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Advice on the Department of Energy’s Cleanup Technology Roadmap: Gaps and Bridges 2 Principal Science and Technology Gaps The first part of the statement of task for this study requests that the committee identify principal science and technology gaps and their priorities for the cleanup program. Previous National Research Council (NRC) reports have identified science and technology shortcomings using a variety of terms, for example, research needs, technology needs, cleanup challenges, and knowledge gaps (NRC 2007c). To address its task statement, the committee first sought an informative definition of the word “gap” (Figure 2.1). The word “gap” is defined as a “discontinuity between two points” and in this context the task of identifying gaps could be interpreted to mean that the committee is to identify “showstoppers,” that is, cleanup tasks for which there is insufficient knowledge or technology available to do the task. Information provided to the committee by the Office of Environmental Management (EM) and its contractors indicated that, if sufficient time and money were available to overcome cleanup obstacles, there are no showstopper gaps in the cleanup program. Another way of stating this is that EM and its contractors are confident that technologies EM has incorporated into its cleanup plans and schedules (baseline technologies) can be made to work. Nevertheless, the committee observed in its interim report (Appendix H) that the complexity and magnitude of EM’s cleanup task requires the results from a significant, ongoing R&D program if EM is to complete its cleanup mission safely, cost-effectively, and expeditiously. To address its statement of task in a way it judged would be most useful to EM, the committee chose as its working definition that a gap is a shortfall in avail-
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Advice on the Department of Energy’s Cleanup Technology Roadmap: Gaps and Bridges FIGURE 2.1 The word “gap” can be seen as the intersection of several synonyms. SOURCE: Visual Thesaurus: http://www.visualthesaurus.com/. able knowledge or technology that could prevent EM from accomplishing a cleanup task on its expected schedule and/or budget. Following the analogy of a roadmap, a science and technology gap is a “pothole” in the road that EM might somehow work around, but at the likely cost of time and money. It would be much better to fill the pothole or avoid it altogether with appropriate research and development (R&D). Addressing potholes could help EM to avoid large, insurmountable problems by addressing smaller technological challenges that could otherwise aggregate into showstoppers. Smaller investments in developing new science and technology could allow funding for several R&D approaches to a pothole problem, which would be more likely to lead to the most effective solution. Filling potholes before they erode into washouts is a natural role for EM’s longer-term roadmapped research. GAP IDENTIFICATION AND PRIORITIZATION Gap identification began with the committee’s March 2007 workshop and review of earlier Academies’ reports (NRC 2007c), and then proceeded through the committee’s site visits, which are summarized in the appendixes of this report. In this chapter, gaps are set forth as problems or potholes,
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Advice on the Department of Energy’s Cleanup Technology Roadmap: Gaps and Bridges which, if avoided or fixed with new technical tools, could help make the EM cleanup safer, faster, or less expensive. The identification of a gap does not imply that a given baseline technology might not work or should be abandoned—rather the gaps are incentives for EM to apply R&D to improve its available site cleanup and remediation tools. The titles of the gaps are intended to factually state a situation or condition that is less than optimal. The gaps have been identified at a level that the committee believes will provide EM the insights and flexibility to develop and implement effective, bounded, and targeted R&D to fill the gap. EM’s draft Engineering and Technology Roadmap, issued in April 2007, provided a framework for organizing the committee’s fact-finding and deliberations,1 but the committee worked independently of the specific contents on the Roadmap. Factors qualitatively considered when identifying the gaps included: Whether the gap required medium- to long-term R&D,2 The volume of waste affected, Potential to reduce technical risks (including risk to workers), Reduction in schedule uncertainty, Potential cost savings, Likelihood of a successful outcome to the R&D effort, and Possible existence of solutions outside EM. Applying these criteria to information received by the committee led to the general list of about 50 science and technology issues given in Appendix C. Later, through the course of its deliberations, the committee refined this list to the set of 13 principal gaps described in this chapter. In the committee’s judgment, each of these 13 principal gaps could affect the schedule, cost, and risk associated with the EM cleanup program. The priorities of the principal gaps were determined by the committee through an iterative process. During the August 2008 closed session, committee members who initially drafted gap analyses described the attributes of each gap to an “investment committee” composed of three committee members who previously held major programmatic and budgetary responsibilities.3 The three suggested initial gap priorities according to the 1 Essential features of the EM Science and Technology Roadmap are outlined in Chapter 1, Sidebar 1.2. For convenience it will be referred to as the EM roadmap or simply as the Roadmap throughout this report. 2 These time frames are described in Sidebar 1.3. 3 The three members of the investment committee were Carolyn Huntoon, former Department of Energy (DOE) Assistant Secretary for Environmental Management; Edwin Przybylowicz, former vice president for research at Eastman Kodak; and Andrew Sessler, former director of Lawrence Berkeley National Laboratory (LBNL).
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Advice on the Department of Energy’s Cleanup Technology Roadmap: Gaps and Bridges information presented. The full committee then refined the gap analyses, prioritization criteria, and priorities. Gaps were prioritized as high, medium, or low within each program area (Table 2.1). The committee did not attempt to prioritize the gaps across the program areas because the program areas differ fundamentally in the nature of TABLE 2.1 Principal Science and Technology Gaps and Their R&D Priorities Gap Numbera Statement of Gap Priority Roadmap Program Area: Waste Processing WP-1 Substantial amounts of waste may be left in tanks/bins after their cleanout—especially in tanks with obstructions, compromised integrity, or associated piping. High WP-2 Low-activity streams from tank waste processing could contain substantial amounts of radionuclides. Medium WP-3 New facility designs, processes, and operations usually rely on pilot-scale testing with simulated rather than actual wastes. Medium WP-4 Increased vitrification capacity may be needed to meet schedule requirements of EM’s high-level waste programs. High WP-5 The baseline tank waste vitrification process significantly increases the volume of high-level waste to be disposed. Medium WP-6 A variety of wastes and nuclear materials do not yet have a disposition path. Low Roadmap Program Area: Groundwater and Soil Remediation GS-1 The behavior of contaminants in the subsurface is poorly understood. High GS-2 Site and contaminant source characteristics may limit the usefulness of EM’s baseline subsurface remediation technologies. Medium GS-3 The long-term performance of trench caps, liners, and reactive barriers cannot be assessed with current knowledge. Medium GS-4 The long-term ability of cementitious materials to isolate wastes is not demonstrated. High Roadmap Program Area: Facility Deactivation and Decommissioning DD-1 D&D work relies on manual labor for building characterization, equipment removal, and dismantlement. High DD-2 Personal protective equipment tends to be heavy and hot and limits movement of workers. Low DD-3 Removing contamination from building walls, other surfaces, and equipment can be slow and ineffective. Medium aReferred to throughout this report.
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Advice on the Department of Energy’s Cleanup Technology Roadmap: Gaps and Bridges the risks that R&D could mitigate and in their timescales. Establishing their relative priorities involves policy judgments that are outside the committee’s expertise. These differences and trade-offs are elaborated briefly below. Cleanup work that involves only human activities, such as facility construction or demolition, can be accomplished on human-controlled schedules. Groundwater and soil remediation, on the other hand, involve geologic processes that humans can only attempt to control and, generally speaking, operate on a much longer timescale. Priorities for R&D, which typically include schedules and expected payoff, will be different for “engineering-only” projects versus those involving geologic processes (Sidebar 2.1). The ultimate goal of site cleanup is to protect humans and the SIDEBAR 2.1 Timescales for Engineering Projects Versus Geologic Processes A conceptual incongruity exists in the time domains for DOE site cleanup between those activities associated with tank closure, waste separation and processing, and demolition and decommissioning and those activities associated with groundwater and soil contamination, environmental remediation, and long-term site stewardship. The pace of activities associated with the former is limited primarily by budget resources, which are manifested as physical infrastructure, size of the labor force, and availability of chemical and engineering solutions. Public and regulatory policies also modulate the selection and implementation schedules, such as tank closure. On the other hand, activities associated with soil and groundwater protection and cleanup are substantially controlled on a geologic scale by natural process rates and characteristics such as permeability of aquifers and the vadose zone, and the massive volumes of contaminated material (albeit at much lower concentration of problematic toxic organics, metals, and radionuclides than that of the original source materials). Simply put, removing waste from a tank is a straightforward, although complex, engineering challenge that can be addressed as such; soil and groundwater remediation cannot be similarly planned and accomplished. A billion-dollar investment in tank closure or in a waste processing facility is likely to have a dramatic effect within a few years, while a like investment in groundwater remediation may only marginally accelerate the schedule for site cleanup and closure. The end state for the groundwater remediation at a site may be ultimately determined by an acknowledgment and acceptance that the site cannot be returned to a pristine state but that the residual contamination is sufficiently well understood scientifically that the risk to the public, end users, or the environment is acceptable, or can be reduced or controlled at acceptable levels far into the future.
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Advice on the Department of Energy’s Cleanup Technology Roadmap: Gaps and Bridges environment from long-term consequences of the nation’s former production of materials for nuclear weapons. Essentially this means remediating contaminated groundwaters and soils and protecting them from future contamination, which would argue that the higher priorities be given to the groundwater and soil gaps. However, the successful recovery and processing of waste from the former production operations, especially the high-level tank waste, is a prerequisite for preventing additional releases of contamination to the environment—in both the near and long terms. Facility decontamination and demolition, no matter how carefully it is planned and conducted, carries the potential for immediate injury or fatality among workers—as opposed to possible future consequence from groundwater and soil contamination. The program areas are thus intertwined and none rises to a higher priority than the others. SCIENCE AND TECHNOLOGY GAP ANALYSES The science and technology gaps that are presented in the remainder of this chapter are arranged according to the main program areas in the EM roadmap (DOE 2007a, 2008b). Each gap is analyzed in terms of how it is an obstacle for EM, and R&D opportunities to deal with it are described, as follow: An overview of the nature of the gap, The impact the gap has on EM’s cleanup program, The current status of work related to the gap, and Future R&D approaches that EM could consider to help bridge the gap. A table at the end of each gap analysis shows the basis for the committee’s assessment of the gap’s priority. Factors qualitatively assessed for each gap were volume of waste affected, potential to reduce technical uncertainty, potential to affect cleanup schedule, and potential to affect cost. To illustrate how these factors were evaluated, the millions of gallons of high-level tank waste ranked as high in the volume category, as did contaminated groundwater. R&D for gaps that reflected lack of knowledge tended to rate high for reducing technical uncertainty. Schedule and cost reductions are not always correlated, for example, for groundwater and soil remediation or waste treatment processes that are already under way. WASTE PROCESSING The waste processing program area of the EM roadmap deals primarily with high-level tank waste issues, including waste storage, waste retrieval,
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Advice on the Department of Energy’s Cleanup Technology Roadmap: Gaps and Bridges tank closure, waste pretreatment, and waste stabilization. Millions of gallons of high-level waste (HLW) from reprocessing nuclear fuels to recover plutonium and other nuclear materials arose during the Cold War era. Hanford, the first site that reprocessed fuels on an industrial scale, used several different reprocessing technologies that resulted in a variety of waste compositions. The Savannah River Site (SRS) mainly used one type of reprocessing technology and has a relatively smaller spectrum of waste compositions. Reprocessing activities at Idaho were at about one-tenth the scale of those at Hanford or SRS. There were important similarities and differences in waste management practices among these three sites, which are reflected in the science and technology gaps in waste processing identified by the committee and described in this section. Waste Processing Gap 1 (WP-1): Substantial amounts of waste may be left in tanks/bins after their cleanout—especially in tanks with obstructions, compromised integrity, or associated piping. Waste from former weapons material production at the Hanford site (Appendix D) is stored onsite in 149 single-shell (single-walled) and 28 double-shell tanks. The single-shell tanks were constructed between 1943 and 1964. The last of the double-shell tanks was constructed in 1986. All of the double-shell tanks have capacities of 1 million gallons. In total, 133 of the tanks have capacities of 500,000 to 1 million gallons. The Hanford tanks currently hold about 54 million gallons of waste, which contain a total of about 193 million curies of radioactivity (NRC 2006b). Hanford tank waste is very heterogeneous, but generally speaking it consists of supernatant liquid, water-soluble salt cake, and insoluble sludge. These phases resulted from the original acidic reprocessing waste being made alkaline for compatibility with the waste tanks, which were built from carbon steel, and subsequent evaporation of water to reduce the waste volume. The phases are layered and intermixed to varying degrees. Sludge removal is the most difficult. SRS has 49 tanks in service that hold about 36 million gallons of waste containing about 426 million curies of radioactivity (Appendix G). The SRS tanks have a variety of designs—some single-shell, some double-shell, and some with the secondary shell less than the full height of the primary tank (i.e., “cup in a saucer”). The tanks vary in capacity from 750,000 to 1.3 million gallons. Most of the SRS tanks have internal cooling coils that were used to keep the temperature of the waste below boiling (NRC 2006b). SRS tank waste is broadly similar to that at Hanford although it is less heterogeneous chemically (Figure 2.2). Most of the highly radioactive waste at the Idaho National Laboratory (INL) site is in the form of granular solids, which are stored in sets of stain-
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Advice on the Department of Energy’s Cleanup Technology Roadmap: Gaps and Bridges FIGURE 2.2 Sludge sampled from an SRS tank. Tank sludge was formed by neutralizing acidic waste from the reprocessing of nuclear fuels and recovery of nuclear materials. This sludge flowed like a thick paste. Other sludges are more viscous or nearly solid, which makes them difficult to remove from the tanks. This approximately 2-liter sample was opened inside a shielded laboratory cell like that shown in Figure 3.2 in the late 1970s. SOURCE: Department of Energy. less steel bins contained in concrete vaults (Appendix E). The calcine waste exhibits a variety of sizes and compositions. It was originally transferred pneumatically into bins for storage, and DOE plans to retrieve the calcine essentially the same way. However, pneumatic retrieval could be difficult if the calcine has caked (e.g., from moisture in the bins or by particle-to-particle sintering). According to a presentation to the committee during its site visit, INL used a simulated calcine to demonstrate technical approaches for removing the binned calcine (Hagers 2007). The INL site still has about 900,000 gallons of acidic liquid waste stored in three stainless steel underground tanks. According to the Ronald Reagan National Defense Authorization Act of 2005, Section 3116, for the tanks and their associated piping at SRS and Idaho to be closed, waste must be removed as much as is practical and
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Advice on the Department of Energy’s Cleanup Technology Roadmap: Gaps and Bridges meet the performance objectives in 10 CFR 61.40.4 Closing a tank marks the end of EM cleanup activities for that tank.5 Tank closure is EM’s top priority for site cleanup, and it is a top priority among public citizens and their representatives. The criteria under which Hanford tanks can be closed has not yet been established (NRC 2006b, Johnson 2008). Most of the legacy waste tanks at Oak Ridge were closed years ago although a few small surge and collection tanks remain (Appendix F). Impact of the Gap Tanks containing waste heels that have not been removed to the “extent practical” according to the Reagan Act or that cannot be shown to meet specified performance objectives to limit long-term radiation exposure cannot be closed. Tanks containing appreciable amounts of residual waste (heels) are unlikely to be accepted by DOE, its regulators, or the public for closure. Removal of the bulk of the waste with large pumps (for SRS and Hanford) or pneumatic devices (for INL) appears to be relatively straightforward and efficient. However, experience at Hanford and SRS has shown that sludge heels inevitably remain in the tanks after the bulk of the waste has been retrieved. Reducing the volume of this heel becomes increasingly difficult, time-consuming, and expensive as the volume of the heel declines. The tanks at Hanford and SRS generally have small access ports (risers); some tanks contain debris, and at SRS cooling coils further inhibit access and waste retrieval (Figure 2.3). A number of single-shell tanks at Hanford have leaked waste into the environment, and some double-shell tanks at SRS have leaked waste into the annulus between the tank walls (Figure 2.4). The structural integrity of tanks that have leaked is considered to be compromised. Buried waste transfer lines and ancillary equipment (e.g., smaller tanks, valves, transfer pits, and pumps) also contain waste. 4 If these criteria are met, DOE can designate the residual waste as “waste incidental to reprocessing,” a legal distinction that allows it to be permanently disposed onsite. Otherwise, classified as HLW, it would have to be removed for disposal in a licensed repository such as that proposed at Yucca Mountain, Nevada. 5 Actions to close a tank after the waste removal criteria are met include isolating it from the waste system and filling it with a material such as grout with no intent for further waste retrieval.
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Advice on the Department of Energy’s Cleanup Technology Roadmap: Gaps and Bridges FIGURE 2.3 Cooling coils in an SRS tank. Such coils maintained the temperature of high-level radioactive waste below boiling. The coils are an obstacle to removing the tank waste at SRS. SOURCE: Department of Energy. Current Status Oak Ridge completed cleaning eight concrete-walled tanks in 2001, and all together closed 65 tanks between 1995 and 2007 (NRC 2007c). These tanks are smaller than those described above, but nonetheless demonstrated the use of several types of innovative remotely operated equipment, which led to substantial savings in cost and schedule (Boyd 2008). At the time of the committee’s visit, Hanford had retrieved the waste from seven single-shell tanks, and waste retrievals were in progress or planned for four others (Mauss 2007). SRS has closed two tanks and is expected to have four more ready for closure by 2010. None of these tanks had internal cooling coils or other significant obstructions. The cleaning of a tank annulus has not been attempted. Both Hanford and SRS operate tank mock-ups in which waste-retrieval challenges are simulated and new technologies are tested. In 2005 an EM subcontractor successfully retrieved simulated calcine from a bin (AEATES
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Advice on the Department of Energy’s Cleanup Technology Roadmap: Gaps and Bridges FIGURE 2.4 Salt accumulated in a tank annulus. Double-walled tank construction helped to prevent the release of radioactive waste into the environment. In this figure minor leaks from the primary wall (right) have accumulated in the annulus. SRNL recently developed a robotic crawler for cleaning the tank wall. SOURCE: Department of Energy. 2005). The sites have little experience in removing waste from bins, tank annuli, transfer pipes, or ancillary equipment. Approaches to Bridge the Gap Residual waste retrieval from tanks and ancillary pipelines was identified as an important technology gap in three NRC reports (2001b, 2003, 2006b). These reports recommended the development of physical and chemical cleaning technologies to improve the effectiveness of residual waste removal in tanks, tank annuli, and pipelines, especially technologies that reduce the risks of leakage of wastes to the environment during the removal operations (e.g., by using little or no water to retrieve wastes). Opportunities for expanding the use of robotics technologies for waste retrieval and tank cleaning are discussed in NRC (2006b). Site presentations at Hanford (Honeyman 2007) and SRS (Davis 2008; Spears 2008) included a number of technology needs for improving waste retrieval (Appendixes D and G).
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Advice on the Department of Energy’s Cleanup Technology Roadmap: Gaps and Bridges chemically hazardous, or both. Some contaminants may be easy to remove and others strongly bound to a substrate (e.g., concrete, steel). According to information gathered by the committee, the most difficult D&D challenges include radiochemical separation facilities at Hanford, Idaho, and SRS; production reactors at SRS; gaseous diffusion plants at Oak Ridge, Paducah, and Portsmouth, plutonium processing plants at Hanford, Los Alamos, and SRS; tritium processing facilities at SRS (NRC 2001c), and support facilities (including sewage lines) at SRS (Whitaker 2008). DD-1: D&D work relies on manual labor for facility characterization, equipment removal, and dismantlement. Currently D&D projects require extensive hands-on, manual labor that unavoidably exposes workers to hazardous conditions (Figure 2.9). Besides the rather obvious hazards to workers who manually dismantle, size reduce (cut up), and remove contaminated structures and equipment, each facility requires extensive characterizations to determine the nature of contaminants before, during, and after D&D. Characterization exposes workers to radiation and other hazards and is costly, amounting to some 15 to 25 percent of overall D&D budgets (NRC 2001c). Work must sometimes be done in high-radiation environments. For example, at Idaho a technical challenge is to characterize and remove contamination in pipelines and other structures that have high-radiation fields (up to 1,600 rads/hour) and are located under a building at the site (NRC 2007c, p. 28). Workshop panelists representing Oak Ridge agreed that D&D is a top priority for the site, mainly due to challenges presented by the gaseous diffusion plants (manual removal of transite siding from these very large buildings was cited (Figure 2.10) and other deteriorating structures (NRC 2007c; McCracken 2007). SRS D&D priorities are worker protection and characterization of facility “hot spots” (NRC 2007c, p. 27). Impact of the Gap Safety of workers and of the public is the primary consideration in the EM cleanup. Worker safety is a criterion for contractors. Should an incident occur that harms a worker or could have caused harm, operations are halted until the incident has been thoroughly investigated, the cause is determined, and measures to prevent such future incidents are implemented. No matter how carefully planned and carried out, hands-on D&D work carries a high risk for radiation exposure, bodily uptake of radioactive or hazards materials, and injury.
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Advice on the Department of Energy’s Cleanup Technology Roadmap: Gaps and Bridges FIGURE 2.9 Hands-on D&D work. Facility D&D often requires hands-on work with large, contaminated equipment in hot, confined spaces. Although uncomfortable, personal protective equipment like that worn by the worker in this photograph is necessary to protect workers from the uptake (skin, mouth, nose) of radioactive or other hazardous substances and from physical hazards. SOURCE: Department of Energy. FIGURE 2.10 Transite removal at Oak Ridge. Transite was a commonly used siding material throughout the DOE complex. Today’s workers must wear personal protective equipment and follow special procedures to remove this asbestos-containing siding. Transite is heavy and often has to be handled in confined, elevated work spaces as shown here. SOURCE: Department of Energy.
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Advice on the Department of Energy’s Cleanup Technology Roadmap: Gaps and Bridges Current Status Manual labor has been key to EM’s D&D work, including the successful closure of the Rocky Flats site under budget and ahead of schedule. Rocky Flats was formerly a major plutonium-handling site, which has now been converted into a wildlife refuge—a major accomplishment. Hands-on labor for D&D is a good example of the committee’s considering technology gaps as potholes in a road that EM can work around. EM and its contractors can and have managed worker safety for hands-on D&D. Nonetheless, R&D toward removing workers from a hazardous environment could provide a better solution. Robotics and remote manipulation for sensing, inspection, measurement, and tank waste remediation have been developed and deployed to some extent at both the Savannah River and Hanford sites. DOE has made limited use of some robotic technology as part of the Glovebox Excavator Method used to demonstrate retrieval of buried TRU waste at Idaho (NRC 2005, p. 43). Researchers at INL have been exploring the possibility of using semi-autonomous robotic systems for detection and characterization in radiological environments. These systems may reduce some uncertainties inherent in different training and skill levels among operators while allowing tasks to be completed more quickly than in the case of purely teleoperated systems (Nielsen et al. 2008). In all cases, the purpose of employing robotic and remote systems is to reduce D&D worker risks while accelerating the pace and accuracy of the remediation operation. SRNL is extending its previous experience with remote devices for use in radiation areas to develop robotic and teleoperated systems for homeland security and defense applications. Non-DOE agencies and universities, including the National Aeronautics and Space Administration (NASA), National Oceanic and Atmospheric Administration, and Carnegie Mellon University, conduct research on robotics and remote-operator systems for the Department of Defense and for ocean and extraterrestrial exploration. There are also recent efforts outside the United States to develop robotics and remote systems for decommissioning of former nuclear power facilities. For example, a group at Lancaster University in the United Kingdom has been funded by the Nuclear Decommissioning Authority to develop a multiarmed robotics system that would allow D&D operations in the United Kingdom to be faster, safer, and more cost-effective, and reduce the radioactivity dose levels to which workers are exposed (Bakari et al. 2007). Work at the French Atomic Energy Agency and COGEMA has focused on radiation-hardened electronics and force feedback mechanisms used in telerobotics operations involving spent fuel (Desbats et al. 2004).
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Advice on the Department of Energy’s Cleanup Technology Roadmap: Gaps and Bridges Approaches to Bridge the Gap According to this committee’s assessment of information it received, the following have promise for future EM R&D: Improved technologies that could reduce worker exposure by reducing the need for manual sample collection. These include: Devices for rapid characterization of low levels of contamination (radionuclides and EPA-listed substances) on surfaces of construction materials and equipment, including devices that can detect very-low-energy beta emitters (e.g., tritium), low-energy photon emitters (iodine-129), and beryllium; Minimally invasive methods to characterize contaminant concentrations as a function of depth in construction materials, especially concrete; and Instruments for remote mapping of radionuclide contamination at low levels that can differentiate specific radionuclides, including beta and alpha emitters. Greater use of robotics to reduce manual labor and worker risks. NRC (2002) recommended that DOE develop robotic technologies for retrieval and repackaging of buried waste. NRC (2001c) recommended research to develop intelligent and adaptable robotic systems that can be used for facility decommissioning. Next-generation robotic systems will need to be: Adaptable to a variety of environments and topographies; Semi-autonomous to provide a more intuitive human-robot interface, prevent accidents, and optimize execution of tasks; and Highly reliable. Such needs were recognized in EM’s former D&D Focus Area 10 years ago (Staubly and Kothari 1998) and remain at the forefront of R&D in robotics. Prioritization of the Gap Relative to other science and technology gaps discussed in this section the committee judged the priority of addressing this gap as High.
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Advice on the Department of Energy’s Cleanup Technology Roadmap: Gaps and Bridges Criteria Relative Rating High Medium Low Volume of waste affected X Potential to reduce technical uncertaintya X Potential to affect cleanup schedule X Potential to affect cost X aIncluding risks to workers. DD 2: Personal protective equipment tends to be heavy and hot and limits movement of workers. As described in DD-1, manual D&D work at all sites requires workers to perform safely and efficiently in hazardous environments. Broadly speaking, personal protective equipment (PPE) can range from standard items such as coveralls, safety glasses, and gloves, to face masks with capability to filter or detoxify airborne contamination (“assault masks”), to full-body anti-contamination suits for work in heavily contaminated areas (Figure 2.9). Anticontamination suits encapsulate the entire body in an impervious suit, and provide safe breathing air by means such as filtration of ambient air, use of self-contained breathing apparatus, or an external supply of uncontaminated air delivered through a flexible hose. PPE for less-contaminated workspaces consists of some type of protective clothing, often in multiple layers, which encloses most or all of the body. PPE is often heavy and bulky, resulting in limitation of motion, extra exertion, and overheating with the consequent risk of heat stress (Bernard 1999). Protective clothing that does not allow perspiration to escape increases body temperature, which reduces worker comfort and productivity (DOE 1998b). Impact of the Gap The limitation of motion and extra exertion imposed by PPE required in high-contamination zones can cause worker stress and reduce the efficiency of D&D work. PPE with externally supplied cool air can reduce heat stress but can have various limitations and problems related to the supply hose. During its Idaho visit, the committee was shown a waste retrieval operation in the Radioactive Waste Management Complex in which workers can operate excavation equipment for only short periods of time due to the risk of heat stress. This, coupled with the time to don and doff PPE, increases the duration and cost of D&D activities.
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Advice on the Department of Energy’s Cleanup Technology Roadmap: Gaps and Bridges Current Status PPE is used throughout the nuclear and hazardous materials industries. There are companies that develop and manufacture PPE (see, e.g., Frham Safety26 and G/O Corporation27). EPRI and USNRC are supporting technology for improving PPE. Shedrow (2008) noted that SRNL has developed a variety of PPE technologies that have been used in environmental remediation work at SRS and other locations. Approaches to Bridge the Gap According to this committee’s assessment of information it received, there is a need for PPE designed for elevated temperatures and longer exposures in contaminated environments. Lighter and cooler PPE would allow workers to safely remain longer in the presence of hazardous materials. There are opportunities to adapt available technologies (e.g., from NASA, Department of Defense). For example, adaptations of NASA protective clothing technology have been examined for use in development of protective clothing for firefighters (Foley et al. 1999). The Department of Defense has supported a number of programs for development of advanced impermeable “NBC” (nuclear/biological/chemical) anticontamination clothing for a number of years, citing this area of need in the Defense Technology Area Plan (DOD 1999). This technology has not been adapted and adopted in D&D applications. Further evaluation would seem appropriate. Robotics and remote or teleoperated techniques will also limit worker exposure, although there are circumstances (i.e., inspection, removal in very complex areas, sensitive structures) where manual labor is essential. Prioritization of the Gap Relative to other science and technology gaps discussed in this section the committee judged the priority of addressing this gap as Low. Criteria Relative Rating High Medium Low Volume of waste affected X Potential to reduce technical uncertaintya X Potential to affect cleanup schedule X Potential to affect cost X aIncluding risks to workers in this instance. 26 http://frhamsafety.com/anti-c/encapsulating_suit.htm. 27 http://www.gocorp.com/.
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Advice on the Department of Energy’s Cleanup Technology Roadmap: Gaps and Bridges DD-3: Removing contamination from building walls, other surfaces, and equipment can be slow and ineffective. Decontamination of facilities and equipment is carried out at multiple stages of the decommissioning process in order to lower worker exposure, prepare equipment for disassembly and removal, and prepare a facility for tear-down and removal (to limit release of contaminants prior to further treatment and disposition of the debris). A primary objective of decontamination procedures is to generate a small volume of the most hazardous waste, while the larger volumes of waste have low or no hazard, thus reducing the cost and long-term risk of their disposal. Some decontaminated equipment or facilities might be recycled or reused. The end state of any decontamination activity must be consistent with both site-specific and overall DOE cleanup objectives. Concrete, such as that in the large canyon buildings on the SRS and Hanford sites and reactor shielding structures at multiple DOE sites, constitutes most of the volume and weight (estimated at over 27 million tons) of DOE’s surplus facilities. Because of its inherent porosity, its heterogeneous surface structure (pits, cracks, and smooth and rough areas on both the macro- and microscopic scales), and its chemistry, concrete poses special challenges for decontamination. At present, the usual method for removing surface contamination is called “scabbling”—the physical removal of the surface by workers in protective clothing using power tools. This procedure generates a great deal of dust and is hazardous to workers. Because of long-term exposure, the concrete is often contaminated to a depth of several millimeters beneath its surface (DOE 2000), and in some cases, such as for tritium, considerably deeper. In many instances, paints, sealers, and varnishes on concrete surfaces create a laminate problem, with aged materials being harder to decontaminate than more recent deposition (NRC 2001c). Contaminated equipment including glove boxes, shielded cell liners, lead shielding, and plastic parts, along with heavily corroded surfaces, pose particular problems due to geometries and occluded structures that trap contaminants. In addition, effectiveness of D&D methodologies can be severely compromised due to the inherent difficulty of characterizing both the chemical nature of contaminants and the degree of their removal following decontamination resulting from occluded, porous, and heterogeneous surfaces of degraded structural building materials (Halada 2006). Before, during, and after the process of decontamination, it is necessary to identify contaminants on concrete and other structural surfaces. Nondestructive methods would be far preferable to the physical removal of samples (e.g., cement cores, metal coupons) for analysis.
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Advice on the Department of Energy’s Cleanup Technology Roadmap: Gaps and Bridges Impact of the Gap Current decontamination processes used by D&D contractors are labor-intensive and costly, and there is the ever-present risk of exposure to toxic and radioactive materials; see DD-1. These processes also generate large volumes of contaminated secondary wastes and often leave behind unwanted residual contamination. The risk of accidents is increased by the bulky protective clothing; see DD-2. Because of cost and hazards, cleanup contractors often choose to dispose of contaminated equipment and construction materials as wastes rather than to decontaminate and recycle them. While current baseline decontamination technologies probably can be made to work for future D&D work, there are opportunities to do the job more safely and cheaply and achieve higher degrees of decontamination by developing and using new technologies. Current Status The EPA has recently conducted two workshops on decontamination methods for chemical, radiological, and biological contaminants through its Office of Research and Development’s National Homeland Security Center (EPA 2005, 2006a). In addition, the EPA has developed a reference guide, “The Technology Reference Guide for Radiologically Contaminated Surfaces,” which provides a broad overview of chemical and physical methods for removing contamination from surfaces (EPA 2006b). These surveys and associated reports consider a broad range of options for decontamination. The technological challenges considered in the EPA report have much in common with DOE site needs, including a need for faster and more effective decontamination methods, determining surface chemistry interactions, difficulties with vertical surfaces and reaching high work areas with decontamination equipment, decontamination of tiny cracks and seemingly inaccessible areas, subsurface effects, and waste generation. Investigators at INL completed a comprehensive study of removal and collection of radioactive contamination from building exteriors, which was supported by the Defense Advanced Research Projects Agency (Demmer at al. 2007). Activities in the United Kingdom and Canada are also of interest. For example, the effect of weathering and other environmental conditions on the association of radiological contamination with porous surfaces and resulting implications for decontamination have been considered in research by the Chemical, Biological, Radiological-Nuclear and Explosives Research and Technology Initiative Secretariat of the Defence Research and Development Canada, Centre for Security Science.28 28 See http://www.css.drdc-rddc.gc.ca/crti/invest/rd-drt/02_0067rd-eng.asp.
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Advice on the Department of Energy’s Cleanup Technology Roadmap: Gaps and Bridges Approaches to Bridge the Gap Scientific understanding of the interactions among contaminants and construction materials is fundamental to developing more effective D&D technologies. Such information includes how contaminants bind to steel and concrete surfaces; how they penetrate into these materials; their migration into pores, fissures, and welds; and time-dependent aging effects. NRC (2001c) identified decontamination as an important science and technology gap and recommended specific areas of research needed to improve decontamination technologies, including: Development of a fundamental understanding of the chemical and physical interactions of important contaminants with the primary materials of interest in D&D projects, including concrete, stainless steel, paints, and strippable coatings to gain a better understanding of how contaminants bind to and penetrate these materials. This would involve understanding the interactions both kinetically and thermodynamically under a variety of conditions (pH, temperature, ionic strength); Development of dry decontamination technologies, including use of supercritical fluids such as carbon dioxide, that can be used to remove high levels of contamination with minimal secondary wastes (Appendix D); Exploration of the role of nanotechnology (for more efficient chelating) and biological mechanisms (including bioleaching, biosurfactants, biocatalysis, and cell-less enzymatic processes) for more efficient and rapid decontamination methods; Advanced methods to leach/migrate contaminants from cementitious matrices (Appendix D); and Development of decision tools for determining optimal decontamination approaches. Prioritization of the Gap Relative to other science and technology gaps discussed in this section the committee judged the priority of addressing this gap as Medium. Criteria Relative Rating High Medium Low Volume of waste affected X Potential to reduce technical uncertainty X Potential to affect cleanup schedule X Potential to affect cost X
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Advice on the Department of Energy’s Cleanup Technology Roadmap: Gaps and Bridges CONCLUSIONS This chapter has presented 13 gaps that the committee views as the principal impediments to the EM site cleanup program. They are obstacles or impediments in the sense that they can represent likely causes for schedule delays, cost increases, and potential failures to meet currently envisaged cleanup objectives. Developed through the committee’s site visits and other information gathering, all of these gaps are worthy of EM’s consideration in developing future science and technology roadmaps. The committee was mindful of the research initiatives set forth in the EM roadmap but has provided its own independent assessments in this chapter. The committee’s prioritization of these gaps, given in Table 2.1, reflects a variety of technical judgments, including schedule and budget impacts, risk reduction, and likelihood of new technology developments that can bridge the gap. The committee has not attempted to be prescriptive by recommending specific research to address each gap, but rather it has indicated R&D approaches that it judges are most likely to bear fruit. The committee used this chapter as a basis for developing the remainder of this report. Chapter 3 describes the personnel expertise and physical infrastructure that EM will need to carry out this R&D. Chapter 4 describes approaches and opportunities for EM to leverage its R&D work with other organizations.
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