Aplicación de la metodología ISA al análisis de la secuencia de pérdida del sistema de agua de refrigeración de componentes en una central nuclear con reactor de agua a presión

La metodología Integrated Safety Analysis (ISA), desarrollada en el área de Modelación y Simulación (MOSI) del Consejo de Seguridad Nuclear (CSN), es un método de Análisis Integrado de Seguridad que está siendo evaluado y analizado mediante diversas aplicaciones impulsadas por el CSN; el análisis integrado de seguridad, combina las técnicas evolucionadas de los análisis de seguridad al uso: deterministas y probabilistas. Se considera adecuado para sustentar la Regulación Informada por el Riesgo (RIR), actual enfoque dado a la seguridad nuclear y que está siendo desarrollado y aplicado en todo el mundo. En este contexto se enmarcan, los proyectos Safety Margin Action Plan (SMAP) y Safety Margin Assessment Application (SM2A), impulsados por el Comité para la Seguridad de las Instalaciones Nucleares (CSNI) de la Agencia de la Energía Nuclear (NEA) de la Organización para la Cooperación y el Desarrollo Económicos (OCDE) en el desarrollo del enfoque adecuado para el uso de las metodologías integradas en la evaluación del cambio en los márgenes de seguridad debidos a cambios en las condiciones de las centrales nucleares. El comité constituye un foro para el intercambio de información técnica y de colaboración entre las organizaciones miembro, que aportan sus propias ideas en investigación, desarrollo e ingeniería. La propuesta del CSN es la aplicación de la metodología ISA, especialmente adecuada para el análisis según el enfoque desarrollado en el proyecto SMAP que pretende obtener los valores best-estimate con incertidumbre de las variables de seguridad que son comparadas con los límites de seguridad, para obtener la frecuencia con la que éstos límites son superados. La ventaja que ofrece la ISA es que permite el análisis selectivo y discreto de los rangos de los parámetros inciertos que tienen mayor influencia en la superación de los límites de seguridad, o frecuencia de excedencia del límite, permitiendo así evaluar los cambios producidos por variaciones en el diseño u operación de la central que serían imperceptibles o complicados de cuantificar con otro tipo de metodologías. La ISA se engloba dentro de las metodologías de APS dinámico discreto que utilizan la generación de árboles de sucesos dinámicos (DET) y se basa en la Theory of Stimulated Dynamics (TSD), teoría de fiabilidad dinámica simplificada que permite la cuantificación del riesgo de cada una de las secuencias. Con la ISA se modelan y simulan todas las interacciones relevantes en una central: diseño, condiciones de operación, mantenimiento, actuaciones de los operadores, eventos estocásticos, etc. Por ello requiere la integración de códigos de: simulación termohidráulica y procedimientos de operación; delineación de árboles de sucesos; cuantificación de árboles de fallos y sucesos; tratamiento de incertidumbres e integración del riesgo. La tesis contiene la aplicación de la metodología ISA al análisis integrado del suceso iniciador de la pérdida del sistema de refrigeración de componentes (CCWS) que genera secuencias de pérdida de refrigerante del reactor a través de los sellos de las bombas principales del circuito de refrigerante del reactor (SLOCA). Se utiliza para probar el cambio en los márgenes, con respecto al límite de la máxima temperatura de pico de vaina (1477 K), que sería posible en virtud de un potencial aumento de potencia del 10 % en el reactor de agua a presión de la C.N. Zion. El trabajo realizado para la consecución de la tesis, fruto de la colaboración de la Escuela Técnica Superior de Ingenieros de Minas y Energía y la empresa de soluciones tecnológicas Ekergy Software S.L. (NFQ Solutions) con el área MOSI del CSN, ha sido la base para la contribución del CSN en el ejercicio SM2A. Este ejercicio ha sido utilizado como evaluación del desarrollo de algunas de las ideas, sugerencias, y los algoritmos detrás de la metodología ISA. Como resultado se ha obtenido un ligero aumento de la frecuencia de excedencia del daño (DEF) provocado por el aumento de potencia. Este resultado demuestra la viabilidad de la metodología ISA para obtener medidas de las variaciones en los márgenes de seguridad que han sido provocadas por modificaciones en la planta. También se ha mostrado que es especialmente adecuada en escenarios donde los eventos estocásticos o las actuaciones de recuperación o mitigación de los operadores pueden tener un papel relevante en el riesgo. Los resultados obtenidos no tienen validez más allá de la de mostrar la viabilidad de la metodología ISA. La central nuclear en la que se aplica el estudio está clausurada y la información relativa a sus análisis de seguridad es deficiente, por lo que han sido necesarias asunciones sin comprobación o aproximaciones basadas en estudios genéricos o de otras plantas. Se han establecido tres fases en el proceso de análisis: primero, obtención del árbol de sucesos dinámico de referencia; segundo, análisis de incertidumbres y obtención de los dominios de daño; y tercero, cuantificación del riesgo. Se han mostrado diversas aplicaciones de la metodología y ventajas que presenta frente al APS clásico. También se ha contribuido al desarrollo del prototipo de herramienta para la aplicación de la metodología ISA (SCAIS). ABSTRACT The Integrated Safety Analysis methodology (ISA), developed by the Consejo de Seguridad Nuclear (CSN), is being assessed in various applications encouraged by CSN. An Integrated Safety Analysis merges the evolved techniques of the usually applied safety analysis methodologies; deterministic and probabilistic. It is considered as a suitable tool for assessing risk in a Risk Informed Regulation framework, the approach under development that is being adopted on Nuclear Safety around the world. In this policy framework, the projects Safety Margin Action Plan (SMAP) and Safety Margin Assessment Application (SM2A), set up by the Committee on the Safety of Nuclear Installations (CSNI) of the Nuclear Energy Agency within the Organization for Economic Co-operation and Development (OECD), were aimed to obtain a methodology and its application for the integration of risk and safety margins in the assessment of the changes to the overall safety as a result of changes in the nuclear plant condition. The committee provides a forum for the exchange of technical information and cooperation among member organizations which contribute their respective approaches in research, development and engineering. The ISA methodology, proposed by CSN, specially fits with the SMAP approach that aims at obtaining Best Estimate Plus Uncertainty values of the safety variables to be compared with the safety limits. This makes it possible to obtain the exceedance frequencies of the safety limit. The ISA has the advantage over other methods of allowing the specific and discrete evaluation of the most influential uncertain parameters in the limit exceedance frequency. In this way the changes due to design or operation variation, imperceptibles or complicated to by quantified by other methods, are correctly evaluated. The ISA methodology is one of the discrete methodologies of the Dynamic PSA framework that uses the generation of dynamic event trees (DET). It is based on the Theory of Stimulated Dynamics (TSD), a simplified version of the theory of Probabilistic Dynamics that allows the risk quantification. The ISA models and simulates all the important interactions in a Nuclear Power Plant; design, operating conditions, maintenance, human actuations, stochastic events, etc. In order to that, it requires the integration of codes to obtain: Thermohydraulic and human actuations; Even trees delineation; Fault Trees and Event Trees quantification; Uncertainty analysis and risk assessment. This written dissertation narrates the application of the ISA methodology to the initiating event of the Loss of the Component Cooling System (CCWS) generating sequences of loss of reactor coolant through the seals of the reactor coolant pump (SLOCA). It is used to test the change in margins with respect to the maximum clad temperature limit (1477 K) that would be possible under a potential 10 % power up-rate effected in the pressurized water reactor of Zion NPP. The work done to achieve the thesis, fruit of the collaborative agreement of the School of Mining and Energy Engineering and the company of technological solutions Ekergy Software S.L. (NFQ Solutions) with de specialized modeling and simulation branch of the CSN, has been the basis for the contribution of the CSN in the exercise SM2A. This exercise has been used as an assessment of the development of some of the ideas, suggestions, and algorithms behind the ISA methodology. It has been obtained a slight increase in the Damage Exceedance Frequency (DEF) caused by the power up-rate. This result shows that ISA methodology allows quantifying the safety margin change when design modifications are performed in a NPP and is specially suitable for scenarios where stochastic events or human responses have an important role to prevent or mitigate the accidental consequences and the total risk. The results do not have any validity out of showing the viability of the methodology ISA. Zion NPP was retired and information of its safety analysis is scarce, so assumptions without verification or approximations based on generic studies have been required. Three phases are established in the analysis process: first, obtaining the reference dynamic event tree; second, uncertainty analysis and obtaining the damage domains; third, risk quantification. There have been shown various applications of the methodology and advantages over the classical PSA. It has also contributed to the development of the prototype tool for the implementation of the ISA methodology (SCAIS).

Desarrollo de una aplicación móvil para organizar eventos entre grupos

Día a día surge la necesidad de tener que organizar actividades entre varias personas donde es necesaria la presencia de una toma de decisiones conjunta. La tarea de coordinar y poner de acuerdo a todas las partes implicadas resulta realmente complicada, y encontrar la solución que mejor se adapte a todos los participantes es uno de los principales problemas a los que hay que enfrentarse. Dentro de este contexto surge la idea de “DealtDay”, una aplicación pensada para organizar de forma sencilla e intuitiva a un grupo de personas a la hora de realizar cualquier actividad, como puede ser el establecimiento de una fecha para una reunión, elegir el restaurante dónde cenar o qué película ver. DealtDay es una aplicación desarrollada para Android, iOS y navegadores web. La elección de estas tecnologías se debe a que permiten que la aplicación sea accesible a los usuarios desde los dispositivos tecnológicos más utilizados cotidianamente (ordenador, tabletas y móviles). El funcionamiento de esta aplicación en los distintos sistemas desarrollados es posible gracias al desarrollo de una API REST que permite la comunicación entre cualquier tipo de aplicación con un servidor mediante peticiones realizadas con el protocolo HTTP. ABSTRACT Day after day it appears the necessity of organizating activities among different people where taking decisions together becomes fundamental. The task of coordinating and creating an agreement among all the parts involved, turns to be really difficult and, as a matter of fact, one of the main problems to cope with is finding a solution which fits to all the participants. In this context appears the idea of DealtDay, an application conceived to organize a group of people in an easy and intuitive way when doing any kind of activity, such as deciding a date for a meeting, choosing a restaurant, a place to have dinner or a film to be watched. DealtDay is an application developed for Android, iOS and web navigators. The selection of these technologies is due to the fact that they allows the application accessibility to users from the most used and common technological devices (personal computers, tablets and mobiles). The functioning of the application is possible thanks to an API REST development that allows the communication between any kind of application and a server through requests made by the HTTP protocol.

Implantación de técnicas de QA en un proyecto de desarrollo software

Hoy en día existe una preocupación creciente por la calidad del software entregado en los proyectos que se realizan a lo largo del mundo. El trabajo de fin de grado que va a ser desarrollado en estas páginas pretende demostrar la importancia de la realización de tests funcionales durante el proceso de desarrollo de software para que el proyecto alcance la calidad requerida tan demandada en estos días. Para ello, después de una pequeña introducción a la historia del software, se presentarán y compararán diversos tipos de metodologías de desarrollo de software, tanto pesadas (cascada, espiral, etc.) como ágiles (Extreme Programming y Scrum), se enfatizará en dichas metodologías ágiles y cómo el proceso de testing y control de calidad encaja perfectamente con la filosofía de las citadas metodologías ágiles. Se desarrollará una explicación del papel de QA en el desarrollo de software, asi como una explicación de los tipos de test existentes, y las herramientas, tecnologías y patrones que existen a disposición de aquellos que quieran desempeñar el papel de QA. Para complementar el punto de vista teórico de este trabajo se presentará un caso práctico real realizado en la empresa bq bajo una metodología Scrum. Dicho caso práctico muestra el uso de ciertas herramientas y su aporte para el control de calidad del proyecto bajo desarrollo, demostrando su importancia. Se realizará énfasis en el proceso de automatización de ciertas baterías de test (llamadas test suites), mostrando desde el planteamiento inicial de las diferentes historias de usuario y la batería de test, pasando por la elección de las tecnologías más adecuadas para la elaboración de los test hasta llegar al lanzamiento de dicha batería de pruebas y la comprobación de éstas. El punto de vista práctico quedará complementado por una explicación del framework nightwatch.js, framework utilizado en el desarrollo del proyecto en bq para la automatización de test funcionales. Esta explicación comprenderá tanto la configuración y uso del framework como el uso de patrones y la estructura de las pruebas. ABSTRACT Nowadays there is a growing concern about the Quality of the software delivered in the projects that are made all around the world. This final project will try to prove the importance of performing functional tests during the Software Development Process in order to be able to reach the demanded Quality. To fulfill this objective, different types of Software Development methodologies will be presented and compared. Heavy methodologies (waterfall, spiral methodologies, etc.) as well as agile methodologies (Extreme Programming and Scrum). There will be an emphasis in the second kind (agile methodologies) and how the testing and quality assurance process fits perfectly in their philosophy. A deep explanation of the role that Quality Assurance holds on software development will be presented, as well as an explanation on the current types of testing and an explanation of the different tools; technologies and patrons that exist to help anyone who wants to perform the role of QA. To complement the theoretical perspective of this work a real case study, performed at the company bq under a Scrum methodology, will be presented. The mentioned study covers the use of certain tools and their input for the quality assurance of the project under development, proving its relevance. Emphasis will be made in the process of conducting a set of tests (called test suite), showing from the initial approach of the different users stories and the set of tests, going through the choosing of the most suitable technologies for the tests development, and ending with the performance of this battery of tests and their checkout. The practical point of view will be complemented by a deep explanation of the creation process using the nightwatch.js automated test framework, used in the project in bq. This explanation will cover both the configuration and use of the framework as the use of patterns and structure of the tests.

Determination of a refractive index and an extinction coefficient of standard production of CVD-graphene

The refractive index and extinction coefficient of chemical vapour deposition grown graphene are determined by ellipsometry analysis. Graphene films were grown on copper substrates and transferred as both monolayers and bilayers onto SiO2/Si substrates by using standard manufacturing procedures. The chemical nature and thickness of residual debris formed after the transfer process were elucidated using photoelectron spectroscopy. The real layered structure so deduced has been used instead of the nominal one as the input in the ellipsometry analysis of monolayer and bilayer graphene, transferred onto both native and thermal silicon oxide. The effect of these contamination layers on the optical properties of the stacked structure is noticeable both in the visible and the ultraviolet spectral regions, thus masking the graphene optical response. Finally, the use of heat treatment under a nitrogen atmosphere of the graphene-based stacked structures, as a method to reduce the water content of the sample, and its effect on the optical response of both graphene and the residual debris layer are presented. The Lorentz-Drude model proposed for the optical response of graphene fits fairly well the experimental ellipsometric data for all the analysed graphene-based stacked structures.

Comparing the Luttinger–Kohn–Pikus–Bir and the Empiric K·P Hamiltonians in quantum dot intermediate band solar cells manufactured in zincblende semiconductors

The calculation of the energy spectrum and absorption coefficients of quantum dot nanostructured intermediate band solar cells using the Empiric K·P Hamiltonian method and its agreement with experimental data are summarized. The well established Luttinger Kohn Hamiltonian modified by Pikus and Bir for strained material, such as quantum dot arrays, is presented using a simplified strain field that allows for square band offsets. The energy spectrum and absorption coefficients are calculated with this new Hamiltonian. With the approximations made the energy spectrum results to be exactly the same but the absorption coefficient fits experiments less accurately. The computer time using the latter Hamiltonian is much longer than the former one.

Organizational determinants of substantive sustainability reporting practices: the role of company-level fit

As sustainability reporting (SR) practices have being increasingly adopted by corporations over the last twenty years, most of the existing literature on SR has stressed the role of external determinants (such as institutional and stakeholder pressures) in explaining this uptake. However, given that recent evidence points to a broader range of motives and uses (both external and internal) of SR, we contend that its role within company-level activities deserves greater academic attention. In order to address this research gap, this paper seeks to provide a more detailed examination of the organizational characteristics acting as drivers and/or barriers of SR integration within corporate sustainability practices at the company-level. More specifically, we suggest that substantive SR implementation can be predicted by assessing the level of fit between the organization and the SR framework being adopted. Building on this hypothesis, our theoretical model defines three forms of fit (technical, cultural and political) and identifies organizational characteristics associated to each of these fits. Finally, implications for academic research, businesses and policy-makers are derived.

Symbolic vs substantive sustainability reporting: examining the role of company-level characteristics

As sustainability reporting (SR) practices have being increasingly adopted by corporations over the last twenty years, most of the existing literature on SR has stressed the role of external determinants (such as institutional and stakeholder pressures) in explaining this uptake. However, given that recent evidence points to a broader range of motives and uses (both external and internal) of SR, we contend that its role within company-level activities deserves greater academic attention. In order to address this research gap, this paper seeks to provide a more integrated perspective of both institutional and efficiency explanations of SR dynamics, as well as to highlight the role of company-level characteristics in explaining its contribution to sustainability management practices. More specifically, we suggest that substantive SR implementation can be predicted by assessing the level of fit between the organization and the SR framework being adopted. Building on this idea, our theoretical model defines three forms of fit (technical, cultural and political) and identifies organizational characteristics associated to each of these fits. Finally, implications for academic research, businesses and policy-makers are derived.

Written on the threshold

One of the most productive discoveries of art and architectural criticism is the comparative reading between different situations. It is an approach that does away with all conventions and destroys any attempt to codifing the future. It also reveals the futility of established styles or movements. In the early 20th century, the Russian Formalists spoke of the dissimilarity of the similar in literature and more than a few studies on the visual arts have used the comparative method, from Heinrich Wolfflin to Robert Venturi. But something more has to be added, personal biography. The involvement of the individual, their name and their life, in the history of art bursts in with all the force of what is real, with no need for credibility, because it merely is what it is. The histories of architecture and art tell things in a believable, perfectly connected manner, without the fits and starts of personal biography - when this appears we find ourselves in a different sort of situation.