Publications

LLUVIA-II is a program designed for the efficient solution of two- dimensional transient flow of liquid water through partially saturated, porous media. The code solves Richards equation using the method-of-lines procedure. This document describes the solution procedure employed, input data structure, output, and code verification.

Short communication.

A complete edge-weighted directed graph on vertices 1,2,...,n that assigns cost c(i,j) to the edge (i,j) is called Monge if its edge costs form a Monge array, i.e., for all i < k and j < l, c[i, j]+c[k,l]{le} < c[i,l]+c[k,j]. One reason Monge graphs are interesting is that shortest paths can be computed quite quickly in such graphs. In particular, Wilber showed that the shortest path from vertex 1 to vertex n of a Monge graph can be computed in O(n) time, and Aggarwal, Klawe, Moran, Shor, and Wilber showed that the shortest d-edge 1-to-n path (i.e., the shortest path among all 1-to-n paths with exactly d edges) can be computed in O(dn) time. This paper`s contribution is a new algorithm for the latter problem. Assuming 0 {le} c[i,j] {le} U and c[i,j + 1] + c[i + 1,j] {minus} c[i,j] {minus} c[i + 1, j + 1] {ge} L > 0 for all i and j, our algorithm runs in O(n(1 + 1g(U/L))) time. Thus, when d {much_gt} 1 + 1g(U/L), our algorithm represents a significant improvement over Aggarwal et al.`s O(dn)-time algorithm. We also present several applications of our algorithm; they include length-limited Huffman coding, finding the maximum-perimeter d-gon inscribed in a given convex n-gon, and a digital-signal-compression problem.

This report documents the lightning threat warning system at the Tonopah Test Range and the technology it uses. The report outlines each of the system's individual components and the information each contributes.

Three seals constructed of compressed crushed salt blocks have been successfully emplaced vertically down in three 97-cm (38.2-in.) diameter boreholes drilled from the repository horizon of the Waste Isolation Pilot Plant. All three seals are designed to allow fluid flow measurements and two of the seals are heavily instrumented with pressure and hole closure gages. The seals are providing structural and fluid flow data useful for evaluating predictive models and long-term crushed salt seal performance. Results to date, 1100 to 1450 days after seal emplacement, indicate the current average densities of the seals to be about 85% of intact rock salt. Relative densities have increased about 2% since emplacement. The results to date are consistent with previous laboratory and modeling studies of crushed salt behavior. This report provides information necessary for evaluating these data including as-built test configurations, construction histories, and instrumentation descriptions. Seal and instrumentation installation techniques are also described.

The ECM Newsletter is published at Sandia National Laboratories to disseminate information obtained from research and development programs and demonstration, testing, and evaluation projects at research facilities on environmentally conscious manufacturing processes. This issue covers the topics of Life Cycle Assessment, etching processes for Kovar, cleaning of plutonium surfaces, non- chromate conversion coatings for aluminum,, and circuit board manufacturing.

The Mixed-Waste Landfill Integrated Demonstration (MWLID) has been assigned to Sandia National Laboratories (SNL) by the US Department of Energy (DOE) Office of Technology Development. The mission of the MWLID is to assess, implement and transfer technologies and systems that lead to quicker, safer, and more efficient remediation of buried chemical and mixed-waste sites. The MWLID focus is on two landfills at SNL in Albuquerque, New Mexico: The Chemical Waste Landfill (CWL) and the Mixed-Waste Landfill (MWL). These landfills received chemical, radioactive and mixed wastes from various SNL nuclear research programs. A characterization system has been designed for the definition of the extent and concentration of contamination. This system includes historical records, directional drilling, and emplacement membrane, sensors, geophysics, sampling strategy, and on site sample analysis. In the remediation task, in-situ remediation systems are being designed to remove volatile organic compounds (VOC`s) and heavy metals from soils. The VOC remediation includes vacuum extraction with electrical and radio-frequency heating. For heavy metal contamination, electrokinetic processes are being considered. The MWLID utilizes a phased, parallel approach. Initial testing is performed at an uncontaminated site adjacent to the CWL. Once characterization is underway at the CWL, lessons learned can be directly transferred to the more challenging problem of radioactive waste in the MWL. The MWL characterization can proceed in parallel with the remediation work at CWL. The technologies and systems demonstrated in the MWLID are to be evaluated based on their performance and cost in the real remediation environment of the landfills.

The structural, electrical and magnetic properties are compared for three superconducting Tl-Ca-Ba-Cu-O thin films prepared by different deposition and sintering protocols. One film containing a mixture of Tl{sub 2}Ca{sub 2}Ba{sub 2}Cu{sub 3}O{sub x} and Tl{sub 2}Cu{sub 1}Ba{sub 2}Cu{sub 2}O{sub y} structural phases has the best superconducting properties. Deposition of a Tl-free Ca-Ba-Cu-O precursor film followed by sintering in Tl-O vapor may be the preferred protocol to obtain a single structural phase.

Sandia National Laboratories (SNL) designs, tests and operates a variety of accelerators that generate large amounts of high energy Bremsstrahlung radiation over an extended time. Typically groups of similar accelerators are housed in a large building that is inaccessible to the general public. To facilitate independent operation of each accelerator, test cells are constructed around each accelerator to shield it from the radiation workers occupying surrounding test cells and work-areas. These test cells, about 9 ft. high, are constructed of high density concrete block walls that provide direct radiation shielding. Above the target areas (radiation sources), lead or steel plates are used to minimize skyshine radiation. Space, accessibility and cost considerations impose certain restrictions on the design of these test cells. SNL Health Physics division is tasked to evaluate the adequacy of each test cell design and compare resultant dose rates with the design criteria stated in DOE Order 5480.11. In response SNL-Health Physics has undertaken an intensive effort to asses existing radiation shielding codes and compare their predictions against measured dose rates. This paper provides a summary of the effort underway and its results.

Here at Sandia, I design new weapon components using PRO-ENGINEER and find that not only am I responsible for the initial design, but that I must be able to justify that design and show that I have analyzed the design for stress, considering thermal, static, and dynamic conditions. I must be able to create models at a reasonable cost using stereolithography. I must be able to create vivid graphic arts presentations for managements approval, if I want the design to be accepted. I must be able to communicate my design to the production people for comment. These problems, plus others must be done in a timely manner with a minimum of paper involved, and less money than ever before. Therefore, Rapid Prototyping takes on an more important stature than originally proposed, and I would like to show you a rapid prototyping process using PRO-ENGINEER as the fundamental base from which to operate.

A previous paper showed that for condensed phase explosives, the C-J density of the detonation product gases correlates to the initial density of the unreacted explosive by a simple power function. This paper extends that correlation to the very low density region which includes detonation of suspended particles of explosives in air as well as gas phase detonations. Extending this correlation of experimental data by an additional three orders of magnitude caused a slight change in the empirical constants of the correlation.

Short communication.

We have used a combination of methods to probe the structure and kinetics of electron beam induced damage in a monolayer of PF{sub 3} on Ru(001). This is a particularly rich system, in which molecularly adsorbed PF{sub 3} is reduced to PF{sub 2}, PF and P by electron bombardment. The concentrations and kinetics of damage by 550 eV electrons are measured as a function of surface temperature (100 to 300 K) and PF{sub 3} coverage using soft x-ray photoemission spectroscopy (SXPS) excited by synchrotron radiation. Structures of fragments and ion desorption kinetics are measured using electron stimulated desorption ion angular distribution (ESDIAD). Evidence is seen for quenching of Desorption induced by electronic transitions (DIET) processes via intermolecular interactions at high coverages. Damage rates and product distributions vary with temperature, due to a competition between DIET and thermal kinetic processes.

This bulletin presents fabrication methods helpful to industry. This issue contains articles on the use of computers in fast casting, techniques for optimizing encapsulation, high quality electroformed parts, improved welding with detection of contaminants, and special machine guards for enhanced safety. (GHH)

Probabilistic risk assessment 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 of direct containment heating (DCH) that could be used for screening studies aimed at identifying potentially significant contributors to overall risk. The two-cell kinetic model developed here is an extension of the two-cell equilibrium model developed previously, which captured a major mitigating feature due to containment compartmentalization. This extension of the equilibrium model represents additional mitigating features resulting from two kinetic competitions: time-of-flight limitations to debris/gas heat transfer and debris oxidation, and the noncoherence or reactor coolant system blowdown with debris residence in the atmosphere. Predictions of containment pressurization and hydrogen production are compared to experiment data taken in the Surtsey facility located at Sandia National Laboratories.

Epitaxial films of Ba{sub 2}YCu{sub 3}O{sub 7-{delta}} (BYCO) as thin as 250 {Angstrom} and with J{sub c}`s approaching those of the best in situ grown films can be formed by co-evaporating BaF{sub 2}, Y, and Cu followed by a two-stage anneal. High quality films of these thicknesses become possible if low oxygen partial pressure [p(O{sub 2}) = 4.3 Torr] is used during the high temperature portion of the anneal (T{sub a}). The BYCO melt line is the upper limit for T{sub a}. The use of low p(O{sub 2}) shifts the window for stable BYCO film growth to lower temperature, which allows the formation of smooth films with greater microstructural disorder than is found in films grown in p(O{sub 2}) = 740 Torr at higher T{sub a}. The best films annealed in p(O{sub 2}) = 4.3 Torr have J{sub c} values a factor of four higher than do comparable films annealed in p(O{sub 2}) = 740 Torr. The relationship between the T{sub a} required to grow films with the strongest pinning force and p(O{sub 2}) is log [p(O{sub 2})] {proportional_to} T{sub a}{minus}{sup 1a} independent of growth method (in situ or ex situ) over a range of five orders of magnitude of p(O{sub 2}).

We have used 2.0-{mu}sec microwave pulses at a frequency of 2.856 GHz to rapidly heat thin amorphous yttrium-barium-copper-oxide (YBCO) films deposited onto silicon substrates. The samples were irradiated inside a WR-284 waveguide by single-pass TE{sub 10} pulses in a traveling wave geometry. X-ray diffractometry studies show that an amorphous-to-crystalline phase transition occurs for incident pulse powers exceeding about 6 MW, in which case the amorphous YBCO layer is converted to Y{sub 2}BaCuO{sub 5}. Microscopy of the irradiated film reveals that the phase transition is brought about by melting of the YBCO precursor film and crystallization of the molten layer upon solidification. Time-resolved in situ experiments of the microwave reflectivity (R) and transmissivity (T) show that there is an abrupt change in R for microwave pulse powers exceeding the melt threshold, so that measurements of R and T can be used to monitor the onset of surface melting.

This paper reports the phase-one results of a planned longitudinal study of the incidence of entrepreneurship among inventors who were employees of national laboratories. A survey of 192 inventors employed by national laboratories and 24 ex-employee inventors who became entrepreneurs provided data for comparison of situational and attitudinal variables. Significant differences in attitudes (as measured by the Entrepreneurial Attitude Orientation Scale) were found between inventors who have not become entrepreneurs and those who have. The differences in perceptions of situational variables between the two groups was significant for only two of the seven dimensions tested.

In order to resolve questions regarding the source of the extended linear viscosity-concentration regime in rod-like systems the distribution of orientations in confined systems has to be determined and related to changes in viscosity. In this work we describe our experimental and computer simulation studies on systems of neutrally buoyant suspensions of rod-like particles confined by the walls of a cylindrical container.

Recent results from light ion fusion experiments on the Particle Beam Fusion Accelerator (PBFA II) are reported. Intense proton beams have been used to drive two different types of targets. In the thermal source targets, the proton beam heated a low-density foam. The specific power deposition of the proton beam in the foam exceeded 100 TW/gm. In the spherical hydrodynamic targets, the proton beam heated a thin-walled deuterium gas-filled target directly, producing a radial convergence of the deuterium of about 6. In order to increase the specific power deposition in the target, we are developing focused lithium beams. A preformed lithium ion source has been produced using a two-step laser evaporation and ionization approach. This preformed source provides the basis for experiments being planned to reduce the divergence of the lithium beam, a critical step in demonstrating the feasibility of light ion fusion.

The first major round of target experiments driven by intense light ion beams was conducted during August and September 1991. In these experiments, intense proton beams were used to drive two different types of targets. We attempted to obtain information on the two separable issues of ion deposition and implosion hydrodynamics. Ion deposition was studied using a low density hydrocarbon foam contained within a cylindrical gold shell. Implosion hydrodynamics was studied using an ion driven exploding pusher configuration in which the ion beam heated the shell directly, exploding it both outward and inward. One of the main objectives of the experiments was to determine the extent to which we could diagnose the ion deposition and the subsequent behavior of the targets. The diagnostics included time-integrated and time-resolved x-ray pinhole cameras, time-integrated and time-resolved grazing incidence x-ray spectrometers, an 11-channel filtered x-ray diode (XRD) array, an 11-channel PIN diode array, an energy-resolved 1-dimensional imaging x-ray streak camera, a transmission grating spectrometer, an elliptical crystal x-ray spectrograph, and a bolometer. Intense beam diagnostics included an ion movie camera and an off-axis 1D slit imaging magnetic spectrograph for obtaining Rutherford-scattered ion images, momenta, and ion power densities.

The last decade has offered many challenges to the welding metallurgist: new types of materials requiring welded construction, describing the microstructural evolution of traditional materials, and explaining non-equilibrium microstructures arising from rapid thermal cycle weld processing. In this paper, the author will briefly review several advancements made in these areas, often citing specific examples of where new insights were required to describe new observations, and to show how traditional physical metallurgy methods can be used to describe transformation phenomena in advanced, non-traditional materials. The paper will close with comments and suggestions as to the needs required for continued advancement in the field.

An improved technology to extract VOCs from the unsaturated zone has developed into a cooperative Environmental Restoration and Technology Development effort. This cooperation is important because the timing of an innovative technology demonstration is critical to the transfer of that technology into an ER remedial action decision. The Mixed-Waste Landfill Integrated Demonstration (MWLID) Program will be demonstrating a Thermal Enhanced Vapor Extraction System that will improve existing vacuum vapor extraction technology by applying in-situ soil heating. Combined demonstrations of vacuum vapor extraction and both powerline frequency and radiofrequency soil heating technologies began in FY92.

SAFSIM (System Analysis Flow SIMulator) is a FORTRAN computer program that provides engineering simulations of user-specified flow networks at the system level. It includes fluid mechanics, heat transfer, and reactor dynamics capabilities. SAFSIM provides sufficient versatility to allow the simulation of almost any flow system, from a backyard sprinkler system to a clustered nuclear reactor propulsion system. In addition to versatility, speed and robustness are primary goals of SAFSIM. The current capabilities of SAFSIM are summarized, and some illustrative example results are presented.

Lost circulation is the loss of drilling fluid from the wellbore to fractures or pores in the rock formation. In geothermal drilling, lost circulation is often a serious problem that contributes greatly to the cost of the average geothermal well. The Lost Circulation Technology Development Program is sponsored at Sandia National Laboratories by the US Department of Energy. The goal of the program is to reduce lost circulation costs by 30--50% through the development of mitigation and characterization technology. This paper describes the technical progress made in this program during the period April 1991--March 1992. 8 refs.