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Advice on the Department of Energy’s Cleanup Technology Roadmap: Gaps and Bridges FIGURE D.1 The Hanford reservation is a 670 square mile site in southeastern Washington. Industrial-scale production of nuclear weapons materials began on the site in 1944. SOURCE: Department of Energy.
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Advice on the Department of Energy’s Cleanup Technology Roadmap: Gaps and Bridges Appendix D Hanford Reservation INTRODUCTION The National Research Council Committee on Development and Implementation of a Cleanup Technology Roadmap held its fourth meeting in Richland, Washington, on October 30-31 and November 1, 2007. The purpose of the meeting was to obtain information relevant to the committee’s Statement of Task (SOT) through presentations and tours by Department of Energy (DOE) staff and their contractors.1 This appendix provides a factual summary of the information related to the four items in the committee’s SOT obtained during the meeting, the site visits, and documents provided to the committee. This appendix first describes the history and status of the DOE site at Hanford to provide perspective on the range of cleanup issues being managed by the DOE Office of Environmental Management (EM). The next sections summarize information presented to the committee, which guided the committee’s deliberations in addressing its SOT as described in the main text. This appendix thus provides support for the findings and recommendations developed by the committee. HISTORY In March of 1943, 670 square miles in southeastern Washington State were chosen to be the site for the plutonium manufacturing operations of 1 The agenda for this meeting is shown in Appendix B.
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Advice on the Department of Energy’s Cleanup Technology Roadmap: Gaps and Bridges the Manhattan project, see Figure D.1. Designated the Hanford Reservation, the area became the first industrial-scale plutonium production site in 1944, and its role was to provide the United States with nuclear weapons material (Gephart 2003). Hanford plutonium was used in the “Fat Man” atomic bomb dropped on Nagasaki in World War II. After the war the Atomic Energy Act of 1946 removed Hanford from military control and placed it under the civilian-run Atomic Energy Commission, which later became the DOE (Gephart 2003). During the early years, radiation exposure and waste disposal were not regarded as significant issues versus production needs and, therefore, not closely regulated. The first reactors built were called single-pass reactors because the cooling water ran only once through the core, where it became contaminated with radioactive activation and sometimes fission products, before being discharged to the Columbia River or soil. Water recirculation was included in the last of nine reactors built onsite; it came online in 1964 (Gephart 2003). Five reprocessing plants were built in the 1940s to 1950s: T Plant, B Plant, U Plant, REDOX Plant, and Purex Plant, which generated huge volumes of waste. T and B plants produced an average of 4,000 gallons of waste liquid for each ton of spent fuel reprocessed. On average, the REDOX and Purex plants produced 4,600 gallons and 500 gallons, respectively, of liquid per ton of fuel. Table D.1 shows the amount of fuel reprocessed at each plant and their operating histories (Gephart 2003). Depending on its source and radionuclide content, the waste was either released to the environment or pumped into large tanks. Highly radioactive waste was typically stored in tanks, and resulted in some leakage into the ground. Solid waste was buried in landfills or stored in surface facilities. Water that contained low- to intermediate-levels of radioactivity was released into the Columbia River, ponds, trenches, or cribs (Gephart 2003). In 1970, transuranic-contaminated solid waste began to be separated from low-level waste and placed in retrievable storage for subsequent offsite ship- TABLE D.1 Uranium Fuel Processed in Hanford Reprocessing Plants Plant Fuel Reprocessed (tons) Operating History T and B 8,900 (8%) 1944-1956 REDOX 24,600 (23%) 1952-1967 PUREX 73,100 (69%) 1956-1972, 1983-1990 Total 106,600 (100%) SOURCE: Gephart (2003, p. 1.26)
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Advice on the Department of Energy’s Cleanup Technology Roadmap: Gaps and Bridges ment to a geologic repository (Gephart 2003). Gaseous effluents from the reactors and reprocessing plants were released into the atmosphere. Nuclear material remained stored in surface facilities. There are many unknowns about the volumes and physical, chemical, and radiological characteristics of the waste generated, stored, and released at Hanford. The wastes in the tanks are complex chemical mixtures. They have been created from multiple reprocessing techniques that include bismuth phosphate and solvent extraction using hexone or tributyl phosphate. Also, other processes have been used to recover radionuclides. Acidic waste streams were made caustic by adding concentrated sodium hydroxide, and sometimes the tanks were used as dumps for miscellaneous waste such as experimental fuel elements, ion exchange columns, and plastic bottles containing plutonium and uranium. Diatomaceous earth and cement were also added to some tanks to soak up liquids (Gephart 2003). The Hanford tanks contained about 54 million gallons of chemical and radioactive waste. This accounted for 10 percent of the volume of waste that was originally generated. The other 90 percent was treated, released to the ground, or evaporated into the air. The high-level waste (HLW) is stored in 177 single- and double-shelled tanks. The 190 million curies of waste in these tanks make up about 50 percent of Hanford’s radioactivity inventory. About 67 of the 149 single-shelled tanks have or are suspected to have leaked up to 1.5 million gallons of waste into the ground (Gephart 2003). To prevent additional releases, all drainable liquid waste in the single-shell tanks has been pumped into the newer double-shell tanks. None of the double-shell tanks have leaked, although they have long surpassed their original life expectancy (Gephart 2003). Tank cleanup is now scheduled to be completed in 2042, which means the oldest single-shelled tanks will be about a century old.2 Information presented to the committee shows that EM has made significant progress in cleanup and site remediation. However, removal of the majority of the waste from the tanks, solidification of the high- and low-activity portions of tank wastes, deactivation and decommissioning of many structures, and remediation or monitoring of much of the contaminated subsurface still remain to be done. Most of the site’s nearly 400 million curies and 400,000 to 600,000 tons of chemicals remain to be dealt with onsite. DOE has divided these tasks into separate programs that are administered by two DOE field offices: 2 Since the briefings in 2007, DOE has issued the River Protection Project System Plan, Revision 3A which projects a tank cleanup completion date of 2049 for a reference case that approximates the key features of the current baseline and underlying technical basis (available at http://www.hanford.gov/orp/uploadfiles/ORP-11242_Rev-3A_(Released).pdf).
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Advice on the Department of Energy’s Cleanup Technology Roadmap: Gaps and Bridges Tank cleanup (Office of River Protection, ORP), and Other site cleanup and remediation activities (Richland Operations Office, RL). The participants at the committee’s Richland meeting and site visits included representatives from EM, ORP, RL, the DOE Office of Science (SC), the Pacific Northwest National Laboratory (PNNL), site cleanup contractors, regulatory agencies, Native Americans, and other citizens. In carrying out its tank cleanup mission, the ORP will be dealing with more than 50 million gallons of tank waste in 177 underground tanks. ORP is also responsible for construction of the Waste Treatment Plant (WTP), a $12 billion project that has been described as the world’s largest nuclear chemical processing plant (Tamosaitis 2007). The private company Bechtel National, Inc. is contracted to design and construct the plant and the private company CH2M HILL is contracted to operate the tank farms and assist ORP in planning and optimization of its mission. This includes leading technology roadmapping efforts and systems planning. CH2M HILL also works with EM-20’s science and technology programs (Honeyman 2007).3 The RL mission includes the disposition or remediation of: 2,100 metric tons of spent nuclear fuel (SNF); 18 metric tons of plutonium-bearing materials, which is in various forms; 80 square miles of contaminated groundwater; 25 million cubic feet of buried or stored solid waste in 175 waste trenches; about 1,700 waste sites and 500 contaminated facilities, including five reprocessing canyons and nine reactor complexes; and 1,936 capsules of cesium and strontium containing 130 million curies of radioactivity (Morse 2007). DOE, the U.S. Environmental Protection Agency (EPA), and the State of Washington Department of Ecology signed a comprehensive cleanup and compliance agreement on May 15, 1989. The Hanford Federal Facility Agreement and Consent Order, usually called the Tri-Party Agreement (TPA), is an agreement for achieving compliance with the Comprehensive Environmental Response, Compensation, and Liability Act remedial action provisions and with the Resource Conservation and Recovery Act treat- 3 Since the site visit in 2007, ORP has awarded the tank operations contract to Washington River Protection Solutions, which replaced CH2M HILL on October 1, 2008.
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Advice on the Department of Energy’s Cleanup Technology Roadmap: Gaps and Bridges ment, storage, and disposal regulations and corrective action provisions (DOE-ORP/RL 2007). According to the EPA’s original assignment of potential hazards, Hanford has four different sites that qualified for the National Priorities List. The four areas include the 100 Area (reactors), 200 Area (fuel reprocessing), 300 Area (which includes the waste burial sites located a few miles north), and the 1100 Area (Gephart 2003). EM manages its cleanup work according to legal provisions of the TPA. Honeyman (2007) noted that if future TPA changes reduce the amounts of contamination allowed to be left onsite after the cleanup, and therefore increase the requirements for removal of waste from tanks or from burial sites, these changes could introduce new technical challenges for accomplishing the cleanup. CLEANUP PROGRAMS AND CHALLENGES This section describes ongoing cleanup programs and challenges as presented to the committee during its open meeting sessions at Richland, Washington, and its visits to the Hanford site and to PNNL. The information is organized according to the program areas of the EM Science and Technology Roadmap (DOE 2008). Roadmap Area: Waste Processing “Hanford waste tanks are, in effect, slow chemical reactors in which an unknown but large number of chemical (and radiochemical) reactions are running simultaneously. Over time, the reaction dynamics and compositions have changed and will continue to change” (Colson et al. 1997, p. B-11). Cleanout and closure of the Hanford tanks is a major EM challenge. As described above, tank waste is highly heterogeneous among Hanford’s 177 tanks, and it is also heterogeneous within any given tank. This is due to the variety of fuel reprocessing and plutonium recovery processes used at the site, especially in the early years of production, and the fact that the acidic reprocessing waste was neutralized and made alkaline for extended storage in Hanford’s carbon steel waste tanks. As a result of neutralization, the tanks may contain one or more of the following: (1) an insoluble “sludge” that contains precipitated metals, fission products, and most actinide elements; (2) a salt cake that contains water-soluble chemicals and some fission products, notably Cs-137; and (3) a supernatant salt solution. These wastes are to be retrieved and, depending on their composition, prepared for disposal according to four methods:
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Advice on the Department of Energy’s Cleanup Technology Roadmap: Gaps and Bridges About 8 to 9 million gallons (17 percent of total) of the tank waste will be vitrified in the WTP’s HLW facility, About 14 million gallons (26 percent of total) will be vitrified in the WTP’s low-activity waste (LAW) facility, About 28 million gallons (52 percent of total) will be vitrified in a supplemental bulk vitrification facility, or by another supplemental process, and About 2 to 3 million gallons (5 percent of total) that qualify as transuranic (TRU) waste will be packaged and sent to the Waste Isolation Pilot Plant (WIPP) in New Mexico, which is DOE’s TRU waste disposal facility (NRC 2006; Mauss 2007). Waste Treatment Plant The purpose of Hanford’s WTP is to enable tank closure by processing the tanks’ contents into appropriate waste forms for disposal. Constructing and operating the Hanford WTP is an unprecedented, one-of-a-kind challenge for DOE. The WTP is planned to begin full operation in 2018. At the time of the committee’s visit, the WTP was about 70 percent designed and 30 percent constructed. Brouns (2007) noted that construction had been delayed by concerns regarding the WTP’s ability to withstand seismic events, and that construction resumed after these concerns were resolved by PNNL and other expert evaluations. The WTP includes four main facilities: Waste pretreatment, LAW vitrification, HLW vitrification, and Laboratory analyses, plus a “balance of facilities” building. Tamosaitis (2007) noted that the processing facilities rely on many first-of-a-kind technologies or applications of technologies. Pretreatment The purpose of waste pretreatment is to process incoming tank waste in order to obtain two waste streams for vitrification either as HLW or as LAW. A quarter-scale pretreatment engineering “platform” is being installed to test and demonstrate pretreatment operations including integrated sludge washing, leaching, and waste concentration. These tests will use nonradioactive waste simulants. The test facility does not include the ion exchange operations. Brouns (2007) presented key WTP technology issues identified by an External Flowsheet Review Team:
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Advice on the Department of Energy’s Cleanup Technology Roadmap: Gaps and Bridges Plugging of process piping, Mixing vessel erosion, Mixing system design, Process operating limits, and Scale-up demonstration of sludge leaching and filtration. The pretreatment engineering platform is designed to help address the last two items. As examples, Brouns described the EFRT finding that mixing system designs may result in insufficient mixing, especially with large particles, small dense particles, and rapidly settling Newtonian slurries, and that neither caustic leaching nor the oxidative leaching process has been demonstrated at greater than bench scale. Michener (2007) described mixing requirements in the WTP as being on the forefront of mixing science. In particular, the pulse jet mixers, which are an important no-moving-parts component of the WTP, introduce unique solids lifting behavior. Tamosaitis (2007) also described current research and development (R&D) on these and similar issues, including waste stream rheology in pipes and during mixing in tanks, sludge washing, hydrogen generation, process chemistry, and online instrumentation. In describing the pretreatment ion exchange operations, intended to remove cesium-137 and some other radionuclides from the LAW stream, Tamosaitis explained that there is need for better understanding and optimization of waste filtration and the Cs-removal ion exchange resin. The resin is an organic polymer and subject to degradation by chemicals and radiation. More resistant inorganic ion exchange materials exist but cannot be eluted (Tamosaitis 2007). LAW Vitrification and Supplemental Treatment The WTP will have the capacity to vitrify only about a third of the tank waste identified as LAW, as noted earlier. Several supplemental processes including those referred to as bulk vitrification and steam reforming are being developed as options to process the remaining two-thirds. Other WTP throughput issues indicate the need for supplemental LAW treatment. Examples are the handling of diverse input streams, behavior of solids, and response to process upsets (Tamosaitis 2007). Tamosaitis also listed improved waste forms, glass formulations, and melters as future technology needs for enhancing throughput. A supplemental pretreatment process, fractional crystallization, to separate radioactive cesium from the LAW salt stream is also under development. Bagaasen (2007) described his work to resolve an important problem with bulk vitrification. In this process, waste and glass-forming material (frit) are mixed into a refractory-lined box, and the mixture is melted via
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Advice on the Department of Energy’s Cleanup Technology Roadmap: Gaps and Bridges Joule heating. It appeared that the radionuclide Tc-99 would migrate from the melt into the refractory and hence not be properly incorporated into the glass. Starting with a conceptual model, Bagaasen was able to modify the frit and add carbon sources to increase the melt viscosity, and to modify the “cold cap” barrier between the melt and refractory, to resolve the problem. These results have been verified by full-scale tests using nonradioactive rhenium as a surrogate for the Tc-99 (Bagaasen 2007). Fractional crystallization was recommended for evaluation as the result of a series of workshops held in 2002. The EM Office of Cleanup Technology (EM-21) began funding process development in 2005. The process development team includes: AREVA NC, Swenson Technologies, Savannah River National Laboratory, Georgia Institute of Technology, and CH2M HILL. Fractional crystallization uses evaporation and crystallization to separate radioactive isotopes from the nonradioactive sodium salts that make up a large fraction of Hanford tank waste. As the water in the waste solution evaporates, nonradioactive sodium salts crystallize. Radionuclide ions like 137Cs+ are too large to substitute for Na+ ions in the sodium salt crystal, so the radionuclides tend to remain in the liquid phase. Separation of the crystals from the remaining solution completes the process. While there are clear advantages, for example, no new chemicals have to be added to the waste, there are a number of R&D challenges at the present time. Honeyman (2007) observed that Hanford’s waste processing rates may need to increase in order to maintain the tank closure schedule. R&D could be targeted toward: Providing greater supplemental capacity for LAW waste treatment or making current waste treatment more efficient and rapid, Developing fractional crystallization as an additional or alternative pretreatment technology, and Reducing secondary wastes. Honeyman concluded that bulk vitrification and fractional crystallization are potentially applicable at other DOE sites as well as Hanford. Research Needs and Capabilities As research needs for WTP operation, Tamosaitis (2007) included precipitation/gelation modeling and prediction, non-Newtonian computational
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Advice on the Department of Energy’s Cleanup Technology Roadmap: Gaps and Bridges fluid dynamics modeling, and simulant development.4 These are needed to reduce the risks of pipe or equipment plugging in the WTP. This is especially important for WTP’s “black cells” in which maintenance will not be possible. For steps in which the waste or its radionuclides are concentrated, hydrogen mitigation and handling is a challenge. Improved online instrumentation for process control and quality assurance is also needed (Tamosaitis 2007). Alternatives to borosilicate glass that can incorporate more waste per unit volume and/or be fabricated more efficiently, for example, iron-phosphate glass, might be developed through further research (Smith 2007). Tamosaitis (2007) described national laboratory capabilities that will be needed to support construction, start-up, and operation of the WTP for the next 25-30 years: Radiochemistry, Modeling (all forms), Glass/waste form development, Hot cells, Analytical development and support, Pilot testing facilities, Chemical engineering and chemistry, Materials technology, and Continuity of technical knowledge. He noted that there is a special need to ensure a future supply of technical personnel. This was highlighted by the EFRT as well as observations about the number of retiring baby boomers, decline in engineering graduates, commercial competition, and the extended schedule for WTP operation. Over the next 10 years, half of the Hanford workforce holding critical waste treatment operation and research skills will retire. Hanford Tank Issues The EM roadmap (DOE 2008) includes waste storage, retrieval, and tank closure within the waste processing program area. Information on these topics was presented during the committee’s Richland meeting and the Hanford site visit. 4 Engineering-scale process tests are usually run in facilities that cannot utilize actual radioactive waste. There is a risk that the simulated wastes may not behave the same way as actual wastes and thus provide misleading results.
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Advice on the Department of Energy’s Cleanup Technology Roadmap: Gaps and Bridges Storage Brouns (2007) suggested three technology needs to support the continued use of Hanford’s double-shelled waste tanks. The first is improved understanding of tank corrosion mechanisms, especially in the vapor space above the waste and at the liquid line. The second is for new approaches that may provide increased waste storage capacity. The third is for remote inspection systems, including ultrasonic testing over large areas. Methods are also needed to assess the integrity of the single-shelled tanks, especially as waste retrieval schedules are impacted by delays in start-up of the waste processing facilities. Retrieval At the time of the committee’s visit, seven single-shell tanks had been emptied, waste retrieval was in progress for two tanks, and two tanks were being outfitted for retrieval (Mauss 2007). Hanford’s waste retrievals have met the tank cleaning requirements of the TPA, but continued improvements to make the retrievals faster and less expensive will be sought during the remaining decades of the tank cleaning work. For example, it cost $50 million to retrieve waste from the first Hanford tank (106C); that expense has now been reduced to about $10 million per tank (Honeyman 2007). Honeyman suggested improved technologies to: Reduce the size of residual clinkers and gravel, Gather the solids without introducing a lot of water, Disaggregate consolidated materials, Handle shear-thickening sludge, Speed up low-water retrieval methods used in leaking tanks, and Deal with the last few percent of waste in tanks. Honeyman also suggested that increasing the amount of material removed from tanks would require some new technology—perhaps improved robotics, chemical dissolution of recalcitrant wastes, and fluid mechanics. Other technology needs for waste retrieval include improving the operating life of in-tank cameras and lights, which are exposed to heat, radiation, and corrosive vapors, and improved techniques for installing openings in the top of the waste tanks (called “risers”) in order to gain better access to the waste for sampling and retrieval (Brouns 2007). Meeting needs for waste characterization for retrieval would also help provide information needed for waste processing. These include: Better ways to mix and sample double-shell tank waste,
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Advice on the Department of Energy’s Cleanup Technology Roadmap: Gaps and Bridges Measurements of HLW slurry hardness and abrasiveness, Online monitoring of the percent of solids in slurry, and Waste slurry transport characterization and pipeline unplugging (Brouns 2007). Tank Closure Brouns (2007) cited technology needs for tank closure as being: Postretrieval, long-term immobilization of residues, Pipeline characterization, and Demonstration of the closure and monitoring of a given waste tank area. A draft environmental impact statement (EIS) for tank closure is expected in early 2009 with a final EIS and Record of Decision perhaps a year later. Although there has been no official word, it is anticipated that closure will proceed as it has at Idaho and the Savannah River Site, which is filling the tank with multiple layers of tailored grout, grouting pipes associated with the tank, and then covering the tank or group of tanks with a low-permeability clay cap. Roadmap Area: Groundwater and Soil Remediation For over five decades, liquid contaminants (~450 billion gallons) were released to the ground through injection wells, French drains, trenches, ponds, and cribs, contaminating both the vadose zone and groundwater (Thompson 2007). Two federal- and state-licensed liquid treatment plants were built in the early 1990s enabling better monitoring and control of the previously untreated discharge water (Gephart 2003). Untreated wastewater has not been discharged into the ground at Hanford since 1995. The groundwater under about 80 square miles (15 percent) of the site is contaminated with regulated constituents at concentrations exceeding the drinking water limits. Radioactive and chemical contaminants in groundwater include, but are not limited to, tritium, iodine-129, Tc-99, uranium, Sr-90, nitrate, carbon tetrachloride, trichloroethene, and hexavalent chromium (Thompson 2007; Uziemblo 2007). There are 761 buried waste sites in the River Corridor project (i.e., sites located along the Columbia River) and 850 on the Central Plateau where the 200 East and 200 West Areas are located. There is also extensive contamination in the vadose zone at the site. Hanford groundwater does not directly serve as a source of potable water for municipal or private wells. However, Hanford groundwater does
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Advice on the Department of Energy’s Cleanup Technology Roadmap: Gaps and Bridges flow into the Columbia River where most downstream municipalities receive their drinking water. Mercury contamination is not a major issue at Hanford (Morse 2007; Uziemblo 2007). DOE, EPA, and the Washington State Department of Ecology have developed a remediation plan for protecting the Columbia River Corridor. The Groundwater Remediation Project is largely responsible for ensuring the plan is implemented. The goals of the program are to prevent contaminated groundwater from migrating to the Columbia River, avoid groundwater contamination in the future, and remediate existing contamination (Jewell 2008). The primary groundwater contaminant plumes of concern are in the 100 and 300 Areas that adjoin the Columbia River. This is where former reactors were built, nuclear fuel development took place, and research laboratories were located. Contaminants of concern include chromium, strontium-90, and uranium with co-contaminants nitrate and trichloroethene (Thompson 2007). The primary groundwater contaminant plumes of concern for river protection in the 200 Area, located at the center of Hanford and generally associated with waste from plutonium reprocessing, are carbon tetrachloride, uranium, technetium-99, and iodine-129 (Thompson 2007). Approximately 16,000 m (or 16 km) of Columbia River shoreline receive contaminated groundwater migrating from beneath Hanford (Thompson 2007). The Groundwater Remediation Project pays close attention to five practical actions: Remediate High-Risk Waste Sites—Clean up waste sites that pose the highest risk to groundwater; Shrink the Contaminated Area—Reduce the contaminated surface area, so as many areas as possible will no longer pose a threat to groundwater; Reduce Recharge—Reduce the transport of contaminants to groundwater from water released onto the soil; Remediate Groundwater—Complete remedial actions at pump-and-treat sites; and Monitor Groundwater—Determine the groundwater monitoring needs for long-term stewardship of the Central Plateau and evaluate new technologies that may be more effective (Jewell 2008). Ongoing Columbia River Protection Projects include well-established groundwater control measures as well as technologies requiring applied or fundamental research. For example, the carbon tetrachloride plume is presently undergoing pump and treat, a method widely used for plume control. Vapor extraction of carbon tetrachloride began in 1992 followed by groundwater extraction 2 years later. An in situ reducing barrier was
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Advice on the Department of Energy’s Cleanup Technology Roadmap: Gaps and Bridges installed and began operating in 2002 to transform hexavalent chromium into the much less soluble Cr(III). A portion of the barrier is now losing reducing capacity and research into a method to mend the barrier is ongoing (Peterson 2007). Barrier systems offer plume containment, but do not actively remediate source zones. Because the latter is desirable, alternative methods to treat chromium and accelerate cleanup are also listed as needs. Within the 200 Areas, the vadose zone varies in thickness from 50 m to 100 m and contaminants exist throughout the full thickness at various locations. Remediation methods for deep, unsaturated soils are not well known. Hanford, as well as at all of the other DOE sites visited by the committee, will rely on engineered caps and barriers to prevent water from carrying contaminants out of areas where solid wastes or contaminated materials are disposed onsite. A Hanford-designed prototype surface barrier, referred to as the Hanford barrier, is a 2.5-hectare multilayered, vegetated, capillary barrier composed mainly of stable natural materials and designed to isolate buried wastes for about 1,000 years. While not all near-surface disposals at Hanford will require the degree of protection offered by the Hanford Barrier, Ward (2007) stated that the results of tests and monitoring of the barrier’s performance can be used to guide the design of more modest covers tailored to achieve the waste isolation needs of individual sites. To do so, it will be necessary to determine moisture flux through representative waste sites, including vegetated and graveled surfaces, account for seasonal variations in precipitation and heating, and from this information develop robust infiltration barriers for sites where contaminants will be temporarily or permanently left in place. Thompson (2007) reported that a 2006 audit by the Government Accountability Office found fault with DOE’s remediation efforts to prevent contaminants from reaching the Columbia River. The audit concluded that technology used in several remedies is not performing satisfactorily, and that there is a lack of new technologies to address contamination issues. Thompson also listed key contaminants that had raised congressional concerns in 2006. These were in two categories: Contaminants currently entering the river—including hexavalent chromium in the 100 Area reactor sites, Sr-90 at N-reactor, uranium in the 300 Area, and tritium and I-129 from 200 East Area; and Contaminants from the central plateau (200 Area) that may reach the river based on their half-lives, mobility, and inventory—including uranium, Tc-99, and carbon tetrachloride. Stewart (2007) provided an overview of near-term geoscience challenges that PNNL addresses at Hanford. These include:
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Advice on the Department of Energy’s Cleanup Technology Roadmap: Gaps and Bridges The complex geohydrology at the groundwater–Columbia River interface and within the subsurface of the Central Plateau where most Hanford contaminants are in surface facilities, underground tanks, or already released into the ground; Hydrology and geophysics characterization and remediation of the deep vadose zone; Specific geochemistry issues, including Sr-90 around N-reactor, uranium in the 300 Area; and uranium, Tc-99, carbon tetrachloride, and plutonium in the Central Plateau; and Reactive transport modeling of contaminants in complex subsurface physical and geochemical settings. To address these challenges, Stewart described several PNNL-led strategic initiatives aligned with site needs. Among the needs are cost-effective, in situ technologies to remediate chlorinated organics. Treatment of these species in deep vadose or tight (low-permeability) zones is particularly problematic. She also stated that mobile ions such as Tc-99, U, and Pu, which are prevalent at multiple sites, are difficult to treat in situ, especially in the deep vadose zone. Stewart noted that simple conceptualizations do not always adequately represent complex subsurface conditions; hence the need for a framework for translating science into conceptual and numerical models, as well as protocols for selecting and implementing numerical models to adequately address complexity of the geohydrologic environment. As long-term needs, she included cost-effective approaches to monitor residual contamination and to verify the performance of site remediation activities. She concluded that sampling and characterization technology, modeling, in situ technology, and long-term monitoring are common challenges at DOE sites (Stewart 2007). From the perspective of the site cleanup contractor, Fluor Hanford, Peterson (2007) described the following challenges: Develop cost-effective in situ remediation of carbon tetrachloride and hexavalent chromium in the vadose zone, Develop cost-effective in situ remediation for radionuclides in the deep vadose zone, Develop numerical models that include chemical reactions by contaminants and their transport in groundwater and the vadose zone, and Develop improved, cost-effective methods for subsurface access to support characterization and remediation.
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Advice on the Department of Energy’s Cleanup Technology Roadmap: Gaps and Bridges Roadmap Area: Decontamination and Decommissioning (D&D) The D&D of the many inactive sites at Hanford has been a large part of the overall cleanup efforts that have been ongoing for the past 20 years at Hanford. The site is still facing a significant amount of D&D work, including 486 structures/facilities in the River Corridor project and over 950 structures/facilities on the Central Plateau (Romine 2007). The River Corridor project includes Hanford’s former production reactors, fuel fabrication, and laboratory facilities. For this project, most cleanup decisions have been made and cleanup has been initiated. For example, all reactor support structures are being removed, leaving only the reactor’s core enclosure. As of 2007, four of Hanford’s nine heavily reinforced concrete reactor buildings were “cocooned” to be left in place for 75 years to allow decay of most contaminants and future decisions as to their further D&D (NRC 2005). Hanford’s B Reactor, the world’s first full-scale operating reactor, is designated as a National Landmark and will be used as a Manhattan Project museum. It will not be cocooned like the other 8 reactors. The land in the river corridor will be available for other purposes such as conservation, tribal, recreational, and industrial use after cleanup (Romine 2007). The 75-square-mile Central Plateau houses fuel reprocessing and waste management facilities, including the five very large “canyon” facilities used for reprocessing irradiated spent fuel from Hanford reactors. The Central Plateau is the last remaining major area where cleanup decisions are yet to be made. According to Romine (2007) the end-state assumptions are that: The Central Plateau will remain under federal control indefinitely, Institutional controls will remain in place for the foreseeable future, and Legacy TRU-contaminated materials and soils will be left in place. As an example of the D&D challenges posed by the canyons, the Purex canyon is approximately 1,000 feet long with walls up to 7 feet thick. Contamination and radiation levels preclude human entry into former fuel reprocessing cells (DOE 1997). There are also two tunnels near the Purex plant containing failed equipment, D&D, and other debris from Purex and the 300 Area located on 24 railroad cars (Gephart 2003). Contaminants include lead, mercury, cadmium, barium, plutonium, and miscellaneous fission products. The equipment contains solids and perhaps liquids. Perhaps 2 million curies of radioactivity exist in the tunnels. This will pose a challenge for D&D efforts. Records and access to the tunnels are not readily available (Hughes et al. 1994). Romine (2007) stated that the baseline for canyon disposition is to seal
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Advice on the Department of Energy’s Cleanup Technology Roadmap: Gaps and Bridges the canyons in place rather than removing them. Given this plan, modeling efforts will be necessary to determine contaminants that can be disposed inside a canyon building without adversely impacting human health or the environment (Romine 2007). Other modeling work to support the baseline will be to investigate the long-term stability of the structures as well as grout added during the D&D. In addition Romine noted the needs for field screening methods to characterize hazardous and TRU contaminants in the canyons and for multipurpose cost-effective robotic vehicles to perform D&D tasks. A major challenge for EM is to balance actual demolition work with long-term requirements for the larger, complex facilities. Engineering work for decommissioning a reactor could take 5 years to complete, while other facilities might only take 6 months. Most major D&D seems to have been pushed into the future. Reactors have been cocooned and reprocessing canyons stabilized with the hard and expensive part being in abeyance. For closure, the long-term performance of cement/grout is pivotal. These materials comprise the structure of facilities to be collapsed on themselves as well as possibly used to fill pipes, vessels, reprocessing cells, galleries, and other void spaces. There is a need to better understand the long-term performance of cement and the surface barriers that may eventually cover these facilities. Asbestos siding (transite) is also an issue on this site as on other DOE sites (Romine 2007). Roadmap Area: Spent Fuel and Nuclear Materials SNF There are 2,100 metric tons of SNF, mostly N-reactor fuel, which is zirconium-clad uranium metal at Hanford. The plan is to send it to a deep geologic repository, such as DOE’s planned Yucca Mountain repository. However, it is unclear that the fuel will meet the waste acceptance criteria for repository disposal and whether the repository will open. If not, other options for spent fuel management must be examined, including onsite storage and fuel reprocessing at Hanford or elsewhere (Gephart 2003). Each option will have unique science and technology needs. K-Basin Sludge Sludge that has been retrieved from K-basin arose from sloughing of uranium metal from N-reactor fuel stored for a prolonged time underwater in the basin, corroded fuel components and uranium, wind-borne soils that settled in the basin, and basin operations. The sludge is heterogeneous and contains a highly variable mix of chemicals, uranium metal, and other ra-
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Advice on the Department of Energy’s Cleanup Technology Roadmap: Gaps and Bridges dionuclides. They are among the most dangerous materials on the Hanford site. The uranium metal is pyrophoric and reacts with water to produce hydrogen, and there is no efficient way to measure the amount of the uranium metal (Delegard et al. 2007). The retrieved sludge has been containerized and is being stored in three locations in K-West area. Disposition plans for the sludge have changed five times since 1995. The plan at the time of the committee’s visit, grouting and disposal in the WIPP, was in the conceptual design phase with additional needs to sample and characterize some of the sludge to determine if it can be accepted at WIPP (Delegard et al. 2007). The current plan is to repackage the sludge in new containers suitable for long-term storage away from the K-West Area while final treatment and disposal options are developed. Cs-137 and Sr-90 Capsules In 1968 Hanford’s B-Plant began separating cesium and strontium from tank waste in order to reduce radioactive decay heat in the waste tanks and allow less-radioactive reprocessed tank liquids to be discharged into the soil. A new facility was added in 1974 to encapsulate these radionuclides, as CsCl and SrF2, inside stainless steel cylinders. The cylinders were intended for use as radiation sources, for example, to sterilize food or medical equipment. Of the 2,217 capsules originally produced, 1,936 are stored in a water pool at B-Plant. The capsules contain 130 megacuries of cesium-137 and strontium-90—about one-third of the total radioactivity on the Hanford site (NRC 2003). The radiation dose adjacent to each capsule is extremely high, more than 1 million rads per hour, which would give a person a lethal dose of radiation in less than 1 minute if standing within 3 feet of an unshielded capsule (Gephart 2003). A decision on how to dispose of the capsules has been deferred. One long-term plan proposes to package them for dry surface storage until they have mostly decayed, which would require some 300 years (about 10 half-lives). Another option could be to open the capsules and mix their contents with the liquid HLW stream to be vitrified in the WTP. CAPABILITIES AND INFRASTRUCTURE AT PNNL PNNL’s total funding was about $760 million in FY 2007. Almost 60 percent of this total was provided by DOE in the areas of science, energy, environment, and national security (Davis 2007). Direct and indirect support from EM was about $91 million (Walton 2008). Presentations from Davis and Walton, as well as PNNL investigators cited in the previous sec-
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Advice on the Department of Energy’s Cleanup Technology Roadmap: Gaps and Bridges tion of this appendix, made it clear that PNNL is closely engaged in EM work relevant to Hanford and, to a lesser extent, the other EM cleanup sites. A recent effort led by PNNL scientists and several other national laboratories outlined many of the major scientific and technical challenges facing DOE across the cleanup sites along with opportunities through focused R&D to reduce the technical risk and uncertainty (Bredt et al. 2008). Davis (2007) stated that a unique feature of PNNL is its fundamental strength in chemistry. Walton (2007) summarized PNNL’s abilities to contribute to EM’s cleanup program. Areas of technical capabilities include: Subsurface science, Chemical process engineering, Ecological science, Integrated assessment and risk analysis, and Environmental and human health and safety. Walton (2008) presented a list of PNNL facilities that he judged would be relevant to meeting EM’s future R&D needs. These are the following: Environmental Molecular Sciences Laboratory (EMSL): scientific investigations in biogeochemistry, waste, solution, and materials chemistry, and supercomputing for subsurface fate and transport simulations; laboratory and bench-scale research; and DOE SC user facility, state-of-the art scientific research and computing. Life Sciences Laboratory: subsurface flow-cell biogeochemical fate and transport research; laboratory and bench-scale testing; and radiological and nonradiological soils, solutions, and simulants. Radiochemical Processing Facility: soil and groundwater biogeochemical fate and transport research; waste and process chemistry, physical properties, mixing, transport, separations, and immobilization; laboratory and bench-scale testing with bench tops, hoods, and hot cells; and category-II nuclear facility for highly radioactive spent fuels, tank waste, contaminated soils and solutions, as well as spiked simulants.
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Advice on the Department of Energy’s Cleanup Technology Roadmap: Gaps and Bridges 336 High Bay: process mixing, retrieval, gas retention and release (safety) testing; laboratory and bench-scale testing with bench tops and hoods; large pilot- and full-scale testing with supporting labs, bench tops, and hoods; and non-radiological chemical and physical simulants. Applied Process Engineering Laboratory (APEL): mixing, chemical processing and filtration, waste forms, materials, physical and chemical properties, glass development and testing; laboratory, bench, and small pilot-scale testing; and non-radiological chemical and physical simulants. Process Development Laboratory (PDLE, PDLW): process mixing, slurry transport, chemical processing, and filtration; large pilot- and full-scale testing (e.g. full-scale piping and pumps); and nonradiological chemical and physical simulants. Relevant to facility needs, Mauss stated that appropriate testing is the key to technology utilization. New technologies should be tested as part of an integrated system, not as individual components. They should be tested at applicable scales with appropriate wastes, and the effects on a new technology in downstream processes should be fully understood (Mauss 2007). REFERENCES Bagaasen, L. 2007. Example of integration of science and engineering on the Bulk Vitrification Project. Presented to the Committee on Development and Implementation of a Cleanup Technology Roadmap. Hanford, Richland, WA, November 1. Bredt, P., A.R. Felmy, P.A. Gauglitz, D. Hobbs, S. Krahn, N. Machara, M. McIlwain, B.A. Moyer, A.P. Poloski, K. Subramanian, J.D. Vienna, and B. Wilmarth. . 2008. Scientific Opportunities to Reduce Risk in Nuclear Process Science. PNNL-17699. Richland, WA: Pacific Northwest National Laboratory. Available at http://www.pnl.gov/main/publications/external/technical_reports/PNNL-17699.pdf. Brouns, T. 2007. Challenges to cleanup: River Protection Project technology needs and technical challenges. Presented to the Committee on Development and Implementation of a Cleanup Technology Roadmap. Hanford, Richland, WA, October 31. Colson, S.D., R.E. Gephart, V.L. Hunter, J, Janata, and L.G. Morgan. 1997. A Risk Based Focused Decision-Management Approach for Justifying Characterization of Hanford Tank Waste, Rev. 2. PNNL-11231. Richland, WA: Pacific Northwest National Laboratory.
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Advice on the Department of Energy’s Cleanup Technology Roadmap: Gaps and Bridges Davis, M. 2007. Welcome: The National Academies Committee on Development and Implementation of a Cleanup Technology Roadmap. Presented to the Committee on Develop- ment and Implementation of a Cleanup Technology Roadmap. Hanford, Richland, WA, October 31. Delegard, C.H., A.J. Schmidt, R.B. Baker, J.P. Sloughter, and W.W. Rutherford. 2007. Challenges to cleanup: K-basin sludge. Presented to the Committee on Development and Implementation of a Cleanup Technology Roadmap. Hanford, Richland, WA, October 31. DOE (U.S. Department of Energy). 1997a. Integration Plan for Environmental Monitoring, Performance Agreement SM 7.2.1. U.S. Department of Energy. Fluor Daniel Hanford, Inc. DOE. 2008. EM Science and Technology Roadmap: Reducing the Uncertainty in the EM Program. Washington, DC: DOE. DOE-ORP/RL (Department of Energy Richland Operations Office and the Office of River Protection). 2007. Hanford Federal Facility Agreement and Consent Order: Tri-Party Agreement. Available at http://www.hanford.gov/?page=91&parent=0. Gephart, R.E. 2003. Hanford: A conversation about nuclear waste cleanup. Presented to the Committee on Development and Implementation of a Cleanup Technology Roadmap, Hanford, Richland, WA, October 31. Gephart, R.E. 2007. Overview of Hanford plutonium production and waste/nuclear material legacy. Presented to the Committee on Development and Implementation of a Cleanup Technology Roadmap. Hanford: Richland, WA, October 31. Honeyman, J. 2007. Hanford HLW program—Challenges to cleanup. Presented to the Committee on Development and Implementation of a Cleanup Technology Roadmap, Hanford, Richland, WA, October 31. Hughes, M.C., L.M. Douglas, and S.G. Marske. 1994. Accelerated Decontamination and Decommissioning at the Hanford Site. WHO-SA-2131-FP. Prepared for the U.S. Department of Energy. Richland, WA: Westinghouse Hanford Company. Available at http://www.osti.gov/bridge/servlets/purl/10118729-hIJzCh/native/10118729.pdf. Jewell, G. 2008. Groundwater at the Hanford Site. U.S. Department of Energy. Available at http://www.hanford.gov/cp/gpp/. Accessed January 24, 2008. Mauss, B. 2007. Hanford HLW program: Challenges to cleanup. Presented to the Committee on Development and Implementation of a Cleanup Technology Roadmap, Hanford, Richland, WA, October 31. Michener, T. 2007. M-3: Mixing systems. Presented to the Committee on Development and Implementation of a Cleanup Technology Roadmap, Hanford, Richland, WA, October 31. Morse, J. 2007. Hanford cleanup. Presented to the Committee on Development and Implementation of a Cleanup Technology Roadmap, Hanford, Richland, WA, October 31. NRC (National Research Council). 2003. Improving the Scientific Basis for Managing DOE’s Excess Nuclear Materials and Spent Nuclear Fuel. Washington, DC: The National Academies Press. NRC. 2005. Improving the Characterization and Treatment of Radioactive Wastes for the Department of Energy’s Accelerated Site Cleanup Program. Washington, DC: The National Academies Press. NRC. 2006. Tank Waste Retrieval, Processing, and On-Site Disposal at Three Department of Energy Sites: Final Report. Washington, DC: The National Academies Press. Peterson, S. 2007. Technology challenges for Hanford soil and groundwater remediation. Presented to the Committee on Development and Implementation of a Cleanup Technology Roadmap, Hanford, Richland, WA, October 31.
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Advice on the Department of Energy’s Cleanup Technology Roadmap: Gaps and Bridges Romine, L.D. 2007. Deactivation and decommissioning. Presented to the Committee on Development and Implementation of a Cleanup Technology Roadmap, Hanford, Richland, WA, October 31. Smith, R.I. 2007. Concerns about the current WTP system. Presented to the Committee on Development and Implementation of a Cleanup Technology Roadmap, Hanford, Richland, WA, October 24. Stewart, T. (2007). Challenges to Cleanup: Soils and Groundwater Remediation. Presented to the Committee on Development and Implementation of a Cleanup Technology Roadmap, Hanford, Richland, WA, October 31. Tamosaitis. 2007. Waste Treatment Plant Project: Technical accomplishments, needs, and challenges. Presented to the Committee on Development and Implementation of a Cleanup Technology Roadmap, Hanford, Richland, WA, October 31. Thompson. 2007. Hanford Groundwater Overview—Challenges to cleanup: DOE-RL Groundwater Project. Presented to the Committee on Development and Implementation of a Cleanup Technology Roadmap, Hanford, Richland, WA, October 31. Uziemblo, N. 2007. Washington State Department of Ecology Nuclear Waste Program: Hanford’s Long-Term Cleanup Problems. Presented to the Committee on Development and Implementation of a Cleanup Technology Roadmap, Hanford, Richland, WA, October 31. Walton, T. 2007. Enabling EM’s cleanup mission with science and technology. Presented to the Committee on Development and Implementation of a Cleanup Technology Roadmap, Hanford, Richland, WA, October 31. Walton, T. 2008. Critical PNNL Laboratories Supporting DOE EM. Presented to the Committee on Development and Implementation of a Cleanup Technology Roadmap, Washington, DC, April 28. Ward, A. 2007. Prototype Hanford Surface Barrier. Presented to the Committee on Development and Implementation of a Cleanup Technology Roadmap, Hanford, Richland, WA, November 2.