Nuclear criticality parameters were developed as a basis for evaluating criticality safety for waste stored in the high-level waste tank farms on the Hanford Site in Washington State. The plutonium critical concentration and critical mass were calculated using a conservative waste model (CWM). The primary requirement of a CWM is that it have a lower neutron absorption than any actual waste. Graphs are provided of the critical mass as a function of plutonium concentration for spheres and for uniform slab layers in a 22.9-m-diameter tank. Minimum subcritical absorber-to-plutonium mass rates were calculated for waste components selected for their relative abundance and neutron absorption capacity. Comparison of measured absorber-to-plutonium mass ratios in their corresponding subcritical limit mass ratios provides a means of assessing whether criticality is possible for waste of the measured composition. A comparison is made between the plutonium critical concentrations in CWM solids and in a postulated real waste. This comparison shows that the actual critical parameters are likely to be significantly larger than those obtained using the CWM, thus providing confidence that the margin of safety obtained to the criticality safety evaluation is conservative.

A news article from the Washington Post discussing the difficulties of finding a vaccine to stop HIV transmission and recent tests that are leading researchers to be hopeful about a possible vaccine.

A news article from AIDS Weekly Plus covering researchers' gathering at the ninth Annual Meeting of the National Cooperative Vaccine Development Groups for AIDS (NCVDG) to discuss a new strategy to pursue an effective vaccine for HIV.

A news article covering the ninth Annual Meeting of the National Cooperative Vaccine Development Groups for AIDS (NCVDG) and the contributions David Baltimore is making to AIDS research and HIV vaccine development.

A news article from the Washington Post discussing Bill Clinton's recent commencement address that he used as a platform to urge the scientific community to find a vaccine to prevent the transmission of HIV/AIDS.

We show that an effective field theory that includes non-standard couplings between the electroweak gauge bosons and the top and bottom quarks may yield negative contributions to both the S and T oblique radiative electroweak parameters. We find that such an effective field theory provides a better fit to data than the standard model (the {chi}{sup 2} per degree of freedom is half as large). We examine in some detail an illustrative model where the exchange of heavy scalars produces the correct type of non-standard couplings.

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Crystals of Yb{sup 3+}:Sr{sub 1-x}Ba{sub x}(PO{sub 4}){sub 3}F (0 < x < 5) have been investigated as a means to obtain broader absorption bands than are currently available with Yb{sup 3+}:S-FAP [Yb{sup 3+}: Sr{sub 5}(PO{sub 4}){sub 3}F], thereby improving diode-pumping efficiency for high peak power applications. Large diode-arrays have a FWHM pump band of >5 nm while the FWHM of the 900 nm absorption band for Yb:S-FAP is 5.5 nm; therefore, a significant amount of pump power can be wasted due to the nonideal overlap. Spectroscopic analysis of Yb:Sr{sub 5-x}Ba{sub x}-FAP crystals indicates that adding barium to the lattice increases the pump band to 13-16 run which more than compensates for the diode-array pump source without a detrimental reduction in absorption cross section. However, the emission cross section decreases by approximately half with relatively no effect on the emission lifetime. The small signal gain has also been measured and compared to the parent material Yb:S-FAP and emission cross sections have been determined by the method of reciprocity, the Filchtbauer-Ladenburg method, and small signal gain. Overall, Yb{sup 3+}:Sr{sub 5-x}Ba{sub x}(PO{sub 4}){sub 3}F crystals appear to achieve the goal of nearly matching the favorable thermal and laser performance properties of Yb:S-FAP while …

An article titled "Chinese officials to visit UNT art seminar" about visiting delegations from the People's Republic of China to the University of North Texas June 23-24 to learn about the North Texas Institute for Educators on the Visual Arts program to improve public school learning on the arts. They are going to be touring the Sid Richardson Collection, the Kimbell Art Museum and the Amon Center Carter Museum with R. William McCarter, NTIEVA Co-director and Regent Professor of art at UNT.

Using an end-pumped technology developed at LLNL we have demonstrated a Yb:YAG laser capable of delivering up to 434 W of CW power and 226 W of Q-switched power. In addition, we have frequency doubled the output to 515 nm using a dual crystal scheme to produce 76 W at 10 kHz in a 30 ns pulse length.

Much has been written about the deterrence strategies that justified the arms race. Walter Slocombe explained that {open_quotes}[t]he dominant problem of U.S. nuclear strategy is credibly using U.S. nuclear power to deter and if necessary resist nonnuclear as well as nuclear threats to America`s allies, forces, and interests overseas.{close_quotes} As a result, the {open_quotes}flexible response{close_quotes} doctrine was developed to declare {open_quotes}that the United States, in consultation with its allies, is prepared to use nuclear weapons should other means of protection from Soviet attack threaten to fail.{close_quotes} In contrast, Freeman Dyson pointed out the Soviet Union was committed to the concept of {open_quotes}counterforce,{close_quotes} which meant that {open_quotes}if the Soviet Union sees a nuclear attack coming or has reason to believe that an attack is about to be launched, the Soviet Union will strike first at the attacker`s weapons with all available forces, and will then do whatever is necessary in order to survive.{close_quotes} Out of these military postures a tense peace ironically emerged, but the terms by which decisions were made about controlling weapons of mass destruction (i.e., nuclear, chemical, and biological weapons) were the terms of war. The thesis of this paper is that the end of the Cold War …

The traditional method for plutonium density determination is by measuring the weight loss of the component when it is immersed in a liquid of known density, Archimedes` Principle. The most commonly used heavy liquids that are compatible for plutonium measurement are freon and monobromobenzene, but these pose serious environmental and health hazards. The contaminated liquid is also a radiological waste concern with difficult disposition. A gaseous medium would eliminate these environmental and health concerns. A collaborative research effort between the Savannah River Technology Center and Los Alamos National Laboratory was undertaken to determine the feasibility of a gaseous density measurement process for plutonium hemishells.

This paper is an overview of the low-level radioactive waste management practices and treatment systems at Argonne National Laboratory - East (ANL-E). It addresses the systems, processes, types of waste treated, and the status and performance of the systems. ANL-E is a Department of Energy laboratory that is engaged in a variety of research projects, some of which generate radioactive waste, in addition a significant amount of radioactive waste remains from previous projects and decontamination and decommissioning of facilities where this work was performed.

High power laser diodes at various wavelengths are described. First, performance and reliability of an optimized large transverse mode diode structure at 808 and 941 nm are presented. Next, data are presented on a 9.5 kW peak power array at 900 nm having a narrow emission bandwidth suitable for pumping Yb:S-FAP laser materials. Finally, results on a fiber-coupled laser diode array at {approx}730 nm are presented.

Calculated excitation functions are provided for all proton-induced reactions listed for the Coordinated Research Program (CRP) on Development of a Reference Charge Particle Cross Section Data Base for Medical Radioisotope Production under the IAEA. The excitation functions are compared with experimental data sets as provided to the CRP. We discuss the merit of calculated results with respect to the experimental data.

Environmental accounting represents a major paradigm shift in the way most companies account for costs and benefits. However, it is a change that must be made if pollution prevention is to become institutionalized into the corporate and government mainstream. Pollution prevention investments must be justified on an economic basis; without environmental accounting tools, pollution prevention investments cannot show their true profitability. This is because traditional accounting methods only track billable costs, thus ignoring some of the major benefits of pollution prevention investments, which are indirect savings resulting from a lessening of a company`s regulatory compliance burden and present and future liabilities. This paper discusses how to apply environmental accounting principles to pollution prevention assessments to improve the outcome of profitability analyses.

Twenty one hundred metric tons of spent nuclear fuel (SNF) are currently stored in the Hanford Site K Basins near the Columbia River. The deteriorating conditions of the fuel and the basins provide engineering and management challenges to assure safe current and future storage. DE and S Hanford, Inc., part of the Fluor Daniel Hanford, Inc. lead team on the Project Hanford Management Contract, is constructing facilities and systems to move the fuel from current pool storage to a dry interim storage facility away from the Columbia River, and to treat and dispose of K Basins sludge, debris and water. The process starts in K Basins where fuel elements will be removed from existing canisters, washed, and separated from sludge and scrap fuel pieces. Fuel elements will be placed in baskets and loaded into Multi-Canister Overpacks (MCOs) and into transportation casks. The MCO and cask will be transported to the Cold Vacuum Drying Facility, where free water within the MCO will be removed under vacuum at slightly elevated temperatures. The MCOs will be sealed and transported via the transport cask to the Canister Storage Building.

R2BaNiO5 (R = rare earth) quasi-1-D antiferromagnets are structurally equivalent to the well-studied 1-D S = 1 Haldane-gap compound Y2BaNiO5. Unlike the Y-nickelate though, these materials undergo 3-D magnetic ordering at finite temperatures. Recent inelastic neutron scattering studies of Pr2BaNiO5 and (Nd(x)Y(1-x))2BaNiO5 revealed purely one-dimensional gap excitations that propagate exclusively on the Ni-chains and are strikingly similar to Haldane gap modes in Y2BaNiO5. In the ordered phase these excitations survive and actually coexist with conventional spin waves. The results suggest that the Haldane singlet ground state of the Ni-chains is not fully destroyed by Neel ordering.

A three-dimensional world model is crucial for many robotic tasks. Modeling techniques tend to be either fully manual or autonomous. Manual methods are extremely time consuming but also highly accurate and flexible. Autonomous techniques are fast but inflexible and, with real-world data, often inaccurate. The method presented in this paper combines the two, yielding a highly efficient, flexible, and accurate mapping tool. The segmentation and modeling algorithms that compose the method are specifically designed for industrial environments, and are described in detail. A mapping system based on these algorithms has been designed. It enables a human supervisor to quickly construct a fully defined world model from unfiltered and unsegmented real-world range imagery. Examples of how industrial scenes are modeled with the mapping system are provided.

The chemistry of uranium and plutonium in conjunction with the storage, retrieval and treatment of high-level nuclear waste (HLW) has been the subject of increasing scrutiny due to concerns with nuclear criticality safety. Previous studies focused on determining the solubilities of plutonium and uranium in alkaline salt solutions that encompass the compositions present during storage and evaporation of fresh and aged. Recent studies extend the chemistry to include the effects of coprecipitation on the liquid phase concentrations of plutonium and uranium. Particle size, morphology and identification of crystalline phases in the precipitated solids as well as the plutonium and uranium dissolution characteristics upon dilution of the liquid phases were also determined.

Some code improvements have been made during the course of this study. One immediately obvious need was for more flexibility in the constitutive representation for materials in shell elements. To remedy this situation, a model with a tabular representation of stress versus strain and rate dependent effects was implemented. This was required in order to obtain reasonable results in the IED cylinder simulation. Another deficiency was in the ability to extract and plot variables associated with shell elements. The pipe whip analysis required the development of a scheme to tally and plot time dependent shell quantities such as stresses and strains. This capability had previously existed only for solid elements. Work was initiated to provide the same range of plotting capability for structural elements that exist with the DYNA3D/TAURUS tools. One of the characteristics of these problems is the disparity in zoning required in the vicinity of the charge and bubble compared to that needed in the far field. This disparity can cause the equipotential relaxation logic to provide a less than optimal solution. Various approaches were utilized to bias the relaxation to obtain more optimal meshing during relaxation. Extensions of these techniques have been developed to provide more powerful …

Interim and long-term storage of carefully prepared plutonium material within hermetically sealed containers may generate dangerous gas pressures and compositions. The authors have been investigating the application of acoustic resonance spectroscopy to non-intrusively monitor changes in these parameters within sealed containers. In this approach a drum-like gas cavity is formed within the storage container which is excited using a piezoelectric transducer mounted on the outside of the container. The frequency response spectrum contains a series of peaks whose positions and widths are determined by the composition of the gas and the geometry of the cylindrical resonator; the intensities are related to the gas pressure. Comparing observed gas frequencies with theory gives excellent agreement. Small changes in gas composition, better than 1:1000, are readily measurable.

Over the past several years, Congress has directed the Department of Energy (DOE), the Nuclear Regulatory Commission (NRC), and the Environmental Protection Agency (EPA) to abandon their efforts to assess an array of potential candidate geologic repository sites for the permanent disposal of spent nuclear reactor fuel and high level radioactive waste, to develop generally applicable requirements for licensing geologic repositories, and to develop generally applicable radiation protection standards for geologic repositories, and instead to focus their efforts to determine whether a single site located at Yucca Mountain, Nevada can be developed as a geologic repository which providing reasonable assurance that public health and safety and the environment will be adequately protected. If the Yucca Mountain site is found to be suitable for development as a geologic repository, then at each stage of development DOE will have to provide the NRC with progressively more detailed information regarding repository design and long-term performance. NRC regulations reflect the fact that it will not be until the repository has been operated for a number of years that the NRC will be able to make a final determination as to long-term repository performance. Nevertheless, the NRC will be able to allow DOE to construct …