The objective of this study is to observe changes in coal structure in situ with small angle X-ray scattering (SAXS) during solvent swelling and during pyrolysis. We have built a SAXS instrument at the Basic Energy Sciences Synchrotrons Research Center at the Advanced Photon Source that allows us to obtain scattering patterns in the millisecond time domain. The eight Argonne Premium Coal samples were used in this study. The information that can be derived from these experiments, such as changes in fractal dimensionality and in size and type of porosity, was found to be very rank-dependent. In the swelling experiments, it was noted that for certain coals, structural changes occurred in just a few minutes.

The International Workshop on Cold Moderators for Pulsed Neutron Sources resulted from the coincidence of two forces. Our sponsors in the Materials Sciences Branch of DOE's Office of Energy Research and the community of moderator and neutron facility developers both realized that it was time. The Neutron Sources Working Group of the Megascience Forum of the Organization for Economic Cooperation and Development offered to contribute its support by publishing the proceedings, which with DOE and Argonne sponsorship cemented the initiative. The purposes of the workshop were: to recall and improve the theoretical groundwork of time-dependent neutron thermalization; to pose and examine the needs for and benefits of cold moderators for neutron scattering and other applications of pulsed neutron sources; to summarize experience with pulsed source, cold moderators, their performance, effectiveness, successes, problems and solutions, and the needs for operational data; to compile and evaluate new ideas for cold moderator materials and geometries; to review methods of measuring and characterizing pulsed source cold moderator performance; to appraise methods of calculating needed source characteristics and to evaluate the needs and prospects for improvements; to assess the state of knowledge of data needed for calculating the neutronic and engineering performance of cold moderators; …

While many issues in the area of virtual reality (VR) research have been addressed in recent years, the constant leaps forward in technology continue to push the field forward. VR research no longer is focused only on computer graphics, but instead has become even more interdisciplinary, combining the fields of networking, distributed computing, and even artificial intelligence. In this article we discuss some of the issues associated with distributed, collaborative virtual reality, as well as lessons learned during the development of two distributed virtual reality applications.

The author discusses the properties of classical Coulombic matter at low temperatures. It has been well known for some time [1,2] that infinite Coulombic matter will crystallize in body-centered cubic form when the quantity {Lambda} (the dimensionless ratio of the average two-particle Coulomb energy to the kinetic energy per particle) is larger than {approximately}175. But the systems of such particles that have been produced in the laboratory in ion traps, or ion beams, are finite with surfaces defined by the boundary conditions that have to be satisfied. This results in ion clouds with sharply defined curved surfaces, and interior structures that show up as a set of concentric layers that are parallel to the outer surface. The ordering does not appear to be cubic, but the charges on each shell exhibit a ''hexatic'' pattern of equilateral triangles that is the characteristic of liquid crystals. The curvature of the surfaces prevents the structures on successive shells from interlocking in any simple fashion. This class of structures was first found in simulations [3] and later in experiments [4].

Irradiation hardening is an issue of practical importance as it relates to the remanent life and the nature of failure of reactor components exposed to displacement-producing radiation. For example, irradiation-induced yield strength increases in pressure vessel steels are directly related to increases in the ductile-to-brittle-transition-temperature of these materials. Other issues associated with hardening, such as reductions in ductility, toughness and fatigue life of structural steels are also of concern. Understanding these phenomena requires studies of fundamental microstructural mechanisms of hardening. Because of the limited supply of neutron-irradiated surveillance material, difficulties posed by the radioactivity of neutron-exposed samples and the uncertainty of irradiation conditions in this case, fundamental studies are often conducted using well-controlled experiments involving irradiation by electrons instead of neutrons. Also, in such studies, simple model alloys are used in place of steels to focus on the influence of specific alloy constituents. It is, therefore, important to understand the relationship between the results of this kind of experiment and the effects of in-reactor neutron exposure in order to use them to make predictions of significance to reactor component life. In this paper, we analyze the tensile behavior of pressure vessel steels (A212B and A350) irradiated by neutrons and electrons. …

Strontium isotope studies of carbonates from soils, veins, eolian dust and Paleozoic basement samples near Crater Flat, southwest of Yucca Mountain, provide evidence for the origins of these materials. Vein and soil carbonates have nearly identical ranges of {sup 87}Sr/{sup 86}Sr ratios at the lower end of the pedogenic range. The average {sup 87}Sr/{sup 86}Sr of Paleozoic basement from Black Marble Hill is similar to the {sup 87}Sr/{sup 86}Sr in the eolian dust, perhaps indicating a local source for this material. Possible spring deposits have generally higher {sup 87}Sr/{sup 86}Sr than the other carbonates. These data are compared with similar data from areas east of Yucca Mountain. 7 refs., 5 figs.

Lithologic variation, regional depositional trends, and the lack of written guidelines have resulted in inconsistencies in the recognition of stratigraphic contacts in drill holes at the Nevada Test Site (NTS). Stratigraphic identification, based on mineralogy of discrete samples, can be augmented by geophysical logs and downhole movies to more accurately and consistently locate contacts between units. Criteria are established for locating the base of the Pahute Mesa ash-flow tuff, the top of the Ammonia Tanks ash-flow tuff, the top of the Ammonia Tanks bedded tuff, and the top and the base of the Rainier Mesa Tuff.

The concept of a disturbed zone surrounding the mined openings of a potential geologic repository for high-level radioactive waste was introduced by the US Nuclear Regulatory Commission (NRC) as a region to be excluded for determining groundwater travel time to the accessible environment, but to be included for determining the impact of underground construction and radioactive decay heat on groundwater movement and radionuclide transport for total system performance analysis. This paper explores both the regulatory and technical necessity for characterizing and modeling a larger region -- the altered zone -- within which the temperature is increased significantly by heat from the high-level waste. Particular attention is given to addressing the effects of heterogeneity on groundwater flux and travel time, showing how these effects might be modeled simply on a macroscopic scale, and outlining its parameters. The effect of uncertainty in the parameter values on the performance of a potential repository can then be easily handled by probabilistic analysis.

A two-dimensional time-dependent two-fluid hydrodynamic model has been used to study numerically the effect of interstellar neutrals on the size and structure of the heliosphere. The interstellar neutrals, coupled to the plasma by charge-exchange collisions, lead to a dramatic decrease in the size of the heliosphere -- 30% for the parameters studied. We find that a build up of neutral hydrogen in front of the leading edge of the heliospbere, seen in earlier models, occurs only when the flow in the interstellar medium is supersonic. When the flow is subsonic, no such hydrogen ``wall`` is seen in the simulations, suggesting that the distribution of scattered solar H Ly a light may be quite different for this case. We have also calculated the propagation of an interplanetary shock to the heliopause as a possible trigger for the 1992 Voyager 2--3 kHz radio emission event. We find that the interstellar plasma density, observed emission cut-off frequency, and heliopause location can all b made consistent once the effect of the reduction in the size of the heliosphere by the interaction with the neutrals is included.

The progress of the Reduced Enrichment Research and Test Reactor (RERTR) Program since its inception in 1978 is described. A brief summary of the results which the RERTR Program had achieved by the end of 1996 in collaboration with its many international partners is followed by a detailed review of the major events, findings, and activities of 1997. Significant progress has been made during the past year. In the area of U.S. acceptance of spent fuel from foreign research reactors, several shipments have taken place and additional are being planned. Intense fuel development activities are in progress, including procurement of equipment, screening of candidate materials, and production of microplates. Irradiation of the first series of microplates began in August 1997 in the Advanced Test Reactor, in Idaho. Progress has been made in the Russian RERTR program, which aims to develop and demonstrate within five years the technical means needed to convert Russian-supplied research reactors to LEU fuels. The study of an alternative LEU core for the FRM-II design has been extended to address, with favorable results, controversial performance issues which were raised at last year's meeting. Progress was also made on several aspects of producing molybdenum-99 from fission targets utilizing …

This report is the proceedings of the annual Nuclear Criticality Technology and Safety Project (NCTSP) Workshop held in Monterey, California, on April 16--28, 1993. The NCTSP was sponsored by the Department of Energy and organized by the Los Alamos Critical Experiments Facility. The report is divided into six sections reflecting the sessions outlined on the workshop agenda.

The original version of ASCE Standard 4, ``Seismic Analysis of Safety-Related Nuclear Structures`` was published in September 1986. It is ASCE policy to update its standards on a five year interval and the Working Group on Seismic Analysis of Safety Related Nuclear Structures was reconvened to formulate the revisions. The goal in updating the standard is to make sure that it is still relevant and that it incorporates the state of the practice in seismic engineering or, in some cases, where it has been demonstrated that state-of-the-art improvements need to be made to standard practice; new improvements are included. The contents of the new standard cover the same areas as the original version, with some additions. The contents are as follows: Input - response spectra and time histories; modeling of structures; analysis of structures; soil-structure interaction; input for subsystem analysis; special structures - buried pipes and conduits, earth-retaining walls, above-ground vertical tanks, raceways, and base-isolated structures; and an appendix providing seismic probabilistic risk assessment and margin assessment.

Single fracture measurements are difficult to obtain, but they are the only means we have to observe and study natural fracture morphology. The character of the fracture openings (apertures) is often one of the primary factors controlling fluid flow in the fracture. In particular, the shape, distribution, and connectivity of contact areas and flow channels can affect the relative permeability of wetting and non-wetting fluid phases in unsaturated systems. In this paper we use three methods of fractal analysis (the slit-island, the divider, and the variogram) as well as statistical and geostatistical analysis to characterize the geometry of measured fracture apertures obtained from two different fractured rock specimens from the field. One of these is a granitic fracture (crack) of homogeneous lithology and no displacement, the other is a fracture (fault) obtained from a highly altered fault zone, containing striations and slickensides. We discuss the fractal and geostatistical analysis of these two fractures in the context of what information is most helpful for making predictions about fluid flow in single fractures.

Microearthquakes induced by hydraulic fracturing have been studied by many investigators to characterize fracture systems created by the fracturing process and to better understand the locations of energy resources in the earth`s subsurface. The pattern of the locations often contains a great deal of information about the fracture system stimulated during the hydraulic fracturing. Seismic tomography has found applications in many areas for characterizing the subsurface of the earth. It is well known that fractures in rock influence both the P and S velocities of the rock. The influence of the fractures is a function of the geometry of the fractures, the apertures and number of fractures, and the presence of fluids in the fractures. In addition, the temporal evolution of the created fracture system can be inferred from the temporal changes in seismic velocity and the pattern of microearthquake locations. Seismic tomography has been used to infer the spatial location of a fracture system in a reservoir that was created by hydraulic fracturing.

Much attention has been focused on the hydrologic properties of tuff from the potential nuclear waste repository at Yucca Mountain, Nevada. The successful characterization of the near-field environment of the potential repository depends on the ability to understand and predict the movement of water within the matrix and fractures when the rock mass is heated by nuclear waste. This understanding will come only after many combined laboratory experiments, field tests, and model calculations have been performed. Electrical properties, including electrical resistivity and dielectric permittivity, have been utilized in past studies to infer water content in partially saturated rocks. In this study we determine the electrical properties of Topopah Spring tuff from Yucca Mountain (Area 25), and Area 3, Nevada Test Site (NTS), NV, as a function of water content. These results will be used to (1) study the electrical properties of ted rocks as functions of saturation and water chemistry; (2) relate the observed electrical properties to the distribution of water and to the rnicrogeometry of the rock; and (3) to create a database of electrical resistivity ({rho}) and relative dielectric permittivity ({kappa}{prime}) versus water content (Sw) and temperature for rocks within the potential repository horizon. The database will be …

Packages of high-level waste are to be emplaced in unsaturated tuff at the proposed Yucca Mountain repository. Each cylindrical waste package is separated from surrounding rock by a 2-cm air gap. A possible mechanism for release of radionuclides is the dripping of ground water onto waste packages. Drips are assumed to penetrate cracks in failed container and to dissolve radionuclides as the partly failed container fills and overflows. For this wet-drip scenario, with assumed constant drip rate, we have developed analytical solutions for the time-dependent release rates of radionuclides to the surrounding rock. Release rates have been calculated for key radionuclides. 7 refs., 3 figs.

What is the minimal software infrastructure and what type of conventions are needed to simplify development of sophisticated parallel numerical application codes using a variety of software components that are not necessarily available as source code? We propose an opaque object-based model where the objects are dynamically loadable from the file system or network. The microkernel required to manage such a system needs to include, at most: (1) a few basic services, namely--a mechanism for loading objects at run time via dynamic link libraries, and consistent schemes for error handling and memory management; and (2) selected methods that all objects share, to deal with object life (destruction, reference counting, relationships), and object observation (viewing, profiling, tracing). We are experimenting with these ideas in the context of extensible numerical software within the ALICE (Advanced Large-scale Integrated Computational Environment) project, where we are building the microkernel to manage the interoperability among various tools for large-scale scientific simulations. This paper presents some preliminary observations and conclusions from our work with microkernel design.

Various commercial software packages and customized programs provide the ability to analyze and visualize the geology of Yucca Mountain. Starting with sparse, irregularly spaced data a series of gridded models has been developed representing the thermal/mechanical units within the mountain. Using computer aided design (CAD) software and scientific visualization software, the units can be manipulated, analyzed, and graphically displayed. The outputs are typically gridded terrain models, along with files of three-dimensional coordinates, distances, and other dimensional values. Contour maps, profiles, and shaded surfaces are the output for visualization.

In order to study the performance of the potential Yucca Mountain Nuclear Waste Repository, scientific investigations are being conducted to reduce the uncertainty about process models and system parameters. This paper is intended to demonstrate a method for determining a strategy for the cost effective management of these investigations. It is not meant to be a complete study of all processes and interactions, but does outline a method which can be applied to more in-depth investigations.

We report on the laser performance of a Nd:phosphate glass (Nd:IOG-1) channel waveguide laser fabricated by electric field assisted Ag{sup +} diffusion. Lasing was achieved in two different size channels, 29 x 9 {micro}m{sup 2} and 50 x 9 {micro}m{sup 2}, on a sample of length 8 mm. Slope efficiencies of {approximately} 15% with respect to incident pump power were measured. Losses in the 29 um wide channel were measured to be in the range 0.2--1.1 dB/cm and in the 50 mm channel, 0.2--0.4 dB/cm. The laser spectrum, centered about the emission peak of 1053 nm, was multimode and randomly polarized.

If the strange quark matter hypothesis is true, then a new class of white dwarfs can exist whose nuclear material in their deep interiors can have a density as high as the neutron drip density, a few hundred times the density in maximum-mass white dwarfs and 4 {times} 10{sup 4} the density in dwarfs of typical mass, M {approximately} 0.6M{sub {circle_dot}}. Their masses fall in the approximate range 10{sup {minus}4} to 1M{sub {circle_dot}}. They are stable against acoustical modes of vibration. A strange quark core stabilizes these stars, which otherwise would have central densities that would place them in the unstable region of the sequence between white dwarfs and neutron stars.

Kaon electroproduction on deuterium and hydrogen targets has been measured at beam energies of 3.245 and 2.445 GeV and momentum transfer Q{sup 2}=0.38 and 0.5 GeV{sup 2}. Associated {Lambda} production off a proton in the deuteron exhibits a quasifree production mechanism. The production of {Sigma}{sup {minus}} off the neutron could be extracted for the first time with reasonable errors.

Aircraft and later missile radar early warning stations played an important role in the Cold War. They are associated with important technological, social, political, and military themes of the Cold War and are worthy of preservation. The scope and scale of these systems make physical preservation impractical, but the U.S. Air Force program of historical evaluation and documentation of these systems will provide valuable information to future generations studying this historic period.

The results from the RELAP5/MOD3 and PARET/ANL codes are compared with the SPERT-IV series of experimental reactivity insertion transients. The PARET/ANL code provides conservative estimates of SPERT-IV experimental data for the midrange transients and for the more severe transients. The PARET results are similar to the results obtained earlier for the SPERT-I D-12/25 series of experiments. The RELAP5/MOD3 code (including the developmental version 3.2.1.2) gives results comparable to PARET for some midrange transients, but seriously diverges from the experimental data when significant boiling is present. Based on the results of this study, the use of the RELAP5 code for research reactor applications should be limited to transients that do not generate substantial boiling and voids. We hope to be able to resolve these differences in further work with the NRC staff and its contractors. The RELAP5 code would be a more useful tool for the analyses research reactor transients with the addition of suitable correlations for low pressures and plate type geometry.