The characterization of unknown mixed wastes is a mandatory step in today`s climate of strict environmental regulations. Cleaning up the nuclear and chemical wastes that have accumulated for 50 years at the Hanford Site is the largest single cleanup task in the United States today. The wastes are stored temporarily in carbon steel single- and double-shell tanks that are buried in tank farms at the Site. In the 1950s, a process to scavenge radioactive cesium and other soluble radionuclides in the wastes was developed to create additional tank space for waste storage. This scavenging process involved treatment of the wastes with alkali cyanoferrates and nickel sulfate to precipitate {sup 137}Cs in the presence of nitrate oxidant. Recent safety issues have focused on the stability of cyanoferrate-bearing wastes with large quantities of nitrates and nitrites. Nitrate has been partially converted to nitrite as a result of radiolysis during more than 35 years of storage. The major safety issue is the possibility of the presence of local hot spots enriched in {sup 137}Cs and {sup 90}Sr that under optimum conditions can self-heat causing dry out and a potential runaway reaction of the cyanoferrates with the nitrates/nitrites). For waste tank safety, accurate data …

We report on the absorption of laser energy that results when an ultra-intense laser pulse is incident onto a sharp vacuum-plasma boundary, where the initial shelf density of the plasma is much greater than the critical density, n{sub cr}. It is found that 2-D effects greatly increase the amount of absorption into hot electrons, over the amount predicted using 1-D theory. In particular, a scaling for the absorption as a function of density, for a fixed laser intensity, implies that the absorption will be of order 30% for densities well in excess of The interaction is studied using both 1- and 2- dimensional particle-in-cell (PIC) 100 n{sub cr} simulations. The 1-D results agree quite well with a simple scaling of JxB heating, where the laser electric field penetrates a skin depth into the overdense plasma and subsequently heats electrons. In 2-D, when the laser is incident at an angle, the absorption is seen to increase substantially due to a form of resonant absorption that occurs in steep density profiles. We find that the inclusion of kinetic and multi-dimensional effects are crucial to obtaining a complete picture of the interaction. The ability of ultra-intense lasers to produce acceptable amounts o f …

Relatively low resistivity (200 to 1000 {Omega}-cm) starting silicon materials have been studied in the search of room temperature neutron radiation-hard silicon detectors. It has been found that, moderate resistivity (300-700 {Omega}-cm) silicon detectors, after being irradiated to 5.0 {times} 10{sup 13} to 2.0 {times} 10{sup 14} n/cm{sup 2}, are extremely stable in terms of the detector full depletion voltage (V{sub d}) or the net effective concentration of ionized space charges (N{sub eff} ---- there is little ``reverse annealing`` of N{sub eff} at RT and elevated temperatures as compared with large reverse annealing observed for high resistivity silicon detectors. Detectors with starting resistivity of 300-700 {Omega}-cm have been found to be stable, during the equivalent of one year RT anneal that would reach the saturation of the first stage of reverse anneal, within then N{sub eff} window of {vert_bar}N{sub eff}{vert_bar}{le} 2.5 {times} 10{sup 12} cm{sup {minus}3} (V{sub d} = 180 V for d = 300 {mu}m) in a working range of 5.0 {times} 10{sup 13} to 1.5 {times} 10{sup 14} n/cm{sup 2}, or a net neutron radiation tolerance of 1.0 {times} 10{sup 14} n/cm{sup 2}. The observed effects are in very good agreement with an early proposed model, which predicted …

A parallel job consists of sets of concurrent and sequential tasks. Often the tasks compute sets of values that are reduced to a single value or gathered to build an aggregate structure. Since reductions may introduced dependencies, most languages separate computation and reduction. For example, Fortran 90 and HPF provide a rich set of predefined reduction functions, but only for extant arrays. Sisal 1.2 is unique in that reduction is a natural consequence of loop expressions. Unfortunately, the language supports only seven reduction operations. In this paper, the authors present compilation techniques that recognize pairs of for expressions in Sisal 1.2 as computation-reduction expressions. The techniques work without any language or intermediate form extensions; however, they recognize only certain forms. They describe how they implement pairs of computation-reduction expressions as single parallel loops, and they present performance numbers that demonstrate the utility of their techniques.

A program has been designed to support the prediction of cement degradation and the chemistry of water in contact with cement, over extended periods of time (e.g., 10,000 y). This multidisciplinary experimental and computer modeling investigation is intended to characterize the structural and thermodynamic properties of crystalline phases found in cement at elevated temperature. Many of these crystalline phases my be hydrated. The hydration state of these phases must be known to the interpret experimentally obtained thermodynamic data, to evaluate the stability of hydrated phases and to estimate long-term water availability, such as would be required for prediction of the radioactive-waste repository`s lifetime. The parts of the program associated with assessing and predicting dehydration/ rehydration behavior are described in this paper. (1) identification of phases present in standardized grout mixtures exposed to elevated temperatures; (2) mechanistic and thermodynamic analysis of the hydration/ dehydration behavior of hydrated calcium silicates as a function of temperature, pressure, and relative humidity; and (3) measurements of thermodynamic data for hydrated calcium silicates.

Approximately 800 hectares on the US Department of Energy Nevada Test Site and vicinity are contaminated with Plutonium. As part of a cleanup effort, both the vegetation and the top 5--10 cm of soil may be removed. A study was developed to determine the effects of topsoil removal on seedling emergence and plant species diversity. Trial plots were prepared by removing 5, 10, or 20 cm of topsoil, seeding a mix of nine native species, mulching with straw, and then anchoring the straw with erosion netting. Additional plots (0 topsoil removal treatment) were lightly bladed to remove existing vegetation and then treated as above. Approximately 85 mm of supplemental irrigation was applied to help initiate germination during early spring. Seedling density data of seeded and nonseeded species was collected following emergence, and species diversity was calculated with the Shannon diversity index for the nonseeded species. Densities of seeded species either were unaffected by or increased with increased depth of topsoil removal. In general, densities of nonseeded species decreased with increased depth of topsoil removal. The number of species, species diversity and evenness also decreased with increased depth of topsoil removal. Initial emergence of seeded species is apparently unaffected by topsoil …

This report contains information about a meeting held to discuss the decontamination and decommissioning of the Fernald site in Ohio. This site contains two major types of waste. First is the legacy waste. This waste consists of the wastes which were left over from production which is stored in various drums and containers across the site. Second is the waste generated from the remedial activities.

Measurements and calculations of the inverse bremsstrahlung absorption of intense microwaves are presented. The isotropic component of the electron distribution becomes flat-topped in agreement with detailed Fokker-Planck calculations. The plasma heating is reduced due to the flat-topped distributions in agreement with calculations. The calculations show that the heat flux at high microwave powers is very large, q{sub max} {approx} 0.3 n{sub e}v{sub e}T{sub e}. A new particle model to, calculate the heat transport inhibition due to ion acoustic turbulence in ICF plasmas is also presented. One-dimensional PIC calculations of ion acoustic turbulence excited due to heat transport are presented. The 2-D PIC code is presently being used to perform calculations of heat flux inhibition due to ion acoustic turbulence.

The trapping of both non-equilibrium electrons and holes by neutron induced deep levels in high resistivity silicon planar detectors have been observed. In the experiments Transient Current and Charge Techniques, with short laser light pulse excitation have been applied at temperature ranges of 77--300 k. Light pulse illumination of the front (p{sup +}) and back (n{sup +}) contacts of the detectors showed effective trapping and detrapping, especially for electrons. At temperatures lower than 150 k, the detrapping becomes non-efficient, and the additional negative charge of trapped electrons in the space charge region (SCR) of the detectors leads to dramatic transformations of the electric field due to the distortion of the effective space charge concentration N{sub eff}. The current and charge pulses transformation data can be explained in terms of extraction of electric field to the central part of the detector from the regions near both contacts. The initial field distribution may be recovered immediately by dropping reverse bias, which injects both electrons and holes into the space charge region. In the paper, the degree of the N{sub eff} distortions among various detectors irradiated by different neutron fluences are compared.

The Department of Energy (DOE) has more than 2.5 million tons of radioactive scrap metal (RSM) that is either in inventory or expected to be generated over the next 25 years as major facilities within the weapons complex are decommissioned. Much of this material cannot be surface decontaminated. In an attempt to conserve natural resources and to avoid burial of this material at DOE disposal sites, options are now being explored to {open_quotes}beneficially reuse{close_quotes} this material in applications where small amounts of radioactivity are not a detriment. One example is where RSM is currently being beneficially used to fabricate shield blocks for use in DOE medium energy physics programs. This paper describes other initiatives now underway within DOE to utilize RSM to fabricate other products, such as radioactive waste shipping, storage and disposal containers.

The climate modeling community has focused recently on improving our understanding of certain processes, such as cloud feedbacks and ocean circulation, that are deemed critical to climate-change prediction. Although attention to such processes is warranted, emphasis on these areas has diminished a general appreciation of the role played by the large-scale dynamics of the extratropical atmosphere. Lack of interest in extratropical dynamics may reflect the assumption that these dynamical processes are a non-problem as far as climate modeling is concerned, since general circulation models (GCMs) calculate motions on this scale from first principles. Nevertheless, serious shortcomings in our ability to understand and simulate large-scale dynamics exist. Partly due to a paucity of standard GCM diagnostic calculations of large-scale motions and their transports of heat, momentum, potential vorticity, and moisture, a comprehensive understanding of the role of large-scale dynamics in GCM climate simulations has not been developed. Uncertainties remain in our understanding and simulation of large-scale extratropical dynamics and their interaction with other climatic processes, such as cloud feedbacks, large-scale ocean circulation, moist convection, air-sea interaction and land-surface processes. To address some of these issues, the 17th Stanstead Seminar was convened at Bishop`s University in Lennoxville, Quebec. The purpose of the …

The Hanford Site in eastern Washington state currently is engaged in the largest waste cleanup in world history. In order to make informed decisions about remediation options, the public throughout the Pacific Northwest and the nation needs to understand the wastes that are present, their sources of generation, their composition, and their behavior in the environment. The fact that Hanford operations` were conducted in secret for over four decades presents a unique public information challenge to those who currently are responsible for communicating with the public.

Approximately 800 hectares on the US Department of Energy Nevada Test Site and vicinity are contaminated with plutonium. As part of a cleanup effort, both the indigenous vegetation and the top 5--10 cm of soil may be removed, and the soil may or may not be replaced. Technologies must be developed to stabilize and revegetate these lands. A study was developed to determine adaptable plant species, methods to prepare seedbeds for direct seeding and water harvesting, and proper irrigation rates. Plots were cleared of indigenous vegetation, and then prepared with various seedbed/water harvesting treatments including, pitting, land imprinting, and mulching. Other plots were treated with large water harvesting structures. Three irrigation treatments were superimposed over the seedbed/water harvesting treatments. Seedling emergence data was collected, and the treatment combinations compared. Supporting meteorological and soil data were collected with an automatic data-logger. Specific data included precipitation, and air temperature. In a year of above-average precipitation, irrigation did not generally aid germination and emergence of seeded species, and only slightly increased densities of species from the native seedbank. With the exception of increased shrub seedling densities in desert strips, there were no strong seedbed preparation/water harvesting treatment effects. In years of above-average rainfall, …

We show how polarization-independent wavelength filters can be realized using asymmetric directional couplers. Simulations demonstrate that excellent polarization behavior can be achieved with practical tolerances without sacrificing filter bandwidth or insertion loss.

Experiments on DIII-D (and other tokamaks) have shown that improved performance can follow from optimization of the current density profile. Increased confinement of energy and a higher limit on beta have both been found in discharges in which the current density profile is modified through transient means, such as ramping of current or elongation. Peaking of the current distribution to obtain discharges with high internal inductance {ell}{sub i} has been found to be beneficial. Alternatively, discharges with broader profiles, as in the VH-mode or with high beta poloidal, have shown improved performance. Noninductive current drive is a means to access these modes of improved confinement on a steady state basis. Accordingly, experiments on noninductive current drive are underway on the DIII-D tokamak using fast waves, electron cyclotron waves. Recent experiments on fast wave current drive have demonstrated the ability to drive up to 180 kA of noninductive current using 1.5 MW of power at 60 MHz, including the contribution from 1 MW of ECCD and the bootstrap current. Higher power rf current drive systems are needed to strongly affect the current profile on DIII-D. An upgrade to the FWCD system is underway to increase the total power to 6 MW, …

Although complementary for the development of complex systems, top-down structured design and object oriented approach are still opposed and not integrated. As the complexity of the systems are still growing, and the so-called software crisis still not solved, it is urgent to provide a framework mixing the two paradigms. This paper presents an elegant attempt in this direction through our Recursive Object-Oriented Method (ROOM) in which a top-down approach divides the complexity of the system and an object oriented method studies a given level of abstraction. Illustrating this recursive schema with a simple example, we demonstrate that we achieve the goal of creating loosely coupled and reusable components.

In order to understand the high {Tc} materials, conventional superconductors and their metallic normal states are examined to see how generalizations of BCS pairing may lead to unconventional properties. The persistence of gap-like features in the normal state up to temperatures several times {Tc} is pointed out. The short coherence length and normal state pseudo-gaps are suggestive of preformed pairs which Bose condense at the superconducting transitions; the normal state is a degenerate Fermi system in which correlations lead to pseudo-gaps. It is argued that these deviations from Fermi liquid behavior are characteristic of the normal state of short coherence length superconductors.

On May 17, 1991, the US Department of Energy (DOE) issued a directive for DOE operations to cease off-site shipments of non-radioactive hazardous waste pending further clarification and approvals. A DOE Performance Objective for Certification of Non-Radioactive Hazardous Waste was issued in November 1991. In response to these directives, the Waste Management Division of Oak Ridge Y-12 Plant, with assistance from Roy F. Weston, Inc., has developed a No Rad-Added Program to provide small programmatic guidance and a set of procedures, approved by DOE, which will permit hazardous waste to be shipped from the Y-12 Plant to commercial treatment, storage, or disposal facilities after ensuring and certifying that hazardous waste has no radioactivity added as a result of DOE operations. There are serious legal and financial consequences of shipping waste containing radioactivity to an off-site facility not licensed to receive radioactive materials. Therefore, this program is designed with well-defined responsibilities and stringent documentation requirements.

Extended x-ray absorption fine structure (EXAFS) show local structural anomalies in Tl{sub 2}Ba{sub 2}CuO{sub 6}, which reduce the crystal symmetry; this symmetry lowering is interpreted as an indication of the existence of localized states. A local structural model consistent with the EXAFS results consists of a fraction of the O(1) sites displaced from the midpoint of the Cu-Cu bond, and dimpling of the CuO{sub 2} planes when the O(1) site is not displaced from this midpoint.

The performance of the Ni/NiCl{sub 2} positive electrode for the Na/NiCl{sub 2} battery has been significantly improved compared to that of our earlier electrodes, representative for 1990. This improvement has been achieved by lowering the impedance and increasing the usable capacity through the use of chemical additives and a tailored electrode morphology. The improved electrode has excellent performance even at 250{degrees}C and can be recharged within one hour. The performance of this new electrode was measured by the conventional interrupted galvanostatic method and under simulated driving profiles. These measurements were used to project the performance of 40- to 60-kWh batteries built with this new electrode combined with the already highly developed sodium/{beta}{double_prime}-alumina negative electrode. These calculated results yielded a specific power of 150--400 W/kg and a specific energy of 110--200 Wh/kg for batteries with single-tube and bipolar cell designs. This high performance, along with the high cell voltage, mid-temperature operation, fast recharge capability, and short-circuited failure mode of the electrode couple, makes the Na/NiCl{sub 2} battery attractive for electric vehicle applications.

The transient charge technique (TChT) has been used in this work to study the electrical properties in both space charge region (SCR) and electrical neutral bulk (ENB) of neutron irradiated high resistivity (4--6 k{Omega}-cm) silicon particle detectors. Detectors irradiated to various neutron fluences were measured by TChT at various biases and temperatures below the room temperature. The Fermi level, obtained from the Arrhenius plot of the time constant of the slow component of the charge shape, has been found to stabilize around E{sub c}-0.47 to 0.50 eV at high fluences ({Phi}n>10{sup 13} n/cm{sup 2}). The resistivity of the ENB has been found greater than 300 k{Omega}-cm at high fluences.

Regular hard disk backups for workstations are widely recommended. The necessity of backups -- akin to one`s own mortality -- is something most people would rather not think about. This attitude has two consequences. When people do subscribe to automated network backups, they expect the system to perform at a high level of reliability and that their files will be there for them when they need them. Second, they usually fail to appreciate that reliability is a shared responsibility. Although ostensibly their only responsibility is to keep the computer powered on overnight, there are actually many more opportunities for failure within the user`s jurisdiction than in other parts of the infrastructure. High reliability is almost a sine qua non for backups. We describe a strategy for enhancing reliability based on the principle of accountability. This strategy involves monitoring the system, gathering statistics, detecting problems, anticipating problems, troubleshooting, and finally determining where failure occurred within the infrastructure and who should be accountable. We describe a specific backup system in a specific network environment to illustrate the value of accountability. This system, macdumps, backs up Macintosh disks over an AppleTalk network. The original software was written by Dan Tappan of BBN in …

The ENDF/B-VI photon interaction library includes data for the elements hydrogen (Z=1) through fermium (Z=100) over the energy range 10 eV to 100 MeV. This library contains data to meet the needs of traditional photon transport methods. However, this library also contains data that can be used to perform much more detailed transport calculations. This paper describes the contents of this library and how it can be used for both traditional and more detailed transport calculations.

Smart card systems are most cost efficient when implemented as a distributed system, which is a system without central host interaction or a local database of card numbers for verifying transaction approval. A distributed system, as such, presents special card and user authentication problems. Fortunately, smart cards offer processing capabilities that provide solutions to authentication problems, provided the system is designed with proper data integrity measures. Smart card systems maintain data integrity through a security design that controls data sources and limits data changes. A good security design is usually a result of a system analysis that provides a thorough understanding of the application needs. Once designers understand the application, they may specify authentication techniques that mitigate the risk of system compromise or failure. Current authentication techniques include cryptography, passwords, challenge/response protocols, and biometrics. The security design includes these techniques to help prevent counterfeit cards, unauthorized use, or information compromise. This paper discusses card authentication and user identity techniques that enhance security for microprocessor card systems. It also describes the analysis process used for determining proper authentication techniques for a system.