bluuebunny/crossref_metadata_2025_split huggingface dataset:
Harvesting Photons in Thin Film Solar Cells with Photonic Crystals
Authors: Zhoue Dayu , Biswas Rana 
Published: April 2011

AbstractEnhanced light absorption and improved photon harvesting is a major avenue to improving solar cell performance. We simulate and design photonic crystal based loss-less back reflectors. The photonic crystal is a 2-dimensional photonic crystal combined with a distributed Bragg reflector. We have designed and simulated a thin film a-Si:H solar cell with the photonic crystal reflector and an antireflection coating. The photonic crystal has square lattice symmetry and generates strong diffraction of near band edge photons in the absorber layer. The absorption of red and near-IR photons is increased by more than an order of magnitude by the photonic crystal. The photonic crystals are composed of ITO and can easily serve as a conducting back contact. This scheme can be easily extended to other solar absorber layers. We have optimized the geometry of the photonic crystal to maximize absorption using rigorous scattering matrix simulations. The optical path length with the photonic crystal can improve over the limit for a random roughened scattering surface.
Influence of Radiation Damage and Isochronal Annealing on the Magnetic Susceptibility of Pu1-xAmx Alloys
Authors: McCall Scott K , Fluss Michael J , Chung Brandon W. , Haire Richard G. 
Published: April 2011

AbstractResults of radiation damage in Pu and Pu1-xAmx alloys studied with magnetic susceptibility, χ(T), and resistivity are presented. Damage accumulated at low temperatures increases χ(T) for all measured alloys, with the trend generally enhanced as the lattice expands. There is a trend towards saturation observable in the damage induced magnetic susceptibility data. that is not evident in similar damage induced resistivity data taken on the same specimen. A comparison of isochronal annealing curves measured by both resistivity and magnetic susceptibility on a 4.3at% Ga stabilized δ-Pu specimen show that Stage I annealing, where interstitials begin to move, is largely transparent to the magnetic measurement. This indicates that interstitials have little impact on the damage induced increase in the magnetic susceptibility. The isochronal annealing curves of the Pu1-xAmx alloys do not show distinct annealing stages as expected for alloys. However, samples near 20% Am concentration show an unexpected increase in magnetization beginning when specimens are annealed to 35K. This behavior is also reflected in a time dependent increase in the magnetic susceptibility of damaged specimens indicative of first order kinetics. These results suggest there may be a metastable phase induced by radiation damage and annealing in Pu1-xAmx alloys.
First-principles Study of the Electronic Structure and Local Moment Interactions in PuAm Alloy
Authors: Han Myung Joon , Wan Xiangang , Savrasov Sergej Y 
Published: April 2011

AbstractExpected to provide a clue about the origin of zero moment in the bulk phase of Plutonium, Pu1-xAmx alloys have attracted a great attention, in which upon doping the system transforms from the Kondo lattice to the diluted impurity limit. To understand the electronic structure and the magnetic properties of Pu in different crystal environments, we performed fully self-consistent first-principles calculations of the PuAm system based on the local density approximation (LDA) combined with static (LDA+U) and dynamic corrections (LDA+DMFT) for on-site electron correlations. The electronic structure strongly depends on the level of approximation for correlation effects. The exchange interactions between Pu 5f electrons and the Kondo screening strength were estimated and compared, which provide a new insight to Pu magnetism.
Zirconia Inert Matrix Fuel for Plutonium and Minor Actinides Management in Reactors and as an Ultimate Waste Form
Authors: Degueldre Claude , Wiesenack Wolfgang 
Published: April 2011

AbstractA plutonia stabilised zirconia doped with yttria and erbia has been selected as inert matrix fuel (IMF) at PSI. The results of experimental irradiation tests on yttria-stabilised zirconia doped with plutonia and erbia pellets in the Halden research reactor as well as a study of zirconia solubility are presented. Zirconia must be stabilised by yttria to form a solid solution such as MAz(Y,Er)yPuxZr1-yO2-ζ where minor actinides (MA) oxides are also soluble. (Er,Y,Pu,Zr)O2-ζ (with Pu containing 5% Am) was successfully prepared at PSI and irradiated in the Halden reactor. Emphasis is given on the zirconia-IMF properties under in-pile irradiation, on the fuel material centre temperatures and on the fission gas release. The retention of fission products in zirconia may be stronger at similar temperature, compared to UO2. The outstanding behaviour of plutonia-zirconia inert matrix fuel is compared to the classical (U,Pu)O2 fuels. The properties of the spent fuel pellets are presented focusing on the once through strategy. For this strategy, low solubility of the inert matrix is required for geological disposal. This parameter was studied in detail for a range of solutions corresponding to groundwater under near field conditions. Under these conditions the IMF solubility is about 109 times smaller than glass, several orders of magnitude lower than UO2 in oxidising conditions (Yucca Mountain) and comparable in reducing conditions, which makes the zirconia material very attractive for deep geological disposal. The behaviour of plutonia-zirconia inert matrix fuel is discussed within a burn and bury strategy.
Pu-Bearing Materials - From Fundamental Science To Storage Standards
Authors: Tam Shiu-Wing , Liu Yung 
Published: April 2011

AbstractThe behavior of plutonium (Pu) oxides in the presence of water/moisture in a confined space and the associated issues of hydrogen and oxygen generation due to radiolysis have important implications for the storage and transportation of Pu-bearing materials. This paper reviews the results of recent studies of gas generation in the Pu-O-H system, including the determination of release rates via engineering-scale measurement. The observations of the significant differences in gas generation behavior between “pure” Pu-bearing materials and those that contain salt impurities are addressed. In conjunction with the discussion of these empirical observations, the work also addresses recent scientific advances in the investigations of the Pu-O-H system using state-of-the-art ab initio electronic structure calculations, as well as advanced synchrotron techniques to determine the electronic structure of the various Pu-containing phases. The role of oxidizing species such as the hydroxyl radical from the radiolysis of water is examined. Discussed also is the challenge in the predictive ab-initio calculations of the electronic structure of the Pu-H-O system, due to the nature of the 5f valence electrons in Pu. Coupled with the continuing material surveillance program, it is anticipated that this work may help determine the electronic structure of the various Pu-containing phases and the role of impurity salts on gas generation and the long-term stability of oxygen/hydrogen-containing plutonium oxides beyond PuO2.
Dialogue-Based Public Engagement with Nanotechnology
Authors: Aggelopoulou Argiri , Kramer Victoria , Reynolds J. Ryan , Townsend Colin , Toumey Chris 
Published: April 2011

AbstractTheory and experience emphasize that science communications between experts and nonexperts should be dialogue, not monologue. This principle guides a program of public engagement with nanotechnology at the University of South Carolina. It enables the participants to express their values and concerns to experts, and to question them. It is intended that the knowledge and confidence generated by this program will enhance the participants' ability to have active and constructive roles in nanotech policy.
Education and Outreach Program on Materials at the University of Puerto Rico - Mayaguez
Authors: Suárez Oscar Marcelo , Dika Sandra , Santos Jeannette , Marrero Eddie 
Published: April 2011

AbstractThe University of Puerto Rico-Mayaguez and University of Wisconsin-Madison Partnership for Research and Education in Materials (UPRM-UW PREM) aims to create richer educational and research opportunities for Hispanic students in Materials Science and Engineering (MSE) and increase their representation in the Materials Science community. The educational and outreach (E&O) components for the UPRM-UW PREM include interventions for high school students and teachers, and undergraduate and graduate students at UPRM. The present report focuses on activities conducted with high school and university students during the third year of the program (2006-07). Results of surveys with student participants indicate that their participation contributes positively to their learning and development in laboratory, research and professional skills, as well as increases student interest in pursuing graduate studies in MSE.
Green Nanotechnologies for Responsible Manufacturing
Authors: Vaseashta Ashok , Reisfeld Renata , Mihailescu Ion N. 
Published: April 2011

AbstractA perpetual increase in population and thus consumption of fossil fuels has led to increased pollution worldwide. Pollution in large metropolitan cities has reached an alarming level and is widely believed to be the leading contributor to chronic and deadly health disorders and diseases affecting millions of people each year. Although correlation between environmental pollution and global warming is debatable, the effects of pollution and its impact on human health are irrefutable and highly observable. Use of nanomaterials to generate energy, in an attempt to reduce environmental pollution, is in its preliminary stages and requires urgent and detailed investigation. This investigation focuses on three aspects of sustainability, (a): use of nanomaterials to monitor, detect, and remediate the environmental pollution, (b): responsible manufacturing of nanomaterials by employing principles of “green chemistry”, and (c): to drastically reduce waste and emission by-products employing use of nanomaterials as catalysts for enhanced efficiency. The synthesis of nanomaterials is accomplished by processes employing processes such as electrospinning, sol-gel, and MAPLE to drastically reduce and isolate emission and waste by-products. An exhaustive overview of the scope of our investigation and some specific applications relating to the use of nanomaterials in environmental friendly investigations, viz.; applications of nanomaterials as catalysts for enhanced efficiency, materials in CO2 sequestration, remediation of toxic metals in water streams, efficient thin film photovoltaic devices, fuel cells, and biodegradable consumable products is described. Fate and transport of nanomaterials in air, water, and soil; life-cycle analysis, and methodologies to conduct risk-assessment in the context of source reduction and conservation is discussed as a step towards sustainability.
Durability of a Cementitious Wasteform for Intermediate Level Waste
Authors: McGlinn Peter J. , Brew Daniel R.M. , Aldridge Laurence P. , Payne Timothy E. , Olufson Kylie P. , Prince Kathryn E. , Kelly Ian J. 
Published: April 2011

AbstractCementitious material is the most commonly used encapsulation medium for low and intermediate level radioactive waste. This paper focuses on the aqueous durability of a Materials Testing Reactor (MTR) cementitious wasteform – a possible candidate for the proposed intermediate level waste management facility in Australia. A series of medium term (up to 92 months) durability tests, without leachate replacement, were conducted on samples of this wasteform.The wasteform was made from cement, ground granulated blast furnace slag and a simulated waste liquor. The compressive strength (39 MPa) was typical of MTR cement wasteforms and well above that required for handling or storage. The wasteform was an inhomogeneous mixture containing calcite, a calcium silicate hydrate phase, hydrotalcite and unreacted slag particles. After leaching for 92 months the crystallinity of the calcium silicate hydrate phase increased.The majority of the releases of Ca, Si, Al, Sr, S, Na and K was reached within 4 days of leaching, with the maxima ie. the highest concentrations in the leachates, occurring at 3 months for Ca, Al, Sr, S, Na and K, and at 1 month for Si. For the longer leach periods (6 months and 3 months respectively) there was a slight reduction in concentration in the leachates, and these levels were similar to those for the longest period of 92 months, suggesting steady-state conditions prevailing after 3 to 6 months of leaching. The highest releases of matrix elements were for Na (37%), K (40%) and S (16%). Releases for elements such as Ca, Na, Al and Sr were similar in magnitude to those reported by the UKAEA in earlier MTR studies.After leaching for 92 months there was an alteration layer about 80 ∞m deep where calcium has been depleted. Na, K and Sr showed signs of diffusion towards the outer part of the cement samples.
NMR Investigation of Cation Distribution in HLW Wasteform Glass
Authors: Holland Diane , Parkinson Ben G , Islam Moinul M , Duddridge Adam , Roderick Jonathan M , Howes Andy P , Scales Charlie R 
Published: April 2011

AbstractMagic-angle-spinning NMR has been used to establish the structural roles of various cations added to the borosilicate glass which is used for the vitrification of high-level nuclear waste (HLW). Representative surrogate oxides with nominal valencies of +1, +2 and +3 have been studied which span the range of oxides from modifier to intermediate and conditional glassformer. NMR has been carried out on those nuclei which are accessible and the species observed have been correlated with the physical and chemical behaviour. The controlling factor is the manner in which the alkali cations partition between the various network groups, changing the distribution of silicon Qn species and the boron N4 ratio. Identifiable superstructural units are also present in these glasses. The aqueous corrosion rate increases with Q3 content, as does the weight loss due to evaporation from the melt. The activation energy for DC conduction scales with N4. Values of N4 obtained for these glasses deviate significantly from those predicted by the currently accepted model (Dell and Bray) and are strongly affected by the modifier or intermediate nature of the surrogate oxide and also by its effect on the distribution of nonbridging oxygens between the silicate and borate polyhedra.
Overview of the CEA French Research Program on Nuclear Waste
Authors: Vernaz Etienne Y. , Poinssot Christophe 
Published: April 2011

AbstractThis presentation gives an overview of the French major research program on nuclear waste and presents some perspectives in the context of the 2006 Act, while focusing on the main CEA contributions. Development of new conditioning processes combined with in-depth studies of the waste-packages long term behaviour studies allows enhancing the expected performance of waste-packages. Geological disposal performances have been demonstrated based in particular on the relevant understanding of the radionuclides chemistry and migration in complex environment, including tracing field-experiments in ANDRA underground research lab. French research and plans for waste from future reactors will be discussed. It is still a very prospective area as fuel materials that will be used in these reactors is not decided. The capacity to recycle most of the fuel component will be a major point in the choice of an integrated concept including reactor and fuel cycle.
Cold Crucible Vitrification of Uranium-Bearing High Level Waste Surrogate
Authors: Stefanovsky S.V. , Ptashkin A.G. , Knyazev O.A. , Zen'kovskaya M.A. , Marra J.C. 
Published: April 2011

AbstractThree tests on vitrification of U-bearing DWPF SB2 and SB4 waste surrogates (40-50 wt% waste loading) in a lab-scale (56 mm inner diameter) copper cold crucible with melt surface area of 24.6 cm2 energized from a 5.28 MHz/10 kW generator were conducted. At the feeding of the air-dry batch (3-5 wt% moisture) glass productivity and specific melt productivity achieved under steady-state conditions were 0.64 kg/h and 256 kg/(m2×h) [6150 kg/(m2×day)], respectively. Similar to previously prepared U-free products, the U-bearing vitrified SB2 (highferrous) waste product was composed of U-enriched glassy matrix and high-ferrous spinel structure phase. As expected, the vitreous phase in the vitrified SB2 waste surrogate was enriched with Na, Al, Si, P, S, Ca, Sr, Pb, U oxides and Cl, whereas spinel preferentially accumulated transition metals (iron group elements: Mn, Fe, Ni) as well as Cu and Zn oxides. Iron oxide content in the spinel phase was ∼67–71 wt %. This result was consistent with XRD data and implies that this spinel was close to magnetite with respect to chemical composition and structure. This was consistent with our previous data on characterization of glass crystalline materials containing both U-bearing and U-free SB2 waste surrogate produced in resistive furnace and cold crucibles. The vitrified SB4 (high-alumina) waste products were predominantly amorphous at waste loading of up to 50 wt %. Traces of quartz occurred in the “skull” zone. In all the products, uranium was found to be uniformly distributed within the vitreous phase. Leach rates of Na, Si, Fe, and U from the vitrified SB2 waste surrogate (50 wt % waste loading) determined by a SPFT procedure were found to be 1.38, 1.42, 0.122, and 0.841 (g×m−2×d−1), respectively.
Immobilization of Radioactive Iodine Using AgI Vitrification Technique for the TRU Wastes Disposal: Evaluation of Leaching and Surface Properties
Authors: Sakuragi Tomofumi , Nishimura Tsutomu , Nasu Yuji , Asano Hidekazu , Hoshino Kuniyoshi , Iino Kenji 
Published: April 2011

AbstractIodine-129 collected from a reprocessing plant is regarded as the dominant nuclide in terms of safety for TRU wastes disposal in Japan. AgI vitrification (AgI-Ag2O-P2O5) is a potential iodine immobilization technique, which has the advantages of less iodine volatilization (low-temperature vitrification) and high volume reduction efficiency (approx. 1/25 the original waste volume). The iodine immobilization property can be evaluated by examining the surface condition of the AgI glass immersed in water. In this study, immersion tests have been performed on AgI glass in pure water in a 3% H2-N2 atmosphere at room temperature, and the surface characteristics have been examined. The thin layer (<4.3 μm) that is formed has been found to consist of AgI, which may act as a barrier, preventing leaching of glass components. The concepts behind the iodine release model have been proposed based on diffusion and the solubility of the components at the glass surfaces.
Synthesis and Characterisation of Ln2TiO5 Compounds
Authors: Aughterson Robert D. , Lumpkin Gregory R. , Smith Katherine L. , Thorogood Gordon J. , Whittle Karl R. 
Published: April 2011

AbstractBulk samples of six Ln2TiO5 compounds with Ln = La, Pr, Nd, Eu, Gd and Tb were prepared and characterised. Most of the samples have a phase purity of ∼95% (based on BEI and EDS) with the predominant secondary phase primarily being Ln2Ti2O7. Using XRD, TEM selected area diffraction and high resolution imaging techniques, we have confirmed the results of previous studies which showed that at room temperature Pr2TiO5, Nd2TiO5, Eu2TiO5 and Tb2TiO5 have orthorhombic structures with Pnma symmetry. The structure of Tb2TiO5 was further monitored as a function of temperature. The relevance of Ln2TiO5 compounds to advanced nuclear fuel cycles is discussed.
Characterisation of 20 Year Old Pu238 -Doped Synroc C
Authors: Hambley M.J. , Dumbill S. , Maddrell E.R. , Scales C.R. 
Published: April 2011

AbstractIn 1987 samples of Pu238 and Cm244 doped Synroc C were prepared in the UKAEA Laboratories at Harwell. They were studied for five years before being archived. During decommissioning of the Harwell laboratories the samples were transferred to Sellafield and the opportunity was taken to conduct further studies. Given the age of the samples, they offer a unique insight into the long term radiation stability of Synroc. To date, the three Pu238 samples have been examined. The alpha decay dose experienced by the samples is estimated to be 3 × 1019 alphas per gram.The sample allowed to accumulate alpha decay damage (10587) was slightly heterogeneous, with an apparent grain size in the range 3–15νm. EDX analysis confirmed the phases present to be those expected in Synroc C and that the Pu had partitioned predominantly into the perovskite and zirconolite. Microcracking was observed in the hollandite and rutile but cracks arrested once they reached a zirconolite or perovskite grain.Sample 10588 was annealed after five years, at temperatures up to 1200°C, this sample was microstructurally similar to 10587 at the 20-50νm scale but differs at small scales. A major difference is the presence of both intergranular and intragranular porosity.Sample 10589 was annealed at the same time as 10588 but differed significantly probably due to actual fabrication temperatures being higher than those recorded.Information on these samples will be presented, along with a discussion of the implications for the expected long term stability of titanate ceramic wasteforms.
RN Fractional Release of High Burn-Up Fuel: Effect of HBS and Estimation of Accessible Grain Boundary
Authors: Clarens F. , Serrano-Purroy D. , Martínez-Esparza A. , Wegen D. , Gonzalez-Robles E. , Pablo J. de , Casas I , Giménez J. , Christiansen B. , Glatz J.P. 
Published: April 2011

AbstractThe so-called Instant Release Fraction (IRF) is considered to govern the dose released from Spent Fuel repositories. Often, IRF calculations are based on estimations of fractions of inventory release based in fission gas release [1]. The IRF definition includes the inventory located within the Gap although a conservative approach also includes both the Grain Boundary (GB) and the pores of restructured HBS inventories.A correction factor to estimate the fraction of Grain Boundary accessible for leaching has been determined and applied to spent fuel static leaching experiments carried out in the ITU Hot Cell facilities [2]. Experimental work focuses especially on the different properties of both the external rim area (containing the High Burn-up Structure (HBS)) and the internal area, to which we will refer as Out and Core sample, respectively. Maximal release will correspond to an extrapolation to simulate that all grain boundaries or pores are open and in contact with solution.The correction factor has been determined from SEM studies taking into account the number of particles with HBS in Out sample, the porosity of HBS particles, and the amount of transgranular fractures during sample preparation.