bluuebunny/crossref_metadata_2025 huggingface dataset:
Recoil Based Fuel Breeding Fuel Structure
Authors: Popa-Simil Liviu
Published: April 2011

Nuclear transmutation reactions are based on the absorption of a smaller particle as neutron, proton, deuteron, alpha, etc. The resulting compound nucleus gets out of its initial lattice mainly by taking the recoil, also with help from its sudden change in chemical properties. The recoil implantation is used in correlation with thin and ultra thin materials mainly for producing radiopharmaceuticals and ultra-thin layer radioactive tracers. In nuclear reactors, the use of nano-particulate pellets could facilitate the recoil implantation for breeding, transmutation and partitioning purposes. Using enriched 238U or 232Th leads to 239Pu and 233U production while using other actinides as 240Pu, 241Am etc. leads to actinide burning. When such a lattice is immersed into a radiation resistant fluid (water, methanol, etc.), the recoiled product is transferred into the flowing fluid and removed from the hot area using a concentrator/purifier, preventing the occurrence of secondary transmutation reactions. The simulation of nuclear collision and energy transfer shows that the impacted nucleus recoils in the interstitial space creating a defect or lives small lattices. The defect diffuses, and if no recombination occurs it stops at the lattices boundaries. The nano-grains are coated in thin layer to get a hydrophilic shell to be washed by the collection liquid the particle is immersed in. The efficiency of collection depends on particle magnitude and nuclear reaction channel parameters. For 239Pu the direct recoil extraction rate is about 70% for 238UO2 grains of 5 nm diameters and is brought up to 95% by diffusion due to 239Neptunium incompatibility with Uranium dioxide lattice. Particles of 5 nm are hard to produce so a structure using particles of 100 nm have been tested. The particles were obtained by plasma sputtering in oxygen atmosphere. A novel effect as nanocluster radiation damage robustness and cluster amplified defects rejection will be discussed. The advantage of the method and device is its ability of producing small amount of isotopic materials easy to separate, using the nuclear reactors, with higher yield than the accelerator based methods and requiring less chemistry. It also represents a reliable candidate for nuclear fuel breeding reducing the cost of super-grade Plutonium and Thorium toward the price of urania and thoria.
Plutonium Elastic Moduli, Electron Localization, and Temperature
Authors: Migliori Albert , Mihut-Stroe Izabella , Betts Jon B.
Published: April 2011

In almost all materials, compression is accompanied naturally by stiffening. Even in materials with zero or negative thermal expansion, where warming is accompanied by volume contraction it is the volume change that primarily controls elastic stiffness. Not so in the metal plutonium. In plutonium, alloying with gallium can change the sign of thermal expansion, but for the positive-thermal-expansion monoclinic phase as well as the face-centered-cubic phase with either sign of thermal expansion, and the orthorhombic phase, recent measurements of elastic moduli show soften on warming by an order of magnitude more than expected, the shear and compressional moduli track, and volume seems irrelevant. These effects point toward a novel mechanism for electron localization, and have important implication for the pressure dependence of the bulk compressibility.
The Nanoscale Informal Science Education Network
Authors: Bell Larry
Published: April 2011

The Nanoscale Informal Science Education Network was formed by the Museum of Science in partnership with the Science Museum of Minnesota and the Exploratorium through a cooperative agreement with the National Science Foundation in the fall of 2005. Over the course of its first two years the NISE Net focused on developing prototype informal educational materials to engage the public in learning about nanoscale science and technology. Now the NISE Net if focusing on building the network and disseminating materials and knowledge broadly to facilitate capacity building, partnering, and getting nano education activities for the public to happen in over 100 sites nationwide. NanoDays in 2008 from March 29 through April 6 has been developed to focus these efforts.
European Nanotechnology Masters Recognition Scheme - Supporting Technical Higher Education
Authors: Singh Kshitij Aditeya
Published: April 2011

Europe aspires to become a knowledge oriented economy by 2010 in which nanoscience and nanotechnologies play an important role. However, the development of skills and competencies in the workforce will be critical in realising the benefits offered by nanoscience and nanotechnologies. The Nanotechnology Masters Recognition Scheme aims to support technical higher education by addressing the challenges of education in nanoscience and nanotechnologies particularly at the masters' level. The paper provides an overview of the education and professional development systems in Europe with specific examples from the U.K. The paper also underlines how the scheme addresses the challenges of skills and competencies development within the European context through information dissemination, identifying gaps and professional needs, encouraging professional development, and supporting through various different measures.
Towards Terabit/in2 Magnetic Storage Media
Authors: Niarchos Dimitris , Manios E. , Panagiotopoulos I.
Published: April 2011

In modern society there is an almost insatiable demand for ever increasing storage capacities in computers and consumer electronics. Magnetic recording is the dominant storage technology and the hard disk, due to its versatility, is becoming a pervasive device in various applications. The soaring demand arises from data-intensive computer applications, including graphics, animation, multimedia and desktop publishing, to which can be added a growing market for non-PC consumer devices such as set-top boxes, cameras, mobile phones, laser printers and satellite navigation systems. In response to this demand the hard disk drive manufacturers have come forward with spectacular increase in storage capacities and densities over the last decade. It is currently projected that the evolution of conventional perpendicular recording storage density in the hard disk industry will reach a limit of 500 Gbit/in2, while further progress will require major breakthroughs and alternative technologies.
In this presentation we will review the state-of-the-art in magnetic recording media and we will discuss the future approaches to reach densities in excess of 1 Tbit/in2 densities along the three axes : a) self-assembled coercive nanoparticles, b) exchange spring media and percolated media, and c) bit-patterned media (nanoscale patterning). This entails resolving several conflicting requirements with regard to signal to noise ratio (SNR) , writability and thermal stability of these new promising systems.
Investigation on the Immobilisation of Carbon in OPC-BFS and OPC-PFA Systems
Authors: Kinoshita Hajime , Borges Paulo H. R. , Utton Claire A. , Milestone Neil B. , Lynsdale Cyril
Published: April 2011

The reaction of CO2 gas with OPC, OPC-BFS and OPC-PFA composite cement systems were studied using XRD, SEM and TG to investigate the applicability of these materials to immobilise carbon arising from graphite waste. XRD results suggested that calcite formed in OPC system after the carbonation reaction, whereas calcite and vaterite were observed in OPCBFS and OPC-PFA systems. In OPC system, nearly half of Ca(OH)2 was consumed to form CaCO3. In OPC-BFS and OPC-PFA systems, the amount of CaCO3 formed, corresponded to the consumption of greater than 100% of Ca(OH)2 initially present, suggesting that other hydration products e.g. C-S-H were also consumed, either directly or indirectly during the carbonation process. The OPC-BFS system became more porous after carbonation. OPC-PFA system indicated a high efficiency on the conversion of Ca in the system into CaCO3.
Changes to Alkali Ion Content Adjacent to Crystal-Glass Interfaces
Authors: Rushton Michael J. D. , Grimes Robin W. , Owens Scott L.
Published: April 2011

Atomic scale molecular dynamics simulations have been used to predict the location of glass modifying Na, Li and Mg species in a borosilicate Magnox type waste glass adjacent to interfaces with the (100) and (110) surfaces of MgO, CaO and SrO crystals. These simulations show a considerable increase in alkali and alkali earth concentration adjacent to specific interfaces. In particular, there are significant, systematic changes in Na, Li and Mg position and concentration as a function of both the crystal's terminating surface and composition.
A Mössbauer Study of Iron in Vitrified Wastes
Authors: Hannant Oliver M. , Bingham Paul A. , Hand Russell J. , Forder Sue D.
Published: April 2011

57Fe Mössbauer spectroscopy has been used to study the environment and oxidation state of iron in a series of vitrified sewage sludge ash (SSA) wastes, which are broadly similar in composition and variability to some intermediate-level legacy wastes (ILLW). The SSA wastes studied here are incapable of forming an homogeneous glass when melted at 1450 °C although increasing additions of CaO reduce the crystalline content, which consists of Ca3(PO4)2 and Ca3Mg3(PO4)4. Bulk glass transition temperatures of 670–850 °C have been measured, the value decreasing with increasing CaO content. Tetrahedrally coordinated Fe3+ appears to exist in vitrified SSA only at high CaO contents (> ∼ 29 mol. %) and whilst broadly similar to our previous results for simulated vitrified SSA, behavioural differences have been noted between fitted Mossbauer parameters for real and simulated vitrified SSA. We suggest that these could be attributable to the buffering action of carbon and other reducing agents in the real SSA wastes.
HIPed Tailored Ceramic Waste Forms for the Immobilisation of Cs and Sr
Authors: Carter Melody L. , Vance E. R.
Published: April 2011

This paper illustrates the benefits of hot isostatically pressed (HIPed) tailored ceramic waste forms for the immobilisation of Cs and Sr separated from spent nuclear fuel. Experimental data on microstructure and aqueous durability are presented for Cs- and Sr-bearing hollanditerich tailored ceramics prepared with 12-18 wt% waste (on an oxide basis). MCC-1 type leach testing, on the sample containing 12 wt% waste at 90°C for 28 days revealed extremely low normalised 7-28-day Cs and Sr release rates of 0.003 and 0.004 g/m2day respectively.
Neutron and Resonant X-ray Diffraction Studies of Zirconolite-2M
Authors: Whittle Karl R. , Smith Katherine L. , Hyatt Neil C. , Lumpkin Gregory R.
Published: April 2011

Zirconolite (nominally CaZrTi2O7) is a constituent phase of potential waste forms for the safe immobilisation of actinide wastes. Structural studies of such materials provide important information about cation ordering, lattice parameters, and strain effects, and provide input into the modelling of alpha decay damage and the development of future wasteform designs. A suite of zirconolites based on the replacement of Ti with Nb and Fe has been studied using high resolution neutron diffraction and resonant X-ray diffraction to determine the degree of disorder across the available cation sites. Resonant X-ray diffraction is a unique method which allows the location of certain cations to be determined accurately by taking advantage of the change in scattering power close to an absorption edge (e.g., Nb-K and Zr-K). Using standard X-ray diffraction alone this is not possible and there is little scattering difference between Nb and Zr.

Raman spectroscopy and measured lattice parameters have shown that the exchange of Ti with Nb and Fe has a non-linear effect on the unit cell dimensions and Raman peak positions while retaining the 2M polytype. Mössbauer spectroscopy has shown that the Fe preferentially fills the Ti split (C2) site. The results from this study provide a more complete picture of the cation order-disorder problem and are generally consistent with the behaviour of lattice parameters across the series.
Migration Behaviour of Ferrous Ion in Compacted Bentonite Under Reducing Conditions Controlled With Potentiostat
Authors: Idemitsu Kazuya , Nessa Syeda Afsarun , Yamazaki Shigeru , Ikeuchi Hirotomo , Inagaki Yaohiro , Arima Tatsumi
Published: April 2011

Carbon steel overpack is corroded by consuming oxygen introduced by repository construction after closure of the repository and then maintains the reducing environment in the vicinity of the repository. The migration of iron corrosion products through the buffer material will affect the migration of redox-sensitive radionuclides. Therefore, it is important to study the migration of iron corrosion products through the buffer material because it may affect the corrosion rate of overpack, and migration of redox-sensitive radionuclides. Electromigration experiments have been conducted with the source of iron ions supplied by anode corrosion of the iron coupon in compacted bentonite. The carbon steel coupon was connected as the working electrode to the potentiostat and was held at a constant supplied potential between - 650 to +300 mV vs. Ag/AgCl electrode for up to 168 hours. The amount of iron penetrated into a bentonite specimen was in good agreement with the calculated value from the corrosion current under the assumption that iron is dissolved as ferrous ions. A model using dispersion and electromigration could explain the measured iron profiles in the bentonite specimens. The fitted value of electromigration velocity depended on the potential supplied. On the other hand the fitted value of the dispersion coefficient did not depend on the potential supplied but a constant. This constant dispersion coefficient could be due to the much larger diffusion coefficient of ferrous ion in bentonite compared with the effect of mechanical dispersion. The experimental configurations used in this study are applicable to the examination of the migration behaviour of cations with the source of iron ions under a reducing condition controlled with a potentiostat.
Deep Borehole Disposal of Plutonium
Authors: Gibb Fergus G.F. , Taylor Kathleen J. , Burakov Boris E.
Published: April 2011

Excess plutonium not destined for burning as MOX or in Generation IV reactors is both a long-term waste management problem and a security threat. Immobilisation in mineral and ceramic-based waste forms for interim safe storage and eventual disposal is a widely proposed first step. The safest and most secure form of geological disposal for Pu yet suggested is in very deep boreholes and we propose here that the key to successful combination of these immobilisation and disposal concepts is the encapsulation of the waste form in small cylinders of recrystallized granite. The underlying science is discussed and the results of high pressure and temperature experiments on zircon, depleted UO2 and Ce-doped cubic zirconia enclosed in granitic melts are presented. The outcomes of these experiments demonstrate the viability of the proposed solution and that Pu could be successfully isolated from its environment for many millions of years.
Molecular Characterisation of Dissolved Organic Matter (DOM) in Groundwaters from the Äspö Underground Research Laboratory, Sweden: A Novel “Finger Printing Tool for Palaeohydrological Assessment
Authors: Vane Christopher H. , Kim Alexander W. , Milodowski Antoni E. , Smellie John , Tullborg Eva-Lena , West Julia M.
Published: April 2011

The molecular signature of dissolved organic matter (DOM) in groundwaters can be used as a tool when investigating the palaeohydrological response of groundwater systems in relation to changes in recharge environment, and also for examining groundwater compartmentalisation, mixing and transport at underground repositories for radioactive waste. The DOM in groundwaters from two compartmentalised bodies of groundwater of distinctly different origin within the Äspö Underground Research Laboratory (URL), Sweden and in Baltic seawater has been isolated using tangential flow ultrafiltration (TUF) and diafiltration. Recoveries of DOM ranged from 34.7 to 0.1 mg/L with substantial differences in the concentrations of the groundwaters collected only 120 m apart. Analysis by infrared spectroscopy (IR) and pyrolysisgas chromatography-mass spectrometry (Py-GC-MS) of the isolated DOM revealed that the groundwaters contained abundant alkylphenols which may represent heavily decomposed proteins or lignins originating from biopolymers contained within soils. The difference in the distribution and relative abundance of major pyrolysis products groups such as alkyphenols confirmed that the groundwater and Baltic seawater DOM samples were chemically distinct indicating minimal infiltration of marine groundwater derived by recharge from the Baltic or earlier Littorina Sea within the two compartmentalised groundwater bodies.
The Use of Activated Slags as Immobilisation Matrices for ILW
Authors: Milestone NB , Bai Y , Yang C.H. , Shi Y.J. , Li X.C.
Published: April 2011

Composite cements where large amounts of blast furnace slag (BFS) replace Portland cement are currently used for immobilisation of ILW. Hydration of BFS is activated by the small amount of OPC present but the amount of reaction that occurs is limited at ambient temperatures. Increasing the temperature increases the hydration of the BFS but large amounts still remain unreacted, leaving a porous matrix where the capillary pores remain filled with a highly alkaline solution. This solution causes corrosion of reactive metals giving rise to expansive reactions and hydrogen release, and it can destroy the structure of zeolites releasing the adsorbed species.

Apart from OPC, BFS hydration can be activated by other compounds such as hydroxides, sulphates, silicates, and calcium aluminate cements. The use of these alternatives gives rise to binders such as ettringite and strätlingite which have a different chemistry where the pore solution has a lower pH. Corrosion of metals does not readily occur in these binders. This may be due to the reduced pH but could also arise from the lack of pore water, as these binders bind more water in their structure so that it is not available for transport of ionic species. This extra water binding also has potential for immobilisation of sludges where high w/s ratios are necessitated by the need to transport the sludge.

This paper will review some of the alternative activators for slag hydration and present experimental results on several systems where slag has been activated with compounds other than OPC.
Realization of Significant Absorption Enhancement in Thin Film Silicon Solar Cells with Textured Photonic Crystal Backside Reflector
Authors: Zeng Lirong , Bermel Peter , Yi Yasha , Alamariu Bernard A. , Broderick Kurt A. , Liu Jifeng , Hong Ching-yin , Duan Xiaoman , Joannopoulos John , Kimerling Lionel C.
Published: April 2011

The major factor limiting the efficiencies of thin film Si solar cells is their weak absorption of red and near-infrared photons due to short optical path length and indirect bandgap. Powerful light trapping is essential to confine light inside the cell for sufficient absorption. Here we report the first experimental application of a new light trapping scheme, the textured photonic crystal (TPC) backside reflector, to monocrystalline thin film Si solar cells. TPC combines a onedimensional photonic crystal, i.e., a distributed Bragg reflector (DBR), with a reflection grating. The near unity reflectivity of DBR in a wide omnidirectional bandgap and the large angle diffraction by the grating ensures a strong enhancement in the absorption of red and near-infrared photons, leading to significant improvements in cell efficiencies. Measured short circuit current density Jsc was increased by 19% for 5 μm thick cells, and 11% for 20 μm thick cells, compared to theoretical predictions of 28% and 14%, respectively.
Infrared ellipsometric characterization of silicon nitride films on textured Si photovoltaic cells
Authors: Saenger M. F. , Schädel M. , Hofmann T. , Hilfiker J. , Sun J. , Tiwald T. , Schubert M. , Woollam J. A.
Published: April 2011

We present an infrared spectroscopic ellipsometry investigation of SixNyfilms deposited on textured Si substrates employed for photovoltaic cells. A multiple-sample data analysis scheme is used in order to determine the SixNydielectric function and thickness parameters regardless of the surface morphology of the substrate. We observe changes in the dielectric function of the silicon nitride film which suggest variations in the chemical composition of the films depending on the substrate morphology.
A Novel Solution Processable Electron Acceptor, C60(CN)2, for Bulk Heterojunction Photovoltaic Applications
Authors: Koppolu Vaishali R. , Gupta Mool C. , Bagienski Will , Shen Yang , Shu Chunying , Gibson Harry W. , Dorn Harry C.
Published: April 2011

Photovoltaic devices based on soluble conjugated polymers have gained great interest in recent years because of the potential low cost of production and ease of fabrication. PCBM ([6,6]-phenyl-C61-butyric acid methyl ester), a fullerene derivative, has been extensively investigated as a solution processable electron acceptor for bulk-heterojunction (BHJ) photovoltaic devices blended with conjugate polymers like P3HT [poly(3-hexylthiophene)]. Here, we investigated a novel solution processable organic semiconductor, C60(CN)2, as an electron acceptor for bulk heterojunction photovoltaic applications. Optical and electrical properties of C60(CN)2 are studied and compared with PCBM. Blend devices with P3HT and C60(CN)2 have been fabricated and compared with P3HT-PCBM devices. The effect of thermal annealing on the device performance is evaluated. Open circuit voltage, short circuit current, fill factor and total efficiency data are compared with PCBM based devices.
Electrodeposition of Cu2ZnSnS4 Thin Films Using Ionic Liquids
Authors: Chan C.P. , Lam H. , Wong K.Y. , Surya C.
Published: April 2011

We report the growth of Cu2ZnSnS4 (CZTS) thin films by electrodeposition in ionic liquid. Sulfurization was performed in elementary sulfur vapor environment at 450°C for 2 hours. The X-ray diffraction analysis indicated that the film has a stannite structure with preferred grain orientation along (112). Photo-absorption measurement of the sample was performed from 500 nm to 990 nm. It is found that the energy bandgap of the film is about 1.49eV and the absorption coefficient is found to be of the order of 104cm-1.
Effects of Growth Parameters on Surface-morphological, Structural and Electrical Properties of Mo Films by RF Magnetron Sputtering
Authors: Kuo Shou-Yi , Chang Liann-Be , Jeng Ming-Jer , Lin Wei-Ting , Lu Yong-Tian , Hu Sung-Cheng
Published: April 2011

This work reports on the fabrication and characterization of Mo thin films on soda-lime glass substrate grown by reactive RF magnetron sputtering. Film thickness was measured by x-ray step surface profiler. The structural properties and surface morphology were analyzed by x-ray diffraction (XRD), atomic force microscope (AFM) and scanning electron microscopy (SEM). Electrical properties were measured by four-point probe. It was found that the growth parameters, such as argon flow rate, RF power, film thickness, have significant influences on properties of Mo films. The strain on films revealed the complicated relationship with the working pressure, which might be associated with micro structures and impurities. In order to improve the adhesion and electricity, we adopted a two-pressure deposition scheme. The optimal thickness and sheet resistance are νm and 0.12 ω The mechanisms therein will be discussed in detail. Furthermore, we also investigated the diffusion property of Na ion of double Mo films sputtered on soda-lime glass. Our experimental results could lead to better understanding for improving further CIGS-based photovoltaic devices.
Impact of Advanced Fuel Cycles on Geological Disposal
Authors: Marivoet Jan , Weetjens Eef
Published: April 2011

In recent years the increasing oil prices and the need for carbon-free energy to limit global warming have resulted in a revival of interests in nuclear energy. Advanced nuclear fuel cycles are being studied worldwide. They aim at making more efficient use of the available resources, reducing the risk of proliferation of nuclear weapons, and facilitating the management of the resulting radioactive waste. Recently, the Red-Impact project has investigated the impact of a number of representative advanced fuel cycles on radioactive waste management, and more specific on geological disposal. The thermal output of the high-level waste arising from advanced fuel cycles in which all the actinides are recycled is reduced with a factor 3 for a 50 years cooling time and with a factor 5 for a 100 years cooling time in comparison with the spent fuel arising from the once-through fuel cycle. This reduction of the thermal output allows for a significant reduction of the length of the disposal galleries and of the size of the repository. Separation of Cs and Sr drastically reduces further the thermal output of the high-level waste, but it requires a long-term management of those heat generating separated waste streams, which contain the very long-lived 135Cs. Recycling all the actinides strongly reduces the radiotoxicity in the waste, resulting in significantly lower doses to an intruder in the case of a human intrusion into the repository. However, the reduction of radiotoxicity has little impact on the main safety indicator of a geological repository, i.e. the effective dose in the case of the expected evolution scenario; for disposal in clay formations, this dose is essentially due to mobile fission and activation products. The deployment of advanced fuel cycles will necessitate the development of low activation materials for the new nuclear facilities and fuels and of specific waste matrices to condition the high-level and medium-level waste streams that will arise from the advanced reprocessing plants.
Cathodoluminescence of Actinides in Wide Gap Materials
Authors: Zamoryanskaya M.V. , Domracheva Ya.V. , Trofimov A.N. , Burakov B.E.
Published: April 2011

Single crystals and polycrystalline samples of durable actinide host phases such as garnet, zircon, and Ti-pyrochlore doped with varying amounts of U, Pu, Np and Am, were studied by cathodoluminescence (CL) spectroscopy. The following characteristic bands were identified: uranyl-ion [UO2]2+– 495 nm in garnet and pyrochlore; [UO4]2− – 710 nm in garnet; and Am3+ – in garnet and zircon at 550 nm, 614 nm, 740÷750 nm.
Mineralogical Control of the REE Distribution in the Fracture Fillings of an Uranium-Ore (Caceres-Spain)
Authors: Buil Belen , Gomez Paloma , Turrero Maria Jesus , Garralon Antonio
Published: April 2011

The behavior of actinides in a deeply buried radioactive waste cannot be predicted from evidence of their movement in geological environments in the geological past because these elements do not occur naturally in appreciable concentration. A useful means of reducing the uncertainty is to observe the behavior, both past and present, of chemical analogues in geological environment. In this sense, the rare earth elements (REE) have been used to predict the behaviour of actinide series elements in water-rock systems on account of the similar valence and ionic radii and high similarity in its electronic structure.

This paper describes the factors that control REE signature in the fracture fillings of an ancient uranium mine (dug granite) located in the Central-Iberian Zone of the Hesperian Massif (Caceres, Spain).

The study of REE distribution in the fracture fillings provides interesting information about the REE distribution in the hydrothermal fluids that flow through the system. In order to obtain this information, it is necessary to evaluate the control of different minerals in the total REE content of the fracture fillings.

The fracture fillings display a large mineralogical variety dominated by K-feldspars, quartz, plagioclase, micas, monazites, xenotimes, apatites, uraninites, inherited of the granites, and carbonates, quartz, apatites, phyllosilicates, sulphides and Fe-oxihydroxydes, neoformed in successive hydrothermal stages.

In general, the fracture fillings present different kind of REE patterns, just as positive or negative Eu anomalies. The REE final distribution in the fracture fillings is controlled by the presence of REE-minerals, both inherited and neoformed, and of carbonates, with great capacity to fractionate HREE in the system. On the other hand, the chemical composition of the carbonates and accessory minerals is responsible, as a last resort, for the Eu anomalie (positive or negative) observed in the fracture fillings.
XAFS of Pu and Hf LIII Edge in Lanthanide-Borosilicate Glass
Authors: Shiryaev A.A. , Zubabichus Ya.V. , Stefanovsky S.V. , Ptashkin A.G. , Marra J.C.
Published: April 2011

Lanthanide-Borosilicate (LaBS) glass capable to dissolve up to ∼10 wt.% PuO2 is designed for immobilization of plutonium-bearing wastes. The sample of LaBS glass with a target chemical composition (wt %): 9.0 Al2O3, 11.8 B2O3, 12.2 Gd2O3, 6.3 HfO2, 17.2 La2O3, 13.6 Nd2O3, 9.5 PuO2, 18.1 SiO2, 2.3 SrO was prepared from PuO2 powder and mechanically activated mixture of chemicals at 1500 °C. The obtained product was visually homogeneous. Xraydiffraction of the as-prepared glass showed that it mostly consists of a vitreous phase withsmall amounts of crystalline PuO2 (or PuO2-HfO2 solid solution with minor HfO2), britholite andan oxide with a fluorite structure and a composition close to GdHfO1.75. The crystalline fractionincreased after storage for ∼1 year. Magnitude of the FT of EXAFS spectrum at Pu LIII edgeshows that the peak due to first coordination sphere is much more intense than that of the secondshell. This indicates that though some Pu entered crystalline phases (mainly distorted PuO2), itsmajor fraction remained in the vitreous phase. Fit of the spectrum (R-factor = 0.02) gives thefollowing distances: R (Pu-O1)1 = 1.98 (σ = 0.04), R (Pu-O1)2 = 2.18 (σ = 0.04), R (Pu-O1)3= 2.35, R (Pu-Pu) = 3.72 (σ = 0.04), R (Pu-O2) = 4.4 (σ = 0.06). Oxygen environment ofthe Pu4+ ions in the vitreous phase resembles axially squeezed tetragonal pyramid with acoordination number ∼5. The distances ∼2.35 and ∼4.4 correspond to the pairs Pu-O in thefirst and the second shells in the crystalline PuO2. The distance ∼3.72 corresponds to the Pu-Pu and/or Pu-M (M = Ln, Hf) distances. EXAFS spectra of Hf show that Hf is present mostly in thevitreous phase with major neighbors at 2.17 and ∼3.2 A.
Initial Investigation Into the Vitrification of High Molybdenum Solids in Borosilicate Glass
Authors: Dunnett Barbara F. , Gribble Nick R. , Riley Andrew D. , Steele Carl J.
Published: April 2011

Sellafield Ltd operates a Waste Vitrification Plant (WVP) to immobilise the arisings from the reprocessing of spent nuclear fuel. Washout of solids from the base of waste storage tanks in preparation for decommissioning is likely to produce feeds enriched in molybdenum to the WVP. Vitrification of such feeds in the borosilicate glass formulation currently used by the WVP for vitrification of reprocessing waste has been investigated to determine the maximum achievable loading of MoO3.

The vitrification of molybdenum in the absence and presence of reprocessing waste was studied. A number of glasses were manufactured in the laboratory containing various waste loadings. The resultant glasses were examined both visually and under the scanning electron microscope for the presence of any phase separation. Additional aluminium was added to the glasses manufactured in the absence of reprocessing waste to improve the durability of the glass. In borosilicate glass containing 3.5 wt% Al2O3 the onset of a molybdenum phase separation was observed in glasses containing 2.6 wt% MoO3. In the presence of Magnox reprocessing waste, phase separation was observed when the product contained >3.8 wt% MoO3. Soxhlet durability testing of a selection of the glasses manufactured was carried out. The Soxhlet durability of glasses in the absence of phase separation was good.
Corrosion Behavior of Simulated LLW Glass in Deionized Water
Authors: Maeda Toshikatsu , Yamaguchi Tetsuji , Hotta Katsutoshi , Mizuno Tsuyoshi , Banba Tsunetaka
Published: April 2011

Static leach tests were conducted for simulated low-level radioactive waste (LLW) glass in deionized water at 90 °C for up to one year to investigate the dissolution mechanism of LLW glass. Widely studied leaching behavior of high-level radioactive waste (HLW) glass is referred in discussing the dissolution mechanism. LLW glass is characterized by higher sodium (Na) and aluminum (Al) contents than HLW glass, about twice as high as R7T7, with its SiO2 content close to HLW glass. Powdered simulated LLW glass of three different chemical compositions was tested with the glass-surface-to-water-volume ratio of 2,000 m−1. The release rates of boron (B), widely used as an indicator of dissolution for HLW glass, decreased with time during leaching, as commonly observed in similar tests for HLW glass. The pH of the leachate was stable around 11.3 - 11.6, which is higher than those in similar tests for HLW glass by one pH unit or more. The concentrations of Al in the leachates were higher compared to data for HLW glass by two orders of magnitude. The high concentration seems to be caused by higher pH. In the leachate condition of the present tests, a zeolitic mineral (analcime) is thermodynamically more stable than amorphous silica (SiO2(am)) which is known to control the concentration of dissolved silica (Si) with respect to HLW glass. The present results imply that dissolution of the LLW glass is accompanied with formation of analcime under virtually closed systems such as geological repository where the groundwater flow rate is quite low.
Phase Formation in the Vitrification of Savannah River Site SB4 HLW Sludge Surrogate Using Frit and Glass Forming Chemicals
Authors: Stefanovsky O.I. , Stefanovsky S.V. , Akatov A.A. , Marra J.C.
Published: April 2011

Phase formation mechanisms associated with the vitrification of Savannah River Site (SRS) Sludge Batch 4 (SB4) high level waste surrogate with high iron and aluminum contents were studied by infrared spectroscopy (IRS), X-ray diffraction (XRD) and optical microscopy. Two mixtures at 50 wt.% SB4 waste loading were prepared as slurries with a water content of ∼50 wt% using a waste surrogate and commercially available Frit 503-R4 (Li2O – 8 wt%, B2O3 – 16 wt%, SiO2 – 76 wt%) or mixture of chemicals (LiOH·H2O, H3BO3, SiO2). The mixtures were air-dried at a temperature of 115 °C and heat-treated at 500, 700, 900, 1000, 1100, 1200, and 1300 °C for 1 hr at each temperature. IR spectra and XRD patterns of the products heat-treated at each temperature were recorded. In both the mixtures phase formation reactions started at low temperatures and yielded intermediate phases (sodalite, pyroxene-type, nepheline), and the reactions were mostly completed within the temperature range between 1000 and 1100 °C. The glassy materials prepared at 1200 and 1300 °C were composed of vitreous phase and magnetite/trevorite type spinel.
Application of Track Membranes for Additional Treatment of Water Coolant of Nuclear Reactor
Authors: U.S. Salihbaev , A.A. Kist , R. Malikov Sh. , V.P. Pikul , R.I. Radyuk , G.A. Radyuk , E.A. Danilova , N.M. Muhamedshina
Published: April 2011

Experiments on determination of operational effectiveness of track membranes with different diameter of pores (0.2 – 0.05 microns) for additional purification of water of the first contour of the reactor before ion-exchange resins were carried out. The track membranes detain products of corrosion, and also products of wearing of moving parts of the equipment by the size of > 0.05 microns. Filtration experiments on of water of the first contour of the exploratory reactor of VVR-SM have shown high performance of track membranes.
Interaction of Hydrogen Peroxide With Carbon Steel and Magnetite
Authors: Gimenez Javier , Casas Ignasi , Sureda Rosa , Pablo Joan de
Published: April 2011

Hydrogen peroxide is considered as one of the main oxidants formed due to the radiolysis of water. In a spent nuclear fuel repository, it is necessary to establish the interaction of hydrogen peroxide with the elements constituting the repository. The objective of this work is to study the consumption of hydrogen peroxide via reaction with the elements of the canister.

In this sense, two different series of experiments were conducted, with iron steel an magnetite, respectively. Each series consisted on three different experiments that contained a coupon of the solid and different hydrogen peroxide concentrations (10−4 mol·dm−3, 10−5 mol·dm−3 and 10−6 mol·dm−3). Hydrogen concentration in solution was measured at different intervals of time by means of chemiluminescence. At the end of the experiments, the coupons were studied by X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) in order to determine the possible secondary solid phases formed on the coupons.

In both series of experiments, a decrease of the hydrogen peroxide concentration in solution with time was observed. The determined consumption rates increased with hydrogen peroxide concentration and were higher in steel than in magnetite. The reaction orders relative to hydrogen peroxide concentration were very close to the unity on both solids.

The study of the carbon steel coupons by SEM at the end of the experiments showed that they were more attacked at higher hydrogen peroxide concentrations. On the other hand, the XRD measurements in the steel coupons showed that lepidocrocite (γ-FeO(OH)), and magnetite (Fe3O4) were formed on the coupon as iron secondary solid phases.
Effect of magnetism on precipitation of Cu in bcc Fe: Ab-initio based modeling
Authors: Gorbatov O.I. , Ruban A.V. , Korzhavyi P.A. , Gornostyrev Yu.N.
Published: April 2011

Theoretical modeling of the decomposition in bcc Fe-Cu alloys has been performed using a combined approach which includes ab-initio calculations of the effective cluster interactions and statistical-mechanical (Monte Carlo) simulations. We showed that the effective Cu-Cu and Cu-vacancy interactions in the bcc Fe matrix have a strong dependence on the global magnetic state of iron. As a result, all the related thermodynamic properties of the alloys (such as solubility limit and diffusivity) are expected to have a pronounced non-Arrhenius temperature behavior, originated from variation of the global magnetization with temperature. We find that strong Cu-vacancy interactions in the bcc Fe matrix lead to a remarkable effect of vacancies on the Cu precipitation and significantly modify the alloy decomposition kinetics under irradiation.
Effect of HBS Structure in Fast Release Fraction of 48 GWd/tU PWR Fuel
Authors: Pablo J. de , Serrano-Purroy D. , Gonzalez-Robles E. , Clarens F. , Martinez-Esparza A. , Wegen D.H. , Casas I. , Christiansen B. , Glatz J.-P. , Gimenez J.
Published: April 2011

Two important issues in Performance Assessment exercises regarding the alteration of Spent Nuclear Fuel (SNF) are the contribution of Instant or better called Fast release Fraction (FRF) and the effect of High Burn-Up Structure (HBS). Therefore this paper focuses on the effect of HBS in FRF of a PWR irradiated in a commercial reactor with a mean Burn-Up (BU) of 48 GWd/tU. Additionally, determined FRF are compared with previous experiments performed with PWR with a mean BU of 60 GWd/tU, in order to evaluate the effect of BU on FRF.

In order to study the HBS contribution, static leaching experiments are performed with two samples prepared from different radial positions, labeled Core, central region and Out, enriched with HBS. Two synthetic leaching solutions, bicarbonate and bentonitic granitic groundwater are used under oxic conditions.

The estimated FRF are calculated from the determined Fraction of Inventory in Aqueous Phase (FIAP) taking into account the inventory determined experimentally for each fraction.

Higher release is observed for Core sample, which can be an indicative that HBS does not increase the RN release. With the exception of Rb and Cs, which release is higher at lower BU, no clear effect of BU is observed within the studied range.
Rim Instant Release Radionuclide Inventory From French High Burnup Spent UOX Fuel
Authors: Roudil D. , Jegou C. , Broudic V. , Tribet M.
Published: April 2011

To assess the long-term behavior of spent fuel in a nuclear waste repository, the chemical reactions between the fuel and possible intruding water must be understood and the resulting radionuclide release must be quantified. The instant release fraction (IRF) source term assumed to be instantaneously accessible to water after the failure of the waste container. Some IRF values for different kinds of spent fuel are available in the literature. However, the possible contribution the rim restructured zone for high-burnup UOX fuels, was not necessary taken into account. A specific study of the leaching behavior of the rim zone has been carried out on a UOX fuel sample with a burnup of 60 GWd·t-1 and 2.8% FGR. The 134/137Cs and 90Sr rim IRF are effectively higher than the gap and grain boundary inventories (respectively 4.4 wt% and 0.3 wt% of the total Cs and Sr inventories). Nevertheless because of the relative small volume of this zone in the pellet, the impact of the rim inventory appears to be limited and the complete Cs and Sr IRF (gap, grain boundaries and rim), were estimated at 1.85 and 0.3 wt%, respectively
Supporting Development of Practical Designs for a Japanese HLW Repository
Authors: Makino Hitoshi , Umeki Hiroyuki , Ochi Yasuhiro , Hioki Kazumasa , Okubo Hiroo , Matsumoto Masaaki , Sato Osamu , Masuda Sumio , McKinley Ian G.
Published: April 2011

In preparation for actual repository implementation, designs that could be tailored to specific sites need to be considered. This requires a paradigm shift in design philosophy, moving away from a single reference design towards a flexible and systematic “catalogue” of engineered barrier components and associated repository infrastructure. To support this development, novel methodology for both developing and comparing repository design options for Japanese vitrified high-level radioactive waste (HLW) has been examined. This paper will outline the background of the project and, in particular, some novel approaches examined for facilitating optimisation of practical repository designs. It is complemented by a companion paper - Matsumoto et al: Application of Formal Knowledge Engineering Approaches to Develop A Design Catalogue for A Japanese HLW Repository -, which describes the repository design process in more detail and illustrates results of first dry runs of the methodology.
Reduction in the Thermal Conductivity of Thermoelectric Titanium Oxide by Introduction of Planar Defects
Authors: Harada Shunta , Tanaka Katsushi , Inui Haruyuki
Published: April 2011

Thermoelectric properties of a homologous series of Magnéli phase titanium oxides TinO2n-1 (n = 2, 3..) have been investigated. Dense polycrystalline specimens with nominal composition of TiO2-x (x = 0.10, 0.20) have been prepared by conventional hot-pressing. X-ray diffraction analysis has revealed that prepared specimens are slightly reduced during hot-pressing. Electrical conduction is of n-type for all prepared titanium oxides and electrical resistivity and absolute values of Seebeck coefficient decrease with increasing oxygen deficiency. The carrier concentration of Magnéli phase titanium oxide increases with increasing oxygen deficiency. Lattice thermal conductivity decreases with increasing oxygen deficiency by more than 60% at room temperature and 40% at 773K compared to TiO2, which can be due to the presence of dense planar defects. The largest thermoelectric figure of merit Z, 1.6×10-4 K-1 at 773K, was obtained in TiO1.90 hot pressed specimen.
Transient Thermal Imaging of Si/SiGe superlattice and bulk Si microrefrigerators
Authors: Michel Hélène , Coppard Rémi , Kendig Dustin , Christofferson James , Maize Kerry , Shakouri Ali
Published: April 2011

In this paper, we present a systematic study of the transient cooling in different Si/SiGe superlattices as well as bulk silicon microrefrigerators. Transient thermoreflectance imaging is used to obtain the temperature map of the device with sub micrometer spatial, 100ns temporal and 0.1C temperature resolution. It is shown that Peltier cooling dominates in the first 10-30 microseconds before Joule heating in the active and buffer layers reach the top surface. The transient characterization shows that at the optimum current for maximum steady-state cooling, the response of bulk silicon cooler is 25% faster than the 3 microns thick superlattice device and that of the 6 microns thick superlattice is 25% slower. However, it is possible to increase the cooling speed by a factor of two or three, down to 3.6 microseconds, by overdriving the current at the expense of the reduced steady-state cooling.
Thermo-Magnetic, Piezo-Electric and Electroactive Energy Harvesting Devices
Authors: Jean-Mistral Claire , Carlioz Louis , Defosseux Maxime , Marzencki Marcin , Cugat Orphèe , Delamare Jèrôme , Basrour Skandar
Published: April 2011

We present three approaches to harvesting ambient energy, based on complementary physical effects in order to exploit three kinds of energy available for harvesting:

Mechanical vibrations

Mechanical vibration energy can be harvested with resonant mechanical structures excited by the vibrations; this scavenged energy is then transformed into electricity by piezoelectric materials. We propose to use thin piezoelectric layers deposited on the resonant structure.

An on-chip integrated prototype, using a seismic mass at the end of a Si cantilever beam coated with a piezoelectric AlN film (overall volume 5 mm3), produces 30 nW of rectified power at 3 V under 0.4 g acceleration, which is enough to power a wireless sensor. Power conditioning electronics adapted to ultra-low voltage input is also proposed, which can efficiently charge a storage capacitor under very low accelerations. The fully micro-fabricated System on a Package combines a MEMS generator and ASIC power management circuit.

Evolutions of ambient temperature

A permanent magnet is attached to a PZT/brass bimorph, and placed near a "thermo-magnetic" material (FeNi) which Curie temperature can be tuned around the ambient. During slow cooling or heating by the ambient air, the FeNi magnetic properties vary slowly and thus the attraction force between the FeNi and the NdFeB magnet varies slowly. Despite the slow global evolutions, the opposition between the linearity of the bimorph bending and the strong non-linearity of the magnetic attraction over distance leads to brutal clamping or release of the magnet around Tc: the piezo can then efficiently convert these fast deformations into electricity. Operational temperature range can be set by tuning the FeNi composition to obtain a predefined Curie point; hysteresis between the cooling/heating thresholds can be tuned by modifying the gap between the magnet and the FeNi.

The cm-scale prototype generates a peak voltage of 35 V on release (T > Tc). For a discharge time of 0.1 s through a 1 MΩ load, the total energy harvested is 13.5 μJ per stroke, i.e. 1.35 mW of average power (respectively -14 V, 2.2 μJ and 0.22 mW on clamping when T < Tc). Output power is surprisingly constant for various load values tested. Scaling effects must now be addressed to assess the feasibility of an integrated MEMS generator and its potential efficiency.

Low-frequency, large amplitude bending from human motion:

A very light, flexible electro-active polymer membrane (50 x 30 mm, 31 μm thick) operates in a large frequency spectrum from quasi-static to dynamic range. It scavenges 0.1 mJ per cycle at 1 Hz, under 170 V and constant charge Q: 100 μW is enough to supply a low-power system.

Improvements under investigation include achieving poling voltage with piezoelectric polymer or electrets polymer, using multi-stack scavengers to miniaturize the structure and to decrease the poling voltage V, and integration into textile.