Effectiveness of the ASVAD valve in a reactor vessel bottom leak scenario

Decay heat removal can be seriously degraded by the presence of non-condensable gases in the cooling circuits. Nitrogen gas may be pushed into the primary system after a full discharge of the accumulators. This may produce various adverse effects: the interruption of natural circulation, the limitation of the primary to secondary heat transfer during the reflux cooling and prevent the startup of the active injection by stabilization of the pressure above the injection set point. State-of-the-art system codes have proven to be capable to simulate non-condensable gas effects in accident situations. The ASVAD valve, has been designed to avoid the inflow of nitrogen into the primary system by means of passive concepts. This paper addresses the complications derived from the nitrogen and evaluates the ASVAD valve performance through the simulation of a vessel bottom leak experiment at the LSTF facility in Japan.Peer ReviewedPostprint (published version

PVST, a tool to assess the power to volume scaling distortions associated to code simulations

System codes along with necessary nodalizations are valuable tools for thermal hydraulic safety analysis. In order to assess the safety of a particular power plant, in addition to the validation and veri cation of the code, the nodalization of the system needs to be quali ed. Since most existing experimental data come from tests performed on scaled-down facilities, any quali cation process must therefore address scale considerations. Along these lines, the Group of Thermal Hydraulic Studies at Technical University of Catalonia (GET) developed SCUP, a scaling-up methodology for qualifying full-scale nodalizations through a systematic procedure based on the extrapolation of post-test simulations of Integral Test Facilities (ITF) experiments. For that purpose, GET created thePostprint (author's final draft

Kv-scaling in thermal hydraulics: Background, applications and forthcoming uses

Addressing the scaling issue refers to a rather complex process of demonstrating the applicability of activities devoted to predict the behaviour of actual nuclear power plants using the knowledge acquired in scaled-down test facilities. Such activities involve, among others, the evaluation of the capability of Best Estimate codes to scale-up processes from reduced scale test facilities to full scale Nuclear Power Plants (NPP) and the quantification of the effects of scale distortions. In this context, a scaled calculation is a system-code simulation in which, defined test conditions of an Integral Test Facility (ITF) are scaled-up to a NPP nodalization to reproduce the same scenario. The practical use of such kind of calculation is to permit a comparison of the behaviour of the plant and the ITF nodalizations under the same conditions. The comparison between the NPP -scaled results and those of the experiment post-test calculation will show unavoidable differences or distortions. Explaining such distortions is the key process in methods devoted to qualify plant nodalizations. The aim of this paper is to show the effectiveness of -scaled calculations and to outline the forthcoming use of hybrid nodalizations and scale-up nodalizations. The paper includes a thorough literature review of these type of approaches as well as the perspectives of future use of the scaling analysis. Such future uses include the feedback to experimentation. Despite the fact that the hybrid calculations presented here are related to existing ITFs and NPPs, feedback to experimentation intents to show the essentials of a future practice to be mainly implemented in modular ITFs.Peer ReviewedPostprint (published version

Applying UPC scaling-up methodology to the LSTF-PKL counterpart test

In the framework of the nodalization qualification process and quality guarantee procedures and following the guidelines of Kv-scaled analysis and UMAE methodology, further development has been performed by UPC team resulting in a scaling-up methodology. Such methodology has been applied in this paper for analyzing discrepancies that appear between the simulations of two counterpart tests. It allows the analysis of scaling-down criterion used for the design of an ITF and also the investigation of the differences of configuration between an ITF and a particular NPP. For analyzing both, it applies two conceptsPostprint (published version

Dinámicas de las concentraciones de empleo en sectores intensivos en conocimiento y su relación con las políticas locales de promoción económica: un estudio para la Provincia de Barcelona

Las economías de aglomeración están transformando el mapa de distribución del empleo en las regiones metropolitanas y están condicionando los cambios en sus estructuras urbanas. Uno de sus más claros efectos es el impacto positivo sobre la productividad de las empresas, que buscan localizarse en un lugar específico como un instrumento competitivo para sus procesos productivos, interactuando así con los procesos de desarrollo del territorio. Estos fenómenos se estudian en la Provincia de Barcelona para el periodo 1991-2001, estudiando los sectores económicos intensivos en conocimiento ―sectores definidos por la OCDE, como Industrias de alta tecnología y servicios de conocimiento alto― por su intrínseca relación con la existencia de economías de aglomeración, además de las industrias textiles, actividad que históricamente ha caracterizado el desarrollo económico de esta región. El estudio se ha desarrollado en dos etapas; en la primera se estudia el proceso de transformación del mercado del empleo en los sectores y el periodo antes definidos, a partir de la información de los lugares de trabajo localizados (LTL) por municipio, de los censos estatales de 1991 y 2001 del Instituto Nacional de Estadística (INE). En la segunda etapa se ha hecho un análisis sobre los factores clave surgidos desde los ámbitos de la planificación pública que han propiciado la consolidación de estos sectores económicos. Es por ello que, mediante entrevistas personales en profundidad a técnicos de desarrollo económico y empresarial de algunos de estos municipios, se han detectado y analizado aquellas políticas, instrumentos y/o medidas que han sido implementadas por iniciativa de las propias entidades municipales y organizaciones supramunicipales, con el objetivo de consolidar dicho proceso. Los resultados sugieren que efectivamente ha habido un avance significativo en el crecimiento de la actividad económica de los sectores estudiados en la Provincia, y que este crecimiento responde en algunos de los casos estudiados a las políticas locales de promoción económica desarrolladas por las administraciones. Esta ponencia se presenta como parte de los resultados obtenidos en el proyecto CAEE The case for agglomeration economies in Europe Targeted Analysis 2013/2/1 del Programa ESPON 2013 de la Unión Europea, y en el que han participado, además de la Universidad Politécnica de Catalunya, la University of Manchester, la National University of Ireland y la Ecole Normale Supérieure Lettres Sciences Humaines, de Lyon.Agglomeration economies are transforming the map of distribution of employment in the metropolitan areas and are affecting the changes in urban structures. One of the clearest effects is the positive impact on productivity of firms that seek to locate in a specific place as a competitive tool for the productive processes, interact with the processes of regional development. These phenomena are studied in the Province of Barcelona for the period 1991-2001, studying the economic sectors in knowledge-intensive sectors defined by the OECD as high-tech industries and high-knowledge services for its intrinsic relation with the existence of economies agglomeration, in addition to the textile industry, an activity that has historically characterized the economic development of this Region. The study was conducted in two stages: the first examines the transformation of the employment market in the sectors and the period defined above, from the information workplace located (LTL) by municipality, the censuses of 1991 and 2001 the National Statistics Institute (INE). In the second stage has been an analysis of key factors arising from the fields of public planning which led to the consolidation of these sectors. That is why, through personal interviews in depth technical and business economic development of some of these municipalities have been detected and analyzed those policies, instruments and / or measures that have been implemented at the initiative of their own supra-municipal entities and organizations with the aim of strengthening this process. The results suggest that there has indeed been significant progress in the growth of economic activity in the sectors studied in the Province, and that this growth response in some of the cases to local economic promotion policies developed by governments. This paper is presented as part of the results obtained in the project CAEE The Case for Agglomeration Economies in Europe Targeted Analysis 2013/2/1 ESPON 2013. Programme of the European Union, and in which participated also Polytechnic University Catalunya, the University of Manchester, National University of Ireland and the Ecole Normale Supérieure Lettres Sciences Humaines, Lyon.Peer Reviewe

Assessment of SBO Fukushima likewise scenario for an IPWR design with RELAP5MOD33 and RELAPSCDAPSIMMOD3. 5 codes

In recent years Small Modular Reactors (SMR) have become very popular within the nuclear industry. These designs allow to reduce costs as well as to enhance the safety due to passive nuclear safety features. Within these systems, the integral Pressurized Water Reactors (iPWR) are very extended because they take advantage of the previous technology developed for Gen II and III PWRs. In this sense, previous Best Estimate system codes like RELAP5 or CATHARE seem to be reliable for Deterministic Safety Assessment (DSA) but need to be assessed for new passive systems in which natural circulation takes a key role. In the present paper, Energy Software Ltd., in collaboration with the UPC, has developed an iPWR input model for both NRC RELAP5 and ISS RELAPSCDAPSIM codes. These models, based on CAREM-25 publicly available data, simulate an SBO Fukushima likewise scenario. Results under Design Basis Accident (DBA) conditions are benchmarked to assess the reliability of the codes to reproduce the plant availability reported in the collected data. Passive systems like Safety Injections and Residual Heat Removal Exchangers have also been included to analyze the code capabilities to reproduce natural circulation under iPWR conditions. Finally, core damage progression is simulated with SCDAP components to analyze the severe accident related phenomena. Results of both simulations seem to confirm the 36 hours grace period for SBO scenario of the CAREM-25 design plus the extended 36 hours grace period associated to the availability of Emergency Injection System (EIS) in Loss of Coolant conditions reported by designer.Peer ReviewedPostprint (published version

Methodology for phenomenological code assessment with integral test data

The use of codes in the licensing process requires a rigorous validation process that can be accomplished by means of qualitative and quantitative assessment. In thermal hydraulics, this validation has to be performed at different levels, from separate effects to the integral response of a plant design. Even though the quantitative assessment is preferred, for complex phenomenology involving the behaviour of the whole plant system this approach is difficult and the assessment is usually performed through qualitative expert judgement. In the present article, a methodology is proposed that combines the use of qualitative and quantitative adequacy assessment for the simulation of experiments at integral test facilities. The method makes use of statistical quantification by means of Best Estimate Plus Uncertainty calculations.Peer ReviewedPostprint (published version

Dinámicas de las concentraciones de empleo en sectores intensivos en conocimiento y su relación con las políticas locales de promoción económica: un estudio para la Provincia de Barcelona

Las economías de aglomeración están transformando el mapa de distribución del empleo en las regiones metropolitanas y están condicionando los cambios en sus estructuras urbanas. Uno de sus más claros efectos es el impacto positivo sobre la productividad de las empresas, que buscan localizarse en un lugar específico como un instrumento competitivo para sus procesos productivos, interactuando así con los procesos de desarrollo del territorio. Estos fenómenos se estudian en la Provincia de Barcelona para el periodo 1991-2001, estudiando los sectores económicos intensivos en conocimiento ―sectores definidos por la OCDE, como Industrias de alta tecnología y servicios de conocimiento alto― por su intrínseca relación con la existencia de economías de aglomeración, además de las industrias textiles, actividad que históricamente ha caracterizado el desarrollo económico de esta región. El estudio se ha desarrollado en dos etapas; en la primera se estudia el proceso de transformación del mercado del empleo en los sectores y el periodo antes definidos, a partir de la información de los lugares de trabajo localizados (LTL) por municipio, de los censos estatales de 1991 y 2001 del Instituto Nacional de Estadística (INE). En la segunda etapa se ha hecho un análisis sobre los factores clave surgidos desde los ámbitos de la planificación pública que han propiciado la consolidación de estos sectores económicos. Es por ello que, mediante entrevistas personales en profundidad a técnicos de desarrollo económico y empresarial de algunos de estos municipios, se han detectado y analizado aquellas políticas, instrumentos y/o medidas que han sido implementadas por iniciativa de las propias entidades municipales y organizaciones supramunicipales, con el objetivo de consolidar dicho proceso. Los resultados sugieren que efectivamente ha habido un avance significativo en el crecimiento de la actividad económica de los sectores estudiados en la Provincia, y que este crecimiento responde en algunos de los casos estudiados a las políticas locales de promoción económica desarrolladas por las administraciones. Esta ponencia se presenta como parte de los resultados obtenidos en el proyecto CAEE The case for agglomeration economies in Europe Targeted Analysis 2013/2/1 del Programa ESPON 2013 de la Unión Europea, y en el que han participado, además de la Universidad Politécnica de Catalunya, la University of Manchester, la National University of Ireland y la Ecole Normale Supérieure Lettres Sciences Humaines, de Lyon.Agglomeration economies are transforming the map of distribution of employment in the metropolitan areas and are affecting the changes in urban structures. One of the clearest effects is the positive impact on productivity of firms that seek to locate in a specific place as a competitive tool for the productive processes, interact with the processes of regional development. These phenomena are studied in the Province of Barcelona for the period 1991-2001, studying the economic sectors in knowledge-intensive sectors defined by the OECD as high-tech industries and high-knowledge services for its intrinsic relation with the existence of economies agglomeration, in addition to the textile industry, an activity that has historically characterized the economic development of this Region. The study was conducted in two stages: the first examines the transformation of the employment market in the sectors and the period defined above, from the information workplace located (LTL) by municipality, the censuses of 1991 and 2001 the National Statistics Institute (INE). In the second stage has been an analysis of key factors arising from the fields of public planning which led to the consolidation of these sectors. That is why, through personal interviews in depth technical and business economic development of some of these municipalities have been detected and analyzed those policies, instruments and / or measures that have been implemented at the initiative of their own supra-municipal entities and organizations with the aim of strengthening this process. The results suggest that there has indeed been significant progress in the growth of economic activity in the sectors studied in the Province, and that this growth response in some of the cases to local economic promotion policies developed by governments. This paper is presented as part of the results obtained in the project CAEE The Case for Agglomeration Economies in Europe Targeted Analysis 2013/2/1 ESPON 2013. Programme of the European Union, and in which participated also Polytechnic University Catalunya, the University of Manchester, National University of Ireland and the Ecole Normale Supérieure Lettres Sciences Humaines, Lyon.Peer Reviewe

OECD/NEA PKL-4 benchmark activity. Code assessment of the relevant phenomena associated to a blind IBLOCA experiment

Code assessment and validation is one of the most relevant research lines in thermal hydraulics and best estimate codes. During the last decades, the Nuclear Energy Agency (NEA) and the Organization for Economic Co-operation and Development (OECD) have sponsored dozens of experimental projects in this field. Most of them were compiled in the CSNI Code Validation Matrix in 1996. Several projects have been promoted in the new century as the SETH, PKL, PKL-2, PKL-3 and PKL-4 at the PKL test facility. In 2017 a benchmark activity was launched within the framework of the OECD/NEA PKL-4 project with the aim of assessing the capabilities of system codes to reproduce the relevant phenomena associated to the IBLOCA scenario. 16 participant organizations from 9 different countries simulated the i2.2 (run 3) experiment in semi-blind conditions. A large variety of system codes were used in the activity: ATHLET, CATHARE, KORSAR, LOCUST, RELAP5, RELAPSCDASIM, SPACE and TRACE. This paper presents the main outcomes for the code assessment of such codes. The first part describes the main features of the experiment and the selection of the key phenomena for code validation. In addition, the paper intoduces a detailed description of each phenomena and the comparison between the experimental data and the blind simulations of the participants. Finally, in the last part of the paper the main sources of uncertainty associated to the codes and the modelling are listed as well as the code assessment conclusions of the benchmark activity. In general, the results obtained by all participants showed a good performance and satisfactory agreement with experimental data, which increases the confidence in current TH code technologies. The overall quality of the contributions was partly a consequence of the excellent documentation and information provided by the PKL team.Peer ReviewedPostprint (published version

Load follow with gen-iv very high temperature gas cooled reactor for the spanish future power mix

The future power mix in Spain and most of the European countries is expected to be dominated by renewable sources. The Spanish government has set a policy to eliminate fossil fuels and nuclear power in the following decades by means of increasing the installed capacity of renewable energy, mainly solar PV and wind. The high penetration of these technologies in the power mix may cause a mismatch between demand and production that can be hardly overcome by the use of batteries or other non-thermal storage systems. Very high temperature Gas cooled reactors (VHTR) are one of the most attractive options of Gen-IV reactors for several reasons including the superior safety, near term deployment and high thermal efficiency. But another important advantage is their possibility of load following thanks to the use of gas turbines and the possibilities for thermal storage. In this publication, an innovative design of the thermal cycle of a VHTR is presented. The thermal circuit configuration is modified to maximize the flexibility of the reactor thanks to a molten salt thermal storage and the inherent flexibility of the use of a gas turbine. In addition, the thermal storage can also be fed by a solar field of mirrors. To demonstrate the adaptability of the power plant, the power generation of Spain in a hypothetical future has been used to represent the variability that should be provided by a power plant needed to support the high penetration rate of renewable power. The power plant showed great capabilities for load following hour by hour with changes from 0 to 100% without the need to change the nuclear thermal power. This type of power plants may support renewable sources while guaranteeing the net zero emissions objective.Peer ReviewedPostprint (published version