Kevin Fernandez-Cosials

Universidad Politécnica de Madrid | UPM

During a severe accident in light water reactor (LWR), hydrogen concentration can overpass the flammability limits locally, so the correct simulation of its behavior during a release is critical. The capability assessment of computational fluid dynamics tools to calculate the hydrogen distribution under different conditions has been the focus of in...

La creatividad suele ser definida comúnmente como “la habilidad de generar ideas o productos que sean novedosos, apropiados y que tengan impacto” . La característica apropiados se refiere a que deben ser ideas o productos útiles, que en caso del arte, se podría intercambiar utilidad por belleza. Por lo tanto, productos novedosos pero no útiles o vi...

Hydrogen management is still one of the main nuclear safety topics because of its violent reaction with oxygen. During a severe accident, hydrogen can be generated and it can be released into the containment atmosphere. To deal with this threat, the severe accident management guidelines must be used. These guidelines include several actions to coup...

Verification and Validation of numerical simulations lies at the foundation of building computational credibility. An attempt has been made in providing an accessible, complete, and practical procedure for this admittedly complicated endeavor, which, nonetheless, is deemed an essential pursuit for those involved in numerical simulations. Despite be...

Anyone clicking on the link before October 16, 2019 will be taken directly to the final version of the article on ScienceDirect, no fees are required. https://authors.elsevier.com/a/1ZdqA3OQ~fPN4h The Best Estimate Plus Uncertainty (BEPU) approach is being used worldwide for nuclear power plants licensing. This method relies on the use of best est...

Heat pipe micro reactors are compact, innovative nuclear reactors that utilize heat pipe technology to manage heat transfer efficiently. The advantage of heat pipe micro reactors lies in their reduced complexity, high efficiency, and ability to provide stable power in various scenarios where traditional, larger reactors are not feasible or practica...

This document explores the role of CFD in nuclear safety studies, with a particular focus on advancements in Spain and Portugal. The field of nuclear safety has increasingly included CFD models to address complex safety–critical phenomena, given their ability to capture three-dimensional behavior with high resolution. While traditional one-dimensio...

Best-Estimate Plus Uncertainty (BEPU) nuclear safety analysis is an approach widely used in the field of nuclear engineering and reactor safety assessment. It aims to provide a more realistic assessment of reactor safety by considering a combination of best-estimate models and the quantification of the uncertainty of the input and code data. The Sp...

VVER are one of the most common reactor types in the world. Moreover, a significant percentage of the Gen-III/Gen III+ reactors that are currently being built or have recently come into operation are VVER. Therefore, there is a growing interest in studying their behavior under both anticipated and accidental transients. A joint effort between the U...

Heat pipe micro reactors are drawing a lot of interest lately due to their distinct features, including the elimination of moving parts required for transferring the heat, as they do so passively through heat pipes, combined with the ability of such reactors to provide energy to remote locations. This present study introduces a proposed design for...

Hydrogen is a flammable gas that can generate thermal and mechanical loads which could jeopardise the containment integrity upon combustion inside nuclear power plants containment. Hydrogen can be generated from various sources and disperses into the containment atmosphere, mixing with steam and air following a loss of coolant accident and its prog...

MELCOR is an integral code developed by Sandia National Laboratories (SNL) for the US Nuclear Regulatory Commission (USNRC) to perform severe accident analyses of Light Water Reactors (LWR). More recently, MELCOR capabilities are being extended also to analyze non-LWR fission technologies. Within the European MELCOR User Group (EMUG), organized in...

The airfoil-fin, Printed Circuit Heat eXchanger (PCHX) has been considered a key candidate for nuclear energy, Concentrated Solar Power (CSP), and several power conversion cycle applications, using different heat transfer fluids like molten salts, supercritical 𝐶𝑂2, and helium gas among others. In this study, differential pressure and flow rate mea...

The current trends in development and installation of solar and wind energy poses certain challenges over the stability of the future electricity grids. New regulations or energy storage systems will be essential to enable this large renewable penetration. In the present paper, a zero-emissions scenario composed solely of nuclear energy and renewa...

One of the main goals of severe accident management strategies is to maintain containment integrity to prevent radioactive release into the environment. As a result, containment internal loads need to be investigated during a postulated accident. In the present study, short-term containment thermal-hydraulic (TH) parameters of a VVER-1000/V446 reac...

The specific configuration of safety systems of VVER-1000/V320 reactors allows a comprehensive study of the Loss of Coolant Accident (LOCA). In the present paper, a verification of the success criteria of the event trees headers for the Medium and Large Break LOCA sequences is conducted. A detailed TRACEV5P5 thermal-hydraulic model of the reactor h...

The Mining of Space Resources starts to exit the science fiction circles and enter the field of patents, academic discussions and even private investors. In this sense, the School of Mines of the Technical University of Madrid has decided to follow the lead of other universities such as the School of Mining of Colorado (USA) and provide a program o...

The Instrumentation performance during a Severe Accident (SA) is currently one of the key identified gaps in Nuclear Safety. The instrumentation is licensed using the pressure and temperature reached during a design basis accident, but SA phenomena are not considered on its design limits. During a SA, it is likely that the pressure or temperature r...

Modern Russian Generation-III/III+ Nuclear Power Plants (NPP) have experienced an outstanding expansion outside the Russian Federation in countries such as China, Turkey, India, Bangladesh, Egypt, Belarus or Iran including ongoing discussions to build VVER-1200 NPPs in Hungary and Finland. In this article, it is described how the safety features of...

AP1000® Generation III+ reactor bases its safety concept on passive systems, differently from the previous Generation II reactors. This fact has led the approximations and methodologies previously used for modeling active safety systems to be reviewed and adapted to simulate the physics of passive systems. Diverse studies about the AP1000 containme...

After the Fukushima-Daiichi accident, different methods, strategies and guidelines were developed to improve the Severe Accident Management Guidelines (SAMG). One of these additions, named the FLEX strategies, relies on portable equipment to obtain power or water to restore key safety functions in the reactor. In the present study, the FLEX strate...

During the last decades, the safety analysis of nuclear power plants, have been shifting from conservative models and hypotheses to best estimate. Within this trend, the different safety analyses can be categorized depending on their associated conservatisms. The approach that includes expanded event trees together with best estimate model and cond...

Uncertainty and sensitivity analyses are a necessary step for best estimate calculations for licensing. In this sense, a complete statistical characterization of a sequence would be a useful tool for these assessments as it can detect behaviors and correlation of the Figures of Merit (FoM) and the input space. For this reason, the present paper pre...

Anticipated Transient Without Scram (ATWS) sequences belong to the beyond design basis events. Within ATWS sequences, the most limiting for PWRs is the Loss Of Normal Feedwater (LONF). This sequence produces a pressure peak in the reactor cooling system that can compromise its integrity. To cope with this sequence, systems like the AMSAC were insta...

Severe accidents in nuclear power plants are still an active field in containment safety research because of their complex phenomenology, their wide range of consequences and the uncertainty involved in the computational modeling. The main contributors to this difficulty are the potential harsh conditions in the containment due to hydrogen combusti...

Containment safety analysis is a field in expansion given the complex phenomenology developed during an accident, and the recent code capabilities improvement. In this paper, a modeling strategy to create complex containments with porous CFDs in a single control volume is presented. This methodology involves using solely Computer Aided Design (CAD)...

A fluid is in supercritical phase when it is held above its critical pressure. In the vicinity of the critical point, the fluid experiences strong variations of the thermophysical properties with accentuated gradients, producing a turbulent heat transfer behavior, difficult to solve with Computational Fluid Dynamics (CFDs). The present research ass...

Nuclear energy has created controversy since its conception during the 1950s. Arguments against it have been constant through the years until the current state on which the majority of western societies are against it as seen in recent surveys. Additionally, confidence in science and scientists is also relatively low. In Spain, these two facts are...

The continuous development of evaluation models in the nuclear industry makes mandatory to keep the highest safety standards. The model updating performed for the Almaraz NPP containment has been focused on: the addition of the newest phenomenological models available on the latest version of GOTHIC, the use of new data that increase the detail in...

In order to enhance Generation II and III reactors safety, Generation III+ reactors have included passive mechanisms for their safety systems that do not need alternating current supply to work correctly. Specifically, the AP1000® reactor uses these mechanisms in both its safety systems including the Passive Containment Cooling System (PCS), which...

The AP1000® advanced reactor passive safety systems are based on natural phenomena to ensure the containment integrity during an accident. One of the most important passive systems is the Passive Core Cooling System (PXS) which includes the In-containment Refueling Water Storage Tank (IRWST), a pool that serves as a heat sink for the Passive Residu...

In order to enhance Generation II reactors safety, Generation III+ reactors have adopted passive mechanisms for their safety systems. In particular, the AP1000® reactor uses these mechanisms to evacuate heat from the containment by means of the Passive Containment Cooling System (PCS). The PCS uses the environment atmosphere as the ultimate heat si...

Containment safety analyses of Design Basis Accidents (DBAs) rely on the use of Lumped Parameters (LP) codes, and therefore, on pressure and temperature averaged values. In those analyses the full containment building is usually modeled with a single or few computational cells. During the latest years, many efforts have been done to develop 3D cont...

During a severe accident in a nuclear power plant, there are several challenges that need to be faced. To coup with a containment overpressure, the venting action will lower the pressure but it will release radioactivity to the environment. In order to reduce the radioactivity released, a filtered containment venting system can be used to retain io...

¿Hasta dónde nos remontamos? Para encontrar los orígenes de la fusión nuclear, la primera pregunta que debe responderse es: ¿Dónde podemos situar el inicio de la serie de acontecimientos que desembocarían en ella? En este sentido se establecerá como inicio, de una forma arbitraria, que para alcanzar la fusión nuclear era preciso avanzar en dos conc...

The AP1000® advanced reactor passive safety systems are based on natural phenomena to ensure the containment integrity during an accident. One of the most important passive systems is the Passive Core Cooling System (PXS) which includes the In-containment Refueling Water Storage Tank (IRWST), a pool that serves as a heat sink for the Passive Residu...

During a nuclear accident, several drop-formation processes occur, such as flashing in the break, the use of containment sprays, or film condensation. Each phenomenon has a characteristic drop size which it is important in containment thermal-hydraulics. In numerical simulations of containments, it is common to model the drop phase with a unique si...

AP1000® is a Generation III+ reactor in which all safety systems relay on passive elements. AP1000 containment includes an In-containment Refueling Water Storage Tank (IRWST), a stainless steel liner that acts as a heat sink, and a Passive Residual Heat Removal System (PRHRS). In a containment Design Basis Accident (DBA) all these components are in...

The Millennial generation is usually delimited to western people born between 1980 and 1999 (figures may vary depending on the study). Millennial generation is entering the work labor force worldwide and this has made them extensively studied. This generation has common characteristics between its members worldwide, and those may create a "generati...

Note : ** [Thesis Title is misleading] ** The computational simulation of nuclear containment phenomenology during an accident has been historically a challenging issue. The containment size, the extreme characteristics of the mass and energy release and the presence of several phases and species have enclosed this discipline within the lumped para...

Containment Design Basis Accident analysis are usually performed using lumped-parameters models as this kind of models do not require high computational resources. Moreover, they offer overall good results of average pressure and temperature evolution. However, in order to perform a detailed local analysis, a thermal-hydraulic behavior study of eve...

Efficient Communication is usually pointed out as a valuable skill for engineering companies. However, teaching efficient communication skills is normally not a first order priority in engineering schools in Spain. There are optional courses to learn how to speak in public or to write correctly, but in general these haven't been considered as core...

Creativity is usually defined as the capability of generating ideas or products that are new, useful and that have an impact. This looks like a very important aspect in an engineer's life. Some authors relate creativity and intelligence till the point of discussing if they are in fact the same thing. On the other hand, creativity has never been a...

The confinement of radioactive material in a nuclear power plant, including the discharge control and the release minimization, is a fundamental safety function to be ensured in a design basis accident (DBA). For plant licensing analysis, the containment is usually modeled with a lumped parameter approach. Inherent to the lumped parameter approach...

This project was started in December 2013, with the International Benchmark Exercise (IBE-3) performed in the PANDA facility at the PSI. The benchmark provides a good start to a deep study of the simulation of hydrogen distribution with the GOTHIC code. The Parameter Influence Chart was the final conclusion to this study and it could be a worldwide...

The Fukushima accident has drawn attention even more to the importance of external events and loss of energy supply on safety analysis. Since 2011, several Station Blackout (SBO) analyses have been done for all type of reactors. The most post-Fukushima studies analyze a pure and straight SBO transient, but the Fukushima accident was more complex th...

The simulation of design basis accidents in a containment building is usually conducted with a lumped parameter model. The codes normally used by Westinghouse Electric Company (WEC) for that license analysis are WGOTHIC or COCO, which are suitable to provide an adequate estimation of the overall peak temperature and pressure of the containment. Ho...

The simulation of design basis accidents in a containment building is usually conducted with a lumped parameter model. The codes normally used by Westinghouse Electric Company (WEC) for that license analysis are WGOTHIC or COCO, which are suitable to provide an adequate estimation of the overall peak temperature and pressure of the containment. How...