We present results of molecular dynamics computer simulation studies of the threshold energy for point defect production in silicon. We employ computational cells with 8000 atoms at ambient temperature of 10 K that interact via the Stillinger-Weber potential. Our simulations address the orientation dependence of the defect production threshold as well as the structure and stability of the resulting vacancy-interstitial pairs. Near the <111> directions, a vacancy tetrahedral-interstitial pair is produced for 25 eV recoils. However, at 30 eV recoil energy, the resulting interstitial is found to be the <110> split dumbbell configuration. This Frenkel pair configuration is lower in energy than the former by 1.2 eV. Moreover, upon warming of the sample from 10 K the tetrahedral interstitial converts to a <110> split before finally recombining with the vacancy. Along <100> directions, a vacancy-<110> split interstitial configuration is found at the threshold energy of 22 eV. Near <110> directions, a wide variety of closed replacement chains are found to occur for recoil energies up to 45 eV. At 45 eV, the low energy vacancy-<l 10> split configuration is found. At 300 K, the results are similar. We provide details on the atomic structure and relaxations near these defects as …

Research has been directed toward use of economically viable ion processing strategies for production and improvement of hardcoatings. Processing techniques were high-energy ion implantation and electron cyclotron resonance microwave plasma processing. Subject materials were boron suboxides, Ti-6Al-4V alloy, CoCrMo alloy (a Stellite{trademark}), and electroplated Cr. These materials may be regarded either as coatings themselves (which might be deposited by thermal spraying, plasma processing, etc.) or in some cases, as substrates whose surfaces can be improved. hardness and other properties in relation to process variables are reported.

A performance goal-based seismic design philosophy, compatible with DOE`s present natural phenomena hazards mitigation and ``graded approach`` philosophy, has been proposed for high level nuclear waste repository facilities. The rationale, evolution, and the desirable features of this method have been described. Why and how the method should and can be applied to the design of a repository facility are also discussed.

This report discusses development on the technology used to assess the safety of irradiation-embrittled nuclear reactor pressure vessels containing flaws. Fracture mechanics tests on reactor pressure vessel steel have shown that local brittle zones do not significantly degrade the material fracture toughness, constraint relaxation at the crack tip of shallow surface flaws results in increased fracture toughness, and biaxial loading reduces but does not eliminate the shallow-flaw fracture toughness elevation. Experimental irradiation investigations have shown that the irradiation-induced shift in Charpy V-notch versus temperature behavior may not be adequate to conservatively assess fracture toughness shifts due to embrittlement and the wide global variations of initial chemistry and fracture properties of a nominally uniform material within a pressure vessel may confound accurate integrity assessments that require baseline properties.

Results are presented detailing the status of tests of perturbative QCD in hard parton-parton collisions generated by high energy collisions of protons and antiprotons at the Fermilab Collider. Recent data fro the CDF and DO experiments are compared to Next-to-Leading Order QCD calculations in hadronic jet production, prompt photon production, jet production in events with W bosons, and b-quark production.

Deep inelastic polarized lepton-nucleon scattering is reviewed in three lectures. The first lecture covers the polarized deep inelastic scattering formalism and foundational theoretical work. The second lecture describes the nucleon spin structure function experiments that have been performed up through 1993. The third lecture discusses implication of the results and future experiments aimed at high-precision measurements of the nucleon spin structure functions.

Non-metallic oxide inclusions are known to influence the microstructure and properties of low alloy steel weld metal. Therefore, it is desirable to estimate the inclusion characteristics such as size distribution, number density, volume fraction, and composition as a function of welding process and weld composition. Previous work considered a sequential formation of various oxides and compounds to estimate the inclusion characteristics, however, the effect of weld metal composition and weld cooling conditions were not considered. Hence, a model based on ladle metallurgy principles and transformation kinetics involving nucleation and growth has been developed. The inclusion kinetic calculations are coupled with weld pool thermal history to estimate the inclusion characteristics for a given welding process and composition. The calculations based on this model show a complex sequential oxidation of dissolved deoxidizing elements such as Al, Ti, Si and Mn. The calculated inclusion characteristics show a good correlation with the published results.

At LLNL, a highly sensitive neutron counter was developed that can detect and accurately measure the neutrons from small quantities of plutonium or from other low-level neutron sources. This neutron counter was originally designed as a safeguard device to determine the amount of plutonium inside 4-ft {times} 4-ft {times} 7-ft waste shipping containers leaving the plutonium facility. To detect small quantities of plutonium in these waste containers, the sensitivity of a survey instrument would have to be very high and the instrument would require numerous large (and expensive) neutron detector tubes. Because of limited funding, we were able to find an obsolete instrument containing sixteen {sup 3}He tubes; the tubes are 2 in. in diameter and 3 ft long and positioned in two banks of eight. The instrument was modified by adding 1.5 in. of polyethylene in front and 4.5 in. to the back of the tubes to obtain the highest possible sensitivity to fission energy neutrons. Additional strips of polyethylene 0.5 in. thick and 2 in. wide were also placed between the tubes. These thicknesses of polyethylene were determined experimentally to be the optimum thickness for fission neutrons using a {sup 252}Cf source at LLNL calibration facility. The electronic …

The Sanford Linear Collider has operated successfully to produce over 50,000 Z{sup O}{prime}s with polarized electron beams. The asymmetry in the production of Z{sup O}{prime}s with respect to left and right handed electron beams has been measured, and a preliminary result is presented.

The value of power corrections to the integrals of the polarization structure functions of proton and neutron {integral} g1{sub p,n}(x)dx measured by the EMC, SMC, and E142 groups, is determined based on a model which accounts for higher twist terms, has the correct asymptotic behavior at large Q{sup 2} and satisfies the Gerasimov-Drell-Hearn sum rule at Q{sup 2}=0. The contribution of resonances up to W=1.8GeV at Q{sup 2}=0 is taken into account based on the analysis of electroproduction data. It is shown that when taking into account these higher twit terms, the experimental data agree with the Bjorken sum rule and part of the proton spin projection carried by quarks, is consistent with the natural estimate of {approximately}50%.

It is shown, theoretically, that a coupling cavity; namely an rf cavity operating in the TM{sup 210} mode, when inserted in a storage ring will enhance the coupling between longitudinal and transverse degrees of freedom. As a result, it is shown that the demonstrated very effective laser cooling of the longitudinal motion, can now be extended to transverse motion; i.e., employed to cool a beam in all three directions.

The purpose of this paper is to provide an update on what we`ve accomplished and have planned in our plating operation at Lawrence Livermore National Laboratory (LLNL) in the area of waste minimization. Our efforts have included issues other than waste minimization and, therefore, fall under the wider umbrella entitled pollution prevention or environmentally conscious electroplating. Approximately one year has passed since our last report on pollution prevention and since this topic remains a high-effort activity much more has been accomplished. Our efforts to date fall under the first two generation categories of waste reduction. Good housekeeping practices, inventory control, and minor changes in operating practices (first generation) resulted in an impressive amount of waste reduction. In the second generation of waste reduction, current technology, separation technologies, and material substitutions were used to reduce emission and wastes. The third generation of improvements requires significant technological advances in process synthesis and engineering. We are presently starting some projects in this third generation phase and these will be discussed at the end of this paper.

The late stages of char combustion have a special technological significance, as carbon conversions of 99% or greater are typically required for the economic operation of pulverized coal fired boilers. In the present article, two independent optical techniques are used to investigate near-extinction and final burnout phenomenas. Captive particle image sequences, combined with in situ optical measurements on entrained particles, provide dramatic illustration of the asymptotic nature of the char burnout process. Single particle combustion to complete burnout is seen to comprise two distinct stages: (1) a rapid high-temperature combustion stage, consuming about 70% of the char carbon and ending with near-extinction of the heterogeneous reactions due to a loss of global particle reactivity, and (2) a final burnout stage occurring slowly at lower temperatures. For particles containing mineral matter, the second stage can be further subdivided into: (2a) late char combustion, which begins after the near-extinction event, and converts carbon-rich particles to mixed particle types at a lower temperature and a slower rate; and (2b) decarburization of ash -- the removal of residual carbon inclusions from inorganic (ash) frameworks in the very late stages of combustion. This latter process can be extremely slow, requiring over an order of magnitude …

The high cost of optoelectronic (OE) devices is due mainly to the labor-intensive packaging process. Manually pigtailing such devices as single-mode laser diodes and modulators is very time consuming with poor quality control. The Photonics Program and the Engineering Research Division at LLNL are addressing several issues associated with automatically packaging OE devices. A furry automated system must include high-precision fiber alignment, fiber attachment techniques, in-situ quality control, and parts handling and feeding. This paper will present on-going work at LLNL in the areas of automated fiber alignment and fiber attachment. For the fiber alignment, we are building an automated fiber pigtailing machine (AFPM) which combines computer vision and object recognition algorithms with active feedback to perform sub-micron alignments of single-mode fibers to modulators and laser diodes. We expect to perform sub-micron alignments in less than five minutes with this technology. For fiber attachment, we are building various geometries of silicon microbenches which include on-board heaters to solder metal-coated fibers and other components in place; these designs are completely compatible with an automated process of OE packaging. We have manually attached a laser diode, a thermistor, and a thermo-electric heater to one of our microbenches in less than 15 minutes …

The central limit theorem can be applied to a Monte Carlo solution if: The random variable x has a finite mean and a finite variance; and the number N of independent observations grows large. When these two conditions are satisfied, a confidence interval based on the normal distribution with a specified coverage probability can be formed. The first requirement is generally satisfied by the knowledge of the type of Monte Carlo tally being used. The Monte Carlo practitioner has only a limited number of marginally quantifiable methods to assess the fulfillment of the second requirement. Ten new statistical checks have been created and added to MCNP4A to assist with this assessment. The checks examine the mean, relative error, figure of merit, and two new quantities: The relative variance of the variance; the empirical history score probability density function f(x). The two new quantities are described. For the first time, the underlying f(x) for Monte Carlo tallies is calculated for routine inspection and automated analysis. The ten statistical checks are defined, followed by the results from a statistical study on analytic Monte Carlo and other realistic f(x)s to validate their values and uses in MCNP. Passing all 10 checks is a …

The distributions of 14 elements into ten extractants were measured from simulant solutions that represent acidic dissolved sludge and acidified supernate from Hanford HLW Tank 102-SY. The extractants: LIX{sup TM}-26, LIX{sup TM}-54, LIX{sup TM}-84, LIX{sup TM}-1010, Cyanex{sup TM} 272, Cyanex{sup TM} 923, Aliquat{sup TM} 336, DHDECMP, DHDECMP-DIPB, and CMPO-DIPB, were sorbed on porous carbon beads to provide dry-appearing beads that would be suitable for column operations. The selected elements, which represent fission products: Ce, Cs, Sr, Tc, and Y; actinides: U, Pu, and Am; and matrix elements: Cr, Co, Fe, Mn, Zn, and Zr; were traced by radionuclides and measured by gamma spectrometry. Distribution coefficients for each of 280 element/absorber/solution combinations were measured for dynamic contact periods of 30 minutes, 2 hours, and 6 hours to provide sorption kinetics information for the selected elements from these complex media. The resulting 840 measured distribution coefficients are presented.

Several general trends were observed in reactivity patterns of sulfur compounds in macerals. Sulfur is reduced in the asphaltene fraction compared to initial maceral. Aliphatics are removed and polycyclic aromatic compounds are both stable and probably formed under these conditions. Molecules containing two sulfur atoms are formed. The preasphaltenes are now being analyzed by DEIHRMS.

This report describes a new flexible technology which is now available to design sensor and control networks based on a protocol embedded in an intelligent communications processor. The flexibility allows a system designer and/or a technical installer to make appropriate tradeoffs among simplicity, functionality, and cost in the design of network nodes and their installation. This is especially important in designing an installation scenario for the safeguards network. The network technology permits several choices of installations with the same basic node hardware. A pre-installed network offers maximum simplicity and no flexibility since it will operate as programmed during manufacture or the pre-installation setup and checkout. At the other end of the spectrum, a network can be installed using network management software and a computer. The combination of the network management software and computer hardware is generally referred to as a Network Management Tool (NMT). The NMT option offers full flexibility to change the network during or after installation. Different NMT can provide different degrees of complexity depending upon the applications and the amount of changes that need to be made during installation.

The objective of this study was to find a material and configuration that could reliably detect the proper functioning of a current slapper detonator. Because of the small size of the slapper geometry (on the order of a 15 mils), most diagnostic techniques are not suitable. This program has the additional requirement that the device could not use any electrical power or output signals. This required that the diagnostic be completely passive. The paper describes the three facets of the development effort: complete characterization of the slapper using VISAR measurements, selection of the diagnostic material and configuration, and testing of the prototype designs. The VISAR testing required the use of a special optical probe to allow the laser light to reach both bridges of the slapper detonator. Results are given in the form of flyer velocity as a function of the initiating voltage level. The selected diagnostic design functions in a manner similar to a dent block except that the impact of the Kapton disk causes a fracture pattern. A quick visual inspection is all that is needed to determine if the flyer velocity exceeded the threshold value. Sub-threshold velocities produce a substantially different appearance.

Two new codes perform ``bootstrapping`` of either two- or three-dimensional boundary fluxes to a TORT three-dimensional calculation. TORSED couples a DORT RZ calculation to an XYZ TORT. Two methods of directional remapping are available, each less expensive than methods previously available for this work. TORSED is compatible with the discontinuous mesh features of TORT. The second code, TORSET, couples two XYZ TORT problems. The second problem may lie entirely inside the first, or it may touch over only a portion of its surface. TORSET can obtain most of its input data from the primary TORT problem or from an automatic mesh generator. Both codes are available for general use on Cray mainframes and UNIX workstations.

This paper describes an approach for systematic evaluation of management alternatives that are being considered for the treatment, storage, and disposal of transuranic waste (TRUW) at U.S. Department of Energy sites. The approach, which is currently under development, would apply WASTE-MGMT, a database application model developed at Argonne National Laboratory, to estimate projected environmental releases and would evaluate impact measures such as health risk and costs associated with each of the waste management alternatives. The customized application would combine site-specific TRUW inventory and characterization data with treatment and transportation parameters to estimate the quantities and characteristics of the wastes to be treated, emissions of hazardous substances from the treatment facilities, and the quantities and characteristics of the wastes to be shipped between sites. These data would then be used to estimate for several TRUW management scenarios the costs and health risks of constructing and operating the required treatment facilities and of transporting TRUW for treatment and final disposal. Treatment, storage, and disposal of TRUW at DOE sites is composed of many variables and options at each stage. The approach described in this paper would provide for efficient consideration of all of these facets when evaluating potentially feasible TRUW management alternatives. …

The author begins with a brief synopsis about Hamiltonian systems and symplectic maps. A symplectic integrator is a symplectic map {phi}(q,p;t) that systematically approximates the time t flow of a Hamiltonian system. Systematic means: (1) in time step, t, i.e. the error should vanish as some power of the time step, and (2) in order of approximation, i.e. one would like a hierarchy of such {phi} that have errors that vanish as successively higher powers of the time step. At present the authors known two general types of symplectic integrators: (1) implicit integrators that are derived from a generating function or from algebraic conditions on Runge-Kutta schemes, and (2) explicit integrators that are derived from integrable Hamiltonians or from algebraic conditions on Runge-Kutta schemes.

By using radioactive ions from the Holifield Radioactive Ion Beam Facility at Oak Ridge National Laboratory it should be possible to identify many new ground-state proton emitters in the mass region from Sn to Pb. During this production and search process the limits of stability on the proton-rich side of the nuclidic chart will be delineated for a significant fraction of medium-weight elements and our understanding of the proton-emission process will be expanded and improved.

Defense nuclear facilities have operated for forty years with a well-defined mission to produce weapons components for the nation. With the end of the cold war, the facilities` missions have changed to one of decontamination and decommissioning. Off-normal operations and use of new procedures, such as will exist during these activities, have often been among the causal factors in previous criticality accidents at process facilities. This paper explores the similarities in causal factors in previous criticality accidents to the conditions existing in current defense nuclear facilities undergoing the transition to decontamination and decommissioning. Practices to reduce the risk to workers, the public, and the environment are recommended.