Pretest analysis of a heated block test, proposed for the Exploratory Studies Facility at Yucca Mountain, Nevada, was conducted in this investigation. Specifically, the study focuses on the evaluation of the various designs to drill holes and cut slots for the block. The thermal/mechanical analysis was based on the finite element method and a compliant-joint rock-mass constitutive model. Based on the calculated results, relative merits of the various test designs are discussed.
Photovoltaic energy systems have historically been treated as a bulk power generation source for the future. However, utilities and other agencies involved with electrification throughout the world are beginning to find photovoltaics a least-cost option to meet specific loads both for themselves and their customers, in both off-grid and grid-connected applications. These expanding markets offer the potential of hundreds of megawatts of sales in the coming decade, but a strategy addressing both industrial growth and user acceptance is necessary to capitalize on this opportunity. 11 refs.
Phase mixing of transverse oscillations changes the nature of the ion hose instability from an absolute to a convective instability. The stronger the phase mixing, the faster an electron beam reaches equilibrium with the guiding ion channel. This is important for long distance propagation of relativistic electron beams where it is desired that transverse oscillations phase mix within a few betatron wavelengths of injection and subsequently an equilibrium is reached with no further beam emittance growth. In the linear regime phase mixing is well understood and results in asymptotic decay of transverse oscillations as 1/Z{sup 2} for a Gaussian beam and channel system, Z being the axial distance measured in betatron wavelengths. In the nonlinear regime (which is likely mode of propagation for long pulse beams) results of the spread mass model indicate that phase mixing is considerably weaker than in the regime. In this paper we consider this problem of phase mixing in the nonlinear regime. Results of the spread mass model will be shown along with a simple analysis of phase mixing for multiple oscillator models. Particle simulations also indicate that phase mixing is weaker in nonlinear regime than in the linear regime. These results will also be shown. 3 refs., 4 figs.
Photovoltaic (PV) systems are increasing in popularity in the northern latitudes and in the arctic regions in the state of Alaska. This increased interest and the high cost of providing electric power in these remote areas have prompted the Alaska Energy Authority (AEA) to request assistance from the Photovoltaic Design Assistance Center at Sandia National Laboratories. A project to investigate the feasibility of using PV-Diesel hybrid power systems in small villages in Alaska was started in 1989. Data acquisition systems (DAS) were designed and installed in selected villages to obtain resource and load information. The DAS is described and village electrical and resource data are presented. Simulations were run using the collected village data and actual cost data provided by the AEA. Results of the simulations and the economic analysis are presented. 5 refs., 8 figs.
Fabrication of high-efficiency silicon solar cells in an industrial environment requires a different optimization than in a laboratory environment. Strategies are presented for process development of high-efficiency silicon solar cells, with a goal of simplifying technology transfer into an industrial setting. The strategies emphasize the use of statistical experimental design for process optimization, and the use of baseline processes and cells for process monitoring and quality control. 8 refs.
The purpose of this paper is to develop an analytical model to convert ballistic limit curves obtained from flat projectile experiments to ballistic limit curves based on equivalent diameter spheres. Results from a test program involving flat plat projectiles conducted at Sandia National Laboratories are compared against the predicted performance of equivalent spherical projectiles as determined from the Wilkinson and Cour-Palais penetration equations. The developed method demonstrates good correlation of the ballistic limit of the shield concept for the flat plate projectiles to the theoretical ballistic limit for equivalent spheres as predicted by the penetration equations. 3 refs.
PRA studies are being extended to include a wider spectrum of reactor plants than was considered in NUREG-1150. There is a need for computationally simple models for Direct Containment Heating (DCH) that could be used for screening studies aimed at identifying potentially significant contributors to risk. This paper discusses two adiabatic equilibrium models that are candidates for the task. The first, a 1-cell model, places a true upper bound on DCH loads. This upper bound, however, often far exceeds reasonable expectations of containment loads based on best estimate CONTAIN calculations or experiment observations. In this paper, a 2-cell model is developed that largely captures the major mitigating features of containment compartmentalization, thus providing more reasonable estimates of the containment load. Predictions of the equilibrium models are compared with experiment data from the Limited Flight Path (LFP) test series conducted at Sandia National Laboratories.
The CONTAIN code is currently being used to predict containment thermal hydraulic conditions during design basis and severe accidents for advanced light water reactor (ALWR) designs such as the Westinghouse AP600. In the AP600 design, a passive containment cooling system (PCCS) is used for reducing long-term overpressure during accidents. CONTAIN models for heat and mass transfer within the AP600 containment and outer air cooling channel are verified by comparing recent CONTAIN calculations to integral test data obtained by Westinghouse in their PCCS Integral Test Facility. The comparison includes test in which the outer containment wall is both dry and wet, that is, the wet tests involve an evaporative water film that enhances heat transfer as will be the case for AP600. The appropriateness of the heat and mass transfer analogy methodology used in the CONTAIN code is demonstrated. Code model limitations are discussed along with model development plans and applications for AP600.
An additive three step process has been developed for patterned deposition of Cu onto poly(tetrafluoroethylene) (PTFE). The first step involves patterned irradiation with X-rays or electrons which is thought to cross link the PTFE surface; step two involves chemical etching with the result that only the non-irradiated areas are etched; and step three involves selective chemical vapor deposition (CVD) of Cu onto the etched surface at 200 C using (hexafluoroacetylacetonato)Cu(I) trimethylphosphine ((hfac)Cu(PMe{sub 3})). The non-irradiated areas of the surface are covered by a continuous, dense Cu film with X-ray photoelectron spectra show to contain only surface impurities that are easily removed by a short Ar ion sputter. The irradiated areas show the presence of only C and F, characteristic of PTFE.
The first experiment of the Integral Effects Test (IET-1) series was conducted to investigate the effects of high pressure melt ejection (HPME) on direct containment heating (DCH). A 1:10 linear scale model of the Zion reactor pressure vessel (RPV), cavity, instrument tunnel, and subcompartment structures were constructed in the Surtsey Test Facility at Sandia National Laboratories (SNL). The RPV was modelled with a melt generator that consisted of a steel pressure barrier, a cast MgO crucible, and a thin steel inner liner. The melt generator/crucible had a semi-hemispherical bottom head containing a graphite limitor plate with a 3.5 cm exit hole to simulate the ablated hole in the RPV bottom head that would be formed by tube ejection in a severe nuclear power plant (NPP) accident. The reactor cavity model contained 3.48 kg of water with a depth of 0.9 cm that corresponded to condensate levels in the Zion plant. A steam driven iron oxide/aluminum/chromium thermite was used to simulate HPME. A relatively small steam explosion occurred in the cavity during IET-1. Steam blowthrough entrained debris into the Surtsey vessel resulting in a peak pressure increase in Surtsey of 98 kPa. The Surtsey vessel had been previously inerted with N{sub 2}. The total debris mass ejected into the Surtsey vessel was 43 kg. The hydrogen concentration was 3.1 mol.% in the vessel at equilibrium. The concentration measured inside the subcompartment structures immediately following HPME transient was 20.7 mol.% H{sub 2}. 4 refs., 17 figs., 5 tabs.
During the RADLAC II open-air beam propagation experiments this last year three separate optical diagnostics were used. (1) Streak cameras were deployed to measure matched beam radius and centroid versus time. (2) Three gated, intensified TV cameras were used to image the beam from the end of the propagation range. They gave beam radius and centroid for three slices of the beam over a five meter propagation length. (3) Open shutter cameras were developed to give the time-averaged beam position over the entire propagation range. Data from all three diagnostics were digitized, stored in files on a computer, and post-processed to give temporally and spatially resolved beam size and position. These diagnostics used beam induced air-fluorescence as the mechanism to provide a prompt signal representative of the beam current density. Previous experiments and analysis have shown that the radiation is prompt with the intensity proportional to the beam current density for high energy, high current electron beams propagating in full density air.
The technical issues brought about by recent federal mandates are reviewed and discussed. Progress made in the elimination of CFCs is briefly reviewed. The problems, implications, and status of pending anti-lead legislation and taxation are discussed at length. Recommendations are made for the enactment of rational, fair, and orderly legislation and taxation.
This paper describes current research and development on a miniaturized sensing system for use during in situ characterization of nuclear waste storage tanks. Sandia is designing this sensing system as a tool for a large robotic arm that is deployed through an access port in the top of a storage tank. While the robot arm scans the sensing package over the waste, a distributed computing system acquires sensor data, correlates the data with the position of the robot, and produces maps of the chemical and radiological contents of the tanks in real time. We have built and demonstrated a first prototype system containing eight sensors. 53 refs.
Two revisions of the CONTAIN code, CONTAIN 1.11 and 1.12 , have recently been released. The purpose of this paper is to highlight the new features of these revisions and to discuss other new code features currently under development. The features of CONTAIN 1.11 discussed here include a quasi-mechanistic concrete outgassing model, the connected structure option for heat conduction between compartments, and a new approach for modeling forced convective heat transfer. The direct containment heating (DCH) models released as part of CONTAIN 1.12 are also discussed. New code features currently under development include a revised gas combustion model and a new multifield DCH model. New features of the revised combustion model include the treatment of spontaneous recombination and diffusion flames. CONTAIN plant calculations comparing the old and the revised combustion models are presented. The new features of the multifield DCH model are discussed, and demonstration calculations using this model to analyze a small scale experiment are presented.
The Department of Energy`s (DOE`s) Office of Civilian Radioactive Waste Management (OCRWM) is in the process of developing a new generation of casks to transport spent fuel from commercial nuclear reactor facilities to federal waste facilities. In evaluating the needs of the cask development program a number of unresolved technical issues with potential impacts on the transportation system were identified. This paper provides three samples of issues being addressed by the Cask Systems Development Program for technical resolution: (1) burn-up credit, (2) containment source term evaluation, and (3) weeping.
SMILE is a coaxial Self Magnetically Insulated Transmission Line voltage adder. It replaces the original beam line of the RADLAC II accelerator by a 12.5 m long cathode electrode. The anode electrode remains practically the same, consisting of the original eight insulating stacks or feeds which are connected with equal diameter stainless steel cylinders. The beam is produced at the end of the accelerator and is free of all the possible instabilities associated with accelerating gaps and magnetic vacuum transport. Annular beams with {beta}{perpendicular} {le} 0.1 and radius r{sub b} {le} 1 cm were routinely obtained and extracted from a small magnetically-immersed foilless electron diode. Results of the experimental evaluation are presented and compared with design parameters and numerical simulation predictions. 4 refs.
In this paper, measurements on the quasi-isentropic compression of tungsten to stress levels of 250 GPa are reported. Results of these experiments have been compared to those obtained under shock loading conditions to comparable stresses. These experiments have allowed the determination of temperature, pressure, and loading rate effects on the dynamic yield strength of tungsten up to 250 GPa. These results show that the dynamic yield strength of tungsten is dependent on the loading rate with the strength being higher for the relatively slower rates of loading along the quasi-isentropic. The pressure dependence of the yield strength of tungsten is determined nearly independent of temperature effects from quasi-isentropic loading experiments to 250 GPa, because the temperature rise in an quasi-loading experiment is much lower than those associated with shock loading experiments.
Continuum dynamics codes are categorized as Lagrangian or Eulerian according to the motion of the mesh. A Lagrangian code`s mesh moves with the material, so no mass flows between cells. An Eulerian code`s mesh is stationary, so mass flows between the cells. Eulerian codes have improved to the point where they are routinely used to solve a broad variety of large deformation solid and fluid dynamics problems ranging from air flow over an airplane wing to meteor impact on space structures. This presentation will concentrate on multi-fluid Eulerian codes capable of modeling transient were propagation in solids. These codes use a two-step process to integrate the physics across a time step. The first step, referred to as the Lagrangian step, integrates the physics on a Lagrangian mesh across the time step. The field values are then at the new time, but they are on the distorted Lagrangian mesh. The second step, referred to as the remap step, remaps the data on the distorted Lagrangian mesh back to the original Eulerian mesh thus completing one time step. The algorithms used in the first step are similar to those used in modern Lagrangian codes but they must be extended to handle multi-material cells. The algorithms used in the second step are complex and must be very carefully chosen to minimize errors. These algorithms include second-order, monotone advection equations to calculate the quantities flowing between cells. They also require algorithms that construct material interfaces inside multi-material cells. The strength and limitations of currently used numerical techniques will be discussed. New code development activities that combine the best features on both Lagrangian and Elueian codes will also be discussed. These new codes will employ the strengths of both technologies to address problems that cannot be adequately solved at this time.
The Hybrid Thin-Slot Algorithm (HTSA) integrates a transient integral-equation solution for an aperture in an infinite plane into a finite-difference time-domain (FDTD) code. The technique was introduced for linear apertures and was extended to include wall loss and lossy internal gaskets. A general implementation for arbitrary thin slots is briefly described here. The 3-D FDTD-code TSAR was selected for the implementation. The HTSA does not provide universal solutions to the narrow slot problem, but has merits appropriate for particular applications. The HTSA is restricted to planar slots, but can solve the important case that both the width and depth of the slot are narrow compared to the FDTD spatial cell. IN addition, the HTSA is not bound to the FDTD discrete spatial and time increments, and therefore, high-resolution solutions for the slot physics are possible. The implementation of the HTSA into TSAR is based upon a ``slot data file`` that includes the cell indices where the desired slots are exist within the FDTD mesh. For an HTSA-defined slot, the wall region local to the slot is shorted, and therefore, to change the slot`s topology simply requires altering the file to include the desired cells. 7 refs.
The one-electron energy levels of icosahedral boron clusters have been calculated as a function of intericosahedral spacing maintaining the intraicosahedral spacing of {alpha}-boron. For crystalline lattice constants greater than 1.25 times the equilibrium one, band overlap occurs with concomitant metallic behavior. At smaller lattice constants, orbitals(bands) associated with bonds to adjacent icosahedra are lowered and orbitals(bands) associated with ``antibonds`` are raised. Four bands which were three quarters full become empty, while three bands which were empty become filled. This leads to an energy gap between the filled states and the empty states which accounts for the experimentally observed insulating behavior of this elemental material with three valence electrons per atom.
Verifying the velocity accuracy of a GPS receiver or an integrated GPS/INS system in a dynamic environment is a difficult proposition when many of the commonly used reference systems have velocity uncertainities of the same order of magnitude or greater than the GPS system. The results of flight tests aboard an aircraft in which multiple reference systems simultaneously collected data to evaluate the accuracy of an integrated GPS/INS system are reported. Emphasis is placed on obtaining high accuracy estimates of the velocity error of the integrated system in order to verify that velocity accuracy is maintained during both linear and circular trajectories. Three different reference systems operating in parallel during flight tests are used to independently determine the position and velocity of an aircraft in flight. They are a transponder/interrogator ranging system, a laser tracker, and GPS carrier phase processing. Results obtained from these reference systems are compared against each other and against an integrated real time differential based GPS/INS system to arrive at a set of conclusions about the accuracy of the integrated system.
Computer-aided molecular design methods were used to tailor binding sites for small substrate molecules, including CO{sub 2} and methane. The goal is to design a cavity, adjacent to a catalytic metal center, into which the substrate will selectively bind through only non-bonding interactions with the groups lining the binding pocket. Porphyrins are used as a basic molecular structure, with various substituents added to construct the binding pocket. The conformations of these highly-substituted porphyrins are predicted using molecular mechanics calculations with a force field that gives accurate predictions for metalloporhyrins. Dynamics and energy-minimization calculations of substrate molecules bound to the cavity indicate high substrate binding affinity. The size, shape and charge-distribution of groups surrounding the cavity provide molecular selectivity. Specifically, calculated binding energies of methane, benzene, dichloromethane, CO{sub 2} and chloroform vary by about 10 kcal/mol for metal octaethyl-tetraphenylporphyrins (OETPPs) with chloroform, dichloromethane, and CO{sub 2} having the lowest. Significantly, a solvent molecule is found in the cavity in the X-ray structures of Co- and CuOETPP crystals obtained from dichloromethane. 5 refs., 3 figs., 3 tabs.
Single Event Upset Imaging utilizes the scanning of a micro-focused MeV ion beams across an integrated circuit to test the upset response of the circuit to energetic heavy ions. Using this technique, the position dependence of logic state upsets, as well as the charge collection efficiency of an integrated circuit, can be directly measured with micron resolution. We present in this paper a review of a series of measurements carried out on the TA670 16K static random access memory chip which display this technique`s capabilities.
