bluuebunny/crossref_metadata_2025 huggingface dataset:
The Stability of Metals in the Atmosphere: New Chemical Insights to Old Problems
Authors: Graedel T.E.
Published: March 2011

The stability of metals (or lack thereof) upon exposure to the indoor or outdoor atmosphere places strong constraints upon many of their uses, including uses in advanced technologies. Two recent developments permit increased understanding of the processes that occur: a detailed knowledge of the chemical constitution of indoor and outdoor atmospheres and of precipitation, and extensive analytical studies of the corrosion layers of degraded metals. Among the insights revealed from these perspectives are (1) the participation in materials degradation of the sulfuric and nitric acids in small aerosol particles and in precipitation; (2) the presence of organic acid anions within corrosion films, revealing interactions with atmospheric formic, acetic, and oxalic acids; (3) the participation of dissolved hydrogen peroxide in the passivation or dissolution of the surface layers of metals; and (4) the frequent occurrence of insoluble mixed salts of hydroxide and either sulfate, chloride, or carbonate anions in the corrosion layers of many metals, suggesting that the rates of formation and dissolution of such minerals may be limiting steps in many stabilization or degradation processes.
MBE Growth of GaAs on an Exactly (001)-Oriented Si Substrate and Selective Epitaxial Growth for Fabrication of Modulation-Doped Fet's
Authors: Noge H. , Kano H. , Hashimoto M. , Igarashi I.
Published: March 2011

GaAs layers free of antiphase domains (APD's) have been grown by molecular beam epitaxy (MBE) on nominally (001)-oriented Si substrates. This is achieved by preheating the substrates at 950°C over 60 min or at 1000°C over 5 min in an ultrahigh vacuum. The maximum Hall mobility at 293 K is 5300 cm2/Vs for the APD-free GaAs layer doped with Si at a concentration of 2×1016 cm−3. Selective epitaxial growth of GaAs has been carried out on a Si substrate pattrened with SiO2, which was formed by wet O2 oxidation. By choosing an appropriate thickness of the SiO2 layer, thzxcSe warpage of wafers can be reduced to zero. While single-crystalline GaAs is grown on Si-exposed areas, highly-resistive (p ≧ 105 Ωcm) poly-crystalline GaAs is deposited on SiO2. This technique has been successfully applied for the device isolation of modulation-doped FET's (MODFET's, HEMT's, etc.) on Si without mesa-etching. The transconductance of the MODFET with a 3 μm-long gate reaches 88 mS/mm at 293 K.
Structural Characterization of Ion Beam Enhanced Solid Phase Epitaxial Regrowth by Raman, RBS, and X-Ray Analysis
Authors: Knudsen John F. , Bowman R. C. , Adams P. M. , Newman R. , Hurrell J. P. , Cole R. C. , Halle L. F. , Barker D. H.
Published: March 2011

Epitaxial regrowth of deposited amorphous silicon has been previously described utilizing ion implantation amorphization, ion mixing and thermal anneal. This paper evaluates the effects of these process steps on crystalline quality utilizing Rutherford Backscattering (RBS), x-ray diffraction rocking curves and Raman scattering.

In situ (during implantation) regrowth results in defective crystallinity. In contrast, when there is no in situ regrowth, the post anneal crystallinity is equivalent by RBS and x-ray evaluation to virgin single crystal wafers. In situ regrowth is most pronounced during the high beam current ion mixing type implants which produce wafer temperatures of about 250°C. The final crystalline quality which results from different sequences of amorphization and ion mixing implants, is strongly dependent upon the amount of in situ regrowth which has occurred. The greater the in situ regrowth the poorer the final crystalline quality.
Defect Structure of MEV Si Implantation in GaAs
Authors: Lee S.-Tong , Braunstein G. , Chen Samuel
Published: March 2011

The defect and atomic profiles for MeV implantation of Si in GaAs were investigated using He++ channeling, TEM, and SIMS. Doses of 1–10 × 1015Si/cm2 at 1–3 MeV were used. MeV implantation at room temperature rendered only a small amount of lattice disorder in GaAs. Upon annealing at 400°C for 1 h or 800°C for 30 a, we observed a ‘defect-free’ surface region (- 1 μ for 3 MeV implant). Below this region, extensive secondary defects were formed in a band which was 0.7 μ wide and centered at 2 μ for 3 MeV implant. These defects were mostly dislocations lying in the [111] plane. SIMS depth profiles of Si implants showed the Si peak to be very close to the peak position of the defects. The experimental profiles of Si were compared to the TRIM calculation; generally good agreement existed among the peak positions.
Damage Removal and Activation in Rapid-Thermally-Annealed Silicon Implanted Semi-Insulating GaAs
Authors: Tandon J. L. , Madok J. H. , Leybovich I. S. , Bai G.
Published: March 2011

In the Rapid-Thermal-Annealing of Si-implanted undoped semi-insulating GaAs three regimes are broadly identified. At ˜ 600°C, ion implantation damage is largely removed, as indicated by lattice-strain measurements performed by X-ray rocking curves. Between ˜ 600 – 900°C, “extended defects”, which presumably account for the long tails in the electron concentration depth profiles, are annealed. Higher annealing temperatures in this range result in profiles with successively shorter tails. Finally, beyond ˜ 900°C, “acceptor levels” in the material are revealed, which become effective in compensating the Si activation.
Degradation of Photoluminescence Efficiency in GaAs Under Low Intensity Laser Irradiation
Authors: Yasin M. , Raja A. , Brueck Steven R. J. , Osinski Marek , Mclnerney John G.
Published: March 2011

We report temporal measurements of bandgap photoluminescence (PL) from GaAs surfaces under low-intensity CW laser excitation. We have observed slow PL degradation in n-type, p-type and semi-insulating (Cr-doped and LEC-grown) samples, and have fit the data to a simple power law. Calculations indicate a significant contribution from the bulk material, possibly via recombination-enhanced generation or migration of non-radiative centers. The effectiveness of various methods of surface treatment (photowashing, deposition of epitaxial AlGaAs, spin-coating with organic and inorganic sulfide films) has been assessed. One specific technique, involving coating with sodium sulfide, is effective in enhancing the PL efficiency and suppressing the degradation, but these effects are not permanent.
Semiconductor Device research Using Non-Lattice Matched Structures
Authors: Woodall Jerry M.
Published: March 2011

Heterojunctions are ubiquitous to compound semiconductor devices. They are used for both device function and are remedial for problems associated with Fermi level pmining. In the past lattice matching was a critical feature for success. Most devices were made using either the GaAIAs/GaAs or InP/GalnAsP systems. Recently, there have been breakthroughs in the fabrication of devices using non-lattice-matched systems. These include high speed devices made of GaAs grown on Si, InGaAs/GaAs high speed and optoclectronic devices, infra-red photodetectors made of GaInAs grown on GaAs and GeSi/Si strained-layer superlattices. This talk will review this progress and discuss some of the materials and epitaxy issues likely to affect future trends in device research using non-latticematched layers.
Applications of Focused Ion Beams to Optoelectronic Device Fabrication - An Overview
Authors: Kubena Randall L.
Published: March 2011

Focused-ion-beam (FIB) technology has been applied during the past decade to a wide variety of device and circuit fabrication procedures. The ability to perform maskless implantation, selective sputtering and deposition, and high resolution lithography with a single system has allowed FIB researchers to explore a large number of unique fabrication processes for silicon, GaAs, and heterojunction devices. Currently, exploratory studies in advanced optoelectronic device fabrication employ the largest number of diverse FIB techniques. In this paper, the major application areas of FIB technology to optoelectronic research are reviewed, and possible uses of ultrasmall (≤500 Å) ion beams in the fabrication of optoelectronic device structures with novel properties are described.
Distribution of Boron Atoms in Ion Implanted Compound Semiconductors
Authors: Bowman R. C. , Knudsen J. F. , Downing R. G. , Kremer R. E.
Published: March 2011

The nondestructive neutron depth profiling (NDP) technique has been used to measure the boron (10B) distributions in GaAs, CdTe, Hg0.7 Cd0.3 Te, and Hg0.85 Mn0.15Te after multiple energy ion implants. The NDP results are found to be in good agreement with the theoretical ion ranges obtained from Monte Carlo computer simulations. Only minor changes in the boron profiles were seen for the chosen annealing conditions.
X-Ray Rocking Curve Analysis of S-Implanted GaAs
Authors: Fatemi M. , Thompson P.E. , Chaudhuri J. , Shah S.
Published: March 2011

The effect of rapid thermal annealing on strain reduction in 1.15 MeV S-implanted GaAs wafers irradiated to a dose of 5 × 1014/cm2 has been studied by double-crystal x-ray diffraction technique. X-ray rocking curves exhibit characteristic thin film fringes between the peak of unstrained GaAs and the major peak of the strained region. The maximum strain, i.e., the separation between the two peaks, as well as the number of minor fringes decreases with increasing RTA temperature, while the relative spacing between the fringes remains constant. At temperatures above 900°C, the main peaks begin to overlap; however, a residual positive strain can be measured for temperatures as high as 1100°C.
Characterization of Radiation Damage at the Nb Site in Natural Pyrochlores and Samarskites by X-Ray Absorption Spectroscopy
Authors: Greegor R. B. , Lytle F. W. , Chakoumakos B. C. , Lumpkin G. R. , Warner J. K. , Ewing R. C.
Published: March 2011

X-ray absorption spectroscopy has been used to investigate the Nb B-site in pyrochlores (A1.2B2O6Y0–1, Fd3m, Z=8) and samarskites (A3B5O16) in both metamict and annealed condition. The XANES and EXAFS measurements indicate significant changes in pyrochlore and smaller changes in samarskite as a result of radiation damage. In the metamict state the Nb site in both pyrochlores and samarskites is similar to Nb in Nb2O5. Short Nb-O (1.65Å) bonds are not disrupted by alpha-decay/recoil-nuclei events as much as longer bonds (2.00Å). This increases the asymmetry and static disorder at the local Nb site while long range order is greatly diminished resulting in considerable distribution in Nb-M distances and bond angles.
Characterization of Low-Gas-Release LHR Fuels by Transmission Electron Microscopy
Authors: Thomas L. E. , Guenther R. J.
Published: March 2011

Analytical transmission electron microscopy (AEM) was performed on light-water reactor (LWR) spent fuel samples from different radial locations in several low-gas release fuels. The examinations revealed high densities of sub-micrometer gas and solid aggregates. Precipitate coarsening and a change in the nature of the fission gas precipitates was observed near the centers of the fuel pellets. The fission-product phases were: 1) ε-ruthenium (Mo-Ru-Tc-Rh-Pd solid-solution alloy); 2) unidentified gases in intra- and intergranular bubbles from fuel edge to mid-radius locations; 3) dense, highly pressurized xenon/krypton “particles” associated with intragranular °-phase near the fuel centers. All other fission products apparently remained in solution. The nature and distribution of these phases are likely to affect fuel behavior in waste repositories and may be important for understanding fission gas behavior.
Detailed Characterization of LWR Fuel Rods for the U.S. Civilian Radioactive Waste Management Program
Authors: Guenther Richard J. , Blahnik D. E. , Campbell T. K. , Jenquin U. P. , Mendel J. E. , Thornhill C. K.
Published: March 2011

Characterizations are being conducted on light-water reactor (LWR) spent fuel with peak burnups from ∼31 to 46 MWd/kgM and rod-average fission gas releases of ∼0.3 to 11%. Measured concentrations of nuclides agreed within ∼10 to 15% of the predicted amounts. Radiochemistry of deposits on the cladding interior surface, fuel ceramography, beta/gamma autoradiog-raphy, and gamma scan data were consistent with fuel burnups and apparent operating temperatures. Microstructural observations also indicated increased porosity at the fuel center in high-release fuels and at the edge in high-burnup fuels. Cladding oxide thickness increased with exterior cladding temperatures as did the trend in hydriding.
Dissolution of UO2 at Various Parametric Conditions: A Comparison Between Calculated and Experimental Results
Authors: Olliia Kaija
Published: March 2011

The solubilities of uranium measured in deionized water, in sodium bicarbonate solutions as a function of carbonate concentration and in two types of synthetic groundwaters have been compared with those predicted using the reaction pathway program, PHREEQE. All the measurements were carried out under both air-saturated, oxidizing and anoxic, reducing conditions.

The experimental solubility values of uranium under oxidizing conditions are, in general, lower when compared to the corresponding theoretical ones calculated by PHREEQE. A critical factor is the choice of solubility constant for the solid phase. The reason for the lower solubility values may also be the mechanism of dissolution leading for example either to a situation where low dissolution rate is a limiting factor, or to formation of some solid phase of uranium with lower solubility. The experimental solubility values under reducing conditions appear to be in good agreement with the theoretical solubility values.
Creep Properties of Welded Joints in Copper Canisters for Nuclear Waste Containment
Authors: Ivarsson Bo , Österberg Jan-Olof , Sandström Rolf , Werme Lars
Published: March 2011

Copper canisters for nuclear waste containment can be expected to be exposed to temperatures up to 100°C. Since the material is pure copper, creep properties must be taken into account in particular for the welded joints in the canisters. In the paper creep rupture properties of parent metal, weld metal, and simulated heat affected zone are presented for 110°C. About ten times shorter rupture times were found for the weld metal in comparison to the parent metal. Cross weld specimens showed even shorter rupture times.
Basis for Selecting Cement-Based Waste Forms for Immobilizing Radioactive Waste
Authors: Mcdaniel Earl W. , Tallent Othar K. , Sams Terry L. , Delzer Dianne B. , Bostick William D.
Published: March 2011

Research at Oak Ridge National Laboratory (ORNL) has shown that cement-based waste forms can be tailored to tolerate wide fluctuations in waste-feed compositions and still maintain properties that are compatible with standard equipment and produce a product that meets regulatory requirements. The 20-year operational history of ORNL's grouting program has demonstrated this resilience and reliability on a spectrum of waste feeds encompassing the developmental history of the nuclear fuel cycle.

Cement-based materials are the most frequently used waste forms for solidifying non-high-level waste. These materials are also perhaps the most misused for immobilizing wastes. This paper discusses the scientific basis for selecting a suitable cement-based waste form to solidify and immobilize radioactive waste. For instance, when a given amount of cement (the source of calcium) is replaced with class F fly ash, the strontium leachability is reduced proportionally.

This paper discusses the use of gel clays such as bentonite and attapulgite to absorb excess fluids and thus increase waste loading. Also, cement-compatible natural materials such as nonswelling clays are used to ion exchange or absorb soluble ions such as cesium and thus reduce leachability.

Recently, blast furnace slag has been the subject of much interest in cement-based immobilization technology. Data are presented to show that a waste form containing blast furnace slag and other cementing materials is very effective in reducing the release rates of 99Tc.
Leaching Scale Effect for Cement-Waste Forms
Authors: Nomine J. C. , Billon A. , Courtois G.
Published: March 2011

The confinement ability of a waste package is one of the major safety characteristics to consider in shallow land burial. In order to determine if the confinement is acceptable, in accordance with local policy, one way is to proceed to leaching tests. The practical method, for sake of simplicity, cost and time limit, is to carry out the leaching tests on laboratory samples which are easier to prepare than full-scale blocks, but the representativity of which needs to be treated with caution; it is in this context, that one of the aspect of our work concerns what is known as the “scale effect”.

This study has been conducted using blocks the volumes of which are respectively of 200, 20, 2 and 0, 2 1, and made with the same cement-waste form (13 Cs) system.
Modelling of the Degradation of Cement in a Nuclear Waste Repository
Authors: Haworth A. , Sharland S. M. , Tweed C. J.
Published: March 2011

The current UK concept for a low- or intermediate-level nuclear waste repository includes a largely cementitious backfill. The cement provides a high pH environment in which the general corrosion rate of the metal canisters is reduced and the solubilities of many nuclides low. It has previously been assumed that this high pH will exist for a period of 107 years, however cement will degrade due to leaching of the solid components and attack from aqueous species in groundwater. In this paper we describe the preliminary stages of a model of the degradation of cement in a repository. The modelling involves the incorporation of a thermodynamic description of cement[2] into the static code PHREEQE[5]. This is then used in a coupled chemistry-transport model of simple leaching of cement using the code CHEQMATE[4]. This preliminary modelling also provides a useful verification of CHEQMATE as a direct comparison with a THCCDM (a coupled code based on CHEMTRN) model is possible. Results from this preliminary model suggest that the fall in pH due to leaching is slow. The model is sufficiently flexible to form the basis of more detailed investigations of the effect of groundwater interactions on the degradation of cement.
Hygroscopic Water Uptake and Dry/Wet Cycling Compared with Normal Water Exposure of Cemented Waste Forms
Authors: Brodersen K.
Published: March 2011

Considerable water uptake, formation of free liquid and leaching of activity may take place if cemented waste materials containing soluble salts are exposed to high humidity air. Another feature of importance for the structural stability of some materials is cyclic variations between water saturation and dry-out periods. The phenomena have been investigated on a laboratory scale using simulated waste in the form of cemented sodium nitrate or ion-exchange resins. Spherical samples are found to be valuable for simultaneous determination of the leaching of major components, mainly sodium, and the water uptake and swelling obtained from weight-increase measurements for the samples weighed in air and immersed in water.
Phase Development and Pore Solution Chemistry in Ageing Blast Furnace Slag-Portland Cement Blends
Authors: Macphee D. E. , Atkins M. , Glassar P. P.
Published: March 2011

Blast furnace slag (BPS) cement blends have certain advantages for the encapsulation of low and intermediate radioactive wastes. However, their hydration reactions are more complex than for Portland cement because Portland cements fully react within several years whereas slag hydration takes considerably longer. Empirical testing of blends matured for short periods, up to several years, are not therefore adequate to characterise the chemical immobilisation potential of such systems. A modelling approach is required to predict long—term properties.

This paper is concerned with defining the internal environment within slag-cement matrices. The important parameters for definition are pH, Eh, solubilities and speciation in the aqueous phase, and solid phase equilibria. Compatibility studies in the CaO-CaSO4-Al2O-SiO2-MgO-H2O system are described and compared with the results of X-ray diffraction on pastes aged up to 2 years. In addition, pore water compositions for slag-rich cements are given, and the potential for predicting their redox level(Eh) by extending the present model is discussed.
Leaching of Chlorine, Cesium, Strontium and Technetium from Cement-Fixed Intermediate Level Liquid Waste
Authors: Brodda Bert-G. , Mingxia Xu
Published: March 2011

The leaching behaviour of Cl-36, Cs-137, Sr-90 and Tc-99 from cement-fixed intermediate level liquid waste was investigated. Bentonite, MicroSili-ca®, acrylic resin and sodium sulfide were used as additives to a blast furnace cement matrix. In some cases portland cement was used. The liquid (water or waste solution) to cement ratio applied was mostly 0.47. Samples were leached with water or quinary brine (Q-brine).

After 250 days the sequence of leachability from additive-free specimen in Q-brine was Cl>Cs>Sr>Tc with little modification in water: Cs>Cl>Sr>Tc. Cl and Cs leaching are diffusion-controlled, Sr and Tc are chemically fixed.

Bentonite improves the retardation of Cs significantly, but has no significant effect on Cl, Sr and Tc. MicroSilica® deteriorates the retardation of Cs, but has no effect on Cl, Sr and Tc release.

Sulfide was expected to reduce the leachability of Tc by forming insoluble TC2S7. No significant effect was observed, however, because either TC2S7 does not form at the pH value of the cement slurry or, due to a solubility competition, insoluble Tc species also form in the absence of sulfide ions.

Acrylic resin does not reduce the leachability of Cs significantly. Irradiation with doses up to 4.4–105 Gy slightly deteriorates Cs retardation.

Applying a liquid to cement ratio of 0.35 instead of 0.47 improves the retardation of Cs by a factor of 1.5–4, which may be due to a reduction of porosity in the specimen.
Safety Analysis of a Sub-Seabed Repository of HLW
Authors: Karpf Armin-Dietmar
Published: March 2011

This national safety study of a repository in the Atlantic Ocean uses as much input from German research work as possible. It is based on a computer code IMPONADOR which can be run on a personal computer. It also introduces a new way of presenting information about radionuclide confinement to individual compartments to facilitate the understanding of release processes. The work is part of the international cooperation within the Seabed Working Group of the OECD/NEA.
Melodie : A Code for Risk Assessment of Waste Repositories in Deep Geological Formations
Authors: Lewi J. , Mejon-Goula M. J. , Goblet P. , Cernes A.
Published: March 2011

In order to perform the safety evaluation of nuclear waste repositories, a global model, called MELODIE, is currently being developed at the CEA/IPSN, in collaboration with other CEA teams and ENSMP (Ecole Nationale Supérieure des Mines de Paris). The version now in operation allows the assessment of the radiological consequences due to a repository located in a granitic formation for a period of several hundred thousands of years.

The calculations are based on models which represent the following physical and chemical phenomena:

– release of the radionuclides from the waste form and through engineered barriers,

– radionuclide transport through the geosphere,

– radionuclide behaviour in the biosphere.

Three separate models have been developed for each of these subjects; they are integrated in the code through a modular flexible dataprocessing structure.

In addition, a sensitivity and uncertainty analysis algorithm has been implemented into the code, which allows the evaluation of the influence of the parameter values on the result and of its uncertainty.

After a quite general description of MELODIE, we intend to present what has been done with it, mainly the calculations performed in the PAGIS (CCE) exercise: global dose calculations and ranking of the most important parameters through the sensitivity analysis.

We also note the studies performed with the geosphere module of MELODIE (METIS), especially the participation to the HYDROCOIN (0ECD/NEA) exercise. In addition, the main future development axes of MELODIE are outlined.
In-Situ Stress Measurement - Results of Experiments Performed at the Asse Salt Mine - Federal Republic of Germany
Authors: Feddersen H.-K.
Published: March 2011

High-level nuclear wastes are heat generating wastes. Heat will be transferred to the surrounding salt formation. This heating of the host rock will result in an increased temperature and in stress changes.

From 1983 through 1985 two underground tests were conducted in the Asse Salt Mine (Federal Republic of Germany) in which among others thermally induced stress changes were investigated.

In the Temperature Test 6 which was conducted at the 750 m-level only electrical heaters were used to simulate the heat generating high-level waste. Three hydraulic stress monitoring stations were arranged in the un-heated area at a distance of about 40 meters to the central heater. Measurements using AWIO flat jacks were also carried out in the heated region of the Temperature Test Field 6 (TVF 6).

The joint US/FRG Brine Migration Test (BMT) - a nuclear waste repository simulation experiment - was performed at the 800 m-level and used radioactive sources and electrical heaters to impose the heat load on the host rock. Stress change measurements during this experiment were performed using hydraulic pressure cells and straingaged stressmeters.

During 1985 an experimental area for the first in-situ test disposal of high-level radioactive sources was created at the 800 m-level within the Asse anticline structure. Thirty high-level radioactive canisters will be emplaced in six down-boreholes located in two test galleries in the experimental area. There is one additional borehole in each gallery equipped only with electrical heaters. Hydraulic pressure cells, AWID flat jacks, and straingaged stressmeters were installed in the HAW-test field for stress change measurements.
Retrieval and Analysis of Simulated Defense HLW Package Experiments at the WIPP
Authors: Molecke Martin A. , Rob Sorensen N.
Published: March 2011

In situ waste package performance experiments involving simulated (non-radioactive) defense high-level waste (DHLW) containers have been in progress since late 1984 at the Waste Isolation Pilot Plant (WIPP) facility. These experiments involve full-size, simulated DHLW containers of several metals and designs emplaced in the WIPP bedded rock salt. These test containers are surrounded by granular backfill (packing) materials, have in many cases been intentionally injected with brines, and are heavily instrumented. A majority of the test packages also contain nonradioactive DHLW borosilicate glass waste form, either within the container and/or outside of it. The primary purpose of these WIPP simulated DHLW experiments is to evaluate the in situ durability and performance of all waste package engineered barrier materials, and to perform package concept validation testing.

Twelve of the test DHLW containers, emplaced in WIPP test Room B, have been in heated operation since 1985 and had a maximum surface temperature of about 190°C. These containers were recently retrieved, after about 3 years of heated exposure, for detailed posttest laboratory analyses of: general corrosion and metallurgical degradation, waste form and backfill materials alterations, and other rock salt-brine-barrier materials near-field interactions with the “repository” geochemical environment. Test canisters and overpacks made of ASTM Grade-12 titanium showed essentially no visible degradation in either the base metal or welds; cast mild steel A216/WCA over-packs have suffered some uniform corrosion. Significant degradation of the removed instruments and associated test apparatus has been found: pieces of stainless steel (both 304L and 316) apparatus have undergone extensive stress-corrosion cracking failure and non-uniform attack; Inconel 600-sheathed instruments have undergone both extensive uniform and localized (pitting) attack. Granular backfill materials have been significantly compacted by creep closure to about a density of 2 kg/m. Laboratory analyses are still in progress. Further details on these materials results plus instrumentation data and other in situ WIPP waste package test observations are discussed.
Mechanical Properties of Swelling Clays
Authors: Broc D. , Plas F. , Robinet J. C.
Published: March 2011

The safety of vitrified radioactive waste disposal in granite is based on the concept of multiple barriers, which include an engineered clay barrier placed between the waste package and the granite. The mechanical properties of the swelling clays used were studied with a view to practical application for storage facility dimensioning. This involved a macroscopic examination of the clays swelling capacities (for sealing of storage boreholes) and fracture criteria (mechanical stability).
Natural Analogue Study of Volcanic Glass – A Case Study of Basaltic Glasses in Pyroclastic Fall Deposits of Fuji Volcano, Japan –
Authors: Arai T. , Yusa Y. , Sasaki N. , Tsunoda N. , Takano H.
Published: March 2011

A considerable range in alteration rates of basaltic glasses in various environments has been reported in previous studies. However, these studies paid only cursory attention to the environmental conditions under which the glass had been altered. In this study, the alteration of basaltic glasses was investigated and the environmental conditions and the alteration rate were discussed. Two sample ages were represented: 280 years and 2800 years. Basaltic glasses and their alteration layers were analyzed by electron probe microanalyzer (EPMA) and the thickness of the alteration layers were measured by scanning electron microscope (SEM). The ground water collected near the sampling point of Zunazawa Scoria and the pore water of both samples were analyzed. The alteration temperature and flow rate of water are estimated to be about 13t and 0.2 1/cm2/y respectively on the basis of meteorological data. The alteration layers of young aged basaltic glasses in freshwater conditions are similar to those of leached borosilicate glasses. The alteration rates of these basaltic glasses are estimated to be several um/1000y. The elemental concentrations in the ground water can be roughly explained as the result of leaching of the glasses.
Diffusion of Chloride and Uranium in Compacted Sodium Bentonite
Authors: Muurinen Arto , Pemtilä-Hiltunen Pirkkd , Uusheimo Kari
Published: March 2011

Sorption and diffusion of chloride (Cl-36) and uranium in conpacted sodium bentonite MX-80 were measured. No sorption was observed in the Sorption tests, however, in the diffusion tests slight sorption of uranium was noticed. The diffusivities of Cl-36 were found to be strongly dependent on the compaction of bentonite and on the salt concentration of the solution. Ion-exclusion can propably explain these phenomena.

The diffusivities of uranium were also strongly dependent on the compaction of bentonite. Uranium shews features of both ion-exclusion and sorption. Farther studies are, however, needed to explain the diffusion mechanisms of uranium.
Numerical Simulation of Cesium and Strontium Migration Through Sodium Bentonite Altered by Cation Exchange with Groundwater Components
Authors: Jacobsen J. S. , Carnahan C. L.
Published: March 2011

Numerical simulations have been used to investigate how spatial and temporal changes in the ion exchange properties of bentonite affect the migration of cationic fission products from high-level waste. Simulations in which fission products compete for exchange sites with ions present in groundwater diffusing into the bentonite are compared to simulations in which the exchange properties of bentonite are constant.
The Speciation of Uranium and Thorium at the Broubster Natural Analogue Site, Caithness, Scotland
Authors: Read D. , Hooker P. J.
Published: March 2011

Anomalously high concentrations of uranium, thorium and the rare earth elements (REE) are associated with peat-rich soils near Broubster, northern Scotland. The source of the anomaly has been traced to a hydrocarbon-containing mineralised zone within a uraniferous, calcareous Devonian sedimentary sequence. From there, the elements have been transported approximately 100 metres downslope and fixed within waterlogged peat deposits. The degree of concentration and fractionation accompanying actinide transport is extreme. This paper describes the results of a theoretical modelling exercise and complementary experimental study carried out to determine the chemical speciation of actinides at the Broubster site. Efforts made to identify mobilisation and retention mechanisms for uranium and thorium have led to the development of a simple model for actinide behaviour in the peat soils. The work, which forms part of an on-going programme of research into natural radionuclide migration, is primarily aimed at improving confidence in predictive models used for radiological assessment.
Modeling Flow and Transport in Fractured Crystalline Rock using the Discrete Fracture Network Concept
Authors: Dverstorp Björn , Nordqvist Wille , Andersson Johan
Published: March 2011

The conductive properties of fractured crystalline rock vary considerably in space, which implies that the flow is very unevenly distributed in space. The large variability raises doubts on modeling the flow with a large scale continuum model. Modeling flow in fractured crystalline rock in a network of discrete fractures provides an increased understanding of the character of the rock heterogeneity. Compared to a continuum model discrete models introduce new parameters such as statistical distributions for fracture orientation, radii, density and transmissivity that need to be estimated. By analyzing the migration experiment in the Stripa research mine in Sweden it is demonstrated how to calibrate and eventually validate a discrete model on field data. The flow analysis shows that the flow distribution on the drift roof and in two out of three vertical boreholes can be modelled with the same discrete model. The properties of the third borehole differ substantially. Initial attempts of analyzing the tracer experiment are also described.
The Migration Behaviour of Transuranium Elements in Gorleben Aquifer Systems: Colloid Generation and Retention Process
Authors: Kim J. I. , Buckau G. , Rommel H. , Sohnius B.
Published: March 2011

The colloid generation as a part of the migration process of trans-uranic ions has been studied in the Gorlben aquifer system. From the migration study for the Gorleben repository site, typical examples are selected to demonstrate the influence of colloids. The quantification of colloid generation and its influence on the dissolution and geochemical sorption of transuranium elements are discussed.
Testing Safety Assessment Models Using Natural Analogues in High Natural-Series Groundwaters. The Second Year of the Pocos De Caldas Project.
Authors: Smellie John , Chapman Neil , McKinley Ian , Franca Eduardo Penna , Shea Michael
Published: March 2011

Progress in the second year of the project is outlined in terms of four analogue objectives. Results of modelling of the preliminary data sets on groundwater chemical speciation of radionuclides, colloids, redox processes, and hydrothermal fluid transport are presented.
The Solubility and Sorption of Radium and Tin in a Cementitious Near-Field Environment
Authors: Bayliss S , Ewart F. T. , Howse R. M. , Lane S. A. , Pilkington N. J. , Smith-Briggs J. L. , Williams S. J.
Published: March 2011

The solubility and sorption of radium and tin have been studied for a cementitious near-field environment.

The solubility of radium was observed to be greater than 10−7M, even with the addition of IM sulphate to the cement equilibrated water. The values of Rn for radium varied from 102 to 103 ml g−1 for the cement types and initial radium concentrations studied.

The solubility of tin was observed to be about 10−4M for a range of cement equilibrated waters above tin oxides and metallic tin. The solubility of tin was observed to increase with pH. Tin solubilities were not affected by the redox conditions. Tin was present in a range of particle sizes in the sorption studies. A value of RD of 104 ml g−1 was observed for tin species less than 0.45μm.
Geochemical Analogue Study in the Krunkelbach Mine, Menzenschwand, Southern Germany: Geology and Water-Rock Interaction
Authors: Hofmann Beda A.
Published: March 2011

The mineralogy, geochemistry and hydrochemistry of water-bearing zones in the Krunkelbach vein-type U deposit, Southern Germany, have been investigated. The U ore body is aligned parallel and a few metres apart from a major waterbearing structure. Oxidation of pitchblende and of iron sulfides has been extensive down to a depth of at least 240 m. U retardation is due to neoformation of U(VI)-phases and to fixation on iron hydroxides, gorceixite and clay minerals. Under the prevailing conditions, Ra is fixed in baryte, but Ba and probably Ra were more mobile during earlier stages of the oxidation event, probably due to the presence of intermediate valence sulphur species as a product of pyrite oxidation.
U - Th - REE Mobility and Diffusion in Granitic Environments During Alteration of Accessory Minerals and U - Ores: A Geochemical Analogue to Radioactive Waste Disposal
Authors: Cathelineau M. , Vergneaud M.
Published: March 2011

U, Th and REE concentrations and distributions have been studied in granitic rocks, using a multidisciplinary approach involving fission-track micromapping of cracks in oriented samples, together with mineralogical and geochemical studies of the different U-Th-REE bearing phases. The behaviour of U, Th and Nd, considered as chemical analogue elements of the radiotoxic nuclides, was investigated either in the vicinity of microsites (accessory mineral environment) or along plurimetric sections around U-ore bodies. The different granite minerals, especially the accessory minerals (uraninite, monazite, thorite, apatite, xenotime), as well as U-ores, present different initial concentrations of U, Th and REE. Limitations to the analogy between these U-Th-REE concentrations and the radwastes is discussed as a function of their mineralogical features, chemical composition, size and solubilities. These primary concentrations present different behaviour when subjected to hydrothermal alteration, such as propylitization, phyllite type alteration, or clay alteration. Results show that in reduced media, in the temperature range 80–200°C, the rate of mobilization of U, Th, REE is relatively moderate. However, fluids enriched in fluorides, phosphates or carbonates may significantly solubilize and transport U and REE under specific conditions. In addition, the degree of opening of the microcracks and faults, as well as the oxidation-reduction processes, are critical parameters for the efficiency of the granitic geological barrier.
Effect of Environmental Materials on Aqueous Corrosion of R7T7 Glass
Authors: Godon N. , Vernaz E. , Thomassin J. H. , Touray J. C.
Published: March 2011

R7T7 glass behavior was investigated in contact with eleven different materials including smectites, bentonites, illites, granite and sand. The experiments were conducted at 90°C under atmospheric pressure with a 4 cm−1 SA/V ratio using two grams of material in double distilled water under static leaching conditions without renewal of the leachate. For each material a control test was conducted under the same conditions but without the glass specimen, as well as a series of tests on glass alone, without the environmental material. Kinetics studies lasting up to 364 days were performed on four selected materials.

The test results (mass loss, ICP analysis of the leachates, SEM and TEM observations) showed relatively slight glass alteration in contact with sand, granite and one bentonite (i.e. the same order of magnitude as glass alone in deionized water), but greater alteration of glass in contact with all the other clays.

The significant differences in glass behavior in contact with environmental materials can be accounted for by the behavior of the latter in solution: activated bentonite releases very large amounts of silicon and sodium into solution while smectite seems to remove silicon from solution.
Cluster Size Measurements in an Ionized Cluster Beam System
Authors: Turner D. E. , Lakin K. M. , Shanks H. R.
Published: March 2011

Ionized Cluster Beam (ICB) deposition has received considerable attention in recent years because of its potential application to low temperature semiconductor and metal film growth. To better understand this deposition process, however, it is necessary to determine the properties of the cluster source and the cluster size distribution obtained. This paper discusses the design of a time-of-flight mass spectrometer with single atom resolution for the measurement of cluster size in a conventional ICB deposition system. Results have been obtained for silver and germanium deposition. In both cases most of the clusters have been found to consist of less than 35 atoms. With the high resolution spectrometer it has been possible to show that certain cluster sizes are more stable than others.
A Comparison Between High- and Low-Energy Ion Mixing
Authors: Cheng Y.-T. , Cirlin E.-H. , Clemens B. M. , Dow A. A.
Published: March 2011

Diffusion in a thermal spike is shown to be the dominant mechanism for both high- and low-energy ion mixing. The similarity between high- and low-energy ion mixing is the result of the fractal nature of collision cascades.
Precipitation of Ar, Kr and Xe in Ni at Room Temperaturey
Authors: Liu A. S. , Birtcher R. C.
Published: March 2011

Transmission electron microscopy (TEM) has been used to study the precipitation of inert gases (Ar, Kr and Xe) injected into Ni at room temperature. The nucleation and size distribution of precipitates were found to be insensitive to the type of inert gas atom but dependent on gas concentration (ion fluence). The precipitate density decreases and the sizes increases with increasing gas concentration. In all cases, the inert gases precipitate as solid fcc crystals with their axes aligned with those of the host Ni lattice. For the same inert gas concentration, the lattice parameter is larger for the higher atomic mass in accord with bulk results. The lattice parameter of each type of inert gas precipitate increases with increasing gas concentration owing to the pressure relaxation that accompanies precipitate growth. This results in melting of large precipitates in accord with the behavior of bulk quantities of the gases at low temperatures.
The Effects of Ar-Bombardment on the Dissolution and Reprecipitation of Carbonitrides Implanted Into Low Carbon Steel
Authors: Ramos Stella M. M. , Amaral L. , Behar M. , Vasquez A. , Zawislak F. C.
Published: March 2011

The effects of Ar post-bombardment on the dissolution and reprecipitation of carbonitrides present in implanted 1020 low carbon steel are investigated using conversion electron Mössbauer spectroscopy (CEMS). The results are compared with similar experiments where samples of the same steel were post-bombarded with He. The experimental data show that the Ar is more efficient in the dissolution of precipitates and also more efficient in the precipitate retention at 450 °C, for the same peak concentration.
Temperature and Orientation Effects in Iron Nitride Crystal Formation
Authors: Lowder L. J. , Franzen W. , Culbertson R. J.
Published: March 2011

Pure rolled iron foils 0.025 mm thick have been implanted at two different angles of incidence and at several different temperatures. The implantation dose in each case was 5×1017 atoms/cm2. Both implanted and unimplanted foils were analyzed by transmission x-ray diffraction. Foils implanted at 320 ± 5°C exhibit peaks that correspond to the formation of several different phases of iron-nitride crystals, as observed by other investigators.[ 1,2] No such formation takes place at an implantation temperature of-20°C. We have evidence that the orientation of the iron nitride crystals is correlated with the orientation of the iron crystals.
Microstructural Characterization of Al2O3 Following Simultaneous Triple Ion Bombardment
Authors: Zinkle S. J.
Published: March 2011

The through-range microstructure of polycrystalline alumina has been examined by cross-section TEM following simultaneous implantation of 2.0 MeV Al+, 1.44 MeV O+, and 0.2 to 0.4 MeV He+ ions at room temperature to a dose of 3.1 keV/atom. The specimen remained crystalline following the irradiation, and four distinct radiation-induced defect features were observed: Network dislocations, dislocation loops, small cavities, and oblong clusters that may be aluminum colloids. The microstructure near the implanted ion region was qualitatively similar to that observed in irradiated regions far from the implanted zone.
Evaluation of Multilayers for Soft X-Ray Fabricated by Ion Beam Sputtering.
Authors: Kataoka I. , Yamada I. , Eto K. , Ito K.
Published: March 2011

Multilayer structures of Li20 and Ni were deposited onto polished fused quartz by the dual ion beam sputtering method. Optical and physical properties of the multilayer structure were evaluated. Reflectivity of multilayer mirrors at an incident angle of 79.6 deg. was 17% for 44Å(C-K line). There was good agreement with the calculated value considering the interface roughness and residual oxygen contamination in the Ni layer from the background of Li2O deposition.
Ion-Beam-Induced Epitaxy and Solute Segregation at the Si Crystal-Amorphous Interface
Authors: Poate J. M. , Jacobson D. C. , Priolo F. , Thompson Michael O.
Published: March 2011

Segregation and diffusion of impurities in amorphous Si during furnace and ion-beam-induced epitaxy will be discussed. The use of ion beams to enhance the crystal growth process has resulted in novel behavior for fast diffusers such as Au. Diffusion is enhanced in the temperature range 300–700 K with activation energies ∼0.3 eV. Segregation and trapping are analogous to behavior at liquid-solid interfaces
Study of Enhanced Solid Phase Epitaxy of Amorphous Silicon with Low Concentrations of Implanted Phosphorous
Authors: Jeon Young- Jin , Park Won Woo , Becker M. F. , Walser Rodger. M.
Published: March 2011

In this work we measured the functional dependence of the solid phase epitaxial (SPE) regrowth of amorphous silicon on the implanted phosphorous concentration, Np. The growth rates of self-ion amorphized layers in silicon wafers with (100) substrate orientation were measured by in situ, high precision, isothermal cw laser interferometry for temperatures from 460°C to 590°C, and concentrations in the range 2x1017 cm-3<Np<4x1020 cm-3. For low impurity concentrations, the fractional increase in the intrinsic SPE growth velocity ΔV/Vi depended linearly on Np as previously established for boron. For a given impurity concentration, the relative change V/Vi decreased with increasing annealing temperature.
Ion-Assisted Regrowth of Deposited Si Layers Mechanisms and Morphology
Authors: Priolo F. , Spinella C. , Ferla A. La , Battaglia A. , Rimini E. , Ferla G. , Carnera A. , Gasparotto A.
Published: March 2011

Ion-assisted regrowth of chemical vapor deposited amorphous Si layers was investigated for different cleaning procedures. The process was directly monitored by transient reflectivity measurements. The c-a interface stops at the deposited layer/substrate interface for doses depending on the effectiveness of the cleaning procedure in removing the native oxide. Small concentrations of twins are found in the regrown layer. Their amount is also correlated to the cleaning procedure. In oxygen implanted bare Si samples the ion-induced growth rate is reduced to 0.3 of the normal value at a peak O concentration of 1 X 1021/cm3. The results on the ion-induced regrowth of deposited layers are explained in terms of oxygen profile broadening during irradiation and retardation of the growth for the presence of dissolved O.