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BWR drywell behavior under steam blowdown.

Description: Historically, thermal hydraulics analyses on Large Break Loss of Coolant Accidents (LOCA) have been focused on the transients within the reactor or steam generator. Few have studied the effects of steam blowdown on the containment building. This paper discusses some theoretical issues as well as presenting numerical and experimental results of the blowdown tests performed at the Purdue University Multi-Dimensional Integrated Test Assembly (PUMA).
Date: May 8, 1998
Creator: NguyenLe, Q.
Partner: UNT Libraries Government Documents Department

Lithium-endohedral C{sub 60} complexes.

Description: High capacity, reversible, lithium intercalated carbon anodes have been prepared, 855 m.Ah/g, which exceed the capacity for stage 1 lithium intercalated carbon anodes, 372 mAh/g. Since there is very little hydrogen content in the high capacity anode, the fullerene C{sub 60} lattice is used to investigate the nature of lithium ion bonding and spacing between lithiums in endohedral lithium complexes of C{sub 60}. Three lithium-endohedral complexes have been investigated using ab initio molecular orbital calculations involving 2,3 and 5 lithium. The calculated results suggest that lithium cluster formation may be important for achieving the high capacity lithium carbon anodes.
Date: May 4, 1998
Creator: Scanlon, L. G.
Partner: UNT Libraries Government Documents Department

Thermal management concepts for higher efficiency heavy vehicles.

Description: Thermal management is a cross-cutting technology that directly or indirectly affects engine performance, fuel economy, safety and reliability, aerodynamics, driver/passenger comfort, materials selection, emissions, maintenance, and component life. This review paper provides an assessment of thermal management for large trucks, particularly as it impacts these features. Observations arrived at from a review of the state of the art for thermal management for over-the-road trucks are highlighted and commented on. Trends in the large truck industry, pertinent engine truck design and performance objectives, and the implications of these relative to thermal management, are presented. Finally, new thermal management concepts for high efficiency vehicles are described.
Date: May 19, 1999
Creator: Wambsganss, M. W.
Partner: UNT Libraries Government Documents Department

Calibration of an Advanced Photon Source linac beam position monitor used for positron position measurement of a beam containing both positrons and electrons.

Description: The Advanced Photon Source (APS) linac beam position monitors can be used to monitor the position of a positron beam also containing electrons. To accomplish this task, both the signal at the bunching frequency of 2856 MHz and the signal at 2 x 2856 MHz are acquired and processed for each stripline. The positron beam position is obtained by forming a linear combination of both 2856- and 5712-MHz signals for each stripline and then performing the standard difference over sum computation. The required linear combination of the 2856- and 5712-MHz signals depends on the electrical calibration of each stripline/cable combination. In this paper, the calibration constants for both 2856-MHz and 5712-MHz signals for each stripline are determined using a pure beam of electrons. The calibration constants are obtained by measuring the 2856- and 5712-MHz stripline signals at various electron beam currents and positions. Finally, the calibration constants measured using electrons are used to determine positron beam position for the mixed beam case.
Date: May 19, 1998
Creator: Sereno, N. S.
Partner: UNT Libraries Government Documents Department

The Cold War is over. What now?

Description: As you might imagine, the end of the Cold War has elicited an intense reexamination of the roles and missions of institutions such as the Los Alamos National Laboratory. During the past few years, the entire defense establishment has undergone substantial consolidation, with a concomitant decrease in support for research and development, including in areas such as materials. The defense industry is down-sizing at a rapid pace. Even universities have experienced significant funding cutbacks from the defense community. I view this as a profound time in history, bringing changes encompassing much more than just the defense world. In fact, support for science and technology is being reexamined across the board more completely than at any other time since the end of World War II.
Date: May 1995
Creator: Hecker, S. S.
Partner: UNT Libraries Government Documents Department

EUV/soft x-ray spectra for low B neutron stars

Description: Recent ROSAT and EUVE detections of spin-powered neutron stars suggest that many emit ``thermal`` radiation, peaking in the EUV/soft X-ray band. These data constrain the neutron stars` thermal history, but interpretation requires comparison with model atmosphere computations, since emergent spectra depend strongly on the surface composition and magnetic field. As recent opacity computations show substantial change to absorption cross sections at neutron star photospheric conditions, we report here on new model atmosphere computations employing such data. The results are compared with magnetic atmosphere models and applied to PSR J0437-4715, a low field neutron star.
Date: May 23, 1995
Creator: Romani, R.W.; Rajagopal, M.; Rogers, F.J. & Iglesias, C.A.
Partner: UNT Libraries Government Documents Department

Phosphate ceramic solidification and stabilization of cesium-containing crystalline silicotitanate resins.

Description: This paper reports on the fabrication and testing of magnesium potassium phosphate (MKP)-bonded cesium-loaded crystalline silicotitanate (CST) resins. Typical waste loading of CST resins in the final waste forms was 50 wt.%. Physical and chemical characterization of the MKP materials has shown them to be physically, chemically, and mineralogically stable. Long-term durability studies (using the AN 16.1 standard test) showed a leachability index of {approx}18 for cesium in the phosphate matrix when exposed to deionized water under ambient and elevated temperatures. Leaching of cesium was somewhat higher than in glass waste forms as per PCT and MCC-1 tests. MKP-based final waste forms showed no significant weight changes after exposure to aqueous media for {approx}90 days, indicating the highly insoluble nature of the phosphate matrix. In addition, durability of the CST-MKP waste forms was further established by freeze-thaw cycling tests.
Date: May 11, 1999
Creator: Langton, C. A.
Partner: UNT Libraries Government Documents Department

``Clean`` fuels: Does the new direction make environmental sense?

Description: This paper examines the ramifications of this a three-pronged energy philosophy, with special reference to its expected environmental impact if it is fully implemented as policy. To recapitulate, the three prongs are to rely on a free energy market to determine winners and losers, which could certainly include Reformulated Gasoline (RFG) if it remains relatively cheap and clean; refocus the bulk of government-sponsored transportation energy research toward a ``great leap ahead`` to fully renewable and essentially pollution-free fuels such as hydrogen and fuel cells; and discontinue AFV pump priming. Of special interest is a premise that appears common to all prongs--that none of these measures represents a retreat from environmental goals or accomplishments on record since the National Environmental Policy Act of 1969 was passed.
Date: May 1996
Creator: Saricks, C. L. & Wang, M. Q.
Partner: UNT Libraries Government Documents Department

Comparison of soft and hard tissue ablation with sub-ps and ns pulse lasers

Description: Tissue ablation with ultrashort laser pulses offers several unique advantages. The nonlinear energy deposition is insensitive to tissue type, allowing this tool to be used for soft and hard tissue ablation. The localized energy deposition lead to precise ablation depth and minimal collateral damage. This paper reports on efforts to study and demonstrate tissue ablation using an ultrashort pulse laser. Ablation efficiency and extent of collateral damage for 0.3 ps and 1000 ps duration laser pulses are compared. Temperature measurements of the rear surface of a tooth section is also presented.
Date: May 1, 1996
Creator: Da Silva, L.B.; Stuart, B.C.; Celliers, P.M.; Feit, M.D.; Glinsky, M.E.; Heredia, N.J. et al.
Partner: UNT Libraries Government Documents Department

BUGLE-96: A revised multigroup cross section library for LWR applications based on ENDF/B-VI Release 3

Description: A revised multigroup cross-section library based ON ENDF/B-VI Release 3 has been produced for light water reactor shielding and reactor pressure vessel dosimetry applications. This new broad-group library, which is designated BUGLE-96, represents an improvement over the BUGLE-93 library released in February 1994 and is expected to replace te BUGLE-93 data. The cross-section processing methodology is the same as that used for producing BUGLE-93 and is consistent with ANSI/ANS 6.1.2. As an added feature, cross-section sets having upscatter data for four thermal neutron groups are included in the BUGLE-96 package available from the Radiation Shielding Information Center. The upscattering data should improve the application of this library to the calculation of more accurate thermal fluences, although more computer time will be required. The incorporation of feedback from users has resulted in a data library that addresses a wider spectrum of user needs.
Date: May 1, 1996
Creator: White, J.E.; Ingersoll, D.T.; Slater, C.O. & Roussin, R.W.
Partner: UNT Libraries Government Documents Department

Waste vitrification projects throughout the US initiated by SRS

Description: Technologies are being developed by the US Department of Energy (DOE) Nuclear Facility sites to convert high-level, low-level, and mixed wastes to a solid stabilized waste form for permanent disposal. Vitrification is one of the most important and environmentally safest technologies being developed. The Environmental Protection Agency (EPA) has declared vitrification the Best Demonstrated Available Technology (BDAT) for high-level radioactive waste and produced a Handbook of Vitrification Technologies for Treatment of Hazardous and Radioactive Waste. The Defense Waste Processing Facility (DWPF) being tested at Savannah River Site (SRS) will soon begin vitrifying the high-level waste at SRS. The DOE Office of Technology Development (OTD) has taken the position that mixed waste needs to be stabilized to the highest level reasonably possible to ensure that the resulting waste forms will meet both the current and future regulatory specifications. Vitrification produces durable waste forms at volume reductions up to 97%. Large reductions in volume minimize long-term storage costs making vitrification cost effective on a life cycle basis.
Date: May 1, 1996
Creator: Jantzen, C.M.; Whitehouse, J.C.; Smith, M.E.; Ramsey, W.G. & Pickett, J.B.
Partner: UNT Libraries Government Documents Department

Development of large scale production of Nd-doped phosphate glasses for megajoule-scale laser systems

Description: Nd-doped phosphate glasses are the preferred gain medium for high-peak-power lasers used for Inertial Confinement Fusion research because they have excellent energy storage and extraction characteristics. In addition, these glasses can be manufactured defect-free in large sizes and at relatively low cost. To meet the requirements of the future mega-joule size lasers, advanced laser glass manufacturing methods are being developed that would enable laser glass to be continuously produced at the rate of several thousand large (790 x 440 x 44 mm{sup 3}) plates of glass per year. This represents more than a 10 to 100-fold improvement in the scale of the present manufacturing technology.
Date: May 1, 1996
Creator: Ficini, G. & Campbell, J.H.
Partner: UNT Libraries Government Documents Department

Increased efficiency of topping cycle PCFB power plants

Description: Pressurized circulating fluidized bed (PCFB) power plants offer the power industry significantly increased efficiencies with reduced costs of electricity and lower emissions. When topping combustion is incorporated in the plant, these advantages are enhanced. In the plant, coal is fed to a pressurized carbonizer that produces a low-Btu fuel gas and char. After passing through a cyclone and ceramic barrier filter to remove gas-entrained particulates and a packed bed of emathelite pellets to remove alkali vapors. the fuel gas is burned in a topping combustor to produce the energy required to drive a gas turbine. The gas turbine drives a generator combustor, and a fluidized bed heat exchanger (FBHE). The carbonizer char is burned in the PCFB and the exhaust gas passes through its own cyclone, ceramic barrier filter, and alkali getter and supports combustion of the fuel gas in the topping combustor. Steam generated in a heat-recovery steam generator (HRSG) downstream of the gas turbine and in the FBHE associated with the PCFB drives the steam turbine generator that furnishes the balance of electric power delivered by the plant.
Date: May 1, 1996
Creator: Robertson, A.; Domeracki, W. & Horazak, D.
Partner: UNT Libraries Government Documents Department

On the use of diffusion synthetic acceleration in parallel 3D neutral particle transport calculations

Description: The linear Boltzmann transport equation (BTE) is an integro-differential equation arising in deterministic models of neutral and charged particle transport. In slab (one-dimensional Cartesian) geometry and certain higher-dimensional cases, Diffusion Synthetic Acceleration (DSA) is known to be an effective algorithm for the iterative solution of the discretized BTE. Fourier and asymptotic analyses have been applied to various idealizations (e.g., problems on infinite domains with constant coefficients) to obtain sharp bounds on the convergence rate of DSA in such cases. While DSA has been shown to be a highly effective acceleration (or preconditioning) technique in one-dimensional problems, it has been observed to be less effective in higher dimensions. This is due in part to the expense of solving the related diffusion linear system. We investigate here the effectiveness of a parallel semicoarsening multigrid (SMG) solution approach to DSA preconditioning in several three dimensional problems. In particular, we consider the algorithmic and implementation scalability of a parallel SMG-DSA preconditioner on several types of test problems.
Date: May 14, 1998
Creator: Brown, P. & Chang, B.
Partner: UNT Libraries Government Documents Department

Assessment of the technical viability of reactor options for plutonium disposition

Description: Various reactor concepts for the disposition of surplus Pu have been proposed by reactor vendors; not all have attained the same level of technical viability. Studies were performed to differentiate between reactor concepts by devising a quantitative index for technical viability. For a quantitative assessment, three issues required resolution: the definition of a technical maturity scale, the treatment of ``subjective`` factors which cannot be easily represented in a quantitative format, and the protocol for producing a single technical viability figure-of-merit for each alternative. Alternatives involving the use of foreign facilities were found to be the most technically viable.
Date: May 1, 1996
Creator: Primm, R.T. III
Partner: UNT Libraries Government Documents Department

Application of the GRI 1.2 methane oxidation model to methane and methanol oxidation in supercritical water

Description: The GRI 1.2 mechanism is used to predict the oxidation rates of methane and methanol by oxygen in supercritical water at 250 bar and temperatures ranging from 420--630 C. Using the Chemkin II computational package which assumes an ideal gas equation of state, the GRI model does very well in representing the available experimental results on methane over a wide temperature and concentration rate. However, the model may lack key CH{sub 3}O{sub 2} reactions needed for a complete description in the < 450 C region. The oxidation of methanol and formation of formaldehyde is not well represented by the GRI mechanism when left unchanged. If two important modifications are made to the reactivity of HO{sub 2}, good agreement with the methanol oxidation results is achieved. This paper illustrates that the carefully-assembled GRI 1.2 mechanism, although designed for conventional combustion conditions, can be successfully extended with very little modification to much lower temperature and extreme pressure conditions. The purpose of this study is to understand the operative chemical kinetics of supercritical water oxidation required for the more efficient application of this technology to treatment of hazardous wastes, obsolete munitions, rocket motors, and chemical warfare agents.
Date: May 1996
Creator: Rice, S. F.
Partner: UNT Libraries Government Documents Department

Reducing residential cooling requirements through the use of electrochromic windows

Description: This paper presents the results of a study investigating the energy performance of electrochromic windows in a prototypical residential building under a variety of state switching control strategies. We used the DOE-2.1E energy simulation program to analyze the annual cooling energy and peak demand as a function of glazing type, size, and electrochromic control strategy. A single-story ranch-style home located in the cooling-dominated locations of Miami, FL and Phoenix, AZ was simulated. Electrochromic control strategies analyzed were based on incident total solar radiation, space cooling load, and outside air temperature. Our results show that an electrochromic material with a high reflectance in the colored state provides the best performance for all control strategies. On the other hand, electrochromic switching using space cooling load provides the best performance for all the electrochromic materials. The performance of the incident total solar radiation control strategy varies as a function of the values of solar radiation which trigger the bleached and colored states of the electrochromic (setpoint range); i.e., required cooling decreases as the setpoint range decreases; also, performance differences among electrochromics increases. The setpoint range of outside air temperature control of electrochromics must relate to the ambient weather conditions prevalent in a particular location. If the setpoint range is too large, electrochromic cooling performance is very poor. Electrochromics compare favorably to conventional low-E clear glazings that have high solar heat gain coefficients that are used with overhangs. However, low-E tinted glazings with low solar heat gain coefficients can outperform certain electrochromics. Overhangs should be considered as a design option for electrochromics whose state properties do not change significantly between bleached and colored states.
Date: May 1, 1995
Creator: Sullivan, R.; Rubin, M. & Selkowitz, S.
Partner: UNT Libraries Government Documents Department

A general protocol for restoration of entire river catchments

Description: Large catchment basins may be viewed as ecosystems with interactive natural and cultural attributes. Stream regulation severs ecological connectivity between channels and flood plains by reducing the range of natural flow and temperature variation, reduces the capacity of the ecosystem to sustain native biodiversity and bioproduction and promotes proliferation of non-native biota. However, regulated rivers regain normative attributes, which promote recovery of native biota, as distance from the dam increases and in relation to the mode of regulation. Therefore, reregulation of flow and temperature to normative pattern, coupled with elimination of pollutants and constrainment of nonnative biota, can naturally restore damaged habitats from headwaters to mouth. The expectation is rapid recovery of depressed populations of native species. The protocol requires: restoration of seasonal temperature patterns; restoration of peak flows needed to reconnect and periodically reconfigure channel and floodplain habitats; stabilization of base flows to revitalize the shallow water habitats; maximization of dam passage to allow restoration of metapopulation structure; change in the management belief system to rely on natural habitat restoration as opposed to artificial propagation, installation of artificial instream structures (river engineering) and artificial food web control; and, practice of adaptive ecosystem management.
Date: May 28, 1996
Creator: Stanford, J.A.; Frissell, C.A.; Ward, J.V.; Liss, W.J.; Coutant, C.C.; Williams, R.N. et al.
Partner: UNT Libraries Government Documents Department