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

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

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

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

Los contratos sobre el buque en Derecho Español. Análisis práctico

Prólogo / José Luis Gabaldón García (pp. 9-13). -- Introducción (pp. 15-18). -- El contrato de construcción naval: aspectos prácticos / Gonzalo Alvar Ezquerra (pp. 19-37). -- El contrato de compraventa / Carlos López-Quiroga, Luz Martínez de Azcoitia y José Sánchez-Fayos Martín-Peña (pp. 39-58). -- El contrato de arrendamiento de buque / Rodolfo González Lebrero (pp. 59-75). -- El contrato de fletamento por tiempo / José María Alcántara González (pp. 77-102). -- El contrato de fletamento por viaje: contenido obligacional / Juan Pablo Rodríguez Delgado (pp. 103-144). -- El contrato de transporte marítimo en régimen de conocimiento de embarque / Javier del Corte (pp. 145-186). -- Los documentos de transporte / Carlos Llorente (pp. 187-205). -- Contratos de utilización del buque para fines distintos del transporte de mercancías / José Manuel G. Pellicer (pp. 207-221). -- El contrato de arrendamiento náutico / León von Ondarza (pp. 223-244). -- El contrato de pasaje marítimo / Hannah de Bustos, Antonio Quirós de Sas y Julio López Quiroga (pp. 245-260). -- Los contratos de gestión naval para la dotación del buque / Bernardo Ruiz Lima (pp. 261-279). -- El contrato de gestión naval / Víctor Mata Garrido (pp. 281-302). -- El contrato de consignación de buques /Jesús Barbadillo Eyzaguirre (pp. 303-323). -- El contrato de manipulación portuaria / Carlos Pérez (pp. 325-338). -- El contrato de practicaje / Alicia Velasco Nates (pp. 339-356). -- Los contratos de mediación en la explotación del buque / Carmen Codes Cid y Martín Prieto Sulleiro (pp. 357-372). -- El contrato de remolque / Ana Sánchez Horneros (pp. 373- 392). -- El contrato de remolque / Jaime de Castro (pp. 393-412). -- El contrato de salvamento / Luis Souto (pp. 413-430). -- El contrato de remoción de restos / Verónica Meana (pp. 431-446). -- El contrato de clasificación del buque / Jaime Rodrigo de Larrucea (pp. 447-463). -- El seguro de casco y máquina / Carlos Cerdá Donat y Diego de San Simón Palacios (pp. 465-491). -- Los clubes de protección e indemnización (P&I) / Miguel Caballero (pp. 493-504). -- El seguro de protección e indemnización (P&I) / Jaime Albors (pp. 505-524). -- El seguro del acreedor hipotecario / Luis F. Gómez de Mariaca Fernández (pp. 525-540)

Hotspots of biogeochemical activity linked to aridity and plant traits across global drylands

14 páginas.- 4 figuras.- 67 referencias.- The online version contains supplementary material available at https://doi.org/10.1038/s41477-024-01670-7Perennial plants create productive and biodiverse hotspots, known as fertile islands, beneath their canopies. These hotspots largely determine the structure and functioning of drylands worldwide. Despite their ubiquity, the factors controlling fertile islands under conditions of contrasting grazing by livestock, the most prevalent land use in drylands, remain virtually unknown. Here we evaluated the relative importance of grazing pressure and herbivore type, climate and plant functional traits on 24 soil physical and chemical attributes that represent proxies of key ecosystem services related to decomposition, soil fertility, and soil and water conservation. To do this, we conducted a standardized global survey of 288 plots at 88 sites in 25 countries worldwide. We show that aridity and plant traits are the major factors associated with the magnitude of plant effects on fertile islands in grazed drylands worldwide. Grazing pressure had little influence on the capacity of plants to support fertile islands. Taller and wider shrubs and grasses supported stronger island effects. Stable and functional soils tended to be linked to species-rich sites with taller plants. Together, our findings dispel the notion that grazing pressure or herbivore type are linked to the formation or intensification of fertile islands in drylands. Rather, our study suggests that changes in aridity, and processes that alter island identity and therefore plant traits, will have marked effects on how perennial plants support and maintain the functioning of drylands in a more arid and grazed world.This research was supported by the European Research Council (ERC grant 647038 (BIODESERT) awarded to F.T.M.) and Generalitat Valenciana (CIDEGENT/2018/041). D.J.E. was supported by the Hermon Slade Foundation (HSF21040). J. Ding was supported by the National Natural Science Foundation of China Project (41991232) and the Fundamental Research Funds for the Central Universities of China. M.D.-B. acknowledges support from TED2021-130908B-C41/AEI/10.13039/501100011033/Unión Europea Next Generation EU/PRTR and the Spanish Ministry of Science and Innovation for the I + D + i project PID2020-115813RA-I00 funded by MCIN/AEI/10.13039/501100011033. O.S. was supported by US National Science Foundation (Grants DEB 1754106, 20-25166), and Y.L.B.-P. by a Marie Sklodowska-Curie Actions Individual Fellowship (MSCA-1018 IF) within the European Program Horizon 2020 (DRYFUN Project 656035). K.G. and N.B. acknowledge support from the German Federal Ministry of Education and Research (BMBF) SPACES projects OPTIMASS (FKZ: 01LL1302A) and ORYCS (FKZ: FKZ01LL1804A). B.B. was supported by the Taylor Family-Asia Foundation Endowed Chair in Ecology and Conservation Biology, and M. Bowker by funding from the School of Forestry, Northern Arizona University. C.B. acknowledges funding from the National Natural Science Foundation of China (41971131). D.B. acknowledges support from the Hungarian Research, Development and Innovation Office (NKFI KKP 144096), and A. Fajardo support from ANID PIA/BASAL FB 210006 and the Millennium Science Initiative Program NCN2021-050. M.F. and H.E. received funding from Ferdowsi University of Mashhad (grant 39843). A.N. and M.K. acknowledge support from FCT (CEECIND/02453/2018/CP1534/CT0001, SFRH/BD/130274/2017, PTDC/ASP-SIL/7743/2020, UIDB/00329/2020), EEA (10/CALL#5), AdaptForGrazing (PRR-C05-i03-I-000035) and LTsER Montado platform (LTER_EU_PT_001) grants. O.V. acknowledges support from the Hungarian Research, Development and Innovation Office (NKFI KKP 144096). L.W. was supported by the US National Science Foundation (EAR 1554894). Y.Z. and X.Z. were supported by the National Natural Science Foundation of China (U2003214). H.S. is supported by a María Zambrano fellowship funded by the Ministry of Universities and European Union-Next Generation plan. The use of any trade, firm or product names does not imply endorsement by any agency, institution or government. Finally, we thank the many people who assisted with field work and the landowners, corporations and national bodies that allowed us access to their land.Peer reviewe