6,152 research outputs found
Recommended from our members
Technology Opportunities to Reduce U.S. Greenhouse Gas Emissions
The rise in greenhouse gas emissions from fossil fuel combustion and industrial and agricultural activities has aroused international concern about the possible impacts of these emissions on climate. Greenhouse gases--mostly carbon dioxide, some methane, nitrous oxide and other trace gases--are emitted to the atmosphere, enhancing an effect in which heat reflected from the earth's surface is kept from escaping into space, as in a greenhouse. Thus, there is concern that the earth's surface temperature may rise enough to cause global climate change. Approximately 90% of U.S. greenhouse gas emissions from anthropogenic sources come from energy production and use, most of which are a byproduct of the combustion of fossil fuels. On a per capita basis, the United States is one of the world's largest sources of greenhouse gas emissions, comprising 4% of the world's population, yet emitting 23% of the world's greenhouse gases. Emissions in the United States are increasing at around 1.2% annually, and the Energy Information Administration forecasts that emissions levels will continue to increase at this rate in the years ahead if we proceed down the business-as-usual path. President Clinton has presented a two-part challenge for the United States: reduce greenhouse gas emissions and grow the economy. Meeting the challenge will mean that in doing tomorrow's work, we must use energy more efficiently and emit less carbon for the energy expended than we do today. To accomplish these goals, President Clinton proposed on June 26, 1997, that the United States ''invest more in the technologies of the future''. In this report to Secretary of Energy Pena, 47 technology pathways are described that have significant potential to reduce carbon dioxide emissions. The present study was completed before the December 1997 United Nations Framework Convention on Climate Change and is intended to provide a basis to evaluate technology feasibility and options to reduce greenhouse gas emissions. These technology pathways (which are described in greater detail in Appendix B, Technology Pathways) address three areas: energy efficiency, clean energy, and carbon sequestration (removing carbon from emissions and enhancing carbon storage). Based on an assessment of each of these technology pathways over a 30-year planning horizon, the directors of the Department of Energy's (DOE's) national laboratories conclude that success will require pursuit of multiple technology pathways to provide choices and flexibility for reducing greenhouse gas emissions. Advances in science and technology are necessary to reduce greenhouse gas emissions from the United States while sustaining economic growth and providing collateral benefits to the nation
Recommended from our members
Detoxification of hazardous waste streams using microwave-assisted fluid-bed oxidation
Microwave-assisted oxidation of trichloroethane (TCE) performed at 500-580{degree}C has been found to be significantly more efficient than conventional oxidation methods. Experiments were conducted using a 6 kilowatt, 2.45 gigohertz power supply and a 6 inch bed of silicon carbide granules in a 1 inch diameter quartz reactor tube which in turn was placed in a microwave cavity. After heating the reactor to a given temperature a TCE-air stream was passed through the silicon carbide bed. TCE was almost completely detoxified (98--99%) in a single pass through the silicon carbide bed at 500--580{degree}C. The oxidation products are HCl, CO{sub 2} and CO. By comparison the corresponding single-pass detoxification using conventional thermal methods results in only partial conversion. The principal products being dichloroethylene (C{sub 2}H{sub 2}Cl{sub 2}) and HCl. 5 refs., 1 tab
Recommended from our members
Design of the CART data system for the US Department of Energy's ARM Program
The Department of Energy (DOE) has initiated a major atmospheric research effort to reduce the uncertainties found in general circulation and other models due to the effects of clouds and radiation. The objective of the Atmospheric Radiation Measurement Program (ARM) is to provide an experimental testbed for the study of important atmospheric effects, particularly cloud and radiative processes, and testing parameterizations of the processes for use in atmospheric models. This experimental testbed, known as the Clouds and Radiation Testbed (CART), will include a complex data system, the CART Data Environment (CDE). The major functions of the CDE will be to: acquire environments from instruments and external data sources; perform quality assessments of the data streams; create data streams of known quality to be used as model input compared to model output; execute the models and capture their predictions; and make data streams associated with model tests available to ARM investigators in near real-time. The CDE will also be expected to capture ancillary information ( meta-data'') associated with the data streams, provide data management facilities for design of ARM experiments, and provide for archival data storage. The first section of this paper presents background information on CART. Next the process for the functional design of the system is described, the functional requirements summarized, and the conceptual architecture of the CDE is presented. Finally, the status of the CDE design activities is summarized, and major technical challenges are discussed
Recommended from our members
ENDF/B-VI six-group delayed neutron data
This paper evaluates ENDF/B-VI delayed neutron data for {sup 235}U, {sup 238}U, and {sup 239}Pu. (LSP
Recommended from our members
Fission product plateout and liftoff in the MHTGR primary system: A review
A review is presented of the technical basis for predicting radioactivity release resulting from depressurization of an MHTGR primary system. Consideration is restricted to so called dry events with no involvement of the steam system. The various types of deposition mechanisms effective for iodine, cesium, strontium, and silver are discussed in terms of their chemical characteristics and the nature of the materials in the primary system. Emphasis is given to iodine behavior, including means for estimating the quantity available for release, the types of plateout locations in the primary system, and the effect of dust on distribution and release. The behavior of fission products cesium, strontium, and silver in such accidents is presented qualitatively. A major part of the review deals with expected dust levels, types, and transport. Available information on the level and nature of dust in the HTGR primary system is reviewed. A summary is presented of dust deposition and liftoff mechanisms. It was concluded that recent approaches to dust liftoff modeling, based on turbulent burst concepts for removal from surfaces, probably offer advantages over the current shear ratio approach. This study concludes that iodine releases from dry depressurization events are likely to be extremely low, on the order of millicuries, due to a predictably low degree of chemical desorption, a low degree of dust liftoff, and a low involvement of iodine with dust. It was also concluded that deposition mechanisms controlling the distribution of fission product material in the primary system, and hence also controlling the degree of liftoff, depend strongly on the chemical nature of the individual elements. Therefore contrary to the current practice, both plateout and liftoff models should reflect those unique chemical and physical properties. 56 refs., 16 figs., 23 tabs
Recommended from our members
A review of activation cross sections in the ENDF/B-VI general purpose files for Cr, Fe, Ni, Cu, and Pb
Isotopic evaluations for {sup 50,52,53,54}Cr, {sup 54,56,57,58}Fe, {sup 58,60,61,62,64}Ni, {sup 63,65}Cu, and {sup 206,207,208}Pb are included in ENDF/B-VI for the first time. These general purpose files, all by the ORNL evaluation group, include many activation cross sections. In this review, the 34 activation reactions for these materials in the priority-I CSEWG list were checked for their presence and contents in the general purpose files. These cross sections are reviewed in terms of the experimental data base and the evaluation methods. Most of them have been significantly improved over ENDF/B-V through the improved data base and the use of advanced codes such as SAMMY for resonance analysis, GLUCS for handling ratio data and covariances, and TNG for cross-section shape and for extracting individual cross sections from the measured particle spectrum. 18 refs., 1 fig., 1 tab
Recommended from our members
DOE mixed wastes: What are they and where can thermal technologies be applied
The Mixed Waste Treatment Project (MWTP) has collected and analyzed mixed low-level waste data to assist in developing treatment capability for the US Department of Energy is (DOE) wastes. Initial data on the characteristics of mixed waste was obtained from the Waste Management Information System (WMIS) data base, and has been updated based on visits to DOE sites where most of the wastes are generated and stored. The streams of interest to the MWTP have a current inventory of about 70,000 m[sup 3] and a generation rate of about 7,700 m[sup 3]/yr. The 12 sites with the most significant processing needs are Fernald, Hanford, K-25 (Oak Ridge), Idaho National Engineering Laboratory (INEL), Lawrence Livermore National Laboratory (LLNL), Los Alamos National Laboratory (LANL), Oak Ridge National Laboratory (ORNL), Paducah Gaseous Diffusion Plant, Portsmouth Gaseous Diffusion Plant, Rocky Flats Plant (RFP), Savannah River Site (SRS), and Y-12 (Oak Ridge). These 12 sites account for about 98% of the mixed waste volumes. The wastes have been assigned to specific waste characterization categories and a flowsheet that identifies applicable technologies has been developed. The largest waste stream category, when considering the current inventory in storage, is inorganic solids, with sludges, filter cakes, and residues the largest specific subcategories. Aqueous liquids are the largest currently generated stream. The other large categories are solid organics, metals wastes, and heterogenous wastes. Organic liquids, which have been a major focus, are the smallest of the categories. The major thermal treatment units include evaporators, incinerators, vitrifiers, metal melters, and off-gas treatment systems
Recommended from our members
Damping the transverse resistive wall instability in the AGS Booster
A transverse bunch-to-bunch feedback system will be installed on the AGS Booster to suppress coherent coupled bunch oscillations driven by the resistive wall impedance of the vacuum chamber when accelerating high intensity proton beams (circulating currents > 3 amp). It is possible to estimate the expected growth rate of the instability by scaling from the machine parameters and measurements made on the AGS. An upper limit of 1.5 {times} 10{sup 3} sec{sup {minus}1} at 1.5 GeV kinetic energy with {Chi} = 0 and 0.5 {times} 10{sup 13} protons/bunch is obtained for the vertical plane. The position signal of each bunch (h = 3), at two locations separated by one quarter of a betatron wavelength, will be integrated, digitized and stored in a memory whose clock is synchronized with the acceleration frequency. This pair of inputs will be used in conjunction with look up tales, which will be related to a given range of the tune Q, to generate the proper correction amplitude. This will then be D/A converted, amplified and applied to 50{Omega} traveling wave kickers. The overall time delay will be adjusted to equal or revolution periods in order to permit the necessary digital signal processing (T{sub o} = 0.73 {mu}s at {gamma} = 2.6). An analysis of the performance of this and similar systems for within the bunch modes m = 0, 1 and both zero and non-zero head tail phase shift {Chi} will be presented. 4 refs., 1 fig
Recommended from our members
The advanced neutron source--designing to meet the needs of the user community
The Advanced Neutron Source (ANS) is to be a multi-purpose neutron research center, constructed around a high-flux reactor now being designed at the Oak Ridge National Laboratory (ORNL). Its primary purpose is to place the United States in the forefront of neutron scattering in the twenty-first century. Other research programs include nuclear and fundamental physics, isotopes production, materials irradiation, and analytical chemistry. The Advanced Neutron Source will be a unique and invaluable research tool because of the unprecedented neutron flux available from the high intensity research reactor. But that reactor would be ineffective without world-class research facilities that allow the fullest utilization of the available neutrons. And, in turn, those research facilities will not produce new and exciting science without a broad population of users coming from all parts of the nation, and the world, placed in a simulating environment in which experiments can be effectively conducted, and in which scientific exchange is encouraged. This paper discusses the measures being taken to ensure that the design of the ANS focuses not only on the reactor, but on providing the experiment and user support facilities needed to allow its effective use. 5 refs., 4 figs
Recommended from our members
Evaluation of shielding analysis methods for spent fuel casks
Accurate results from shielding analyses of spent fuel casks are increasingly important as the desire for optimized designs increases. ALARA concerns also contribute to the need for accurate dose evaluations for casks. Three areas require the attention of cask shielding analysts --- radiation source generation, utilization of cross-section data, and the radiation transport and dose evaluation. This paper reviews recent efforts carried out at Oak Ridge National Laboratory (ORNL) to evaluate the impact of various codes, data, and analysis assumptions on the calculation of radiation doses from spent fuel casks. 9 refs., 1 tab
- …