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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 1,189 records · Page 66
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Preliminary performance assessment for the Waste Management Area C at the Hanford site in southeast Washington - 15331

A performance assessment of Single-Shell Tank Waste Management Area C located at the U.S. Department of Energy's Hanford Site in southeastern Washington is being conducted to satisfy the requirements of the Hanford Federal Facility Agreement and Consent Order, as well as other Federal requirements and State-approved closure plans and permits. The Waste Management Area C performance assessment assesses the fate, transport, and impacts of radionuclides and hazardous chemicals within residual wastes left in tanks and ancillary equipment and facilities in their assumed closed configuration and the subsequent risks to humans into the far future. The part of the performance assessment focused on radiological impacts is being developed to meet the requirements for a closure authorization under U.S. Department of Energy Order 435.1 that include a waste incidental to reprocessing determination for residual wastes remaining in tanks, ancillary equipment, and facilities. An additional part of the performance assessment will evaluate human health and environmental impacts from hazardous chemical inventories in residual wastes remaining in Waste Management Area C tanks, ancillary equipment, and facilities needed to meet the requirements for permitted closure under the Resource Conservation and Recovery Act of 1976. Preliminary results of the performance assessment are evaluating the groundwater and air pathways to determine radiation exposure once radionuclides are released to the environment due to degradation of the engineered barriers. Per DOE Order 435.1, results of the preliminary analyses are being compared to the performance objectives during the 1,000-year post-closure period of compliance. Per the Order, performance assessment results are also being compared to the performance measures related to acute and chronic inadvertent intruder analyses and groundwater protection. (authors)

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

Canada's Underground Research Laboratory (1980-2014) - 16274

In 1980, Canada initiated a long-term, comprehensive research and development program of geologic characterization and large-scale in situ geotechnical experiments in a subsurface facility, the Underground Research Laboratory (URL). The URL was excavated specifically to evaluate the concept of permanent disposal of used CANDU{sup R} nuclear reactor fuel in a deep geological repository (DGR) constructed in Canadian Shield granite. Key phases of the URL included siting, detailed site characterization and monitoring, construction, operation, decommissioning, and closure. Much collaborative research with international organizations was undertaken at the URL and continues, even after the closure of the facility, through the ongoing Enhanced Sealing Project (ESP). The ESP monitors the engineered performance of a full-scale composite shaft seal that was emplaced during URL closure to permanently seal the main URL access shaft across a sub-horizontal hydraulically active fracture zone. Currently the ESP is jointly funded by Canadian Nuclear Laboratories (CNL) (Canada), Posiva (Finland), and Andra (France), and monitoring is planned to continue until the end of 2016. Decades of programmatic experience at the URL have shown that knowledge continuity is integral to supporting the development of a safe geological disposal facility for high level nuclear waste. This paper outlines the history of the URL and describes some technical lessons learned from its 30-plus years of construction, operation, and closure activities. (authors)

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

Ion Exchange Column Thermal Modeling: Prevention of Process Effluent Boiling - 18577

The Savannah River Site treats and disposes of legacy high-level waste, which resulted from 60 years of nuclear material production, medical research, and other nuclear related work. Complex mixtures of soluble and insoluble solids occupy tanks of which the South Carolina Department of Health and Environmental Control recognizes as the single largest environmental risk state-wide. The risk is reduced through removal, treatment, and solidification of decontaminated salt waste. Presently, SRS decontaminates the soluble salt component of the waste, a solution containing actinides and cesium, via implementation of the Actinide Removal Process and the Modular Caustic Side Solvent- Extraction Unit. Caustic solvent extraction is set to increase in scale by late 2018, with startup of the newly constructed Salt Waste Processing Facility. In conjunction with Salt Waste Processing Facility startup, Savannah River Remediation has been tasked by the Department of Energy to demonstrate modular ion exchange technology. The Tank Closure Cesium Removal project aims to demonstrate the feasibility of modular ion exchange processes for future Department of Energy applications. The Tank Closure Cesium Removal system is scheduled to begin operation in mid-2018. Dissolved salt solution, or influent, will be fed through a filter and ion exchange columns in lead-lag configuration, producing effluent. The effluent is fed to a separate high-level waste tank, for future disposition at Salt-stone Production Facility. Once the demonstration project is complete, the loaded ion exchange columns will be purged, dried, and placed in interim safe storage, awaiting final disposition. The ion exchange media selected for the Tank Closure Cesium Removal system is Honeywell UOP IONSIV{sup C} R-9120. The media is a prime candidate for separation of cesium from radioactive high-level waste. UOP R-9120{sup C} is inorganic and has high capacity, selectivity, and affinity for cesium. During operation, influent is fed to the ion exchange columns, contacting UOP R-9210{sup C} packed within the media vessel. Contact initiates loading of isotopes, and given ample time the solid phase (ion exchange media) and solution achieve thermodynamic equilibrium. UOP R-9120{sup C} is a prime candidate for separation of cesium and dissolved fission products. Although the properties of UOP R-9120{sup C} are favorable for separation, the same properties lead to accumulation of a heat source in the ion exchange bed. Cesium-137 and its daughter product, barium-137 m, generate a clear majority of heat (i.e. ∼ 94%). During operation salt solution flows through each column and transports heat from the ion exchange bed. Once operation is terminated, the effluent contained within the porous bed volume becomes essentially static. In the absence of engineering controls, the heat generated may boil the effluent. Rapid vaporization of aqueous salt solution would lead to bed over pressurization. Over pressurization and an associated release of high-level waste would result in adverse impacts to human health and the environment. This paper focuses on modeling the heat transfer associated with the Tank Closure Cesium Removal system ion exchange column. The model evaluates the maximum heat generation and the associated radionuclide loadings that prevent boiling within of the media vessel, under no flow conditions. A safety significant control, maintaining loadings less than the established loading limit ensures associated impacts to human health and the environment are prevented. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2019

Development of a Preliminary Performance Assessment to Support Single-Shell Tank Waste Retrieval - 19446

A preliminary Performance Assessment (PA) of Single-Shell Tank (SST) Waste Management Area A-AX (WMA A-AX) located at DoE's Hanford Site in southeastern Washington is being conducted to satisfy the requirements of the Hanford Federal Facility Agreement and Consent Order (HFFACO), as well as other Federal and State requirements of closure plans and permits. The WMA A-AX PA effort is assessing the fate, transport, and impacts of radionuclides and hazardous chemicals within residual wastes left in tanks, ancillary equipment, and facilities in their assumed closed configuration, and the subsequent risks to humans into the far future. WMA A-AX includes the 241-A Tank Farm (A Farm), the 241-AX Tank Farm (AX Farm), and the ancillary equipment associated with each Farm. There are six underground SSTs in A Farm, and four underground SSTs in AX Farm. Each of these SSTs have a storage capacity of 1,000,000 gallons. A complex waste transfer system of ancillary equipment supported the transfer and storage of waste within WMA A-AX SSTs. This ancillary equipment includes transfer lines, catch tanks, diversion boxes, vaults, valve pits, and other miscellaneous structures. This paper emphasizes the development of the PA effort focused on radiological impacts to meet the requirements for a closure authorization under DOE Order 435.1. Lessons learned from retrieval and development of a recently completed PA of the nearby Waste Management Area C (WMA C) led to the decision to develop a preliminary PA for WMA A-AX prior to initiation of retrieval efforts so that a site-specific risk management capability could be available to support anticipated retrieval decisions. The technical approach for the PA analysis includes developing both a process-level model using site-specific hydrogeological data, as well as a system-level model. The system model is being developed to facilitate uncertainty and sensitivity analyses being conducted in the PA effort. Preliminary results of the DOE Order 435.1 PA are evaluating potential impacts to the groundwater and air pathways to determine radiation exposure once radionuclides are released to the environment from residual waste after closure of the tank farm. To meet other analysis requirements in DOE Order 435.1, the PA effort must also evaluate potential radiological impacts from inadvertent intruder scenarios into the closed WMA A-AX facility. The results of the PA evaluation will be compared to performance objectives and measures in the DOE Order 435.1 to support retrieval and eventual closure decisions at WMA A-AX. (authors)

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

Controlled Nucleation and Stabilization of Ferroelectric Domain Wall Patterns in Epitaxial (110) Bismuth Ferrite Heterostructures

Ferroelectric domain walls, topological entities separating domains of uniform polarization, are promising candidates as active elements for nanoscale memories. In such applications, controlled nucleation and stabilization of domain walls are critical. In this work, using in situ transmission electron microscopy and phase-field simulations, a controlled nucleation of vertically oriented 109° domain walls in (110)-oriented BiFeO 3 (BFO) thin films is reported. In the switching experiment, reversed domains that are nucleated preferentially at the nanoscale edges of the “crest and sag” pattern-like electrode under external bias subsequently grow into a stable stripe configuration. In addition, when triangular pockets (with an in-plane polarization component) are present, these domain walls are pinned to form stable flux-closure domains. Phase field simulations show that i) field enhancement at the edges of the electrode causes site-specific domain nucleation, and ii) the local electrostatics at the domain walls drives the formation of flux closure domains, thus stabilizing the striped pattern, irrespective of the initial configuration. The results demonstrate how flux closure pinning can be exploited in conjunction with electrode patterning and substrate orientation to achieve a desired topological defect configuration. These insights constitute critical advancements in exploiting domain walls in next generation ferroelectronic devices.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2021

Flowback Test Analyses at the Utah Frontier Observatory for Research in Geothermal Energy (FORGE) Site

Abstract In 2017 and 2019, injection testing was carried out in three zones in a vertical well in granite at the Frontier Observatory for Research in Geothermal Energy site near Milford, Utah, USA. In several injection cycles, flowback was implemented rather than shut-in. The goal was to explore an alternative to prolonged shut-in periods for inferring closure stress, formation compressibility, and formation permeability (permeability thickness product). The flowback procedures involved a cyclic flowback/shut-in, while pressure decreased. The flowback data are presented, and analyses are shown. The inferred closure stress(es) from flowback analyses are lower than for equivalent injection cycles that were strictly shut-in. Relatively high formation compressibility obtained from the flowback analyses indicates an extensive, fractured system. This study also includes numerical simulation of the flowback events. The numerical model shows that the rebound pressure is not necessarily the lower bound of the minimum principal stress. The signature of stiffness change can be identified as the process when the depletion mainly transitions from hydraulic fracture to natural fractures from numerical analysis. Overall, flowback potentially has advantages over shut-in because of the reduced time to closure.

15 GEOTHERMAL ENERGY↗
DOE OSTI2019

Hf-W chronology of ordinary chondrites

Fifteen H, L, and LL ordinary chondrites of petrologic types 4–6 have been analyzed for Hf-W isotope systematics to constrain the chronology, internal structure, and thermal history of their parent bodies. For most samples coarse-grained metals plot below the isochrons defined by silicate-dominated fractions which consist of variable mixtures of silicate minerals with tiny metal inclusions. This offset results from an earlier Hf-W closure in the large metal grains and provides a new means for simultaneously determining cooling rates and Hf-W closure ages for individual samples. For most type 5 and 6 samples, cooling rates and Hf-W ages are inversely correlated, indicating that these samples derive from concentrically zoned bodies in which more strongly metamorphosed samples derive from greater depth. These data, therefore, provide strong evidence for a common ‘onion shell’ structure for the H, L, and LL chondrite parent bodies. The cooling rates and Hf-W ages of some type 5 and 6 chondrites overlap, indicating that the Hf-W systematics provide a more robust measure of the thermal history and burial depth of a given sample than the simple petrographic distinction between types 5 and 6. Two type 6 samples deviate from the correlation between cooling rates and Hf-W ages and cooled much faster than expected for their Hf-W age. These samples likely were excavated by impacts that occurred during high-temperature metamorphism and prior to complete closure of the Hf-W system at ~10 Ma after CAI formation. As these impacts would have disturbed the asteroid’s cooling history, these samples likely derive from different bodies than samples with undisturbed cooling histories, implying that ordinary chondrites derive from more than just three parent bodies. The Hf-W data reveal that metal-silicate fractionation among the H, L, and LL groups occurred between ~2 and ~2.7 Ma after CAI formation and, hence, was about coeval to chondrule formation. As both metal-silicate fractionation and chondrule formation occurred prior to chondrite parent body accretion, there should be no ordinary chondrite chondrules that are younger than ~2.7 Ma. In conclusion, ordinary chondrite precursors had lower Hf/W ratios than carbonaceous chondrites, suggesting that inner and outer solar system materials, respectively, were chemically distinct even for refractory elements.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Is There a Scalar Atmospheric Surface Layer Within a Convective Boundary Layer? Implications for Flux Measurements

Top‐down entrainment shapes the vertical gradients of sensible heat, latent heat, and CO 2 fluxes, influencing the interpretation of eddy covariance (EC) measurements in the unstable atmospheric surface layer (ASL). Using large eddy simulations for convective boundary layer flows, we demonstrate that decreased temperature gradients across the entrainment zone increase entrainment fluxes by enhancing the entrainment velocity, amplifying the asymmetry between top‐down and bottom‐up flux contributions. These changes alter scalar flux profiles, causing flux divergence or convergence and leading to the breakdown of the constant flux layer assumption (CFLA) in the ASL. As a result, EC‐measured fluxes either underestimate or overestimate “true” surface fluxes during divergence or convergence phases, contributing to energy balance non‐closure. The varying degrees of the CFLA breakdown are a fundamental cause for the non‐closure issue. These findings highlight the underappreciated role of entrainment in interpreting EC fluxes, addressing non‐closure, and understanding site‐to‐site variability in flux measurements.

eddy covariance fluxes of scalars↗
DOE OSTI2019

Monitoring Potential Transport of Radioactive Contaminants in Shallow Ephemeral Channels: FY2018

Desert Research Institute (DRI) is conducting a field assessment of the potential for contaminated soil to be transported from the Smoky Site Contamination Area (CA) as a result of storm runoff. This activity supports U.S. Department of Energy (DOE) Environmental Management Nevada Program (EM NV) efforts to establish post-closure monitoring plans for the Smoky Site Soils Corrective Action Unit (CAU) 550. The work is intended to confirm the likely mechanism of transport and determine the meteorological conditions that might cause the movement of contaminated soils, as well as determine the particle size fraction that is most closely associated with transported radionuclide-contaminated soils. These data will facilitate the design of the appropriate post-closure monitoring program. In 2011, DRI installed a meteorological monitoring station on the west side of the Smoky Site CA and a hydrologic (runoff) monitoring station within the CA, near the east side. The meteorological station collects air temperature, wind speed, wind direction, relative humidity, precipitation, solar radiation, barometric pressure, soil temperature, and soil water content data. The maximum, minimum, and average or total values (as appropriate) for each of these parameters are recorded for each 10-minute interval. The maximum, minimum, and average water depth in the flume installed at the hydrologic station are also recorded for each 10-minute interval. This report presents the data collected from these stations during fiscal year (FY) 2018. During the FY2018 reporting period, the warmest months were June, July, and August and the coldest were December through March. Solar radiation showed the same seasonal trend. Monthly mean wind speeds were highest in the spring (March through May) and early summer (June). Winds were generally from the west during the summer and from the north throughout the fall and winter. The monthly average relative humidity ranged from the mid-teens to approximately 50 percent. Humidity was lowest in the fall and highest in the winter. Monthly total precipitation ranged from 0 in October, December, and June to approximately 1.38 inches (in) (35.05 millimeters [mm]) in July. Total precipitation for FY2018 was 3.86 in (98.04 mm). During the reporting period, two runoff events were recorded at the flume. One occurred on July 14, 2018, in response to precipitation earlier the same day. This event produced a peak water depth of 11.26 in (28.60 centimeters [cm]) in the flume, which is equivalent to a discharge of 1.86 cubic feet per second (cfs) (0.05 cubic meters per second [cm/s]) and a velocity of 3.97 feet per second (fps) (1.21 meters per second [m/s]) through the flume. Applying the flume hydraulic measurements to the channel geometry at the nearest surveyed cross-section it was determined that the velocity through the channel was 1.29 fps (0.39 m/s), which is sufficient to transport silts and fine sands. The second flow event occurred in response to earlier precipitation on September 4, 2018. This event produced a peak water depth of 0.78 in (1.98 cm) in the flume, which is equivalent to a discharge of 0.03 cfs (0.001 cm/s) and a velocity of 1.17 fps (0.36 m/s) through the flume. Applying the flume hydraulic measurements to the channel geometry at the nearest surveyed cross-section it was determined that the velocity through the channel was 0.03 fps (0.01 m/s). Although neither runoff event produced sufficient flow velocities through the natural channel to cause local erosion and transport of coarser bedload materials, the velocity of the first runoff event was sufficient to transport silts and fine sands, which have been shown to be preferentially associated with radionuclide contaminants. Therefore, a sampling event was planned after the first flow event in conjunction with a periodic maintenance inspection. As no suspended load sampling is available at this location, bedload samples were collected from the vicinity of the flume on August 7, 2018. The collected sediment was separated into three particle size fractions and each fraction was analyzed for americium-241 (Am-241), plutonium-238 (Pu-238), and plutonium-239/240 (Pu-239/240) by alpha spectrometry. The two smaller particle size fractions had higher concentrations of all three radionuclides than the largest particle size fraction. Additionally, Pu-239/240 had the highest concentration and Pu-238 had the lowest concentration in all samples. The same relationship between the concentrations of Pu-238 and Pu-239/240 was seen in samples reported in FY2013 and FY2014. Observation of meteorological and environmental conditions that lead to storm runoff will help identify parameters and threshold conditions that should be incorporated into postclosure monitoring plans for this and similar sites as well as aid in determining appropriate closure strategies for other Soils CAUs.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1994

Review of modelling small-crack behavior and fatigue-life predictions for aluminum alloys

The small-crack effect, where small fatigue cracks grow faster and at lower stress-intensity factors than large cracks, has been found to be significant for many materials and loading conditions. In this paper, plasticity effects and crack-closure modelling of small fatigue cracks are reviewed. A crack-closure model with a cyclic-plastic-zone-corrected effective stress-intensity factor range (related to the cyclic J-integral) and microstructural data on crack-initiation sites were used to calculate small-crack growth rates and fatigue lives for unnotched and notched specimens made of two aluminum alloys. The crack-closure transient from the plastic wake was shown to be the dominant cause of the small-crack effect and plasticity effects on the cyclic-plastic-zone-corrected stress-intensity factor range were negligible except at extremely high stress levels. Small-crack growth rates and fatigue lives under both constant-amplitude and spectrum loading from tests and analyses agreed well.

CRACK CLOSURE MODELLING↗
DOE OSTI2015

Unique natural system modeling aspects of the H-Tank Farm at the Savannah river site - 15271

The U.S. Department of Energy (DOE) is in the process of closing radioactive waste storage tanks at the Savannah River Site (SRS). One of the key technical documents supporting closure and regulatory decision documents is the Performance Assessment (PA). PAs within the DOE complex are performance-based, risk-informed analyses of the fate and transport of residual contaminants, in this case any residual material remaining following cleaning and closure of the tank systems. There are two active radioactive waste storage facilities at SRS, F-Tank Farm (FTF) and H-Tank Farm (HTF), which consist of 51 carbon steel waste tanks. To date, six tanks have been emptied and closed in FTF. Activities are currently in progress to support closure of the first tanks in HTF. A PA has been developed for HTF and includes modeling that takes into account the unique aspects of the natural system associated with HTF. These unique aspects include the water table elevation in relation to the tanks and the complex flow patterns of the groundwater beneath HTF. (authors)

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

Integration of performance assessments and 3116 basis documents within the Savannah River Site liquid waste facilities - 15375

The end of the Cold War has left a legacy of over 136 million liters (36 million gallons) of radioactive waste in the aging waste tanks at the Department of Energy's Savannah River Site (SRS). A robust program is in place to remove waste from these tanks, treat the waste to separate it into a relatively small volume of high-level waste and a large volume of low-level waste, and to actively dispose of the low-level waste on-site. This process allows the US Department of Energy (DOE) to move forward with closure of the cleaned waste tanks and associated ancillary structures. To support performance-based, risk decision making for closure and disposal activities, three individual performance assessments (PAs) have been developed - salt-stone Disposal Facility, F-Tank Farm and H-Tank Farm. In addition, three Waste Determinations (WDs) have been made by the Secretary of Energy, in consultation with the Nuclear Regulatory Commission (NRC), under the authority of Section 3116 of the Ronald W. Reagan National Defense Authorization Act for Fiscal Year 2005 (NDAA Section 3116). To support these waste determination decisions, individual '3116 Basis Documents' were developed that describe the assumptions and conditions under which the criteria outlined in NDAA Section 3116 are met. The development of each of the PAs represented a long and arduous effort that involved the development of both deterministic and probabilistic conceptual models of the facilities, the development of assumptions and associated ranges, uncertainty and sensitivity analyses, model data collection and analyses, writing of the actual performance assessment, internal and external peer reviews, and ultimately approval by DOE. Similarly, the development of the 3116 Basis Documents represents similar time and financial commitments. At the end of these efforts, after years of preparation and millions of dollars in investment, we have thousands of pages of highly technical text, tables of data and hundreds of graphs and charts all contained in a series of thick binders that fit neatly on the shelf of a bookcase. We were done - right? Actually, we were just getting started. Performance Assessments and 3116 Basis Documents are living documents that shape day-to-day and long-term decision making in the operation of a low-level waste disposal facility (e.g., salt-stone Disposal Facility) or in area closure activities (e.g., F-Tank Farm or H-Tank Farm). Although these documents do not contain specifically described requirements per se, they do utilize specific assumptions that, if changed significantly, could result in no longer being able to demonstrate that there is reasonable assurance that the required performance objectives or the criteria from NDAA Section 3116 can be met. Savannah River Remediation LLC (SRR), the contractor responsible for Liquid Waste operations at SRS, has not only developed the PAs and 3116 Basis Documents to support this work and shepherded these documents through the DOE approval process, but has also developed the processes and procedures to ensure the successful implementation and integration of these documents into day-to-day decision making within the associated facilities. This paper describes these processes, including the Un-reviewed Waste Management Question process and the PA Maintenance process, and provides specific examples of their successful implementation. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2019

A Practical Approach of Mining Operational Risks in Cigeo - A field-test - 19349

Andra is currently completing the detailed engineering phase of the stepwise design development of Cigeo (the French HLW and IL-LLW Deep Geological Repository, aka DGR). Various technical issues are at stake, including the risk management requirements linked to the safety of 'Mining Operations' (i.e. occupational safety issues related to underground excavation/dismantling works at some 500 m of depth), at different stages of the DGR life cycle (i.e. from its construction start-up to its final closure and future monitoring/or conversely a decision of waste retrieval). These occupational safety requirements have a significant impact on Cigeo's design, its progressive construction and later closure. On a shorter term, one must demonstrate that the design bases are technically sound and that the solutions selected (to build, operate, close the DGR infrastructures or conversely retrieve the waste) are both feasible and safe. In that sense (and following an identification of operational risks during construction), Andra focused on two sensitive cases: - The construction of large diameter drift crossings, in particular those related to the connection between a transfer drift (main) and a IL-LLW disposal vault (i.e. during construction operations), - The partial dismantling of a drift concrete lining (made of concrete segment rings, erected and placed by a TBM) at time of construction of a horizontal seal (i.e. during closure operations). The discussion starts with a description of the geotechnical conditions prevailing at the (French) Bure site, in the Callovo-Oxfordian (COx) claystone formation. Then the paper presents the Cigeo underground architecture (at large) and the specific structural choices made (at the end of the detailed engineering phase) for drifts, disposal vaults and seals. The discussion on construction - deconstruction challenges for each of the critical issues cited above provides an opportunity to explain the operational sequences (and how the methodology selected enables to reduce the risks). The following part of the paper focuses the technological demonstration (an in-situ test to be planned in detail) of a partial dismantling of the concrete segments rings forming the support lining of two tunnels previously built in the Meuse/Haute-Marne URL (Underground Research Laboratory) infrastructures, combined with the construction of a specific drift crossing. In this dismantling and construction test, the technical demonstration objective is three-fold: - The capacity to lay down compressible arch segments and support (by bolts and mesh) the rock after the lining removal, - The capacity to excavate and line the drift crossing, - The structural / geomechanical behavior (evolution with time) of the rock and lining compared with that of 'neighboring' zones. This paper provides a timeline of the tests. Should the results obtained deliver some positive perspectives of technical feasibility (and convincing operational safety) Andra will incorporate this dismantling/construction solution in the 'design freeze' of the DGR underground infrastructures. The positive outcomes of this technical test campaign will also provide 'elements of proof' for the instruction of the Cigeo licensing (a process likely to take place between 2020 and 2024) by the French Nuclear Safety Authority (ASN). (authors)

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

Single Bubble Drag Force Evaluation in Turbulent Flow based on DNS Results

Two-phase turbulent flows are widely encountered in the light water reactor engineering. The interaction between liquid phase and gas phase is bi-directional: the liquid turbulence influences the dispersion and distribution of the bubbles which in turn modulates the liquid turbulence with bubble-induced turbulence. Considering a single bubble, the effect of homogeneous turbulent flow is to modify the drag force compared to that in laminar flow. The bubble can modify the homogeneous turbulence through formation of vorticities behind the bubble. The correct description of the closure laws for the interfacial forces is of great importance in numerical simulation of bubbly flows. Various closure laws for the drag coefficient have been proposed in the literature in the last few decades. Among them, Tomiyama proposed a widely accepted correlation based on spherical bubbles in pure systems. While the development of closure model for two-phase laminar flow has reached a certain level of confidence, more studies and investigations are required for turbulent flows. In this paper, we want to numerically analyze the influence of homogeneous turbulent flow on the drag force experienced by a single bubble and compare its behavior with the laminar flow conditions based on Tomiyama's correlation. A set of parametric studies will be performed to justify the relationship between typical two-phase turbulent flow parameters and drag force. (authors)

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2016

The Potential of Computational Fluid Dynamics Simulation on Serial Monitoring of Hemodynamic Change in Type B Aortic Dissection

PurposeWe aimed to assess the potential of computational fluid dynamics simulation (CFD) in detecting changes in pressure and flow velocity in response to morphological changes in type B aortic dissection.Materials and MethodsPressure and velocity in four morphological models of type B aortic dissection before and after closure of the entry tear were calculated with CFD and analyzed for changes among the different scenarios. The control model (Model 1) was patient specific and built from the DICOM data of CTA, which bore one entry tear and three re-entry tears. Models 2–4 were modifications of Model 1, with two re-entry tears less in Model 2, one re-entry tear more in Model 3, and a larger entry tear in Model 4.ResultsThe pressure and velocity pertaining to each of the morphological models were unique. Changes in pressure and velocity findings were accountable by the changes in morphological features of the different models. There was no blood flow in the false lumen across the entry tear after its closure, the blood flow direction across the re-entry tears was reversed after closure of the entry tear.ConclusionCFD simulation is probably useful to detect hemodynamic changes in the true and false lumens of type B aortic dissection in response to morphological changes, it may potentially be developed into a non-invasive and patient-specific tool for serial monitoring of hemodynamic changes of type B aortic dissection before and after treatment.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2021

Toward Predictive RANS and SRS Computations of Turbulent External Flows of Practical Interest

In this work, we investigate the main challenges to prediction of turbulent external flows of practical interest with Reynolds-Averaged Navier–Stokes equations (RANS) and Scale-Resolving Simulation (SRS) models. This represents a crucial step toward further developing and establishing these formulations so they can be confidently utilized in engineering problems without reference data. The study initiates by identifying the major challenges to prediction. A literature review is performed to illustrate their effects in RANS and SRS computations. Afterward, we evaluate the impact of the challenges to prediction by analyzing representative statistically steady and unsteady flows with prominent RANS and SRS methods. These include multiple turbulent viscosity and second-moment RANS closures, and hybrid and bridging SRS models. The results demonstrate the potential of the selected SRS models to predict engineering flows. Yet, they also show the importance of considering the challenges to prediction during the setup and conduction of numerical experiments. These can suppress the advantages of using SRS formulations. The data also indicate that only SRS models can confidently predict statistically unsteady flows. In contrast, the results demonstrate that mean-flow quantities of statistically steady flows can be efficiently calculated with RANS closures, especially second-moment closures. Among the selected SRS methods, bridging models reveal better suited for prediction due to their ability to prevent commutation errors and enable the robust evaluation of numerical and modeling errors. This last property allows the use of a new validation technique that does not require reference data.

42 ENGINEERING↗
DOE OSTI2015

Drake passage and central american seaway controls on the distribution of the oceanic carbon reservoir

A coupled carbon/climate model is used to explore the impact of Drake Passage opening and Central American Seaway closure on the distribution of carbon in the global oceans. We find that gateway evolution likely played an important role in setting the modern day distribution of oceanic dissolved inorganic carbon (DIC), which is currently characterized by relatively low concentrations in the Atlantic ocean, and high concentrations in the Southern, Indian, and Pacific oceans. In agreement with previous studies, we find a closed Drake Passage in the presence of an open Central American Seaway results in suppressed Atlantic meridional overturning and enhanced southern hemispheric deep convection. Opening of the Drake Passage triggers Antarctic Circumpolar Current flow and a weak Atlantic meridional overturning circulation (AMOC). Subsequent Central American Seaway closure reinforces the AMOC while also stagnating equatorial Pacific subsurface waters. These gateway-derived oceanographic changes are reflected in large shifts to the global distribution of DIC. An initially closed Drake Passage results in high DIC concentrations in the Atlantic and Arctic oceans, and lower DIC concentrations in the Pacific/Indian/Southern oceans. Opening Drake Passage reverses this gradient by lowering mid-depth Atlantic and Arctic DIC concentrations and raising deep Pacific/Indian/Southern Ocean DIC concentrations. Central American Seaway closure further reinforces this trend through additional Atlantic mid-depth DIC decreases, as well as Pacific mid-depth DIC concentration increases, with the net effect being a transition to a modern distribution of oceanic DIC.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2020

CFD-DEM and PR-DNS studies of low-temperature densely packed beds

Over the past few decades, granular media is gaining attention as a viable option for heat transfer fluids (HTFs). Several research efforts are studying the use of particle-based heat transfer fluids in a wide variety of applications. With this motivation, the current work focusses on analyzing the different heat transfer mechanisms in low-temperature mono-sized densely packed granular media. To study the heat transfer behavior of granular media at different scales, the current work employs a two-way coupled computational strategy. The motion of particles is solved using the Discrete Element Method (DEM) and the interstitial air is solved using a Finite-Volume (CFD) approach. The Open-Source library CFDEM Coupling® is used in the current study to join the Finite Volume PISO solver of OpenFOAM® and the DEM solver of LIGGGHTS®. Typically, particle-particle contact conduction and particle-air convection are the most popular closure models. But recent research identified a different heat transfer phenomenon in packed beds that cannot be identified by conduction or convection models. While closure models were developed to implement this on a CFD-DEM framework, they did not capture the effect of intra-particulate thermal gradients on this phenomenon. Hence the current work also employs Particle-Resolved Direct Numerical Simulations (PR-DNS) to gain valuable insights allowing for the modification of existing models. A new closure model is then proposed here and is implemented in the CFD-DEM framework. This model provides key insights into the different heat transfer mechanism of packed beds.

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