bluuebunny/crossref_metadata_2025 huggingface dataset:
Some Evidence of Radiolysis in a Uranium ore Body - Quantification and Interpretation
Authors: Liu Jinsong , Neretnieks Ivars
Published: April 2011

Locally oxidising conditions in the near-field of the Cigar Lake uranium deposit was observed. Ongoing processes of water radiolysis has also been predicted previously by our mass transport model. In the ore there was an enhanced concentration of helium, hydrogen and sulphate. Sulphate is the only oxidising species of substantial amount in the groundwater samples, and is possibly indirectly produced by water radiolysis and oxidation of sulphides. The ongoing oxidant production rate has been calculated by the mass transport model.

In this paper, the issue of water radiolysis is addressed from a more fundamental angle of approach. The maximum oxidant production rate is calculated based on the assumptions of geometric dispersion of the ore constituents, the estimate of the total radiation energy, the fraction of energy deposited into the pore water, and the G-values of water. The results show that only a few percent of the total radiation energy is deposited into the pore water to cause water radiolysis. If the recombination factor projected by other researchers are accounted for, the oxidant production rate thus calculated agrees with the present-day ongoing oxidant production rate predicted by the mass transport model.
Precipitation of Uraninite in Chlorite-Bearing Veins of the Hydrothermal Alteration Zone (Argile De Pile) of the Natural Nuclear Reactor at Bangombé, Republic of Gabon
Authors: Eberly P. , Janeczek J. , Ewing R.
Published: April 2011

This paper describes the mineralogy of a phyllosilicate/uraninite/galena-bearing vein located within the hydrothermal alteration halo associated with the Bangombé reactor. Phyllosilicates within the vein include a trioctahedral Al-Mg-Fe chlorite (ripidolite), Al-rich clay (kaolinite and/or donbassite) and illite. Textural relations obtained by backscattered-electron imaging suggest that ripidolite crystallized first among the sheet silicates. Uraninite is spatially associated with ripidolite and probably precipitated at a later time. While energy-dispersive x-ray analyses suggest that the uranium phase is predominantly uraninite, coffinite or other phases may also be present.
Uranium Redistribution Under Oxidizing Conditions in Oklo Natural Reactor Zone 2, Gabon
Authors: Isobe H. , Ohnuki T. , Murakami T. , Gauthier-Lafaye F.
Published: April 2011

This mineralogical study was completed to elucidate the relationships between uranium distribution and alteration products of the host rock of natural reactor zone 2 at Oklo. The samples used were from the reactor core and reactor zone clays just below the reactor core. Uraninite is preserved without any alteration in the reactor core. Uranium minerals found to be present in the fractures in the reactor zone clays associated with iron-mineral veins, galena and Ti-bearing minerals. Uranium, for which the phases could not be identified, occurs in iron-mineral veins and the iron-mineral rim of pyrite grains in the reactor zone clays. Uranium is not associated with granular iron minerals occurring in the illite matrix of the reactor zone clays. The degree of crystallinity and uranium content of the three iron-bearing alteration products suggest that they formed under different conditions; the granular iron minerals, under alteration conditions where uranium was not mobilized while the iron-mineral veins and the iron-mineral rim of pyrite, under conditions in which uranium is mobilized after the formation of the granular iron minerals.
Measurement of Uranium Series Radionuclides in Rock and Groundwater at the Koongarra ore Deposit, Australia, by Gamma Spectrometry
Authors: Yanase Nobuyuki , Sekine Keiichi
Published: April 2011

Gamma spectrometry without any self-absorption correction was developed to measure low energy gamma rays emitted by uranium and actinium series radionuclides in rock samples and groundwater residues collected at the Koongarra ore deposit, Australia. Thin samples were prepared to minimize the self-absorption by uranium in the samples. The present method gave standard deviations of 0.9 to 18% for the measurements of concentrations of uranium and actinium series radionuclides. The concentrations of238U,230Th and235U measured by gamma spectrometry were compared with those by alpha spectrometry that requires a complicated chemical separation procedure. The results obtained by both methods were in fairly good agreement, and it was found that the gamma spectrometry is applicable to rock and groundwater samples having uranium contents up to 8.1% (103Bq/g) and 3 Bq/1 of238U, respectively. The detection limits were calculated to be of the order of 10−2Bq/g for rock samples and 10−2Bq/1 for groundwater samples. The concentrations of uranium and actinium series radionuclides can be determined precisely in these samples using gamma spectrometry without any self-absorption correction.
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

The 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

We 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

The 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

A 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

Site 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

Curium-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

Diffusion 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

We 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

Drinkis 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

Diffusion 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

The 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

This 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

The 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

The 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

A 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

The 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

The 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

This 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

The 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.
The Interaction of Na-Al-P-Glass (Cs, Sr-Bearing) with Water at Elevated Temperatures (70–250°C)
Authors: Mukhamet-Galeyev Alexander P. , Magazina Larisa O. , Levin Konstantin A. , Samotoin Nikolay D. , Zotov Alexander V. , Omelianenko Boris I.
Published: April 2011

At present Na-Al-P-glass is used in Russia as matrix for high level nuclear waste which include a sufficient portion of 90Sr and 137Cs isotopes. It has been known that this type of glass is characterized by relatively poor hydrothermal stability above 120°C (Krilova et al., 1990 [1], Balukova et al., 1987 [2]). Although careful studies were devoted to the glass, some questions of geochemical behavior of Sr and Cs in the limits of the nearest repository environment have remained undecided. For example, these have been left uncertain: the mechanism of the glass leaching, phenomena limiting the glass dissolution, the detailed composition of newly formed phases, temperature dependence of the glass solubility. The main purpose of the present experimental investigation was to detect factors controlling Sr and Cs concentrations of aquous solutions and to study the possibility of new solid phase formation as a factor slowing down migration of Cs and Sr in water satureted circumstance.
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

Thorium 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

Hydrated 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.
Modeling of Neptunium(V) Sorption Behavior onto Iron-Containing Minerals
Authors: Fujita T. , Tsukamoto M. , Ohe T. , Nakayama S. , Sakamoto Y.
Published: April 2011

Sorption behaviors of neptunium (V) on naturally-occurring magnetite (Fe3O4) and goethite (α-FeOOH) in 0.1M NaN03electrolyte solution under aerobic conditions were interpreted using the surface complexation model (SCM). The surface properties of these materials were experimentally investigated by C02-free potentiometric titration, and SCM parameters for the constant capacitance model, such as protonation/deprotonation constants of the surface hydroxyl group, were determined. The number of negatively charged sorption sites of goethite rapidly increased with the increase of the bulk solution pH compared with that of magnetite and this tendency was similar to the pH dependence of neptunium sorption. This implies that the neptunyl cation, NpO2+, plays a dominant role in possible sorption reactions. Assuming that the dominant surface complex is XO-NpO2, modeling by means of SCM was carried out, and the results were found to agree with experimental data.
Nucleation, Growth and Ostwald Ripening of Cosi2 Precipitates During Co Ion Implantation In Si
Authors: Reiss S. , Ruault M. O. , Clayton J. , Kaitasov O. , Heinig K.-H. , Bernas H.
Published: April 2011

The experimental conditions during the implantation step of Ion Beam Synthesis influence crucially the formation of a buried structure in subsequent annealing steps. Due to of the complexity of the in-beam nucleation and evolution of precipitates of new phases there is still a low level of understanding.
In this paper we present results of direct experimental investigations as well as results of computer simulations of in-beam nucleation and growth. The evolution of an ensemble of C0SÌ2 precipitates is mainly controlled by nucleation and diffusion. The observed decrease of the nucleation rate at high fluences can be explained by the decrease of the supersaturation of implanted atoms due to diffusion towards earlier nucleated precipitates.
Formation of Excess Donors During High-Dose 74Ge+ Ion Implantation
Authors: Xia Z. , Ristolainen E. , Elliman R. , Ronkainen H. , Eränen S. , Kuivalainen P. , Sopanen M. , Tuomi T. , Holloway P.
Published: April 2011

Recently observations that high-dose Ge implantations into Si substrates caused the n-type carrier concentration to increase were attributed to residual structural defects after activation annealing [7,12]. However, co-implantation of an n-type impurity is another possibility. The origin of this excess donor concentration has been studied in this work. The possibilities of residual defects versus implantation of impurities have been investigated using two different implanters and materials analysis. Comparison of data from different implanters showed that the concentration of excess donors was sensitive to the implanter configuration. Furthermore, transmission electron microscopy (TEM), Rutherford backscattering channeling (RBS-C), and spreading resistance profiling (SRP) data showed that the excess donor effect was related to impurities rather than residual defects. Secondary-ion mass spectroscopy (SIMS) and SRP measurements confirmed that impurities such as 75As ions were present after implants. This impurity easily explains the excess donor concentration when 75Ge implants are performed into silicon wafers doped with phosphorous.
Defects Related To Electrical-Leakage In Tmos Structures
Authors: Knoch Lynnita , David Theodore N. , Tam Pak , Yamamoto Taku
Published: April 2011

TMOS devices for power applications use ion-implantation for doped layers. Implant-damage can increase electrical leakage of devices. Transmission electron microscopy was used to study the effect of dose (4E14 - 2E15 cm-2) and energy (20-40 keV) of p+ implants on damage related to leakage in TMOS structures. TEM reveals a high density of boron implant-induced defects such as end-of-range and peak-of-implant damage, boron implant-induced stacking faults and dislocations. End-of-range defects also arise from an arsenic implant, and mask-edge defects arise where arsenic-amorphized Si and crystalline Si meet in the source region. Some defects extend >0.5 μπι into the substrate. The density and the extent of defect penetration decrease with decreasing implant-dose and energy. These data correlate well with the electrical data, which show that Idss leakage decreases with decreasing p+ implant-energy and dose.
Residual Deformations Induced By The Thermal Shock During Pulsed Ion Implantation
Authors: Feugeas Jorge N. , BrÜhl S. P. , Sanchez G. , Kaufmann G. H.
Published: April 2011

Samples of AISI 316 Stainless Steel were nitrogen and argon ion implanted with pulsed beams generated with a Plasma Gun operated in the detonation mode. The residual deformations induced by the beams were studied by double exposure (before and after implantation) holographic interferometry.

The results showed residual deformations corresponding to a concave situation, with the total value depending on the number of single pulses accumulated. A saturation in the deformation is observed when the number of pulses is > 20. A model of the process of pulsed irradiation (based on the strong thermal effect due to the short duration of pulses) and the state of stresses induced in the surface layers is presented.
Sputtering Induced Changes in Defect Morphology and Dopant Diffusion for Si Implanted GaAs: Influence of Ion Energy and Implant Temperature
Authors: Robinson H.G. , Lee C.C. , Haynes T.E. , Allen E.L. , Deal M.D. , Jones K.S.
Published: April 2011

Experimental observations of dopant diffusion and defect formation are reported as a function of ion energy and implant temperature in Si implanted GaAs. In higher energy implants (>100 keV), little or no diffusion occurs, while at energies less than 100 keV, the amount of dopant redistribution is inversely proportional to energy. The extended defect density shows the opposite trend, increasing with increasing ion energy. Similarly, the diffusion of Si during post implant annealing decreases by a factor of 2.5 as the implant temperature increases from -2 to 40°C. In this same temperature range, the maximum depth and density of extrinsic dislocation loops increases by factors of 3 and 4, respectively. Rutherford Backscattering (RBS) channeling measurements indicate that Si implanted GaAs undergoes an amorphous to crystalline transition at Si implant temperatures between -51 and 40°C. A unified explanation of the effects of ion energy and implant temperature on both diffusion and dislocation formation is proposed based on the known differences in sputter yields between low and high energy ions and crystalline and amorphous semiconductors. The model assumes that the sputter yield is enhanced at low implant energies and by amorphization, thus increasing the excess vacancy concentration. Estimates of excess vacancy concentration are obtained by simulations of the diffusion profiles and are quantitatively consistent with a realistic sputter yield enhancement. Removal of the vacancy rich surface by etching prior to annealing completely suppresses the Si diffusion and increases the dislocation density, lending further experimental support to the model.
Depth-Dependent Hardness Improvements in Ion Irradiated Polystyrene
Authors: Rao Gopal R. , Riester Laura , Lee Eal H.
Published: April 2011

Polystyrene (PS) was irradiated with 2 MeV He+ ions to a fluence of 3.3×1019 ions/m2. A cross-section of the irradiated layer was subjected to hardness measurements across the section using a nanoindentation technique. Results showed that hardness increased as a function of irradiation depth and showed a maximum value of 12 GPa at a depth of approximately 6.5 μπι, for a total ion penetration range of 9 μιη, as compared to a hardness of 0.45 GPa for unirradiated PS. The hardness variation with depth followed the trend for Linear Energy Transfer (LET) for ionization from the energetic ions to substrate atoms. This investigation showed for the first time how hardness varies as a function of depth for ion-irradiated polymers; this variation approximately follows the ionization LET profile, suggesting that cross-linking in the polymers could be proportional to ionization.
Observation of Semiconductor Superstructures With Backscattered Electrons in a Scanning Electron Microscope
Authors: Bosacchi A. , Franchi S. , Govoni D. , Mattei G. , Merli P.G. , Migliori A. , Nacucchi M.
Published: April 2011

Observations of semiconductor superstructures with backscattered electrons in a scanning electron microscope have been used to revisit the concept of resolution of the backscattering imaging mode. It will be shown that the generation volume doesn't represent in itself a limit to the resolution, which depends only on the beam size and the signal to noise ratio.
Structural Differences Between Cvd And Thermally Grown Amorphous SiO2
Authors: Makabe M. , Hirose K. , Ishikawa H. , Ono H. , Ishitani A. , Mizuki J.
Published: April 2011

The structure and density of amorphous S1O2 films grown by chemical vapor deposition (CVD) or thermal oxidation are studied by Fourier-transform infrared (FT-IR) absorption, neutron diffraction, and Rutherford backscattering (RBS) measurements. CVD oxides, formed in an atmospheric-pressure CVD reactor with a SiH4-O2 gas mixture at 400 °C, are compared with thermal oxides, grown at 980 °C in H2-O2 atmosphere. The average Si-O-Si bond angle deduced from the stretching frequency of FT-IR is found to be smaller in CVD oxides than in thermal oxides, and the density revealed by RBS measurements is found to be a little lower in CVD oxides than in thermal oxides. These differences are explained by the medium-range structural disorder revealed by FT-IR measurements as well as by neutron diffraction measurements. The medium-range structural disorder in CVD oxides is responsible for large silanol content in the oxides and is the origin in difference between CVD and thermal oxides.
Backside Sims Study Of Ge/Pd Non-Alloyed Ohmic Contacts On InGaAs
Authors: Schwarz S.A. , Pahnstrom C.J. , Bhat R. , Koza M. , Wang L.C. , Park M.H.
Published: April 2011

Backside secondary ion mass spectrometry (SIMS) is employed to examine the Ge/Pd non-alloyed ohmic contact on InGaAs. 130 nm Ge/ 50 nm Pd contacts were deposited on an InP/InGaAs marker layer structure. The contacts were annealed for various times at 200°C and 325°C. Samples were mechanically and chemically thinned to facilitate sputter profiling from the backside, thereby avoiding problems such as roughening or non-uniformity of the metallic layers. Subsequent to depth profiling, additional anneals were performed on the thinned samples, and the samples were reexamined. Extensive reaction of Pd with InGaAs is observed on deposition. Little additional reaction occurs at 200°C. At 325°C, Pd is reclaimed from the reacted surface region, forming PdGe with some excess Ge at the interface. In-diffiision of Pd and Ge into InGaAs is observed at longer annealing times. The results are contrasted with prior studies on GaAs, InP, and InGaAs.
Quantifying The Effects Of Amorphous Layers on Image Contrast Using Energy Filtered Transmission Electron Microscopy
Authors: Boothroyd C. B. , Dunin-borkowski R. E. , Stobbs W. M. , Humphreys C. J.
Published: April 2011

High resolution images of a block oxide, (Nb205)çi(W03)8, with and without a superposed carbon film are compared both energy filtered and including the inelastic scattering. The differences between the images are quantified on an absolute intensity scale and possible origins of the differences in atomic level contrast are assessed using multislice simulations.
Modelling of Multi-Ion-Beam Reactive Cosputtering for Metal Oxide Thin Films
Authors: Xiao D. Q. , Zhu J. G. , Qian Z. H. , Peng W. B. , Wei L. F. , Li Z. S.
Published: April 2011

Very recently a new technique named multi-ion-bram reactive cosputtering(MIBRECS) was developed for preparing multi-component metal oxide thin films. Epitaxial or highly oriented (Pb,La) TiO3 thin films sputtered from pure metals of lead, titanium and lathanium were deposited by using this technique. In order to consummate the technique and to study the mechanism of reactive cosputtering, a general model of multi-ion-beam reactive cosputter-ing was proposed for the first time based on the well-known gas kinetics under stable sputtering circumstances, and a computer numerical simulation of the model was carried out with the parameters adopted in our experiments. The relationships among the sputtering ratioes of the targets, and the coverage ratioes of simple substances and oxides of the target metals on substrate surface with the total reactive gas flux and the densities of the sputtering ion beam were obtained respectively, and the hysteresis effect of the characteristic of reactive sputtering and the interactions during multi-ion-beam reactive cosputtering processes were also obtained. The numerical simulation results are at least qualitively in agreement with the experiments.
Copper Metallization of Polyimide Film by Excimer Laser Irradiation and Electrodeposition
Authors: Hohman James L. , Keating Kenneth B. , Kelley Michael J.
Published: April 2011

Severe excimer laser irradiation is reported to impart electrical conductivity to Kapton* polymide films. We find that a proper choice of pretreatment and irradiation practice reduces the required dose markedly. Such films have sufficient conductivity to permit direct, good-quality, adherent copper electroplating.H.M.Phillips, D.L.Callahan, R.Sauerbrey, G.Szabo and Z.Bor; Appl.Phys.Lett.58, 2761 (1991).
Laser-Ablated Particles From Porous Silicon
Authors: Nonaka Hidehiko , Sekine Shigeyuki
Published: April 2011

In order to search for the possibility to synthesize materials with new functions by laser deposition using source materials consisting of characterized microstructures, the porous silicon was ablated in ultrahigh vacuum with ultraviolet lasers of fluence as low as a few Jem”2. The ablated particles were analyzed by the time of flight method and the main species detected were atoms and small molecules such as Si, SÍ2, and SiO. The kinetics of the laser ablation of porous silicon in comparison with crystal silicon was also studied.
Laser-Modified Chemical Beam Epitaxy of InGaAs/GaAs Multiple Quantum Wells Using Tris-Dimethylaminoarsenic
Authors: Dong H.K. , Li N.Y. , Tu C.W.
Published: April 2011

We report for the first time laser-modified chemical beam epitaxy (CBE) of InGaAs/GaAs multiple quantum well (MQW) structures using trimethylindium (TMIn), triethylgallium (TEGa), and tris-dimethylaminoarsenic (TDMAAs), a safer alternative to arsine. X-ray rocking curve (XRC) and low-temperature photoluminescence (PL) measurements were used to characterize the pseudomorphic strained quantum well structures. As determined by the X-ray simulation, laser irradiation during the InGaAs well growth was found to enhance the InGaAs growth rate and reduce the indium concentration in the substrate temperature range studied, 440-S00°C, where good interfaces can be achieved. We attribute these changes to laser-enhanced decomposition of TEGa and laser-enhanced desorption of TDMAAs. With laser irradiation, lateral variation of PL exciton peaks was observed, and the PL peaks became narrower.
Uniform And Large Area Deposition Of Diamond-Like Carbon Using Rf Source Ion Beam
Authors: Wu Richard L.C. , Lanter William , Miyoshi K. , Heidger S.L. , Bletzinger P. , Garscadden A.
Published: April 2011

We have designed and constructed a large area ion beam apparatus to deposit DLC films onto 1000 cm2surfaces with various geometries. The use of an efficient RF excited ion gun (13.56 MHz, 1 kW power, 50-3000 eV ion energy) with a diameter of 20 cm, enables us to generate various hydrocarbon ions with high ion beam currents, varying ionic species and less maintenance. The use of a four axis (Χ-ϒ-Θϒ-ΘZ) substrate scanner with computer control can produce uniform DLC films on large areas and curved surfaces. The effects of RF power, ion energy, gaseous composition, and total pressure on the properties of DLC have been systematically investigated.
Studies of Cn1 Films Deposited by Ion-Beam-Assisted Laser Ablation of Graphite
Authors: Ren Zhong-Min , Du Yuan-Cheng , Xiong Xia-Xing , Wu Jia-Da , Ying Zhi-Feng , Qiu Yuan-Xun , Li Fu-Ming
Published: April 2011

CN1 thin films have been synthesized by ion-beam-assisted laser ablation of graphite. Films with N-concentration of 45% are obtained, indicated by high energy backseattering spectrum (HEBS). Raman and X-ray photoelectron spectroscopy (XPS) data confirm the existence of carbon-nitrogen bonds. Polycrystallites beta-CjNi structure has been detected in the amorphous matrix of the films, as indicated by transmission electron microscopy (TEM) and electron diffraction. Qualitative tests indicate that the films are relatively hard and adhesive.
Microraman Study of Laser Ablated Gaas
Authors: García C. , Jiménez J. , Prieto A.C. , Ramos J. , Sanz L.F.
Published: April 2011

Morphologic and structural changes induced by UV pulsed laser beams on GaAs are studied by means of surface inspection (optical interferometry) and MicroRaman spectroscopy. Crystal order and chemical composition (dopant distribution ) are shown to be changed by the ablation.
Some Insights Into the Process of E-beam Generation of Metal Nanoparticles From Binary Metal Hydride and Azide Precursors
Authors: Herley Patrick J. , Jones William
Published: April 2011

Exposure of micron-sized particles of inorganic metal hydrides and azides to an intense electron beam within a transmission electron microscope results in melting followed by accelerated decomposition. The energy density localized in the specimen is considerable - arguably from one of the most intense energy deposition sources available. The induced effects have been evaluated using electron beam theory and it is concluded that, to a first approximation, the phenomena are attributable to extremely rapid heating. Criteria for the use of this technique to other possible systems are identified and future experiments applying this unique technique to other materials systems are proposed.