The 2-D code MAGIC and TRAJ have been used for extensive studies of diode, IFR channel, and accelerating gap problems in the recirculating linear accelerator (RLA). Typical beam parameters use 10--20 kA, 3--4 MeV. This report summarizes recent results from these simulations. We have also designed possible injectors for the proposed BOLT experiment, with typical beams at 100 A, 1.0--1.5 MeV. Finally, we discuss some preliminary diode runs of proposed 100 MV, 500 kA accelerator using the SMILE/HERMES method of adding voltages from many cavities across a single immersed diode gap. 8 refs.
This report describes the progress of the three-dimensional mesh generation research, using plastering, during the 1990 fiscal year. Plastering is a 3-D extension of the two-dimensional paving technique. The objective is to fill an arbitrary volume with hexahedral elements. The plastering algorithm`s approach to the problem is to remove rows of elements from the exterior of the volume. Elements are removed, one level at a time, until the volume vanishes. Special closure algorithms may be necessary at the center. The report also discusses the common development environment and software management issues. 13 refs.
The AL-SX/2 and AL-SX/3 are recently certified Type B shipping containers for tritium reservoirs. Both containers consist of an outer stainless steel drum overpack and sealed stainless steel containment vessel. WR reservoirs provide containment of tritium for normal conditions of transport. In accident conditions the containment vessel of the AL-SX must contain the tritium. A variety of reservoirs and materials will be packaged inside the containment vessel. These materials must not produce high pressure gas products that exceed the internal pressure capability of the vessel if the container is in an accident involving fire. This report summarizes outgassing tests performed on various organic materials. Tests of commonly used materials show that increased pressure due to outgassing is not a problem at elevated temperatures that simulate an accident. This report summarizes outgassing tests performed on various materials that may be packaged inside the AL-SX during shipment. These materials (except the getter) are normally a part of the reservoir shipping configuration. The objective of the tests was to determine the temperature that these materials begin to generate high pressure gaseous products.
During June and July 1991, the Sandia Transportable Lightning Instrumentation Facility (SATTLIF) was fielded at the Department of Defense (DoD) Security Operations Test Site (SOTS) at Ft. McClellan, Alabama. Nine negative cloud-to-ground lightning flashes were artifically triggered to designated locations on Igloo 2, a weapons storage bunker specially prepared to allow instrumentation access to various of its structural and electrical system elements. Simultaneous measurements of the incident flash currents and responses at 24 test points within the igloo and its grounding counterpoise network were recorded under lightning attachments to the front and rear air terminals of the structure`s lightning protection system. In Volume I the test is described in detail. The measured data are summarized and discussed. Appendix A contains the full set of recorded incident flash currents, while Appendix B presents the set of largest responses measured at each test point, for both front and rear attachments to the structure. As part of these tests, 0.050-in-thick stainless steel, 0.08-in copper, and 0.08-in titanium samples were exposed to triggered flash currents. In this way, damage spots created by direct-strike triggered lightning have been obtained, along with the measurement of the return-stroke and continuing currents that produced them. These data points, along with similar ones on aluminum and ferrous steel obtained during 1990 will be used as benchmarks against which to quantify the fidelity of burnthrough testing achievable Sandia`s advanced laboratory lightning simulator.
A channel ions can focus and guide a relativistic electron beam. This report discuses the generation of plasma channels using magnetically confined low energy electron beams in a low pressure gas. The most significant advantages of these channels are that any gas can be ionized and that they can easily be made to follow a curved path. The major advantages are that the channel is less well confined than a laser produced channel and that a small solenoidal magnetic field is required. This report is intended to be a guide for those technicians and scientists who need to assemble and operate an e-beam generated plasma channel system. Hardware requirements are discussed in detail. There are brief discussions of operating techniques, channel diagnostic, and channel characteristics.
This report contains viewgraphs on topics in the following areas: plasma facing components (PFC) operation in devices; disruption studies; laboratory PFM and high heat flux research; R&D for future machines; and neutron effects on thermonuclear materials.
Data are presented from the 18 W/m{sup 2} Mockup for Defense High-Level Waste, a very large scale in situ test fielded underground at the Waste Isolation Pilot Plant (WIPP). These data include selected fielding information, test configuration, instrumentation activities, and comprehensive results from a large number of gages. The results in this report give measured data from the thermal response gages, i.e., thermocouples, flux meters, and heater power gages emplaced in the test. Construction of the test began in June 1984; gage data in this report cover the complete test duration, that is, to June 1990.
The objective of this project is to apply Sandia`s expertise and technology towards the development of stimulation diagnostic technology in the areas of in situ stress, natural fracturing, stimulation processes and instrumentation systems. Initial work has concentrated on experiment planning for a site where hydraulic fracturing could be evaluated and design models and fracture diagnostics could be validated and improved. Important issues have been defined and new diagnostics, such as inclinometers, identified. In the area of in situ stress, circumferential velocity analysis is proving to be a useful diagnostic for stress orientation. Natural fracture studies of the Frontier formation are progressing; two fracture sets have been found and their relation to tectonic events have been hypothesized. Analyses of stimulation data have been performed for several sites, primarily for in situ stress information. Some new ideas in stimulation diagnostics have been proposed; these ideas may significantly improve fracture diagnostic capabilities.
The Nuclear Waste Repository Technology Department at Sandia National Laboratories (SNL) is investigating the suitability of Yucca Mountain as a potential site for underground burial of nuclear wastes. One element of the investigations is to assess the potential long-term effects of groundwater flow on the integrity of a potential repository. A number of computer codes are being used to model groundwater flow through geologic media in which the potential repository would be located. These codes compute numerical solutions for problems that are usually analytically intractable. Consequently, independent confirmation of the correctness of the solution is often not possible. Code verification is a process that permits the determination of the numerical accuracy of codes by comparing the results of several numerical solutions for the same problem. The international nuclear waste research community uses benchmarking for intercomparisons that partially satisfy the Nuclear Regulatory Commission (NRC) definition of code verification. This report presents the results from the COVE-2A (Code Verification) project, which is a subset of the COVE project.
The Yucca Mountain Site Characterization Project is studying Yucca Mountain in southwestern Nevada as a potential site for a high-level nuclear waste repository. Site characterization includes surface-based and underground testing. Analyses have been performed to design site characterization activities with minimal impact on the ability of the site to isolate waste, and on tests performed as part of the characterization process. One activity of site characterization is the construction of an Exploratory Studies Facility, which may include underground shafts, drifts, and ramps, and the accompanying ponds used for the storage of sewage water and muck water removed from construction operations. The information in this report pertains to the two-dimensional numerical calculations modelling the movement of sewage and settling pond water, and the potential effects of that water on repository performance and underground experiments. This document contains information that has been used in preparing Appendix I of the Exploratory Studies Facility Design Requirements document (ESF DR) for the Yucca Mountain Site Characterization Project.
The Yucca Mountain Site Characterization Project (YMP) is conducting studies to determine whether the Yucca Mountain site in southern Nevada will meet regulatory criteria for a potential mined geologic disposal system for high-level radioactive waste. Data gathered as part of these studies must be compiled and tabulated in a controlled manner for use in design and performance analyses. An integrated data management system has been developed to facilitate this process; this system relies on YMP participants to share in the development of the database and to ensure the integrity of the data. The site and Engineering Properties Database (SEPDB) is unique in that, unlike most databases where one data set is stored for use by one defined user, the SEPDB stores different sets of data which must be structured so that a variety of users can be given access to the information. All individuals responsible for activities supporting the license application should, to the extent possible,work with the same data and the same assumptions. For this reason, it is important that these data sets are readily accessible, comprehensive, and current. The SEPDB contains scientific and engineering data for use in performance assessment and design activities. These data sets currently consist of geologic, hydrologic, and rock properties information from drill holes and field measurements. The users of the SEPDB include engineers and scientists from several government research laboratories (Lawrence Livermore National Laboratory, Los Alamos National Laboratory, and Sandia National Laboratories), the US Geological Survey, and several government contractors. This manuscript describes the detailed requirements, contents, design, and status of the SEPDB, the procedures for submitting data to and/or requesting data from the SEPDB, and a SEPDB data dictionary (Appendix A) for defining the present contents.
Midway Valley, located at the eastern base of Yucca Mountain, Nye County, Nevada, has been identified as a possible location for the surface facilities of a potential high-level nuclear-waste repository. This structural and topographic valley is bounded by two north- trending, down-to-the-west normal faults: the Paintbrush Canyon fault on the east and the Bow Ridge fault on the west. Surface and near-surface geological data have been acquired from Midway Valley during the past three years with particular emphasis on evaluating the existence of Quaternary faults. A detailed (1:6000) surficial geological map has been prepared based on interpretation of new and existing aerial photographs, field mapping, soil pits, and trenches. No evidence was found that would indicate displacement of these surficial deposits along previously unrecognized faults. However, given the low rates of Quaternary faulting and the extensive areas that are covered by late Pleistocene to Holocene deposits south of Sever Wash, Quaternary faulting between known faults cannot be precluded based on surface evidence alone. Middle to late Pleistocene alluvial fan deposits (Unit Q3) exist at or near the surface throughout Midway Valley. Confidence is increased that the potential for surface fault rupture in Midway Valley can be assessed by excavations that expose the deposits and soils associated with Unit Q3 or older units (middle Pleistocene or earlier).
The Choice Coordination Problem with {kappa} alternatives ({kappa}-CCP) was introduced by Rabin in 1982. The goal is to design a wait-free protocol for n asynchronous processes which causes all correct processes to agree on one out of {kappa} possible alternatives. Each of the {kappa} alternatives has an associated shared register and a solution to the {kappa}-CCP requires that a special symbol be written in exactly one shared register. All correct processes must eventually halt with a pointer to the register containing the special symbol. The difficulty arises from the fact that each process may have a different naming convention for the registers. Protocols requiring the least number of symbols are considered optimal. We gave a brief overview of our results in this paper.
This paper presents a methodology for determining the response of spent fuel assembly spacer grids subjected to transport cask impact loading. The spacer grids and their interaction with rod-to-rod loading are the most critical components governing the structural response of spent fuel assemblies. The purpose of calculating the assembly response is to determine the resistance to failure of spent fuel during regulatory transport. The failure frequency computed from these analyses is used in calculating category B spent fuel cask containment source term leakage rates for licensing calculations. Without defensible fuel rod failure frequency prediction calculations, assumptions of 100% fuel failure must be made, leading to leak tight cask design requirements.
The Strategic Defense Initiative Organization (SDIO) decided to investigate the possibility of launching a Russian Topaz 11 space nuclear power system. A preliminary safety assessment was conducted to determine whether or not a space mission could be conducted safely and within budget constraints. As part of this assessment, a safety policy and safety functional requirements were developed to guide both the safely assessment and future Topaz II activities. A review of the Russian flight safety program was conducted and documented. Our preliminary safety assessment included a top level event tree, neutronic analysis of normal and accident configurations, an evaluation of temperature coefficients of reactivity, a reentry and disposal analysis, and analysis of postulated launch abort impact accidents, and an analysis of postulated propellant fire and explosion accidents. Based on the assessment, it appears that it will be possible to safely launch the Topaz II system in the US with some possible system modifications. The principal system modifications will probably include design changes to preclude water flooded criticality and to assure intact reentry.
The US Department of Energy (DOE) has developed a site characterization plan (SCP) to collect detailed information on geology, geohydrology, geochemistry, geoengineering, hydrology, climate, and meteorology (collectively referred to as ``geologic information``) of the Yucca Mountain site. This information will be used to determine if a mined geologic disposal system (MGDS) capable of isolating high-level radioactive waste without adverse effects to public health and safety over 10,000 years, as required by regulations 40 CFR Part 191 and 10 CFR Part 60, could be constructed at the Yucca Mountain site. Forecasts of future climates conditions for the Yucca Mountain area will be based on both empirical and numerical techniques. The empirical modeling is based on the assumption that future climate change will follow past patterns. In this approach, paleclimate records will be analyzed to estimate the nature, timing, and probability of occurrence of certain climate states such as glacials and interglacials over the next 10,000 years. For a given state, key climate parameters such as precipitation and temperature will be assumed to be the same as determined from the paleoclimate data. The numerical approach, which is the primary focus of this paper, involves the numerical solution of basic equations associated with atmospheric motions. This paper describes these equations and the strategy for solving them to predict future climate conditions around Yucca Mountain.
This paper presents an overview of the preclosure seismic hazards and the influence of these hazards on determining the suitability of Yucca Mountain as a national high-level nuclear-waste repository. Geologic data, engineering analyses, and regulatory guidelines must be examined collectively to assess this suitability. An environmental assessment for Yucca Mountain, written in 1986, compiled and evaluated the existing tectonic data and presented arguments to satisfy, in part, the regulatory requirements that must be met if the Yucca Mountain site is to become a national waste repository. Analyses have been performed in the past five years that better quantify the local seismic hazards and the possibility that these hazards could lead to release of radionuclides to the environment. The results from these analyses increase the confidence in the ability of Yucca Mountain and the facilities that may be built there to function satisfactorily in their role as a waste repository. Uncertainties remain, however, primarily in the input parameters and boundary conditions for the models that were used to complete the analyses. These models must be validated and uncertainties reduced before Yucca Mountain can qualify as a viable high-level nuclear waste repository.
The design of cementitious repository seals requires an understanding of cement hydration effects in developing a tight interface zone between the rock and the seal. For this paper, a computer code, SHAFT.SEAL, is used to model early-age cement hydration effects and performs thermal and thermomechanical analysis of cementitious seals. The model is described, and then used to analyze for the effects of seal size, rock temperature and placement temperature. The model results assist in selecting the instrumentation necessary for progressive evaluation of seal components and seal-system tests. Also, the results identify strategies for seal emplacement for a series of repository seal tests for the Yucca Mountain Site Characterization Project (YMP).
Bent-axis maneuvering vehicles provide a unique type of control for a variety of supersonic and hypersonic missions. Unfortunately, large hinge moments, incomplete pitching moment predictions, and a misunderstanding of corresponding center of pressure calculations have prevented their application. A procedure is presented for the efficient design of bent-axis vehicles given an adequate understanding of origins of pitching moment effects. In particular, sources of pitching moment contributions will be described including not only normal force, but inviscid axial force and viscous effects as well. Off-centerline center of pressure effects are first reviewed for symmetric hypersonic sphere-cone configurations. Next the effects of the bent-axis geometry are considered where axial force, acting on the deflected tail section, can generate significant pitching moment components. The unique relationship between hinge moments and pitching moments for the bent-axis class of vehicles is discussed.
As part of the design process for a hypersonic vehicle, it is necessary to predict the aerodynamic and aerothermodynamic environment for flight conditions. This involves combining results obtained from ground testing with analytical modeling to predict the aerodynamics and heating for all conditions of interest. The question which always arises is, how well will these models predict what is actually seen in a flight environment? This paper will briefly address ground-testing and analytical modeling and discuss where each is appropriate, and the associated problems with each area. It will then describe flight test options as well as instrumentation currently available and show how flight tests can be used to validate or improve models. Finally, several results will be shown to indicate areas where ground testing and modeling alone are inadequate to accurately predict hypersonic aerodynamics and aerothermodynamics.
X-ray observations of boiling sodium in a 75-kW{sub t} reflux-pool-boiler solar receiver operating at up to 800{degrees}C were carried out. Both cinematographic and quantitative observations were made. From the cinematography, the pool free surface was observed before and during the start of boiling. During boiling, the free surface rose out of the field of view, and chaotic motion was observed. From the quantitative observations, void fraction in pencil-like probe volumes was inferred, using a linear array of detectors. Useful data were obtained from three of the eight probe volumes. Information from the other volumes was masked by scattered radiation. During boiling, time-averaged void fractions ranged from 0.6 to 0.8. During hot restarts, void fractions near unity occurred and persisted for up to {1/2} second. 17 refs.
Many robot control algorithms for high performance in-contact operations including hybrid force/position, stiffness control and impedance control approaches require the command of the joint torques. However, most commercially available robots do not provide joint torque command capabilities. The joint command at the user level is typically position or velocity and at the control developer level is voltage current, or pulse-width, and the torque generated is a nonlinear function of the command and joint position. To enable the application of high performance in-contact control algorithms to commercially available robots, and thereby facilitate technology transfer from the robot control research community to commercial applications, a practical methodology has been developed to linearize the torque characteristics of electric motor-amplifier combinations. A four degree-of-freedom Adept 2 robot, having pulse-width modulation amplifiers and both variable reluctance and brushless DC motors, is converted to operate from joint torque commands to demonstrate the methodology. The average percentage torque deviation over the command and position ranges is reduced from as much as 76% to below 5% for the direct-drive joints 1, 2 and 4 and is cut by one half in the remaining ball-screw driven joint 3. 16 refs., 16 figs., 2 tabs.
We have obtained dual-longitudinal-mode operation of a Q-switched Nd:YAG laser by simultaneous injection-seeding at two frequencies to produce pulses with modulation frequency discretely tunable from 185 MHz to greater than 17 GHz.