bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structure And Stress Evaluation Of Diamond Films Deposited On Ti-6A1-4V Alloy At Low Temperature Using Ch4/O2/H2 And CO/H2 Gas Mixtures
Authors: Catledge Shane A. , Vohra Yogesh K. 
Published: April 2011

ABSTRACTLow temperature diamond deposition on metal substrates is motivated by the need to reduce thermal stress so that the film adhesion is satisfactory. Although the use of oxygen-con- taining gas mixtures have been shown to extend the temperature range for which diamond can grow as well as to improve film quality, most studies have focused on the use of silicon as sub- strates and have neglected technologically important metallic systems. To this end, microwave plasma chemical vapor deposition (MPCVD) was used to grow diamond films on Ti-6A1-4V alloy at low temperature (615 to 780 C) using CH4/O2/H2 and CO/H2 gas mixtures. In-situ pyrometric interferometry (ISPI) shows that as the oxygen concentration increases, the onset time for dia- mond nucleation and subsequent film surface roughness increases while the average growth rate decreases. Micro-Raman spectroscopy shows improved film quality and suggests a trend toward increasing in-plane compressive stress with increasing oxygen concentration. Glancing-angle x- ray diffraction (XRD) was complimentary to the Raman data and indicates the presence of a TiC interfacial layer thickness which decreases with increasing oxygen concentration. We found that the CO/H2 mixture resulted in poorly adhered “white soot” films with low diamond content whereas the CH4/O2/H2 mixture yielded well adhered high quality diamond films.
Critical Issues In Measuring The Mechanical Properties Of Hard Films On Soft Substrates By Nanoindentation Techniques
Authors: Hay Jack C. , Pharr G. M. 
Published: April 2011

ABSTRACTThis study explores the difficulties encountered when using conventional nanoindentation techniques to measure the Young's modulus and hardness of hard films on soft substrates. In general, the indentation measurement of film/substrate systems is affected by four material properties: the Young's modulus and hardness of the film, and the Young's modulus and hardness of the substrate. For the particular case of a hard film on a soft substrate, there is a tendency for the material around the hardness impression to sink-in which results from the large difference in yielding of the two materials. In this study, a ‘model’ system consisting of NiP on annealed Cu was used to explore the behavior. This system is interesting because the film and substrate have similar Young's moduli, minimizing the elastic behavior as a variable. In contrast, the hardness of NiP is approximately 7–18 GPa, and that of the annealed copper is less than 1 GPa, providing a factor of 10 difference in the plastic flow characteristics. Experimental results indicate that standard analytical methods for determining the contact depth, hardness and Young's modulus do not work well for the case of a hard film on a soft substrate. At shallow contact depths, the measured indentation modulus is close to that of the film, but at larger depths sink-in phenomena result in an overestimation of the contact area, and an indentation modulus which is less than the Young's modulus of both the film and substrate. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) provide critical details of the physical processes involved, and illustrate how the standard data analyses overestimate the true contact area.
Disposal of Spent Sealed Radiation Sources in Borehole Repositories
Authors: Sobolev I.A. , Timofeev E.M. , Ojovan M.I. , Shiryaev V.V. , Arustamov A.E. , Kachalov M.B. 
Published: April 2011

ABSTRACTIn Russia the spent sealed radiation sources are disposed of into shallow ground borehole repositories. Design and status of the repositories as well as the basis for the safe disposal of the sources with metal matrices are presented.
Alkaline Degradation of Cellulose: Estimation of the Concentration of Isosaccharinic Acid in Cement Porewater
Authors: Van Loon L.R. , Glaus M.A. , Stallone S. , Laube A. 
Published: April 2011

ABSTRACTThe sorption of radionuclides on repository components (e.g. cement) is an important process since it controls the release of radionuclides from the repository [1]. A strong sorption of radionuclides is desirable since it will allow only a small release of radionuclides to the geo-and biosphere. The strong sorption behaviour of radionuclides, however, could possibly be decreased by several orders of magnitude by the presence of organic ligands. Ligands such as EDTA, NTA, citric acid etc. are inherent components of radioactive waste since these complexing agents are used in nuclear power stations for decontaminating purposes. Other ligands might be formed by degrading organic polymers present in low and intermediate level radioactive waste [2, 3]. Cellulose materials such as cotton, paper and wood form a substantial part (ca. 50 %) of the organic waste [1]. The use of large amounts of cement for constructing a repository causes alkaline environments in which the pH of the pore solution will remain above 12.5 for periods of the order of 105years [4]. It is well known from the literature that cellulose is unstable under alkaline conditions and will degrade to water soluble, low molecular weight compounds by the peeling-off reaction [5]. The main degradation product of cellulose is isosaccharinic acid (ISA), which is stable under alkaline conditions [5-10]. ISA enhances the solubility of Pu(IV) [7, 8] and has an adverse effect on the sorption of Eu(III), Th(IV) and Ni(II) [6]. For instance, in a solution of 10-3M ISA, the solubility of Pu(IV) at pH 12 increases by a factor of 20000 [11]. The sorption of Pu(IV) [8], Eu(III), Th(IV) and Ni(II) [6], however, was affected to only a minor extent. The observed effects were - by analogy with gluconic acid [12] - interpreted to be due to a strong complexation of these metals. The concentration of ISA in the pore water is the key parameter for evaluating its effect on radionuclide sorption [13].A full assessment of the effect of cellulose degradation on the sorption requires a detailed understanding of the mechanisms involved. The present study gives an overview of the different processes involved and describes how to quantify the concentration of isosaccharinic acid in the pore water of a repository.
Application of Petrological and Petrophysical Data for the Assessment of Radionuclide Retardation in Metavolcanites
Authors: Petrov V.A. , Poluektov V.V. , Kupriyanova E.Yu. 
Published: April 2011

ABSTRACTAn attempt was made to analyze the mechanism of the distribution of Sr and Cs isotopes depending upon petrochemical and petrophysical characteristics of metavolcanites of the basement forming the territory of the Production Association (PA) Mayak, Chelyabinsk District, Russia. It was found that radionuclide reterdation depends on the structure, density and mineralogy of intact rock.
Report on Workshop on Solute Transport in Compacted Bentonite
Authors: Hugi Markus , Apted Mick , Gilby David 
Published: April 2011

This workshop produced a lively discussion covering a number of issues relating to the transport of radionuclides through compacted bentonite. The predominant themes were:– the structural and chemical inhomogeneity of the compacted bentonite barrier– the process of radionuclide sorption in bentonite– the postulated process of surface diffusionThe main points of interest in this discussion are summarised here and some general conclusions are drawn.
Fundamental Science of f-Elements in Selected Immobilization Glasses: Significance for TRU Disposal Schemes
Authors: Haire R. G. , Assefa Z. , Stump N. 
Published: April 2011

ABSTRACTWe have investigated certain aspects of the fundamental chemistry and materials science of the 4fand several 5f-elements in three glass matrices. Two of these matrices were high-temperature (850° and 1450°C melting points) silicate-based glasses and the third was a sol-gel glass. Optical spectroscopy was the principal investigating tool. One aspect of the work here was to ascertain the oxidation state exhibited by these elements in the different glasses, as well as the factors that control and/or may alter this state. An important finding was noting a general correlation between the oxidation states obtained in the two high-temperature glasses and those observed in the oxides of these elements. Of the twenty three f-elements considered here, only three exceptions (Ce, Am and Bk) or examples of variable behavior (Pr, Tb, U and Cf) to this correlation were noted. One explanation offered for the exceptions is based on the stability afforded by the oxides' fluorite lattice. The correlation also applied to the sol-gel glasses after they had been heated. Other oxidation states for some elements could be obtained in the sol-gel glasses prepared at 25°C. Presented here is a summary of the oxidation states observed for these elements in three glass matrices and how these states correlate with those observed in the oxides of these elements and with the relative oxidation potentials for the elements.
X-Ray Absorption Fine Structure of Aged, Pu-Doped Glass and Ceramic Waste Forms
Authors: Hess N.J. , Weber W.J. , Conradson S.D. 
Published: April 2011

ABSTRACTX-Ray Absorption Fine Structure (XAFS) spectroscopic studies were performed on a suite of compositionally identical Pu-doped simulated waste glasses prepared 15 years ago at different aactivities by varying the239Pu/f238Pu isotopic ratio. The resulting α-activities range from 1.9 × 107to 4.2 × 109 Bq/g. These samples have a current, accumulated dose that ranges from 8.8 × 1018to 1.9 × 1018αdecays/g. A second suite of polycrystalline zircon samples that were synthesized 16 years ago with 10.0 wt.% Pu was also investigated. The239Pu238Pu isotopic ratio in these samples resulted in α-activities of 2.5 × 108and 5.6 × 1010Bq/g and an accumulated dose of 1.2 × 1017and 2.8 × 1019α-decays/g. The multicomponent composition of the simulated waste glass permitted XAFS investigation at six elemental absorption edges. For both the glass and ceramic waste forms, initial analysis of Extended X-Ray Absorption Fine Structure (EXAFS) and X-Ray Absorption Near Edge Structure (XANES) indicate that the local environment around the cations exhibit different degrees of disorder as a result of the accumulated a-decay dose. In general cations with short cationoxygen bonds show little effect from self-radiation where as cations with long cation-oxygen bonds show a greater degree of disorder with accumulated a-decay dose.
Effects of Water Redox Conditions and Presence of Magnetite on Leaching of Pu and Np From HLW Glass
Authors: Inagaki Y. , Sakata H. , Furuya H. , Idemitsu K. , Arima T. , Banba T. , Maeda T. , Matsumoto S. , Tamura Y. , Kikkawa S. 
Published: April 2011

ABSTRACTThe objective of this study is to evaluate the effects of water redox conditions and of the presence of iron corrosion products (magnetite) on the release of actinides from HLW glasses. Static corrosion tests were performed on a simulated HLW glass doped with Pu and Np in deionized water in the presence of magnetite under oxidizing and reducing conditions. The tests under oxidizing conditions were performed in air, while the tests under reducing conditions were performed in mixed gas (Ar+5%H2) atmosphere.The following results were obtained: (1) The presence of magnetite enhances formation of colloids containing Pu and Np in the leachates under both redox conditions. (2) Redox conditions have no remarkable influence on the release of Pu. (3) The reducing conditions combined with the presence of magnetite cause a decrease in the concentrations of Np dissolved species, which is probably the result of the reduction of Np(V) to Np(IV) at the magnetite surface.
Research Priorities in Nuclear Waste Management: A View From the Far Field
Authors: Richardson Philip J. 
Published: April 2011

ABSTRACTFirst of all I would like to express my appreciation to the MRS for the opportunity to address this symposium. I am especially pleased to be speaking alongside Charles McCombie and Soren Norrby, who have both made me feel welcome whenever we have met in the past. I have been more active in Sweden over the last few years, as Soren will know. Perhaps it is now time I turned my attentions to Switzerland as well.
Sintered (Sr,U)-Containing Zirconolite Ceramics Study
Authors: Stefanovsky S.V. , Ioudintsev S.V. , Ochkin A.V. , Ptashkin A.G. , Chizhevskaya S.V. 
Published: April 2011

ABSTRACTZirconolite-rich ceramics, containing strontium (∼1 wt.%) or uranium (5-20 wt.%) were prepared by cold pressing of mechanically activated oxide powders and sintering in air at 1200 TC for 2 hours. They were examined with XRD, optical and electron microscopy (SEM/TEM/EDS) methods. Zirconolite content in the samples was found to be as much as 85-90 vol.%, Baddeleyite, rutile, and perovskite (in the Sr-containing sample only) were present as minor phases. In the U-containing samples, two zirconolite varieties with different Zr/U ratio were found: zirconolite-1 and zirconolite-2 with average compositions Ca0.90Zr0.95U0.10Ti2.00O7.00, and Ca1.15Zr0.40U0.50Ti2.02O7.00 respectively. The amount of zirconolite-2 increases from ∼1 vol.% in the sample with the lowest uranium content to >50 vol.% in the sample containing ∼20 % U02. In the latter sample about 5 vol.% of cubic pyrochlore-type phase was also present.
Commentary on Studies of 36Cl in the Exploratory Studies Facility at Yucca Mountain, Nevada
Authors: Murphy William M. 
Published: April 2011

ABSTRACT36Cl data from the Exploratory Studies Facility (ESF) at Yucca Mountain, Nevada, reported by LANL researchers [1,2,3,4] provide important empirical constraints on the velocity and pathways for water flow under natural conditions in the unsaturated zone at Yucca Mountain. It has been concluded that some data exhibiting exceptionally high 36Cl/Cl ratios (i.e., greater than 1250×10−15 [3]) indicate unambiguous bomb pulse contamination and fast groundwater travel times to depths of the proposed waste emplacement horizon. Several lines of evidence indicate that some ESF samples with 36Cl/Cl ratios greater than 900×10−15 to 1000×10−15 are also affected by bomb pulse contamination. The distribution of 36Cl/Cl data can be well represented by a mixture of two normally distributed populations, which are hypothesized to represent uncontaminated and bomb pulse contaminated sets. The transition between these groups occurs at 36Cl/Cl between 600×10−15and 1000× 10−15, and the hypothesized contaminated samvles comprise 20 to 25 percent of the total. Shapiro-Wilk statistics confirm that when samples with 36Cl/Cl ratios greater than about 1000×10−15 are included, the distribution deviates from normality. Variation in the Earth's magnetic field, which is a primary mechanism for variation in natural 36Cl production, also appears to be normally distributed, supporting the hypothesis that natural, relatively undecayed 36Cl/Cl ratios are normally distributed. Further evidence that samples with 36Cl/Cl greater than 950×10−15 to 1000×10−15 are likely to have a bomb pulse component is provided by the spatial correlation of these samples with those containing unambiguous contamination at values greater than 1250×10−15. Zones in which elevated 36Cl/Cl ratios are localized constitute about 23 percent of the length of the ESF at the level of the proposed waste emplacement horizon.
The Role of Engineered Barriers in the Performance Assessment of a Repository for L/ILW
Authors: Askarieh M.M. , Chambers A.N. , Hickford G.E. , Sharland S.M. 
Published: April 2011

ABSTRACTDesigns for repositories for the underground disposal of radioactive waste throughout the world are generally based on the ‘multiple barrier’ concept. This comprises engineered barriers that are the introduced features of the disposal facility, and natural barriers provided by the host geology. In the near field of the repository, the engineered barriers can provide both physical and chemical containment. This paper is mainly concerned with the deep disposal of intermediatelevel and low-level waste. In particular, it reviews current understanding concerning the evolution of the chemical and physical barriers for the disposal concept developed by United Kingdom Nirex Limited. Examples of work from underlying research programmes that support this understanding are discussed. The paper also discusses the representation of the engineered barriers in performance assessment calculations.
Dissolution of a Complex Borosilicate Glass at 60°C: The Influence of pH and Proton Adsorption on the Congruence of Short-Term Leaching
Authors: Abraitis P. K. , Vaughan D. J. , Livens F. R. , Monteith J. , Trivedi D. P. , Small J. S. 
Published: April 2011

ABSTRACTThe short-term dissolution behaviour of a complex borosilicate glass has been investigated by controlled pH leaching, surface titration and leach rate temperature dependence experiments. The results indicate that the rates, congruence and mechanisms of dissolution vary significantly with pH. At low pH, dissolution occurs via a proton-promoted mechanism which results in enhanced release of B and many network modifying elements (relative to Si). At 60°C in high pH media, dissolution is essentially congruent. Here, dissolution is surface reaction controlled and occurs via a hydroxyl-promoted network dissolution process. Selective leaching is favoured at low and near-neutral pH. Congruent dissolution occurs in solutions of pH greater than that at the point of zero net proton charge.
Influence of Iron(II) and Iron(III) Ions on the Corrosion of MTR Fuel Element Claddings in Repository-Relevant Brines
Authors: Zschunke S. , Fachinger J. 
Published: April 2011

ABSTRACTAfter the USA decided in 1988 to no longer accept spent fuel elements from German material test reactors (MTR), a national back-end fuel cycle alternative was sought in the Federal Republic of Germany [1]. The aim is their direct final disposal in deep, stable geologic formations. The corrosion of material test reactor (MTR)-fuel element claddings (aluminium) in repository-relevant brines was examined. Before the aluminium cladding material can corrode, the POLLUX cask, containing the fuel elements, must be corroded. In this case, iron(II) and iron(III) ions are present in the brine. These ions decisively influence the corrosion of the MTR fuel element cladding material, therefore the mechanism responsible for this phenomenon should be identified. Tests were performed in which Fe(II) and Fe(III) salts were added to the brines. In these experiments, the percentage mass decrease of the aluminium cladding, the iron content of the brine, as well as the pH value were determined. As expected the results provided the information about the corrosion mechanism. The higher the concentration of iron ions in the brines, the higher the aluminium corrosion rate was for all three brines. Identical redox equilibria between Fe(II) and Fe(III) were formed in the brine, irrespective of whether Fe(II) or Fe(III) salt had been added. It is assumed that the acceleration of the corrosion rate is based on the fact that Fe(II) is reduced to metallic iron by absorbing the electrons produced during the oxidation of aluminium to Al(III). The aluminium cladding material does not function as a barrier for the release of radionuclides from the fuel elements. The results of this study show that the 0.38 mm thick aluminium cladding will corrode through after approximately four weeks.
Waste Management in a National Research Laboratory
Authors: Beer H.-F. , Jermann M. 
Published: April 2011

ABSTRACTBecause of its experience in handling radioactive materials including waste generated on-site PSI was charged with managing the treatment and interim storage of the radioactive waste from medicine, industry and research in Switzerland. Combustible operational waste from the Swiss nuclear power plants is conditioned on a contract base and stored temporarily at the sites of the power plants. Because of the decommissioning of old facilities provoked by the change in the research priorities at PSI, temporarily an additional amount of waste is released on-site to be treated. PSI possesses the facilities and the organisational structure to fulfil the tasks it is charged with. In the near future the major part of the conditioning procedures, except the conditioning of some of the waste containing α-emitters, will be performed by ZWILAG. PSI will stay responsible for the management, organisation and interim storage of all radioactive waste, except for nuclear power plant waste, as before.
Interaction of Alkalis (CS+) With Calcium Silicates Hydrates
Authors: Faucon P. , Charpentier T. , Henocq P. , Petit J.C. , Virlet J. , Adenot F. 
Published: April 2011

ABSTRACTC-S-H of different Ca/Si ratios were synthesized in suspension. Cesium chloride (0.5 M) was put in contact with these C-S-H in reactors for 30 days at 25 °C with solution/solid ratios of 50. The quantities of cesium fixed by the C-S-H was determined by microanalyses and the mechanisms of retention in relation with the C-S-H structure was investigated by 133Cs Nuclear Magnetic Resonance (NMR). The influence of the humidity yield in which the C-S-H were stored was also studied.At 100% of humidity, some cesium ions are trapped in the pore network of the C-S-H. However, most cesium ions are incorporated in the hydrated interlayers of the C-S-H between the silica chains of the structure. They are mobile in this interlayer space. At high Ca/Si ratio, the charge of incorporated Cs+ ions in the structure should be compensated by the associated Cl- incorporation. At low Ca/Si, the presence of silanol groups in the C-S-H structure, which becomes closer to that of tobermorite (Ca/Si about 0.8), makes possible the exchange or substitution H'<->Cs'. The resulting retention of cesium in the C-S-H then becomes higher.
XRD Examination of Slags Produced by Incineration of Solid Wastes With Metal Fuel
Authors: Karlina O.K. , Ojovan M.I. , Stefanovsky S.V. , Varlakova G.A. 
Published: April 2011

ABSTRACTA mixture of powdered magnesium-aluminum alloy (with composition close to Mg4A13), calcium silicide, and potassium nitrate as oxidizer was applied as metal fuel to incinerate various solid radioactive wastes (biomaterials, ion-exchange resin, etc.) and to produce glass-like materials. Materials obtained were examined with X-ray diffraction to identify mineral phases formed during incineration and vitrification processes. It has been established that solid waste incineration resulted in a formation of a slag product composed of stable mineral phases: oxyapatite, nagelschmidtite, spinels, karnegiite, which can be considered as host phases for radionuclide immobilization. Waste vitrification with metal fuel yields an amorphous phase which is predominant in final products, and a small amount of crystalline phases. Preliminary leaching tests were carried out. Leach rate of 137Cs in deionized water at 20 °C was found to be by order of magnitude 10−5 g-cm−2 day−1. Leach rates of 90Sr and 238Pu were approximately one order of magnitude lower.
Interaction of Eu(III) and Th(IV) With Sulfate-Resisting Portland Cement
Authors: Wieland E. , Tits J. , Spieler P. , Dobler J.P. 
Published: April 2011

ABSTRACTThe uptake of Eu(III) and Th(IV) by a sulphate-resisting Portland cement has been investigated in batch type sorption experiments using 152 Eu and 234Th as tracers. Prior to performing sorption studies, the experimental methodology was assessed. The kinetics of Eu(III) and Th(IV) interactions with cement were measured for times up to about 130 days. The effect of isosaccharinic acid added to artificial cement pore water on Eu(III) and Th(IV) uptake was examined to elucidate the effect of cellulose degradation products.