Advice on the Department of Energy's Cleanup Technology Roadmap Gaps and Bridges (2009) / Chapter Skim
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2 Principal Science and Technology Gaps
2 Principal Science and Technology Gaps
Pages 21-80
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From page 21... ...
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.
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From page 22... ...
2-1 Bitmapped 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.
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From page 23... ...
EM's draft Engineering and Technology Roadmap, issued in April 2007, provided a framework for organizing the committee's fact-finding and deliberations, 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, • The volume of waste affected, • Potential to reduce technical risks (including risk to workers)
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From page 24... ...
WP-2 Low-activity streams from tank waste processing could contain Medium substantial amounts of radionuclides. WP-3 New facility designs, processes, and operations usually rely on Medium pilot-scale testing with simulated rather than actual wastes.
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From page 25... ...
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 suf ficiently 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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From page 26... ...
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.
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From page 27... ...
. SRS tank waste is broadly similar to that at Hanford although it is less heterogeneous chemically (Figure 2.2)
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From page 28... ...
. The INL site still has about 900,000 gallons of acidic liquid waste stored in three stainless steel underground tanks.
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From page 29... ...
; some tanks contain debris, and at SRS cooling coils further inhibit access and waste retrieval (Figure 2.3)
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From page 30... ...
The coils are an obstacle to removing the tank waste at SRS. SOURCE: Department of Energy.
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From page 31... ...
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)
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Relative Rating Criteria 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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From page 33... ...
. The sludge in Hanford and SRS tanks contains most of the waste radionuclides but comprises only about 10 percent of the tank waste volume at each site.
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From page 34... ...
Impact of the Gap The SRS tank closure program cannot proceed without the ability to meet radionuclide separation objectives for its salt waste. Salt processing methods and objectives for the Hanford Waste Treatment Plant (WTP)
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From page 35... ...
Relative Rating Criteria 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 WP-3: New facility designs, processes, and operations usually rely on pilot-scale testing with simulated rather than actual wastes. EM and its contractors are challenged with designing, building, and operating large, expensive, one-of-a-kind waste processing facilities that have major inherent safety risks because of the nature of the waste to be
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From page 36... ...
The committee heard of numerous basic waste processing operations that carry significant technical risk because they cannot be tested on a pilotplant scale with actual wastes, including: • Reliable separation of solids from liquid waste streams to prevent clogging of ion exchange beds or adverse effects on solvent extraction equipment, • Ensuring that shear-thickening (non-Newtonian) sludges can be transported in pipelines without clogging, • Predicting the rate of radiolytic hydrogen generation by process sludges and the release time and rate of the hydrogen, • Predicting the stability and interaction of various process streams to allow for reduced conservatism in the operational safety bases of the tank farms, and • Understanding the effect of impurities and degradation or corrosion products on process performance.
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From page 37... ...
However, one example is the SRS in-tank precipitation pro cess for radiocesium removal, which behaved unexpectedly during a full-scale test with actual radioactive waste and was abandoned (NRC 2000a, 2001a, and Appendix G)
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From page 38... ...
However, the use of computer modeling to replace large pilot- and full-scale testing with simulants carries some technical risk. These technical risks could be reduced if CFD or other models of relatively complex behaviors could be calibrated using data from tests with actual wastes.
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From page 39... ...
A Joule-heated melter is being used at SRS to stabilize high-activity tank waste in borosilicate glass. Hanford is taking a similar approach, but the Hanford WTP is being designed to vitrify both high-activity and low-activity streams from its tanks using different melters for each stream.
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From page 40... ...
These include the diversity of waste input streams, behavior of solids in the system, and process upsets. He listed improved waste forms, glass formulations, and melters as technology needs for enhancing throughput.
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From page 41... ...
Relative Rating Criteria 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 Disturbing the cold cap would increase the load of volatile materials and radionuclides on the melter off-gas system or possibly trap water beneath portions of the melt, which could lead to eruptions of steam and molten glass.
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From page 42... ...
Tank operations and a good deal of site infrastructure will have to remain open and operating to support waste vitrification during these decades. The approximately $500 million per year cost at each site for maintaining its high-activity waste operations is a strong incentive for faster waste processing (Appendixes D and G)
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From page 43... ...
Chromium in Hanford waste will reduce waste loadings in WTP glass unless it is removed in pretreatment or reduced in concentration by blending with low-chromium waste. • Work to develop entirely new, nonborosilicate glass waste forms that can accommodate higher waste loadings and/or loadings of problematic constituents like aluminum, chromium, and sulfate.
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From page 44... ...
Wastes and nuclear materials that do not have a defined disposition path are "orphans." Examples of orphans include: • Over 4,000 cubic meters of calcine at Idaho that may require processing such as vitrification if it cannot be shown to be acceptable for in situ disposal or geologic disposal in its present form; • Idaho's sodium-bearing tank waste, which is presently classified as TRU waste;10 • The waste left in SRS Tank 48 that contains tetraphenyl borate (used in a previous attempt to remove Cs-137 from tank waste) and its degradation products, which may require special processing to convert them into a stream suitable for vitrification at the DWPF; • Spent fuel at Idaho for which adequate characterization to qualify it for disposal is impractical because of the high radiation field and lack of access to the nuclear materials in the sealed packages; • Aluminum-clad N-reactor fuels at Hanford that may not meet criteria for disposal in a deep geologic repository because of their susceptibility to corrosion; • K-basin sludge at Hanford that contains pyrophoric uranium metal; • High-atomic-weight ("heavy")
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From page 45... ...
According to this committee's assessment of information it received, the following have promise for future EM R&D: • A systematic effort to develop the technical basis for alternative characterization, treatment, and disposal options, and for waste acceptance criteria; • A systematic effort to understand the degradation rate of nuclear materials in storage with initial focus on materials stored underwater; • Risk-informed comparison of the alternatives for disposition of INL calcine and SRS Tank 48 waste; and • Improved methods for characterizing highly radioactive spent fuel and nuclear materials inside containers.
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From page 46... ...
. Chemicals, metals, and radionuclides were introduced into the environment at DOE sites through accidental spills and leaks from storage tanks and waste transfer lines and also through intentional disposal via injection wells, disposal pits, and settling ponds.
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From page 47... ...
Several examples illustrate the importance of understanding basic contaminant biogeochemistry and characterizing the properties of the field site adequately when planning whether or how to conduct soil and groundwater remediation: • At Oak Ridge, the levels of mercury in East Fork Poplar Creek, which is downstream from Y-12, have been reduced to meet drinking wa
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From page 48... ...
characterization of the contamination source and factors that control contaminant movements is a technical risk -- simply removing some of the contaminant mass may not cause the expected response in contaminant concentration or movement. Without knowledge of the fundamental processes that interact to determine contaminant mobility and persistence in the spatially heterogeneous geologic settings that exist at each of the DOE sites, it is impossible to complete a reliable risk assessment or plan an effective remedial program.
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From page 49... ...
.13 Examples of Subsurface Science Focus Area projects include PNNL's research on the role of microenvironments and transition zones in the reactive transport of technetium (Tc) , uranium, and plutonium;14 ORNL's research on the biogeochemical transformations that govern mercury speciation at the sediment–water interface;15 and LBNL's research to develop a sustainable systems approach for addressing critical knowledge gaps associated with envi ronmental stewardship of metals and radionuclides in the subsurface.16 Organizations such as the DOE offices of Science and Civilian Radioactive Waste Management, the Environmental Protection Agency (EPA)
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From page 50... ...
The technical challenges in groundwater and soil remediation differ from those in waste processing in terms of the timescales during which the relevant processes operate, access and ability to measure process parameters (reading a gauge versus ascertaining what is going on belowground) , and ability to control the process parameters.
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From page 51... ...
The liquid waste disposed at the BC cribs and trenches represents some of the most concentrated radioactive and hazardous waste disposed to the ground at Hanford. Based on inventory estimates, this site contains the largest inventory of technetium-99 in the Hanford soil.17 The majority of the Tc-99 is believed to be located in the site's vadose zone, which comprises highly stratified glacial-fluvial sediments that give rise to complex subsurface-flow paths (Gee et al.
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From page 52... ...
Relative Rating Criteria 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 18 See: http://homer.ornl.gov/oepa/guidance/cercla/techimpract.pdf.
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From page 53... ...
. Among these, pump and treat is the most commonly used, and it appears to be favored by EM site cleanup contractors (Figure 2.6)
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From page 54... ...
The purpose of the interim remedy for the ~11 km2 CCl4 plume (estimated area exceeding the water quality standard in the upper region of the unconfined aquifer) is to prevent further migration of the portion exceeding 2,000 μg/L.
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From page 55... ...
However, the aquifer itself is relatively poorly characterized, especially with respect to the biogeochemical conditions that can impact the fate of CCl4 and many other mobile groundwater contaminants relevant to EM at the field site, such as nitrate, uranium, and technetium. Similar to some other DOE sites in the western United States, the aquifer is deep and the geologic system is challenging to sample.
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From page 56... ...
. A similar situation exists at Hanford, where pump and treat has controlled a carbon tetrachloride plume but impact on the source and plume longevity is unknown (Sidebar 2.2)
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From page 57... ...
This program consumed much of the OBER Subsurface Science Program and in 2005 was merged with the Environmental Management Science Program to create the ERSP, which supports fundamental, mission-oriented research on DOE legacy waste and priority contaminants. These research programs have generated nearly 1,000 research publications relative to the mechanistic microbiology, fate, and transport issues influencing metals and radionuclides in the subsurface and their potential for bioremediation and immobilization.
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From page 58... ...
The organisms that efficiently degrade contaminants such as trichloroethylene, the predominant VOC at DOE sites, are very specific. Depending on whether the environment is aerobic or anaerobic, completely different organisms and biochemistries operate.
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From page 59... ...
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. Relative Rating Criteria 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 GS-3: The long-term performance of trench caps, liners, and reactive barriers cannot be assessed with current knowledge.
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From page 60... ...
Impact of the Gap Removal and subsequent treatment of wastes at many DOE sites is technically difficult, expensive, and potentially hazardous to workers. As a result, alternative approaches that leave the waste in place, but incorporate robust containment barriers and waste stabilization technologies over the long term (100-1,000 years)
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From page 61... ...
is developing fieldscale performance data for landfill final cover systems based on field data being obtained at a dozen sites representing a variety of geohydrologic conditions.22 ACAP is part of the EPA's National Risk Management Research Laboratory's SITE program established to promote the development of new and innovative technologies used to address hazardous waste problems. Both prescriptive (Resource Conservation and Recovery Act)
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From page 62... ...
3. Many of the barrier systems put in place or proposed at DOE sites are systems that are designed to shed precipitation and/or divert or retard groundwater flow.
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From page 63... ...
Cementitious materials are among the world's most widely used and best understood construction materials. In the EM cleanup program, their high-volume applications include: • Grouting of emptied HLW tanks and associated inter-tank transfer pipes; • Stabilizing LAW in large monoliths, such as the SRS saltstone, or in smaller containers (e.g., 55-gallon drums)
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From page 64... ...
Impact of the Gap The successful grouting of wastes in tanks, pipes, and saltstone is assumed in performance assessments that demonstrate regulatory requirements for tank closure and SRS salt disposal will be met. If the adequate long-term performance of the grout were to be seriously questioned -- and the requirements for the grout's performance and performance period are beyond any direct experience in the construction industry -- then closure of the tanks and SRS salt disposal could become problematical.
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From page 65... ...
It notes on page 90, "some of the assumptions made in the analysis, if incorrect, could lead to noncompliance with the performance objectives." Current Status Cementitious grouts and related materials are routinely used in the construction industry for a wide variety of applications, some of which closely match EM's needs. Where the project requirements are the same as or similar to these routine applications, the DOE can simply use existing technology.
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From page 66... ...
not. For example, it is well known that the pH of cementitious materials decreases over time due to carbonation (reaction with carbon dioxide from the air)
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From page 67... ...
Developing improved and quality-assured methods to measure hydraulic conductivities of very low permeability materials can assist the SRS tank closure program.
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From page 68... ...
All cementitious materials shrink to some degree on hydration, which would leave the pipe less than completely filled. Materials can be engineered to shrink less, and shrinkage-compensating materials can also be designed.
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From page 69... ...
Facilities requiring D&D throughout the DOE complex include reprocessing plants, large production and smaller test reactors, fuel fabrication facilities, gaseous diffusion plants, and laboratories with hot cells -- including all of these facilities' support structures that typically contain ancillary equipment, piping, and ductwork. In many cases there are complicating factors including poor (and continually degrading)
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From page 70... ...
. DD-1: D&D work relies on manual labor for facility characterization, equipment removal, and dismantlement.
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From page 71... ...
Although uncomfort Fig 2-9 able, personal protective equipment like that worn by the worker in this photograph bitmap image is necessary to protect workers from the uptake (skin, mouth, nose) of radioactive or other hazardous substances and from physical hazards.
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From page 72... ...
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.
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From page 73... ...
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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From page 74... ...
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.
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From page 75... ...
Relative Rating Criteria 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 ttp://frhamsafety.com/anti-c/encapsulating_suit.htm.
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From page 76... ...
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.
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From page 77... ...
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.
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From page 78... ...
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. Relative Rating Criteria 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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From page 79... ...
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.
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