A METHODOLOGY FOR DETERMINING THE DOSE RATE FOR BOUNDING MASS LIMITS IN A 9977 PACKAGING (open access)

A METHODOLOGY FOR DETERMINING THE DOSE RATE FOR BOUNDING MASS LIMITS IN A 9977 PACKAGING

The Small Gram Quantity (SGQ) concept is based on the understanding that the hazards associated with the shipment of a radioactive material are directly proportional to its mass. This study describes a methodology that estimates the acceptable masses for several neutron and gamma emitting isotopes that can be shipped in a 9977 Package compliant with the Title 10 of the Code of Federal Regulations, Part 71 (10CFR71) external radiation level limits. 10CFR71.33 states that a shipping application identifies the radioactive and fissile materials at their maximum quantity and provides an evaluation demonstrating compliance with the external radiation standards. Since rather small amounts of some isotopes emit sufficiently strong radiation to produce a large external dose rate, quantifying of the dose rate for a proposed content is a challenging issue for the SGQ approach. It is essential to quantify external radiation levels from several common gamma and neutron sources that can be safely placed in a specific packaging, to ensure compliance with federal regulations. A methodology was established for determining the dose rate for bounding mass limits for a set of isotopes in the Model 9977 Shipping Package. Calculations were performed to estimate external radiation levels using the MCNP radiation transport …
Date: May 24, 2012
Creator: Abramczyk, G.; Bellamy, S.; Nathan, S. & Loftin, B.
System: The UNT Digital Library
Developing high brightness and high current beams for HIF injectors (open access)

Developing high brightness and high current beams for HIF injectors

The US Heavy Ion Fusion Virtual National Laboratory is continuing research into ion sources and injectors that simultaneously provide high current (0.5-1.0 Amps) and high brightness (normalized emittance better than 1.0 {pi}-mm-mr). The central issue of focus is whether to continue pursuing the traditional approach of large surface ionization sources or to adopt a multiaperture approach that transports many smaller ''beamlets'' separately at low energies before allowing them to merge. For the large surface source concept, the recent commissioning of the 2-MeV injector for the High Current eXperiment has increased our understanding of the beam quality limitations for these sources. We have also improved our techniques for fabricating large diameter aluminosilicate sources to improve lifetime and emission uniformity. For the multiaperture approach, we are continuing to study the feasibility of small surface sources and a RF induced plasma source in preparation for beamlet merging experiments, while continuing to run computer simulations for better understanding of this alternate concept. Experiments into both architectures will be performed on a newly commissioned ion source test stand at LLNL called STS-500. This stand test provides a platform for testing a variety of ion sources and accelerating structures with 500 kV, 17-microsecond pulses. Recent progress …
Date: May 24, 2002
Creator: Ahle, Larry; Grote, Dave & Kwan, Joe
System: The UNT Digital Library
Magnetic Semiconductor Quantum Wells in High Fields to 60 Tesla: Photoluminescence Linewidth Annealing at Magnetization Steps (open access)

Magnetic Semiconductor Quantum Wells in High Fields to 60 Tesla: Photoluminescence Linewidth Annealing at Magnetization Steps

Magnetic semiconductors offer a unique possibility for strongly tuning the intrinsic alloy disorder potential with applied magnetic field. We report the direct observation of a series of step-like reductions in the magnetic alloy disorder potential in single ZnSe/Zn(Cd,Mn)Se quantum wells between O and 60 Tesla. This disorder, measured through the linewidth of low temperature photoluminescence spectra drops abruptly at -19, 36, and 53 Tesla, in concert with observed magnetization steps. Conventional models of alloy disorder (developed for nonmagnetic semiconductors) reproduce the general shape of the data, but markedly underestimate the size of the linewidth reduction.
Date: May 24, 1999
Creator: Awschalom, D.D.; Crooker, S.A.; Lyo, S.K.; Rickel, D.G. & Samarth, N.
System: The UNT Digital Library
Thermo-Chemical-Mechanical Effects on Microstructure Development in Low-Alloy Steel Welds (open access)

Thermo-Chemical-Mechanical Effects on Microstructure Development in Low-Alloy Steel Welds

Effect of aluminum on the decomposition of 5 ferrite to austenite was investigated in a low-alloy steel weld. In addition, the effect of inclusion composition on the transition from bainite to acicular ferrite during austenite decomposition was analyzed. Stress relaxation during decomposition of austenite to allotriomorphic and acicular ferrite was also characterized. Results from the above experiments illustrate the importance of thermomechanical effects on weld microstructure evolution.
Date: May 24, 1999
Creator: Babu, S.S.; David, S.A. & Vitek, J.M.
System: The UNT Digital Library
A Comparative experimental study of media access protocols for wireless radio networks (open access)

A Comparative experimental study of media access protocols for wireless radio networks

We conduct a comparative experimental analysis of three well known media access protocols: 802.11, CSMA, and MACA for wireless radio networks. Both fixed and ad-hoc networks are considered. The experimental analysis was carried out using GloMoSim: a tool for simulating wireless networks. The main focus of experiments was to study how (i) the size of the network, (ii) number of open connections, (iii) the spatial location of individual connections, (iv) speed with which individual nodes move and (v) protocols higher up in the protocol stack (e,g. routing layer) affect the performance of the media access sublayer protocols. The performance of the protocols was measured w.r.t. three important parameters: (1) number of received packets, (2) average latency of each packet, and (3) throughput. The following general qualitative conclusions were obtained; some of the conclusions reinforce the earlier claims by other researchers. (1) Although 802.11 performs better than the other two protocols with respect to fairness of transmission, packets dropped, and latency, its performance is found to (i) show a lot of variance with changing input parameters and (ii) the overall performance still leaves a lot of room for improvement. (2) CSMA does not perform too well under the fairness criteria, however, …
Date: May 24, 2001
Creator: Barrett, C. L. (Christopher L.); Drozda, M. (Martin) & Marathe, M. V. (Madhav V.)
System: The UNT Digital Library
A Pulse Power Modulator System for Commercial High Power Ion Beam Surface Treatment Applications (open access)

A Pulse Power Modulator System for Commercial High Power Ion Beam Surface Treatment Applications

The Ion Beam Surface Treatment (lBESTrM) process utilizes high energy pulsed ion beams to deposit energy onto the surface of a material allowing near instantaneous melting of the surface layer. The melted layer typically re-solidifies at a very rapid rate which forms a homogeneous, fine- grained structure on the surface of the material resulting in significantly improved surface characteristics. In order to commercialize the IBESTTM process, a reliable and easy-to-operate modulator system has been developed. The QM-I modulator is a thyratron-switched five-stage magnetic pulse compression network which drives a two-stage linear induction adder. The adder provides 400 kV, 150 ns FWHM pulses at a maximum repetition rate of 10 pps for the acceleration of the ion beam. Special emphasis has been placed upon developing the modulator system to be consistent with long-life commercial service.
Date: May 24, 1999
Creator: Barrett, D. M.; Cockreham, B.D.; Dragt, A. J.; Ives, H. C.; Neau, E. L.; Reed, K. W. et al.
System: The UNT Digital Library
Nanoporous plasmonic metamaterials (open access)

Nanoporous plasmonic metamaterials

We review different routes for the generation of nanoporous metallic foams and films exhibiting well-defined pore size and short-range order. Dealloying and templating allows the generation of both two- and three-dimensional structures which promise a well defined plasmonic response determined by material constituents and porosity. Viewed in the context of metamaterials, the ease of fabrication of samples covering macroscopic dimensions is highly promising, and suggests more in-depth investigations of the plasmonic and photonic properties of this material system for photonic applications.
Date: May 24, 2007
Creator: Biener, J.; Nyce, G. W.; Hodge, A. M.; Biener, M. M.; Hamza, A. V. & Maier, S A
System: The UNT Digital Library
Plutonium Disposition Now! (open access)

Plutonium Disposition Now!

A means for use of existing processing facilities and reactors for plutonium disposition is described which requires a minimum capital investment and allows rapid implementation. The scenario includes interim storage and processing under IAEA control, and fabrication into MOX fuel in existing or planned facilities in Europe for use in operating reactors in the two home countries. Conceptual studies indicate that existing Westinghouse four-loop designs can safety dispose of 0.94 MT of plutonium per calendar year. Thus, it would be possible to consume the expected US excess stockpile of about 50 MT in two to three units of this type, and it is highly likely that a comparable amount of the FSU excess plutonium could be deposed of in a few VVER-1000`s. The only major capital project for this mode of plutonium disposition would be the weapons-grade plutonium processing which could be done in a dedicated international facility or using existing facilities in the US and FSU under IAEA control. This option offers the potential for quick implementation at a very low cost to the governments of the two countries.
Date: May 24, 1995
Creator: Buckner, M. R.
System: The UNT Digital Library
Towards automatic planning for manufacturing generative processes (open access)

Towards automatic planning for manufacturing generative processes

Generative process planning describes methods process engineers use to modify manufacturing/process plans after designs are complete. A completed design may be the result from the introduction of a new product based on an old design, an assembly upgrade, or modified product designs used for a family of similar products. An engineer designs an assembly and then creates plans capturing manufacturing processes, including assembly sequences, component joining methods, part costs, labor costs, etc. When new products originate as a result of an upgrade, component geometry may change, and/or additional components and subassemblies may be added to or are omitted from the original design. As a result process engineers are forced to create new plans. This is further complicated by the fact that the process engineer is forced to manually generate these plans for each product upgrade. To generate new assembly plans for product upgrades, engineers must manually re-specify the manufacturing plan selection criteria and re-run the planners. To remedy this problem, special-purpose assembly planning algorithms have been developed to automatically recognize design modifications and automatically apply previously defined manufacturing plan selection criteria and constraints.
Date: May 24, 2000
Creator: CALTON,TERRI L.
System: The UNT Digital Library
Active and passive safety control performance in sub - critical, accelerator - driven nuclear reactors. (open access)

Active and passive safety control performance in sub - critical, accelerator - driven nuclear reactors.

Traditional safety performance requirements for nuclear reactors have been developed for critical reactors, whose kinetics characteristics differ significantly from sub-critical, accelerator-driven nuclear reactors. In a critical nuclear reactor, relatively small amounts of reactivity (negative or positive) can produce large changes in the fission rate. In sub-critical reactors, the self-multiplication (k) decreases as the sub-criticality (1-k) increases, and the responsiveness to small reactivity changes decreases. This makes sub-critical nuclear reactors less responsive to positive reactivity insertions than critical reactors. Also, larger negative reactivity insertions are needed in sub-critical reactors to shut down the fission chain if the neutron source remains. This paper presents the results from a computational analysis of the safety performance of sub-critical, accelerator-driven nuclear reactors. Coupled kinetics and thermal-hydraulics models are used to quantify the effectiveness of traditional protection and control system designs in sub-critical reactors. The analyses also quantify the role of inherent, passive reactivity feedback mechanisms in sub-critical reactors. Computational results are used to develop conclusions regarding the most favorable and effective means for reactor control and protection in sub-critical, accelerator-driven nuclear reactors.
Date: May 24, 2002
Creator: Cahalan, J. E. & Eriksson, M.
System: The UNT Digital Library
The Limits of Quintessence (open access)

The Limits of Quintessence

We present evidence that the simplest particle-physics scalar-field models of dynamical dark energy can be separated into distinct behaviors based on the acceleration or deceleration of the field as it evolves down its potential towards a zero minimum. We show that these models occupy narrow regions in the phase-plane of w and w', the dark energy equation-of-state and its time-derivative in units of the Hubble time. Restricting an energy scale of the dark energy microphysics limits how closely a scalar field can resemble a cosmological constant. These results, indicating a desired measurement resolution of order \sigma(w')\approx (1+w), define firm targets for observational tests of the physics of dark energy.
Date: May 24, 2005
Creator: Caldwell, R.R. & Linder, Eric V.
System: The UNT Digital Library
Thermal decomposition and reaction of confined explosives. [TNT, TATB, LX-04, LX-10] (open access)

Thermal decomposition and reaction of confined explosives. [TNT, TATB, LX-04, LX-10]

Some new experiments designed to accurately determine the time interval required to produce a reactive event in confined explosives subjected to temperatures which will cause decomposition are described. Geometry and boundary conditions were both well defined so that these experiments on the rapid thermal decomposition of HE are amenable to predictive modelling. Experiments have been carried out on TNT, TATB and on two plastic-bonded HMX-based high explosives, LX-04 and LX-10. When the results of these experiments are plotted as the logarithm of the time to explosion versus 1/T K (Arrhenius plot), the curves produced are remarkably linear. This is in contradiction to the results obtained by an iterative solution of the Laplace equation for a system with a first order rate heat source. Such calculations produce plots which display considerable curvature. The experiments have also shown that the time to explosion is strongly influenced by the void volume in the containment vessel. Results of the experiments with calculations based on the heat flow equations coupled with first-order models of chemical decomposition are compared. The comparisons demonstrate the need for a more realistic reaction model.
Date: May 24, 1976
Creator: Catalano, E.; McGuire, R.; Lee, E.; Wrenn, E.; Ornellas, D. & Walton, J.
System: The UNT Digital Library
Mesoscale modeling of grain boundary migration under stress using coupled finite element and meshfree methods. (open access)

Mesoscale modeling of grain boundary migration under stress using coupled finite element and meshfree methods.

The process of grain boundary migration involves moving interfaces and topological changes of grain boundary geometry. This can not be effectively modeled by Lagrangian, Eulerian, or arbitrary Lagrangian Eulerian finite element formulation when stress effect is considered. A coupled finite element and meshfree approach is proposed for modeling of grain boundary migration under stress. In this formulation, the material grid carries material kinematic and kinetic variables, whereas the grain boundary grid carries grain boundary kinematic variables. The material domain is discretized by a reproducing kernel partition of unity with built-in strain discontinuity across the grain boundaries. The grain boundaries, on the other hand, are discretized by the standard finite elements. This approach allows an arbitrary evolution of grain boundaries without continuous remeshing.
Date: May 24, 2002
Creator: Chen, J.-S.; Lu, H.; Moldovan, D. & Wolf, D.
System: The UNT Digital Library
Heavy ion clusters in the TDHF approximation. [112 to 384 MeV, cross sections] (open access)

Heavy ion clusters in the TDHF approximation. [112 to 384 MeV, cross sections]

The time-dependent Hartree-Fock method is used to produce time dependent graphical representations of the density contours of the binary cluster in the reactions /sup 14/N(112 MeV) + /sup 12/C, /sup 16/O(384 MeV) + /sup 16/O, and /sup 20/Ne(164 MeV) + /sup 58/Ni. Alpha clustering and multipole shape vibrations are seen. Predictions for d sigma/d..cap omega.., d sigma/dZ/sub f/, and d/sup 2/sigma(E/sub f/)d..cap omega..dE/sub f/vertical/sub z//sub f/ are obtained in the case of /sup 14/N + /sup 12/C and found to agree well with available experimental data. It is concluded that cluster dynamics play an essential role in heavy-ion reactions.
Date: May 24, 1978
Creator: Cusson, R.Y.; Gomez del Campo, J. & Meldner, H.W.
System: The UNT Digital Library
A multi-attribute utility decision analysis for treatment alternatives for the DOE/SR aluminum-based spent nuclear fuel (open access)

A multi-attribute utility decision analysis for treatment alternatives for the DOE/SR aluminum-based spent nuclear fuel

A multi-attribute utility analysis is applied to a decision process to select a treatment method for the management of aluminum-based spent nuclear fuel (Al-SNF) owned by the US Department of Energy (DOE). DOE will receive, treat, and temporarily store Al-SNF, most of which is composed of highly enriched uranium, at its Savannah River Site in South Carolina. DOE intends ultimately to send the treated Al-SNF to a geologic repository for permanent disposal. DOE initially considered ten treatment alternatives for the management of Al-SNF, and has narrowed the choice to two of these: the direct disposal and melt and dilute alternatives. The decision analysis presented in this document focuses on a formal decision process used to evaluate these two remaining alternatives.
Date: May 24, 2000
Creator: DAVIS,FREDDIE J.; WEINER,RUTH FLEISCHMAN; WHEELER,TIMOTHY A.; SORENSON,KEN B. & KUZIO,KENNETH A.
System: The UNT Digital Library
Photonic Doppler Velocimetry Multiplexing Techniques: Evaluation of Photonic Techniques (open access)

Photonic Doppler Velocimetry Multiplexing Techniques: Evaluation of Photonic Techniques

This poster reports progress related to photonic technologies. Specifically, the authors developed diagnostic system architecture for a Multiplexed Photonic Doppler Velocimetry (MPDV) that incorporates frequency and time-division multiplexing into existing PDV methodology to provide increased channel count. Current MPDV design increases number of data records per digitizer channel 8x, and also operates as a laser-safe (Class 3a) system. Further, they applied heterodyne interferometry to allow for direction-of-travel determination and enable high-velocity measurements (>10 km/s) via optical downshifting. They also leveraged commercially available, inexpensive and robust components originally developed for telecom applications. Proposed MPDV architectures employ only commercially available, fiber-coupled hardware.
Date: May 24, 2012
Creator: Daykin, Edward
System: The UNT Digital Library
Limits on the use of Nuclear Explosives for Asteroid Deflection (open access)

Limits on the use of Nuclear Explosives for Asteroid Deflection

None
Date: May 24, 2011
Creator: Dearborn, D S & Bruck, M
System: The UNT Digital Library
The role of phase instabilities in the early material response during laser-induced breakdown in bulk fused silica (open access)

The role of phase instabilities in the early material response during laser-induced breakdown in bulk fused silica

None
Date: May 24, 2011
Creator: Demange, P; Negres, R A; Raman, R N; Colvin, J D & Demos, S G
System: The UNT Digital Library
Bounding the Higgs Width Through Interferometry (open access)

Bounding the Higgs Width Through Interferometry

None
Date: May 24, 2013
Creator: Dixon, Lance J. & Li, Ye
System: The UNT Digital Library
Determining Cross Sections for Reactions on Unstable Nuclei: A Consideration of Indirect Approaches (open access)

Determining Cross Sections for Reactions on Unstable Nuclei: A Consideration of Indirect Approaches

An indirect method for determining cross sections for reactions proceeding through a compound nucleus is presented. The appropriate theoretical framework for applications of this method is reviewed and theoretical and experimental challenges that need to be addressed in applications of the method are outlined. Two approximations are considered and their advantages and limitations are discussed.
Date: May 24, 2005
Creator: Escher, J & Dietrich, F S
System: The UNT Digital Library
Progress in the development of superconducting quadrupoles for heavy ion fusion (open access)

Progress in the development of superconducting quadrupoles for heavy ion fusion

The Heavy Ion Fusion program is developing single aperture superconducting quadrupoles based on NbTi conductor, for use in the High Current Experiment at Lawrence Berkeley National Laboratory. Following the fabrication and testing of prototypes using two different approaches, a baseline design has been selected and further optimized. A prototype cryostat for a quadrupole doublet, with features to accommodate induction acceleration modules, is being fabricated. The single aperture magnet was derived from a conceptual design of a quadrupole array magnet for multi-beam transport. Progress on the development of superconducting quadrupole arrays for future experiments is also reported.
Date: May 24, 2002
Creator: Faltens, A.; Lietzke, A.; Sabbi, G.; Seidl, P.; Lund, S.; Manahan, B. et al.
System: The UNT Digital Library
Enhanced Detection of Proteins in Microchip Separations by On-Chip Preconcentration (open access)

Enhanced Detection of Proteins in Microchip Separations by On-Chip Preconcentration

Microfluidic chips incorporating a semiporous glass filter were used to electrokinetically concentrate proteins on-chip prior to injection and electrophoretic analysis. Signal enhancements of >100-fold could be achieved for the microchip analysis of both native and SDS-denatured proteins using this technique.
Date: May 24, 2001
Creator: Foote, R. S.
System: The UNT Digital Library
Local Magnitude Tomography in California (open access)

Local Magnitude Tomography in California

None
Date: May 24, 2010
Creator: Ford, S R; Uhrhammer, R A & Hellweg, M
System: The UNT Digital Library
PICTURES OF A SUSPECT-TRU RETRIEVAL (open access)

PICTURES OF A SUSPECT-TRU RETRIEVAL

Retrieving ''suspect'' transuranic (TRU) waste from the Hanford Site's low-level waste burial grounds is a tall order, due to conditions that have changed as the work progresses. Project personnel developed several new methods for handling the waste that other retrieval operations may find useful. The Waste Retrieval Project is operated by Fluor Hanford, a prime contractor for the U.S. Department of Energy's Richland Operations Office since 1996.
Date: May 24, 2007
Creator: GADD, R.R.
System: The UNT Digital Library