Evaluation of THOR Mineralized Waste Forms (Granular and Monolith) for the DOE Advanced Remediation Technologies (ART) Phase 2 Project (open access)

Evaluation of THOR Mineralized Waste Forms (Granular and Monolith) for the DOE Advanced Remediation Technologies (ART) Phase 2 Project

The U.S. Department of Energy's (DOE) Office of River Protection (ORP) is responsible for the retrieval, treatment, immobilization, and disposal of Hanford's tank waste. Currently there are approximately 56 million gallons of highly radioactive mixed wastes awaiting treatment. A key aspect of the River Protection Project (RPP) cleanup mission is to construct and operate the Waste Treatment and Immobilization Plant (WTP). The WTP will separate the tank waste into high-level and low-activity waste (LAW) fractions, both of which will subsequently be vitrified. The projected throughput capacity of the WTP LAW Vitrification Facility is insufficient to complete the RPP mission in the time frame required by the Hanford Federal Facility Agreement and Consent Order, also known as the Tri-Party Agreement (TPA), i.e. December 31, 2047. Therefore, Supplemental Treatment is required both to meet the TPA treatment requirements as well as to more cost effectively complete the tank waste treatment mission. The Supplemental Treatment chosen will immobilize that portion of the retrieved LAW that is not sent to the WTP's LAW Vitrification facility into a solidified waste form. The solidified waste will then be disposed on the Hanford site in the Integrated Disposal Facility (IDF). In addition, the WTP LAW Vitrification facility …
Date: February 2, 2012
Creator: Crawford, Charles L. & Jantzen, Carol M.
System: The UNT Digital Library
Center for the Study of Plasma Microturbulence (open access)

Center for the Study of Plasma Microturbulence

We have discovered a possible "natural fueling" mechanism in tokamak fusion reactors using large scale gyrokinetic turbulence simulation. In the presence of a heat flux dominated tokamak plasma, cold ions naturally pinch radially inward. If cold DT fuel is introduced near the edge using shallow pellet injection, the cold fuel will pinch inward, at the expense of hot helium ash going radially outward. By adjusting the cold DT fuel concentration, the core DT density profiles can be maintained. We have also shown that cold source ions from edge recycling of cold neutrals are pinched radially inward. This mechanism may be important for fully understanding the edge pedestal buildup after an ELM crash. Work includes benchmarking the gyrokinetic turbulence codes in the electromagnetic regime. This includes cyclone base case parameters with an increasing plasma beta. The code comparisons include GEM, GYRO and GENE. There is good linear agreement between the codes using the Cyclone base case, but including electromagnetics and scanning the plasma beta. All the codes have difficulty achieving nonlinear saturation as the kinetic ballooning limit is approached. GEM does not saturate well when beta gets above about 1/2 of the ideal ballooning limit. We find that the lack of …
Date: March 2, 2012
Creator: Parker, Scott E.
System: The UNT Digital Library
Designing Microporus Carbons for Hydrogen Storage Systems (open access)

Designing Microporus Carbons for Hydrogen Storage Systems

An efficient, cost-effective hydrogen storage system is a key enabling technology for the widespread introduction of hydrogen fuel cells to the domestic marketplace. Air Products, an industry leader in hydrogen energy products and systems, recognized this need and responded to the DOE 'Grand Challenge' solicitation (DOE Solicitation DE-PS36-03GO93013) under Category 1 as an industry partner and steering committee member with the National Renewable Energy Laboratory (NREL) in their proposal for a center-of-excellence on Carbon-Based Hydrogen Storage Materials. This center was later renamed the Hydrogen Sorption Center of Excellence (HSCoE). Our proposal, entitled 'Designing Microporous Carbons for Hydrogen Storage Systems,' envisioned a highly synergistic 5-year program with NREL and other national laboratory and university partners.
Date: May 2, 2012
Creator: Cooper, Alan C.
System: The UNT Digital Library
Draft INFL Guideline on SIMS (open access)

Draft INFL Guideline on SIMS

Secondary Ion Mass Spectrometry (SIMS) is used for elemental and isotopic analysis of solid samples. The greatest strength of SIMS is the ability to analyze very small areas (as small as 50 nm using the CAMECA NanoSIMS, for example) and to generate high-spatial resolution maps of the distribution of elements and isotopes within the sample. The measurement of the isotopic composition of sample is usually straightforward, only requiring the analysis of the sample and that of an isotopic reference material for determination of the mass bias of the instrument. Quantification of elements, however, involves the analysis of matrix matched standards for the determination of the relative sensitivity factor (a function of both the element to be analyzed and the matrix). SIMS is commonly used in nuclear forensics for exploring the heterogeneity of the material on fine spatial scale.
Date: April 2, 2012
Creator: Kristo, M J
System: The UNT Digital Library
Center for Technology for Advanced Scientific Component Software (TASCS) (open access)

Center for Technology for Advanced Scientific Component Software (TASCS)

Indiana University’s SWIM activities have primarily been in three areas. All are completed, but we are continuing to work on two of them because refinements are useful to both DoE laboratories and the high performance computing community.
Date: August 2, 2012
Creator: Bramley, Randall B.
System: The UNT Digital Library
MACHINING ELIMINATION THROUGH APPLICATION OF THREAD FORMING FASTENERS IN NET SHAPED CAST HOLES (open access)

MACHINING ELIMINATION THROUGH APPLICATION OF THREAD FORMING FASTENERS IN NET SHAPED CAST HOLES

The ultimate objective of this work was to eliminate approximately 30% of the machining performed in typical automotive engine and transmission plants by using thread forming fasteners in as-cast holes of aluminum and magnesium cast components. The primary issues at the source of engineers’ reluctance to implementing thread forming fasteners in lightweight castings are: * Little proof of consistency of clamp load vs. input torque in either aluminum or magnesium castings. * No known data to understand the effect on consistency of clamp load as casting dies wear. The clamp load consistency concern is founded in the fact that a portion of the input torque used to create clamp load is also used to create threads. The torque used for thread forming may not be consistent due to variations in casting material, hole size and shape due to tooling wear and process variation (thermal and mechanical). There is little data available to understand the magnitude of this concern or to form the basis of potential solutions if the range of clamp load variation is very high (> +/- 30%). The range of variation that can be expected in as-cast hole size and shape over the full life cycle of a …
Date: May 2, 2012
Creator: Cleaver, Ryan J.; Cleaver, Todd H. & Talbott, Richard
System: The UNT Digital Library
Theoretical calculating the thermodynamic properties of solid sorbents for CO{sub 2} capture applications (open access)

Theoretical calculating the thermodynamic properties of solid sorbents for CO{sub 2} capture applications

Since current technologies for capturing CO{sub 2} to fight global climate change are still too energy intensive, there is a critical need for development of new materials that can capture CO{sub 2} reversibly with acceptable energy costs. Accordingly, solid sorbents have been proposed to be used for CO{sub 2} capture applications through a reversible chemical transformation. By combining thermodynamic database mining with first principles density functional theory and phonon lattice dynamics calculations, a theoretical screening methodology to identify the most promising CO{sub 2} sorbent candidates from the vast array of possible solid materials has been proposed and validated. The calculated thermodynamic properties of different classes of solid materials versus temperature and pressure changes were further used to evaluate the equilibrium properties for the CO{sub 2} adsorption/desorption cycles. According to the requirements imposed by the pre- and post- combustion technologies and based on our calculated thermodynamic properties for the CO{sub 2} capture reactions by the solids of interest, we were able to screen only those solid materials for which lower capture energy costs are expected at the desired pressure and temperature conditions. Only those selected CO{sub 2} sorbent candidates were further considered for experimental validations. The ab initio thermodynamic technique has …
Date: November 2, 2012
Creator: Duan, Yuhua
System: The UNT Digital Library
Renewal of Collaborative Research: Economically viable Forest Harvesting Practices that Increase Carbon Sequestration (open access)

Renewal of Collaborative Research: Economically viable Forest Harvesting Practices that Increase Carbon Sequestration

This technical report covers a 3-year cooperative agreement between the University of Maine and the Northeastern Forest Experiment Station that focused on the characterization of forest stands and the assessment of forest carbon storage (see attached for detailed description of the project). The goal of this work was to compare estimates of forest C storage made via remeasurement of FIA-type plots with eddy flux measurements. In addition to relating whole ecosystem estimates of carbon storage to changes in aboveground biomass, we explored methodologies by partitioning growth estimates from periodic inventory measurements into annual estimates. In the final year, we remeasured plots that were subject to a shelterwood harvest over the winter of 2001-02 to assess the production of coarse woody debris by this harvest, to remeasure trees in a long-term stand first established by NASA, to carry out other field activities at Howland, and, to assess the importance of downed and decaying wood as well as standing dead trees to the C inputs to harvested and non harvested plots.
Date: August 2, 2012
Creator: Dail, David Bryan
System: The UNT Digital Library
Summary of Current LLNL Projects with the Russian Federation (open access)

Summary of Current LLNL Projects with the Russian Federation

Developing a sophisticated theory to understand the electronic structure of 5f-metals is a great challenge to solid state physics. Complicated electronic structures of 5f-metals make their properties strongly sensitive to small energy changes produced by the addition of a small amount of alloy, impurities, or crystal structure defects caused by irradiation. A theoretical material science technique applicable to investigate these effects is atomistic simulation using Classical Molecular Dynamics (CMD). In contrast to ab initio techniques, CMD may include several million particles, so that there is a possibility of direct simulation of very low concentration impurities and defects (as well as phenomena such as plasticity and polymorphous transitions) under given conditions. The goal is to develop theoretical models to understand and predict changes in materials properties of actinides caused by self-irradiation.
Date: April 2, 2012
Creator: Schilling, O
System: The UNT Digital Library
Interfacial Engineering for Highly Efficient-Conjugated Polymer-Based Bulk Heterojunction Photovoltaic Devices (open access)

Interfacial Engineering for Highly Efficient-Conjugated Polymer-Based Bulk Heterojunction Photovoltaic Devices

The aim of our proposal is to apply interface engineering approach to improve charge extraction, guide active layer morphology, improve materials compatibility, and ultimately allow the fabrication of high efficiency tandem cells. Specifically, we aim at developing: i. Interfacial engineering using small molecule self-assembled monolayers ii. Nanostructure engineering in OPVs using polymer brushes iii. Development of efficient light harvesting and high mobility materials for OPVs iv. Physical characterization of the nanostructured systems using electrostatic force microscopy, and conducting atomic force microscopy v. All-solution processed organic-based tandem cells using interfacial engineering to optimize the recombination layer currents vi. Theoretical modeling of charge transport in the active semiconducting layer The material development effort is guided by advanced computer modeling and surface/ interface engineering tools to allow us to obtain better understanding of the effect of electrode modifications on OPV performance for the investigation of more elaborate device structures. The materials and devices developed within this program represent a major conceptual advancement using an integrated approach combining rational molecular design, material, interface, process, and device engineering to achieve solar cells with high efficiency, stability, and the potential to be used for large-area roll-to-roll printing. This may create significant impact in lowering manufacturing cost …
Date: April 2, 2012
Creator: Jen, Alex; Ginger, David; Luscombe, Christine & Ma, Hong
System: The UNT Digital Library
SSPC (Solid State Proton Conductors 15 Meeting (open access)

SSPC (Solid State Proton Conductors 15 Meeting

The field of solid state protonics has had a small but dedicated following for the past several decades. The collection of papers compiled in this special issue of Solid State Ionics were presented at the most recent international conference focused specifically on this topic, the 15th International Conference on Solid State Proton Conductors (SSPC-15) held in Santa Barbara, California, United States, August 15-20, 2010. Early recognition of the importance of proton transport in solids led to the establishment of the first meeting in this series in 1981, held in Paris in the form of a Danish-Frenchworkshop. The subsequent thirteen meetingswere all held inWestern Europe,with increasing participation from Asian, Eastern European and North and South American researchers. In recognition of the growing international interest in the field, SSPC-14 was held in Kyoto, Japan. SSPC-15, the first North American meeting in this series, built on the momentum of internationalization achieved in SSPC-14, ensuring that the best and brightest minds continue to contribute to the important problems still facing the understanding and manipulation of proton transport in solids. This occasion warrants an update to the SSPC history, and is given. Overall, the oxide proton conductors were the topic of greatest interest, reflecting the …
Date: May 2, 2012
Creator: Speakers; Yamaguchi, Shu; Rossman, George; Islam, M. Saiful; Gomez, Maria & Paddison, Stephen
System: The UNT Digital Library
Environmental Monitoring Plan, Revision 6 (open access)

Environmental Monitoring Plan, Revision 6

The purpose of environmental monitoring is to promote the early identification of, and response to, potential adverse environmental impacts associated with Lawrence Livermore National Laboratory (LLNL) operations. Environmental monitoring supports the Integrated Safety Management System (ISMS), International Organization for Standardization (ISO) 14001 Environmental Management Systems standard, and U. S. Department of Energy (DOE) Order 458.1, Radiation Protection of the Public and the Environment. Specifically, environmental monitoring enables LLNL to detect, characterize, and respond to releases from LLNL activities; assess impacts; estimate dispersal patterns in the environment; characterize the pathways of exposure to members of the public; characterize the exposures and doses to individuals and to the population; and to evaluate the potential impacts to the biota in the vicinity of LLNL. Environmental monitoring is also a major component of compliance demonstration for permits and other regulatory requirements. The Environmental Monitoring Plan (EMP) addresses the sample collection and analytical work supporting environmental monitoring to ensure the following: (1) A consistent system for collecting, assessing, and documenting environmental data of known and documented quality; (2) A validated and consistent approach for sampling and analysis of samples to ensure laboratory data meets program-specific needs and requirements within the framework of a performance-based approach …
Date: March 2, 2012
Creator: Gallegos, G M; Bertoldo, N A; Blake, R G; Campbell, C G; Grayson, A R; Nelson, J C et al.
System: The UNT Digital Library
EFFECTIVENESS OF COPPER AND BRONZE FOR ZINC CAPTURE (open access)

EFFECTIVENESS OF COPPER AND BRONZE FOR ZINC CAPTURE

A series of experiments was conducted to determine the efficacy of using copper and bronze sheet and screen under high vacuum conditions to capture zinc vapor. The experiments were conducted in a parametric manner using a fixed zinc vaporization temperature (350°C) but varying the filter temperature from ambient to 550°C. Consistent with previous work, metallic zinc was deposited at low temperatures, but the deposit was non‐adherent. At an intermediate temperature range (350‐450°C), the deposit formed an alloy with both copper and bronze materials. At higher temperatures (> 500°C) the zinc did not deposit on the surfaces likely due to its high vapor pressure. Additional testing to optimize the zinc 'getter' chemistry and surface condition is warranted.
Date: November 2, 2012
Creator: Korinko, P. S.
System: The UNT Digital Library
Performance Analysis: Issues Tracking System Data through September 2011 (open access)

Performance Analysis: Issues Tracking System Data through September 2011

None
Date: July 2, 2012
Creator: Kerr, C E; Holman, G & McTyer, N
System: The UNT Digital Library
STABLE SR VS 85SR SORPTION FROM SIMULATED WASTE SOLUTIONS BY MST AND MMST (open access)

STABLE SR VS 85SR SORPTION FROM SIMULATED WASTE SOLUTIONS BY MST AND MMST

A series of tests were performed to examine the sorption of stable Sr versus the sorption of {sup 85}Sr by monosodium titanate (MST) and modified monosodium titanate (mMST) from simulated waste solutions. Earlier testing indicated a discrepancy between the decontamination factors (DFs) obtained by measuring the stable Sr concentrations by inductively coupled plasma - mass spectroscopy (ICP-MS) and the {sup 85}Sr activities by gamma spectroscopy. One hypothesis to explain this discrepancy was that the stable Sr and {sup 85}Sr were in different chemical forms in the simulated solutions. Several simulants were prepared using different methods for adding the Sr and performance tests were carried out using MST and mMST to determine the Sr and {sup 85}Sr DFs with the various simulants. Testing indicated no discrepancy between the Sr and {sup 85}Sr DFs in tests with these simulants.
Date: April 2, 2012
Creator: Taylor-Pashow, K. & Hobbs, D.
System: The UNT Digital Library
A System for Conducting Sophisticated Mechanical Tests in Situ with High Energy Synchrotron X-Rays Final Technical Report (open access)

A System for Conducting Sophisticated Mechanical Tests in Situ with High Energy Synchrotron X-Rays Final Technical Report

This is the final technical report for the SBIR Phase I project titled 'A System for Conducting Sophisticated Mechanical Tests in Situ with High Energy Synchrotron X-Rays.' Experiments using diffraction of synchrotron radiation that help scientists understand engineering material failure modes, such as fracture and fatigue, require specialized machinery. This machinery must be able to induce these failure modes in a material specimen while adhering to strict size, weight, and geometric limitations prescribed by diffraction measurement techniques. During this Phase I project, Mechanical Solutions, Inc. (MSI) developed one such machine capable of applying uniaxial mechanical loading to a material specimen in both tension and compression, with zero backlash while transitioning between the two. Engineers currently compensate for a lack of understanding of fracture and fatigue by employing factors of safety in crucial system components. Thus, mechanical and structural parts are several times bigger, thicker, and heavier than they need to be. The scientific discoveries that result from diffraction experiments which utilize sophisticated mechanical loading devices will allow for broad material, weight, fuel, and cost savings in engineering design across all industries, while reducing the number of catastrophic failures in transportation, power generation, infrastructure, and all other engineering systems. With an …
Date: August 2, 2012
Creator: Weiss, Jeremy
System: The UNT Digital Library
DISSOLUTION OF PLUTONIUM METAL IN 8-10 M NITRIC ACID (open access)

DISSOLUTION OF PLUTONIUM METAL IN 8-10 M NITRIC ACID

The H-Canyon facility will be used to dissolve Pu metal for subsequent purification and conversion to plutonium dioxide (PuO{sub 2}) using Phase II of HB-Line. To support the new mission, the development of a Pu metal dissolution flowsheet which utilizes concentrated (8-10 M) nitric acid (HNO{sub 3}) solutions containing potassium fluoride (KF) is required. Dissolution of Pu metal in concentrated HNO{sub 3} is desired to eliminate the need to adjust the solution acidity prior to purification by anion exchange. The preferred flowsheet would use 8-10 M HNO{sub 3}, 0.015-0.07 M KF, and 0.5-1.0 g/L Gd to dissolve the Pu up to 6.75 g/L. An alternate flowsheet would use 8-10 M HNO{sub 3}, 0.05-0.2 M KF, and 1-2 g/L B to dissolve the Pu. The targeted average Pu metal dissolution rate is 20 mg/min-cm{sup 2}, which is sufficient to dissolve a “standard” 2250-g Pu metal button in 24 h. Plutonium metal dissolution rate measurements showed that if Gd is used as the nuclear poison, the optimum dissolution conditions occur in 10 M HNO{sub 3}, 0.04-0.05 M KF, and 0.5-1.0 g/L Gd at 112 to 116 °C (boiling). These conditions will result in an estimated Pu metal dissolution rate of ~11-15 mg/min-cm{sup …
Date: July 2, 2012
Creator: Rudisill, T. S. & Pierce, R. A.
System: The UNT Digital Library
VARIABILITY OF KD VALUES IN CEMENTITIOUS MATERIALS AND SEDIMENTS (open access)

VARIABILITY OF KD VALUES IN CEMENTITIOUS MATERIALS AND SEDIMENTS

Measured distribution coefficients (K{sub d} values) for environmental contaminants provide input data for performance assessments (PA) that evaluate physical and chemical phenomena for release of radionuclides from wasteforms, degradation of engineered components and subsequent transport of radionuclides through environmental media. Research efforts at SRNL to study the effects of formulation and curing variability on the physiochemical properties of the saltstone wasteform produced at the Saltstone Disposal Facility (SDF) are ongoing and provide information for the PA and Saltstone Operations. Furthermore, the range and distribution of plutonium K{sub d} values in soils is not known. Knowledge of these parameters is needed to provide guidance for stochastic modeling in the PA. Under the current SRS liquid waste processing system, supernate from F & H Tank Farm tanks is processed to remove actinides and fission products, resulting in a low-curie Decontaminated Salt Solution (DSS). At the Saltstone Production Facility (SPF), DSS is mixed with premix, comprised of blast furnace slag (BFS), Class F fly ash (FA), and portland cement (OPC) to form a grout mixture. The fresh grout is subsequently placed in SDF vaults where it cures through hydration reactions to produce saltstone, a hardened monolithic waste form. Variation in saltstone composition and …
Date: February 2, 2012
Creator: Almond, P.; Kaplan, D. & Shine, E.
System: The UNT Digital Library
Genome-Facilitated Analyses of Geomicrobial Processes (open access)

Genome-Facilitated Analyses of Geomicrobial Processes

This project had the goal(s) of understanding the mechanism(s) of extracellular electron transport (EET) in the microbe Shewanella oneidensis MR-1, and a number of other strains and species in the genus Shewanella. The major accomplishments included sequencing, annotation, and analysis of more than 20 Shewanella genomes. The comparative genomics enabled the beginning of a systems biology approach to this genus. Another major contribution involved the study of gene regulation, primarily in the model organism, MR-1. As part of this work, we took advantage of special facilities at the DOE: e.g., the synchrotron radiation facility at ANL, where we successfully used this system for elemental characterization of single cells in different metabolic states (1). We began work with purified enzymes, and identification of partially purified enzymes, leading to initial characterization of several of the 42 c-type cytochromes from MR-1 (2). As the genome became annotated, we began experiments on transcriptome analysis under different conditions of growth, the first step towards systems biology (3,4). Conductive appendages of Shewanella, called bacterial nanowires were identified and characterized during this work (5, 11, 20,21). For the first time, it was possible to measure the electron transfer rate between single cells and a solid substrate (20), …
Date: May 2, 2012
Creator: Nealson, Kenneth H.
System: The UNT Digital Library
Low Cost Open-Path Instrument for Monitoring Surface Carbon Dioxide at Sequestration Sites Phase I SBIR Final Report (open access)

Low Cost Open-Path Instrument for Monitoring Surface Carbon Dioxide at Sequestration Sites Phase I SBIR Final Report

Public confidence in safety is a prerequisite to the success of carbon dioxide (CO2) capture and storage for any program that intends to mitigate greenhouse gas emissions. In that regard, this project addresses the security of CO2 containment by undertaking development of what is called “an open path device” to measure CO2 concentrations near the ground above a CO2 storage area.
Date: October 2, 2012
Creator: Wu, Sheng
System: The UNT Digital Library
Renewal of Collaborative Research: Economically Viable Forest Harvesting Practices That Increase Carbon Sequestration (open access)

Renewal of Collaborative Research: Economically Viable Forest Harvesting Practices That Increase Carbon Sequestration

Forests provide wildlife habitat, water and air purification, climate moderation, and timber and nontimber products. Concern about climate change has put forests in the limelight as sinks of atmospheric carbon. The C stored in the global vegetation, mostly in forests, is nearly equivalent to the amount present in atmospheric CO{sub 2}. Both voluntary and government-mandated carbon trading markets are being developed and debated, some of which include C sequestration resulting from forest management as a possible tradeable commodity. However, uncertainties regarding sources of variation in sequestration rates, validation, and leakage remain significant challenges for devising strategies to include forest management in C markets. Hence, the need for scientifically-based information on C sequestration by forest management has never been greater. The consequences of forest management on the US carbon budget are large, because about two-thirds of the {approx}300 million hectare US forest resource is classified as 'commercial forest.' In most C accounting budgets, forest harvesting is usually considered to cause a net release of C from the terrestrial biosphere to the atmosphere. However, forest management practices could be designed to meet the multiple goals of providing wood and paper products, creating economic returns from natural resources, while sequestering C from the …
Date: August 2, 2012
Creator: Davidson, E. A.; Dail, D. B.; Hollinger, D.; Scott, N. & Richardson, A.
System: The UNT Digital Library
Development Status of PROTEUS-MOC (open access)

Development Status of PROTEUS-MOC

None
Date: November 2, 2012
Creator: Marin-Lafleche, A.; Smith, M. A.; Lewis, E. E. & Lee, C. H. (Nuclear Engineering Division)
System: The UNT Digital Library
Adaptive Algebraic Multigrid for Finite Element Elliptic Equations with Random Coefficients (open access)

Adaptive Algebraic Multigrid for Finite Element Elliptic Equations with Random Coefficients

This thesis presents a two-grid algorithm based on Smoothed Aggregation Spectral Element Agglomeration Algebraic Multigrid (SA-{rho}AMGe) combined with adaptation. The aim is to build an efficient solver for the linear systems arising from discretization of second-order elliptic partial differential equations (PDEs) with stochastic coefficients. Examples include PDEs that model subsurface flow with random permeability field. During a Markov Chain Monte Carlo (MCMC) simulation process, that draws PDE coefficient samples from a certain distribution, the PDE coefficients change, hence the resulting linear systems to be solved change. At every such step the system (discretized PDE) needs to be solved and the computed solution used to evaluate some functional(s) of interest that then determine if the coefficient sample is acceptable or not. The MCMC process is hence computationally intensive and requires the solvers used to be efficient and fast. This fact that at every step of MCMC the resulting linear system changes, makes an already existing solver built for the old problem perhaps not as efficient for the problem corresponding to the new sampled coefficient. This motivates the main goal of our study, namely, to adapt an already existing solver to handle the problem (with changed coefficient) with the objective to achieve …
Date: April 2, 2012
Creator: Kalchev, D
System: The UNT Digital Library
Fusion-Fission Hybrid for Fissile Fuel Production without Processing (open access)

Fusion-Fission Hybrid for Fissile Fuel Production without Processing

Two scenarios are typically envisioned for thorium fuel cycles: 'open' cycles based on irradiation of {sup 232}Th and fission of {sup 233}U in situ without reprocessing or 'closed' cycles based on irradiation of {sup 232}Th followed by reprocessing, and recycling of {sup 233}U either in situ or in critical fission reactors. This study evaluates a third option based on the possibility of breeding fissile material in a fusion-fission hybrid reactor and burning the same fuel in a critical reactor without any reprocessing or reconditioning. This fuel cycle requires the hybrid and the critical reactor to use the same fuel form. TRISO particles embedded in carbon pebbles were selected as the preferred form of fuel and an inertial laser fusion system featuring a subcritical blanket was combined with critical pebble bed reactors, either gas-cooled or liquid-salt-cooled. The hybrid reactor was modeled based on the earlier, hybrid version of the LLNL Laser Inertial Fusion Energy (LIFE1) system, whereas the critical reactors were modeled according to the Pebble Bed Modular Reactor (PBMR) and the Pebble Bed Advanced High Temperature Reactor (PB-AHTR) design. An extensive neutronic analysis was carried out for both the hybrid and the fission reactors in order to track the fuel …
Date: January 2, 2012
Creator: Fratoni, M.; Moir, R. W.; Kramer, K. J.; Latkowski, J. F.; Meier, W. R. & Powers, J. J.
System: The UNT Digital Library