THM analysis of a large-scale heating test incorporating material fabric changes

Engineered barriers are basic elements in the design of repositories for the isolation of high‐level radioactive waste. This paper presents the thermo‐hydro‐mechanical (THM) analysis of a clay barrier subjected to heating and hydration. The study focuses on an ongoing large‐scale heating test, at almost full scale, which is being carried out at the CIEMAT laboratory under well‐controlled boundary conditions. The test is intensely instrumented and it has provided the opportunity to study in detail the evolution of the main THM variables over a long period of time. Comprehensive laboratory tests carried out in the context of the FEBEX and NF‐PRO projects have allowed the identification of the model parameters to describe the THM behaviour of the compacted expansive clay. A conventional THM approach that assumes the swelling clay as a single porosity medium has been initially adopted to analyse the evolution of the test. The model was able to predict correctly the global THM behaviour of the clay barrier in the short term (i.e. for times shorter than three years), but some model limitations were detected concerning the prediction of the long‐term hydration rate. An additional analysis of the test has been carried out using a double structure model to describe the actual behaviour of expansive clays. The double structure model explicitly considers the two dominant pore levels that actually exist in the FEBEX bentonite and it is able to account for the evolution of the material fabric. The simulation of the experiment using this enhanced model provides a more satisfactory reproduction of the long‐term experimental results. It also contributes to a better understanding of the observed test behaviour and it provides a physically based explanation for the very slow hydration of the barrier.&nbsp

Effect of thermo-coupled processes on the behaviour of a clay barrier submitted to heating and hydration

The storage of high level radioactive waste is still an unresolved problem of the nuclear industry, being geological disposal the most favoured option and, naturally, the one requiring the strongest geo-mechanical input. Most conceptual designs for the deep geological disposal of nuclear waste envisage placing the canisters containing the waste in horizontal drifts or vertical boreholes. The empty space surrounding the canisters is filled by an engineered barrier often made up of compacted swelling clay. In the barrier and the near field, significant thermo-hydro-mechanical (THM) phenomena take place that interact in a complex way. A good understanding of THM issues is, therefore, necessary to ensure a correct performance of engineered barriers and seals. The conditions of the bentonite in an engineered barrier for high-level radioactive waste disposal are being simulated in a mock-up heating test at almost scale, at the premises of CIEMAT in Madrid. The evolution of the main Thermo-Hydro-Mechanical (THM) variables of this test are analysed in this paper by using a fully coupled THM formulation and the corresponding finite element code. Special emphasis has been placed on the study of the effect of thermo-osmotic flow in the hydration of the clay barrier at an advanced staged of the experimen

Thermal-hydraulic-mechanical (THM) behaviour of a large-scale in situ heating experiment during cooling and dismantling

A geological disposal facility for high-level radioactive waste (HLW) encompasses both natural (host rock) and (generally clay-based) engineered barriers. Many processes can influence, either positively or negatively, the effectiveness of the safety functions of isolation and retardation. This paper focuses on the analysis of a large-scale heating test when subjected to cooling and subsequent partial dismantling. The experiment reproduces the conditions of an HLW repository at full scale under realistic conditions. Key thermal, hydraulic, and mechanical (THM) variables, such as temperature, relative humidity, stresses, and fluid pressures, were measured in the clay barrier and surrounding rock. The experimental observations recorded during the cooling down and clay barrier excavation are analyzed in light of a fully coupled THM finite element formulation. This analysis has provided the opportunity to explore the behaviour of the clay and natural barriers under conditions very relevant for the repository performance but not analyzed previously. Overall, the model predictions are quite satisfactory when compared against experimental observations. Furthermore, model predictions for a period of 20 years, including the transient phase induced by the partial dismantling, are also presented. This additional analysis has allowed a better understanding of the effect of thermal gradient on long-term clay hydration

Murciélagos de la provincia de Córdoba, Argentina: riqueza y distribución

Los objetivos del trabajo fueron identificar vacios en la información distribucional existente referida a los quirópteros de la provincia de Córdoba, para determinar el patrón de riqueza de especies e individualizar las variables que afectan la distribución de cada especie en particular. Se realizaron búsquedas bibliográficas de registros publicados, revisiones de ejemplares depositados en colecciones sistemáticas y relevamientos de localidades puntuales. Con base en los datos distribucionales obtenidos se realizaron modelos predictivos utilizando el programa Maxent. El mapa de riqueza se obtuvo mediante la superposición de 10 mapas individuales de presencia-ausencia, más las celdas de presencia de las cinco especies que no pudieron ser modeladas por presentar menos de cinco registros. Se obtuvieron 204 registros de 15 especies en 191 localidades. La mayor parte de las localidades se concentran en la zona serrana. Las 15 especies registradas fueron citadas para el bosque serrano. Desmodus rotundus, Tadarida brasiliensis y Myotis dinellii presentaron el mayor número de registros. En tres de los 26 departamentos de la provincia de Córdoba (General Roca, Roque Sáenz Peña y Totoral) no se hallaron registros. El rango anual de la temperatura fue la variable más importante para el conjunto de especies, seguida por dos variables topográficas, la pendiente y la elevación. El área serrana de la provincia constituyó la zona de mayor riqueza, con celdas con hasta diez especies.Fil: Castilla, María Cecilia. Universidad Nacional de Cordoba. Facultad de Cs.exactas Fisicas y Naturales. Museo de Zoologia; Argentina;Fil: Torres, Ricardo Marcelo. Universidad Nacional de Cordoba. Facultad de Cs.exactas Fisicas y Naturales; Argentina;Fil: Díaz, María Mónica. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo. Prog.de Investigación de Biodiversidad Argentina; Argentina

Informe sobre expediente N°19-2004-tsc-OSINERGMIN, reclamación de LUZ DEL SUR S.A.A. contra ELECTROPERÚ S.A. sobre los cobros por los retiros en exceso de la energía contratada, destinados al servicio público de electricidad

vinculada a la regulación tarifaria de los excesos de energía contratada cuando dichos excesos estén destinados al Servicio Público de Electricidad. Además, analiza el procedimiento mediante el cual se resuelve la controversia, y la competencia que ostenta el OSINERGMIN para hacerlo. La relevancia del análisis radica en definir los alcances del Servicio Público de Electricidad y la asignación de responsabilidades por su prestación. Además, permite utilizar herramientas e instituciones de otras ramas del derecho, como el derecho constitucional, para determinar el adecuado desarrollo de los procedimientos trilaterales que son conocidos por el OSINERGMIN. Las hipótesis del caso son que (i) se cumplieron las normas del procedimiento, (ii) que los excesos de consumo deben ser pagados con la Tarifa en Barra y (iii) que el OSINERGMIN es competente para conocer y resolver la controversia. Para demostrar la validez o no de las hipótesis, se analizarán y aplicarán instituciones del derecho administrativo (procedimiento trilateral, las medidas cautelares, etc.), regulatorio (regulación tarifaria del mercado eléctrico) y constitucional (aplicación temporal de las normas, orden público, etc.). Los resultados de la investigación demuestran que dos de las tres hipótesis resultan ciertas, toda vez que los actores del procedimiento (empresas y órganos resolutivos) siguieron de manera general las reglas aplicables al procedimiento, y que el OSINERGMIN es competente para conocer y resolver la controversia en razón de que esta versa sobre aspectos regulatorios y normativos, y que la santidad de los contratos no puede aplicarse de manera absoluta en el presente caso. No obstante, se demuestra que la Tarifa en Barra no puede constituir un tope para los retiros en exceso que realicen los distribuidores, sino que está en el ámbito de la libre voluntad de las parte del contrato respectivo

Analysis of unsaturated materials hydration incorporating the effect of thermo-osmotic flow

The geological disposal of a high level radioactive waste relies in a system composed of engineered and geological barriers. The soils and rocks involved in the design of this type of solution are generally initially unsaturated and subject to complex thermal, hydraulic and mechanical (THM) coupled phenomena triggered by the simultaneous heating and hydration of the barrier materials under confined conditions. Mathematical THM formulations are typically used to analyze the behavior and long term performance of the barriers system. These types of formulations generally do not include some coupled processes, for example thermo-osmosis (i.e. the movement of liquid water induced by gradient of temperature), because they are considered not significant when compared against the main or direct processes (e.g., Darcy’s, Fourier’s and Fick’s laws). In this work, the potential effects of thermo-osmotic phenomenon is studied in detail. Typical flow equations are modified to include thermo-osmotic flows and then they are implemented in numerical simulators. Two case studies are analyzed. The first one focuses on a simple and already proposed model to study the behavior of a geological barrier for nuclear waste when subjected to heating and hydration. The other case corresponds to the study of an engineered clay barrier material in the laboratory subjected to hydraulic and thermal gradients similar to the ones expected in real repository conditions. In both cases the analyses with and without thermo-osmotic flows are compared. From these comparisons it is observed that the effect of thermo-osmosis can be quite significant. Thermo-osmotic effects also assisted to explain the apparent low wetting observed in the hydration of a clayey barrier material

Hydromechanical behaviour of a heterogeneous compacted soil: experimental observations and modelling

The paper describes a theoretical and experimental study of the coupled hydromechanical behaviour of a compacted mixture of bentonite powder and bentonite pellets intended as sealing material in underground repositories for nuclear waste. One of the main advantages of the use of powder/pellets mixtures is the reduction of the compaction effort required to achieve the value of average dry density necessary to attain the required swelling potential. However, the heterogeneous fabric of the material requires special approaches in order to describe adequately its behaviour during hydration. A double porosity formulation is presented to account for the presence of two distinct structural levels in the material. Hydraulic equilibrium between the two porosities is not assumed; instead a water exchange term between them is postulated. The formulation is applied to the modelling of a number of one-dimensional swelling pressure tests performed in the CEA (Commisariat à l'Énergie Atomique, France) and CIEMAT (Spain) laboratories. A very satisfactory quantitative description of the experimental observations is obtained that includes a number of complex behaviour features such as size effects and non-monotonic development of swelling pressures. Some microfabric observations using X-ray tomography and mercury intrusion porosimetry lend support to the conceptual approach adopted. The formulation is then applied to the analysis of a long-term large-scale sealing test performed at the Hades underground facility in Belgium, using the same set of hydraulic and mechanical parameters employed in the modelling of the laboratory tests. Although the field observations exhibit a much higher degree of scatter, the basic behaviour of the field sealing test is satisfactorily simulated. A formulation that incorporates basic features of the microfabric of the mixture is thus able to span successfully over a large range of space and time scales

De Novo Generation of Infectious Prions In Vitro Produces a New Disease Phenotype

Prions are the proteinaceous infectious agents responsible for Transmissible Spongiform Encephalopathies. Compelling evidence supports the hypothesis that prions are composed exclusively of a misfolded version of the prion protein (PrPSc) that replicates in the body in the absence of nucleic acids by inducing the misfolding of the cellular prion protein (PrPC). The most common form of human prion disease is sporadic, which appears to have its origin in a low frequency event of spontaneous misfolding to generate the first PrPSc particle that then propagates as in the infectious form of the disease. The main goal of this study was to mimic an early event in the etiology of sporadic disease by attempting de novo generation of infectious PrPSc in vitro. For this purpose we analyzed in detail the possibility of spontaneous generation of PrPSc by the protein misfolding cyclic amplification (PMCA) procedure. Under standard PMCA conditions, and taking precautions to avoid cross-contamination, de novo generation of PrPSc was never observed, supporting the use of the technology for diagnostic applications. However, we report that PMCA can be modified to generate PrPSc in the absence of pre-existing PrPSc in different animal species at a low and variable rate. De novo generated PrPSc was infectious when inoculated into wild type hamsters, producing a new disease phenotype with unique clinical, neuropathological and biochemical features. Our results represent additional evidence in support of the prion hypothesis and provide a simple model to study the mechanism of sporadic prion disease. The findings also suggest that prion diversity is not restricted to those currently known, and that likely new forms of infectious protein foldings may be produced, resulting in novel disease phenotypes

Role of estrogen related receptor beta (ESRRB) in DFN35B hearing impairment and dental decay

BACKGROUND: Congenital forms of hearing impairment can be caused by mutations in the estrogen related receptor beta (ESRRB) gene. Our initial linkage studies suggested the ESRRB locus is linked to high caries experience in humans. METHODS: We tested for association between the ESRRB locus and dental caries in 1,731 subjects, if ESRRB was expressed in whole saliva, if ESRRB was associated with the microhardness of the dental enamel, and if ESRRB was expressed during enamel development of mice. RESULTS: Two families with recessive ESRRB mutations and DFNB35 hearing impairment showed more extensive dental destruction by caries. Expression levels of ESRRB in whole saliva samples showed differences depending on sex and dental caries experience. CONCLUSIONS: The common etiology of dental caries and hearing impairment provides a venue to assist in the identification of individuals at risk to either condition and provides options for the development of new caries prevention strategies, if the associated ESRRB genetic variants are correlated with efficacy.Fil: Weber, Megan L.. University of Pittsburgh; Estados UnidosFil: Hsin, Hong Yuan. University of Pittsburgh; Estados UnidosFil: Kalay, Ersan. Karadeniz Technical University; TurquíaFil: Brožková, Dana Š. Charles University; República Checa. University Hospital Motol; República ChecaFil: Shimizu, Takehiko. Nihon University. School of Dentistry; JapónFil: Bayram, Merve. Medipol Istanbul University; TurquíaFil: Deeley, Kathleen. University of Pittsburgh; Estados UnidosFil: Küchler, Erika C.. University of Pittsburgh; Estados UnidosFil: Forella, Jessalyn. University of Pittsburgh; Estados UnidosFil: Ruff, Timothy D.. University of Pittsburgh; Estados UnidosFil: Trombetta, Vanessa M.. University of Pittsburgh; Estados UnidosFil: Sencak, Regina C.. University of Pittsburgh; Estados UnidosFil: Hummel, Michael. University of Pittsburgh; Estados UnidosFil: Briseño Ruiz, Jessica. University of Pittsburgh; Estados UnidosFil: Revu, Shankar K.. University of Pittsburgh; Estados UnidosFil: Granjeiro, José M.. Universidade Federal Fluminense; BrasilFil: Antunes, Leonardo S.. Universidade Federal Fluminense; BrasilFil: Antunes, Livia A.. Universidade Federal Fluminense; BrasilFil: Abreu, Fernanda V.. Universidade Federal Fluminense; BrasilFil: Costabel, Marcelo C.. Universidade Federal do Rio de Janeiro; BrasilFil: Tannure, Patricia N.. Veiga de Almeida University; Brasil. Salgado de Oliveira University; BrasilFil: Koruyucu, Mine. Istanbul University; TurquíaFil: Patir, Asli. Medipol Istanbul University; TurquíaFil: Poletta, Fernando Adrián. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. CEMIC-CONICET. Centro de Educaciones Médicas e Investigaciones Clínicas ; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Mereb, Juan C.. Estudio Colaborativo Latino Americano de Malformaciones Congénitas; ArgentinaFil: Castilla, Eduardo Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. CEMIC-CONICET. Centro de Educaciones Médicas e Investigaciones Clínicas ; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Orioli, Iêda M.. Universidade Federal do Rio de Janeiro; BrasilFil: Marazita, Mary L.. University of Pittsburgh; Estados UnidosFil: Ouyang, Hongjiao. University of Pittsburgh; Estados UnidosFil: Jayaraman, Thottala. University of Pittsburgh; Estados UnidosFil: Seymen, Figen. Istanbul University; TurquíaFil: Vieira, Alexandre R.. University of Pittsburgh; Estados Unido

Ground State Magnetization of Polymerized Spin Chains

We investigate the ground state magnetization plateaus appearing in spin 1/2 polymerized Heisenberg chains under external magnetic fields. The associated fractional quantization scenario and the exponents which characterize the opening of gapful excitations are analyzed by means of abelian bosonization methods. Our conclusions are fully supported by the extrapolated results obtained from Lanczos diagonalizations of finite systems.Comment: 5 pages, 6 figures, final version to appear in Phys.Rev.