The compressive constitutive strength behavior of PBXN-110 and its HTPB-based binder system was measured as a function of temperature (-55 C to +20 C) and strain rate (10{sup -3} and 2000 s{sup -1}). PBXN-110 is a plastic bonded explosive (PBX) with relatively high binder content that contains 88wt% HMX and 12wt% HTPB-based binder. A pure analog of the PBXN-110 binder system was tested for comparison to the strain rate and temperature dependence of the composite PBXN-110. As expected, the strength of PBXN-110 was found to exhibit strong temperature and strain rate dependence, attributable to the large fraction of the very soft HTPB binder. The strength of the pure HTPB binder analog was challenging to measure using the split Hopkinson pressure bar (SHPB) because of its extreme softness, however satisfactory results were obtained at and below room temperature by optimizing the SHPB technique. These measurements provide the basis to develop and validate predictive material strength models for PBXN-110.

When a radioactive material gas is accidentally released with a room, the present of the hazardous gas will directly affect the people safety inside. In this study, the flow field and gas dispersion in a ventilated tritium storage room at Los Alamos National Laboratory was simulated using CFX-5.5, a commercially available CFD package using a finite volume methodology. CFD models provide a simultaneously numerical solution of continuity, Navier-Stokes, and energy equations for a flow field geometry with specified boundary conditions. CFX-5 uses a coupled solver, which solves the hydrodynamic equations (for u, v, w, p) as a single system. This reduces the number of iterations required for convergence to a steady state, and to a transient analysis solution for each time step in time-dependant gas dispersion as well.

When a hazardous aerosol or gas is inadvertently or deliberately released in an occupied facility, the airborne material presents a hazard to people. Inadvertent accidents and exposures continue to occur in Los Alamos and other nuclear facilities despite state-of-art engineering and administrative controls, and heightened diligence. Despite the obvious need in occupational settings and for homeland defense, the body of research in hazardous aerosol dispersion and control in large, complex, ventilated enclosures is extremely limited. The science governing generation, transport, inhalation, and detection of airborne hazards is lacking and must be developed to where it can be used by engineers or safety professionals in the prediction of worker exposure, in the prevention of accidents, or in the mitigation of terrorist actions. In this study, a commercial computational fluid dynamics (CFD) code, CFX5.4, and experiments were used to assess flow field characteristics, and to investigate aerosol release and transport in a large, ventilated workroom in a facility at Savannah River Site. Steady state CFD results illustrating a complex, ventilation-induced, flow field with vortices, velocity gradients, and quiet zones are presented, as are time-dependent CFD and experimental aerosol dispersion results. The comparison of response times between CFD and experimental results was favorable. …

Damage diagnosis is a problem that can be addressed at many levels. Stated in its most basic form, the objective is to ascertain simply if damage is present or not. In a statistical pattern recognition paradigm of this problem, the philosophy is to collect baseline signatures from a system to be monitored and to compare subsequent data to see if the new 'pattern' deviates significantly from the baseline data. Unfortunately, matters are seldom as simple as this. In reality, structures will be subjected to changing environmental and operational conditions that will affect measured signals. In this case, there may be a wide range of normal conditions, and it is clearly undesirable to signal damage simply because of a change in the environment. In this paper, a unique combination of time series analysis, neural networks, and statistical inference techniques is developed for damage classification explicitly taking into account these natural variations of the system in order to minimize false positive indication of true system changes.

Los Alamos National Laboratory has recognized that security infractions are often the consequence of various types of human errors (e.g., mistakes, lapses, slips) and/or breaches (i.e., deliberate deviations from policies or required procedures with no intention to bring about an adverse security consequence) and therefore has established an error reduction program based in part on the techniques used to mitigate hazard and accident potentials. One cornerstone of this program, definition of the situational and personal factors that increase the likelihood of employee errors and breaches, is detailed here. This information can be used retrospectively (as in accident investigations) to support and guide inquiries into security incidents or prospectively (as in hazard assessments) to guide efforts to reduce the likelihood of error/incident occurrence. Both approaches provide the foundation for targeted interventions to reduce the influence of these factors and for the formation of subsequent 'lessons learned.' Overall security is enhanced not only by reducing the inadvertent releases of classified information but also by reducing the security and safeguards resources devoted to them, thereby allowing these resources to be concentrated on acts of malevolence.

Cylindrical experiments were performed on the OMEGA laser at the University of Rochester to study unstable interfaces in single and double shells. For single shells a marker layer of more opaque and higher density material is placed between foam and an outside ablator. The marker is either smooth or with a well defined surface roughness. For double shells an inner cylinder is placed along the outer cylinder axis. The outer cylinder is irradiated directly with 50 laser beams which produces a strong shock (mach number 5-15) that passes through the unstable marker interf'ace creating a Richtmyer-Meshkov (RM) instability. For double shells this shock bounces off the inner cylinder back to the incoming marker layer causing it to decelerate. We present comparisons of the measured smooth marker layer hydrodynamics with computer simulations using both Lagrangian and Eulerian codes.

One key issue in optimizing critical current density (J,) in MgB2 is to determine which structural features are the relevant pinning centers. Likely sources of vortex pinning include grain boundaries and intra-grain defects. Detailed studies of the field (H) and temperature (T) dependence of pinning in microstructurally well-characterized samples are required to clarify this point. In this work we explore the influence of microstructures on the vortex dynamics of MgB2 bulk samples prepared either at ambient or at high pressure (HIP). Scanning and transmission electron microscopy indicate the presence of several types of defects. Both un-HIPed and HIPed samples contain a large number of intra-grain Mg(B,0)2 precipitates coherent with the matrix, with sizes ranging from 5 nm to 100 nm, which are very well suited to act as pinning centers. The HIP process further improves flux pinning by eliminating the porosity, dispersing the MgO present at the grain boundaries of the un-HIPed samples, and generating dislocations. We also present a detailed study of the T, H and current density (J) dependence of the normalized time relaxation rate, S=dlnJ/dlnt. The intermediate transition temperature T, - 39K makes MgB2 attractive for exploring vortex dynamics in a regime of intermediate influence of thermal …

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Critical masses of square-prisms of highly enriched uranium diluted in various X/235U ratios with matrix material and polyethylene were measured. The Configuration cores were 22.86-cm and 45.72-cm square and were reflected with 8.1 3-cm and 10.1 6-cm thick side polyethylene reflectors, respectively. The configurations had 10.1 6-cm thick top and bottom polyethylene reflectors. For some configurations, the Rossi-a, which is an eigenvalue value characteristic for a particular configuration, was measured to establish a reactivity scale based on the degree of subcriticality . Finally, the critical mass experiments are compared with values calculated with MCNP and ENDF/B-VI cross-sections.

We present key improvements to growing high quality ({approx}7 degrees {Delta}{phi}) magnesium oxide (MgO) The use of a new layer for IBAD MgO nucleation and reduction in surface roughness of substrates have resulted in better in-plane texture. The processing window for obtaining optimum template texture is very narrow ({approx}10 seconds) using Si,N,. This has been ameliorated by use of an alternate amorphous nucleation layer. The substrate surface roughness has a significant effect on the initial nucleation texture of IBAD MgO films. A surface roughness of -1 nm has resulted in better in-plane texture for IBAD MgO films deposited on metal substrates. We have also implemented a method to quantify IBAD MgO texture using reflected high-energy electron diffraction (RHEED). Utilizing this in situ tool, we have been able to refine deposition parameters to routinely grow films in batch mode that have a {Delta}{phi} of {approx} 7 degrees. Deposited meter lengths have had {Delta}{phi} values from 7-9 degrees with 10% uniformity. One to two micrometer thick YBCO films on these templates have had critical current densities in excess of 1 MA/cm2 at 75 K, in self field.

The first and most important objective of any damage identification algorithms is to ascertain with confidence if damage is present or not. Many methods have been proposed for damage detection based on ideas of novelty detection founded in pattern recognition and multivariate statistics. The philosophy of novelty detection is simple. Features are first extracted from a baseline system to be monitored, and subsequent data are then compared to see if the new features are outliers, which significantly depart from the rest of population. In damage diagnosis problems, the assumption is that outliers are generated from a damaged condition of the monitored system. This damage classification necessitates the establishment of a decision boundary. Choosing this threshold value is often based on the assumption that the parent distribution of data is Gaussian in nature. While the problem of novelty detection focuses attention on the outlier or extreme values of the data i.e. those points in the tails of the distribution, the threshold selection using the normality assumption weighs the central population of data. Therefore, this normality assumption might impose potentially misleading behavior on damage classification, and is likely to lead the damage diagnosis astray. In this paper, extreme value statistics is integrated …

Structural health monitoring (SHM) is fast becoming a field of great importance as engineers seek for new ways to ensure the safety of structures throughout their designed lifetime. Current methods for analyzing the dynamic response of structures often use standard frequency response functions to model linear system input/output relationships. However, these functions do not account for the nonlinear response of a system, which damage often introduces. In this study, an auto-regressive model with exogenous inputs (ARX) in the frequency domain is used to extract damage sensitive features, explicitly considering the nonlinear effect in the frequency domain. Furthermore, because of the non-Gaussian nature of the extracted features, extreme value statistics (EVS) is employed to develop a robust damage classifier. The applicability of the ARX model combined with EVS to nonlinear damage detection is demonstrated using vibration data obtained from a laboratory experiment of a three-story building model.

The strengths of metallic multilayers, composed of alternating layers o f soft metals such as Cu and Nb, approach the theoretical limit of material strengih when the bilayer periods are on the order of a few nanometers. We have investigated the damage mechanisms in these ultra-high strength nanolayered composite inaterials subjected to monotonic deformation. Large strain plastic deformation such as rooin temperature rolling does not lead to any dislocation cell structure formation within the layers indicating that the deformation and dislocation storage mechanisms in nanostructured materials are completely different from the bulk. In bulk metals, dislocation pile-ups lead to heterogeneous slip, but in nano-materials, deformation by single disloqations on closely spaced glide planes results in more homogeneously distributed slip. The implications of the high tensile strengths and hoinogencous slip on the fatigue properties of nanolayered materials are also discussed.

Measurements of neutron capture on unstable nuclei are important for studies of s-process nucleosynthesis, nuclear waste transmutation, and stewardship science. A 160-element, 4{pi} barium fluoride detector array, and associated neutron flight path, is being constructed to make capture measurements at the moderated neutron spallation source at LANSCE. Measurements can be made on as little as 1 mg of sample material over energies from near thermal to near 100 keV. The design of the DANCE array is described and neutron flux measurements from flight path commissioning are shown. The array is expected to be complete by the end of 2002.

The design of the interior portions of the Dual Axis Radiographic Hydrodynamic Test (DARHT) Facility incorporated shielding and controls from the beginning of the installation of the Accelerators. The purpose of the design and analysis was to demonstrate the adequacy of shielding or to determine the need for additional shielding or controls. Two classes of events were considered: (1) routine operation defined as the annual production of 10,000 2000-ns pulses of electrons at a nominal energy of 20 MeV, some of which are converted to the x-ray imaging beam consisting of four nominal 60-ns pulses over the 2000-ns time frame, and (2) accident case defined as up to 100 2000-ns pulses of electrons accidentally impinging on some metallic surface, thereby producing x rays. Several locations for both classes of events were considered inside and outside of the accelerator hall buildings. The analysis method consisted of the definition of a source term for each case studied and the definition of a model of the shielding and equipment present between the source and the dose areas. A minimal model of the fixed existing or proposed shielding and equipment structures was used for a first approximation. If the resulting dose from the first …

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Materials with Si-C-N composition are of great interest due to their remarkable properties such as high hardness and oxidation resistance. In this study amorphous silicon nitride and silicon carbonitride films were deposited on glass, fised silica, and carbon substrates by the plasma immersion ion processing technique. Gas pressure during the deposition was kept around 0.13 Pa (1 mTorr) and S a, N2, Ar, and C2H2 gas mixtures were used. Film hardness, composition, and UV-visible optical absorption were characterized using nanoindentati on, ion beam analysis techniques, and UV-visible spectroscopy, respectively. The films exhibit high transparency in the visible and near UV regions. Addition of the carbon to the films causes decrease in the density of the films, as well as decrease in hardness and transparency. These results suggest that in the low energy regime of PTIP the deposition of hard carbon composites with nitrogen and silicon does not take place.

Transverse shear at the interface of two solids occurs when these solids move at different velocities. This frictional phenomenon is being studied in a series of experiments on the ATLAS capacitor bank at Los Alamos. Cylindrical targets to test friction force models are composed of alternating regions of high- and low-shock speed materials. When the target is impacted by a cylindrical, magnetically-accelerated aluminum liner, the differential shock velocity in the two materials establishes the desired shear at the interface. One- and two-dimensional MHD calculations have been performed to design liners with suitable properties to drive these 'friction-like' ATLAS experiments. A thick impactor allows the shock to be maintained for several microseconds. The ATLAS experiments use a liner that is approximately 10 mm thick at impact, with an inner surface velocity of {approx} 1.4-1.5 km/s. Interaction of this thick liner with the electrodes, or glide planes, results in significant deformation of the hardened stainless steel electrodes. Data from the ATLAS experiments and comparisons with the calculations will be presented, along with plans for future experiments.

The Spallation Neutron Source (SNS) is a facility being designed for scientific and industrial research and development. The SNS will generate and employ neutrons as a research tool in a variety of disciplines including biology, material science, superconductivity, chemistry, etc. The neutrons will be produced by bombarding a heavy metal target with a high-energy beam of protons, generated and accelerated with a linear particle accelerator, or linac. The low energy end of the linac consists of, in part, a multi-cell copper structure termed a coupled cavity linac (CCL). The CCL is responsible for accelerating the protons from an energy of 87 MeV, to 185 MeV. Acceleration of the charged protons is achieved by the use of large electrical field gradients established within specially designed contoured cavities of the CCL. While a large amount of the electrical energy is used to accelerate the protons, approximately 60-80% of this electrical energy is dissipated in the CCL's copper structure. To maintain an acceptable operating temperature, as well as minimize thermal stresses and maintain desired contours of the accelerator cavities, the electrical waste heat must be removed from the CCL structure. This is done using specially designed water cooling passages within the linac's copper …

A design approach based on a stream function with a single angular Fourier component can be used to specify the end-turn configuration in magnet windings with discrete blocks of conductors. The design approach is especially appropriate for large-bore, current-dominated magnets with many turns. The design method can be summarized as follows: First find a winding-block layout (block angles, number of turns in each block, etc.) for the central, straight-conductor part of the windings that produces two-dimensional fields with negligible higher harmonic content. Next, specify the numbers of groups of conductors into which each block of the 2-D part of the winding fans out in the end-turn region. Also specify the end-zone axial length and the shape-function profile for the end zones. Finally, generate turn contours by finding conductor-group centerline curves in the developed (flattened) cylinder surface that are contours of constant stream function. Individual turns are specified by constant parallel displacement from the group centerline curve in the developed winding surface. An interactive computer program performs the above steps has been written and has been used to design end windings for a test quadrupole example. The unwanted higher harmonics in both peak and integral fields as computed by the Biot-Savart …

Control can improve the performance of wind turbines by enhancing energy capture and reducing dynamic loads.At the National Renewable Energy Laboratory, we are beginning to design control algorithms for regulation of turbine speed and power using state-space control designs. In this paper, we describe the design of such a control algorithm for regulation of rotor speed in full-load operation (region 3) for a two-bladed wind turbine. We base our control design on simple linear models of a turbine, which contain rotor and generator rotation, drivetrain torsion, and rotor flap degrees of freedom (first mode only). We account for wind-speed fluctuations using disturbance-accommodating control. We show the capability of these control schemes to stabilize the modeled turbine modes via pole placement while using state estimation to reduce the number of turbine measurements that are needed for these control algorithms. We incorporate these controllers into the FAST-AD code and show simulation results for various conditions. Finally, we report conclusions to this work and outline future studies.

The Detector for Advanced Neutron Capture Experiments (DANCE) is a 159-element 4x barium fluoride array designed to study neutron capture on small quantities, 1 mg or less, of radioactive nuclides. It is being built on a 20 m neutron flight path which views the 'upper tier' water moderator at the Manuel J. Lujan Jr. Neutron Scattering Center at the Los Alamos Neutron Science Center. The detector design is based on Monte Carlo calculations which have suggested ways to minimize backgrounds due to neutron scattering events. A data acquisition system based on fast transient digitizers is bcing implemented

Integrated Safety Management (ISM) is structured to manage and control work at the activity level. Fundamental to ISM is that all work will be performed safely while meeting the applicable institutional-, facility-, and activity-level expectations. High and medium initial risk activities require certain levels of independent peer and/or Environmental, Health & Safety subject matter expert reviews prior to authorization. A key responsibility of line management and chemical workers is to assign initial risk adequately, so that the proper reviews are obtained. Thus, the effectiveness of an ISM system is largely dependent upon the adequacy and accuracy of this initial risk determination. In the following presentation, a Risk Determination Model (RDM) is presented for physical, health and ecological hazards associated with materials. Magnitude of exposure (Le., dose or concentration), frequency, duration, and quantity are the four factors most difficult to capture in a research and development setting. They are factored into the determination, as a function of the quantity of material. Quantity and magnitude of exposure components are simplified by using boundary criteria. This RDM will promote conformity and consistency in the assignment of risk to hazardous material activities. In conclusion, the risk assessors (line manager and chemical worker) should be …

We have investigated the adsorptiodreaction of deuterium on water pre-adsorbed oxidized uranium-niobium alloys at pressures near 1 Torr. Deuterium exposures were conducted at pressures from 1 to 4 Torr at surface temperatures between 300 and 600 K using a fixed dosing time of 30 seconds. Water is preadsorbed at room temperature at a pressure of {approx} 1 Torr for 30 seconds. Subsequent to gaseous exposure the surface temperature of the alloy was increased in a controlled manner and deuterium desorption was monitored using mass spectroscopy. Deuterium is observed to adsorb both at the surface and in the bulk of the uranium-niobium alloys. Water preadsorption prevents deuterium adsorption on all surfaces. The water forms a surface passivation layer at low temperatures that prevents deuterium uptake into the bulk and surface of the sample. As the adsorption temperature of the deuterium increases the amount of deuterium that adsorbs also increases.