23 Matching Results

Search Results

Advanced search parameters have been applied.

UV-Shifted Durable Silver Coating for Astronomical Mirrors

Description: Silver has the highest reflectance of all of the metals, but it tarnishes in the presence of sulfides, chlorides, and oxides in the atmosphere. Also, the silver reflectance is very low at wavelengths below 400 nm making aluminum more desirable mirror coating for the UV region. They have found a way to prevent silver tarnishing by sandwiching the silver layer between two thin layers of NiCrN{sub x}, and to extend the metal's high reflectance down to 200 nm by depositing the (thin) Ag layer on top of Al. Thus, the uv is transmitted through the thin Ag layer below 400 nm wavelength, and is reflected from the Al layer underneath. This UV-shifted durable coating provides a valuable alternative to the aluminum coating for telescope mirror coatings where high throughput and durability are important considerations. The throughput for a telescope with, say, six reflections from silver coatings is (0.97){sup 6} = 83% compared to (0.92){sup 6} = 60% for aluminum coatings, or 28% less. The use of silver coatings allows more photons to be collected by primary mirror. Aluminum also has a reflectance dip at 850 nm caused by inter-band transitions which is eliminated by placing the thin Ag layer on top. This paper describes a non-tarnishing silver coating having high reflectance down into the UV region. The average specular reflectance is 70%-97% in the near-UV, 95%-99% in the visible region, and {ge} 99% in the infrared region covering the total wavelength range 200 nm to 10,000 nm. Figure 1 compares the reflectance of the UVHR-LLNL silver coating to bare silver and aluminum over-coated with magnesium fluoride over the wavelength range 300 nm to 2000 nm.
Date: June 1, 2000
Creator: Thomas, N.L. & Wolfe, J.
Partner: UNT Libraries Government Documents Department

STUDIES RELATING TO HYDROGEN IN DINGOT URANIUM

Description: The distribution of H/sub 2/ among feed materials and products in the thermite reaction producing dingot U was studied. The H/sub 2/ content of Mg, molten U, and molten and solid MgF/sub 2/ density oxide to 98 to 99% for the high specific surface, ow bulk density oxides. The observed values for properties of the U/sub 3/O/sub 8/ samples correlated better with conversion of U/ sub 3/O/sub to UF/sub 4/ than did the observed values for properties of the corresponding UO/sub 2/ intermediates. (auth)
Date: September 20, 1957
Creator: Trzeciak, M.J. & Mallett, M.W.
Partner: UNT Libraries Government Documents Department

SEPARATION OF TECHNETIUM-99 FROM URANIUM HEXAFLUORIDE

Description: A system is described for recovery of Tc from UF/sub 6/ in a UO/sub 3/ fluorination plant. The Tc is retained on MgF/sub 2/ in traps through which the UF/sub 6/ stream is passed. The system is in operation at the Paducah Gaseous Diffusion Plant. (J.R.D.)
Date: January 1, 1963
Creator: Golliher, W.R.; LeDoux, R.A.; Bernstein, S. & Smith, V.A.
Partner: UNT Libraries Government Documents Department

Report on the Study of Radiation Damage in Calcium Fluoride and Magnesium Fluoride Crystals for use in Excimer Laser Applications

Description: A study was performed to investigate the effects of radiation damage in calcium fluoride and magnesium fluoride crystals caused by gamma rays and UV photons from excimer lasers. The purpose was to study and correlate the damage caused by these two different mechanisms in various types of material used for fabricating optical elements in high power excimer lasers and lens systems of lithography tools. These optical systems are easily damaged by the laser itself, and it is necessary to use only the most radiation resistant materials for certain key elements. It was found that a clear correlation exists between the, radiation induced damage caused by high energy gamma rays and that produced by UV photons from the excimer laser. This correlation allows a simple procedure to be developed to select the most radiation resistant material at the ingot level, which would be later used to fabricate various components of the optical system. This avoids incurring the additional cost of fabricating actual optical elements with material that would later be damaged under prolonged use. The result of this screening procedure can result in a considerable savings in the overall cost of the lens and laser system.
Date: October 4, 1999
Partner: UNT Libraries Government Documents Department

Thermodynamics of the conversion of calcium and magnesium fluorides to the parent metal oxides and hydrogen fluoride

Description: The authors have used thermodynamic modeling to examine the reaction of calcium fluoride (CaF{sub 2}) and magnesium fluoride (MgF{sub 2}) with water (H{sub 2}O) at elevated temperatures. The calculated, equilibrium composition corresponds to the global free-energy minimum for the system. Optimum, predicted reaction temperatures and reactant mole ratios are reported for the recovery of hydrogen fluoride (HF), a valuable industrial feedstock. Complete conversion of MgF{sub 2} is found at 1,000 C and a ratio of 40 moles of H{sub 2}O per 1 mole of MgF{sub 2}. For CaF{sub 2}, temperatures as high as 1,400 C are required for complete conversion at a corresponding mole ratio of 40 moles of H{sub 2}O per 1 mole of CaF{sub 2}. The authors discuss the presence of minor chemical constituents as well as the stability of various potential container materials for the pyrohydrolysis reactions at elevated temperatures. CaF{sub 2} and MgF{sub 2} slags are available as wastes at former uranium production facilities within the Department of Energy Complex and other facilities regulated by the Nuclear Regulatory Commission. Recovery of HF from these wastes is an example of environmental remediation at such facilities.
Date: February 1, 1997
Creator: West, M.H. & Axler, K.M.
Partner: UNT Libraries Government Documents Department

Laser-induced damage in dielectrics with nanosecond to subpicosecond pulses. II. Theory

Description: The authors have reported extensive measurements of damage thresholds for fused silica and several fluorides (LiF, CaF, MgF, and BaF) at 1053 and 526 nm for pulse durations, {tau}, ranging from 275 fs to 1 ns. A theoretical model based on electron production via multiphoton ionization, Joule heating, and collisional (avalanche) ionization is in good agreement with experimental results.
Date: December 1, 1994
Creator: Feit, M.D.; Rubenchik, A.M. & Shore, B.W.
Partner: UNT Libraries Government Documents Department

Neutron study of fracton excitations in percolating antiferromagnets

Description: The authors report the results of an inelastic neutron scattering experiment on nearly-percolating Heisenberg antiferromagnets (RbMn{sub c}Mg{sub 1{minus}o}F{sub 3}), in which the Mn concentrations (C = 0.31, 0.34 and 0.39) are very close to the percolation threshold (c{sub p} = 0.312). A broad peak superimposed on Ising-cluster excitations was observed throughout the Brillouin zone. The intensity of a broad peak increased on approaching the percolation threshold. The origin of this broad peak is attributed to the excitation of fractons in a percolating network.
Date: June 27, 1997
Creator: Ikeda, H.; Takahashi, M.; Fernandez-Baca, J.A. & Nicklow, R.M.
Partner: UNT Libraries Government Documents Department

An introduction to technetium in the gaseous diffusion cascades

Description: The radioisotope technetium-99 ({sup 99}Tc) was introduced into the gaseous diffusion plants (GDP) as a contaminant in uranium that had been reprocessed from spent nuclear reactor fuel. {sup 99}Tc is a product of the nuclear fission of uranium-235 ({sup 235}U). The significantly higher emitted radioactivity of {sup 99}Tc generates concern in the enrichment complex and warrants increased attention (1) to the control of all site emissions, (2) to worker exposures and contamination control when process equipment requires disassembly and decontamination, and (3) to product purity when the enriched uranium hexafluoride (UF{sub 6}) product is marketed to the private sector. A total of 101,268 metric tons of RU ({approximately}96% of the total) was fed at the Paducah Gaseous Diffusion Plant (PGDP) between FY1953 and FY1976. An additional 5600 metric tons of RU from the government reactors were fed at the Oak Ridge Gaseous Diffusion Plant (ORGDP), plus an approximate 500 tons of foreign reactor returns. Only a small amount of RU was fed directly at the Portsmouth Gaseous Diffusion Plant (PORTS). The slightly enriched PGDP product was then fed to either the ORGDP or PORTS cascades for final enrichment. Bailey estimated in 1988 that of the 606 kg of Tc received at PGDP from RU, 121 kg was subsequently re-fed to ORGDP and 85 kg re-fed to PORTS.
Date: September 1, 1996
Creator: Simmons, D. W.
Partner: UNT Libraries Government Documents Department

Amorphous silicon research: Phase II. Annual technical progress report, August 1, 1995--July 31, 1996

Description: This report describes the research performed during Phase II of a three-phase, three-year program under NREL Subcontract No. ZAN-4-13318-02. The research program is intended to expand, enhance and accelerate knowledge and capabilities for the development of high-performance, two-terminal multijunction hydrogenated amorphous silicon (a-Si:H) alloy modules. It is now well recognized that a multifunction, multibandgap approach has the potential of achieving the highest stable efficiency in a-Si:H alloy solar cells. In this approach, the bandgap of the materials of the component cell is varied in order to capture a wide spectrum of the solar photons. Significant progress has been made in the development of materials and cell design in the last few years, and a stable module efficiency of 10.2% has been demonstrated over one-square-foot area using a triple-junction approach in which the bottom two component cells use hydrogenated amorphous silicon-germanium (a-SiGe:H) alloy. In order to meet the Department of Energy goal of achievement of 12% stable module efficiency, it is necessary to make further improvements in each of the component cells. This has been the thrust of the current program.
Date: October 1, 1996
Creator: Guha, S.
Partner: UNT Libraries Government Documents Department

The Precipitation of Uranium Peroxide in the Presence of Fluorides

Description: The large-scale recovery of uranium from materials which also contained great quantities of fluorides did not give a product which had a low enough fluoride content to be treated satisfactorily by the other extraction process. The objective of the investigations carried out in this laboratory was a method of reducing the amount of fluoride which accompanied the uranium. The material from which the uranium was recovered in the industrial process was a slag containing (in addition to uranium) magnesium fluoride, calcium and dolomitic lines, crucible dross, and other waste products from the reaction of magnesium metal and uranium hexafluoride. Most of the fluoride was removed from this mixture by heating the roasted and ground slag with sulfuric acid. The residue was mixed with water and much of the caclium sulfate and fluoride, magnesium fluoride, and hydrated ferric oxide and alumina was precipitated by reducing the acidity. After filtering off the precipitate, ammonium sulfate was added to the solution and uranium peroxide (UO{sub 4} {center_dot} 2H{sub 2}O) was precipitated by addition of hydrogen peroxide. The pH of the solution was maintained between 3.0 and 3.5 during the precipitation by addition of sodium hydroxide. The uranium peroxide, even after washing, contained between 2 and 3% fluoride. The percentage of fluoride could be reduced to 0.5% by precipitating the peroxide from a more acidic solution but this required the use of much larger amounts of hydrogen peroxide.
Date: January 1, 1941
Creator: King, Edward J.
Partner: UNT Libraries Government Documents Department

Reduction of Glass Surface Reflectance by Ion Beam Surface Modification

Description: This is the final report for DOE contract DE-EE0000590. The purpose of this work was to determine the feasibility of the reduction of the reflection from the front of solar photovoltaic modules. Reflection accounts for a power loss of approximately 4%. A solar module having an area of one square meter with an energy conversion efficiency of 18% generates approximately 180 watts. If reflection loss can be eliminated, the power output can be increased to 187 watts. Since conventional thin-film anti-reflection coatings do not have sufficient environmental stability, we investigated the feasibility of ion beam modification of the glass surface to obtain reduction of reflectance. Our findings are generally applicable to all solar modules that use glass encapsulation, as well as commercial float glass used in windows and other applications. Ion implantation of argon, fluorine, and xenon into commercial low-iron soda lime float glass, standard float glass, and borosilicate glass was studied by implantation, annealing, and measurement of reflectance. The three ions all affected reflectance. The most significant change was obtained by argon implantation into both low-iron and standard soda-lime glass. In this way samples were formed with reflectance lower than can be obtained with a single-layer coatings of magnesium fluoride. Integrated reflectance was reduced from 4% to 1% in low-iron soda lime glass typical of the glass used in solar modules. The reduction of reflectance of borosilicate glass was not as large; however borosilicate glass is not typically used in flat plate solar modules. Unlike conventional semiconductor ion implantation doping, glass reflectance reduction was found to be tolerant to large variations in implant dose, meaning that the process does not require high dopant uniformity. Additionally, glass implantation does not require mass analysis. Simple, high current ion implantation equipment can be developed for this process; however, before the process can ...
Date: March 11, 2011
Creator: Spitzer, Mark
Partner: UNT Libraries Government Documents Department

RESIN ATTRITION

Description: ABS>Uranium metal is produced by the bomb reduction of UF/sub 4/ with Mg. The slag from this reduction contains appreciable quantities of U, either in the metallic or the tetrafluoride form, in addition to the MgF/sub 2/. A process for recovering low enrichmeat U from this slag has gone into operation. A study of the causes of resin attrition and their relative magnitude both from an over-all point of view and with specific reference to the Higgins' Column and Dowex 21K resin is preseated. Equipment was designed, assembled, and tested to investigate the effects of valve action, wall to resin and resin to resin friction, repeated chemical cycling, and column height. Certain mechanical properties of the resin beads were investigated, and some existing plant data were analyzed. A discussion of the probable mechanism of attrition and its contribution to the overall amount of attrition is presented. (W.L.H.)
Date: April 1, 1958
Creator: Seiler, G.R.; Ammann, P.R. & Newey, A.B.
Partner: UNT Libraries Government Documents Department

URANIUM RECOVERY FROM COMPOSITE UF$sub 4$ REDUCTION BOMB WASTES

Description: A number of techniques have been investigated on a laboratory-scale for separating uranium from fluorides during the recovery of uranium from UF4 reduction bomb wastes (C-oxide) by an HCl leach - NH4OH precipitation process. Among these are included adsorption of fluorides from filtered leach liquors, fractional precipitation of fluorides and uranium, complexing of fluorides into forms soluble in slightly acid solutions, and fluoride volatilization from the uranium concentrate. Solubility studies of CaF2 and MgF2 in aqueous hydrochloric acid at various acidities and temperatures were also conducted. A description of the production-scale processing of C-oxide in the FMPC scrap plant has been included.
Date: January 28, 1954
Creator: Johnson, E R; Doyle, R L; Coleman, J R; Kreuzmann, A B; Rutenkroger, E O & Malotte, W H
Partner: UNT Libraries Government Documents Department

PROCESS DEVELOPMENT QUARTERLY REPORT. PART I

Description: Progress is preserted on studies of the Waxco process, new raw materials, high (NH/sub 4/)/sub 2/Csub 2/O/sub 4/ insoluble in MCW UF/su b 4/, recovery of HF and U from MgF/sub 2/ bomb slag, study of U metal with respect to metal quality, C contamination in cast U, vacuum fusion 0 determination, pyroelectric con centration methods for improving B sensitivity, grinding sample preparations for spectrographic analysis, and determination of N in U metal. (For preceding report see NYO-1353). (M.C.G.)
Date: July 15, 1953
Creator: Ruehle, A.E. & Shepardson, J.U. et al.
Partner: UNT Libraries Government Documents Department

Reduction of Uranium Hexafluoride Retention on Beds of Magnesium Fluoride Used for Removal of Technetium Hexafluoride

Description: The excessive loss of uranium incurred when discarding magnesium fluoride, (the adsorber used to selectively remove technetium hexafluoride from uranium hexafluoride streams) is a problem common to all volatility processes for recovering enriched uranium fuels. As a result of the work described, two schemes for the release of the uranium hexafluoride from the magnesium fluoride and its separation from the technetium hexafluoride are proposed. One scheme depends on preferential thermal desorption of the uranium hexafluoride at 350 deg C and the other on selective adsorption of the uranium hexafluoride on sodium fluoride pellets following the codesorption of the two hexafluorides with fluorine at 500 deg C from the magnesium fluoride pellets. These proposals are aimed at reducing the amount of retained uranium to less than 1 g per 1000 g of discardable magnesium fluoride. In the work reported, the deposition of uranium on magnesium fluoride as a function of heating, fluorination, and hydrogen fluoride pretreatment of the magnesium fluoride pellets prior to exposure to uranium hexafluoride was characterized in a series of gasometric studies. The dependence of the quantity of uranium hexafluoride adsorbed on pressure and temperature was also determined. The data show that physical adsorption is the mechanism for the deposition of most of the uranium hexafluoride on well- stabilized magnesium fluoride pellets. More than 90% of the adsorbate can be removed by heating to 350 deg C. Chemisorption (formation of a double salt) is probably not involved because of the small (<0.05) mole ratio of UF/sub 6//MgF/ sub 2/ observed. (auth)
Date: January 31, 1964
Creator: Katz, S.
Partner: UNT Libraries Government Documents Department

QUARTERLY PROGRESS REPORT FOR THE PERIOD ENDING JUNE 30, 1954

Description: Chemistry of Feed Materials. Studies were made of the first step in the reduction of UO/sub 3/ to UO/sub 2/. The rates of reduction of pelleted- hydrated and pelleted-dehydrated UO/sub 3/ to U/sub 3/O/sub 8/ in steam were determined. The rates of reduction of pelleted U/sub 3/O/sub 8/ to UO/sub 2/ in 1-to-1 ammonia-steam were determined. Some preliminary measurements were made on the thermal conductivities of hydrated and dehydrated UO/sub 3/ wafers. Purification of Th(NO/sub 3/)/sub 4/ for spectrographic standards is described. Uranium was extracted from MgF/sub 2/ slag with an aqueous solution of sodium carbonate --bicarbonate using 0/sub 2/ at 30 psi as an oxidant. The conversion of thorium benzoate to ThCl/sub 4/ was carried out with HCl in ether. Dimethyl ether was prepared by the catalytic dehydration of methanol. The processing of UO/sub 3/ containing As contamination is described. Metallurgical Investigations. A process for stripping Af and Ni coatings from flat plates is described. Analytical Chemistry. The spectrographic determination of dysprosium and gadolinium in lanthanum oxide matrix--rare earth concentrate is described. (W.L.H.)
Date: July 1, 1954
Creator: Rodden, C.J.
Partner: UNT Libraries Government Documents Department