bluuebunny/crossref_metadata_2025_split huggingface dataset:
Immobilization of Separated Tc and Cs/Sr in Synroc
Authors: Hart K. P. , Vance E. R. , Day R. A. , Begg B. D. , Angel P. J. , Jostsons A. 
Published: April 2011

AbstractIn some radwaste applications, such as immobilization of U.S. Tank wastes using vitrification, Tc and Cs/Sr are likely to be separated out from HLW supernates. Simplified Synroc preparations can be devised for the immobilization of separated Tc and Cs/Sr, either together or individually. Under suitably reducing processing conditions, Tc can be immobilized, as metal or Tc4+. The volatility of Tc and Cs/Sr in Synroc processing is very restricted.In Synroc-C, designed for Purex high-level reprocessing wastes, Tc exists as a metal alloy. In air-saturated water, normalized MCC-1 type total differential leach rates at 90°C decreased with leaching time and after 90 days were <10-4 g/m2/d, decreasing by a factor of ∼100 in anoxic conditions. The corresponding results in a pH=6.1 buffer solution were fairly similar to those in deionised water, but in anoxic conditions, the leach rates were higher in the buffer solution than in the deionised water.A single perovskite phase was loaded with ∼40 wt% of TcO2 to form CaTc0.5Ti0.5O3 by a combination of graphite-die hot-pressing and heating in argon. Rutile, intended to be doped with ∼35wt% TcO2, was fabricated by bellows hot-pressing at 1200°C; aproximately 75% of the Tc formed a solid solution with rutile, but some metallic Tc was also present due to imperfect redox control. Results of both MCC-1 and PCT-type leach tests are presented on a preparation containing 70 wt% hollandite + 20 wt% perovskite + 10 wt% rutile containing about 5 wt% of Cs and Sr respectively. Phase distributions resulting from incorporating Cs and Sr in Synroc-B precursor were studied.
Hot Isostatic Press (Hip) Vitrification of Radwaste Concretes
Authors: Siemer Darryl D. , Scheetz Barry E. , Gougar Mary Lou 
Published: April 2011

AbstractProperly prepared cementitious waste forms can be hot-isostatically-pressed into materials that exhibit performance equivalent to typical radwaste-type glasses. The HIPing conditions (temperature/pressure) required to “vitrify” these concretes are quite mild and therefore consistent with both safety and good productivity. This paper describes both the process and its products with reference to potential application to Idaho Chemical Processing Plant (ICPP) reprocessing wastes.
The Necessity for Scale Up in R&D: Approach for Waste Immobilisation in Cement by BNFL
Authors: Fairhall Graham A , Miller Eric W 
Published: April 2011

AbstractThe full scale processing of nuclear wastes immobilised in cement utilises a wide range of chemical and physical parameters. The success of this work however, involves many factors and material properties which are affected by the actual scaling up processes. The paper outlines the approach and experience gained by BNFL to recognise and evaluate the major factors involved in order to successfully produce large scale stable products acceptable to the appropriate regulatory bodies and suitable for long term disposal.
Migration of Solutes in Unsaturated, Fractured Rock at Yucca Mountain: Measurements, Mechanisms, and Models
Authors: Wolfsberg A. V. , Robinson B. A. , Fabryka-Martin J. T. 
Published: April 2011

AbstractCharacterization and performance assessment (PA) studies for the potential high-level nuclear waste repository at Yucca Mountain require an understanding of migration mechanisms and pathways of radioactive solutes. Measurements of 36C1 in samples extracted from boreholes at the site are being used in conjunction with recent infiltration estimates to calibrate a site-scale flow and solute transport model. This exercise using the flow and solute transport model, FEHM, involves testing different model formulations and two different hypotheses to explain the occurrence of elevated 36Cl in the Calico Hills unit (CHn) which indicates younger water than in the overlying Topopah Spring unit (TSw). One hypothesis suggests fast vertical transport from the surface via fractures in the TSw to the CHn. An alternative hypothesis is that the elevated 36C1 concentrations reflect rapid horizontal flow in the CHn or at the interface between the CHn and the TSw with the source being vertical percolation under spatially isolated regions of high infiltration or at outcrops of those units. Arguments in favor of and against the hypotheses are described in conjunction with the site-scale transport studies.
The Release of Cesium and the Actinides from Spent Fuel Under Unsaturated Conditions
Authors: Finn P. A. , Hoh J. C. , Wolf S. F. , Slater S. A. , Bates J. K. 
Published: April 2011

AbstractTests designed to be similar to the unsaturated and oxidizing conditions expected in the candidate repository at Yucca Mountain are in progress with spent fuel at 90°C. The similarities and the differences in release behavior for 137Cs during the first 2.6 years and the actinides during the first 1.6 years of testing are presented for tests done with (1) water dripped on the fuel at a rate of 0.075 and 0.75 mL every 3.5 days and (2) in a saturated water vapor environment.
A Natural Analogue Study of Uranium Migration in the Tono Mine
Authors: Clark K. J. , Takase H. , Impey M. D. , Humm J. P. , Maekawa K. , Ogata N. , Yanaegizawa K. 
Published: April 2011

AbstractThe Tono uranium mine in Japan, consists of a granite basin infilled with layered marine sedimentary rocks, within which uranium is heterogeneously distributed. This site is being used as a natural analogue to study the migration of uranium. The irregular observed uranium distribution had not satisfactorily been explained by local geochemical properties. This paper examines the hypothesis that the distribution of uranium could be dominated by the accessibility of locations to the migrating uranium, i.e. by the heterogeneous hydrology of the site.High resolution heterogenous transmissivity fields were generated, conditioned on data from four boreholes through the mine. Steady state Darcy flow calculations and particle tracking simulations of uranium migration have been carried out. The time dependent relative intensity of a set of sources on the boundary of the modelled region were used as parameters to fit the modelled uranium distribution to the observed.The relative intensities so obtained could be interpreted in a physically reasonable way. Good qualitative agreement was achieved between the observed heterogenous irregular uranium distribution and that fitted. We conclude that this supports the hypothesis, and that detailed knowledge of channelling flows can provide a better understanding of possible radionuclide dispersal.
Ion Exchange and Dehydration Effects on Potassium and Argon Contents of Clinoptilolite
Authors: Woldegabriel G. , Levy S. 
Published: April 2011

AbstractZeolite-rich Miocene tuffs are an important part of the principal hydrochemical barrier to water-borne radionuclide transport from a potential high-level nuclear waste repository at Yucca Mountain, Nevada. The timing of zeolitization is an issue that relates to paleohydrology, permeability, zeolite stability, and unsaturated-zone geochemical processes. Exploratory K/Ar dating of clinoptilolite, the most abundant and widespread zeolite, shows a striking and consistent pattern of increasing apparent ages (2–13 Ma) with depth. Only the isotopic ages from the saturated zone are compatible with geologic evidence suggesting an age >10 Ma for most of the zeolites.Factors that may be responsible for the young apparent ages in the unsaturated zone were investigated. Cation exchange with recharge water and Ar diffusion under unsaturated conditions (processes that may be characteristic of the unsaturated zone) were evaluated experimentally for their effects on K/Ar systematics. Cation exchanging a natural clinoptilolite with Ca-, Cs-, K-, and Na-chloride solutions showed minimal effects on radiogenic Ar content. However, clinoptilolite heated at 2007deg;C for 16 hours in air lost a significant amount of its radiogenic Ar compared with minimal losses from clinoptilolite heated in water at 100°C for over 5 months. The preliminary results indicate that Ar loss from incompletely hydrated clinoptilolite may be a major factor contributing to the young apparent ages of clinoptilolite in the unsaturated zone at Yucca Mountain.
Applications of Electro-optic Polymers in Photonics
Authors: Steier William H. , Kalluri Srinath , Chen Antao , Garner Sean , Chuyanov Vadim , Ziari Mehrdad , Shi Yongqiang , Fetterman Harold , Jalali Bahram , Wang Wenshen , Chen Datong , Dalton Larry R. 
Published: April 2011

ABSTRACTThis review gives a summary of our research in the applications of EO polymers for very broad band infrared modulators, in solving some of the initial problems one faces in integrating semiconductor electronics and EO polymers, and in the fabrication of low loss infrared waveguides.
Nlo Polymer Material Systems for Electro-Optic Devices
Authors: Kenney J. T. , Nurse J. C. , Chon J. C. , Binidey E. S. , Stiller M. , Ball D. W. , Jen A. K-Y. 
Published: April 2011

ABSTRACTNon linear optical (NLO) polymers have great potential to be fabricated into integrated electro-optic (E/O) devices for use as high speed electro-optic (E/O) switches, modulators and interconnects in computer and communication systems [1,2]. The fabrication of practical integrated E/O devices requires a material system that meets the final device requirements and can be processed using standard fabrication technologies [3]. Applications of polymer E/O devices in electronic systems have been limited by the relatively low thermal stability and poor processability of non linear optical (NLO) polymers. This paper describes a thermally stable electro-optic material system and the fabrication process to make compact integrated E/O devices for application in electronic systems. This material system consists of high thermal stability polyimide core and cladding materials. The active NLO material is a side chain polyimide that uses a new high activity and high thermal stability chromophore.
Multiphasic Nanostructured Composites for Photonics
Authors: Prasad P. N. , Gvishi R. , He G. S. , Bhawalkar J. D. , Kumar N. D. , Ruland G. , Zhao C. F. , Reinhardt B. A. 
Published: April 2011

ABSTRACTThe realization of photonics technology rests on the development of multifunctional materials, which simultaneously satisfy many functional requirements. Towards this goal, we present here, the preparation of novel multifunctional nanostructured composites using the sol-gel process. Two specific applications: optical limiting, and two-photon pumped lasing in these composite materials will be discussed.We have been able to dope two optical limiting materials in a single bulk and retain the optical limiting effects at each of their characteristic wavelengths. The materials selected for this purpose were C60 which shows optical limiting behavior at a wavelength of 532 nm and bisbenzothiazole 3,4-didecyloxy thiophene (BBTDOT) which exhibits a strong two-photon absorption induced optical limiting at 800 nm. The resulting glass acts as a multi-wavelength optical limiter.In addition, we present results of two-photon pumped upconverted lasing at 600 nm in a nanostructured composite glass doped with a new dye, trans-4-[P-(N-ethyl-Nhydroxylethylamino) styryl]-N-methylpyridinium tetraphenylborate (ASPT). The pump source was a Q-switched Nd:YAG laser producing 1064 nm pulses of ˜ 10 ns duration.
Polyamic Acid Langmuir-Blodgett (LB) Films Containing A Stable Second-Order NLO Chromophore
Authors: Cheong D. W. , Chen J. -I , Kumar J. , Tripathy S. K. 
Published: April 2011

ABSTRACTNonlinear optical (NLO) LB films of polyamic acid containing a stable NLO dye were prepared and imidized either chemically or thermally. The optical properties and molecular orientation of these LB films were studied. From the absorption spectra, we infer that the derivative of the pnitroazobenzene chromophore covalently attatched to polyamic acid did not show significant aggregation. Quadratic dependence of SHG on the number of layers in polyamic acid films indicated the noncentrosymmetric organization of polar NLO chromophores. A second-order nonlinear coefficient (d33) of 23.4 pm/V was observed at 1064 nm after absorption correction. In polyimide films, SH intensity was dramatically reduced due to the collapse of the layered structure upon imidization process. In-plane isotropy of the LB films of polyamic acid and polyimide were lost upon irradiation of polarized light.
Surface Enhanced Raman Spectroscopy Of AgTCNQ Formed From Ag Micellar And Inverse Micellar Colloidal Systems
Authors: Ong Ivan W. , Cowan Dwaine O. , Poehler Theodore O. 
Published: April 2011

ABSTRACTSilver Tetracyanoquinodimethane (AgTCNQ) is an organometallic semiconductingcompound with potential for use as an optical memory storage media due to its ability to exist intwo states. A laser Raman system has been proposed for this application as the two states havedistinct Raman vibrational peaks. However, the Raman spectra of bulk AgTCNQ films is veryweak and requires special measures to prevent laser-induced degradation and to ensure adequatesignal to noise ratios. In this paper, we report a synthesis AgTCNQ consisting of AgTCNQnanolayers grown around silver colloidal particles in both water and heptane with the use of theamphiphilic surfactants, AOT and SDS. The Raman scattering of such AgTCNQ systems hasbeen found to be strongly enhanced and far superior to that obtained on bulk AgTCNQ films.We believe that such a system represents a novel and advantageous way of detecting theswitching behavior of AgTCNQ (and other metal-TCNQ compounds) by laser, as Ramanresearch on metal-TCNQ systems has been stymied in the past by poor Raman signals andsusceptibility to laser-induced degradation.
A Study On The Thermal Decomposition of Ba(tmhd)2 and Sr(tmhd)2
Authors: Ryu Hyun-Kyu , Han Jae Hyun , Moon Sang Heup 
Published: April 2011

ABSTRACTDecomposition of Sr(tmhd)2 and Ba(tmhd)2 was investigated by thermogravimetric analysis, in-situ FTIR, and mass spectrometry. Both compounds decomposed following 3 steps: 1) decomposition of the ligands, 2) simultaneous vaporization and partial decomposition of metal-organics, and 3) decomposition of the vaporized metal-organics which existed as the oligomeric species.The Sr source decomposed at lower temperatures and in a narrower temperature range than the Ba source. Also, the gaseous oligomeric species from the Sr source decomposed relatively quickly while the corresponding species from the Ba source decomposed slowly over a long period. Such a difference between the two compounds is due to different bond energies between the metal atom and the ligands, as indicated by our FTIR results.
MOCVD of the Blue Electro-luminescent Phosphor CaGa2 S4:Ce from a Liquid Reagent Delivery System
Authors: Moss T.S. , Dye R.C. , Smith D.C. , Samuels J.A. , DelaRosa M.J. , Schaus C.F. 
Published: April 2011

ABSTRACTThe deposition of CaS, Ga2S3, and CaGa2S4:Ce has been accomplished by MOCVD using Ca(tmhd)2, Ga(tmhd)3, and Ce(tmhd)4, with bubblers and with a liquid delivery system to control the flows. Samples were primarily characterized using x-ray fluorescence and electroluminescence measurements of the color and brightness. Deposition using the bubblers showed a definitive relationship between the Ga(tmhd)3 bubbler temperature and the Ga XRF counts. The Ca conversion shows a tenuous relationship with the Ca(tmhd)2 bubbler temperature, but the scatter of the data makes determining a correlation impractical. Use of the liquid delivery system is preferred to the bubblers because it delivered a reliable reagent flow without the same problems of degradation of the reagent over time. Analysis shows the CaS deposition is mass transport limited, while the Ga2S3 is limited by the deposition kinetics. However, application of these mechanisms to the CaGa2S4:Ce deposition system reveals that the CaGa2S4:Ce is independent of its components. Further, the deposition of CaGa2S4:Ce is found to be Ca rich under conditions which leads to low Ga/Ca ratios in the deposited film. This indicates that the conversion of Ca from Ca(tmhd)2 was catalyzed by the slight presence of Ga in the form of CaGa2S4:Ce or Ga2S3 on the surface. The Ca is thought to be deposited as CaS:Ce since there is a shift in the EL color towards green under low Ga/Ca ratios. The Ca conversion is also found to approach values predicted by the CaS deposition mechanism under conditions which lead to high Ga/Ca ratios, implying that excess Ga2S3 is needed for the deposition of CaGa2S4:Ce without any CaS:Ce inclusions.
Room Temperature Deposition of High Dielectric Constant, High Density Ceramic Thin Films
Authors: Chen K. , Nielsen M. , Soss S. , Liu S. , Rymaszewski E.J. , Lu T.-M. 
Published: April 2011

ABSTRACTFuture high-performance integrated circuits and electronic packaging technology require the integration of many passive components, including high storage capacitors, on the systems. Because of the low melting temperature metal lines and polymer dielectrics in these electronic systems, one cannot employ most of the existing high temperature deposition techniques to grow thin film components. In this paper, we will report our recent work on the room temperature deposition of amorphous ceramic thin films, including BaxTi 2−xOy and SiOx, using the newly developed partially ionized beam technique. This technique utilizes a small percent (<3%) of selfions derived from the depositing materials to bombard the surface growth front during deposition. It is shown that a dramatic control of the density (and therefore the leakage current) and uniformity of the film can be achieved using this deposition technique without post annealing. Al or Cu was used as the electrodes in our multilayer MIM (metal-insulator-metal) test structure. As deposited thin film capacitors with a capacitance ranging from 25 to 100 nF/cm 2 have been fabricated with tan δ <0.01, leakage current of <l.μA/cm2 at 0.5 MV/cm, and breakdown field strength of several MV/cm. These ceramic capacitors do not show any dispersion up to 1 GHz.
Diamond Heat Sinks For High Temperature Electronics: Simuilation, And Thermal Analysis
Authors: Strifas Nickolaos , Christou Aris 
Published: April 2011

ABSTRACTperformance that can be achieved by utilizing a diamond heat - sink design which minimizes junction - to - case thermal resistance. Effects of the thermal conductivity of the substrate material, the thermal conductivity of the die attach material, the substrate thickness, and the die attach thickness onl Ihe thermal resistance are addressed. The results indicate that the temperature increase could be 3 to 4 times less with diamond heat-sinks when compared to other materials.
Luminescence Characterization and Application of Diamond
Authors: Zaitsev A. M. , Melnikov A. A. , Denisenko A. V. , Varichenko V. S. , Job R. , Fahrner W. R. 
Published: April 2011

ABSTRACTThe main advantages of stationary luminescence as a characterization technique of diamond are its relatively simple technical realization and a wide information gained on the impuritydefect structure of crystal. The physical reasons of capability of luminescence come from a very high Debye temperature of the diamond crystal, a strong interatomic bonding, and a relatively weak electron-phonon coupling in optical centers. As a result, a majority of optical centers in diamond possess the luminescence spectra with well resolved zero-phonon lines assisted by vibration-related replica, many of them retaining this spectral structure to room temperature and even above. As zero-phonon line spectrum is normally very sensitive to any external forces applied to the crystal (temperature, mechanical stress, magnetic and electrical fields), the optical centers can serve as sensitive markers, providing much information on the state of the didmond lattice surrounding them.The value of the luminescence increases when diamond is characterized as a material for electronic and, particularly, optoelectronic applications. In this area luminescence really proves to be a unique characterization tool giving a direct information on optical and electronic properties (for instance, impurity and defect content, lifetime of charge carriers, efficiency of radiative recombination etc.), to be used in the devices.In this review the basic parameters of the luminescence centers of diamond are considered and discussed from the view-point of the information they provide. Cathodoluminescence of diamond films and ion implanted layers is given as an example of luminescent characterization of diamond. The semiconducting structures with insulating active zones are discussed as a promising application of diamond for light emitting devices operating at high temperatures.
Negative Electron Affinity Effects And Schottky Barrier Height Measurements Of Metals On Diamond (100) Surfaces
Authors: Baumann P. K. , Nemanich R. J. 
Published: April 2011

ABSTRACTIn this study copper and cobalt films have been deposited on natural type IIb single crystal semiconducting diamond (100) surfaces in ultra-high vacuum (UHV). Prior to metal deposition the diamond crystals have been cleaned by a 1150°C anneal in UHV. This treatment resulted in positive electron affinity surfaces. Upon deposition of 2Å of Cu or Co a negative electron affinity (NEA) was observed. Schottky barrier heights of 0.70 eV and 0.35 eV were found for Cu and Co respectively. In-situ Auger electron spectroscopy (AES) was employed to confirm the presence of a metal layer.
Diamond Film CVD Synthesis on Titanium: Experimental Evidence of the Intermediate Phases at the Film/Substrate Interface
Authors: Rossi M. , Terranova M. L. , Sessa V. , Vitali G. 
Published: April 2011

ABSTRACTThe present findings concern the CVD deposition of diamond films on Ti substrates and the presence of a stratification of other various phases (Titanium Carbide, Titanium Hydride and Graphite) through the thickness of the CVD coatings.The reflection high energy electron diffraction (RHEED) technique is mainly used to gain insight into the structure of the various phases generated at the diamond/substrate interface.The experimental results seem to indicate that the structure of the transition layers present at the substrate/film interface play a fundamental role for the control of the heterogeneous nucleation process of the diamond.
Diamond Needles And Tips As Engineered Growth Shapes
Authors: Cherian K. A. , Litster J. , Rudolph V. , White E. T. 
Published: April 2011

ABSTRACTDiamond nucleation and growth by CFD were investigated to examine the possibility of engineering diamond growth shapes for practical applications. The results obtained include the following:a) Evidence supporting certain factors influencing nucleation - useful in controlling nucleation sites and nucleation density.b) Evidence for a double spiral growth mechanism operating on (111) faces under specific conditions - indicates the possibility of a new mechanism operating for diamond growth from the vapour phase, and the possibility of larger growth rates.c) Evidence for the enhanced growth in <100= crystallographic direction on a cubooctahedral crystal and its control by varying the process parameters – thus showing the possibility of obtaining diamond needles and tips as engineered growth shapes, for specific applications.