bluuebunny/crossref_metadata_2025_split huggingface dataset:
Alpha-Decay Radiation Damage Study of a Glass-Bonded Sodalite Ceramicwaste form
Authors: Frank S.M. , Barber T. L. , DiSanto T. , Goff K. M. , Johnson S. G. , Jue J-F , Noy M. , O'Holleran T. P. , Sinkler W. 
Published: April 2011

ABSTRACTEffects of alpha decay on the ceramic waste form used to immobilize fission products and actinides accumulated from electrometallurgical treatment of Department of Energy metallic spent nuclear fuel is being studied. This involved the preparation of a surrogate ceramic waste form containing two-weight percent plutonium-238 and monitoring changes to the waste form resulting from alpha-decay damage. The phase assembly of the ceramic waste form consists of glass-bonded sodalite with small quantities of nepheline, halite and plutonium dioxide. The waste form has been monitored for three years and has acquired an internal alpha-decay dose of 1 × 1018 disintegrations per gram of material. Methods used to monitor the material include: density determination, chemical durability measured by immersion testing, microscopy and powder xray diffraction. The investigation has, to date, found little alteration to the waste form due to alpha-decay damage. X-ray diffraction analysis has detected a unit cell volume increase of 0.7 percent of the plutonium dioxide phase. Furthermore, bubbles and/or voids have been observed by transmission electron microscopy in the sodalite and glass phase. The origin of these defects is unclear and under investigation.
Ion Irradiation Effects in Synthetic Garnets Incorporating Actinides
Authors: Utsunomiya Satoshi , Wang Lu-Min , Yudintsev Sergey , Ewing Rodney C. 
Published: April 2011

ABSTRACTRadiation durability of garnet [A3B2(XO4)3; Ia3d; Z=8] has been examined by 1.0 MeV Kr2+ irradiation with in situ transmission electron microscopy over the temperature range of 50 to 1070 K. The targets were five synthetic garnets incorporating various contents of actinides and andradite, Ca3Fe2Si3O12. The synthetic garnets were silicates (N series) and ferrate-aluminate series (G series).The critical amorphization temperatures (Tc), above which amorphization does not occur, were determined to be 1050 K for N77, 1130 K for N56, 1100 K for G3, 890 K for G4 and 1030 K for andradite. Tc of the synthetic garnets increased as the average atomic mass of the garnet increased. The maximum transferred energy by ballistic interaction was positively correlated to the atomic mass. The larger cascade size that formed due to the larger Emax might lead to the higher Tc.
Experimental Determination of the Deliquescence Relative Humidity and Conductivity of Multicomponent Salt Mixtures
Authors: Yang Lietai , Pabalan Roberto T. , Browning Lauren 
Published: April 2011

ABSTRACTThe conductivity of hygroscopic salt deposits containing Na+, K+, NO3– and Cl– ions was measured in air as a function of relative humidity at constant temperatures. The deliquescence relative humidity (DRH) of multicomponent salts containing Na+, K+, NO3– and Cl– was also determined experimentally. The results of the conductivity experiments show that the conductivity of initially dry salt deposits start to increase after reaching a relative humidity value that is 15 to 20% lower than the DRH of the salt. When the DRH is reached, the conductivity increases dramatically as the salt dissolves and transforms into a saturated aqueous phase. The increase in conductivity at humidities below the DRH is attributed to the adsorption of water on the surface of the salt particles. Because of the increase in conductivity, the initiation of aqueous corrosion of metals in contact with hygroscopic salts may occur at a relative humidity much lower than the DRH of the salt. Thus, the onset of aqueous corrosion of metallic nuclear waste package and the drip shield may be earlier, the duration may be longer, and the temperature at which it occurs may be higher than assumed based on the DRH of the salt. The results of the DRH experiments show that the DRH of a salt mixture is usually significantly lower than that of any of its component pure salt.
Effect of Redox Conditions on the Sorption of Plutonium onto Geological Materials
Authors: Berry J.A. , Brownsword M. , Ilett D.J. , Linklater C.M. , Mason C. , Tweed C.J. , Yui M. 
Published: April 2011

ABSTRACTThis paper presents the latest results from a programme of generic sorption studies undertaken to increase confidence in data underpinning the performance assessment for a potential high-level radioactive waste repository in Japan. The sorption of plutonium onto basalt and sandstone was studied as a function of redox conditions that ranged from strongly reducing to oxidising. Geochemical modelling was used to aid experimental design and the interpretation of results.
Incorporation of Cerium and Neodymium in a Uranyl Hydroxide Solid
Authors: Kim C.W. , Wronkiewicz D.J. , Finch R.J. , Buck E.C. 
Published: April 2011

ABSTRACTThe migration behavior of radionuclides in a nuclear-waste repository will be influenced, in part, by their equilibrium solubilities in the presence of radionuclide-bearing solids and/or adsorption affinities as trace components onto the surfaces of solid host phases. Uranium phases that precipitate on the surface of altered spent nuclear fuel may thus influence the mobility of radionuclides released in the near-field environment, since by proximity, these will be the first phases that the radionuclides encounter following their release from the spent fuel matrix.We have evaluated the potential for incorporating radionuclides into crystalline compounds by precipitating uranyl phases from aqueous solutions containing dissolved rare earth elements (REE; 2.1 ppm Ce4+, 4.6 ppm Ce4+, or 286 ppm Nd3+). Rare earth elements serve both as monitors for evaluating the potential behavior of REE radionuclides and as surrogate elements for the actinides (e.g., Ce4+ and Nd3+ for Pu4+ and Am3+, respectively). Although the crystalline compound that formed in the present set of experiments has not been positively identified, x-ray diffraction profiles suggest the presence of a uranyl hydroxide (UO2(OH)2) as the principal reaction product. An analysis of the crystalline products indicate a progressive decrease in concentration of cerium; from 26, to 20, and finally 11 ppm for crystals produced in 7-, 35-, and 190-day tests, respectively (Kd = 14, 11, 3, respectively). Results with neodymium display a similar trend, with concentrations in the solid decreasing from 1240 to 922 ppm between 7 and 35 days of reaction (Kd = 14 and 11, respectively). The decreasing concentration of REEs in the uranyl crystals can be correlated with both a coarsening in crystal size and a decrease in the concentration of dissolved uranium over time. Thus, REE incorporation in the crystalline solids decreases in conjunction with a decrease in the ratio of surface area/volume of the crystals, a decrease in the rate of crystal growth as uranium concentrations are lowered, or both. These data also suggest that adsorption of REE (and by analogy, actinides) onto crystal surfaces and subsequent trapping by crystal overgrowth processes may play key roles in the limiting the mobility of radionuclides in a nuclear waste repository.
Demonstration of the Feasibility of Recovering Americium and Curium Isotopes from a Lanthanide Borosilicate Glass
Authors: Rudisill Tracy S. , Peeler David K. , Edwards Thomas B. 
Published: April 2011

ABSTRACTA solution containing kilogram quantities of highly radioactive isotopes of americium and curium (Am/Cm) is currently stored in a process tank at the Department of Energy's Savannah River Site. This tank and its vital support systems are old, subject to deterioration, and prone to possible leakage. To address the stabilization of this material, vitrification of the isotopes has been considered. Potentially, the glass could be shipped to the isotope production and distribution programs at the Oak Ridge National Laboratory for californium-252 production and use by the transplutonium research community. However, before the Am/Cm could be used in these programs, it must be recovered from the glass.To demonstrate the feasibility of recovering the Am/Cm isotopes from a glass, a series of small-scale experiments was performed as part of a compositional variability study. Glasses fabricated during the study utilized lanthanide elements as surrogates for Am/Cm due to the high specific activity of these materials. In the dissolution tests, glass formulations representative of potential uncertainties in the composition of the Am/Cm solution were fabricated, ground to a -35 to +60 mesh particle size, and dissolved in 8M nitric acid at 110°C. Under these conditions, at least 98% of the lanthanide oxides in the glass dissolved in less than 2 h meeting a recoverability criterion established for the vitrification process and imposing no limitations on the acceptable glass composition region.Dissolution of the lanthanide borosilicate glasses was described by a spherical particle model based on the observation that the rate of change of the mass to surface area ratio remains constant. Calculation of dissolution rates using the model showed that the rate was proportional to the lanthanide oxide concentration in the glass. When silicon oxide (SiO2) was replaced with a lanthanide element at higher (simulated Am/Cm) loadings, the glass became more easily dissolved in nitric acid due to the solubility of the lanthanide oxides compared to SiO2.
Aging of a Bitumen Waste form in Wet Repository Conditions
Authors: Ojovan M.I. , Ojovan N.V. , Golubeva Z.I. , Startceva I.V. , Barinov A.S. 
Published: April 2011

ABSTRACTSIA ‘Radon’ has been performing field tests of bitumen waste forms holding low and intermediate level wastes (LILW) for about three decades. The waste forms were made at an industrial bituminization plant from the actual LILW wastes. This paper presents results from analyzing the samples of the bitumen waste material taken from the bulky bitumen block with waste salts loading 31 wt.% after storing the block in a shallow-ground repository for 12 years. Rich in natrium nitrate NPP-operational waste was incorporated in bitumen.Salts were separated from bitumen in some waste form samples. Non-homogeneous distribution of both salts and radionuclides was detected in vertical direction of the bitumen block. Specific radioactivity of the extracted bitumen was of the same order as the specific radioactivity of salts, in some cases even greater.Bitumen samples free of salts were further separated into three main bitumen fractions, asphaltenes, saturated and aromatic hydrocarbons, using methods of solvent extraction. Essentially all radioactivity of the bitumen was associated with the asphaltene fraction. Aging of the bitumen waste form led to increase in asphaltene fraction content (with minimum 4%) and hardening of the waste material. The study has revealed a significant transfer of the waste salts radioactivity to the asphaltene fraction of the bitumen matrix. Changes in the properties of the bitumen waste form will be taken into consideration in modeling the long-term behavior of the bitumen waste materials under repository conditions.
Diffusion Behavior of Iron Corrosion Products In Buffer Materials
Authors: Idemitsu Kazuya , Yano Seiji , Xiaobin Xia , Inagaki Yaohiro , Arima Tatsumi , Mitsugashira Toshiaki , Hara Mitsuo , Suzuki Yoshimitsu 
Published: April 2011

ABSTRACTCarbon steel is one of the candidate overpack materials for high-level waste disposal and is expected to assure complete containment of vitrified waste glass during an initial period of 1000 years in Japan. The lifetime of the carbon steel overpack will depend on its corrosion rate. The corrosion rate of carbon steel is reduced by the presence of buffer material such as bentonite. Buffer material will delay the supply of corrosive materials and discharge of corrosion products through it. Carbon steel overpack will be corroded by consuming oxygen introduced by repository construction after closure of repository and then will keep the reducing environment in the vicinity of repository. The reducing condition will be expected to retard the migration of redox-sensitive radionuclides by lowering their solubilities. Therefore, the diffusion of corrosion products of iron in buffer material is important to discuss the corrosion rate of overpack, migration of redox-sensitive radionuclides and properties of buffer material. The purpose of this paper is to study diffusion behavior of a corrosion product of iron in compacted bentonites under a reducing condition with a carbon steel. The diffusion mechanism of iron in the compacted bentonites were discussed by estimation of iron species in the bentonite pore water. There were two diffusion paths of iron in the compacted bentonites used in this study; the fast path has low capacity of iron, ca. 1wt%, and large apparent diffusion coefficient, ca. 10−12m2/s and the slow path has high capacity of iron, ca. 10wt%, and small apparent diffusion coefficient, ca. 10−14m2/s.
Origins of Discrepancies Between Kinetic Rate Law Theory and Experiments in the Na2O-B2O3-SiO2 System
Authors: McGrail B. P. , Icenhower J. P. , Rodriguez E. A. 
Published: April 2011

ABSTRACTDiscrepancies between classical kinetic rate law theory and experiment were quantitatively assessed and found to correlate with macromolecular amorphous separation in the sodium borosilicate glass system. A quantitative reinterpretation of static corrosion data and new SPFT data shows that a recently advanced protective surface layer theory fails to describe the observed dissolution behavior of simple and complex silicate glasses under carefully controlled experimental conditions. The hypothesis is shown to be self-inconsistent in contrast with a phase separation model that is in quantitative agreement with experiments.
Leaching of Np and Tc From Doped Nuclear Waste Glasses in Clay Media: The Effects of Redox Conditions
Authors: Pirlet Véra , Lemmens Karel , Iseghem Pierre Van 
Published: April 2011

ABSTRACTBoom Clay is the candidate geologic formation in Belgium for disposal of vitrified high level waste. In the waste glass, 237Np and 99Tc are some of the principal radionuclides. The leaching behaviour of these nuclides has been studied in dissolution tests involving glass doped with 237Np and 99Tc and was found to depend strongly on the redox conditions of the media contacting the glass. Static tests with the reference R7T7 glass and the reference PAMELA SM539 glass were performed in two clay media that may interact with the glass during the geological disposal. The first test medium consisted of FoCa-clay (Fourges-Cahaignes-clay), which is an oxidised clay. The second test medium was a mixture of backfill material, consisting mainly of FoCa-Clay, with metal corrosion products and Boom Clay. Lower Np and Tc concentrations were found in Boom Clay compared to FoCa-clay. In FoCaclay, Np and Tc were predominately in their oxidised form. Although Tc is mostly present in the soluble pertechnetate form, the Np concentrations are lower than expected for the chemistry of Np(V) in the medium. The concentrations of the radionuclides are steady-state concentrations rather than thermodynamic concentrations. Different mechanisms can be invoked to explain these Np concentrations. In Boom Clay, the measured Np concentrations are close to the solubility limit whereas the Tc concentrations are slightly higher than those calculated in Boom Clay at thermodynamic equilibrium. The initial specific activity of the radionuclide in the glass was found to influence the soluble concentration. Np and Tc were not found to be retained in the glass reaction layer for both media.
Corrosion Tests of Lwr Fuels – Nuclide Release
Authors: Finn Patricia A. , Tsai Yifen , Cunnane James C. 
Published: April 2011

ABSTRACTTwo high burnup BWR fuels [64 and 71 (MWd)/kgU], one of which contained 2% Gd, and two low burnup PWR fuels [30 and 45 (MWd)/kgU], are tested by dripping groundwater on the fuel under oxidizing and hydrologically unsaturated conditions for 2.4 and 8.2 yr, respectively, at 90°C. The 99Tc, 129I, 137Cs, 97Mo, and 90Sr releases are presented to show the effects of reaction time and of gadolinium (Gd) on nuclide release. For the PWR fuels, the five nuclides have similar fractional release rates at 8.2 yr. For the BWR fuels, the presence of 2% Gd reduced the 99Tc cumulative release fraction after 2.4 yr by about an order of magnitude from that of a fuel with a similar burnup but without added Gd.
Radiation Effects in Crystalline Oxide Host Phases for the Immobilization of Actinides
Authors: Weber William J. , Ewing Rodney C. 
Published: April 2011

ABSTRACTRadiation effects from alpha-decay events in crystalline oxides, which are proposed for the immobilization of actinides, often lead to amorphization, macroscopic swelling and order-of-magnitude increases in dissolution rates for all of the phases currently under consideration. However, the results of systematic experimental studies using short-lived actinides and ion-beam irradiations, studies of radiation effects in U- and Th-bearing minerals, and the development of new models of the damage process over the past 20 years have led to a substantial increase in the understanding of the processes of damage accumulation in apatite, zircon, perovskite, zirconolite, and pyrochlore/fluorite structures. This fundamental scientific understanding now provides a basis for predicting the performance of nuclear waste forms in a radiation field. One of the recent successes of these studies has been the discovery of a class of radiation-resistant pyrochlore/fluorite structures that can serve as highly durable, radiation-resistant host phases for the immobilization of actinides.
Performance Assessment of Geological Disposal of High-level Radioactive Waste in a Plastic Clay formation
Authors: Marivoet Jan , Sillen Xavier , Mallants Dirk , Preter Peter De 
Published: April 2011

ABSTRACTIn Belgium the possibilities to dispose of high-level waste in the plastic Boom Clay formation has been studied since 1975. Consequently many results of the site characterisation programme are already available. Various performance assessments have been carried out dealing with the disposal of high-level waste arising from reprocessing and with direct disposal of spent fuel. The performance assessment consists of two main steps: scenario development and consequence analyses. The scenario analysis is based on a catalogue of features, events and processes (FEPs) having the potential to influence the behaviour of the repository system. Two main groups of scenarios are distinguished. The normal evolution scenario, including a number of variants, treats the FEPs that are fairly sure to take place. Altered evolution scenarios focus on FEPs having a probability of occurrence lower than one but that might influence the performance of the repository system. For the impact analyses, a robust concept approach was introduced, which focused the analyses on a limited number of well-characterised barriers and processes. The impact analyses are complemented with sensitivity and uncertainty analyses based on deterministic and probabilistic approaches.
Engineered Films of Bombyx mori Silk with Poly(ethylene oxide)
Authors: Jin Hyoung-Joon , Park Jaehyung , Cebe Peggy , Kaplan David L. 
Published: April 2011

ABSTRACTPhase separation into controllable patterned microstructures was observed for Bombyx mori silkworm silk and poly(ethylene oxide) (PEO) (900,000 g/mol) blends cast from aqueous solution. Solution blending was used to incorporate water-soluble PEO into silk to enhance elasticity and hydrophilicity. The sizes of the globule fibroin phase ranged from 3.1±0.9 μm to 18.2±2.1 μm depending on the ratio of silk/PEO. Optical microscopy and SEM analysis confirmed the micro-phase separation between PEO and silk. Surface properties were determined by contact angle. The PEO can be easily extracted from the films with water to generate silk matrices with definable porosity and enhanced surface roughness. These blend films formed from two biocompatible polymers provide new potential tissue engineering scaffolds and controlled release drug delivery materials.
Human Bone Marrow Stem Cell Responses on Electrospun Bombyx mori Silk Fibroin
Authors: Jin Hyoung-Joon , Chen Jingsong , Karageorgiou Vassilis , Altman Gregory H. , Kaplan David L. 
Published: April 2011

ABSTRACTElectrospinning for the formation of nanoscale diameter fibers has been explored for high performance filters and biomaterial scaffolds for vascular grafts or wound dressings. Fibers with nanoscale diameters provide benefits due to high surface area. In this study we used electrospinning for protein-based biomaterials to fabricate scaffolds from aqueous regenerated silkworm silk, Bombyx mori,. Adhesion, spreading and proliferation of human bone marrow stem cells (hBMSCs) on electrospun silk was characterized. Scanning electron microscopy (SEM) and MTT analyses demonstrated that the electrospun silk matrices promoted hBMSC attachment and proliferation over 10 days in culture. The responses of the hBMSCs on the electrospun silk matrices, combined with the biocompatibile properties of the silk fibroin protein matrix, suggest potential for use of this biomaterial as scaffolds for tissue engineering.
Electrospinning Nanofibers of PANI/PMMA Blends
Authors: Desai Keyur , Sung Changmo 
Published: April 2011

ABSTRACTElectrically conducting organic polymers are a novel class of ‘synthetic metals’ that combine the chemical and mechanical properties of polymers with the electronic properties of metals and semiconductors. Electronically conducting polymers have been studied extensively owing to their applications in energy conversion devices, sensors, electro chromic devices, electromagnetic interference shielding (EMI), electronic circuits etc. Polyaniline - an organic conducting polymer - has been blended with poly methyl methacrylate and the blends have been electrospun to produce conducting nanofibers. The electrospun blends have been characterized to study fiber morphology and formulate conditions for nanofiber formation.
Bisperfluorophenyl-Substituted Thiophene Oligomers. Organic Semiconductors with Complementary-Type Carrier Mobility
Authors: Facchetti Antonio , Katz Howard E. , Marks Tobin J. 
Published: April 2011

ABSTRACTThe design, synthesis, and properties of two mixed perfluorophenyl-thiophene oligomers 5,5″′-diperfluorophenyl-2,2′:5′,2″:5″,2″′:5″′,2″″:5″″,2″″′-quaterthiophene (2) and 5,5′-bis{1-[4-(thien-2-yl)-2,3,5,6-tetrafluorophenyl)] }-2,2′-dithiophene (3) are presented. Molecular characterization included the following techniques: multinuclear NMR, DSC and TGA, optical UV-Vis and photoluminescence spectroscopy, and cyclic voltammetry. Thin films can be easily grown by vacuum evaporation and have been characterized by optical UV-Vis and photoluminescence, XRD, and field-effect transistor measurements. Electron and hole mobilities of 0.06–0.08 cm2/(V s) and 0.001–0.003 cm2/(V s) were found for 2 and 3, respectively.