1,171 Matching Results

Search Results

Status report on the long-term stability of the Advanced Photon Source.

Description: Table 1 summarizes the average elevation changes and standard deviations as well as the points with the largest changes for each year. On average, hardly any settlements can be detected; however, local changes of +2.90 mm to {minus}2.31 mm have been measured. Looking at the low and high points, the settlement process is slowing down over time. Overall, the settlements observed match the expectations for this type of construction. To date no major realignment of the Advanced Photon Source (APS) storage ring has been necessary. The particle beam tracks with the settlements of the floor as long as these changes occur in a smooth fashion and not as sudden discontinuities [5]. From Figures 6 through 8 it is also apparent that settlements affect larger areas in the storage ring and experiment hall that impact the location of the source point as well as the location of the beamline user equipment. The limiting apertures of the insertion device chambers will make realignment of the APS storage ring a necessity at some point in the future. Currently simulations and machine studies we underway to provide an estimate of tolerable settlement limits before a realignment of certain sections of the storage ring would be required. In conclusion, the APS has been constructed on solid ground with an excellent foundation. Only small settlement changes are being observed; so far they are not impacting the operation of the accelerator. We are continuing to monitor deformations of the APS floor in anticipation of a future realignment of the accelerator components.
Date: September 21, 1998
Creator: Friedsam, H.
Partner: UNT Libraries Government Documents Department

Thermal recovery measurements on multi-segment amplifiers

Description: We present the results of a series of experiments to measure the thermal recovery times of a flashlamp-pumped, Nd:Glass multi-segment laser amplifier. In particular, we investigated the thermal recovery times under the following cooling options: (1) passive cooling; (2) active cooling of the flashlamp cassettes, and (3) active cooling of the flashlamp cassettes and gas flow in the pump cavity.
Date: September 21, 1995
Creator: Rotter, M.D.; McCracken, R.W.; Erlandson, A.C. & Brown, D.
Partner: UNT Libraries Government Documents Department

Measurement techniques in dry-powdered processing of spent nuclear fuels.

Description: High-performance liquid chromatography (HPLC) with inductively coupled plasma mass spectrometry (ICPMS) detection, {alpha}-spectrometry ({alpha}-S), and {gamma}-spectrometry ({gamma}-S) were used for the determination of nuclide content in five samples excised from a high-burnup fuel rod taken from a pressurized water reactor (PWR). The samples were prepared for analysis by dissolution of dry-powdered samples. The measurement techniques required no separation of the plutonium, uranium, and fission products. The sample preparation and analysis techniques showed promise for in-line analysis of highly-irradiated spent fuels in a dry-powdered process. The analytical results allowed the determination of fuel burnup based on {sup 148}Nd, Pu, and U content. A goal of this effort is to develop the HPLC-ICPMS method for direct fissile material accountancy in the dry-powdered processing of spent nuclear fuel.
Date: July 21, 1999
Creator: Bowers, D. L.; Hong, J.-S.; Kim, H.-D.; Persiani, P. J. & Wolf, S. F.
Partner: UNT Libraries Government Documents Department

EVOLVE - an advanced first wall/blanket system.

Description: A new concept for an advanced fusion first wall and blanket has been identified. The key feature of the concept is the use of the heat of vaporization of lithium (about 10 times higher than water) as the primary means for capturing and removing the fusion power. A reasonable range of boiling temperatures of this alkali metal is 1200 to 1400 C, corresponding with a saturation pressure of 0.035 to 0.2 MPa. Calculations indicate that a evaporative system with Li at {approximately}1200 C can remove a first wall surface heat flux of >2 MW/m2 with an accompanying neutron wall load of >10 MW/m2. Work to date shows that the system provides adequate tritium breeding and shielding, very high thermal conversion efficiency, and low system pressure. Tungsten is used as the structural material, and it is expected to operate at a surface wall load of 2 MW/m2 at temperatures above 1200 C.
Date: July 21, 1999
Creator: Khater, H.; Majumdar, S.; Malang, S.; Mattas, R. F.; Mogahed, E.; Nelson, B. et al.
Partner: UNT Libraries Government Documents Department

FUTURE KAON INITIATIVES AT BNL.

Description: Although the Brookhaven AGS will become an injector to RHIC, it will still be available for external proton beam experiments. I discuss a number new K decay experiments which have been proposed for this facility.
Date: June 21, 1999
Creator: LITTENBERG,L.
Partner: UNT Libraries Government Documents Department

Cosmological parameters and power spectrum from peculiar velocities

Description: The power spectrum of mass density fluctuations is evaluated from the Mark III and the SFI catalogs of peculiar velocities by a maximum likelihood analysis, using parametric models for the power spectrum and for the errors. The applications to the two different data sets, using generalized CDM models with and without COBE normalization, give consistent results. The general result is a relatively high amplitude of the power spectrum, with {sigma}{sub 8}{Omega}{sub m}{sup 0.6} = 0.8 {+-} 0.2 at 90% confidence. Casting the results in the {Omega}{sub m} {minus} {Omega}{sub {Lambda}} plane, yields complementary constraints to those of the high-redshift supernovae, together favoring a nearly flat, unbound and accelerating universe with comparable contributions from {Omega}{sub m} and {Omega}{sub {Lambda}}. Further implications on the cosmological parameters, arising from a joint analysis of the velocities together with small-scale CMB anisotropies and the high-redshift supernovae, are also briefly described.
Date: September 21, 1999
Creator: Zehavi, Idit
Partner: UNT Libraries Government Documents Department

EXPECTED TRIGGER RATES OF HIGH PT JETS AND DIRECT PHOTONS IN THE STAR EMC.

Description: The STAR experiment at RHIC is a large acceptance detector. The electromagnetic calorimeter (EMC) will provide a sensitive trigger to study high p{sub t} jets and hard photons in AuAu, pp, and pAu collisions. The capability for the EMC to trigger on jets and direct photons was studied for trigger level 0. Trigger efficiencies and expected process rates were obtained for pp reactions. Results from pp interactions will be essential to the interpretation of AuAu results as well as for the spin physics program. These studies were performed with the standard STAR software chain which includes GEANT and EMC simulations. The HIJING event generator was used to provide input for the simulations.
Date: March 21, 1999
Creator: BELT-TONJES,M. FOR THE STAR COLLABORATION
Partner: UNT Libraries Government Documents Department

Hybrid electric vehicles TOPTEC

Description: This one-day TOPTEC session began with an overview of hybrid electric vehicle technology. Updates were given on alternative types of energy storage, APU control for low emissions, simulation programs, and industry and government activities. The keynote speech was about battery technology, a key element to the success of hybrids. The TOPEC concluded with a panel discussion on the mission of hybrid electric vehicles, with a perspective from industry and government experts from United States and Canada on their view of the role of this technology.
Date: June 21, 1994
Partner: UNT Libraries Government Documents Department

Incorporation of radionuclides from the electrometallurgical treatment of spent fuel into a ceramic waste form.

Description: An electrometallurgical process is being developed at Argonne National Laboratory to treat spent metallic nuclear fuel. In this process, the spent nuclear fuel is electrorefined in a molten salt to separate uranium from the other constituents of the fuel. The treatment process generates a contaminated chloride salt that is incorporated into a ceramic waste form. The ceramic waste form, a composite of socialite and glass, contains the fission products (rare earths, alkalis, alkaline earth metals, and halides) and transuranic radionuclides that accumulated in the electrorefiner salt. These radionuclides are incorporated into zeolite A, which can fully accommodate the salt in its crystal structure. The radionuclides are incorporated into the zeolite by high-temperature blending or by ion exchange. In the blending process the salt and zeolite are simply tumbled together at >450 C (723 K), but in the ion exchange process, which yields a product more highly concentrated in fission products, the molten salt is passed through a bed of the zeolite. In either case, the salt-loaded zeolite A is mixed with glass frit and hot isostatically pressed to produce a monolithic leach resistant waste form. Zeolite is converted to sodalite during hot pressing. This paper presents experimental results on the fission product uptake of the zeolite as a function of time and salt composition.
Date: December 21, 1998
Creator: Pereira, C.
Partner: UNT Libraries Government Documents Department

Laboratory Simulation of Response to a Distributed Pressure Load

Description: Responses to a distributed pressure load are typically predicted through the use of a finite-element model. This procedure depends on the model to represent the actual structure accurately. Another technique that is developed in this work is to predict the response based upon an experi- mentally derived model. This model consists of frequency response functions. The pressure distribution is assumed to be known. In this work, the pressure load will be a blast load. The focus of this work will be to simulate a harsh, shock-like environment. Data from a reverse Hopkinson bar (RHB) test is used to generate the response to a symmetric, distributed load. The reverse Hopkinson bar generates a high ampli- tude, high frequency content pulse that excites components at near-blast levels. The frequency response functions gen- erated from the RHB are used to generate an experimental model of the structure, which is then used in conjunction with the known pressure distribution, to estimate the component response to a blast. This result can then be used with a model correlation technique to adjust a finite element model such that data from a true blast test can be used to only fine tune the model. This work details the estimation response due to the blast.
Date: October 21, 1998
Creator: Mayes, R. & Simmermacher, T.
Partner: UNT Libraries Government Documents Department

THE YEAR-ONE PHYSICS CAPABILITIES OF STAR.

Description: When the Relativistic Heavy Ion Collider (RHIC) at BNL begins operation in the Fall of 1999, heavy ions will be accelerated in collider mode for the first time, and a new energy regime will be entered for Heavy Ion Physics. The Solenoidal Tracker At RHIC (STAR) detector has a near 4{pi} coverage and is dedicated to taking hadronic measurements. A large volume Time Projection Chamber placed in a solenoidal magnet at 0.5T is used to track and identify the many thousands of produced particles. STAR will measure many observables simultaneously on an event-by-event basis to study signatures of a possible QGP phase transition and the space-time evolution of the collision process. The goal is to obtain a fundamental understanding of the microscopic structure of hadronic interactions, at the level of quarks and gluons, at high energy densities. This paper outlines the physics STAR intends to study during the first year of operation.
Date: March 21, 1999
Creator: CAINES,H. FOR THE STAR COLLABORATION
Partner: UNT Libraries Government Documents Department

Experiments on Corium Dispersion after Lower Head Failure at Moderate Pressure

Description: Concerning the mitigation of high pressure core melt scenarios, the design objective for future PWRS is to transfer high pressure core melt to low pressure core melt sequences, by means of pressure relief valves at the primary circuit, with such a discharge capacity to limit the pressure in the reactor coolant system to less than 20 bar. Studies have shown that in late in-vessel reflooding scenarios there may be a time window where the pressure is indeed in this range, at the moment of the reactor vessel rupture. It has to be verified that large quantities of corium released from the vessel after failure at pressures <20 bar cannot be carried out of the reactor pit, because the melt collecting and cooling concept of future PWRs would be rendered useless. Existing experiments investigated the melt dispersal phenomena in the context of the DCH resolution for existing power plants in the USA, most of them having cavities with large instrument tunnels leading into subcompartments. For such designs, breaches with small cross sections at high vessel failure pressures had been studied. However, some present and future European PWRs have an annular cavity design without a large pathway out of the cavity other than through the narrow annular gap between the RPV and the cavity wall. Therefore, an experimental program was launched, focusing on the annular cavity design and low pressure vessel failure. The first part of the program comprises two experiments which were performed with thermite melt steam and a prototypic atmosphere in the containment in a scale 1:10. The initial pressure in the RPV-model was 11 and 15 bars, and the breach was a hole at the center of the lower head with a scaled diameter of 100 cm and 40 cm, respectively. The main results were: 78% of melt mass ...
Date: September 21, 1999
Creator: BLANCHAT,THOMAS K.; GARGALLO,M.; JACOBS,G.; MEYER,L. & WILHELM,D.
Partner: UNT Libraries Government Documents Department

X-ray and visible light transmission as two-dimensional, full-field moisture-sensing techniques: A preliminary comparison

Description: Two independent high-resolution moisture-sensing techniques, x-ray absorption and light transmission, have been developed for use in two-dimensional, thin-slab experimental systems. The techniques yield full-field measurement capabilities with exceptional resolution of moisture content in time and space. These techniques represent powerful tools for the experimentalist to investigate processes governing unsaturated flow and transport through fractured and nonfractured porous media. Evaluation of these techniques has been accomplished by direct comparison of data obtained by means of the x-ray and light techniques as well as comparison with data collected by gravimetric and gamma-ray densitometry techniques. Results show excellent agreement between data collected by the four moisture-content measurement techniques. This program was established to support the Yucca Mountain Site Characterization Project.
Date: January 21, 1992
Creator: Tidwell, V. C. & Glass, R. J.
Partner: UNT Libraries Government Documents Department

Implementation of U.S. transparency monitoring under the U.S./Russian HEU purchase agreement

Description: During the past three years US monitoring at Russian nuclear facilities, subject to the HEU Purchase Agreement, has evolved as MINATOM and DOE negotiators worked to improve transparency rights and as additional Russian facilities began processing HEU. The number of Russian nuclear facilities subject to US monitoring has increased from two in 1996 to the current four. In that time, physical monitoring, which only permitted visual inspections and access to process forms is being supplemented by instrumentation which detects U-235 enrichment of material in containers and instrumentation which is used to confirm that blending of HEU into LEU at the blending facilities is taking place. This paper summarizes the US HEU Transparency monitoring activities performed in Russian facilities. It then summarizes the process used to certify the Blend Down Monitoring System (BDMS) that is currently in use at one of these facilities.
Date: July 21, 1999
Creator: Benton, J B; Glaser, J W & Mastal, E F
Partner: UNT Libraries Government Documents Department

Development and application of NDE methods for monolithic and continuous fiber ceramic matrix composites.

Description: Monolithic structural ceramics and continuous fiber ceramic matrix composites (CMCs) are being developed for application in many thermally and chemically aggressive environments where structural reliability is paramount. We have recently developed advanced nondestructive evaluation (NDE) methods that can detect distributed ''defects'' such as density gradients and machining-induced damage in monolithic materials, as well as delamination, porosity, and throughwall cracks, in CMC materials. These advanced NDE methods utilize (a) high-resolution, high-sensitivity thermal imaging; (b) high-resolution X-ray imaging; (c) laser-based elastic optical scattering; (d) acoustic resonance; (e) air-coupled ultrasonic methods; and (f) high-sensitivity fluorescent penetrant technology. This paper discusses the development and application of these NDE methods relative to ceramic processing and ceramic components used in large-scale industrial gas turbines and hot gas filters for gas stream particulate cleanup.
Date: May 21, 1999
Creator: Ellingson, W. A.
Partner: UNT Libraries Government Documents Department

Simulation of edge-plasma profiles and turbulence related to L-H transitions in tokamaks

Description: Understanding plasma profile evolution and plasma turbulence are two important aspects of developing a predictive model for edge-plasma in tokamaks and other fusion-related devices. Here they describe results relevant to the L-H transition phenomena observed in tokamaks obtained from two simulations codes which emphasize the two aspects of the problem. UEDGE solves for the two-dimensional (2-D) profiles of a multi-species plasma and neutrals given some anomalous cross-field diffusion coefficients, and BOUT solves for the three-dimensional (3-D) turbulence that gives rise to the anomalous diffusion. These two codes are thus complementary in solving different aspects of the edge-plasma transport problem; ultimately, they want to couple the codes so that UEDGE uses BOUT's turbulence transport results, and BOUT uses UEDGE's plasma profiles with a fully automated iteration procedure. This goal is beyond the present paper; here they show how each aspect of the problem, i.e., profiles and turbulent transport, can contribute to L-H type transitions.
Date: September 21, 1999
Creator: Cohen, R H; Rognlien, T D & Xu, X Q
Partner: UNT Libraries Government Documents Department

Development of NDE methods for hot gas filters.

Description: Ceramic hot gas candle filters are currently under development for hot gas particulate cleanup in advanced coal-based power systems. The ceramic materials for these filters include nonoxide monolithic, nonoxide-fiber-reinforced composites, and nonoxide reticulated foam. A concern is the lack of reliable data on which to base decisions for reusing or replacing hot gas filters during plant shutdowns. The work in this project is aimed at developing nondestructive evaluation (FIDE) technology to allow detection, and determination of extent, of life-limiting characteristics such as thermal fatigue, oxidation, damage from ash bridging such as localized cracking, damage from local burning, and elongation at elevated temperature. Although in-situ NDE methods are desirable in order to avoid disassembly of the candle filter vessels, the current vessel designs, the presence of filter cakes and possible ash bridging, and the state of NDE technology prevent this. Candle filter producers use a variety of NDE methods to ensure as-produced quality. While impact acoustic resonance offers initial promise for examining new as-produced filters and for detecting damage in some monolithic filters when removed from service, it presents difficulties in data interpretation, it lacks localization capability, and its applicability to composites has yet to be demonstrated. Additional NDE technologies being developed and evaluated in this program and whose applicability to both monolithics and composites has been demonstrated include (a) full-scale thermal imaging for analyzing thermal property variations; (b) fret, high-spatial-resolution X-ray imaging for detecting density variations and dimensional changes; (c) air-coupled ultrasonic methods for determining through-thickness compositional variations; and (d) acoustic emission technology with mechanical loading for detecting localized bulk damage. New and exposed clay-bonded SiC filters and CVI-SiC composite filters have been tested with these additional NDE methods.
Date: July 21, 1999
Creator: Deemer, C.; Ellingson, W. A.; Koehl, E. R.; Lee, H.; Spohnholtz, T. & Sun, J. G.
Partner: UNT Libraries Government Documents Department

Recent results from the National Transparent Optical Networks (NTON)

Description: We review the NTON program, its design and its recent progress on deployment. We then focus on one aspect of our design process, namely modeling the links of the network at the physical layer.
Date: July 21, 1999
Creator: Feng, H X; Heritage, J P; Lennon, W J & Thombley, R L
Partner: UNT Libraries Government Documents Department

Welding metallurgy of nickel alloys in gas turbine components

Description: Materials for gas turbine engines are required to meet a wide range of temperature and stress application requirements. These alloys exhibit a combination of creep resistance, creep rupture strength, yield and tensile strength over a wide temperature range, resistance to environmental attack (including oxidation, nitridation, sulphidation and carburization), fatigue and thermal fatigue resistance, metallurgical stability and useful thermal expansion characteristics. These properties are exhibited by a series of solid-solution-strengthened and precipitation-hardened nickel, iron and cobalt alloys. The properties needed to meet the turbine engine requirements have been achieved by specific alloy additions, by heat treatment and by thermal mechanical processing. A thorough understanding of the metallurgy and metallurgical processing of these materials is imperative in order to successfully fusion weld them. This same basic understanding is required for repair of a component with the added dimension of the potential effects of thermal cycling and environmental exposure the component will have endured in service. This article will explore the potential problems in joining and repair welding these materials.
Date: May 21, 1997
Creator: Lingenfelter, A. C., LLNL
Partner: UNT Libraries Government Documents Department

Ab initio and density functional studies of hydrocarbon adsorption in zeolites.

Description: The adsorption energies of methane and ethane in zeolites are investigated with ab initio molecular orbital theory and density functional theory. In this work we have used zeolite cluster models containing two, three, and five tetrahedral (Si, Al) atoms and have found equilibrium structures for complexes of methane, ethane, and propane with an acid site. If a large enough cluster is used and correlation effects are included via perturbation theory, the calculated adsorption energy for ethane is about 5 kcal/mol compared with the experimental value of 7.5 kcal/mol. The B3LYP density functional method gives a much smaller binding of {approximately}1 kcal/mol for ethane. The reason for the failure of density fictional theory is unclear.
Date: August 21, 1998
Creator: Curtiss, L. A.
Partner: UNT Libraries Government Documents Department

Modeling Solute Diffusion in the Presence of Pore-Scale Heterogeneity

Description: A range of pore diffusivities, D{sub p}, is implied by the high degree of pore-scale heterogeneity observed in core samples of the Culebra (dolomite) Member of the Rustler formation, NM. Earlier tracer tests in the culebra at the field-scale have confirmed significant heterogeneity in diffusion rate coefficients (the combination of D{sub p} and matrix block size). In this study, expressions for solute diffusion in the presence of multiple simultaneous matrix diffusivities are presented and used to model data from eight laboratory-scale diffusion experiments performed on five Culebra samples. A lognormal distribution of D{sub p} is assumed within each of the lab samples. The estimated standard deviation ({sigma}{sub d}) of In(D{sub p}) within each sample ranges from 0 to 1, with most values lying between 0.5 and 1. The variability over all samples leads to a combined {sigma}{sub d} in the range of 1.0 to 1.2, which appears to be consistent with a best-fit statistical distribution of formation factor measurements for similar Culebra samples. A comparison of the estimation results to other rock properties suggests that, at the lab-scale, the geometric mean of D{sub p} increases with bulk porosity and the quantity of macroscopic features such as vugs and fractures. However, {sigma}{sub d} appears to be determined by variability within such macroscopic features and/or by micropore-scale heterogeneity. In addition, comparison of these experiments to those at larger spatial scales suggests that increasing sample volume results in an increase in {sigma}{sub d}.
Date: October 21, 1999
Creator: FLEMING,SEAN W. & HAGGERTY,ROY
Partner: UNT Libraries Government Documents Department

Roles and Delegation of Authority (R/DA) System

Description: The processes of defining managerial roles and providing for delegation of authority are essential to any enterprise. At most large organizations, these processes are defined in policy manuals and through sets of standard operating procedures for many, if not all, business and administrative functions. Many of these staff-initiated, administrative functions require the routing of documents for approval to one or more levels of management. These employee-oriented, back office types of workflows tend to require more flexibility in determining to whom these documents should go to, while, at the same time, providing the responsible parties with the flexibility to delegate their approval authority or allow others to review their work. Although this practice is commonplace in manual, paper-based processes that exist in many organizations, it is difficult to provide the same flexibility in the more structured, electronic-based, workflow systems.
Date: October 21, 1999
Creator: ABBOTT,JOHN P.; HUTCHINS,JAMES C. & SCHOCH,DAVID G.
Partner: UNT Libraries Government Documents Department

A practical microgripper by fine alignment, eutectic bonding and SMA actuation

Description: A silicon microgripper with a large gripping force, a relatively rigid structural body, and flexibility in functional design is presented. The actuation is generated by Ni-Ti-Cu shape memory alloy (SMA) films and the stress induced can deflect each side of the microgripper up to 55 {mu}m for a total gripping motion of 110 {mu}m. When fully open, the force exerted by the film corresponds to a 40 mN gripping force on the tip of the gripper.
Date: April 21, 1995
Creator: Lee, A. P.; Ciarlo, D. R. & Krulevitch, P. A.
Partner: UNT Libraries Government Documents Department

Fate of neptunium in an anaerobic, methanogenic microcosm.

Description: Neptunium is found predominantly as Np(IV) in reducing environments, but Np(V) in aerobic environments. However, currently it is not known how the interplay between biotic and abiotic processes affects Np redox speciation in the environment. In order to evaluate the effect of anaerobic microbial activity on the fate of Np in natural systems, Np(V) was added to a microcosminoculated with anaerobic sediments from a metal-contaminated fresh water lake. The consortium included metal-reducing, sulfate-reducing, and methanogenic microorganisms, and acetate was supplied as the only exogenous substrate. Addition of more than 10{sup {minus}5} M Np did not inhibit methane production. Total Np volubility in the active microcosm, as well as in sterilized control samples, decreased by nearly two orders of magnitude. A combination of analytical techniques, including VIS-NIR absorption spectroscopy and XANES, identified Np(IV) as the oxidation state associated with the sediments. The similar results from the active microcosm and the abiotic controls suggest that microbian y produced Mn(II/HI) and Fe(II) may serve as electron donors for Np reduction.
Date: December 21, 1998
Creator: Banaszak, J. E.
Partner: UNT Libraries Government Documents Department