concluded that the most significant needs and opportunities lie in the characterization and decontamination steps of the D&D process, robotics and intelligent machines to enhance worker safety, and the scientific basis for determining objectives of a D&D project (facility end states)
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The committee has three recommendations for research that could lead to new or improved methods of characterizing the contaminated construction materials that are found in most obsolete DOE facilities: characterization of surfaces, characterization beneath surfaces (depth profiling) , and remote mapping of contamination.
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The greatest opportunities for research are in characterizing surfaces bearing very low levels of radionuclide and chemical contamination. For example, before these materials can be disposed of, they must first be characterized and, if certified to be below a derived concentration guideline level (DCGL)
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Analytical chemistry methods Modern methods of chemical analysis that can detect small numbers of molecules are often capable of measuring far lower concentrations of radionuclides than direct radiation measurements.3 There are opportunities for research to extend analytical chemistry methods to develop more sensitive methods to measure small amounts of long-lived radionucl ides. Laser ablation mass spectroscopy (LA/MS)
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Such sensing materials might be fabricated into visual color test strips or luminescent smears to sensitively and selectively report on the concentration and identity of both chemical and radioactive contaminants, including lead, uranium, plutonium, strontium, cesium, and cobalt (Asher, 2000~. Nanosensors Nanotechnology wil I have a significant impact on many aspects of science and technology,4 and the committee believes that research in support of nanotechnology development deserves special attention by the EMSP.
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Analytes measurable by biosensors include a vast array of organic chemicals, biochemicals inorganics, and metals and more recently ionizing radiation (Lee et al., 2000~. There are research opportunities to fundamentally develop and evaluate biosensor organisms to detect radionuclides and chemicals that are important for D&D applications.
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Bionanosensors are recognized as a key research area in the National Science Foundation's first call for proposals related to the National Nanotechnology Initiative.5 Such technology could create new capacity for continuous and remote monitoring in chemically and physically complex environmental and structural systems characteristic of DOE's site D&D needs. Profiling Construction Materials The committee recommends basic research leading to development of real-time and minimally invasive methods to characterize radionuclides and EPA-/isted substances as a function of depth in construction materials, especially concrete.
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Research to extend laser ablation mass spectroscopy (LA-MS) along the lines described under characterization of surfaces is one example (Van Hecke and KaruLstis, 1998~.
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Opportunities The committee believes that current technology for remote mapping can be significantly advanced by research in new detector materials, fiber optics, and fiber optic-based dosimeters. Detector materials There are research opportunities to discover or synthesize new detector materials to overcome current limitations (Squillante and Shah, 1995;EntineandSquillante,1999~.1ngeneral,agoodmaterialmustbe readily available in high-quality crystal form and be compatible with electronic device fabrication procedures.
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Fiber optic radiation sensors Remote sensing of radiation using optical fibers as the detector material and a conduit for transmitting accumulated dose information is a recent development (Herschel et al., 1994; Huston et al., 1996; Borgermans et al., 2000~. Opportunities exist for both improved performance and such novel features as optical interrogation (Miller et al., 2000~.
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. Improvements in both materials and analysis methods are required to develop reliable, robust fiber optic dosimeters for DOE radiation man itoring activities.
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For large-scale applications, almost all current decontamination methods are time consuming, i evolve risks to \/vorkers, produce sign if icant volumes of secondary waste, and often leave residual contamination, especially actinide contamination. They usually require direct, hands-on work such as the concrete spelling work shown on the front cover of this report.
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Contaminated materials include glove boxes, shielded cell liners, concrete, lead bricks, lead glass, and plastics. Radioactively contaminated lead, which is also chemically toxic, is a particular challenge.
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Beyond their use in decontamination the models can help provide a more general scientific basis for predicting behavior of contaminants in construction materials as a scientific underpinning of facility end states, which are described in the final recommendation in this chapter. Biological Processes The committee recommends basic research on biotechnological means to remove contaminants from surfaces and from within porous materials found in surplus DOE facilities.
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Metal-rich ore differs significantly from concrete because the pH of the ore leaching solution is relatively easily maintained at pH <2. Concrete, being highly alkaline and buffered, poses difficulty for establishment of sulfuroxidation-driven bioleaching, but alkali-tolerant strains of Thiobacillus have demonstrated potential.
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Similarly, a variety of hazardous contaminants (e.g., PCBs, TCE, and perchloroethylene) can be independently or cooperatively degraded by joint aerobic and anaerobic bacterial processes with or without synergistic action of physical-chemical treatment, such as photocatalytic oxidation, or Fe++-driven reduction.
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Most D&D baseline technologies require that workers routinely enter areas with radiation and many other industrial safety hazards and perform hands-on work with powerful and heavy equipment, including cutting devices that can instantly penetrate protective clothing. This routine work includes sampling (for characterization)
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Current technology available for D&D is best represented by the Chicago Pile 5 (CP-5) large-scale demonstration of a dual arm robotic system (see Table 3.2~.
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, thus enhancing their safety and productivity. Advances in the state of the art , , , as, for example, in deep sea exploration could improve overall system performance by providing force feedback, remote vision, collision avoidance, and radiation-resistant sensor technology.
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A special need is the kinesthetic interface to human operators to enhance their motor skills and input commands to the remote system. Mobile platforms that in themselves are modular and highly dexterous must be further developed to gain access to the work environment and to transport size-reduced facility components.
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Fate and Behavior of Contaminants in Construction Materials Research should be directed toward understanding the fate and behavior of treated and untreated contaminated material by determining the fundamental chemical species of the contaminants in the host material and how the species behave. The effect of time and changing ambient conditions should be considered in these investigations.
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The use of chemicals or bacteria for decontamination can dramatically affect the local environment by changing pH or inducing chemical reduction or oxidation reactions through respiratory activity. This activity, coupled with physical changes due to material cutting, melting, or polishing from decontamination efforts, can impact the behavior of the contamination.
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