bluuebunny/crossref_metadata_2025_split huggingface dataset:
Sorption Kinetics of Uranium-238, Neptunium-237, Caesium-134, and Strontium-85 on a Glacial Deposit
Authors: Moyes L.N. , Bunker D.J. , Smith J.T. , Livens F.R. , Hughes C.R. , Hilton J. , Braithwaite A. , Richardson S. 
Published: April 2011

ABSTRACTBatch sorption experiments have been used to assess the sorption behaviour of four radionuclides, important in the context of low-level waste disposal, on a glacial substrate. Data for sorption of 238U, 237Np, 134Cs and 85Sr are compared and agree well with independent studies. A series of well-established kinetic models have been used to describe the individual uptake mechanisms and rate parameters reported. Sorption occurs via both equilibrium and kinetically controlled pathways, with neptunium sorption being under kinetic control to the greatest extent.
A Comprehensive Hydrodynamic Modeling Approach for the Hydrogeological Site Characterization and for Deriving Input to Performance Assessment
Authors: Vinard P. , Vomvoris S. , Marschall P. 
Published: April 2011

ABSTRACTThis paper gives an overview of the numerical models employed for the simulation of ground-water flow at the Wellenberg site, the runs carried out and the kind of products which were specified as results of the modelling calculations. With respect to more conventional modelling approaches, based mainly on fully deterministic and steady-state schemes, this new approach integrates both deterministic and stochastic aspects (hydraulic conductivity distribution, geometry of the fracture network, etc.) in three different groundwater models, accounting for different scale levels. Moreover, this new approach is as close as possible to a realistic representation of the in situ conditions, since it is based on plausible distributions of transmissivity and hydraulic conductivity at all scales and takes the transient nature of flow fully into account. This latter aspect is fundamental since, at Wellenberg, both the underground facilities and a natural head anomaly in the host rock cause pressure disturbance in the flow field. Finally, and because boundary conditions (especially topographic surface and overburden) vary over time, model predictions based on current topography and climatic conditions are of limited duration and hence a validity duration has to be defined.
The Adsorption of Humic Acids and Europium-Humate Colloids Onto Repository Components: Boom Clay, Bentonite, and Fe2O3
Authors: Wei Jiang 
Published: April 2011

ABSTRACTBatch sorption experiments were carried out to investigate the adsorption of humic acids (HA) and Eu-humate colloids onto repository components: Boom clay, bentonite and Fe2O3as a function of pH. The concentration of humic acids is 150 mg/l and the bulk concentration of Eu is 10−6M. Radioactive152Eu was used as a tracer. The adsorption of humic acids onto bentonite and Fe2O3decreased with increasing pH. Humic acids were probably complexed to Al/Fe sites on the adsorbents through COOH and phenolic OH groups. It is difficult to interpret the adsorption of humic acids onto Boom clay because Boom clay itself contains high content of organic matters. The adsorption of Eu-humate colloids onto repository components were performed near neutral pH conditions. Eu was strongly adsorbed by three adsorbents, and pH had little effect on the adsorption in the neutral pH range. The strong complexation of Eu with humic acids did not prevent Eu from being adsorbed. Eu is likely bound to solid surfaces via humic acids. The adsorption of Eu-humate colloids onto mixed adsorbents (Boom clay + bentonite, Boom clay + Fe2O3, bentonite + Fe2O3, and Boom clay + bentonite + Fe2O3) was investigated. Most of Eu-humate colloids was adsorbed by the mixed adsorbents. The desorption of humic acids and Eu from repository components was also examined.
On the Behavior of Uranium Dioxide Toward Aqueous Corrosion: Incidence of Electronic Stopping of Fission Fragments
Authors: Choffel C. , Garrido F. , Thomé L. , Dran J.-C. , Nowickit L. , Turos A. 
Published: April 2011

ABSTRACTThe scenario of spent fuel direct storage in a deep geological repository is currently under consideration in many countries. In this approach the nuclear fuel — mainly uranium dioxide —acts as a first barrier towards fission fragment and actinide release. Although the access of water in such a repository is rather unlikely, evaluating the safety of a disposal requires the knowledge of the mechanisms and kinetics of alteration and dissolution of the nuclear fuel in groundwaters. Despite the fact that the reported litterature on the topic is really extensive, it is still a challenging problem due to the complexity of the system: the used nuclear fuel cannot identify with uranium dioxide itself due to both radiation damage and modification of the matrix composition during reactor operation. Parametric studies in well-defined conditions on simple systems are therefore of prime importance in order to determine the relevant parameters involved in the structural transformations of the uranium-oxygen-water systenL The aim of the present work was to study the incidence of the electronic stopping of fission fragments on the behavior of nuclear fuel towards leaching in deionized water under oxidative conditions. Several features were of special interest: (i) quantification of the damage induced by swift-heavy ion irradiation prior to aqueous corrosion; (ii) stoichiometry and oxygen depth concentration of the alterated surface region; (iii) structural transformation of the crystalline structure induced by incorporation of additional O atoms; (iv) comparison between unirradiated and irradiated samples
Packaging of High Burnup UO2 and MOX Spent Fuel Considering Temperature Restrictions in the Near Field of a Repository
Authors: McGinnes D.F. , Schneider J. W. 
Published: April 2011

ABSTRACTThe direct disposal of spent fuel is one of the options considered in the Swiss high level waste management program. One of the important questions, within this program, is the heat generation from high-burnup UO2and MOX spent fuels. Depending on the repository boundary conditions (e.g. ambient temperatures at depth, thermal properties of the host rock etc.), on the maximum temperatures allowed in the near field and on the heat output of the fuel, it may not always be possible to completely fill the conceptual waste canister. The aim of this paper is to address the potential loading of spent fuel into canisters for different possible repository heat loading restrictions
TEM Study of Neutron Irradiated Synroc
Authors: Smith Katherine L. , Blackford Mark G. , Lumpkin Gregory R. 
Published: April 2011

ABSTRACTSynroc is a candidate waste form for the immobilisation of high level radioactive waste (HLW)[1]. It is polyphase titanate ceramic principally comprised of zirconolite, hollandite perovskite and rutile (nominally CaZrTi2O7, (BaxCsy)[(Ti3+, Al)2x+y(Ti4+)8−2x−y]O16), CaTiO3and TiO2respectively). Waste species substitute into the three former phases. In particular, actinides (ACTs) substitute onto the Ca and Zr sites in zirconolite and the Ca site in perovskite. Consequently over time, these phases will suffer alpha-recoil and alpha particle damage while hollandite and rutile will suffer alpha particle damage. The effect of radiation damage on the structure and consequently on the durability of Synroc's constituent phases is important to predictive modelling of Synroc's behaviour in the repository environment and risk assessment.
Evolution of an Engineered Barrier Under Thermal Gradient During the STRIPA Experiments: Influence of the Clay Texture on the Element Transfers
Authors: Pozo C. , Jullien M. , Poinssot C. 
Published: April 2011

ABSTRACTHydrothermal experiments on saturated barrier were conducted for 6 months and 4 years in the granite of the STRIPA mine (Sweden). The French clay Fo-Ca 7 (80 % Kaolinite/Smectite mixed-layer) was compacted (25 MPa) and placed around a steel heater in a 20 cm diameter borehole. The temperature was about 170°C at contact with the heater and only 80°C at clay/granite interface, thus giving a thermal gradient around 10°C/cm
LiNO3 Addition to Cement Which Prevents Aluminum Corrosion
Authors: Matsuo T. , Izumida T. , Hironaga M. , Horikawa Y. , Shiomi T. 
Published: April 2011

ABSTRACTLiNO3 addition to cement was examined to prevent hydrogen gas generation from metallic aluminum in dry active wastes during waste solidification and under circumstances of underground water penetration into the land disposal site. And its reaction mechanism was identified by some chemical analyses. The volume of the hydrogen gas generation with LiNO3 addition was 10% as much as that without LiNO3, by formation of the insoluble Li-Al preservation film on aluminum. After the land disposal of waste forms, LiNO3 would be expected to be effective to prevent aluminum corrosion as long as the cement forms keep their alkaline character, and when it became ineffective, the circumstances around the waste forms can be made less corrosive for aluminum. The aluminum corrosion at that time would be as much as 10% of that without LiNO3 addition.
Preparation of a-Si:H and a-SiGe:H I-Layers for Nip Solar Cells at High Deposition Rates Using a Very High Frequency Technique
Authors: Jones S.J. , Deng X. , Liu T. , Izu M. 
Published: April 2011

ABSTRACTThe 70 MHz Plasma Enhance Chemical Vapor Deposition (PECVD) technique has been tested as a high deposition rate (10 A/s) process for the fabrication of a-Si:H and a-SiGe:H alloy ilayers for high efficiency nip solar cells. As a prelude to multi-junction cell fabrication, the deposition conditions used to make single-junction a-Si:H and a-SiGe:H cells using this Very High Frequency (VHF) method have been varied to optimize the material quality and the cell efficiencies. It was found that the efficiencies and the light stability for a-Si:H single-junction cells can be made to remain relatively constant as the i-layer deposition rate is varied from 1 to 10 Å/s. Also these stable efficiencies are similar to those for cells made at low deposition rates (1 Å/s) using the standard 13.56 MHz PECVD technique. For the a-SiGe:H cells of the same i-layer thickness, use of the VHF technique leads to cells with higher currents and an ability to more easily current match triple-junction cells prepared at high deposition rates which should lead to higher multi-junction efficiencies. Thus, use of this VHF method in the production of large area a- Si:H based multi-junction solar modules will allow for higher i-layer deposition rates, higher manufacturing throughput and reduced module cost.
Effect of Excitation Frequency on the Performance of Amorphous Silicon Alloy Solar Cells
Authors: Yang J. , Sugiyama S. , Guha S. 
Published: April 2011

ABSTRACTWe have studied amorphous silicon alloy solar cells made by using a modified-very-highfrequency glow discharge at 75 MHz with a deposition rate of ∼6 Å/s. The solar cell performance is compared with those made from conventional glow discharge at 13.56 MHz with lower deposition rates. Cells made at ∼6 Å/s with 75 MHz showed comparable stabilized efficiency to those made at ∼3 Å/s with 13.56 MHz. The best performance, however, was obtained with ∼1 Å/s, including a stabilized 9.3% a-Si alloy single-junction cell employing conventional glow discharge technique. Using 75 MHz, we have achieved 11.1% and 10.0% initial active-area efficiencies for a-Si alloy and a-SiGe alloy n i p cells, respectively. An initial efficiency of 11.0% has also been obtained in a dual bandgap double-junction structure.
New Method to Determine the a-Si:H Pin Diode Series Resistance by Noise Measurements
Authors: Blecher F. , Seibel K. , Hillebrand M. , Böhm M. 
Published: April 2011

ABSTRACTThe series resistance limits the linearity of photodiodes and decreases the efficiency of solar cells. It is usually determined from IV-measurements for moderate and high forward current density. This method, however, provides only partial information about Rs, since the series resistance depends on the operating point. An alternative method is based on noise measurements. System noise of the measuring system with a low-noise current-voltage converter has been investigated. A new method for extraction of photodiode series resistance from noise measurements is suggested. Noise measurements are carried out for a-Si:H pin diodes. The series resistance of an amorphous pin diode has been extracted for different operating conditions using the new measurement method.
Photocurrent in Microcrystalline Hydrogenated Silicon P-I-N Devices
Authors: Fernandesi M. , Vieirai M. , Maqarico A. , Koynov S. , Fantoni A. , Schwarz R. 
Published: April 2011

ABSTRACTThe photocurrent delivered by microcrystalline hydrogenated silicon p-i-n devices and the spectral response are analysed under different applied bias voltage. The spectral response is extended far beyond 900 nm. Under reverse bias the spectral response is high and essentially unchanged while under increasing forward bias it decreases continuously. For forward bias higher than the open circuit voltage, the usual reversal of the spectral response is not observed and the photocurrent remains negative and almost independent of the bias voltage. A heterojunction model based on the presence of additional local electric fields near the grain boundaries is presented to explain this behaviour. Those fields lead to a strong increase of the recombination at the grain boundaries decreasing the contribution from the photogenerated carriers for the secondary photocurrent. Reverse bias restores the electric field at the interfaces minimizing the influence of the local barriers.
A Novel Room Temperature Infrared Detector Using Micro-Compensated Amorphous Silicon
Authors: Caputo D. , Cesare G. De , Nascetti A. , Palma F. 
Published: April 2011

ABSTRACTDetection at room temperature of near and medium infrared radiation has been achieved by using micro-doped or micro-compensated amorphous silicon films as intermediate absorber layer in a p-n junction. Extremely low dopant concentrations in the gas mixture have been utilized to achieve micro-doping and micro-compensation. Device operation is based on transitions, induced by the infrared radiation, between extended states in the valence band and defects in the forbidden gap. The absorption process changes electron defect occupancy, giving rise to change in electric field distribution. This effect can be observed as variation of differential capacitance of the structure. Capacitance measurements, performed on two different devices with micro-doped and micro-compensated absorber layer respectively, showed sensitivity to radiation from 900 nm up to 4·5 jim.
Temperature Dependence of Electroluminescence from Nanocrystalline Silicon thin Films
Authors: Toyama T. , Kotani Y. , Shimode A. , Shimizu K. , Okamoto H. 
Published: April 2011

ABSTRACTTemperature dependence of electroluminescence (EL) from nanocrystalline Si (nc-Si) has been studied in comparison with that of photoluminescence (PL) from the nc-Si. The similarity is found in the temperature dependence of peak shift between EL and PL excited by ultraviolet light. The blue shift in both peaks is also found when the carrier generation rate is increased. The experimental results are indicative that the peak shifts due to the temperature and the generation rate are based on different mechanisms.
Erbium-Doped A-Si:H Films Fabricated by Standard Pecvd Using Metalorganics
Authors: Feoktistov N.A. , Golubev V.G. , Medvedev A.V. , Pevtsov A.B. 
Published: April 2011

ABSTRACT1·54 jim light-emitting erbium-doped hydrogenated amorphous silicon films have been fabricated by standard low temperature (200 – 250 °C) PE CVD technique. The films were doped with erbium during the deposition by making use of a new fluorine-containing metalorganic compound Er(HFA)3*DME [where HFA=CF3C(O)CHC(O)CF3, DME=CH3OCH2CH2OCH3]. Photoluminescence spectra of the a-Si(Er):H films were studied within the range 0·6–1·7 pm at both 77 K and 295 K. A photoconductivity was also detected. The photo- to dark conductivity ratio was on the order of 103.
A Study of Silicon Suboxide thin Films by Photoluminescence
Authors: Wang F. , Wolfe D.M. , Hinds B.J. , Lucovsky G. , Platz R. , Wagner S. 
Published: April 2011

ABSTRACTSilicon suboxide (SiOx1 0<x<2) thin films have been investigated by means of photoluminescence, FTIR and photothermal deflection spectroscopy. Results showed that as the oxygen content in the films increases, the temperature dependence of PL intensity (Ipl) becomes weaker, and the PL peak position (Ep) shifts to the visible with decreasing intensity predominantly due to a decrease in the absorption coefficient. After sequential rapid thermal annealing from 500 to 100°C, Ep shifts simply to low photon energy. However, Ip1 of high oxygen content films first increases with increasing annealing temperature (TRTA), then decreases when TRTA>800°C, in contrast to low oxygen content films whose Ip1 monotonically decreases with TRTA and disappears above 700°C. The results are interpreted in terms of inhomogeneity in the as-deposited films, phase segregation upon annealing, and quantum confinement.
Role of the Collecting Resistive Layer on the Static Characteristics of 2D a-Si:H thin Film Position Sensitive Detector
Authors: Fortunato E. , Martins R. 
Published: April 2011

ABSTRACTThe aim of this work is to present an analytical model able to interpret the role of the thin collecting resistive layer on the static performances exhibited by 2D amorphous silicon hydrogenated pin thin film position sensitive detectors. In addition, experimental results concerning the device linearity and spatial resolution are presented and checked against the predicted values of the analytical model proposed.
Deposition and Evaluation of Micro-Crystalline Silicon for Use in Photoconducting Antennas
Authors: Yarasi Sripathi , Manku Tajinder 
Published: April 2011

ABSTRACTThe importance of micro-crystalline silicon (μc-Si:H) for the photo-conducting dipole antenna application is investigated in this paper. The structural and optical properties of gc-Si:H films prepared by plasma enhanced chemical vapor deposition are studied with Raman spectra, scanning electron microscope, and ellipsometer measurements. The influence of grain size and defects on the opto-electronic characteristics of the photo-conducting dipole antenna is discussed. A sample of the antenna fabricated in our clean room laboratory is reported.
Analysis of Radical Reaction on Growing Surface During Si Epitaxy by Photo-Cvd
Authors: Abe Katsuya , Watahiki Tatsuro , Yamada Akira , Konagai Makoto 
Published: April 2011

ABSTRACTThe growth mechanism of Si film at low temperature on Si(100) by photo-CVD was theoretically analyzed by using reaction models both in the gas phase and on the growing surface. We introduced three surface reactions; the growth of Si from SiH3 radicals, the dangling bond termination by atomic hydrogen and the abstraction of bonding hydrogen by SiH3 radicals. We assumed that the film structure is determined by the hydrogen surface coverage ratio “ø” and the parameters of the surface reaction model were determined from the experimental results. The theoretical analysis explained well the experimental data on the growth rate.
Hydrogenated Amorphous Silicon Germanium Alloys Grown by the Hot-Wire Chemical Vapor Deposition Technique
Authors: Nelson Brent P. , Xu Yueqin , Williamson D.L. , Von Roedern Bolko , Mason Alice , Heck Stephan , Mahan A.H. , Schmitt S.E. , Gallagher A.C. , Webb John , Reedy Robert 
Published: April 2011

ABSTRACTWe successfully grow high-quality hydrogenated amorphous-silicon-germanium alloys (a-SiGe:H) by the hot-wire chemical-vapor deposition (HWCVD) technique using silane and germane gas mixtures. These alloys display electronic properties as good as those grown by the plasma-enhanced chemical-vapor deposition (PECVD) technique, when comparing materials with the same optical bandgaps. However, we grow materials with good electrical properties at high deposition rates—up to 40 Å/s, compared to 1–4 Å/s for PECVD materials. Our alloys exhibit similar trends with increasing Ge content to alloys grown by PECVD. The defect density, the dark conductivity, and the degree of nanostructural heterogeneity (as measured by small-angle X-ray scattering) all increase with increasing germanium content in the alloy. The nanostructural heterogeneity displays a sharp transition between 9 at.% and 14 at.% germanium. PECVD- grown a-SiGe:H alloys exhibit a similar transition at 20 at.% Ge. The photoconductivity and the ambipolar diffusion length of the alloys decrease with increasing germanium content. For a fixed silane-to-germane gas ratio, all material properties improve substantially when increasing substrate temperature (Tsub) from 220°C to 375°C. Increasing Tsub also narrows the optical bandgap and lowers the hydrogen content in the alloys for the same germane-to-silane gas ratio.
Internal Stress and Optical Degradation in a-Si:H Deposited on Glass Substrates
Authors: Nakata Jun-ichi , Miyako Tadayuki , Imao Shozo , Doi Atsutoshi 
Published: April 2011

ABSTRACTInternal stress in a-Si:H films prepared by plasma chemical vapor deposition was studied in connection with optical degradation or Staebler-Wronski effect (SWE). It was found that the stress increased with increasing discharge power density (0.03 ∼ 1.5 W/cm2) of silane, accompanied by increase in the introduction rate of SWE. These results imply that highly decomposed radical species due to high discharge power density dominate the surface reaction. Consequently, larger stress and larger introduction rate of SWE are brought about in the films. The stress also slightly increased at lower power density (< 0.03 W/cm2), suggesting that neutral silane molecules take part in the reaction at these power density.
Microcrystalline Silicon Growth: Deposition Rate Limiting Factors
Authors: Hamma S. , Colliquet D. , Cabarrocas P. Rocai 
Published: April 2011

ABSTRACTMicrocrystalline silicon films were deposited on corning glass substrates both by the standard hydrogen dilution and the layer-by-layer (LBL) technique. In-situ UV-visible spectroscopic ellipsometry measurements were performed to analyze the evolution of the composition of the films.The change of the hydrogen plasma conditions by increasing the pressure in the LBL process leads to a faster kinetic of crystallization and to an increase of the deposition rate by a factor of two. The increase of the pressure and the decrease of the inter-electrode distance allowed to increase the deposition rate from 0.26 to 3 Å/s in the hydrogen dilution technique. Interestingly enough, the crystalline fraction of the films remains higher than 50%. However, as the deposition rate increases the growth process results in a slower kinetic of crystallization with a long range evolution of the film composition (up to 0.5 νm).
Photo-Leakage-Current Analysis of Poly-Si TFT by Using Rear Irradiation OBIC Method
Authors: Wakagi Masatoshi , Ookubo Tatsuya , Ando Masahiko , Kawachi Genshiro , Mimura Akio , Minemura Tetsuroh 
Published: April 2011

ABSTRACTPhoto-leakage-current of poly-Si (polycrystalline Si) TFFs has been investigated by using the rear irradiation OBIC (Optical Beam Induced Current) method. In the case of the offset gate TFIs, it was found that the photo-leakage-current was generated in the offset region of the drain electrode side. In order to reduce the photo-leakage-current, low concentration phosphor (P) was doped in the offset region, which corresponds to LDD (Lightly Doped Drain) structure. In the LDD TFT, the photo leakage current at the offset region decreased remarkably, because of the reduction of hole transportation in this region.