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At least 469 records · Page 26
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Coupling LaGrit unstructured mesh generation and model setup with TOUGH2 flow and transport: A case study

Furthermore, there are many applications in science and engineering modeling where an accurate representation of a complex model geometry in the form of a mesh is important. In applications of flow and transport in subsurface porous media, this is manifest in models that must capture complex geologic stratigraphy, structure (faults, folds, erosion, deposition) and infrastructure (tunnels, boreholes, excavations). Model setup, defined as the activities of geometry definition, mesh generation (creation, optimization, modification, refine, de-refine, smooth), assigning material properties, initial conditions and boundary conditions requires specialized software tools to automate and streamline the process. In addition, some model setup tools will provide more utility if they are designed to interface with and meet the needs of a particular flow and transport software suite. A control volume discretization that uses a two point flux approximation is for example most accurate when the underlying control volumes are 2D or 3D Voronoi tessellations. In this paper we will present the coupling of LaGriT, a mesh generation and model setup software suite and TOUGH2 to model subsurface flow problems and we show an example of how LaGriT can be used as a model setup tool for the generation of a Voronoi mesh for the simulation program TOUGH2. To generate the MESH file for TOUGH2 from the LaGriT output a standalone module Lagrit2Tough2 was developed, which is presented here and will be included in a future release of LaGriT. Here in this paper an alternative method to generate a Voronoi mesh for TOUGH2 with LaGriT is presented and thanks to the modular and command based structure of LaGriT this method is well suited to generating a mesh for complex models.

58 GEOSCIENCES↗
DOE OSTI2021

Cs retention and diffusion in C-S-H at different Ca/Si ratio

Cement and concrete are commonly used in the construction of repository sites for radioactive wastes. The correct isolation of those contaminants requires good adsorption and low diffusion rates. Both parameters are highly affected by many factors, such as pH, temperature or composition. The large variability of experimental conditions and formulations makes it extraordinarily difficult to tackle the influence of each of them independently in experimental samples. To this effect, molecular dynamics simulations have been employed in this study to investigate the role of the composition in the capacity to retain Cs and diffusivity of these ions in calcium silicate hydrate (C-S-H) gel pores. The results indicate that the adsorption of Cs ions is worsened at high Ca/Si ratios due to a lower interaction of the cations with the C-S-H surface, while hydrophilicity of the C-S-H nanopore rises, resulting in higher long-range ordering and lower diffusion coefficients of Cs ions.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Potential for biocolloid transport of cesium at high ionic strength

In subsurface repositories, active bacterial populations may directly influence the fate and transport of radionuclides including in salt repository systems like the Waste Isolation Pilot Plant in Carlsbad, NM. This research quantified the potential for transport and interaction between Chromohalobacter sp. and Cs in a high ionic strength system (2.6 M NaCl) containing natural minerals. Mini-column experiments showed that Chromohalobacter moved nearly un-retarded under these conditions and that there was neither association of Cs with microbes nor dolomite despite changes in bacterial metabolic phases. Growth batch experiments that monitored the potential uptake of Cs into the microbes confirmed results in column experiments where intracellular uptake of Cs by Chromohalobacter was not observed. These results show that Cs may be highly mobile if released in high ionic strength systems and/or carbonate minerals with negligible inhibition by these microbes.

dolomite, cesium, biocolloid, intracellular uptake↗
DOE OSTI2015

Swelling properties of montmorillonite and beidellite clay minerals from molecular simulation: Comparison of temperature interlayer cation, and charge location effects

In this study, the swelling properties of smectite clay minerals are relevant to many engineering applications including environmental remediation, repository design for nuclear waste disposal, borehole stability in drilling operations, and additives for numerous industrial processes and commercial products. We used molecular dynamics and grand canonical Monte Carlo simulations to study the effects of layer charge location, interlayer cation, and temperature on intracrystalline swelling of montmorillonite and beidellite clay minerals. For a beidellite model with layer charge exclusively in the tetrahedral sheet, strong ion–surface interactions shift the onset of the two-layer hydrate to higher water contents. In contrast, for a montmorillonite model with layer charge exclusively in the octahedral sheet, weaker ion–surface interactions result in the formation of fully hydrated ions (two-layer hydrate) at much lower water contents. Clay hydration enthalpies and interlayer atomic density profiles are consistent with the swelling results. Water adsorption isotherms from grand canonical Monte Carlo simulations are used to relate interlayer hydration states to relative humidity, in good agreement with experimental findings.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Monticello Mill Tailings Site, Operable Unit lll, Annual Groundwater Report, May 2015 Through April 2016

This report provides the annual analysis of water quality restoration progress, cumulative through April 2016, for Operable Unit (OU) III, surface water and groundwater, of the U.S. Department of Energy (DOE) Office of Legacy Management (LM) Monticello Mill Tailings Site (MMTS). The MMTS is a Comprehensive Environmental Response, Compensation, and Liability Act National Priorities List site located in and near the city of Monticello, San Juan County, Utah. MMTS comprises the 110-acre site of a former uranium- and vanadium-ore-processing mill (mill site) and 1700 acres of surrounding private and municipal property. Milling operations generated 2.5 million cubic yards of waste (tailings) from 1942 to 1960. The tailings were impounded at four locations on the mill site. Inorganic constituents in the tailings drained from the impoundments to contaminate local surface water (Montezuma Creek) and groundwater in the underlying alluvial aquifer. Mill tailings dispersed by wind and water also contaminated properties surrounding and downstream of the mill site. Remedial actions to remove and isolate radiologically contaminated soil, sediment, and debris from the former mill site, Operable Unit I (OU I), and surrounding properties (OU II) were completed in 1999 with the encapsulation of the wastes in an engineered repository located on DOE property 1 mile south of the former mill site. This effectively removed the primary source of groundwater contamination; however, contamination of groundwater and surface water remains within OU III at levels that exceed water quality protection standards. Uranium is the primary contaminant of concern (COC). LM implemented monitored natural attenuation with institutional controls as the OU III remedy in 2004. Because groundwater restoration proceeded more slowly than expected and did not meet performance criteria established in the OU III Record of Decision (June 2004), LM implemented a contingency action in 2009 by an Explanation of Significant Difference to include a pump-and­ treat system using a single extraction well and treatment by zero-valent iron (ex situ treatment system). The contingency action was optimized in 2015 with the installation of8 extraction wells and 16 monitoring wells in a focused area of the aquifer, the area of attainment (AOA). Contaminated water is treated by solar evaporation at an existing facility at the LM repository.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2015

Monticello Mill Tailings Site Operable Unit III Annual Groundwater Report May 2014 Through April 2015, October 2015

This report provides the annual analysis of water quality restoration progress, cumulative through April 2015, for Operable Unit (OU) III, surface water and groundwater, of the U.S. Department of Energy (DOE) Office of Legacy Management Monticello Mill Tailings Site (MMTS). The MMTS is a Comprehensive Environmental Response, Compensation, and Liability Act National Priorities List site located in and near the city of Monticello, San Juan County, Utah. MMTS comprises the 110-acre site of a former uranium- and vanadium-ore-processing mill (mill site) and 1,700 acres of surrounding private and municipal property. Milling operations generated 2.5 million cubic yards of waste (tailings) from 1942 to 1960. The tailings were impounded at four locations on the mill site. Inorganic constituents in the tailings drained from the impoundments to contaminate local surface water (Montezuma Creek) and groundwater in the underlying alluvial aquifer. Mill tailings dispersed by wind and water also contaminated properties surrounding and downstream of the mill site. Remedial actions to remove and isolate radiologically contaminated soil, sediment, and debris from the former mill site (OU I) and surrounding properties (OU II) were completed in 1999 with the encapsulation of the wastes in an engineered repository located on DOE property 1 mile south of the former mill site. Contamination of groundwater and surface water remains within OU III at levels that exceed water quality protection standards. Uranium is the primary contaminant of concern. LM implemented monitored natural attenuation with institutional controls as the OU III remedy in 2004. Because groundwater restoration proceeded more slowly than expected and did not meet performance criteria established in the OU III Record of Decision (June 2004), LM implemented a contingency action in 2009 by an Explanation of Significant Difference to include a pump-and-treat system using a single extraction well and treatment by zero-valent iron (ex-situ treatment system). The contingency action was optimized in 2015 with the installation of 8 extraction wells and 16 monitoring wells in a focused area of the aquifer (area of attainment). Contaminated water is treated by solar evaporation at an existing onsite LM facility. Environmental monitoring at OU III consists of twice-yearly (April and October) collection and analysis of hydrologic and water-quality data from an established network of observation wells, seeps, and surface water locations. The scope of monitoring was expanded in 2009 for the ex situ treatment system and in 2015 for the remedy optimization system. Operation and monitoring of the ex situ treatment system was discontinued in 2014 with the start-up of the remedy optimization system. No data anomalies for OU III water quality trending or restoration progress are identified for the May 2014 through April 2015 reporting period. Although some regions of the aquifer demonstrate decreasing concentration trends, such trending is not evident for the bulk of the aquifer and a prolonged restoration period is indicated. The groundwater contingency remedy optimization system captures significant contaminant mass (primarily uranium) from the area of attainment; however, because that system only became operational in 2015, a long-term forecast of restoration progress is premature.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2017

The Role of Chromohalobacter on Transport of Lanthanides and Cesium in the Dolomite Mineral System

The chemical behavior of actinide series elements and fission products is a concern for the Waste Isolation Pilot Plant repository due to their uncertain mobility in the subsurface salt formation. In this work, we are observing the behavior of the halophilic bacterium, Chromohalobacter, and its effect on the mobility of lanthanides and cesium in the presence of dolomite. Batch and minicolumn experiments were conducted with Cs + and lanthanides (Nd 3+ , Eu 3+ ) to quantify potential transport with bacteria. Preliminary results show that Cs does not interact strongly with dolomite or Chromohalobacter, while the lanthanides can interact strongly with both minerals and bacteria depending on which the Ln contacts first.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2024

Proceedings of the 13 th US/German Workshop on Salt Repository Research, Design, and Operation

This report summarizes the proceedings of the 13 th US/German Workshop on Salt Repository Research, Design, and Operation hosted by Sandia National Laboratories on June 20-23, 2023, in Santa Fe, New Mexico, USA. Over 60 participants attended, representing Germany, United States, the Netherlands, Australia, and the United Kingdom, along with the IAEA. The purpose of the US/German Workshop is to foster in-person collaboration and dialogue amongst salt repository researchers and nuclear waste disposal implementers across international organizations. The workshop included five sessions of topical presentations and two breakout sessions to promote additional discussion on compelling topics.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2015

Separation and recovery of uranium from residues to allow disposal as VLLW - 15379

During fabrication of uranium fuel, significant amounts of uranium contaminated wastes are generated. The uranium concentration in the waste is typically 1-10% in weight. With this uranium concentration, the residues constitute long lived Low Level Waste (LL-LLW) which need to be disposed of in a repository specifically for this type of waste. Through recovery of uranium from the primary waste, the potential for reducing the concentration of uranium to such low levels that the remaining waste qualifies as Very Low Level Waste (VLLW) are significant. The remaining waste could then be disposed of in a less costly disposal than the primary waste. A method for recovery of uranium from waste has been developed and used in Sweden and includes leaching with sulphuric acid, solvent extraction and precipitation. The final result is ammonium di-uranate (ADU). The remaining waste typically has residual uranium content in the range of 100 g uranium per tonne of waste. In several countries this would permit disposal at a hazardous waste landfill site after conditional clearance. During the development process, it has been shown that for certain types of waste it's possible to reduce the uranium concentration even further. The paper gives an overview of the technology, its applications as well as advantages and limitations. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2018

A Method for the Assessment of Operational Safety of DGR Using Scenario Development - 18187

This paper treats the subject of the accident analysis for the operational phase of a deep geological repository (DGR) for radioactive waste. It describes the further development of the procedures used in the accident analysis. The procedures of the scenario development for the post-closure phase of DGRs are used as example for this further development. Nine international projects regarding scenario development were analyzed to create an advanced and more systematic method for the accident analysis. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2020

Panel Session 89: Progress on Deep Repository Around the World

This panel focused on the progress of deep repository programs, worldwide. While efforts on a deep geological repository for SNF/UNF and HLW in the USA were terminated in 2010, several other repository programs continue to make considerable progress 10 and deserve to be recognized. Panelists from national, multi-national, and international repository programs and organizations reported on the status and future plans as well as the perceived reasons underlying the success and the failure of components of their respective repository program. This session provided a forum for interested parties to present, exchange, and take advantage of, as appropriate, repository progress, challenges, concepts/designs and other lessons learned around the world, including site characterization, site selection, research and development, licensing, construction, operation, and public acceptance and participation. Panelists with presentations: Switzerland's Geological Repository Program for Radioactive Waste (Tim Vietor); Update on NWMO's Progress in Implementing Canada's Plan (Sarah Hirschorn); Cigeo Project Progress and Next Milestones (Corinne Bauer)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2018

Optimising National WM Strategies through early consideration of Nuclear Safeguards - 18607

International Atomic Energy Agency (IAEA) safeguards stand alongside safety and security as one of the three pillars for prudent management of all nuclear material, including nuclear waste. Although safety considerations, including public and environmental radiation protection, are the traditional drivers of waste management strategies, there is a requirement for nuclear safeguards in shaping and quantifying long-term solutions for special classes of radioactive waste. This is especially important when considering the disposal of nuclear material in a repository that could be released from regulatory oversight for radiation protection after a period of institutional control, as some safeguards oversight would still be required. Failure to consider nuclear safeguards at the early stages of planning may alternatively lead to excessive volumes for disposal or the need to recondition already treated wastes. At the very least, safeguards measures should be considered before countries seek to dispose of legacy nuclear materials, decommissioning wastes and other materials containing uranium, thorium or plutonium in an operating repository. Nuclear safeguards are the set of tools and techniques used by the IAEA to verify that countries comply with their international obligations not to divert nuclear materials to nuclear explosive devices. Under the Nuclear Non-Proliferation Treaty (NPT), nuclear safeguards apply to all uranium, thorium and plutonium held in non-weapons NPT states, with limited exceptions. In nuclear-weapon states, much of their material is likewise subject to IAEA safeguards through conditions in agreements with respective suppliers of the uranium. Under IAEA safeguards, such nuclear material must remain accounted for and accessible for periodic verification-analogous to the safety concepts of reversibility and retrievability. Nevertheless, safeguards requirements can be terminated - provided that the State and the [IAEA] agree that such nuclear material is practicably irrecoverable - through dilution or immobilisation in solid form (such as cement, glass or ceramic). This means candidate material can be disposed of as non- nuclear material, with no further safeguards requirements, provided this criterion is met. Unlike radiological wastes where repository design strongly influences pathways for radionuclide migration and overall safety performance, repository design is not a factor in considering the termination of safeguards on nuclear material. This paper looks at similarities and differences in the safety, security and safeguards regulatory requirements for the management of radioactive waste and nuclear material in Australia. In particular, it outlines recent experience gained from participation in Australia's waste acceptance criteria working group for a national low-level waste repository and intermediate-level waste store, as well as from Australia's overall waste management strategy. These items of work have coincided with the IAEA update of its internal policy on termination of safeguards on nuclear material. Australia's experience shows how inclusion of safeguards criteria in the planning process is leading to optimisations in choice of facility concepts, project sequencing and equitable distribution of economic risk. By considering the three pillars-safety, security and safeguards-early on in the planning process, Australia's waste management strategy will provide a benchmark for other states in establishing and updating their own waste acceptance criteria for the disposal of nuclear material. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2024

FIU Project 2: Environmental Remediation Science & Technology [Slides]

FIU’s research under this project involves conducting basic and applied science to fill knowledge gaps and validate potential remediation technologies for contaminated soil and groundwater and the assessment of the fate and transport of contaminants in the environment. The aim of FIU’s research is to reduce the potential for contaminant mobility or toxicity in the surface and subsurface through the development and application of state-of-the-art scientific and environmental remediation technologies at the Hanford Site, Savannah River Site (SRS), and the Waste Isolation Pilot Plant (WIPP), which is the Nation’s only mined geologic repository for permanent disposal of transuranic waste. FIU collaborates with scientists from Pacific Northwest National Laboratory (PNNL), Savannah River National Laboratory (SRNL), Savannah River Ecology Laboratory (SREL), Los Alamos National Laboratory (LANL) and the DOE Carlsbad Field Office (CBFO) in order to plan and execute research that is synergistic with the work being conducted at the sites, and that supports the resolution of critical science and engineering needs which leads to a better understanding of the long-term behavior of subsurface contaminants. The knowledge gained through this research will be used to transform experimental and modeling innovations into practical applications deployed at the sites to support EM’s primary goal of expediting the closure of major contaminated soil and groundwater sites and waste units. Collaborative relationships between FIU and the national laboratories have provided large benefits over the years to FIU, the national laboratories, the DOE complex, and the DOE EM mission. By working closely with the national laboratories, FIU’s research is not only closely aligned with the cleanup mission priorities at the DOE sites, but complements and supports ongoing work at the national laboratories for screening of new remedial technologies. This coordination and leveraging of research efforts results in time- and cost-savings, and will accelerate progress of the DOE EM environmental restoration mission.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

What's the big deal with TA-55's trash?

There's a beast of hazardous waste, and we're learning how to tame it. Plutonium and production activities are ongoing at TA-55, which means the beast of hazardous waste is always looming around the corner. The Laboratory must dispose of this delicate type of waste properly and swiftly. Learning from previous snags and pitfalls in an incredibly complex process, TA-55 leadership and staff have worked together to greatly improve and streamline waste processes. The result: As of the last week of fiscal year 2020, 42 shipments containing 1,275 containers of transuranic (TRU) waste were sent to the Waste Isolation Pilot Plant (WIPP) in southern New Mexico, the nation’s only repository for defense-generated TRU waste. In FY 2019, we shipped less than half that amount.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2016

Methods to Capture the Tritium Released by Recovery/Recycle of Zirconium from Used Fuel Cladding: A Review

After uranium, the second largest mass contained in most used nuclear fuel (UNF) is the zirconium-based Zircaloy{sup R} cladding in the fuel cladding which accounts for about 25% of the mass. In current practice, the cladding requires disposal in a geologic repository. Zirconium may be recovered from the Zircaloy cladding of UNF for recycle. Alternatively, it may be decontaminated to recategorize it as low-level waste. Either approach reduces the quantities of high-level waste destined for a geologic repository, thereby reducing the overall cost of recycling UNF. Process development studies are under way in the United States and Republic of Korea based on dry chlorination using a mixture of chlorine (Cl{sub 2}) and an inert carrier such as argon (Ar) to convert the zirconium in the alloy, which is greater than 98 wt% of the alloy mass, to zirconium tetrachloride (ZrCl{sub 4}). The ZrCl{sub 4} is volatile and is easily separated from the non-volatile components. The residues include non-volatile chlorides such as CrCl{sub 3}, oxychlorides and oxides. The product ZrCl{sub 4} is recovered as a solid salt by condensation when cooled to less than about 300 deg. C. Feasibility tests with actual UNF cladding have demonstrated that the recovered zirconium chloride salt is sufficiently separated from fuel and fission product radionuclides that it emanates no significant dose and can be handled without shielding. Several methods for capturing tritium released from cladding during the chlorination process have been identified. A detailed description of the methodologies, advantages, drawbacks, and conceptual flowsheets will be presented. (authors)

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2015

Impacts of an additional exhaust shaft on WIPP performance - 15170

The Waste Isolation Pilot Plant (WIPP), located in southeastern New Mexico, has been developed by the U.S. Department of Energy (DOE) for the geologic (deep underground) disposal of transuranic (TRU) waste. WIPP performance assessment (PA) demonstrates repository performance from facility closure to 10,000 years after closure. The recent radiological release event at the WIPP site has temporarily halted waste emplacement activities at the facility. A modified ventilation system is envisioned that will provide sufficient airflow necessary for the resumption of full-rate disposal operations in the future. A primary component of the modified ventilation system is an additional exhaust shaft in the north end of the repository. There are four shafts currently in the repository north end, namely a salt handling shaft, an exhaust shaft, a waste shaft, and an air intake shaft. These shafts are combined into a single composite shaft in WIPP PA that captures the combined impacts of all of them. The proposed additional exhaust shaft is combined with the four existing shafts in the repository model to determine its impacts on long-term repository performance. Moreover, mined volume in the repository north end is modified in the repository representation so as to include additional drifts created to access the new shaft. Computed gas and brine flow behaviors corresponding to the repository with the additional exhaust shaft are compared to those obtained in the PA executed for the 2014 Compliance Re-certification Application (the CRA-2014 PA). Results show that the repository with an additional exhaust shaft and drifts yields brine and gas flow behaviors similar to the current repository configuration. It is concluded that WIPP continues to satisfy regulatory compliance limits with the addition of an exhaust shaft and its access drifts, with compliance curves like those found in the CRA-2014 PA for total normalized releases. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2015

Update on site selection for Canada's national repository for used nuclear fuel - 15481

In 2007, the Government of Canada selected Adaptive Phased Management as Canada's plan that provides for long-term management of Canada's used nuclear fuel in a deep geological repository, located in an informed and willing host. The Nuclear Waste Management Organization is tasked through federal legislation to select the site and develop and manage all aspects of Canada's plan. In May 2010 the Nuclear Waste Management Organization published and initiated the site selection process that serves as a road map for decision-making on the location for the deep geological repository. The Nuclear Waste Management Organization continues to lead the site selection process for a deep geological repository for the long term management of Canada's used nuclear fuel and centre of expertise. The screening down process is advancing and, from an initial starting point of 22 communities expressing interest in learning about the project, as of November 2014 14 communities are now the focus of more detailed studies. Preliminary assessments are underway with these communities, which is the third step in the 9 step site selection process. Preliminary assessments involve preliminary technical and social desktop and field assessments, engagement activities within and beyond the interested community and seeking involvement of Indigenous peoples and nearby municipalities in the planning and conduct of the work. The paper provides an update on the advancement of the site selection process. It describes the nature of the technical and social studies being conducted at this phase of work, including the progressively more detailed field studies which are the focus of technical work at this stage, approach to engagement and collaboration with communities to direct these studies, and the work underway to ensure the framework used for this assessment and engagement includes the range of priorities and perspectives of First Nations and Metis peoples and communities in the broader area. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗