Statistical Analyses of Pore Pressure Signals in Claystone During Excavation Works at the Mont Terri Underground Research Laboratory

In many countries (such as Belgium, Germany, France, Japan, Switzerland, and United Kingdom), deep argillaceous formations are considered as potential host rocks for geological disposal of high-level and intermediate-level long-lived radioactive wastes. Some of these countries are investigating the suitability of high compacted clay-rich rocks at depths down to around 500 m below the ground surface. The general disposal concept comprises a network of drifts and tunnels linked to the surface by shafts and ramps, all artificially ventilated. Research is ongoing in Underground Research Laboratories, like the Mont Terri site in the Swiss Jura, to assess and ensure the safety of the repositories for the full decay life of the radioactive waste, i.e. the capacity of the hypothetical repository toprevent the migration of radionuclides towards the biosphere.[...

Analysis and Modeling of Coupled Thermo-Hydro-Mechanical Phenomena in 3D Fractured Media

Ce mémoire présente un travail de thèse conduite en cotutelle France-Espagne dans le cadre d'une convention entre l'Institut National Polytechnique de Toulouse (INPT) et l'Université Polytechnique de Madrid (UPM). Il porte sur un problème d'intérêt commun au niveau national et international, le stockage de déchets radioactifs en milieux géologiques profonds. Le mémoire est consacré plus particulièrement aux aspects hydrogéologiques et aux transferts de masse et de chaleur en champ proche. Dans une première partie, on s'intéresse à un problème particulier d'interprétation de données (pressions, humidités relatives, températures) dans une expérience de systèmes multi-barrières à l'échelle de quelques mètres - le « Test Mock-up » du projet FEBEX réalisé en Espagne. Des techniques d'analyse statistique spatiale, temporelle et de fréquence / échelle sont appliquées à plus de 500 chroniques de données. On analyse le déroulement et le couplage des phénomènes physiques qui ont eu lieu lors de l'expérience, et on tire des conclusions sur le comportement et la fiabilité des capteurs. La seconde partie de la thèse développe plus en détail la modélisation des phénomènes Thermo-Hydro-Mécaniques 3-Dimensionnels (3D) dans une roche poreuse fracturée, cette fois-ci à l'échelle de la centaine de mètres, en s'appuyant sur les données du « Test In-Situ » du projet FEBEX, réalisé au Grimsel Test Site dans les Alpes Suisses. En première étape, une reconstruction 3D du réseau de fractures est réalisée par simulation de Monte-Carlo en tenant compte, par optimisation, des données géomorphologiques collectées autour de la galerie FEBEX. La distribution hétérogène de traces observée sur la paroi cylindrique de la galerie est assez bien reproduite dans le réseau simulé. Dans une seconde étape, on développe une méthode pour estimer la perméabilité équivalente d'un bloc multi-fracturé en généralisant la méthode de superposition de Ababou et al. [1994] au cas où la perméabilité matricielle est non négligeable (celle-ci peut représenter non seulement l'espace poral mais aussi une fracturation fine). Avec la perméabilité matricielle, il devient envisageable d'éviter les corrections empiriques basées sur la connectivité, qui sont employées dans la littérature pour tenir compte des effets de non-percolation. L'approche « superposition » est également appliquée ici au problème couplé hydro-mécanique afin d'obtenir les coefficients équivalents du milieu fracturé 3D, qui comprennent (outre le tenseur de perméabilité) les coefficients tensoriels de raideur ou de complaisance élastique, et des coefficients de couplage pression-déformation (Biot). Finalement, à partir de ces résultats, on réalise un modèle hermo-hydro-mécanique couplé en milieu continu équivalent 3D, comprenant : des couplages hydro-mécaniques par les équations tensorielles de Biot (non orthotrope), un flux darcien dans le milieu poreux équivalent (perméabilité anisotrope), ainsi que des contraintes thermiques et du transport de chaleur par diffusion et convection tenant compte de l'expansivité thermique du fluide. Des simulations transitoires de l'excavation de la galerie FEBEX et du réchauffement provoqué par l'éventuel stockage de colis de déchets radioactifs sont conduites à l'aide du logiciel numérique Comsol Multiphysics ® (éléments finis 3D). Les résultats de simulation sont analysés dans différents cas et pour différents types de sollicitations. Enfin, les premières comparaisons des simulations numériques avec les chroniques de données provenant du « Test In-Situ » FEBEX donnent des résultats encourageants. ABSTRACT : This doctoral research was conducted as part of a joint France-Spain « cotutelle » PhD thesis in the framework of a bilateral agreement between two universities, the Institut National Polytechnique de Toulouse (INPT) and the Universidad Politecnica de Madrid (UPM). It concerns a problem of common interest at the national and international levels, namely, the disposal of radioactive waste in deep geological repositories. The present work is devoted, more precisely, to near-field hydrogeological aspects involving mass and heat transport phenomena. The first part of the work is devoted to a specific data interpretation problem (pressures, relative humidities, temperatures) in a multi-barrier experimental system at the scale of a few meters – the “Mock-Up Test” of the FEBEX project, conducted in Spain. Over 500 time series are characterized in terms of spatial, temporal, and/or frequency/scale-based statistical analysis techniques. The time evolution and coupling of physical phenomena during the experiment are analyzed, and conclusions are drawn concerning the behavior and reliability of the sensors. The second part of the thesis develops in more detail the 3-Dimensional (3D) modeling of coupled Thermo-Hydro-Mechanical phenomena in a fractured porous rock, this time at the scale of a hundred meters, based on the data of the “In-Situ Test” of the FEBEX project conducted at the Grimsel Test Site in the Swiss Alps. As a first step, a reconstruction of the 3D fracture network is obtained by Monte Carlo simulation, taking into account through optimization the geomorphological data collected around the FEBEX gallery. The heterogeneous distribution of traces observed on the cylindrical wall of the tunnel is fairly well reproduced in the simulated network. In a second step, we develop a method to estimate the equivalent permeability of a many-fractured block by extending the superposition method of Ababou et al. [1994] to the case where the permeability of the rock matrix is not negligible (matrix permeability may embody some finer fracturing in addition to pore space). When fracture flow is complemented by significant matrix permeability, it may be possible to avoid empirical connectivity-based corrections, which are used in the literature to account for non-percolation effects. The superposition approach is also applied here to coupled Hydro-Mecanical problems to obtain the equivalent coefficients of the 3D fractured medium, including the permeability tensor, but also elastic stiffness or compliance coefficients, as well as pressure-strain coupling coefficients (Biot). Finally, these results are used to develop a continuum equivalent model for 3D couple Thermo-Hydro-Mechanics, including: hydro-mechanical coupling via tensorial Biot equations (non-orthotropic), a darcian flow in an equivalent porous medium (anisotropic permeability), as well as thermal stresses and heat transport by diffusion and convection, taking into account the thermal expansivity of water. Transient simulations of the excavation of the FEBEX gallery, and of the heating due to hypothetical radioactive waste canisters, are conducted using the Comsol Multiphysics ® software (3D finite elements). The results of numerical simulations are analyzed for different cases and different ways of stressing the system. Finally, preliminary comparisons of simulations with time series data collected during the “In-Situ Test” of FEBEX yield encouraging result

Radioactive Waste

The safe management of nuclear and radioactive wastes is a subject that has recently received considerable recognition due to the huge volume of accumulative wastes and the increased public awareness of the hazards of these wastes. This book aims to cover the practice and research efforts that are currently conducted to deal with the technical difficulties in different radioactive waste management activities and to introduce to the non-technical factors that can affect the management practice. The collective contribution of esteem international experts has covered the science and technology of different management activities. The authors have introduced to the management system, illustrate how old management practices and radioactive accident can affect the environment and summarize the knowledge gained from current management practice and results of research efforts for using some innovative technologies in both pre-disposal and disposal activities

Detection Of Periodic Error And Structure Change Using Wavelet Analysis

Heterodyne displacement measuring interferometry provides important metrology for applications requiring high resolution and accuracy. Heterodyne Michelson interferometers use a two-frequency laser source and separate the two optical frequencies into one fixed length and one variable length path via polarization. Ideally these two beams are linearly polarized and orthogonal so that only one frequency is directed toward each path. An interference signal is obtained by recombining the light from the two paths; this results in a measurement signal at the heterodyne (split) frequency of the laser source. This measurement signal is compared to the optical reference signal. Motion in the measurement arm causes a Doppler shift of the heterodyne frequency which is measured as a continuous phase shift that is proportional to displacement. In practice, due to component imperfections, undesirable frequency mixing occurs which yields periodic errors. Ultimately, this error can limit the accuracy to approximately the nanometer level. Periodic error is typically quantified using a Fourier transform-based analysis of constant velocity motions. However, non-constant velocity profiles lead to non-stationary signals that require alternate analysis techniques for real-time compensation. A new discrete time continuous wavelet transform (DTCWT)-based algorithm has been developed, which can be implemented in real time to quantify and compensate periodic error for constant velocity motion in heterodyne interferometer. The objective of this study is to extend the application of this algorithm to compensate non-stationary periodic error. In non-constant velocity motion, the frequency of periodic error varies with the velocity of the target. Also, the periodic error amplitude may fluctuate due to the use of a fiber-coupled laser source. The algorithm is also applied into the situation where higher order periodic error occurs. To validate the effectiveness of the novel wavelet-based algorithm in practice, the algorithm is implemented on the hardware and operated in real-time. The wavelet analysis is generalized and extended to a method of structural health monitoring (SHM). Currently, there are nearly 70,000 t of used nuclear fuel in spent fuel pools or dry cask storage increasing by nearly 2,000 t per year. After being used in a reactor, this fuel is stored for 3 to 5 years in spent fuel pools. Eventually the spent fuel will be placed into dry cask storage for another 20 years to more than 100 years. From the spent fuel pool, used fuel rod assemblies are loaded into casks underwater. This water must be removed to avoid corrosion or potential creation of combustion gases burning subsequent storage. During the drying process, if this operation is rapid, the water retained in the failed rods is likely to form ice. In this case, the ice crystal is difficult to remove. Moreover, if the ice forms at some critical location on the water flow path (e.g., a fretting on a fuel rod), it will prevent removal of the remaining water inside the rod. The objective of this research is to develop an integrated wavelet-based approach for structural health monitoring in dry cask storage based on concepts developed in the periodic error compensation. The key conditions (defect location, ice formation, etc.) of failed fuel rods in dry cask storage are monitored to acquire any possible structure change in real-time. The relationship between different conditions and wavelet transform results is investigated. Simulations and experiments are used to validate this approach. A wavelet-based approach can be used to effectively do SHM and periodic error compensation

NASA SBIR abstracts of 1991 phase 1 projects

The objectives of 301 projects placed under contract by the Small Business Innovation Research (SBIR) program of the National Aeronautics and Space Administration (NASA) are described. These projects were selected competitively from among proposals submitted to NASA in response to the 1991 SBIR Program Solicitation. The basic document consists of edited, non-proprietary abstracts of the winning proposals submitted by small businesses. The abstracts are presented under the 15 technical topics within which Phase 1 proposals were solicited. Each project was assigned a sequential identifying number from 001 to 301, in order of its appearance in the body of the report. Appendixes to provide additional information about the SBIR program and permit cross-reference of the 1991 Phase 1 projects by company name, location by state, principal investigator, NASA Field Center responsible for management of each project, and NASA contract number are included

French Roadmap for complex Systems 2008-2009

This second issue of the French Complex Systems Roadmap is the outcome of the Entretiens de Cargese 2008, an interdisciplinary brainstorming session organized over one week in 2008, jointly by RNSC, ISC-PIF and IXXI. It capitalizes on the first roadmap and gathers contributions of more than 70 scientists from major French institutions. The aim of this roadmap is to foster the coordination of the complex systems community on focused topics and questions, as well as to present contributions and challenges in the complex systems sciences and complexity science to the public, political and industrial spheres

30th International Conference on Condition Monitoring and Diagnostic Engineering Management (COMADEM 2017)

Proceedings of COMADEM 201

ReSCon '12, Research Student Conference: Book of Abstracts

The fifth SED Research Student Conference (ReSCon2012) was hosted over three days, 18-20 June 2012, in the Hamilton Centre at Brunel University. The conference consisted of 130 oral and 70 poster presentations, based on the high quality and diverse research being conducted within the School of Engineering and Design by postgraduate research students. The conference is held annually, and ReSCon plays a key role in contributing to research and innovations within the School

ReSCon '09, Research Student Conference: Book of Abstracts

The second SED Research Student Conference (ReSCon2009) was hosted over three days, 22-24 June 2009, in the Lecture Centre at Brunel University. The conference consisted of technical presentations, a poster session and social events. The abstracts and presentations were the result of ongoing research by postgraduate research students from the School of Engineering and Design at Brunel University. The conference is held annually, and ReSCon plays a key role in contributing to research and innovations within the School