bluuebunny/crossref_metadata_2025 huggingface dataset:
Sub-critical telephone cord delamination propagation and adhesion measurements
Authors: Volinsky Alex A. , Waters Patrick , Kiely James D. , Johns Earl C.
Published: April 2011

Thin film delamination can occur when the stored elastic energy per unit area in the film due to the residual stress exceeds the interfacial toughness. Telephone cord morphology is commonly observed in delaminating thin films under compressive stresses. Here, the biaxial film stress is partially relieved by film buckling in the direction perpendicular to the telephone cord propagation, and by “secondary” blister buckling in the direction of telephone cord propagation, which results in the sinusoidal fracture patterns.

A superlayer indentation test, in which additional stress is supplied to the crack tip using a nanoindenter, can be used to measure the interfacial toughness. Estimates of the energy release rate for diamond-like carbon (DLC) films on magnetic media were obtained using the superlayer indentation test, as well as the delaminated buckling profiles. The results obtained by these two independent methods are in good agreement with each other. We find the average adhesion energy to be 6 J/m2 for DLC films on magnetic media.

Normally telephone cord blisters “run out of steam” and stop once the interfacial toughness exceeds the strain energy release rate. It is possible to make blisters propagate further by either putting mechanical energy into the system, or by introducing liquids at the crack tip, thus reducing the film interfacial toughness. Environmental species can assist cracking and contribute to thin film delamination, which is readily observed in vintage mirrors. Crack propagation rates on the order of microns per minute were measured for DLC films in different fluid environments. We identify how telephone cord buckling delamination can be used as a test vehicle for studying crack propagation rates and environmentally assisted cracking in thin films.
Superelastic Thin Film NiTi-Polymer Composites and Sputtered Thin-walled Tubes
Authors: Rumpf Holger , Zamponi Christiane , Bourauel Christoph , Drescher Dieter , Quandt Eckhard
Published: April 2011

Superelastic shape memory materials are of special interest in medical applications due to the large obtainable strains, the constant stress level and their biocompatibility. Superelastic NiTi-polymer-composites have the potential to be used for novel applications in orthodontics and medical instrumentation as well as in certain areas of mechanical engineering. Especially, using NiTi thin films these composites have the potential to substantially reduce those forces compared to conventional NiTi wires and tubes. In orthodontic applications lowering the forces during archwire treatment is of special importance due to tooth root resorption, which can be caused by the application of oversized forces. Furthermore, the use of superelastic materials or composites enables the application of constant forces independent of diminutive tooth movements during the therapy due to the superelastic plateau. Superelastic NiTi thin films have been fabricated by magnetron sputtering using extremely pure cast melted targets. Special heat treatments were performed for the adjustment of the superelastic properties and the transformation temperatures. A superelastic strain exceeding 4% at 36°C was obtained. In this paper the fabrication of superelastic NiTi thin walled tubes by magnetron sputtering is presented and their mechanical properties are compared to conventional wires and tubes in view of orthodontic applications.
Applying NiTi Shape-Memory Thin Films to Thermomechanical Data Storage Technology
Authors: Crone Wendy C. , Shaw Gordon A.
Published: April 2011

As the data storage density in cutting edge microelectronic devices continues to increase, the superparamagnetic effect poses a problem for magnetic data storage media. One strategy for overcoming this obstacle is the use of thermomechanical data storage technology. In this approach, data is written by a nanoscale mechanical probe as an indentation on a surface, read by a transducer built into the probe, and then erased by the application of heat. An example of such a device is the IBM millipede, which uses a polymer thin film as the data storage medium. It is also possible, however, to use other kinds of media for thermomechanical data storage, and in the following work, we explore the possibility of using thin film Ni-Ti shape memory alloy (SMA). Previous work has shown that nanometer-scale indentations made in martensite phase Ni-Ti SMA thin films recover substantially upon heating. Issues such as repeated thermomechanical cycling of indentations, indent proximity, and film thickness impact the practicability of this technique. While there are still problems to be solved, the experimental evidence and theoretical predictions show SMA thin films are an appropriate medium for thermomechanical data storage.
Raman Imaging and Thermal Expansion of Highly Textured Pb(Mg1/3Nb2/3)O3-PbTiO3 Piezoelectric Ceramics
Authors: Colomban Philippe , Pham-Thi Mai
Published: April 2011

PMN(PZN)-PT single crystals exhibit unique electromechanical properties when oriented and poled along the <001> direction. While expensive crystal growth techniques are advancing slowly, it is of great practical importance to develop an alternative low-cost production method based on strongly oriented or textured ceramics. We present here the thermal expansion, dielectric properties and Raman spectroscopy study of Pb(Mg1/3Nb2/3)O3-PbTiO3 solid solution ((1-x)PMN-xPT, 0.2<x <0.4, here after called PMN xPT) single crystals, random ceramics and ceramics prepared by homo-templated grain growth (HTGG) using cubic PMN-PT single crystal seeds as templates and nanoparticles as ceramic matrix. Representative medium to highly textured ceramics were sintered at 1150°C and 1200°C, respectively, and studied by Raman imaging. Raman peak centre of gravity is used to image the x-composition whereas peak intensity is correlated to the unit-cell distortion and related short-range structure. Smart Raman imaging shows that the final composition is very close to that of the matrix. We compare their thermal expansion (-150 to 300°C) and dielectric properties (R.T. to 300°C) with those of corresponding poled or non-poled single crystals and random ceramics homologues. Short-range ordering and phase diagram are discussed.
A Shape Memory Polymer with Improved Shape Recovery
Authors: Liu Changdeng , Mather Patrick T.
Published: April 2011

Thermally actuated shape memory polymers (SMPs) interest, both academically and industrially, due to their ability to memorize a permanent shape that is set during processing and a temporary shape that is later programmed by manipulation above a critical temperature, either Tg or Tm. However, the thermal triggering process for SMPs is usually retarded compared to that of shape memory alloys, because the thermal conductivity of polymers is much lower (<0.30 W/m.K). In the present study, we incorporated a highly thermal conducting filler into a shape memory matrix to increase its thermal conductivity and therefore, shorten the heat transfer progress. A mathematical was worked out that quantitatively relates the material's thermal conductivity with the heat transfer time, τ, also defined as a shape memory induction time. The model fit nicely with our experimental data. In addition, mechanical reinforcement was observed with the addition of this rigid thermal conducting filler.
Controllable growth of single walled CNTs using nanotemplates from diblock copolymers
Authors: Lu Jennifer , Bai Jia , Moll Nick , Roitman Daniel , Yang Dorothy , Fu Qiang , Liu Jie , Rider David , Manners Ian , Winnik Mitch
Published: April 2011

We use diblock copolymers as nanotemplates to produce various catalyst nanoclusters or catalyst-containing inorganic nanostructures with controlled size and spacing for carbon nanotube growth. We are able to generate periodically ordered catalytic nanostructures by spin coating polymer-based catalyst systems. As a result, uniformly distributed, low defect density single walled nanotubes(CNTs) have been obtained. CNTs with diameters of 1nm or less have been produced from iron-containing inorganic nanostructures using conventional chemical vapor deposition. The superior film forming ability of polymer-based catalyst systems enables selective growth of carbon nanotubes on lithographically predefined catalyst islands over a large surface area. The ability to control the density and location of CNTs offers great potential for practical applications. The initial MALDI-MS (Matrix Assisted Laser Desorption Ionization-Mass Spectrometry) results indicate that we can positively identify bovine serum albumin (BSA) at 500 attomoles using CNT surfaces produced by this method.
SWNT NETWORK for BIOMOLECULE DETECTION
Authors: Atashbar Massood Z. , Bejcek Bruce , Singamaneni Srikanth
Published: April 2011

In this paper we describe a single wall carbon nanotube (SWNT) based biological sensor for the detection of biomolecules using streptavidin and IgG. Two types of sensing mechanisms have been used to demonstrate the ability of carbon nanotubes to form nanoscale biosensors. The first sensing mechanism involves a CNT based conduction sensor in which the decrease in the current was observed when the specific biomolecule was bound. In the second mechanism Quartz Crystal Microbalance (QCM) was used to quantify the mass of the biomolecule bound on the sidewalls of the carbon nanotube. Both sensing mechanisms proved to be efficient and consistent. Immobilization of the biomolecules on the carbon nanotube surface was confirmed by Atomic Force Microscopy.
Low Temperature Growth of Carbon Nanotubes and Nanofibres
Authors: Robertson J , Hofmann S , Kleinsorge B , Golokov V , Ducati C , Geng J , Cantoro M , Boskovic B , Huck W , Johnson B F G
Published: April 2011

This paper reviews work on low temperature growth of carbon nanotubes, on Si, on plastic, on carbon cloth, using sputtered and colloidal catalysts, and with nano-imprinted patterning.
Bulk Synthesis of Helical Coiled Carbon Nanostructures
Authors: Wang Wei , Rao A. M.
Published: April 2011

Three dimensional helical coiled carbon nanostructures including coiled nanowires and nanotubes were synthesized at ambient pressure using a thermal chemical vaporization deposition (CVD) process in which xylene and acetylene were used as the primary carbon source. A bi-metal catalyst formed from a mixture of ferrocene and indium isopropoxide served as the seed to initiate the growth of these helical coiled nanostructures. The as-synthesized coiled nanowires and nanotubes are pure without the presence of amorphous carbon nanoparticles. By precisely controlling the atomic ratio of In / (Fe+In), coiled nanowires or nanotubes can be synthesized exclusively. The diameters of the as-grown coiled nanowires vary from several tens to several hundreds nanometers, whereas the diameters of the coiled nanotubes are around 20 nm. The structure of coiled nanowires and nanotubes were determined using scanning electron microscopy and transmission electron microscopy. The key novel aspects of this research are: (i) to synthesize helical coiled nanotubes or nanowires exclusively by controlling the bi-catalyst concentration of Fe and In, and (ii) no preformed substrates are required which implies that our process is amenable for scaled-up synthesis of these nanostructures.
Thermal Conductivity of Single-Walled Carbon Nanotube/PMMA Nanocomposites
Authors: Guthy Csaba , Du Fangming , Brand Stijn , Fischer John E. , Winey Karen I.
Published: April 2011

Due to their exceptional thermal properties, single-wall carbon nanotubes (SWNT) are considered as very promising filler materials for improving the thermal conductivity of conventional polymers. We carefully investigated the thermal conductivity of SWNT/PMMA nanocomposites with SWNT loading in the range up to10 wt% using the comparative technique. The samples were prepared by coagulation method. We demonstrated moderate improvement in the composites’ thermal conductivity of about 250% at 10wt%. The experimental results were analyzed using the versatile Nielsen model, which takes into account many important factors, like the fillers aspect ratio and maximum packing fraction. The aspect ratio of SWNT material used to prepare our composites was determined by AFM and careful image analysis in order to use it as an input parameter in the Nielsen model. We obtained good agreement between our experimental results and the predictions of the Nielsen model. Based on our analysis we concluded that higher aspect ratio of filler material was needed to achieve better improvement in the composites thermal conductivities. One should also take steps in order to improve the thermal contact between the SWNT network and the matrix material.
Chemically Engineered Carbon Nanotube-Polymer Composite Coatings for use as Remote Strain-Sensors
Authors: Halary Jérôme , Stanford John L. , Lovell Peter A. , Young Robert J.
Published: April 2011

Carbon nanotubes nanocomposites with unique opto-mechanical properties have been developed as smart coatings. Remote polarized Raman spectroscopy has been used to monitor optical strain sensitivity of deformed coatings and determine local strains on the micron scale directly from stress/strain induced Raman band shifts.

Chemically engineered carbon nanotubes and polymer matrices have been developed in order to overcome the limitations highlighted in previous reports. They have proved to be of significance importance in the optimization of the stress transfer between the nanotubes and the polyurethane matrix.
Random Telegraph Noise in Individual Single-walled Carbon Nanotubes
Authors: Jhang SungHo , Lee SangWook , Lee DongSu , Campbell Eleanor E. B. , Roth Siegmar , Park YungWoo
Published: April 2011

The switching of resistance between two discrete values, known as random telegraph noise (RTN), was observed in individual single-walled carbon nanotubes (SWNTs). The RTN has been studied as a function of bias-voltage and gate-voltage as well as temperature. By analyzing the features of the RTN, we identify three different types of RTN existing in the SWNT related systems. While the RTN can be generated by the various charge traps in the vicinity of the SWNTs, the RTN for metallic SWNTs is mainly due to reversible defect motions between two metastable states, activated by inelastic scattering with electrons.
Controlling (In,Ga)As quantum structures on high index GaAs surfaces
Authors: Seydmohamadi Sh. , Wen H. , Wang Zh. M. , Salamo G. J.
Published: April 2011

We investigate the formation of (In, Ga) As self assembled quantum structures grown on different orientations of a GaAs substrate along one side of the stereographic triangle between (100) and (111)A surfaces. The samples were grown by Molecular Beam Epitaxy, monitored by Reflection High-Energy Electron Diffraction during the growth and characterized by in-situ Scanning Tunneling Microscopy and Atomic Force Microscopy. A systematic transition from zero dimensional (In, Ga) As quantum dots to one dimensional quantum wires was observed as the substrate was varied along the side of the triangle within 25° miscut from the (100) toward (111)A, which includes several high index surfaces. We propose an explanation for the role of the substrate in determining the type of the nanostructure that is formed.
A Multiscale Model of the Si LPCVD Process
Authors: Rondanini Maurizio , Masi Maurizio , Carrà Sergio , Cavallotti Carlo , Milano Politecnico di
Published: April 2011

The Low Pressure Chemical Vapor Deposition of Si from SiH4 is an industrial process that can be used to deposit epitaxial Si at relatively low surface temperatures. Multiscale models are necessary in order to tune the operating conditions to optimize the quality of the deposited materials. In this work we present a multiscale approach meant to describe the film morphological evolution at different time and length scales. The reactor fluid dynamics and overall mass and temperature balances are solved with the finite element method. The morphological evolution of the film is investigated with 3D kinetic Monte Carlo. We have systematically investigated the dependence of the growth morphology from temperature, pressure and gas phase composition (SiH4/H2 ratio) with the aim of determining the operating parameters window that can lead to the best film morphology. We found that the presence of a significant amount of hydrogen on the surface can significantly influence the surface morphology. In particular hydrogen can be considered as the principal responsible of the transition from an order terrace step flow growth regime, which prevails at high temperatures, to a disordered 3 dimensional growth regime. It is also worth noting that our KMC simulations show that the hydrogen surface chemistry active at low temperatures is probably richer than expected, since the formation of a significant number of island on the surface dramatically increases the concentration of steps, and thus the variety of configurations by which two adsorbed H atoms can interact.
Materials Science and Technology: A curriculum that works
Authors: Stoebe Thomas G. , Rusin John M.
Published: April 2011

Materials Science and Technology is a curriculum developed at Battelle Pacific Northwest National Laboratories, which emphasizes hands-on, minds-on studies of materials science and technology. This curriculum has been taught to over 1000 middle and high school teachers nationwide in a series of week-long institute programs, and is used in classrooms in 16 states. Evaluations have shown that the curriculum is highly effective in getting students interested in science and technology, and in encouraging them to study more science.

This paper presents the basics of the curriculum and its approach, along with venues used for promoting the curriculum and the teaching methods used. Full evaluation results are discussed, including the assessment of increased student interest and increased student involvement their own learning. Means of adapting the program to a local situation are also presented.
Salt: A Tasty Ceramic.
Authors: Peshoff Tracy Lea
Published: April 2011

This paper has described the importance of salt to our modern civilization, and has also discussed the role that salt has played in history. The structure and properties of salt have also been presented. Finally, the production of salt, by solar evaporation, and by underground mining has been described.
Turning Cutting-Edge Research into Secondary Curriculum
Authors: Zenner Greta M. , Crone Wendy C. , Aura Gimm J. , Lux Ken W. , Voyles Paul M. , Abbott Nicholas L. , Cina Anthony P. , Comins Ann Pumper , Tabora Johan , Tuchscherer Pamela , Tuchscherer Tyson , John Whitsett P. , Widstrand Cindy G.
Published: April 2011

Traditional science classroom activities rely on topics and experiments that are distant from the forefront of scientific research. As a result, students view science as stagnant and far removed from real life. Through a National Science Foundation-funded Research Experiences for Teachers (RET) program, we at the University of Wisconsin-Madison (UW) Materials Research Science and Engineering Center (MRSEC) work with secondary teachers to transform cutting-edge research in nanoscale science and engineering into curriculum that is appropriate for middle- and high-school classrooms. This benefits everyone involved: teachers learn about innovative science and the process of research; UW MRSEC personnel learn about science education and the state of today's schools; and students get to test and engage with new curriculum about breakthrough research. This past summer our RET participants conducted research on and developed curriculum about “smart” papers with microencapsulation technology, fuel cells, nano biosensors and liquid crystals, glassy metals, and Wells models.
Research Experiences for Teachers in Materials Science: A Case Study
Authors: Strand Michelle A. , Wignall Steve , Leslie-Pelecky Diandra L.
Published: April 2011

The National Science Education Standards encourage teachers to become involved in research as ‘representatives of science in the classroom’. The Research Experiences for Teachers program affiliated with the Materials Research Science and Engineering Center at the University of Nebraska involves teachers in research on nanoscale magnetic and electronic structures over a summer. Two teachers and a sponsoring researcher share their experiences and what they believe are necessary elements for successful RET experiences.
Materials Education for the 21ST Century Workforce a Report on the 18th Biennial Conference on National Materials Policy, Washington D.C.
Authors: Christou Aris
Published: April 2011

This article presents a summary report of the 18th biennial conference on National Materials Policy, held May 24–25, 2004 at National Academies Keck Center, Washington DC. This conference addressed the educational needs in materials science for the 21st century through a series of presentations which focused on all aspects of materials education including elementary (K-12), undergraduate as well as graduate education and continuing education. The conference therefore contributed to the definition of the educational needs for the 21st century workforce.
A Study of Mechanical Effect of Simulated Fault Movement on Engineered Barrier System
Authors: Nishimura Mayuka , Hirai Takashi , Tanai Kenji , Yui Mikazu
Published: April 2011

The objective of this study is to clarify the mechanical effect on the engineered barrier system (EBS) of a fault movement, presupposed to occur in a high-level radioactive waste repository. The plan of this study is; 1) to understand the mechanical behavior of the buffer material when shearing takes place during experimental tests, and 2) to make progress in numerical analysis techniques in order to estimate the effect of fault movement on the EBS at a disposal site.

Accordingly, the first part of this paper reports tests, which were carried out on a 1:20 model of the EBS. The experimental results indicate that the increased total pressure is due, in part, to the increase of pore water pressure. The second part of this paper reports the results of finite element simulations of the experiments. The calculation results show that the permeability of the near-field rock, which influences the amount of water draining from the buffer material, affects the pressure increase in the buffer material. With appropriately set parameters, the calculation shows agreement with the experimental results.
Waste Package Scenario Modelling
Authors: Watson Sarah P , Hodgkinson David P , Robinson Peter C , Bailey Lucy EF , Poole Mike J
Published: April 2011

UK Nirex has supported a programme of work to develop models describing the postclosure evolution of intermediate-level waste packages with the objectives of:

• providing support and justification for the parameters and representations used in performance assessment models;

• informing future model development and packaging advice.

Scenarios for the potential evolution of a waste package were developed and modelled taking explicit account of waste package heterogeneity and the time-dependence of the physical and chemical characteristics of the system. The modelling work highlighted the treatment of organic complexants and the representation of physical containment as two areas in which the impacts of time dependence and package scale heterogeneity might be particularly significant.

A subsequent study of the impact of organic complexants emphasised the importance of heterogeneity in package inventory in determining the radionuclide release from the near field.

The degree of containment afforded by the wasteform and the waste container has been investigated as part of a study to develop a preliminary understanding of the mixing scales within the repository. The study suggests that the most important control on the release of radionuclides from the waste packages is the integrity of the waste encapsulation grout. Interactions between neighbouring packages are to be expected, but the degree to which homogeneous (well mixed) conditions develop may be limited in both time and space.
Consolidation of Ethanol/Bentonite Slurry Injected in a Planar Fracture; Mathematical Modelling and Experiment
Authors: Takase Hiroyasu , Iwasa Kengo , Ishii Takashi , Ueda Hiroyoshi , Sakabe Yasushi , Ishiguro Katsuhiko
Published: April 2011

Ethanol/bentonite slurry is an alternative to the conventional cement-based material that may cause chemical disturbances to the host rock and the buffer material. In this study we carried out an experiment in which the ethanol/bentonite slurry was injected into a planar synthetic fracture at a constant rate. The pressure build-up due to the increase in viscosity of the bentonite ethanol slurry was observed and, eventually, consolidation of the slurry led to termination of the injection. A mathematical model was also developed to simulate the advection, dispersion and matrix dispersion of ethanol that contributed to the increase in viscosity of the ethanol/bentonite slurry, together with a Stoke's flow of the slurry before consolidation. Furthermore, applicability of the ethanol/bentonite slurry as a grouting material in a range of geological settings is discussed based on the result of a case study using the same model.
Impact of iron released from steel components on the performance of the bentonite buffer: a preliminary assessment within the framework of the KBS-3H disposal concept
Authors: Wersin Paul , Johnson Lawrence H. , Snellman Margit
Published: April 2011

Steel components in the engineered barrier of HLW repositories have a potential to react with the clay buffer and induce adverse effects on its properties. These effects have been assessed within the KBS-3H disposal concept, which includes spent fuel in copper canisters surrounded by bentonite blocks and a steel supercontainer (SC), placed within tunnels in deep crystalline Olkiluoto-type host rock. Based on literature review and thermodynamic modeling, the SC is predicted to completely corrode within a minimum of a few thousand years. The resulting corrosion products are expected to be magnetite, and depending on groundwater compositions, also iron sulfide and perhaps siderite. Furthermore corrosion-derived Fe(II) may react with the clay to form non-swelling phyllosilicates, such as berthierine. From simple mass balance estimates and by applying a more realistic reactive transport model, it can be deduced, that the effect of iron from the SC on the integrity of the bentonite buffer is limited. However, large uncertainties in adequately quantifying this effect pertain due to limited process knowledge on Fe-bentonite interactions.
CORALUS: An Integrated In Situ Corrosion Test on α-Active HLW Glass
Authors: Valcke Elie , Smets Steven , Labat Serge , Lemmens Karel , Iseghem Pierre Van , Thomas Peter , Godon Nicole , Jollivet Patrick , Parisot Géraldine , Mestre Jean-Pierre , Jockwer Norbert , Wieczorek Klaus , Pozo Claudine
Published: April 2011

Integrated in situ corrosion tests with α-doped SON68 glass samples have been and are still being performed in the HADES underground laboratory in Mol, Belgium. Two test tubes have been dismantled, and the glass and clay samples have been analysed (mass loss, SEM, EDS, SIMS,…). The results on glass corrosion largely respond to the expectations and agree very well with results from surface laboratory tests and modelling predictions. The glass alteration is about two orders of magnitude higher at 90 °C than at 30 °C. The addition of powdered glass frit to a Ca-bentonite backfill reduces the glass alteration by two orders of magnitude in comparison with another backfill, dried Boom Clay. The α-doped glass samples were shown to have slightly thicker alteration layers. The thickness seemed to increase with increasing αβγ-activity. Because of the lack of sufficient data on mass loss, we cannot conclude that also the degree of alteration is higher for these samples. Under the thermal gradient in the test tubes, the reaction of Cabentonite with the glass samples and the powdered glass frit dispersed within the bentonite results in the neo-formation of non-swelling 7 Å minerals.
Studies on Metal Gluconic Acid Complexes
Authors: Warwick Peter , Evans Nick , Vines Sarah
Published: April 2011

The presence of organic complexants, such as gluconic acid, in an intermediate-level radioactive-waste (ILW) repository may have a detrimental effect on the sorption of radionuclides, by forming organic complexes in solution. In order to assess this, stability constants are required for the complexes formed with radionuclides at high pH. This study reports the stability constants for the reactions of some divalent metals with gluconic acid (Gl). The metals studied were Cd, Co, Fe(II), and U(VI) at pH 13.3; and Co and U(VI) at pH 7. The constants were measured by the Schubert (ion-exchange) or solubility product methods. Stoichiometries of the complexes were also determined. At pH 7 each complex was of the form M1Gl1, with log β values suggestive of salt formation. At high pH, log β values were between 13 and 20. The constants have enabled speciation calculations to be performed showing the effect of gluconic acid on the metal's solubility, with data for Ni included. Solubility is predicted to increase in the presence of Gl from pH 9 to 13.5, suggesting that it may have an impact on radionuclide behaviour. The largest solubility increases are for Cd and Co, the smallest, U(VI).
Creep performance of OFP copper for the overpack of repository canisters
Authors: Auerkari Pertti , Holmström Stefan , Salonen Jorma , Nenonen Pertti
Published: April 2011

To experimentally assess the long term creep performance of oxygen-free phosphorus- doped (OFP) copper for the overpack of repository canisters, the combination of modestly elevated temperature and multi-axial stress state has been applied for accelerated testing. Multi-axiality was induced by using notched compact tension (CT) specimens, with interrupted testing to periodically inspect for creep damage. Uniaxial creep testing was also conducted to support creep analysis of the CT specimens. After about 10000 h of testing at 150°C/46 MPa (reference stress), the inspected CT specimens showed only marginal creep cavity indications near the notch tip. However, a distinct grain boundary zone with elevated Pcontent was observed to appear and widen during testing, mainly near the notch tip. The significance of the grain boundary zone is not well understood, but indicates stress-enhanced microstructural changes at relatively low temperatures. The predicted isothermal uniaxial creep life at 150°C/46 MPa agreed satisfactorily within a factor of two in time, when obtained independently from converted multi-axial testing results and directly from a creep model based on the available uniaxial data. Although the uncertainties in extended extrapolation remain large, the prediction would suggest safe long term service at leastagainst pure creep failure of intact parent material.
Development of a rapid screening test for SCC susceptibility of copper in disposal vault conditions
Authors: Betova Iva G. , Bojinov Martin S. , Heinonen Jussi , Kinnunen Petri , Lilja Christina , Saario Timo
Published: April 2011

Stress corrosion cracking is a potential failure mechanism of the copper canister proposed to be the main corrosion barrier in the Scandinavian design of the final nuclear waste disposal vault. The main target in SCC-oriented research is to determine the limiting values for the critical concentration of harmful species, the potential range in which these species cause SCC and the threshold stress level required for SCC. The present paper attempts to redefine the criteria for SCC susceptibility of copper in acetate solutions through analysis of potentiodynamic curves using both rotating disc and thin plate electrodes insulated on one side. A potential range in which the current densities at a slow sweep rate are lower than those at a fast sweep rate exists for Cu in 0.001 M - 0.1 M acetate. However, the values of the current densities within this range are significantly smaller than those postulated for active anodic dissolution, implying dissolution mediated by a surface film. New criteria for the SCC susceptibility of pure copper in acetate solutions have been formulated through Stern-Geary analysis of the polarisation curves. Several electrochemical characteristics, such as the current density at the positive crossover potential, the ratio between the corrosion current densities determined from the slow and fast sweeps, as well as the anodic current density in a fast sweep show a clear jump for concentrations between 0.01 M and 0.05 M. This, however, cannot yet be considered as an indication of SCC susceptibility at higher acetate concentrations, as evidenced by complementary SSRT tests.
Direct alpha-recoil as a process to generate U-234/U-238 disequilibrium in groundwater
Authors: Rasilainen Kari , Nordman Henrik , Suksi Juhani , Marcos Nuria
Published: April 2011

We discuss quantitatively the capability of direct α-recoil to create observable radioactive disequilibrium (U-234/U-238 activity ratio > 1) in flowing groundwater. Coupled equations for radioactive decay chain are formulated for the solid U source and for the corresponding groundwater receiving the recoiling U-234 atoms. U-rich fracture coating material and the water flowing in the fracture are discussed in detail.

The novel modelling approach worked well and provides a useful tool for more detailed site-specific studies with more detailed input data. The approach appears feasible because the equations are based on straightforward mass balance considerations.

α-recoil -induced enrichment of U-234 in groundwater is a slow process: the increase of U-234/U-238 activity ratio to notable values above unity will take hundreds to thousands of years. Strong groundwater flow prevents any local recoil-induced U-234 enrichment in the water.
Bituminised Waste Re-treatment: Replacement of the Bitumen Matrix by a Glass Matrix
Authors: Impens Nathalie R.E.N. , Tennstedt Isabelle M. , Lemmens Karel , Gielen Ben , Laer Jo M.P. Van , Fonteyne Alfons F. , Vos Liliane , Vos Ben , Leenaers Ann J.G. , Berghe Sven Van den , Bree Peter J.P. Van , Oost Guido Van
Published: April 2011

The vitrification of nuclear waste salts similar to the salts present in Eurobitum produced by the former Eurochemic reprocessing plant, Mol-Dessel, Belgium, is investigated. In order to approach the composition of the high-level waste reference glass SON68, mixtures with different ratios of glass frit to waste salts have been prepared and vitrified. The concentration of the waste salts varied between 17 and 25 % by weight.

To compare the short term corrosion behaviour with reference waste glass, leach tests have been performed. During 8 weeks, the glass samples were submitted to leach tests at 363 K using Milli Q water as leachant, at a glass exposed area over leachant volume ratio equal to 100 m−1.

During this short period, scanning electron microscopy with energy dispersive X-ray analysis (SEM-EDX) showed no gel layer formation. This technique did not detect changes in the chemical composition. However, X-ray photoelectron spectroscopy (XPS) showed that the binding energy of the Zr 3d and Si 2p electrons decreased as a function of leaching time, indicating an increasing covalent character of the glass surface. Inductively coupled plasma-mass spectrometry (ICP-MS) of the leachate as a function of time shows that ionic species such as Na and K leach faster than e.g. Si and B. These results together with the XPS data suggest the onset of a gel layer formation. The effect of waste content in the glass on the leaching rate is also studied. The results are compared with similar leaching tests on R7T7 type SON68 glass. Most elements are better retained in the simulated Eurobitum glass than in the SON68 glass.
Immobilization of Simulant ILW Actinide Wastes Containing Halides: Effect of Process Parameters on Wasteform Properties
Authors: Metcalfe Brian L. , Fong Shirley K. , Donald Ian W.
Published: April 2011

The applicability of a process, originally developed to immobilize a chloride-rich intermediate level waste (ILW) arising from the pyrochemical reprocessing of plutonium, to alternative ILW waste-streams containing a large variety of cations, present as oxides together with KCl and CaF2, has been investigated. Non-radioactive studies, using simulated wastes containing hafnium and samarium as surrogates for the actinides, have been performed to establish the optimum processing parameters for the manufacture of wasteforms suitable for long-term storage/disposal. It has been demonstrated that the wastes can be immobilized by calcining with either Ca3(PO4)2 or CaHPO4 as the host. In excess of 97.5 % of the chloride present in calcined wastes, containing up to 3.2 wt% halides as a mixture of F- and Cl-, is immobilized when using this process. Whereas in the original calcined waste, the Cl- (about 12 wt%) was immobilized as chlorapatite, Ca5(PO4)3Cl, and spodiosite, Ca2(PO4)Cl, in these current wastes fluorapatite is the predominant halide containing phase. Conversion of the immobilized waste powder into a monolithic wasteform was achieved by sintering the powder with the addition of a sodium aluminium phosphate based glass. Both the calcined powder and the sintered monolithic wasteforms showed excellent durability in aqueous solution.
39-years Performance of Cemented Radioactive Waste in a Mound Type Repository
Authors: Sobolev Igor A. , Dmitriev Sergey A. , Barinov Alexander S. , Varlakova Galina A. , Golubeva Zoya I. , Startceva Irene V. , Ojovan Michael I.
Published: April 2011

Long-term field tests of cemented aqueous radioactive wastes in an experimental mound type surface repository were carried out at Moscow Scientific and Industrial Association “Radon” from 1965 to 2004. Aqueous radioactive wastes of different compositions containing short-lived radionuclides including 90Sr and 137Cs at concentrations from 0.34 to 1.8 MBq/L were immobilized using cementation technology. Water solution to cement ratio was 0.66, grout mixing time 10-15 minutes, and cement paste hardening time 7 days. 73 cement blocks with a volume of 0.027 m3 were disposed of for long-term tests in a simple mound type surface repository. The atmospheric precipitates, which contacted radioactive cement blocks, were collected and analyzed for the content of radionuclides. In August 2004 the experimental repository was opened, cemented blocks, underlying and covering materials were retrieved for analyses. XRD analyses showed that along with amorphous tobermorite gel the main crystal phases in cements are calcite and portlandite. Both visual inspection and radiometric analyses demonstrate that cemented blocks are in good condition and that the cement paste has retained radionuclides from the wastes. Thus after 39 years of storage in the mound type repository the cemented aqueous wastes are reliable immobilized.
The Boom Clay geochemistry: Natural evidence
Authors: De Craen M.
Published: April 2011

In Belgium, the Boom Clay is studied as the reference formation for geological disposal of high-level radioactive waste and spent fuel. As the Boom Clay is considered as the main barrier for radionuclide migration/retention, a thorough characterisation of the clay and its pore water was done. This facilitates better understanding of the long-term geological processes and the distribution of the trace elements and radionuclides.

From a mineralogical/geochemical point of view, the Boom Clay is considered as a rather homogeneous sediment, vertically as well as laterally. It is composed of detrital minerals, organic matter and fossils. Minerals are mainly clay minerals, quartz and feldspars. Minor amounts of pyrite and carbonates are also present. Small variations in mineralogical/geochemical composition are related to granulometrical variations. The radiochemical study indicates that the Boom Clay is in a state of secular radioactive equilibrium, meaning that the Boom Clay has not been disturbed for a very long time.

Pore water sampling is done in situ from various piezometers, or by the squeezing or leaching of clay cores in the laboratory. These three pore water sampling techniques have been compared and evaluated. Boom Clay pore water is a NaHCO3 solution of 15 mM, containing 115 mg·1−1 of dissolved natural organic carbon. Some slight variations in pore water composition have been observed and can be explained by principles of chemical equilibrium.
Porous Alumina-Silica (Gubka) as a Matrix for REE-TUE Strip Solution Immobilization
Authors: Aloy A.S. , Kol'tsova T.I. , Sapozhnikova N.V. , Strelnikov A.V.
Published: April 2011

The immobilisation of strip product (TUE + REE), collected at Russian research centers and laboratories during R&D on partitioning technology for liquid high–level radioactive waste (HLW), was studied using simulated solutions.

Ultraporous glass crystalline material “Gubka”(G) and multiple processing stages were used to immobilize the simulated strip product. The processing consisted of the following stages: Gubka saturation by solution – drying into Gubka pores – compaction by cold uniaxial pressing followed by sintering (CUPS) or hot uniaxial pressing (HUP).
Leach Resistant Cesium and Strontium-bearing Wasteforms from Hexagonal Tungsten Bronze-Polyacrylonitrile Composite Adsorbers
Authors: Griffith Christopher S. , Luca Vittorio , Sebesta Ferdinand , Yee Patrick , Drabarek Elizabeth
Published: April 2011

Immobilization of adsorbed Cs+ and Sr2+ on a molybdenum-doped, hexagonal tungsten bronze (HTB)-polyacrylonitrile (PAN) composite adsorbent can be achieved by heating in air at temperatures in the range 600 - 1200 °C. Thermal treatment of the parent composite material at 800 – 1000 °C undergoes a ca. 60% reduction in volume and retains its spherical morphology. For materials prepared at 800 – 1200 °C the full complement of Cs+ and the majority of Sr2+ partition into HTB phases (A∼0.16-0.3MO3; A = Cs, Sr, Na; M = Mo,W), along with sodium cations. The presence of high concentrations of Na+ relative to either Cs+ or Sr2+ does not appear to interfere with the formation of the HTB phase. The fraction (f) of Cs+ and Sr2+ leached from the tungstate phase assemblages is better or comparable with cesium hollandite (Cs0.8Ba0.4Ti8O18; f = ca. 8 × 10−5; rate = <1.2 × 10−4 g m−2d−1) and strontium titanate (SrTiO3; f = 3.1 × 10−3; rate = 2.63 × 10−4 g m−2day−1), respectively, using a modified PCT test. Furthermore, where aggressive leaching conditions are employed (0.1M HNO3; 150 °C; 4 days), the tungstate phase assemblages display leach resistance orders of magnitude better than the reference phases (Cs+ - f = ca. 5 × 10−3; rate = ca. 1.4 × 10−3 g m−2day−1; Sr2+ - f = ca. 8 × 10−2; rate = ca. 2.5 × 10−2 g m−2day−1).
Effects of alpha self-irradiation on actinide-doped spent fuel surrogate matrix
Authors: Roudil Danièle , Jégou Christophe , Deschanels Xavier , Peuget Sylvain , Raepsaet Caroline , Gallien Jean-Paul , Broudic Véronique
Published: April 2011

During the initial period after disposal, in which no mass transfer occurs with environmental materials, spent fuel undergoes modifications mainly arising from the effects of α self-irradiation damage. To simulate this aging phenomenon and estimate the consequences on the matrix, an experimental study was carried out in which old UO2 samples doped with short-lived actinides were characterized and analyzed. Changes that occur rapidly at the beginning of the aging process were identified in two lots of actinide-doped samples. Volume and microscopic swelling increased, reaching a maximum relative level of 1.5%. At the same damage level, microscopic swelling remained below 0.9%, suggesting that helium formation and atomic defects have a role in this regard. Similarly, the sample microhardness rapidly increased by up to more than 12%. Characterizing 238PuO2 sources showed at very high integrated and instantaneous doses, irradiation damage and helium accumulation at the grain boundaries resulted in grain decohesion or even powder formation. Helium mobility appeared to be modified by the presence of defects, and local implantation experiments were devised in the CEA's Pierre Süe Laboratory at Saclay to quantify this thermally enhanced diffusion component. The physical condition of the sintered PuO2 pellets after 30 years of storage revealed a purely athermal diffusion mechanism, depending on the sample α activity.
Evolution of the spent nuclear fuel during the confinement phase in repository conditions: Major outcomes of the French research
Authors: Ferry C. , Piron J.P , Poinssot Ch.
Published: April 2011

The effects of the temperature and high radioactivity on the chemical and physical state of the fuel during a confinement phase were evaluated in the framework of the PRECCI program. No significant evolution of the fuel chemistry is expected. The radionuclides mobility due to thermal diffusion can be neglected in the temperature range of disposal and diffusion enhanced by α self-irradiation appears to be limited. Microscopic swelling due to alpha self irradiation cumulated damage corresponds to a low volume increase of about 1%. Macroscopic swelling will depend on the helium behavior in the spent fuel. Literature data and results from the project indicate that helium solubility is low in UO2 and should be reached after a few centuries of cooling for MOX fuels. Although the thermal diffusion of helium is some orders of magnitude faster than the thermal diffusion of xenon, it remains low in the temperature range of disposal. Therefore, the first step of physical damage due to helium production should be the precipitation of He bubbles in grains, causing micro-cracks, which could enhance the He release to the grain boundaries. These processes and their consequences on the stability of grain boundaries still need to be quantified today.
Determination of alpha dose rate profile at the UO2/water interface
Authors: Poulesquen A. , Jégou C. , Peuget S.
Published: April 2011

In this paper, an evaluation of the alpha dose rate profile at the UO2/water interface is presented. The calculation is performed in spherical geometry by considering the position of alpha emitters in the material. Moreover it proceeds to an iterative way. The fuel matrix and water is divided in spherical layers of 0.1 μm of thickness. The alpha emitters have an average energy of 5.3 MeV corresponding to a maximum distance of 13.2 μm in UO2 matrix and 42 μm in water. The direction of emission and the energy deposition, described by the Bragg curve, in the nuclear fuel are also taken into account. It appears that the alpha dose rate strongly decreases towards the calculated maximum penetration depth in water namely 42 μm. The concentrations of oxidising and reducing species are largely higher at the UO2/water interface than in solution. This alpha dose profile is used as input file in a model coupling a radiolysis kinetic model and a diffusion model. This kind of calculation is particular suitable for HTR kernels which have a spherical form of few hundreds microns of diameters (200-500 μm).