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MCNP load balancing and fault tolerance with PVM

Description: Version 4A of the Monte Carlo neutron, photon, and electron transport code MCNP, developed by LANL (Los Alamos National Laboratory), supports distributed-memory multiprocessing through the software package PVM (Parallel Virtual Machine, version 3.1.4). Using PVM for interprocessor communication, MCNP can simultaneously execute a single problem on a cluster of UNIX-based workstations. This capability provided system efficiencies that exceeded 80% on dedicated workstation clusters, however, on heterogeneous or multiuser systems, the performance was limited by the slowest processor (i.e., equal work was assigned to each processor). The next public release of MCNP will provide multiprocessing enhancements that include load balancing and fault tolerance which are shown to dramatically increase multiuser system efficiency and reliability.
Date: July 1995
Creator: McKinney, G. W.
Partner: UNT Libraries Government Documents Department

Design of standards for nondestructive assay of special nuclear material

Description: Nondestructive assay (NDA) of special nuclear material (SNM) involves a variety of measurement techniques, instruments, and nuclear materials. High-quality measurements require well-characterized SNM standards that represent the expected range of mass, chemical composition, and physical properties of the SNM to be measured. Due to the very limited commercial availability of NDA standards, facilities must usually produce their own standards, both to meet their specific measurement needs and to comply with existing regulations. This paper will describe the current extent to which NDA standards are commercially available. The authors will further describe the types of NDA standards used to calibrate and verify the measurement techniques commonly used in the safeguards of SNM. Several types of NDA standards will be discussed in detail to illustrate the considerations that go into specifying and designing traceable, representative standards for materials accounting measurements.
Date: May 1997
Creator: Smith, H. A., Jr.; Stewart, J. E. & Ruhter, W.
Partner: UNT Libraries Government Documents Department

Engineering models of deflagration-to-detonation transition

Description: For the past two years, Los Alamos has supported research into the deflagration-to-detonation transition (DDT) in damaged energetic materials as part of the explosives safety program. This program supported both a theory/modeling group and an experimentation group. The goal of the theory/modeling group was to examine the various modeling structures (one-phase models, two-phase models, etc.) and select from these a structure suitable to model accidental initiation of detonation in damaged explosives. The experimental data on low-velocity piston supported DDT in granular explosive was to serve as a test bed to help in the selection process. Three theoretical models have been examined in the course of this study: (1) the Baer-Nunziato (BN) model, (2) the Stewart-Prasad-Asay (SPA) model and (3) the Bdzil-Kapila-Stewart model. Here we describe these models, discuss their properties, and compare their features.
Date: July 1995
Creator: Bdzil, J. B. & Son, S. F.
Partner: UNT Libraries Government Documents Department

Authentication of reprocessing plant safeguards data through correlation analysis

Description: This report investigates the feasibility and benefits of two new approaches to the analysis of safeguards data from reprocessing plants. Both approaches involve some level of plant modeling. All models involve some form of mass balance, either applied in the usual way that leads to material balances for individual process vessels at discrete times or applied by accounting for pipe flow rates that leads to material balances for individual process vessels at continuous times. In the first case, material balances are computed after each tank-to-tank transfer. In the second case, material balances can be computed at any desired time. The two approaches can be described as follows. The first approach considers the application of a new multivariate sequential test. The test statistic is a scalar, but the monitored residual is a vector. The second approach considers the application of recent nonlinear time series methods for the purpose of empirically building a model for the expected magnitude of a material balance or other scalar variable. Although the report restricts attention to monitoring scalar time series, the methodology can be extended to vector time series.
Date: April 1, 1995
Creator: Burr, T.L.; Wangen, L.E. & Mullen, M.F.
Partner: UNT Libraries Government Documents Department

Automated grid generation from models of complex geologic structure and stratigraphy

Description: The construction of computational grids which accurately reflect complex geologic structure and stratigraphy for flow and transport models poses a formidable task. With an understanding of stratigraphy, material properties and boundary and initial conditions, the task of incorporating this data into a numerical model can be difficult and time consuming. Most GIS tools for representing complex geologic volumes and surfaces are not designed for producing optimal grids for flow and transport computation. We have developed a tool, GEOMESH, for generating finite element grids that maintain the geometric integrity of input volumes, surfaces, and geologic data and produce an optimal (Delaunay) tetrahedral grid that can be used for flow and transport computations. GEOMESH also satisfies the constraint that the geometric coupling coefficients of the grid are positive for all elements. GEOMESH generates grids for two dimensional cross sections, three dimensional regional models, represents faults and fractures, and has the capability of including finer grids representing tunnels and well bores into grids. GEOMESH also permits adaptive grid refinement in three dimensions. The tools to glue, merge and insert grids together demonstrate how complex grids can be built from simpler pieces. The resulting grid can be utilized by unstructured finite element or integrated finite difference computational physics codes.
Date: April 1, 1996
Creator: Gable, C.; Trease, H. & Cherry, T.
Partner: UNT Libraries Government Documents Department

Automated Information System (AIS) Alarm System

Description: The Automated Information Alarm System is a joint effort between Los Alamos National Laboratory, Lawrence Livermore National Laboratory, and Sandia National Laboratory to demonstrate and implement, on a small-to-medium sized local area network, an automated system that detects and automatically responds to attacks that use readily available tools and methodologies. The Alarm System will sense or detect, assess, and respond to suspicious activities that may be detrimental to information on the network or to continued operation of the network. The responses will allow stopping, isolating, or ejecting the suspicious activities. The number of sensors, the sensitivity of the sensors, the assessment criteria, and the desired responses may be set by the using organization to meet their local security policies.
Date: May 1, 1997
Creator: Hunteman, W.
Partner: UNT Libraries Government Documents Department

Atmospheric transport of neutrons and gamma rays from a high-altitude nuclear detonation

Description: Although radiation outputs from nuclear detonations in free space are well established, few studies exist of effect of atmospheric transport on the resulting intensity, energy, and time signatures. This report presents calculations for generic sources at high altitudes, 20-50 km above the Earth`s surface, in an atmosphere whose density decreases almost exponentially with height. The sources are instantaneous time bursts with simple energy dependences: gamma rays use an evaporation spectrum; neutrons use either a Gaussian fusion or a Maxwell fission spectrum. The observation angles vary from vertical to 5{degrees} below the horizon, and detectors are placed in either geosynchronous or low Earth orbits (100 km). All calculations use the Monte Carlo N-Particle (MCNP) transport code in either its photon, neutron, or coupled neutron-photon modes, with the coupled mode being applied to the production of gamma rays by neutron inelastic scattering. The standard MCNP outputs are analyzed to extract the intensity, energy, and time dependences of the fluence as functions of either source altitude or observation angle. In general, the intensities drop rapidly below about 30-km source altitude or +5` slant angle. Above these limits, the gamma-ray signal loses substantial intensity but still contains most of the original source information. In contrast, neutron scattering produces little or no decrease in intensity, but it rapidly degrades much of the information about the original source spectrum. Finally, although there is abundant gamma-ray production from neutron inelastic scattering, the resulting signatures appear to provide little additional information.
Date: July 1, 1995
Creator: Byrd, R.C.
Partner: UNT Libraries Government Documents Department

Atmospheric transport of neutrons and gamma rays from near-horizon nuclear detonations

Description: This report continues a study of the transport of neutrons and rays from nuclear detonations at high altitudes to a set of detectors, with an emphasis on the limiting case of sources even beyond the horizon. To improve the calculational efficiency, the standard arrangement of a single source with multiple detectors is transformed to an equivalent one with a single detector and sources at multiple locations. Particular attention is paid to the critical problem of transport at near-horizon angles in an atmosphere whose density decreases exponentially with altitude. As a check, calculations for this region are made using both analytical and Monte Carlo approaches. For sources approaching the horizon, the fluence of gamma rays and neutrons reaching the detector drops gradually as the increasing column density attenuates the direct, unscattered fluence. Near the grazing angle, the direct fluence plummets, but the scattered component continues to decrease slowly and remains observable. Over this range, the timedependent flux of direct-plus-scattered gamma rays changes dramatically in both shape and magnitude, but it probably remains distinct from typical natural backgrounds. The neutron time-of-flight spectrum is dominated by scattering and reflects only the most important aspects of the original source spectrum; its most obvious features are a prominent low-energy tail and the resonance structure produced by nuclear interactions in the atmosphere. In some cases, the fluence of secondary gamma rays produced by these interactions may be larger than that from the source itself.
Date: March 1, 1996
Creator: Byrd, R.C. & Heerema, B.D.
Partner: UNT Libraries Government Documents Department

Atomistic simulation of point defects and dislocations in bbc transition metals from first principles

Description: Using multi-ion interatomic potentials derived from first-principles generalized pseudopotential theory, we have been studying point defects and dislocations in bcc transition metals, with molybdenum (Mo) as a prototype. For point defects in Mo, the calculated vacancy formation and activation energies are in excellent agreement with experimental results. The energetics of six self-interstitial configurations in Mo have also been investigated. The <110> split dumb-bell is found to have the lowest formation energy, as is experimentally observed, but the corresponding migration energy is calculated to be 3--15 times higher than previous theoretical estimates. The atomic structure and energetics of <111> screw dislocations in Mo are now being investigated. We have found that the ``easy`` core configuration has a lower formation energy than the ``hard`` one, consistent with previous theoretical studies. The former has a distinctive 3-fold symmetry with a spread out of the dislocation core along the <112> directions, an effect which is driven by the strong angular forces present in these metals.
Date: January 19, 1996
Creator: Xu, W & Moriarty, J.A.
Partner: UNT Libraries Government Documents Department

Attack optimization at moderate force levels

Description: Optimal offensive missile allocations for moderate offensive and defensive forces are derived and used to study their sensitivity to force structure parameters levels. It is shown that the first strike cost is a product of the number of missiles and a function of the optimum allocation. Thus, the conditions under which the number of missiles should increase or decrease in time is also determined by this allocation.
Date: April 1, 1997
Creator: Canavan, G.H.
Partner: UNT Libraries Government Documents Department

Automated nuclear material recovery and decontamination of large steel dynamic experiment containers

Description: A key mission of the Los Alamos National Laboratory (LANL) is to reduce the global nuclear danger through stockpile stewardship efforts that ensure the safety and reliability of nuclear weapons. In support of this mission LANL performs dynamic experiments on special nuclear materials (SNM) within large steel containers. Once these experiments are complete, these containers must be processed to recover residual SNM and to decontaminate the containers to below low level waste (LLW) disposal limits which are much less restrictive for disposal purposes than transuranic (TRU) waste limits. The purpose of this paper is to describe automation efforts being developed by LANL for improving the efficiency, increasing worker safety, and reducing worker exposure during the material cleanout and recovery activities performed on these containers.
Date: March 1, 1999
Creator: Dennison, D.K.; Gallant, D.A.; Nelson, D.C.; Stovall, L.A. & Wedman, D.E.
Partner: UNT Libraries Government Documents Department

Automatic beam position control at Los Alamos Spallation Radiation Effects Facility (LASREF)

Description: Historically the Los Alamos Spallation Radiation Effects Facility (LASREF) has used manual methods to control the position of the 800 kW, 800 MeV proton beam on targets. New experiments, however, require more stringent position control more frequently than can be done manually for long periods of time. Data from an existing harp is used to automatically adjust steering magnets to maintain beam position to required tolerances.
Date: August 1, 1997
Creator: Oothoudt, M.; Pillai, C. & Zumbro, M.
Partner: UNT Libraries Government Documents Department

Automatic identification of NDA measured items: Use of E-tags

Description: This paper describes how electronic identification devices or E-tags could reduce the time spent by LAEA inspectors making nondestructive assay (NDA) measurements. As one example, the use of E-tags with a high-level neutron coincidence counter (HLNC) is discussed in detail. Sections of the paper include inspection procedures, system description, software, and future plans. Mounting of E-tabs, modifications to the HLNC, and the use of tamper indicating devices are also discussed. The technology appears to have wide application to different types of nuclear facilities and inspections and could significantly change NDA inspection procedures.
Date: July 1, 1995
Creator: Chitumbo, K.; Olsen, R.; Hatcher, C.R. & Kadner, S.P.
Partner: UNT Libraries Government Documents Department

A 2.14 ms candidate optical pulsar in SN1987A: Ten years after

Description: We have monitored Supernova 1987A in optical/near-infrared bands from a few weeks following its birth until the present time in order to search for a pulsar remnant. We have found an apparent pattern of emission near the frequency of 467.5 Hz - a 2.14 ms pulsar candidate, first detected in data taken on the remnant at the Las Campanas Observatory (LCO) 2.5-m Dupont telescope during 14-16 Feb. 1992 UT. We detected further signals near the 2.14 ms period on numerous occasions over the next four years in data taken with a variety of telescopes, data systems and detectors, at a number of ground- and space-based observatories. The sequence of detections of this signal from Feb. `92 through August `93, prior to its apparent subsequent fading, is highly improbable (< 10{sup -10} for any noise source). We also find evidence for modulation of the 2.14 ms period with a {approx}1,000 s period which, when taken with the high spindown of the source (2-3 x 10{sup -10} Hz/s), is consistent with precession and spindown via gravitational radiation of a neutron star with a non- axisymmetric oblateness of {approx}10{sup -6}, and an implied gravitational luminosity exceeding that of the Crab Nebula pulsar by an order of magnitude.
Date: September 1, 1997
Creator: Middleditch, J.; Kristian, J.A.; Kunkel, W.E.; Hill, K.M. & Watson, R.D.
Partner: UNT Libraries Government Documents Department

3-dimensional wells and tunnels for finite element grids

Description: Modeling fluid, vapor, and air injection and extraction from wells poses a number of problems. The length scale of well bores is centimeters, the region of high pressure gradient may be tens of meters and the reservoir may be tens of kilometers. Furthermore, accurate representation of the path of a deviated well can be difficult. Incorporating the physics of injection and extraction can be made easier and more accurate with automated grid generation tools that incorporate wells as part of a background mesh that represents the reservoir. GEOMESH is a modeling tool developed for automating finite element grid generation. This tool maintains the geometric integrity of the geologic framework and produces optimal (Delaunay) tetrahedral grids. GEOMESH creates a 3D well as hexagonal segments formed along the path of the well. This well structure is tetrahedralized into a Delaunay mesh and then embedded into a background mesh. The well structure can be radially or vertically refined and each well layer is assigned a material property or can take on the material properties of the surrounding stratigraphy. The resulting embedded well can then be used by unstructured finite element models for gas and fluid flow in the vicinity of wells or tunnels. This 3D well representation allows the study of the free- surface of the well and surrounding stratigraphy. It reduces possible grid orientation effects, and allows better correlation between well sample data and the geologic model. The well grids also allow improved visualization for well and tunnel model analysis. 3D observation of the grids helps qualitative interpretation and can reveal features not apparent in fewer dimensions.
Date: April 1, 1996
Creator: Cherry, T.A.; Gable, C.W. & Trease, H.
Partner: UNT Libraries Government Documents Department

A 6.7 MeV cw RFQ linac

Description: A 6.7-MeV 350 MHz, cw Radio Frequency Quadrupole proton linac has been designed and is being fabricated for the Accelerator Production of Tritium Project at Los Alamos. This eight-meter long structure consists of four resonantly-coupled segments and is being fabricated using hydrogen furnace brazing as a joining technology. Details of the design and status of fabrication are reported.
Date: August 1, 1997
Creator: Schrage, D.; Young, L.; Clark, W.; Davis, T.; Martinez, F.; Naranjo, A. et al.
Partner: UNT Libraries Government Documents Department

HEL-1: A DEMG Based Demonstration of Solid Liner Implosions at 100 MA

Description: In August 1997, the Los Alamos National Laboratory (LANL) and the All-Russian Scientific Research Institute of Experimental Physics (VNIIEF) conducted a joint experiment in Sarov, Russia to demonstrate the feasibility of applying explosive pulsed power technology to implode large scale, high velocity cylindrical liners. Kilogram mass metal liners imploding at velocities of 5-25 km/sec are useful scientific tools for producing high energy density environments, ultra high pressure shocks, and for the rapid compression of plasmas. To explore the issues associated with the design, operation and diagnosis of such implosions, VNIIEF and LANL designed and executed an practical demonstration in which a liner of approximately 1 kilogram mass was accelerated to 510 km/sec while undergoing a convergence of about 4:1. The scientific objectives of the experiment were threefold. First to explore the limits of very large, explosive, pulse power system delivering about 100 MA as drivers for accelerating solid density imploding liners to kinetic energies of 25 MJ or greater. Second to evaluate the behavior of single material (aluminum) liners imploding at 510 km/sec velocities by comparing experimental data with 1-D and 2-D numerical simulations. Third, to evaluate the condition of the selected liner at radial convergence of 4 and a final radius of 6 cm. A liner of such parameters could be used as a driver for equation of state measurements at megabar pressures or as a driver for a future experiment in which a magnetized fusion plasma would be compressed to approach ignition conditions.
Date: December 1997
Creator: Reinovsky, R. E.; Anderson, B. G. & Clark, D. A.
Partner: UNT Libraries Government Documents Department

Los Alamos National Laboratory summary plan to fabricate mixed oxide lead assemblies for the fissile material disposition program

Description: This report summarizes an approach for using existing Los Alamos National Laboratory (Laboratory) mixed oxide (MOX) fuel-fabrication and plutonium processing capabilities to expedite and assure progress in the MOX/Reactor Plutonium Disposition Program. Lead Assembly MOX fabrication is required to provide prototypic fuel for testing in support of fuel qualification and licensing requirements. It is also required to provide a bridge for the full utilization of the European fabrication experience. In part, this bridge helps establish, for the first time since the early 1980s, a US experience base for meeting the safety, licensing, safeguards, security, and materials control and accountability requirements of the Department of Energy and Nuclear Regulatory Commission. In addition, a link is needed between the current research and development program and the production of disposition mission fuel. This link would also help provide a knowledge base for US regulators. Early MOX fabrication and irradiation testing in commercial nuclear reactors would provide a positive demonstration to Russia (and to potential vendors, designers, fabricators, and utilities) that the US has serious intent to proceed with plutonium disposition. This report summarizes an approach to fabricating lead assembly MOX fuel using the existing MOX fuel-fabrication infrastructure at the Laboratory.
Date: December 1, 1997
Creator: Buksa, J.J.; Eaton, S.L.; Trellue, H.R.; Chidester, K.; Bowidowicz, M.; Morley, R.A. et al.
Partner: UNT Libraries Government Documents Department

Los Alamos National Laboratory transuranic database analysis

Description: This paper represents an overview of analyses conducted on the TRU database maintained by the Los Alamos National Laboratory (LANL). This evaluation was conducted to support the ``TRU Waste Workoff Strategies`` document and provides an estimation of the waste volume that potentially could be certified and ready for shipment to (WIPP) in April of 1998. Criteria defined in the WIPP WAC, including container type, weight limits, plutonium fissile gram equivalents and decay heat, were used to evaluated the waste for compliance. LANL evaluated the containers by facility and by waste stream to determining the most efficient plan for characterization and certification of the waste. Evaluation of the waste presently in storage suggested that 40- 60% potentially meets the WIPP WAC Rev. 5 criteria.
Date: February 1, 1997
Creator: Christensen, D.V.; Rogers, P.S.Z.; Kosiewicz, S.T. & LeBrun, D.B.
Partner: UNT Libraries Government Documents Department

Los Alamos National Laboratory Yucca Mountain Project publications (1979--1994)

Description: This over-300 title publication list reflects the accomplishments of Los Alamos Yucca Mountain Site Characterization Project researchers, who, since 1979, have been conducting multidisciplinary research to help determine if Yucca Mountain, Nevada, is a suitable site for a high-level waste repository. The titles can be accessed in two ways: by year, beginning with 1994 and working back to 1979, and by subject area: mineralogy/petrology/geology, volcanism, radionuclide solubility/groundwater chemistry; radionuclide sorption and transport; modeling/validation/field studies; summary/status reports, and quality assurance.
Date: November 1, 1995
Creator: Bowker, L.M.; Espinosa, M.L. & Klein, S.H.
Partner: UNT Libraries Government Documents Department

Los Alamos National Laboratory Yucca Mountain Site Characterization Project 1992 quality program status report

Description: This status report summarizes the activities and accomplishments of the Los Alamos Yucca Mountain Site Characterization Project`s quality assurance program for calendar year 1992. The report includes major sections on Program Activities and Trend Analysis. Program Activities are discussed periodically at quality meetings. The most significant issue addressed in 1992 has been the timely revision of quality administrative procedures. The procedure revision process was streamlined from 55 steps to 7. The number of forms in procedures was reduced by 38%, and the text reduced by 29%. This allowed revision in 1992 of almost half of all implementing procedures. The time necessary to complete the revision process (for a procedure) was reduced from 11 months to 3 months. Other accomplishments include the relaxation of unnecessarily strict training requirements, requiring quality assurance reviews only from affected organizations, and in general simplifying work processes. All members of the YMP received training to the new Orientation class Eleven other training classed were held. Investigators submitted 971 records to the Project and only 37 were rejected. The software program has 115 programs approved for quality-affecting work. The Project Office conducted 3 audits and 1 survey of Los Alamos activities. We conducted 14 audits and 4 surveys. Eight corrective action reports were closed, leaving only one open. Internally, 22 deficiencies were recognized. This is a decrease from 65 in 1991. Since each deficiency requires about 2 man weeks to resolve, the savings are significant. Problems with writing acceptable deficiency reports have essentially disappeared. Trend reports for 1992 were examined and are summarized herein. Three adverse trends have been closed; one remaining adverse trend will be closed when the affected procedures are revised. The number of deficiencies issued to Los Alamos compared to other participants is minimal.
Date: March 1994
Creator: Bolivar, S. L.; Burningham, A. & Chavez, P.
Partner: UNT Libraries Government Documents Department

Los Alamos National Laboratory Yucca Mountain Site Characterization Project 1993 Quality Program status report

Description: This status report is for calendar year 1993. It summarizes the annual activities and accomplishments of the Los Alamos National Laboratory (Los Alamos) Yucca Mountain Site Characterization Project (YMP or Project) quality assurance program. By identifying the accomplishments of the quality program, we establish a baseline that will assist in decision making, improve administrative controls and predictability, and allow us to annually identify long term trends and to evaluate improvements. This is the third annual status report (Bolivar, 1992; Bolivar, 1994). This report is divided into two primary sections: Program Activities and Trend Analysis. Under Program Activities, programmatic issues occurring in 1993 are discussed. The goals for 1993 are also listed, followed by a discussion of their status. Lastly, goals for 1994 are identified. The Trend Analysis section is a summary of 1993 quarterly trend reports and provides a good overview of the quality assurance issues of the Los Alamos YMP.
Date: May 1, 1995
Creator: Bolivar, S.L.
Partner: UNT Libraries Government Documents Department

Los Alamos National Laboratory Yucca Mountain Site Characterization Project 1994 quality program status report

Description: This status report is for calendar year 1994. It summarizes the annual activities and accomplishments of the Los Alamos National Laboratory Yucca Mountain Site Characterization Project (YMP or Project) quality assurance program. By identifying the accomplishments of the quality program, a baseline is established that will assist in decision making, improve administrative controls and predictability, and allow us to annually identify adverse trends and to evaluate improvements. This is the fourth annual status report.
Date: March 1, 1996
Creator: Bolivar, S.L.
Partner: UNT Libraries Government Documents Department