bluuebunny/crossref_metadata_2025_split huggingface dataset:
Utilization of Valuable Metals from High Level Waste-Decomposition of Water Using Semiconductor Photocatalytic Method Induced by Gamma Ray-
Authors: Wada Y. , Kawaguchi K. , Myochin M. 
Published: April 2011

AbstractThe technique of radiolytic decomposition of water leading to hydrogen production was demonstrated to explore a new field in the utilization of radioactive platinum group metals recovered from high level radioactive waste (HAW) and radioactivity of HAW. The radiation photocatalytic method is based on the technique to decompose water on platinized semiconductor particles under UV-light irradiation which has been widely investigated to develop an alternative energy source. In this study gamma radiation from Co-60 source was applied to produce hydrogen instead of UV-light and a significant amount of hydrogen evolved from catalyst-water suspension. Our preliminary experiments proved a possibility of converting the energy of radiation ionization into chemical energy (hydrogen) by the radiation photocatalytic method.
Sharp Fronts within Geochemical Transport Problems
Authors: Grindrod Peter 
Published: April 2011

AbstractWe consider some reactive geochemical transport problems in groundwater systems. When incoming fluid is in disequilibrium with the mineralogy sharp transition fronts may develop. We show that this is a generic property for a class of systems where the timescales associated with reaction and diffusion phenomena are much shorter than those associated with advective transport. Such multiple timescale problems are relevant to a variety of processes in natural systems: mathematically methods of singular perturbation theory reduce the dimension of the problems to be solved locally. Furthermore we consider how spatial heterogeneous mineralogy can impact upon the propagation of sharp geochemical fronts.We develop an asymptotic approach in which we solve equations for the evolving geometry of the front and indicate how the non-smooth perturbations due to natural heterogeneity of the mineralogy on underlying ground water flow field are balanced against the smoothing effect of diffusion/dispersive processes. Fronts are curvature damped, and the results here indicate the generic nature of separate front propagation within both model (idealized) and natural (heterogeneous) geochemical systems.
Characterization of Slag Product from Plasma Furnace for Unsorted Solid Radioactive waste Treatment
Authors: Dmitriyev Sergey A , Stefanovsky Sergey V , Knyazev Igor A , Lifanov Fyodor A 
Published: April 2011

AbstractThe shaft furnace equipped with plasma-fuel burners for high temperature slagging treatment has been developed in State Corp.»RADON». A slag is considered as final wasteform. From this point of view a slag formation mechanism, radionuclides immobilization and basic slag properties have been studied. A chemical and phase compositions of institutional and nuclear power station waste slags were determined. Some details of slags structure were investigated by infra-red spectroscopy. A study of radionuclides distribution has shown that caesium and strontium are concentrated in the silicate slag constituent while iron and cobalt enter the metal fraction.
Radioactive Tracer Test to Develop a Recycling System for Operating Reactor Scrap Metal
Authors: Umemura A. , Kimura K. , Takahashi K. , Sakurai D. , Yamamoto M. , Abe S. 
Published: April 2011

AbstractA demonstration test using radio-isotope(RI) tracers during the manufacturing of inner drum shielding material from the recycling of operating reactor scrap metal was completed and the following results were obtained. The behaviour of five radionuclides (Mn-54. Co-60. Zn-65. Sr-85 and Cs-137) was established. The time-dependent behaviors of the radionuclides in molten steel and in slag were investigated. The radioactivity distributions in metal products were homogeneous. Dose equivalent rates in the working area were below background levels and radioactive dust concentrations in the air were below detection limits.
Radiation Effects Issues Related to U.S. Doe Site Remediation and Nuclear Waste Storage
Authors: Weber William J. , Ewing Rodney C. 
Published: April 2011

AbstractSite restoration activities at DOE facilities and the permanent disposal of nuclear waste generated at the same DOE facilities involve working with and within various types and levels of radiation fields. Radionuclide decay and the associated radiation fields lead to physical and chemical changes that can degrade or enhance material properties. This paper reviews the impact of radiation fields on site restoration activities and on the release rate of radionuclides to the biosphere from nuclear waste forms.
Alpha-Decay Damage of Cm-Doped Perovskite
Authors: Mitamura H. , Matsumoto S. , Tsuboi T. , Vance E. R. , Begg B. D. , Hart K. P. 
Published: April 2011

AbstractCurium-doped perovskite slurry, which had the nominal composition of Ca0.98919(Cm, Pu)0.0108l Al0.0108l Ti0.98919O3, was calcined at 750°C for 2 h and then hot-pressed at 1250°C and 29MPa for 2 h. The hot-pressed cylinder samples had the specific 244Cm activity of 22.3 GBq·g−l on 31 March 1993. Their average density was 4.083 g·cm−3 after the samples got a cumulative dose of 0.7}1017 α decays·g−l. Change in density of Cm-doped perovskite reached 0.8% at a dose of 5}1017 α decays·g−l. The rate of density change was slightly larger in the present perovskite material than in Cm-doped Synroc reported previously. Half-disk perovskite specimens, which had accumulated doses of 1.6}1017 and 4.0}1017 α decays·g−l, were MCC-1 leach tested in pH˜2 solution at 90°C for two months. The leach rates of these specimens derived from weight losses were 1.7 and 2.3 g·m−2·day−l, respectively. These high leach rates caused a significant increase in pH in the later stage of the leaching runs. As-leached surfaces of Cm-doped perovskite showed the formation of anatase (TiO2). For the first 28 days, the Ca and Cm leach rates at the two different doses increased with leach time. More damaged specimens tended to give higher leach rates. In the final 28-day leaching run, both leach rates at the two different doses converged on each lower values although the Cm leach rate was lower than the Ca leach rate by a factor of >20. Nonradioactive perovskite material showed similar changes in Ca leach rate and pH to the Cm-doped one although the as-leached surfaces of the former material showed much higher degree of alteration of perovskite to anatase.
Facilitated Transport of Charged Colloids in Geologic Media
Authors: Nagasaki Shinya , Tanaka Satoru , Suzuki Atsuyuki 
Published: April 2011

AbstractDiffusion of a charged colloidal particle in a two-dimensional simple shear flow was studied by means of Monte Carlo calculations and the effects of a bounding wall and charge of a particle on convective diffusion were elucidated. Taking charge effects into account has a marked effect on the diffusion behavior of the particle, increasing the migration distance. Diffusion of latex colloidal particles in a quartz-powder packed cell was also studied by through-diffusion methods. For the large latex colloidal particles, the effective diffusion coefficients measured are larger than those estimated by Stokes-Einstein equation.
Interactions of Actinide Analogues with Naturally Occurring Organic Matter
Authors: Stout Barbara E. , Deramos Cielito M. 
Published: April 2011

AbstractWe have studied the interaction of a low molecular weight alginic acid (ca. 7,000 daltons) with Ca2+, Mg2+, Eu3+ and La3+, using lanthanide luminescence spectroscopy (LLS) and 13C NMR. LLS results imply that nine-coordinate lanthanide ions lose six water molecules upon complexation with alginate, forming inner-sphere alginate complexes. In general, the 13C resonances in the NMR studies decreased in intensity as metal ion concentration increased, but the preference of a cation for repeating mannuronate and guluronate units (MM and GG blocks) varied greatly. The La3+ ion binds preferentially to the GG blocks, though some binding to the MM blocks is evident, while Eu3+ binds equally well to GG and MM blocks. Ca2+ shows a strong preference for the GG blocks only, while Mg2+ shows no evidence of binding to alginate at all. These preferences may be explained in terms of cation size, charge and coordination number. The diequatorial linkage pattern of sequential mannuronate residues leads to a flat ribbon-like structure with shallow cavities for the metal ions while the diaxial linkages of the guluronates allow a deeper, more size-specific cavity. Calcium has the optimum ionic radius for the GG cavities compared to the larger Eu3+ and La3+ ions. The smaller Mg2+ ion does not bind at all over the concentration range studied. This could be due to its large charge density to coordination number ratio that would make dehydration of this ion and subsequent complexation by alginate thermodynamically unfavorable.
The Biogeochemical Transport Code Drink: a Mechanistic Description.
Authors: Humphreys P. , Johnstone T. , Trivedi D. , Hoffmann A. 
Published: April 2011

AbstractDrinkis a 2D research code, which simulates the long term evolution of shallow, trenched, LLW disposal sites with significant groundwater flow. It employs a finite difference solver and is built around a geochemical transport model into which various functional units are interfaced. These units describe sorption, corrosion, microbiology, radionuclide decay, colloids, mineral precipitation and dissolution and gaseous release. Each of these units is described here, along with a 1 D simulation of uranium migration.
Diffusion of Radionuclides in Compacted Bentonite : Results from Combined Glass Dissolution and Migration Tests
Authors: Tsukamoto Masaki , Ohe T. , Fujita T. , HesbÖl R. , Hermansson H-P. 
Published: April 2011

AbstractDiffusion experiments of radionuclides in compacted sodium bentonite with a dry density of 1.0 g/cm3were performed in nitrogen gas atmosphere at 90 °C for 208 d and 375 d. The corrosion experiments of crushed radioactive glass, JSS-A, carried out simultaneously to provide the source of the radionuclides for the diffusion experiments. The normalized elemental mass losses of cesium isotopes and238Pu were lower than those of boron (ca. 10 g/m2) probably because of the difference of sorption and/or precipitation. The apparent diffusion coefficients of238Pu,234U and125Sb were determined to be 2x 10-14m2/s, 5x 10-12m2/s and 2x 10-12m2/s, respectively. The distribution coefficient of Pu estimated from the diffusion data was of the same order as that from batch sorption experiments. The glass corrosion and the plutonium diffusion were described by the geochemical codes PHREEQE, STRAG4 and GESPER. The calculation results well fitted the observed data.
Numerical Simulation of Solute Transport Instantaneously Injected in a Single Rock Fracture System: Inclusion of a Nonlinear Sorption Term
Authors: Fujikawa Yoko , Fukui M. 
Published: April 2011

AbstractThe effect of nonlinear Freundlich sorption isotherm on the transport of sorptive solute in a system of fracture and porous matrix was investigated through numerical simulation. To solve a set of partial differential equations of solute transport with nonlinear term, use of the Laplace transform Galerkin (LTG) technique was investigated. It was shown that the LTG method could be applied successfully to solve quasi-linearized transport equation. Sensitivity analysis showed that nonlinear sorption in porous matrix with order less than 1 increased the skewness of the breakthrough curve. The fitting of experimental effluent data using a transport model with nonlinear isotherms was also conducted.
Discrete Fracture Network Modelling of Tracer Migration Experiments at the Kamaishi Mine
Authors: Uchida Masahiro , Sawada Atsushi 
Published: April 2011

AbstractThis paper presents the results of a discrete fracture network modelling for the non-sorbing tracer migration experiments, which were conducted in the fractured rock at the Kamaishi mine. A newly developed in-plane heterogeneity model, which can address the channelling effects within a fracture, and the matrix diffusion model, which can simulate the retardation time due to the matrix diffusion adjacent to fracture were applied in this study. As a result, the matrix diffusion model better reproduces the general shape of breakthrough curves. The transport aperture At was approximately one order of magnitude larger than the hydraulic aperture Ac derived from the cubic law.
Behavior of Np, Pu, Am, Tc Upon Glass Corrosion in a Concentrated Mg(Ca)Cl2Solution
Authors: Grambow Bernd , Loida Andreas , Kahl Lothar , Lutze Werner 
Published: April 2011

AbstractThe objective of this investigation is to describe the extent to which Np, Pu, Am and Tc are mobilized from vitrified high-level radioactive waste into the near field of an HLW repository in a salt formation, when a hot and concentrated salt solution comes into contact with the glass. Waste form corrosion studies are conducted with a salt solution representing the composition of a fluid phase encountered in drill holes in the Gorleben salt dome. Test temperatures are determined by the designed maximum surface temperature of 200°C for the vitrified waste in the Gorleben salt. The following results were obtained: 1. pH changes of the radio-active leachate are the same as in inactive leachates. 2. The time and temperature dependence of the reaction for the radioactive glass are in excellent agreement with that of the inactive glass. 3. Np, Pu, Am, and Tc have not been reimmobilized in secondary minerals. Hence, mobilization of these radionuclides is governed by the kinetics of glass dissolution. Pu oxidation states were analyzed and related to Pu concentrations.
A Large Block Heater Test for High Level Nuclear Waste Management,
Authors: Lin Wunan , Wilder D. G. , Blink J. A. , Blair S. C. , Buscheck T. A. , Glass R. S. , Glassley W. E. , Lee K. , McCright R. D. , Owens M. W. , Roberts J. J. 
Published: April 2011

AbstractThe radioactive decay heat from nuclear waste packages may, depending on the thermal load, create coupled thermal-mechanical-hydrological-chemical (TMHC) processes in the near-field environment of a repository. A group of tests on a large block (LBT) are planned to provide a timely opportunity to test and calibrate some of the TMHC model concepts. The LBT is advantageous for testing and verifying model concepts because the boundary conditions are controlled, and the block can be characterized before and after the experiment. A block of Topopah Spring tuff of about 3 × 3 × 4.5 m was sawed and isolated at Fran Ridge, Nevada Test Site. Small blocks of the rock adjacent to the large block were collected for laboratory testing of some individual thermal-mechanical, hydrological, and chemical processes. A constant load of about 4 MPa will be applied to the top and sides of the large block. The sides will be sealed with moisture and thermal barriers. The large block will be heated by heaters within and guard heaters on the sides so that a dry-out zone and a condensate zone will exist simultaneously. Temperature, moisture content, pore pressure, chemical composition, stress, and displacement will be measured throughout the block during the heating and cool-down phases. The results from the experiments on small blocks and the tests on the large block will provide a better understanding of some concepts of the coupled TMHC processes. The progress of the project is presented in this paper.
A Dynamical Network Model for Percolation Problems in Performance Assessment of Radioactive Waste Management
Authors: Takase Hiroyasu , Inagaki M. , Impey M. D. , Grindrod P. 
Published: April 2011

AbstractA semi-analytical model for percolation problems, called the Dynamical Network Model, is developed. Because of its semi-analytic nature, the model is more efficient than the existing numerical techniques especially for three dimensional problems and, thus, can be used to a wide range of percolation-like problems in performance assessment of radioactive waste disposal.
Devising Scenarios for Future Repository Evolution: A Rigorous Methodology
Authors: Chapman Neil A. , Andersson Johan , Robinson Peter , Skagius Kristina , Wene Clas-Otto , Wiborgh Marie , Wingefors Stig 
Published: April 2011

AbstractThe Swedish Nuclear Power Inspectorate is developing a new methodology for the construction of scenarios for radiological consequence analysis as part of its SITE-94 performance assessment project. SITE-94 involves the incorporation of site specific data from the Äspö site into a performance assessment (PA) of a hypothetical high-level waste repository. This paper describes a systems analysis approach that has been developed based on the concept of organising all the events and processes which need to be taken account of in PA into a ‘process system’ and a much smaller residual group which are used to generate scenarios. The methodology used for developing scenarios, producing calculation cases and addressing the various types of uncertainty involved in PA consequence analysis is described.
Effect of Secondary Phases Formation in the Leaching of UO2 Under Simulated Radiolytic Products
Authors: Díaz-Arocas P. , Quinoñes J. , Maffiotte C. , Serrano J. , Garcia J. , Almazán J. R. , Esteban J. 
Published: April 2011

AbstractThe leaching of the spent fuel matrix (UO2) is function of the radiolytic products formation. The effect of each radioiytic product on the leaching process is not totally understood. In the literature, the influence of H2O2 on the dissolution process is described from the qualitative point of view, and most of the studies were performed for pH values from 8 to 12. In this paper we report on the effect of the H2O2 in the leaching process of UO2 by dissolution experiments at various H2O2 concentrations. Also, it was tested the influence of S/V ratio (surface area exposed to the leaching media) on the UO2 leaching and secondary phases formation. It was identified the formation of secondary phases on the UO2 surface. Solid phases characterization was carried out by x-ray Photoelectron Spectrometry (XPS), x-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) techniques. By XPS studies the secondary phase formed corresponded to a U(VI) phase. By XRD analyses the solid was identified as studtite, UO4 - 4H2O, (card n0 16–206, [I]). A comparison of the U(VI) phases formed in spent fuel and UO, leaching experiments in various media has been carried out.
A Modelling and Experimental Study for Long-Term Prediction of Localised Corrosion in Carbon Steel Overpacks for High-Level Radioactive Waste.
Authors: Hoch A. , Honda A. , Ishikawa H. , Porter F. , Sharland S. , Taniguchi N. 
Published: April 2011

AbstractThis paper describes a joint modelling and experimental study for investigation of pit growth in carbon steel High-Level Radioactive Waste overpacks under consideration in Japan. A mathematical model of the growth of corrosion pits in metals has been developed. This model is implemented in the computer program CAMLE, and includes representation of the chemical, electrochemical and migration processes that control pit-growth rates. Experiments to provide key input data for the model are described, in addition to experiments to measure ‘short-term’ pit growth. Predictions from the model are compared with these data. Overall, the comparisons are encouraging and the model shows good potential as a tool for assessment of the long-term corrosion behaviour of overpacks under repository conditions. Future developments of the model to improve agreement are discussed.
Cathodic Protection for Nuclear Waste Packaging Under Gamma Ray Irradiation by Using TiO2 Coating Combined with Glass Scintillators
Authors: Fujisawa Ryutaro , Tsujikawa Shigeo 
Published: April 2011

AbstractThe photoelectrochemical behaviours of a TiO2 single crystal and TiO2 coating were studied, for the purposes of cathodic protection of stainless steels and Cu via the TiO2 coating combined with glass scintillators under gamma ray irradiation. It was confirmed that a TiO2 coating could protect 304 stainless steel cathodically from crevice corrosion under illumination. A logarithmic relationship between the photopotential of single crystal TiO2(rutile) and light intensity was found, moreover, the photopotential was found to be least noble when wavelength equals 375 nm. Under illumination by gamma rays combined with the glass scintillators, the electrode potential of single crystal TiO2 was found to shift in the less noble direction by about 200 mV. Therefore, the technique of cathodic protection by TiO2 coating is considered to be applicable to protect the packaging metal from corrosion for a long time.
Thorium and Uranium Phosphate Syntheses and Lixiviation Tests for their Use as Hosts for Radwastes
Authors: Genet Michel , Dacheux N. , Merigou C. , Brandel V. 
Published: April 2011

AbstractThorium and uranium phosphates were synthetized via soft chemistry and then calcined at high temperature, respectively up to 850 and 1170°C. Th3(PO4)4 was produced in agreement with published results.while the analog uranium phosphate : U3(PO4)4 was not found. Instead, we found we had made a new mixed valence compound : U(UO2)(PO4)2, for which crystal structure, absorption spectrum in ultraviolet and visible, and X-ray photoelectron spectroscopy were done. All of these experiments confirmed the presence of uranium in both tetravalent and hexavalent states.Lixiviation of thorium phosphate labelled with radioactive isotopes : 227Th and 223Ra allowed us to determine the upper limit of the solubility for this compound = 7.6xl0–11 M and, the percentage of 223Ra released in deionized water (about 5xl0–3%).Similar lixiviation tests on U(UO2)(PO4)2 labelled with 230U (radiochemically produced) gave an uranium solubility value 10 times greater than uranium measured by laser spectrofluorimetry. This discrepancy is attributed to the radiation chemistry inherent in the use of radioactive isotope at high specific activity. The lixiviated uranium fraction from U(UO2)(PO4)2 is seven to eight orders of magnitude higher than for thorium. Unexpected behaviour was observed for uranium solubility which increases by two orders of magnitude after 2000 hours of lixiviation. This phenomenon is not yet understood.
Preparation of Hydrated Glass as a Model of Long-Term Leached Nuclear Waste Glass
Authors: Yamanaka Hiroshi , Nishii Junji , Akai Tomoko , Yamashita Masaru , Wakabayashi Hajimu 
Published: April 2011

AbstractHydrated glass was prepared by the treatment in an autoclave. Specimen in a good state was obtained under unsaturated water vapor pressure conditions. The obtained glass has an silica-rich hydrated layer and proved to be more durable than the original glass. There are some kinds of hydroxyl species in the hydrated glass and there are some patterns in the depth profile of water, indicating that the rate-controlling process is not a simple diffusion and the hydration process is a complicated reaction depending on the conditions. Water in hydrated glass is tightly bonded and a disintegration of hydrated glass in this study occurs at more than 560°C.