Molecular dynamics is employed to study the low energy states of a beam of charged particles subject to circumferentially varying guiding and focusing forces and with Coulomb forces between the particles. In a constant gradient ring, the lowest energy state is never ordered, but in an alternating gradient structure, operating below the transition energy, the lowest state is ordered. The nature and characteristics of the ground state depends upon the beam density and the ring parameters. For zero temperature the crystal remains intact for a very long time, but at nonzero temperatures it gains energy from the lattice. A critical temperature exists above which the crystal melts rapidly.

Compositions of coexisting liquid and vapor phases have been determined at temperatures from 250 to 350{degree}C for brines containing NaCl and either HCl or NaOH by direct sampling of both phases from a static phase-equilibration apparatus. Thermodynamic partitioning constants for NaCl have been determined from the observed compositions of the coexisting phases combined with the known activity coefficients of NaCl(aq) in the liquid phase. An apparent dependence of the values of these partitioning constants on brine concentration is explained by considering the effect of decreasing pressure on the density of the vapor phase. Concentrations of HCl and NaCl in steam produced from various natural brines may be calculated as functions of temperature and brine composition based on these new results coupled with our previous determinations of the partitioning constants for HCl(aq). Application of these results to The Geysers will be discussed in terms of the composition of postulated brines which could be in equilibrium with observed steam compositions at various temperatures.

In 1991, the NRC, Division of Industrial and Medical Nuclear Safety, began a program to evaluate the use of probabilistic risk assessment (PRA) in regulating medical devices. This program represents an initial step in an overall plant to evaluate the use of PRA in regulating the use of nuclear by-product materials. The NRC envisioned that the use of risk analysis techniques could assist staff in ensuring that the regulatory approach was standardized, understandable, and effective. Traditional methods of assessing risk in nuclear power plants may be inappropriate to use in assessing the use of by-product devices. The approaches used in assessing nuclear reactor risks are equipment-oriented. Secondary attention is paid to the human component, for the most part after critical system failure events have been identified. This paper describes the risk methodology developed by Lawrence Livermore National Laboratory (LLNL), initially intended to assess risks associated with the use of the Gamma Knife, a gamma stereotactic radiosurgical device. For relatively new medical devices such as the Gamma Knife, the challenge is to perform a risk analysis with very little quantitative data but with an important human factor component. The method described below provides a basic approach for identifying the most likely …

A mobile robot is being developed by the Savannah River Technology Center (SRTC) Robotics Group of Westinghouse Savannah River company (WSRC) to perform mandated inspections of waste drums stored in warehouse facilities. The system will reduce personnel exposure and create accurate, high quality documentation to ensure regulatory compliance. Development work is being coordinated among several DOE, academic and commercial entities in accordance with DOE`s technology transfer initiative. The prototype system was demonstrated in November of 1993. A system is now being developed for field trails at the Fernald site.

We develop, analyze, and test a new acceleration scheme for neutron transport methods, the Adjacent-cell Preconditioner (AP) that is particularly suited for solving optically thick problems. Our method goes beyond Diffusion Synthetic Acceleration (DSA) methods in that it`s spectral radius vanishes with increasing cell thickness. In particular, for the ID case the AP method converges immediately, i.e. in one iteration, to 10{sup {minus}4} pointwise relative criterion in problems with dominant cell size of 10 mfp or thicker. Also the AP has a simple formalism and is cell-centered hence, multidimensional and high order extensions are easier to develop, and more efficient to implement.

Vibration tests of elbows to failure were performed in Japan in the early 1970s. The piping system included two elbows and an eccentric mass. Tests were run both pressurized and unpressurized. This report documents a static analysis of the piping system in which the elbows are subjected to out of plane bending. The effects of internal pressure and material plasticity are investigated.

Rapidly changing world events, the increased number of nations with inter-continental ballistic missile capability, and the proliferation of nuclear weapon technology will increase the number of nuclear threats facing the world today. Monitoring these nation`s activities and providing an early warning and/or intercept system via reconnaissance and surveillance satellites and space based weapon platforms is a viable deterrent against a surprise nuclear attack. However, the deployment of satellite and weapon platform assets in space will subject the sensitive electronic equipment to a variety of natural and man-made radiation environments. These include Van Allen Belt protons and electrons; galactic and solar flare protons; and, neutrons, gamma rays, and X-rays from intentionally detonated fission and fusion weapons. In this paper, the MASH vl.0 code system is used to estimate the dose to the critical electronics components of an idealized space based weapon platform from neutron and gamma-ray radiation emitted from a thermonuclear weapon detonation in space. Fluence and dose assessments were performed for the platform fully loaded, and in several stages representing limited engagement scenarios. The results indicate vulnerabilities to the Command, Control, and Communication (C) bay instruments from radiation damage for a nuclear weapon detonation for certain source/platform orientations. The distance …

D&D of the process facilities at the gaseous diffusion plants (GDPs) will be an enormous task. The EBASCO estimate places the cost of D&D of the GDP at the K-25 Site at approximately $7.5 billion. Of this sum, nearly $4 billion is associated with the construction and operation of decontamination facilities and the dismantlement and transport of contaminated process equipment to these facilities. In situ long-term low-temperature (LTLT) gas phase decontamination is being developed and demonstrated at the K-25 site as a technology that has the potential to substantially lower these costs while reducing criticality and safeguards concerns and worker exposure to hazardous and radioactive materials. The objective of gas phase decontamination is to employ a gaseous reagent to fluorinate nonvolatile uranium deposits to form volatile LJF6, which can be recovered by chemical trapping or freezing. The LTLT process permits the decontamination of the inside of gas-tight GDP process equipment at room temperature by substituting a long exposure to subatmospheric C1F for higher reaction rates at higher temperatures. This paper outlines the concept for applying LTLT gas phase decontamination, reports encouraging laboratory experiments, and presents the status of the design of a prototype mobile system. Plans for demonstrating the LTLT …

APEX -- the ATLAS Positron Experiment -- is designed to measure electrons and positrons emitted in heavy-ion collisions. Its scientific goal is to gain insight into the puzzling positron-line phenomena observed at the GSI Darmstadt. It is in operation at the ATLAS accelerator at Argonne National Lab. The assembly of the apparatus is finished and beginning 1993 the first positrons produced in heavy-ion collisions were observed. The first full scale experiment was carried out in December 1993, and the data are currently being analyzed. In this paper, the principles of operation are explained and a status report on the experiment is given.

In many physical problems stimulated Brillouin scattering (SBS) and selffocusing are manifested simultaneously. We consider effect of the stimulated Brillouin backscattering (SBS) on self-focusing of laser radiation in plasmas. It was found that the self-focusing may be supressed substantionally by the SBS effect.

Scenario developments is part of the iterative performance assessment (PA) process for the Waste Isolation Pilot Plant (WIPP). Scenario development for the WIPP has been the subject of intense external review, and is certain to be the subject of continued scrutiny as the project proceeds toward regulatory compliance. The principal means of increasing confidence is this aspect of the PA will be through the use of a systematic and thorough procedure toward developing the scenarios and conceptual models on which the assessment is to be based. Early and ongoing interaction with project reviewers can assist with confidence building. Quality of argument and clarity of presentation in PA will be of key concern. Appropriate tools are required for documenting and tracking assumptions, through a single assessment phase, and between iterative assessment phases. Risks associated with future human actions are of particular concern to the WIPP project, and international consensus on the principles for incorporation of future human actions in assessments would be valuable.

We have measured many peak-to-total gamma-ray detection ratios for germanium detectors, and have correlated the observed values with various parameters, such as gamma-ray energy, detector size, source-to-detector distance, and shielding. We have also observed an unexpected, pronounced, positive slope in the peak-to-total curve in the low-energy region of p-type detectors. To explain this observation, we have evidence that the ``dead`` layer is not completely dead but is capable of producing degraded pulses that contribute to the continuum of a spectrum.

The method of dynamic programming is applied to three example problems dealing with robot trajectory planning. The first two examples involve end-effector tracking of a straight line with rest-to-rest motions of planar two-link and three-link rigid robots. These examples illustrate the usefulness of the method for producing smooth trajectories either in the presence or absence of joint redundancies. The last example demonstrates the use of the method for rest-to-rest maneuvers of a single-link manipulator with a flexible payload. Simulation results for this example display interesting symmetries that are characteristic of such maneuvers. Details concerning the implementation and computational aspects of the method are discussed.

Numerical and experimental results are presented to illustrate some hydrodynamic effects of heat release in premixed flames. The heat release is represented by a simple model which treats the flame front as a two dimensional line source of volume. The velocity and strain rate induced in the flow field are determined and the numerical solution for the case of a laminar double kernel ignition is obtained. Of primary interest is the strain induced in the reactants between the expanding flame kernels and, for heat release rates typical of hydrocarbon flames, the strain rate at the plane of symmetry midway between the kernels up to 150 s{sup {minus}1}. The effects of kernel size, density ratio across the flame front and laminar burning velocity are studied. For the case of turbulent combustion the velocity induced in the reactant stream is measured in a plane parallel to the flame holder of an open premixed turbulent V-shaped flame. A divergent flow field, with a strain rate of 50 s{sup {minus}1}, is induced by the heat release in the flame zone and the consequences of this for determining the turbulent burning velocity in this and similar systems is reviewed.

Eigenvalues and two-dimensional fission rate distributions computed with the CASMO-3G lattice physics code and the VIM Monte Carlo Code are compared. The cases assessed are two advanced commercial BWR pin bundle designs. Generally, the two codes show good agreement in K{sub inf}, fission rate distributions, and control rod worths.

In this paper, we present a new discrete formulation that maintains discrete invariance and is suitable for use on nonorthogonal meshes. This formulation, unlike its predecessors, allows us to easily use adaptive mesh refinement to concentrate grid points where error contributions are large (near vortex centers). In this way we reduce the total number of grid points required to accurately capture vortex configurations and allow the possibility of solving problems previously considered intractable. To solve these large problems, we require the memory capabilities and computational power of state-of-the-art parallel computers. To use these machines, we have developed scalable libraries for adaptive mesh refinement and partitioning on two-dimensional triangular grids. This general-purpose software uses bisection of the longest side to refine triangles in which error contributions are large. These adaptive meshes are both unstructured and dynamic, and we present a new geometric partitioning, algorithm that strives to minimize communication cost by ensuring good partition aspect ratios. We present computational results showing the efficiency of these adaptive techniques for a superconductivity application.

Maximum entropy (Gull and Skilling, IEE Proceedings, 131F, 646 (1984)) is an image processing routine based on Bauesian probability which can produce a ``most likely`` image from original data given a particular point spread function. By combining maximum entropy and analysis with incoherent Z-contrast imaging, it is possible to retrieve crystal lattice information at atomic resolution from directly acquired experimental data without the need for preconceived structures. Results are given for simulated and experimentally acquired Z-contrast images of semiconductors (graded SiGe, <110> Si, <110> GaAs) at 300 kV.

The US Department of Energy`s Uranium Mill Tailings Remedial Action (UMTRA) Project requires that mill tailings, containing low-level radioactive uranium mill tailings and other waste, be stabilized and controlled by placement in an encapsulated disposal cell. The cover of the cell is a multi-layer system which includes a low-permeability earthen radon/infiltration barrier, a bedding layer, and a erosion protection layer. The radon/infiltration barrier is designed to limit the radon flux and reduce water infiltration. The performance criteria established by the US Environmental Protection Agency in 40 CFR 192 require the cover to be effective for up to 1000 years to the extent reasonably achievable, and in any case, for at least 200 years. One concern that would affect the integrity of the radon/infiltration barrier is the potential for cracking due to the post-construction settlement of underlying compressible materials. To investigate the potential of cover cracking for UMTRA disposal cells, a simplified beam analysis is used to determine the horizontal movements and strains due to the differential settlements at the top surface of a relatively incompressible layer (e.g. radon/infiltration barrier and compacted tailings). The potential of cover cracking is then evaluated by comparing the calculated horizontal tensile strains with the strains …

A simple method to estimate the threshold-voltage shift in MOSFETs due to low-dose-rate ionizing irradiation based on MIL-STD-883D Method 1019.4 is demonstrated. The realm of applicability of this approach is explored.

As part of the regulatory development process, the US Envirorunental Protection Agency (EPA) collects data, makes various assumptions about the data, and analyzes the data. Although EPA acts in good faith, the agency cannot always be aware of all relevant data, make only appropriate assumptions, and use applicable analytical methods. Regulated industries must carefully must carefully review every component of the regulatory decision-making process to identify misunderstandings and errors and to supply additional data that is relevant to the regulatory action. This paper examines three examples of how EPA`s data, assumptions, and analytical methods have been critiqued. The first two examples involve EPA`s cost-effectiveness (CE) analyses prepared for the offshore oil and gas effluent limitations guidelines and as part of EPA Region 6`s general permit for coastal waters of Texas and Louisiana. A CE analysis regulations to the incremental amount of pollutants that would be removed by the recommended treatment processes. The third example, although not involving a CE analysis, demonstrates how the use of non-representative data can influence the outcome of an analysis.

Analyses have performed on the severe accident response of four 90 MWth reactor cores, all designed using the metallic fuel of the Integrated Fast Reactor (IFR) concept. The four core designs have different sodium void worth, in the range of {minus}3$ to 5$. The purpose of the investigation is to determine the improvement in safety, as measured by the severe accident consequences, that can be achieved from a reduction in the sodium void worth for reactor cores designed using the IFR concept.

Cleanup of hazardous waste sites under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) is a complicated and painstaking process, particularly at facilities with a multitude of individual hazardous waste sites, each having a multitude of chemicals and radonuclides. The US Department of Energy-Oak Ridge, Environmental Restoration Division (DOE-OR/ERD) administers five such facilities which are undergoing environmental cleanup under the CERCLA Remedial Investigation and Feasibility Study (RI/FS) process or the Resource Conservation and Recovery Act (RCRA) investigation process. The nature of the wastes treated, stored, or disposed of at the US DOE-OR sites is heterogeneous and often unknown. The amount of environmental sampling, chemical analysis, and document preparation and review required to support a baseline risk assessment alone at each facility often requires years before arriving at a final Record of Decision. Therefore, there is clearly a need to streamline the investigative and decision processes in order to realize the US Environmental Protection Agency`s (EPA) goal of reducing contaminant levels to those that are protective human health and the environment in a timely and cost-effective manner.

Vibrational predissociation of XI{sub 2} and X{sub 2}I{sub 2} van der Waals complexes, with X = He and Ne, is studied with wave packets. Three-dimensional calculations are carried out on the three-atom systems. Suitable X{center_dot}{center_dot}I potential interactions are determined, and product distributions are predicted. Reduced dimension models of X{sub 2}I{sub 2}(v{prime}) {yields} 2X + I{sub 2}(v < v{prime}) are investigated. Comparison is made with available experimental results. Mechanistic issues, including the role of intramolecular vibrational relaxation resonances, are addressed.

A precise measurement of the left-right cross section asymmetry (A{sub LR}) for Z boson production by e{sup +}e{sup {minus}} collisions has been attained at the Slac Linear Collider with the SLD detector. We describe this measurement for the 1993 data run, emphasizing the significant improvements in polarized beam operation which took place for this run, where the luminosity-weighted electron beam polarization averaged 62.6 {plus_minus} 1.2 %. Preliminary 1993 results for A{sub LR} are presented. When combined with the (less precise) 1992 result, the preliminary result for the effective weak mixing angle is sin{sup 2} {theta}{sub W {sup eff}} = 0.2290 {plus_minus} 0.0010.