LLW Notes, Volume 10, Number 3, April/May 1995 (open access)

LLW Notes, Volume 10, Number 3, April/May 1995

Newsletter distributed to the Low-Level Radioactive Waste Forum members describing current news, policies, and legislation, as well as other information relevant to the management of low-level radioactive waste.
Date: May 5, 1995
Creator: Afton Associates, Inc.
Object Type: Journal/Magazine/Newsletter
System: The UNT Digital Library
Predicting tropospheric ozone and hydroxyl radical in a global, three-dimensional, chemistry, transport, and deposition model (open access)

Predicting tropospheric ozone and hydroxyl radical in a global, three-dimensional, chemistry, transport, and deposition model

Two of the most important chemically reactive tropospheric gases are ozone (O{sub 3}) and the hydroxyl radical (OH). Although ozone in the stratosphere is a necessary protector against the sun`s radiation, tropospheric ozone is actually a pollutant which damages materials and vegetation, acts as a respiratory irritant, and is a greenhouse gas. One of the two main sources of ozone in the troposphere is photochemical production. The photochemistry is initiated when hydrocarbons and carbon monoxide (CO) react with nitrogen oxides (NO{sub x} = NO + NO{sub 2}) in the presence of sunlight. Reaction with the hydroxyl radical, OH, is the main sink for many tropospheric gases. The hydroxyl radical is highly reactive and has a lifetime on the order of seconds. Its formation is initiated by the photolysis of tropospheric ozone. Tropospheric chemistry involves a complex, non-linear set of chemical reactions between atmospheric species that vary substantially in time and space. To model these and other species on a global scale requires the use of a global, three-dimensional chemistry, transport, and deposition (CTD) model. In this work, I developed two such three dimensional CTD models. The first model incorporated the chemistry necessary to model tropospheric ozone production from the reactions …
Date: January 5, 1995
Creator: Atherton, C.S.
Object Type: Report
System: The UNT Digital Library
A quantum mechanical equivalent photon spectrum for heavy ion reactions (open access)

A quantum mechanical equivalent photon spectrum for heavy ion reactions

Radioactive nuclear beams are rapidly coming to the fore as an important alternative to traditional measurements in nuclear astrophysics. Radioactive nuclei are scattered off the strong electromagnetic fields of a heavy ion, such as lead, providing an independent measurement of electromagnetic cross sections that are difficult to measure otherwise. In this paper, we examine the corrections to the semi-classical ``equivalent photon spectrum`` used to analyze these experiments, and derive an improved spectrum, valid in the long wavelength limit, that includes the effects of the size of the heavy ion, the non-zero longitudinal momentum transfer required by kinematics, and the response of the target nucleus to be off-shell photon.
Date: December 5, 1995
Creator: Benesh, C.J.; Hayes, A.C. & Friar, J.L.
Object Type: Article
System: The UNT Digital Library
Closed-form approach to checking frame design (open access)

Closed-form approach to checking frame design

This brief report contains calculations of deflections and stresses of the support frame on the XMM project. The goal is to provide an independent view of structural integrity of the frame utilizing a noncomputer approach to design based on elementary closed form solutions and approximate models of mechanical and structural behavior. It is recognized that full confidence can only be assured when computer generated results pertaining to the critical areas and features of the integrating structure can be enveloped by the bracketing solutions. Although the computer solutions have come from the three independent sources, this report utilizes the numerical values from the LLNL studies represented by the computer runs and analysis of the critical elements of the frame. Since the frame geometry, deformation patterns, and the nature of loading are highly complex, this study is restricted to simplified models of selected areas of the structure which can be handled by the conventional formulas and reasonable approximations. This report contains some comments related to material properties, stress concentration, and elements of fracture mechanics directly applicable to frame analysis and design. Such topics and parameters fall usually outside the finite element modeling, but they can have a crucial influence on the mechanical …
Date: April 5, 1995
Creator: Blake, A.
Object Type: Report
System: The UNT Digital Library
Headspace gas and vapor characterization summary for the 43 vapor program suspect tanks (open access)

Headspace gas and vapor characterization summary for the 43 vapor program suspect tanks

During the time period between February 1994 and September 1995, Westinghouse Hanford Company (WHC) sampled the waste tank headspace of 43 single-shell tanks for a variety of gaseous and/or volatile and semi-volatile compounds. This report summarizes the results of analyses of those sampling activities with respect to both the Priority 1 Safety Issues and relative to the detection in the headspace of significant concentrations of target analytes relating to worker breathing space considerations as recommended by the Pacific Northwest Laboratory (PNL) Toxicology Review Panel. The information contained in the data tables was abstracted from the vapor sampling and analysis tank characterization reports. Selected results are tabulated and summarized. Sampling equipment and methods, as well as sample analyses, are briefly described. Vapor sampling of passively ventilated single-shell tanks (tanks C-105, C-106, and SX-106 were sampled and are actively ventilated) has served to highlight or confirm tank headspace conditions associated with both priority 1 safety issues and supports source term analysis associated with protecting worker health and safety from noxious vapors.
Date: October 5, 1995
Creator: Bratzel, D.R.
Object Type: Report
System: The UNT Digital Library
Acceptance/operational test procedure 103-AN tank camera purge system and 103-AN video camera system (open access)

Acceptance/operational test procedure 103-AN tank camera purge system and 103-AN video camera system

This Acceptance/Operational Test Procedure will document the satisfactory operation of the 103-AN Camera Purge Control System and 103-AN Video Camera System
Date: September 5, 1995
Creator: Castleberry, J.L.
Object Type: Report
System: The UNT Digital Library
Application of geometry correction factors for low-level waste package dose measurements. Revision 1 (open access)

Application of geometry correction factors for low-level waste package dose measurements. Revision 1

Plans are to determine the Cs-137 content of low-level waste packages generated in High-Level Waste by measuring the radiation level at a specified distance from the package with a hand-held radiation instrument. The measurement taken at this specified distance, either 3 or 5 feet, is called the far-field measurement. This report documents a method for adjusting the gamma exposure rate (mR/hr) reading used in dose-to-curie determinations when the far-field measurement equals the background reading. This adjustment is necessary to reduce the conservatism resulting from using a minimum detection limit exposure rate for the dose-to-curie determination for the far-field measurement position. To accomplish this adjustment, the near-field (5 cm) measurement is multiplied by a geometry correction factor to obtain an estimate of the far field exposure rate (which is below instrument sensitivity). This estimate of the far field exposure rate is used to estimate the Cs-137 curie content of the package. This report establishes the geometry correction factors for the dose-to-curie determination when the far-field gamma exposure measurement equals the background reading. This report also provides a means of demonstrating compliance to 1S Manual requirements for exposure rate readings at different locations from waste packages while specifying only two measurement positions. …
Date: January 5, 1995
Creator: Chandler, M.C. & Parish, B.
Object Type: Report
System: The UNT Digital Library
A distributed activation energy model of heterogeneous coal ignition. Technical progress report, April 1-- June 30, 1995 (open access)

A distributed activation energy model of heterogeneous coal ignition. Technical progress report, April 1-- June 30, 1995

Experiments designed to measure kinetic rate constants of ignition of pulverized coals showed clearly that, for single particles or dilute suspensions, particle-to-particle variations due to reactivity and/or thermophysical properties are important. There exists ample evidence that the most important factor in interpreting these data is the existence of a variation in chemical reactivity in the sample. It is surprising, therefore, to note that all previous studies presumed that a single (average) activation energy is adequate to describe the ignition process. The equations formulated using this presumption are then correlated to the experimental measurements to infer the kinetic rate constants of ignition. The major objectives are to develop a model of heterogeneous ignition which allows for a distribution of activation energies, and to implement this model to interpret previously published data. It is the authors hypothesis that variations in chemical reactivity account for the experimental trends observed. Another objective of this project is to examine the effects of variations in thermodynamic and physical properties (e.g. specific heat, particle diameter, density) on data interpretation from previous ignition experiments. An attached paper submitted for review to ``Combustion and Flame`` summarizes the Distributed Activation Energy Model of Ignition, which accounts for particle-to-particle variations in …
Date: July 5, 1995
Creator: Chen, J. C.
Object Type: Report
System: The UNT Digital Library
Role of char during reburning of nitrogen oxides. Eighth quarterly report, July 1, 1995--September 30, 1995 (open access)

Role of char during reburning of nitrogen oxides. Eighth quarterly report, July 1, 1995--September 30, 1995

The investigation of this quarter focuses on the rates of NO reactions with chars in various gaseous environments. The results have revealed significant insights into the NO reduction mechanisms on char surface, particularly when the oxidants, O{sub 2} and CO{sub 2}, are introduced into the feed. Indeed, evidences suggest that the formation of stable oxygen complexes is the major cause of differences in NO reactivity on chars of different origins. The oxidants retard the reactivity of char derived fro the bituminous coal more seriously than they affect the char derived from lignite. Furthermore, additions of these oxidants into the reacting stream produce additional yields of CO and CO{sub 2} during NO reaction with lignite char, suggesting gasification of carbon from lignite char. No excess CO and CO{sub 2} were observed when the bituminous coal char was used. These yields of CO and CO{sub 2} also imply that desorption of stable surface oxygen complex is a rate-limiting step which may be catalyzed by the mineral matters during reactions involving lignite char. Surface area evaluated by CO{sub 2} and Dubinin-Radushkevich (D-R) equation is not a normalization factor of char reactivity during reburning. In the absence of oxidants, the bituminous coal char shows …
Date: November 5, 1995
Creator: Chen, Wei-Yin; Lu, Te-Chang; Fan, L.T. & Yashima, Mutsuo
Object Type: Report
System: The UNT Digital Library
Solid Waste Information Tracking System (SWITS), Backlog Waste Modifications, Software Requirements Specification (SRS) (open access)

Solid Waste Information Tracking System (SWITS), Backlog Waste Modifications, Software Requirements Specification (SRS)

Purpose of this document is to define the system requirements necessary to improve computer support for the WHC backlog waste business process through enhancements to the backlog waste function of the SWITS system. This SRS document covers enhancements to the SWITS system to support changes to the existing Backlog Waste screens including new data elements, label changes, and new pop-up screens. The pop-ups will allow the user to flag the processes that a waste container must have performed on it, and will provide history tracking of changes to data. A new screen will also be provided allowing Acceptable Services to perform mass updates to specific data in Backlog Waste table. The SWITS Backlog Waste enhancements in this document will support the project goals in WHC-SD-WM-003 and its Revision 1 (Radioactive Solid Waste Tracking System Conceptual Definition) for the control, tracing, and inventory management of waste as the packages are generated and moved through final disposal (cradle-to-grave).
Date: May 5, 1995
Creator: Clark, R. E.
Object Type: Report
System: The UNT Digital Library
Design analysis supporting 101-SY Water Decon System (open access)

Design analysis supporting 101-SY Water Decon System

This document contains the results of stress analysis and component sizing for the 101-SY mitigation pump, Water Decon System. Calculations included are a stress analysis of the High Pressure Manifold, the threaded connection on the Yoke Water Connector and a sizing of an air receiver tank.
Date: September 5, 1995
Creator: Cleveland, K.J.
Object Type: Report
System: The UNT Digital Library
Identification of potential transuranic waste tanks at the Hanford Site (open access)

Identification of potential transuranic waste tanks at the Hanford Site

The purpose of this document is to identify potential transuranic (TRU) material among the Hanford Site tank wastes for possible disposal at the Waste Isolation Pilot Plant (WIPP) as an alternative to disposal in the high-level waste (HLW) repository. Identification of such material is the initial task in a trade study suggested in WHC-EP-0786, Tank Waste Remediation System Decisions and Risk Assessment (Johnson 1994). The scope of this document is limited to the identification of those tanks that might be segregated from the HLW for disposal as TRU, and the bases for that selection. It is assumed that the tank waste will be washed to remove soluble inert material for disposal as low-level waste (LLW), and the washed residual solids will be vitrified for disposal. The actual recommendation of a disposal strategy for these materials will require a detailed cost/benefit analysis and is beyond the scope of this document.
Date: May 5, 1995
Creator: Colburn, R. P.
Object Type: Report
System: The UNT Digital Library
Vault safety and inventory system conceptual baseline document (open access)

Vault safety and inventory system conceptual baseline document

This document defines the baseline scope, schedule, and cost of the replacement computer system for the Vault Safety and Inventory System at the Plutonium Finishing Plant.
Date: September 5, 1995
Creator: Corrigan, N. B.
Object Type: Report
System: The UNT Digital Library
Development test procedure High Pressure Water Jet System (open access)

Development test procedure High Pressure Water Jet System

Development testing will be performed on the water jet cleaning fixture to determine the most effective arrangement of water jet nozzles to remove contamination from the surfaces of canisters and other debris. The following debris may be stained with dye to simulate surface contaminates: Mark O, Mark I, and Mark II Fuel Storage Canisters (both stainless steel and aluminum), pipe of various size, (steel, stainless, carbon steel and aluminum). Carbon steel and stainless steel plate, channel, angle, I-beam and other surfaces, specifically based on the Scientific Ecology Group (SEG) inventory and observations of debris within the basin. Test procedure for developmental testing of High Pressure Water Jet System.
Date: June 5, 1995
Creator: Crystal, J.B.
Object Type: Report
System: The UNT Digital Library
Investigation of liquid instrusion in 241-BX-103 (open access)

Investigation of liquid instrusion in 241-BX-103

Although SST 241-BX-103 is classified as being interim stabilized and intrusion prevented, FIC readings have indicated the tank`s surface level to be increasing in a `step like` fashion even after the completion of intrusion prevention activities. This letter report discusses the finding of an investigation conducted to (i) determine if liquid intrusion (rather than other potential causes such as a change in the waste`s physiochemical properties, instrumentation error, etc.) was responsible for the increase in the surface level and if so, (ii) recommend a likely course of action to pursue if the tank`s supernate volume is exceeding the interim stabilization criterion. Engineering judgement (supplemented by analysis of historical tank data, tank video and photographs) was used to determine the extent to which the rise in the surface level could be attributed to various types of liquid intrusion and/or other phenomena. It was concluded that the rise in BX-103`s surface level was indeed real (and most likely caused by liquid intrusion), and that the tank`s supernate volume was exceeding the interim stabilization criterion of 5000 gallons. However the tank`s surface level has remained fairly constant since August 1993. It was recommended that tank BX-103 be left `as is` for the moment …
Date: October 5, 1995
Creator: Dasgupta, A.
Object Type: Report
System: The UNT Digital Library
Using emissivity-corrected thermal maps to locate deep structural defects in concrete bridge decks (open access)

Using emissivity-corrected thermal maps to locate deep structural defects in concrete bridge decks

Dual-band infrared (DBIR) thermal imaging is a promising, non-contact, nondestructive evaluation tool to evaluate the amount of deteriorated concrete on asphalt-covered bridge decks. We conducted proof-of-principle demonstrations to characterize defects in concrete structures which could be detected with DBIR thermal imaging. We constructed two identical concrete slabs with synthetic delaminations, e.g., 1/8-in. thick styrofoam squares, implanted just above the 2-in.-deep steel reinforcement bars. We covered one of the slabs with a 2-in. layer of asphalt. We mounted the DBIR cameras on a tower platform, to simulate the optics needed to conduct bridge-deck inspections from a moving vehicle. We detected 4-in. implants embedded in concrete and 9-in. implants embedded in asphalt-covered concrete. The midday (above-ambient) and predawn (below-ambient) delamination-site temperatures correlated with the implant sizes. Using DBIR image ratios, we enhanced thermal-contrast and removed emissivity-noise, e.g., from concrete compositional variations and clutter. Using the LLNL/VIEW code, we removed the asphalt thermal-gradient mask, to depict the 4-in. deep, 9-in. square, concrete implant size. We plan to image bridge deck defects, from a moving vehicle, for accurate estimations of the amount of deteriorated concrete impairing the deck integrity. Potential longterm benefits are affordable and reliable rehabilitation for asphalt-covered decks.
Date: April 5, 1995
Creator: Del Grande, N. K. & Durbin, P. F.
Object Type: Article
System: The UNT Digital Library
The effects of selenium on glutathione peroxidase activity and radioprotection in mammalian cells (open access)

The effects of selenium on glutathione peroxidase activity and radioprotection in mammalian cells

The media of representative mammalian cell lines were supplemented with low levels of selenium in the form of sodium selenite in order to investigate the effects of selenium on mammalian cells. Following incubation in 30 nM sodium selenite, these cells were assayed for changes in glutathione peroxidase (GPx) activity. The cells examined included NIH 3T3 mouse fibroblasts, PC12 rat sympathetic precursor cells, SupT-1 human lymphocytes, MCF-7{sup adr} human breast carcinoma cells and AA8 Chinese hamster ovary cells. Selenium supplementation resulted in a marginal increase in GPx activity for the NIH 3T3, MCF-7{sup adr} and Supt-1 cells but stimulated GPx activity approximately 5-fold in PC12 and AA8 cells. AA8 cells were selected to evaluate whether selenium supplementation was radioprotective against {sup 60}cobalt gamma irradiation. Protection against radiation-induced mutation was measured by evaluating mutation frequency at the hprt locus. In this assay, preincubation of AA8 CHO cells significantly protected these cells from exposure to 8 Gy.
Date: September 5, 1995
Creator: Diamond, A. M.; Murray, J. L.; Dale, P.; Tritz, R. & Grdina, D. J.
Object Type: Report
System: The UNT Digital Library
A human factors engineering evaluation of the Multi-Function Waste Tank Facility. Final report (open access)

A human factors engineering evaluation of the Multi-Function Waste Tank Facility. Final report

This report documents the methods and results of a human factors engineering (HFE) review conducted on the Multi-Function Waste Tank Facility (MWTF), Westinghouse Hanford Company (WHC) Project 236A, to be constructed at the U.S. Department of Energy (DOE) facility at Hanford, Washington. This HFE analysis of the MWTF was initiated by WHC to assess how well the current facility and equipment design satisfies the needs of its operations and maintenance staff and other potential occupants, and to identify areas of the design that could benefit from improving the human interfaces at the facility. Safe and effective operations, including maintenance, is a primary goal for the MWTF. Realization of this goal requires that the MWTF facility, equipment, and operations be designed in a manner that is consistent with the abilities and limitations of its operating personnel. As a consequence, HFE principles should be applied to the MWTF design, construction, its operating procedures, and its training. The HFE review was focused on the 200-West Area facility as the design is further along than that of the 200-East Area. The review captured, to the greatest extent feasible at this stage of design, all aspects of the facility activities and included the major topics …
Date: June 5, 1995
Creator: Donohoo, D.T. & Sarver, T.L.
Object Type: Report
System: The UNT Digital Library
Lessons from UNSCOM/IAEA applicable to nuclear arms control (open access)

Lessons from UNSCOM/IAEA applicable to nuclear arms control

In early 1991, the Security Council of the United Nations tasked the Director General of the International Atomic Energy Agency, with the assistance and cooperation of the United Nations Special Commission, to oversee the destruction, removal or rendering harmless of nuclear weapons material and capabilities in Iraq. The conduct of the nuclear inspections, and the subsequent activities (identification, destruction, removal rendering harmless), have provided a wealth of experience and insight into the inspection and monitoring process as well as into the political realities of such an operation. The early inspections were conducted in an atmosphere of discovery and inexperience on both the part of the Iraqis and the IAEA and UNSCOM. As time went on, the Iraqis became more adept at hiding and obscuring relevant documents and equipment, and the inspection teams became more knowledgeable about inspection and investigative techniques, and the pre-existing Iraqi programs. A continuous monitoring presence in Iraq has now been established and an import/export monitoring regime is being developed. While steps taken to date have proven effective in inhibiting resumption of nuclear weaponization activities, it remains to be seen how effective these measures will be in the future. The external and internal conditions which led the …
Date: December 5, 1995
Creator: Dorn, D.W.
Object Type: Article
System: The UNT Digital Library
Estimation of total error in DWPF reported radionuclide inventories. Revision 1 (open access)

Estimation of total error in DWPF reported radionuclide inventories. Revision 1

The Defense Waste Processing Facility (DWPF) at the Savannah River Site is required to determine and report the radionuclide inventory of its glass product. For each macro-batch, the DWPF will report both the total amount (in curies) of each reportable radionuclide and the average concentration (in curies/gram of glass) of each reportable radionuclide. The DWPF is to provide the estimated error of these reported values of its radionuclide inventory as well. The objective of this document is to provide a framework for determining the estimated error in DWPF`s reporting of these radionuclide inventories. This report investigates the impact of random errors due to measurement and sampling on the total amount of each reportable radionuclide in a given macro-batch. In addition, the impact of these measurement and sampling errors and process variation are evaluated to determine the uncertainty in the reported average concentrations of radionuclides in DWPF`s filled canister inventory resulting from each macro-batch.
Date: June 5, 1995
Creator: Edwards, T. B.
Object Type: Report
System: The UNT Digital Library
Operator coil monitoring acceptance test procedure (open access)

Operator coil monitoring acceptance test procedure

The readiness of the Data Acquisition and Control System (DACS) to provide monitoring and control of the Programmable Logic Controller (PLC) abort coils from the Master and RSS stations will be systematically tested during performance of this procedure. It should be noted that these are not physical abort coils but software coils controlled by the software`s ladder logic. The readiness of the DACS to properly interface with the ENRAF wire level gauge installed in the SY101 storage tank will also be tested. During this test, a verification of all abort coil indications will be conducted at the DACS Development Facility in the 306E Building by injecting an input signal for each DACS sensor that has an associated abort coil until the abort coil actuates, and then ensuring that the status of the abort coil indicated at the Master and RSS stations correct. Each abort coil will also be tested to ensure that the ``ENABLE`` and ``DISABLE`` controls from the Master and RSS stations function correctly, and only with the use of proper passwords.
Date: June 5, 1995
Creator: Erhart, M.F.
Object Type: Report
System: The UNT Digital Library
Quality assurance procedures for the analysis of TRU waste samples (open access)

Quality assurance procedures for the analysis of TRU waste samples

The Waste Isolation Pilot Plant (WIPP) project was undertaken in response to the growing need for a national repository for transuranic (TRU) waste. Guidelines for WIPP specify that any waste item to be interred must be fully characterized and analyzed to determine the presence of chemical compounds designated hazardous and certain toxic elements. The Transuranic Waste Characterization Program (TWCP) was launched to develop analysis and quality guidelines, certify laboratories, and to oversee the actual waste characterizations at the laboratories. ORNL is participating in the waste characterization phase and brings to bear a variety of analytical techniques including ICP-AES, cold vapor atomic absorption, and instrumental neutron activation analysis (INAA) to collective determine arsenic, cadmium, barium, chromium, mercury, selenium, silver, and other elements. All of the analytical techniques involved participate in a cooperative effort to meet the project objectives. One important component of any good quality assurance program is determining when an alternate method is more suitable for a given analytical problem. By bringing to bear a whole arsenal of analytical techniques working toward common objectives, few analytical problems prove to be insurmountable. INAA and ICP-AES form a powerful pair when functioning in this cooperative manner. This paper will provide details of …
Date: October 5, 1995
Creator: Glasgow, D.C. Giaquinto, J.M. & Robinson, L.
Object Type: Article
System: The UNT Digital Library
Status report on preliminary assessment of variations of regional phases and discriminants with distance (open access)

Status report on preliminary assessment of variations of regional phases and discriminants with distance

An improved understanding of the variability of regional seismic phases with distance is needed to improve the performance and transportability of regional seismic discriminants. Observations of large variations in regional phase amplitudes, over relatively short distances, are not uncommon. For example, large variations in Pn amplitudes of the Non-Proliferation Experiment (NPE) were observed along lines to the west (e.g., Keller et al., 1994), and northwest (e.g., McCormack et al., 1994). Numerous studies, in a number of areas, have also observed large variations in Sn and Lg over relatively short distances (e.g., Kadinsky-Cade et al., 1981; Ni and Barazangi, 1983). An improved understanding of these variations has been gained from numerous empirical observations (e.g., Chavez and Priestley, 1984; Zhang et al., 1994) and theoretical studies (e.g., Campillo, 1990, Kennett, 1993). We are developing a number of techniques and procedures for characterizing such features on a region specific basis.
Date: June 5, 1995
Creator: Goldstein, P. & Schultz, C.
Object Type: Report
System: The UNT Digital Library
Slag recycling of irradiated vanadium (open access)

Slag recycling of irradiated vanadium

An experimental inductoslag apparatus to recycle irradiated vanadium was fabricated and tested. An experimental electroslag apparatus was also used to test possible slags. The testing was carried out with slag materials that were fabricated along with impurity bearing vanadium samples. Results obtained include computer simulated thermochemical calculations and experimentally determined removal efficiencies of the transmutation impurities. Analyses of the samples before and after testing were carried out to determine if the slag did indeed remove the transmutation impurities from the irradiated vanadium.
Date: April 5, 1995
Creator: Gorman, P.K.
Object Type: Thesis or Dissertation
System: The UNT Digital Library