Development of an Analytic Nodal Diffusion Solver in Multigroups for 3D Reactor Cores with Rectangular or Hexagonal Assemblies.

More accurate modelling of physical phenomena involved in present and future nuclear reactors requires a multi-scale and multi-physics approach. This challenge can be accomplished by the coupling of best-estimate core-physics, thermal-hydraulics and multi-physics solvers. In order to make viable that coupling, the current trends in reactor simulations are along the development of a new generation of tools based on user-friendly, modular, easily linkable, faster and more accurate codes to be integrated in common platforms. These premises are in the origin of the NURESIM Integrated Project within the 6th European Framework Program, which is envisaged to provide the initial step towards a Common European Standard Software Platform for nuclear reactors simulations. In the frame of this project and to reach the above-mentioned goals, a 3-D multigroup nodal solver for neutron diffusion calculations called ANDES (Analytic Nodal Diffusion Equation Solver) has been developed and tested in-depth in this Thesis. ANDES solves the steady-state and time-dependent neutron diffusion equation in threedimensions and any number of energy groups, utilizing the Analytic Coarse-Mesh Finite-Difference (ACMFD) scheme to yield the nodal coupling equations. It can be applied to both Cartesian and triangular-Z geometries, so that simulations of LWR as well as VVER, HTR and fast reactors can be performed. The solver has been implemented in a fully encapsulated way, enabling it as a module to be readily integrated in other codes and platforms. In fact, it can be used either as a stand-alone nodal code or as a solver to accelerate the convergence of whole core pin-by-pin code systems. Verification of performance has shown that ANDES is a code with high order definition for whole core realistic nodal simulations. In this paper, the methodology developed and involved in ANDES is presented

Public television faced with the challenges of digital convergence: perceptions of audience and TVE professionals

En un momento de crisis del Estado del Bienestar y de cuestionamiento de la televisión pública en una industria de la comunicación marcada por una intensa competitividad, la profunda mutación que está experimentando el ecosistema mediático con el avance de la digitalización invita a preguntarse por el papel que juegan los servicios públicos de televisión ante una audiencia interactiva redefinida como “prosumidora”.Ongizatearen estatua krisian dagoela eta, lehiakortasun gogo batek markatutako komunikazioindustriaren barruan, telebista publikoa zalantzan jartzen ari dela, digitalizazioaren garapenarekin komunikabideen ekosisteman izaten ari den aldaketa sakona dela eta, galdetu beharra dago zer betekizun duten telebistaren zerbitzu publikoek ikus-entzule interaktiboen aurrean (ikus-entzule horiei orain “prosumitzaile” esaten zaie).À une époque de crise de l’État-providence et de remise en cause de la télévision publique dans une industrie de la communication marquée par une forte compétitivité, la mutation profonde que connaît l’écosystème médiatique avec les progrès de la numérisation invite à s’interroger sur le rôle que jouent les services publics de télévision face à une audience interactive redéfinie comme « prosommatrice »

Transient analysis in the 3D nodal kinetics and thermal-hydraulics ANDES/COBRA coupled system

Neutron kinetics has been implemented in the 3D nodal solver ANDES, which has been coupled to the core thermal-hydraulics (TH) code COBRA-III for core transient analysis. The purpose of this work is, first, to discuss and test the ability of the kinetics solver ANDES to model transients; and second, by means of a systematic analysis, including alternate kinetics schemes, time step size, nodal size, neutron energy groups and spectrum, to serve as a basis for the development of more accurate and efficient neutronics/thermal-hydraulics tools for general transient simulations. The PWR MOX/UO2 transient benchmark provided by the OECD/NEA and US NRC was selected for these goals. The obtained ANDES/COBRA-III results were consistent with other solutions to the benchmark; the differences in the TH feedback led to slight differences in the core power evolution, whereas very good agreements were found in the other requested parameters. The performed systematic analysis highlighted the optimum kinetics iterative scheme, and showed that neutronics spatial discretization effects have stronger influence than time discretization effects, in the semi-implicit scheme adopted, on the numerical solution. On the other hand, the number of energy groups has an important influence on the transient evolution, whereas the assumption of using the prompt neutron spectrum for delayed neutrons is acceptable as it leads to small relative errors

Teoría de nudos y aplicaciones

El presente trabajo consiste en una breve introducción a la teoría de nudos, con especial hincapié en la teoría de nudos virtuales (una joven rama de este campo con prometedoras perspectivas de futuro que estudia una generalización del concepto de nudo clásico) y su conexión (siendo ésta de carácter topológico) con unos elementos de naturaleza algebraica. La memoria está dividida en tres partes fundamentales: preliminares (apéndice A), códigos de Gauss (capítulo 1) y planaridad (capítulo 2). La lectura debe comenzar con el apéndice A: en éste se expone lo necesario para entender el desarrollo de los capítulos 1 y 2. Se introducen conceptos básicos de teoría de nudos y teoría de nudos virtuales y, debido a la fuerte analogía entre nudos y grafos, también de teoría de grafos. Esta parte presenta una visión general para posicionarse en el contexto de lo estudiado, proporcionando las herramientas para afrontar cuestiones más particulares. En el capítulo 1 entraremos en algo más concreto: la capacidad de unas secuencias de números, letras y signos para representar los nudos virtuales, los llamados códigos de Gauss. Desarrollaremos de forma natural y detallada el proceso para demostrar que estos códigos verdaderamente sirven para representar nudos virtuales y nos familiarizaremos mejor con el entorno sobre el que estamos trabajando. El último y segundo capítulo servirá para demostrar la utilidad de este nuevo enfoque para estudiar los nudos virtuales: el hecho de trabajar con códigos de Gauss nos permitirá obtener nuevos resultados y además, ser capaces de desarrollar algoritmos para el estudio de nudos virtuales. En definitiva, se trata de una breve inmersión en una línea de investigación actual, la teoría de nudos virtuales, mostrando su motivación y (parte de) la utilidad de la misma

Design and Realization of a Novel Optically Disordered Material: A Demonstration of a Mie Glass

Herein, a diffusive material presenting optical disorder is introduced, which represents an example of a Mie glass. Comprising spherical crystalline TiO nanoparticles randomly dispersed in a mesoporous TiO matrix, it is proved that the scattering of light in this inhomogeneous solid can be predicted in an unprecedented manner from single-particle considerations employing Mie theory. To that aim, a study of the dependence of the key parameters employed is performed to describe light propagation in random media, i.e., the scattering mean free path and the transport mean free path, as a function of the size and concentration of the spherical inclusions based on a comparison between experimental results and analytical calculations. It is also demonstrated that Mie glasses enable enhanced fluorescence intensity due to a combined absorptance enhancement of the excitation light combined with an improved outcoupling of the emitted light. The method offers the possibility to perform a deterministic design for the realization of a light diffuser with tailor-made scattering properties.European Union 307081Ministerio de Economía y Competitividad MAT2014-54852-

Critical appraisal of the systematic review and meta-analysis of intra-articular ozone therapy efficiency to attenuate pain in knee osteoarthritis

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Oxigenoterapia y cuidados paliativos en pacientes con insuficiencia cardiaca. Respuesta

Letter to the Edito

The analytic nodal diffusion solver ANDES in multigroups for 3D rectangular geometry: Development and performance analysis

In this work we address the development and implementation of the analytic coarse-mesh finite-difference (ACMFD) method in a nodal neutron diffusion solver called ANDES. The first version of the solver is implemented in any number of neutron energy groups, and in 3D Cartesian geometries; thus it mainly addresses PWR and BWR core simulations. The details about the generalization to multigroups and 3D, as well as the implementation of the method are given. The transverse integration procedure is the scheme chosen to extend the ACMFD formulation to multidimensional problems. The role of the transverse leakage treatment in the accuracy of the nodal solutions is analyzed in detail: the involved assumptions, the limitations of the method in terms of nodal width, the alternative approaches to implement the transverse leakage terms in nodal methods – implicit or explicit _, and the error assessment due to transverse integration. A new approach for solving the control rod ‘‘cusping” problem, based on the direct application of the ACMFD method, is also developed and implemented in ANDES. The solver architecture turns ANDES into an user-friendly, modular and easily linkable tool, as required to be integrated into common software platforms for multi-scale and multi-physics simulations. ANDES can be used either as a stand-alone nodal code or as a solver to accelerate the convergence of whole core pin-by-pin code systems. The verification and performance of the solver are demonstrated using both proof-of-principle test cases and well-referenced international benchmarks

Extension of the analytic nodal diffusion solver ANDES to triangular-Z geometry and coupling with COBRA-IIIc for hexagonal core analysis.

In this paper the extension of the multigroup nodal diffusion code ANDES, based on the Analytic Coarse Mesh Finite Difference (ACMFD) method, from Cartesian to hexagonal geometry is presented, as well as its coupling with the thermal–hydraulic (TH) code COBRA-IIIc for hexagonal core analysis. In extending the ACMFD method to hexagonal assemblies, triangular-Z nodes are used. In the radial plane, a direct transverse integration procedure is applied along the three directions that are orthogonal to the triangle interfaces. The triangular nodalization avoids the singularities, that appear when applying transverse integration to hexagonal nodes, and allows the advantage of the mesh subdivision capabilities implicit within that geometry. As for the thermal–hydraulics, the extension of the coupling scheme to hexagonal geometry has been performed with the capability to model the core using either assembly-wise channels (hexagonal mesh) or a higher refinement with six channels per fuel assembly (triangular mesh). Achieving this level of TH mesh refinement with COBRA-IIIc code provides a better estimation of the in-core 3D flow distribution, improving the TH core modelling. The neutronics and thermal–hydraulics coupled code, ANDES/COBRA-IIIc, previously verified in Cartesian geometry core analysis, can also be applied now to full three-dimensional VVER core problems, as well as to other thermal and fast hexagonal core designs. Verification results are provided, corresponding to the different cases of the OECD/NEA-NSC VVER-1000 Coolant Transient Benchmarks

Análisis molecular de las poblaciones de la especie invasora Rhynchophorus ferrugineus Olivier, 1790 (Coleoptera: Curculionidae) en la Región de Murcia (España)

In this research two fragments of the cytochrome c oxidase subunit I (COX1) gene of the mitochondrial DNA were analyzed in 61 individuals of the genus Rhynchophorus collected in the Region of Murcia with the aim of determining their origin. Phylogenetic analysis of fragment 1 of the samples collected in the Region of Murcia together with the available sequences in GenBank, indicated that these individuals correspond to the species Rhynchophorus ferrugineus. Sequences from Murcia collapsed into the H8 Mediterranean haplotype, which cluster into the R. ferrugineus clade. Phylogeographic analysis shows that the origin of the individuals collected in the Region of Murcia is Egypt. Additionally, a contiguous fragment of COX1 (fragment 2) was analyzed and the sequences collapsed into two haplotypes.En este estudio se analizan dos fragmentos del gen de la citocromo c oxidasa subunidad I (COX1) del ADN mitocondrial de 61 individuos del género Rhynchophorus colectados en la Región de Murcia a fin de determinar su procedencia. El análisis filogenético del fragmento 1 de las muestras de la Región de Murcia conjuntamente con las secuencias disponibles en GenBank indica que los individuos corresponden a la especie Rhynchophorus ferrugineus. Las secuencias de Murcia se colapsan en un único haplotipo (H8 mediterráneo) que aparece dentro del clado de R. ferrugineus. De los análisis filogeográficos se infiere que el origen de los individuos de Murcia es Egipto. Adicionalmente, se examinó una región contigua del COX1 (fragmento 2) en la que las secuencias se colapsaron en dos haplotipos