bluuebunny/crossref_metadata_2025 huggingface dataset:
Study of Processing Hllw by Super High Temperature Method. Part II*. Reducing Reactions and Formation of Complex Oxides in the Simplified Hllw
Authors: Uno Masayosi , Kadotani Youji , Miyake Chie , Horie Misato
Published: April 2011

The reducing reactions of platinum metal oxides and the formation of the complex oxides were studied to estimate the process at high temperatures. Heat treatment of Re207 with TiN causes reduction up to the sublimation point of Re207 and exhibits the highest value of the recovery among the reducing agents used in the present study. Reducing reactions of the platinum metal oxides with the reducing agents lower the melting temperature. The simplified complex oxides contain the complex oxides of the representative elements of FP and the metallic elements of the reducing agents, which contribute to a decrease of melting temperature, neodymium zirconium oxides and neodymium barium oxide which may transform to the other phases during heating. Uranium may dissolve in the phases in which uranium is identified by EPMA but cannot detected by X-ray diffraction.
Behaviour of Iodine-129 in Rice Paddy Fields
Authors: Uchida Shigeo , Muramatsu Yasuyuki
Published: April 2011

Transfer factors of iodine from soil to rice were obtained by laboratory experiments using125I tracer. Two typical soil types in Japan, Andosol and Gray lowland soil, were used. The transfer factor (TF) is defined as ’concentration of the nuclide in a plant organ at harvest’ divided by ’concentration of the nuclide in dry soil’. The TFs for brown (hulled) rice were 0.006 for Andosol and 0.002 for Gray lowland soil. The TFs for different organs of rice plants decreased in the order of blade > stem > rachis > unhulled rice >> brown rice.

The concentration of iodine in soil solution under flooded conditions varied with time during cultivation. The iodine concentration in rice plants seemed to be influenced by the soil solution.

The effect of removal of 1–129 from paddy fields by harvesting rice plants was also modelled. Even assuming continuous deposition of 1–129 onto the field, annual harvesting of the blades and stems of rice plants could effectively reduce the amount of the nuclide in the root zone.
Experimental Determination of Chlorite Dissolution Rates
Authors: Rochelle Christopher A. , Bateman Keith , MacGregor Robert , Pearce Jonathan M. , Savage David , Wetton Paul D.
Published: April 2011

Current concepts of the geological disposal of low- and intermediate-level radioactive wastes in the UK envisage the construction of a mined facility (incorporating cementitious engineered barriers) in chlorite-bearing rocks. To model accurately the fluid-rock reactions within the ‘disturbed zone’ surrounding a repository requires functions that describe mineral dissolution kinetics under pH conditions that vary from near neutral to highly alkaline.

Therefore, an experimental study to determine the dissolution rates of Fe-rich chlorite has been undertaken as part of the Nirex Safety Assessment Research Programme. Four experiments have been carried out at 25 °C and four at 70 °C, both sets using a range of NaCl/NaOH solutions of differing pH (of nominal pH 9.0,10.3, 11.6 and 13.0 [at 25 °C]).

Dissolution rates have been calculated and were found to increase with increasing pH and temperature. However, increased pH resulted in non-stoichiometric dissolution possibly due to preferential dissolution of part of the chlorite structure relative to another, or reprecipitation of some elements as thin hydroxide or oxyhydroxide surface coatings on the chlorite.

These results also show that chlorite dissolution is appreciably slower than that of albite and quartz at both 25 and 70 °C, but slightly faster than that of muscovite at 70 °C.
Coupled Chemical and Diffusion Model for Compacted Bentonite
Authors: Olin M. , Lehikoinen J. , Muurinen A.
Published: April 2011

A chemical equilibrium model has been developed for ion-exchange and to a limited extent for other reactions, such as precipitation or dissolution of calcite or gypsum, in compacted bentonite water systems. The model was successfully applied to some bentonite experiments, especially as far as monovalent ions were concerned. The fitted log-binding constants for the exchange of sodium for potassium, magnesium, and calcium were 0.27, 1.50, and 2.10, respectively.
In addition, a coupled chemical and diffusion model has been developed to take account of diffusion in pore water, surface diffusion and ion-exchange. The model was applied to the same experiments as the chemical equilibrium model, and its validation was found pardy successful. The above values for binding constants were used also in the coupled model. The apparent (both for anions and cations) and surface diffusion (only for cations) constants yielding the best agreement between calculated and experimental data were 3.0×10-11 m2/s and 6.0×10-12m2/s, respectively. These values are questionable, however, as experimental results good enough for fitting are currently not available.
Estimation of Effective Diffusivity in Compacted Ben Tonite
Authors: Kato H. , Muroi M. , Yamada N. , Ishida H. , Sato H.
Published: April 2011

Effective diffusivities of radioactive nuclides in compacted bentonite were calculated theoretically by using an electric double layer theory. Comparison between calculated diffusivities and measured ones show good agreements.

The effective diffusivity is dominated by pore structure and pore diffusivity Dp. The pore structure can be characterized by effective porosity ε eff, constrictivity δ, and tortuosity Γ. The δ was assumed to be unity. The ε eff and the Γ were determined experimentally. The Dp was estimated by means of the electric double layer theory. In the estimation, smectite interlayer was assumed the space between parallel plane sheets of smectite crystal lattice.

Diffusion experiments were carried out by using Cs+ for monovalent cation, C1- and Tc04- for monovalent anion, and tritiated water for neutral molecule. The measured and calculated effective diffusivities in different densities showed the same tendency of cation > neutral > anion. The dry density of bentonite became higher, the discrepancy between the estimated and the measured diffusivities became larger. The calculation was limited by the applicability of the electric double layer theory in the near surface region of smectite.
Radiation Resistance of the Natural Microbial Population in Buffer Materials
Authors: Stroes-Gascoyne S. , Lucht L. M. , Borsa J. , Delaney T. L. , Haveman S. A. , Hamon C. J.
Published: April 2011

The radiation sensitivity of naturally occurring microorganisms in buffer materials vas investigated as veil as the sensitivity ofBacillus subtilisspores andAcinetobacter radioresistensin a buffer matrix. The D10values obtained in our radiation experiments varied from 0.34 to 1.68 kGy and it vas calculated that the surface of a nuclear fuel vaste container vould be sterilized in 9 to 33 d after emplacement, depending on the type of container, and the initial bioburden. This suggests that formation of biofilms and microbially influenced corrosion vould not be of concern for some time after emplacement. The results also indicated that sterilization throughout a 25 cm thick buffer layer is unlikely and that repopulation of the container surface after some time is a possibility, depending on the mobility of microbes in compacted buffer material.
Numerical Relationship between Surface Deformation and a Change of Groundwater Table Before and after an Earthquake
Authors: AKAO Yoshihiko
Published: April 2011

The purpose of this study is to estimate the effect of earthquakes upon a groundwater flow around a repositories for high-level radioactive wastes. Estimation of a groundwater flow change before and after an earthquake or a volcanic eruption is one of the issues for a long-term safety assessment of the repositories. However, almost any systematic investigation about the causality between a groundwater flow change and an earthquake or an eruption was not found, and as well no estimation formula has been published. We succeeded to obtain a primitive relationship between a groundwater change and an earthquake in this study.

Our study consists of three stages. First, several survey reports which describe field observation results of groundwater anomalies caused by earthquakes or eruptions have been collected. The necessary data have been read from the literature and systematically arranged. Second, source mechanisms of the corresponding earthquakes were inspected and static displacements at the well positions were calculated by the dislocation theory in the seismology. Third, parametric studies among the parameters of groundwater anomalies and earthquakes were carried out to find a numerical relationship between a couple of them. Then, a preliminary relationship between water table change in a well and static displacement at the well position was found.

We can conclude that temporary change of water table seems to depend on the norm of displacement vector. In this relationship, the maximum value of water table change would be approximately one hundred times of the displacement.
Near-Field Transport of 129I from a Point Source in an In-Room Disposal Vault
Authors: Kolář Miroslav , Leneveu Dennis M. , Johnson Lawrence H.
Published: April 2011

A very small number of disposal containers of heat generating nuclear waste may have initial manufacturing defects that would lead to pin-hole type failures at the time of or shortly after emplacement. For sufficiently long-lived containers, only the the initial defects need be considered in modelling of release rates from the disposal vault. Two approaches to modelling of near-field mass transport from a single point source within a disposal room have been compared: the finite-element code MOTIF (A Model Of Transport In Fractured/porous media) and a boundary integral method (BIM). These two approaches were found to give identical results for a simplified model of the disposal room without groundwater flow. MOTIF has been then used to study the effects of groundwater flow on the mass transport out of the emplacement room.
Examination and Testing of an Active Glass Sample Produced by Cogema
Authors: Cheron P. , Chevalier Ph. , Do Quang R. , Tanguy G. , Sourrouille M. , Woignier S. , Senoo M. , Banba T. , Kuramoto K. , Yamaguchi T. , Shimizu K. , Fillet C. , Jacquet-Francillon N. , Godard J. , Dussossoy J. L. , Pacaud F. , Charbonnel J. G.
Published: April 2011

This paper presents the results of analyses and measurements performed on an active glass sample taken from the French vitrification facility R7.
Corrosion Behavior of Spent MTR Fuel Elements in a Drowned Salt Mine Repository
Authors: Brodda Bert-G. , Fachinger J.
Published: April 2011

Spent MTR fuel from German Material Test Reactors will not be reprocessed, but stored in a final salt repository in the deep geologic underground. Fuel elements will be placed in POLLUX containers, which are assumed to resist the corrosive attack of an accidentally formed concentrated salt brine for about 500 years. After a container failure the brine would contact the fuel element, corrode the aluminum plating and possibly leach radionuclides from the fuel.

A source term for the calculation of radionuclide mobilization results from the investigation of the behavior of MTR fuel in this scenario, which has to be considered for the long- term safety analysis of a deep mined rock salt repository.

Experiments with the different plating materials show that the considered aluminum alloys will not resist the corrosive attack of a brine solution, especially in the presence of iron, under the conditions in a drowned salt mine repository. Although differences in the corrosion rates of about two orders of magnitude were observed when applying different parameter sets, the deterioration must be considered to be almost instantaneous in geological terms.

Radionuclides are mobilized from irradiated MTR fuel, when the “meat” of the fuel element becomes accessible to the brine solution. It seems, however, that the radionuclides are effectively trapped by the aluminum hydroxide formed, as the activity concentrations in the brine solution soon reach a constant level with the progressing corrosion of the cladding aluminum. In the presence of iron a more significant initial release was observed, but also in this case an equilibrium activity seems to be reached as a consequence of radionuclide trapping.
The Assessment of the Long-Term Evolution of the Spent Nuclear Fuel Matrix by Kinetic, Thermodynamic and Spectroscopic Studies of Uranium Minerals.
Authors: Bruno Jordi , Casas I. , Cera E , Ewing R. C. , Finch R. J. , Werme L. O.
Published: April 2011

The long term behaviour of spent nuclear fuel is discussed in the light of recent thermodynamic and kinetic data on mineralogical analogues related to the key phases in the oxidative alteration of uraninite. The implications for the safety assessment of a repository of the established oxidative alteration sequence of the spent fuel matrix are illustrated with Pagoda calculations. The application to the kinetic and thermodynamic data to source term calculations indicates that the appearance and duration of the U(VI) oxyhydroxide transient is critical for the stability of the fuel matrix.
Prediction of Unknown Uranyl Oxide Hydrate Structure Types: Comparison of Calculated and Measured XRD Powder Patterns
Authors: Finch R. J. , Hawthorne F. C. , Ewing R. C.
Published: April 2011

The accurate identification of uranium-bearing corrosion products from spent fuel leaching studies is often difficult because the XRD powder patterns for many U(VI) phases are closely similar. Standard pattern-matching techniques commonly used for phase identification (e.g., JCPDS) make confident phase identification difficult and can oversimplify complex mixtures of UOHs. Refinement methods that fit the full XRD powder pattern, such as Rietveld, may be the only methods for accurate UOH identification, especially for data from sample mixtures. Rietveld refinement of XRD powder data for uranium oxides can be accomplished for phases whose structures are well defined. Unfortunately, many of the uranyl oxide hydrates are still ill-defined, both structurally and compositionally. The uranyl oxide hydrates have large unit cells and relatively low symmetries, as well as close structural similarities, all of which complicates the simultaneous refinement of mixed UOH phases. Modeling peak shape profiles can also hamper refinements of mixed-UOH samples due to extreme peak overlap. Because of these difficulties, Rietveld structuredeterminationfor UOHs from sample mixtures remains intractable, although structure determination may be possible for fine-grained, single-phase samples. Nonetheless, Rietveld refinement is the most promising method for accurately identifying the component phases in a mixture, but the unknown UOH structures must be determined before this technique can be applied successfully.
Impact of Thermal Loading on Waste Package Material Performance
Authors: Stahl D. , McCoy J. K. , McCright R. D.
Published: April 2011

This report focuses on the prediction of materials performance for the carbon steel corrosion-allowance container as a function of thermal loading for the potential repository at Yucca Mountain. Low, intermediate and high thermal loads were evaluated as to their performance given assumptions regarding the temperature and humidity changes with time and the resultant depth of corrosion penetration. The reference case involved a kinetic relation for corrosion that was utilized in a sensitivity analysis to examine the impacts of time exponent, pitting, and microbiologically-influenced corrosion. As a result of this study, the high thermal load appears to offer the best corrosion performance. However, other factors must be considered in making the final thermal loading decision.
Stochastic Modeling of the Influence of Environment on Pitting Corrosion Damage of Radioactive-Waste Containers
Authors: Henshall Gregory A.
Published: April 2011

A physically-based, phenomenological stochastic model for pit initiation and growth is presented as a potential tool for predicting the degradation of high-level radioactive-waste containers by aqueous pitting corrosion. Included in the model are simple phenomenological equations describing the dependence of the controlling stochastic parameters on the applied (or corrosion) potential, chloride ion concentration, and absolute temperature. Results from this model are presented that demonstrate its ability to simulate several important environmental effects on pitting.
Durability of High-Level Waste Glass in Flowing Groundwater Under Gamma-Irradiation
Authors: Kamizono Hiroshi , Hashimoto Masa-Aki , Tamura Yukito , Sagawa Tamio , Matsumoto Sei-Ichiro
Published: April 2011

Durability of simulated high-level waste glass in continuously-flowing J-13 tuff groundwater has been examined at 90°C under gamma-irradiation. The results obtained are compared with those without gamma-irradiation. The effects of groundwater radiolysis on the glass durability are discussed based on the Eh-pH excursion obtained in the present system. It is found that the groundwater tends to be reduced under gamma-irradiat ion, however, this may not influence the solubility of multivalent cations leached from the glass.
Crichtonite Structure Type (Am21O38 and A2M19O36) as a Host Phase in Crystalline Waste Form Ceramics
Authors: Gong W. L. , Ewing R. C. , Wang L. M. , Xie H. S.
Published: April 2011

Previous studies of ceramic crystalline waste forms, e.g. Synroc, tailored ceramics, and supercalcine, have concentrated on phases which are major constituents in the formulations: zirconolite, pyrochlore, hollandite, perovskite and zircon. These phases usually occur as members of multi-phase assemblages which are required for the incorporation of the wide variety of radionuclide elements present in the waste and the non-radioactive components added during reprocessing and pretreatment. The crichtonite structure (AM21O38 and A2M19O36), based on crystallo-chemical considerations and natural compositional analogues, may effectively incorporate both fission products and actinides. The naturally occurring crichtonite structure types include Sr (crichtonite), Ca and REE (loveringite), Na (landauite), REE and U (davidite), K (mathiasite), Ba (lindsleyite), and Pb (senaite), which are classified based on the dominant, large cations occupying the A-site. The crystal structure contains three types of sites of distinct size, from very large, M0, intermediate (M1, M3, M4, and M5), to small (M2). Numerous coupled substitutions within these cation sites allow for charge balance. Synthesis experiments were completed on the Ba-, Sr-, Ca-, and K-member compositions at 3 GPa and 1,150 °C. Low pressure synthesis should be possible, as natural minerals mostly occur in low-P systems. Reaction products were characterized by powder x-ray diffraction, scanning electron microscopy and electron microprobe analysis. In addition to the crichtonite phases, rutile, spinel, perovskite and armalcolite were identified as well. The Crichtonite structure type is estimated to accommodate waste loading of up to 30 wt. % PW-4B waste.
Comparison of Ceramic Waste forms Produced by hot Uniaxial Pressing and by Cold Pressing and Sintering
Authors: Oversby V. M. , Vance E.R.
Published: April 2011

Synroc C waste form specimens prepared using the Australian-developed technology are uniaxially pressed in stainless steel bellows at 1200°C and 20MPa. This produces a material with high chemical and physical durability and with the radioactivity enclosed inside both the waste form and the bellows. An alternative method of producing the ceramic product is to use cold pressing of pellets followed by reactive sintering to provide densification and mineralization. Depending on the scale of waste form preparation required and on the activity level and nature of the waste streams, the cold press and sinter method may have advantages. To evaluate the effects of production method on waste form characteristics, especially resistance to dissolution or leaching of waste elements, we have prepared two simulated waste samples for evaluation. Both samples were prepared from liquid precursor materials (alkoxides, nitrates, and colloidal silica) and then doped with waste elements. The precursor material in each case corresponded to a basic phase assemblage of 60% zirconolite, 15% nepheline, 10% spinel, 10% perovskite, and 5% rutile. One sample was doped with 25% by weight of U; the other with 10% by weight each of U and Gd. Each sample was calcined at 750°C for 1 hr. in a 3.5% H2 in N2 atmosphere. Then one portion of each sample was hot pressed at temperatures ranging from 1120 to 1250°C and 20MPa pressure in steel bellows. A separate portion of each sample was formed into pellets, cold pressed, and sintered in various atmospheres at 1200°C to produce final products about 2/3 cm in diameter. Samples were then examined to determine density of the product, grain sizes of the phases, phase assemblage, and the location of the U and Gd in the final phases. Density data indicate that sintering gives good results provided that the samples are held at 200°C for long enough to allow trapped gases to escape.
Synthetic Melted Rock-Type Wasteforms
Authors: Sobolev Igor A , Stefanovsky Sergey V , Lifanov Fyodor A
Published: April 2011

Glass-ceramic materials based on sphene, pyroxenes, apatite as well as various SYNROC formulations have been produced through melting in a laboratory electrically-heated furnace and inductive-heated melter (“cold crucible”). Materials prepared were investigated by X-ray diffraction analysis, electron-probe microanalysis, infra-red and EPR spectroscopies. Basic properties such as leach rates of radionuclides, density and compressive strength have been determined. Melted SYNROC-B and C phase compositions produced by induction melting are similar to hot-pressed SYNROC.
pH Dependence of the Aqueous Dissolution Rates of Perovskite and Zirconolite at 90°C
Authors: McGlinn Peter J , Hart K. P. , Loi E. H. , Vance E. R.
Published: April 2011

Perovskite and zirconolite are two of the major phases of the Synroc titanate mineral assemblage. Their aqueous durability under a range of pH conditions at 90°C has been examined. Solution analysis, electron microscopy and X-ray diffraction have been used to investigate the dissolution behaviour of these phases, and a perovskite phase doped with Nd, Sr and Al, using buffered solutions at pH levels of 2.1, 3.7, 6.1, 7.9 and 12.9. After 43 days of leaching, Ca and Ti extractions from perovskite and zirconolite show only a weak pH-dependence.

SEM investigation of the samples leached at pH 2.1, 6.1 and 12.9 showed that a titanaceous surface layer formed on the perovskite specimens. XRD analysis of the perovskite samples showed that anatase formed on the leached surface at acidic and neutral pHs, but not under alkaline conditions, and that minor amounts of rutile also formed. In the leached perovskite specimens doped with Nd, Sr and Al, no rutile was found by XRD and anatase was only detected in the sample leached at pH 2.1. There were no detectable changes in the leached zirconolite samples examined by SEM and XRD.
Surface Alteration of Sintered Product of Strontium Aluminum Silicate Under Hydrothermal Conditions
Authors: Mimura H. , Koyama A. , Akiba K.
Published: April 2011

The surface alteration of strontium aluminum silicate has been studied under hydrothermal conditions in connection with the leachability of Sr from solidified radioactive wastes. Samples exposed to a 3 M NaCl solution at 300°C produced a precipitated layer of analcime (NaAISi2O6) with high crystallinity. The normalized leach rates for Sr in 3 M NaCl and 3 M KC1 solutions were found to be less than 10-3 g/cm2.d, yielding high resistance to leaching in these solutions.

On exposure to the CaCl2 solution at 300°C, anorthite (CaAl2Si2O8) was formed on the surface, indicating the replacement of Sr with Ca through isomorphous substitution. In the case of MgCl2 solution, a thick precipitated layer of clinochlore (Mg5Al(Si3Al)O10(OH)8) built up on the outermost surface. This layer serves to depress the migration of Sr, resulting in the deposition of SrCl2 salts in the altered layer.
Macro and Micro Observations on Mortar Alteration Mechanism Under the Various Solution Conditions
Authors: Fujiwara A. , Tashiro S. , Takemura T. , Sakogaichi K. , Yokomoto S. , Katsuyama K.
Published: April 2011

Accelerated aging tests have been conducted to evaluate the long-term durability of cementitious material against aggressive ions. In tests, cementitious specimens were immersed in the solutions containing concentrated aggressive ions at high temperature and it promoted diffusion of the ions in the specimen. This method would be suitable for the evaluation on the aging as the alteration of the specimen would be expected to resemble the natural behavior. This paper presents a classification of alteration mechanism in the immersion tests using MgCl2 and Na2SO4 solution. This classification was done by relating the changes of compressive strength to microscopic and mineralogical changes.
Influence of Aggressive Liquid Environment on the Physico-Chemical and Mechanical Characteristics of Mortar-Radwaste Mixture Form
Authors: Perić Aleksandar D , Plećaš Ilija B , Pavlović Radojko S
Published: April 2011

Mortar was used as a matrix material in an immobilization process of radioactive waste material, 137CsCl solution, where the final product had a water-to-cement ratio of 0.36. Solidified orthocylinder shaped samples, H=4.5 cm, with the exposed surface area completely open to contact leachant medium, were used in prospecting physico-chemical and mechanical characteristics of mortar-radwaste mixture forms. After curing period of 28 days in an atmosphere of defined parameters, samples were introduced to leaching in the specific leachant media. Leachants were chosen up to their aggressive influence on matrix material deterioration and decomposition: distilled water, chloride and sulphate solutions. Experiments were performed for 730 days and the 137Cs cumulative leached fraction for each leachant was calculated. Leach-rate steady-state values were obtained after approximately 290 days. The same trend in obtaining saturation value was noticed in an investigations of pH value and Ca2+ concentration in the three groups of leachants, due to a Ca2+ depletion from the matrix structure. Mortar-radwaste mixture samples were withdrawn from the leaching experiments and investigated on their mechanical strength. Mechanical strength characteristics adopted a decreasing trend for the samples treated in leachants longer than 100 days, which continued in the two years period of experimental duration.
The Use of Surface Analytical Techniques to Measure the Loadings of Uranium and Plutonium Sorbed Simultaneously from Solution onto Rocks
Authors: Berry J A , Bishop H E , Cowper M M , Fozard P R , McMillan J W
Published: April 2011

Small polished blocks of granite, diorite and dolerite were immersed in solutions containing uranium and plutonium at equal initial concentration. The samples were analysed by the advanced surface analytical techniques of secondary ion mass spectrometry (SIMS) and nuclear microprobe analysis. The results show that both actinides sorb onto the same minerals in the three rocks. However, SIMS data show that significantly more uranium was sorbed than plutonium.
Influence of Microbial Activity on Technetium Behaviour in Soil Under Waterlogged Condition
Authors: Tagami K. , Uchida S.
Published: April 2011

The behaviour of Tc in soil depends upon its chemical forms. Under aerobic conditions, Tc is present as pertechnetate Tc+7(TcO4–), which has a high geochemical mobility and bioavailability. However, the form changes through a combination of factors such as redox conditions and microbial activity in soils. The anaerobic condition can be supplied in waterlogged rice paddy soil, which is common to Japan and other Southeast Asian countries.

In this study, we focused on the influence of microbial activity on Tc behaviour in soil under the waterlogged condition. The microbial activity is expected to be controlled by addition of glucose and the activity causes a change in the soil redox condition. Air-dried soil with increasing glucose contents and sterile soil were used to compare the effect of microbial activity. The soils were waterlogged with99Tc solution. Although the concentrations of99Tc in the surface and bottom solutions of air-dried soils decreased over time with increasing glucose concentration, those of sterile soils were almost constant during the experiment. From these results, it was assumed that the activity of microorganisms influenced Tc adsorption onto the soil.
Sorption Behavior of Uranium(VI) on a Biotite Mineral
Authors: Idemitsu K. , Obata K. , Furuya H. , Inagaki Y.
Published: April 2011

Biotite has the most important role for the sorption of radionuclides in granitic rocks. Experiments on the sorption of uranium (VI) on biotite were conducted to understand the fundamental controls on uranium sorption on biotite mineral, including the effects of pH and uranium concentration in solution. Biotite powder (mesh 32 – 60) were washed with 1N HC1 for a week and were rinsed twice with deionized water for a week. This HC1 treatment was necessary to avoid the effects by other minerals. The agreement between surface adsorption coefficient, Ka, of both biotites with and without HC1 treatment was within one order of magnitude. The peak Ka value was in the range of 0.1 to 0.01 cm3/cm2 around pH 6. A comparison of aqueous uranium speciations and sorption results indicates that neutral uranyl hydroxide could be an important species sorbed on the biotite.

Sequential desorption experiments with KC1 and HC1 solutions were also carried out after sorption experiments to investigate sorption forms of uranium. Approximately 20 % of uranium in solution were sorbed on the biotite as an exchangeable ion. The fraction of exchangeable uranium had a little dependence on pH. The other uranium could not be extracted even by 6N HC1 solution. It is possible that most of the uranium could be precipitated as U(IV) via Fe(II) reduction on the biotite surface.
Influence of Humic Acid on Sorption of Neptunium(V) onto Soil
Authors: Sakamoto Y. , Nagao S. , Ohnuki T. , Senoo M. , Ohashi A. , Sato S. , Ohashi H.
Published: April 2011

The pH dependence of the stability constant of Np(V)-humate and the sorption of Np(V) onto soil was studied to clarify the influence of dissolved organic carbon on the migration behavior of Np(V) in soil layer. The stability constant of Np(V)-humate was expressed by logβ1=(0.35 ±0.03)pH+0.04±0.01 in the pH region from 5.3 to 8.7, and the intrinsic stability constant by logβ*1=3.66±0.05.

The sorption of Np(V) increased with pH up to pH 7, and tended to reach maximum, about 95%, at pH 9 in the absence of humic acid. In the presence of humic acid more than 140mg/l, the sorption of Np(V) was lower than that in the absence of humic acid above pH 7, while any influence of humic acid on the sorption of Np(V) onto soil was not observed below pH 7. The sorption behavior of Np(V) onto soil was explained by reversible sorption of NpO2+and sorption of NpO2CO3- and/or NpO2OH. Further, the influence of the size distribution of Np(V) on the sorption onto soil was examined and discussed.
Formation of Silicon on Insulator (Soi) With Separation by Plasma Implantation of Oxygen (Spimox)
Authors: Liu J.B. , Iyer S.S.K. , Min J. , Chu P. , Gronsky R. , Hu C. , Cheung N.W.
Published: April 2011

Buried oxide layers in Si were fabricated using non-mass analyzed plasma immersion ion implantation (PHI). We call this process of making separation by implantation of oxygen (SIMOX) with implantation by PIII as separation by plasma implantation of oxygen (SPIMOX). The implantation was carried out by applying a large negative bias to a Si wafer immersed in an oxygen plasma and a nominal dose of 2 × 1017 cm”2 of oxygen was obtained in less than three minutes. Cross section transmission electron microscopy (XTEM) and Rutherford backscattering spectrometry (RBS) were used to characterize the wafers. Three distinct modes of microstructure development were observed after post implantation annealing. With a low oxygen dose (< 1 × 1017 cm”2 ), isolated silicon dioxide precipitates did not grow large enough to form a continuous oxide layer. With a high oxygen dose ( > 3 × 1017 cm”2 ), however, a single buried oxide layer was observed. By optimizing the concentration ratio of 0+ and 02+ in the plasma and the implant dose, a double oxide layer (Si/oxide/Si/oxide/Si) structure, was produced in a single implantation step.
Erbium Doping of Silicon and Silicon Carbide Using Ion Beam Induced Epitaxial Crystallization
Authors: Boucaud P. , Julien F.-H. , Lourtioz J.-M. , Bernas H. , Clerc C. , Chaumont J. , Bodnar S. , Regolini J.-L. , Lin X. W.
Published: April 2011

Erbium doping of silicon and silicon carbide using implantation followed by ion beam induced epitaxial crystallization (IBIEC) is investigated. The implanted concentration of Er was 1.4 at% in both cases. In Si(100), Rutherford backscattering/channeling revealed that about 40% of the Er atoms evolved upon rapid thermal annealing from an undetermined position (room temperature) to an interstitial tetrahedral position (650°C) and finally to a substitutional position (950°C). The remaining Er atoms were presumably trapped in the small precipitates visible in high resolution transmission electron microscopy. The photoluminescence at 1.54 μπι of Er3+ is enhanced with annealing and persists up to room temperature after a 950 °C 1 min anneal. The high concentration of optically active Er atoms is illustrated by the lack of saturation of the photoluminescence at high pumping excitation intensity. Erbium was also implanted into cubic silicon carbide films prepared by chemical vapor deposition on Si at 900 °C. Both solid phase epitaxy (SPE) and IBIEC were performed. After a 950°C anneal, the low temperature photoluminescence at 1.54 μιη after IBIEC was five times higher in SiC than in silicon. The difference in photoluminescence linewidth between IBIEC (broad lines) and SPE (sharp lines) is explained in terms of interactions between optically active erbium atoms.
Characterization of Si Implantation and Annealing of InP by Raman Spectroscopy
Authors: Artus L. , Cusco R. , Martin J.M. , Gonzalez-Diaz G.
Published: April 2011

Raman scattering was used to assess the lattice damage caused by Si+implantation in InP, as well as the lattice recovery achieved after rapid thermal annealing (RTA). Semi-insulating InP was implanted with Si+with doses in the range of 1012to 5xl014cm”2. Raman scattering measurements show a progressive intensity reduction of the characteristic first- and second-order InP Raman peaks and an enhancement of the disorder activated modes with increasing dose. The onset of amorphization was found to be at about 1014cm”2. RTA of the implanted samples at 875 °C for 10s results in a very good recovery of the InP lattice even for the highest dose, as confirmed by Raman scattering measurements.
Atom Penetration from A Thin Film into the Substrates During Sputtering by Polyenergetic Ar+ Ion Beam with Mean Energy of 9.4 keV
Authors: Kalin B.A. , Gladkov V.P. , Volkov N.V. , Sabo S.E.
Published: April 2011

Penetration of alien atoms (Be, Ni) into Be, Al, Zr, Si and diamond was investigated under Ar+ ion bombardment of samples having thermally evaporated films of 30-50 nm. Sputtering was carried out using a wide energy spectrum beam of Ar+ ions of 9.4 keV to dose D=lxl0 -10 ion/cm2. Implanted atom distribution in the targets was measured by Rutherford backscattering spectrometry (RBS) of tT and He+ ions with energy of 1.6 MeV as well as secondary ion mass-spectrometry (SIMS).

During the bombardment, the penetration depth of Ar atoms increases with dose linearly. This depth is more than 3...20 times deeper than the projected range of bombarding ions and recoil atoms. This is a “deep action” effect.

The analysis shows that the experimental data for foreign atoms penetration depth are similar to the data calculated for atom migration through the interstitial site in a field of internal (lateral) compressive stresses created in the near-surface layer of the substrate as a result of implantation. Under these experimental conditions atom ratio r/rm (r¡ - radius of dopant, rm - radius target of substrate) can play a principal determining role.
Study of Titanium Nitrides Synthesized by High Dose Ion Implantation
Authors: Guemmaz M. , Mosser A. , Raiser D. , Grob J.J. , Cornet A. , Paletto S.
Published: April 2011

Polycrystalline titanium samples were implanted with N+ ions at high fluences and at several energies. The aim was to obtain 4000 Â thick nitrided layers of constant nominal concentration equal to 20% ,30%, and 40%.

The results obtained by RBS showed a flat nitrogen distribution with depth and the measured concentrations were respectively 20%,31% and 38%.

X-ray grazing incidence diffraction indicated that, at 20%, a nitrogen solid solution is formed in the a-Ti matrix. At 31% the nitrogen solid solution is present besides a 5-TiN phase and at 38% only the 5-TiN phase remains.

From nanoindentation measurements, we derived the depth-related hardness and Young's modulus of the implanted samples. These values were compared to those found on titanium nitride layers obtained with other coating techniques.
Implantation of Metal Ions into High Speed Steel for Improved Tribology
Authors: Ruck D.M. , Hirvonen J.-P. , Yan S. , Lappalainen R. , Torrfi P.
Published: April 2011

High speed steel with a martensitic microstructure is widely used in tool industry, but often the usage is limited by severe abrasive and corrosive wear. Metal ion implantation is a promising method to improve the tribological behaviour of this steel, as was shown in several publications. In this paper we discuss the application V and Cr implanted high speed steel, both of these elements are alloying constituents of the steel matrix. Combined with implantation of carbon is also carried out.

The tribological tests were performed with a pin-on-disc machine under dry sliding conditions. The obtained tribological results are discussed in relation to the microstructures of the nonimplanted and implanted samples.
Effects of Implantation Temperature on the Structure, Composition and Oxidation Resistance of Sic
Authors: Yang Zunde , Du Honghua , Libera Matthew , Singer Irwin L.
Published: April 2011

ɑ-SiC crystals were implanted with aluminum to a high dose at room temperature or 800°C. Studies by transmission electron microscopy showed that SiC was amorphized by room temperature implantation but remained crystalline at 800°C. Crystalline aluminum carbide was formed and aluminum redistribution took place in SiC implanted at 800°C. Implanted and unimplanted crystals were oxidized in 1 atm flowing oxygen at 1300°C. Amorphization led to accelerated oxidation of SiC. The oxidation resistance of SiC implanted at 800°C was comparable to that of pure SiC. The oxidation layers formed on SiC implanted at both temperatures consisted of silica embedded with mullite precipitates. The phase formation during implantation and oxidation is consistent with thermodynamic predictions.
Effect of Oxygen Implantation on the Electrochemical Properties of Palladium
Authors: Fujihana Takanobu , Ueshima Masato , Takahashi Katsuo , Iwaki Masaya
Published: April 2011

The electrochemical properties of O+-implanted Pd measured by cyclic voltammetry in a 0.25 mol dm-3 H2SO4 solution were investigated in relation to their composition and structure. Implantation of 16O+ was performed with doses between 1O17 and 1O18 ions cm-2 at 150 keV, and at nearly room temperature. SIMS, ERD combined with RBS, and XRD were used to analyze the composition depth profile and structure of O+-implanted Pd surface layers. The H atoms were accumulated with a gaussian distribution and carbon materials containing the solid solution of PdCx (x=0.13-0.15) were also formed in the near surface layers during O+-implantation. The distribution of implanted oxygen changed from gaussian to trapezoidal as the dose increased, accompanied by the crystal growth of Pd(OH)2, and simultaneously, the amount of accumulated H atoms increased. The voltammetric measurements revealed that with an increase in the dose, the hydrogen absorption was suppressed at the early stage of sweep cycles, and at the final stage, the redox reaction of both hydrogen and Pd was activated. From these results, we propose that the carbon materials containing the PdCx formed during O+-implantation suppress the hydrogen absorption, and the metallic Pd like a Pd-black formed by the reduction of Pd(OH)2 during voltammetric measurements causes the electrochemical activation of O+-implanted Pd.
Depth of Origin of Secondary Ions: Suppression and Enhancement of Ions Upon Passage Through Overlayers.
Authors: Sack N. J. , Akbulut M. , Madey T. E.
Published: April 2011

We are investigating the transmission of low energy ions (<10 eV) through ultrathin films of condensed rare gases. Our goal is to address the issue of the depth of origin of secondary ions that desorb from solid surfaces under the impact of ionizing radiation, such as electrons, photons, or through ion sputtering. The secondary ions are produced by electron stimulated desorption (ESD) from a suitable substrate, such as an oxide or an adsórbate on a metal single crystal; the overlayer gas is condensed onto this substrate. The yield, energy and angular distributions of the ions are measured as a function of overlayer thickness. We find that 7 eV oxygen ions can be transmitted through rare gas films (Kr, Xe) several ML thick. In contrast, O+ is completely suppressed by 0.5 ML of H2O. Surprisingly, we find the F− yield to be 4 times higher in the presence of 1 ML of Xe, compared to the clean surface value, accompanied by a dramatic change in the ions’ angular distribution. We discuss a model which considers elastic scattering and charge transfer of the ions with rare gas atoms, as well as the structure of the surface and the electronic properties of the solid-vacuum interface.
Defect Formation by Single Ion Impacts on Highly Oriented Pyrolytic Graphite Observed by Scanning Tunneling Microscopy
Authors: Reimann K. P. , Bolse W. , Geyer U. , Von minnigerode G. , Lieb K. P.
Published: April 2011

(0001) surfaces of highly oriented pyrolytic graphite (HOPG) were irradiated at 77K with 132Xe+ ions at energies between 50 keV and 900 keV. The ion fluences ranged between 1011 ions/cm2 and 1015 ions/cm2. Scanning tunneling microscopy (STM) was applied to image the irradiation induced defects at the surfaces. In case of orthogonal incidence and small ion fluence each incident ion induces one single hillock at the surface. These hillocks have typical lateral diameters of 2 nm and heights of several à. In many cases measurements of the hillocks with atomic resolution show disordered atomic arrangements. The hillocks are interpreted as the local volume expansion due to surface-near self-interstitials generated in the collision cascades of the ions. The high mobility of these interstitials parallel to the (0001) planes leads to a formation of interstitial clusters which cause the larger hillocks. Irradiation at an angle of incidence of 75° with respect to the surface normal effects a higher density of hillocks due to the higher number of recoils stopped in the uppermost lattice planes. The hillocks are arranged in chains which are aligned in the direction of the incident beam. Each of these chains marks a single collision cascade.
Thermal Stability Study of Oxygen Implanted Algaas/Gaas Single Quantum Well Structures Using PhotoreflectancE
Authors: Hughes P J , Li E H , Weiss B L , Jackson H E , Roberts J S
Published: April 2011

The effects of interdiffusion on the band structure of two MxGaUxAs/GaAs single quantum well (SQW) structures were studied using room temperature photoreflectance. Rapid thermal annealing of the SQW structures at temperatures of 800°C, 900°C and 1000°C for times up to 180 seconds resulted in limited interdiffusion. Low dose (1014 cm”2) oxygen implantation reduced the thermal stability of these structures where the extent of the interdiffusion was found to be greater for the implanted samples for identical annealing conditions.
Total Reflection X-Ray Fluorescence (TXRF)
Authors: Hockett R. S.
Published: April 2011

Total reflection X-Ray Fluorescence (TXRF) is a glancing x-ray analytical technique which is used primarily to measure surface metal contamination on semiconductor substrates. This is a review of Total reflection X-Ray Fluorescence (TXRF) applications for silicon semiconductor processing. In addition, some comments are made about the future of TXRF, and in particular, synchrotron radiation TXRF (SR-TXRF)
Elasticity Shear Modulus Modification By Impulsive Ion Implantation
Authors: Feugeas Jorge N. , Lambri O.A. , Grigioni G. , Sanchez G. , Povolo F.
Published: April 2011

Samples of pure copper were argon ion irradiated using a Plasma Gun operated in the detonation mode. The irradiated copper samples were studied by means of the Mechanical Dynamical Spectroscopy technique.
The results show an anomalous behavior in the Elasticity Shear Modulus, consisting in an abrupt jump in its value at ∼840K, repeated in the running up as well as in the running down part of the temperature cycling. A Damping Peak at that temperature was also observed.
Improved Near Surface Heavy Impurity Detection by a Novel Charged Particle Energy Filter Technique
Authors: Ishibashi K. , Patnaik B.K. , Parikh N. R. , Tateno H. , Hunn J.D.
Published: April 2011

As the typical feature size of silicon integrated circuits, such as in VLSI technology, has become smaller, the surface cleanliness of silicon wafers has become more important. Hence, detection of trace impurities introduced during the processing steps is essential. A novel technique, consisting of a “Charged Particle Energy Filter (CPEF)” used in the path of the scattered helium ions in the conventional Rutherford Backscattering geometry, is proposed and its merits and limitations are discussed. In this technique, an electric field is applied across a pair of plates placed before the detector so that backscattered particles of only a selected energy range go through slits to strike the detector. This can be used to filter out particles from the lighter substrate atoms and thus reduce pulse pileup in the region of the impurity signal. The feasibility of this scheme was studied with silicon wafers implanted with 1×1014 and 1×1013 14pe/cm2 at energy of 35 keV, and a 0.5 MeV He+ analysis beam. It was found that the backscattered ion signals from the Si atoms can be reduced by more than three orders of magnitude. This suggests the detection limit for contaminants can be improved by at least two orders of magnitude compared to the conventional Rutherford Backscattering technique. This technique can be incorporated in 200–300 kV ion implanters for monitoring of surface contaminants in samples prior to implantation.
Mass Spectrometric Studies of Pulsed Laser Ablation: Existence of Rydberg State Atoms
Authors: Leuchtner Robert
Published: April 2011

An unusual aspect of the pulsed laser deposition (PLD) process is that highly oriented (sometimes epitaxial) films of complex, multicomponent materials can often be prepared at low substrate temperatures. It is argued, using a simple model, that the arrival of even minor quantities of electronically excited species (Rydberg atoms and ions) can significantly affect the local surface temperature of the growing film. The present study experimentally confirms the existence of these energetic components in an ablation plume using a specially-modified time-of-flight quadrupole mass spectrometer. Ions as well as long-lived, excited state (Rydberg state) atoms were detected from laser ablation from a YBa2Cu307-5 (YBCO) target. Multiple peaks in the TOF profiles appear to derive from electron/ion recombination from higher charged species; the high kinetic energies observed are explainable from simple electrostatics involving localized holes trapped on the target surface.