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Dive into the research topics where Walter Villanueva is active.

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Featured researches published by Walter Villanueva.


Science and Technology of Nuclear Installations | 2014

Approach and Development of Effective Models for Simulation of Thermal Stratification and Mixing Induced by Steam Injection into a Large Pool of Water

Hua Li; Walter Villanueva; Pavel Kudinov

Steam venting and condensation in a large pool of water can lead to either thermal stratification or thermal mixing. In a pressure suppression pool (PSP) of a boiling water reactor (BWR), consistent thermal mixing maximizes the capacity of the pool while the development of thermal stratification can reduce the steam condensation capacity of the pool which in turn can lead to pressure increase in the containment and thereafter the consequences can be severe. Advanced modeling and simulation of direct contact condensation in large systems remain a challenge as evident in commercial and research codes mainly due to small time-steps necessary to resolve contact condensation in long transients. In this work, effective models, namely, the effective heat source (EHS) and effective momentum source (EMS) models, are proposed to model and simulate thermal stratification and mixing during a steam injection into a large pool of water. Specifically, the EHS/EMS models are developed for steam injection through a single vertical pipe submerged in a pool under two condensation regimes: complete condensation inside the pipe and chugging. These models are computationally efficient since small scale behaviors are not resolved but their integral effect on the large scale flow structure in the pool is taken into account.


Science and Technology of Nuclear Installations | 2014

Validation of Effective Models for Simulation of Thermal Stratification and Mixing Induced by Steam Injection into a Large Pool of Water

Hua Li; Walter Villanueva; Markku Puustinen; Jani Laine; Pavel Kudinov

Steam venting and condensation in a large pool of water creates both a source of heat and a source of momentum. Complex interplay between these two sources leads to either thermal stratification or ...


20th International Conference on Nuclear Engineering and the ASME 2012 Power Conference (ICONE20-POWER2012), Anaheim, CA, Jul 30-Aug 03, 2012 | 2012

Effect of CRGT Cooling on Modes of Global Vessel Failure of a BWR Lower Head

Walter Villanueva; Chi-Thanh Tran; Pavel Kudinov

An in-vessel stage of a severe core melt accident in a Nordic type Boiling Water Reactor (BWR) is considered wherein a decay-heated pool of corium melt inflicts thermal and mechanical loads on the ...


Nuclear Technology | 2015

PARAMETRIC STUDY OF SLOSHING EFFECTS IN THE PRIMARY SYSTEM OF AN ISOLATED LEAD-COOLED FAST REACTOR

Marti Jeltsov; Walter Villanueva; Pavel Kudinov

Risks related to sloshing of liquid metal coolant due to seismic excitation need to be investigated. Sloshing effects on reactor performance include first, fluid-structure interaction and second, gas entrapment in the coolant with subsequent transport of void to the core region. While the first can hypothetically lead to structural damage or coolant spill, the second increases the risk of a reactivity insertion accident and/or local dryout of the fuel. A two-dimensional computational fluid dynamics study is carried out in order to obtain insights into the modes of sloshing depending on the parameters of seismic excitation. The applicability and performance of the numerical mesh and the Eulerian volume of fluid method used to track the free surface are evaluated by modeling a simple dam break experiment. Sloshing in the cold plenum free surface region of the European Lead-cooled SYstem (ELSY) conceptual pool-type lead-cooled fast reactor (LFR) is studied. Various sinusoidal excitations are used to imitate the seismic response at the reactor level. The goal is to identify the domain of frequencies and magnitudes of the seismic response that can lead to loads threatening the structural integrity and possible core voiding due to sloshing. A map of sloshing modes has been developed to characterize the sloshing response as a function of excitation parameters. Pressure forces on vertical walls and the lid have been calculated. Finally, insight into coolant voiding has been provided.


Nuclear Engineering and Design | 2018

Pool stratification and mixing induced by steam injection through spargers: analysis of the PPOOLEX and PANDA experiments

Ignacio Gallego-Marcos; Pavel Kudinov; Walter Villanueva; Ralf Kapulla; Sidharth Paranjape; Domenico Paladino; Jani Laine; Markku Puustinen; Antti Räsänen; Lauri Pyy; Eetu Kotro

Spargers are mutli-hole injection pipes used in Boiling Water Reactors (BWR) and Advanced Pressurized (AP) reactors to condense steam in large water pools. A steam injection induces heat, momentum and mass sources that depend on the steam injection conditions and can result in thermal stratification or mixing of the pool. Thermal stratification reduces the steam condensation capacity of the pool, increases the pool surface temperature and thus the containment pressure. Development of models with predictive capabilities requires the understanding of basic phenomena that govern the behavior of the complex multi-scale system. The goals of this work are (i) to analyze and interpret the experiments on steam injection into a pool through spargers performed in the large-scale facilities of PPOOLEX and PANDA, and (ii) to discuss possible modelling approaches for the observed phenomena. A scaling approach was developed to address the most important physical phenomena and regimes relevant to prototypic plant conditions. The focus of the tests was on the low steam mass flux and oscillatory bubble condensation regimes, which are expected during a long-term steam injection transient, e.g. in the case of a Station Black Out (SBO). Exploratory tests were also done for chugging and stable jet conditions. The results showed a similar behavior in PPOOLEX and PANDA in terms of jet induced by steam condensation, pool stratification, and development of hot layer and erosion of the cold one. A correlation using the Richardson number is proposed to model the erosion rate of the cold layer as a function of the pool dimensions and steam injection conditions.


international youth conference on energy | 2015

Extension of the MELCOR code for analysis of late in-vessel phase of a severe accident

Philipp Dietrich; Frank Kretzschmar; Alexei Miassoedov; Andreas G. Class; Walter Villanueva; Sevostian Bechta

The simulation of severe accidents in nuclear power plants with system codes is a powerful tool to improve the safety measures to prevent severe accidents. The further development of severe accident codes is part of current research. MELCOR, as the leading nuclear safety code, provides the possibility to be coupled to other codes. A detailed knowledge of this coupling interface is necessary to use this possibility. Therefore, the software tool DINAMO, which contains the coupling routines and an interface to communicate with other programs, was developed. Using DINAMO it is possible to utilize new models for specific phenomena in MELCOR. In the present work the Phase-Change Effective Convectivity Model was coupled using the CFD-software OpenFOAM and DINAMO to MELCOR to improve the prediction of molten core material in the lower plenum of a reactor pressure vessel. The simulation results were compared to the experimental findings of the LIVE-facility.


14th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-14), At Toronto, Canada, Sept. 25-30, 2011 | 2011

A Study on the Integral Effect of Corium Material Properties on Melt Pool Heat Transfer in a Boiling Water Reactor

Chi Thanh Tran; Walter Villanueva; Pavel Kudinov

A Study on the Integral Effect of Corium Material Properties on Melt Pool Heat Transfer in a Boiling Water Reactor


International Journal of Multiphase Flow | 2006

Some generic capillary-driven flows

Walter Villanueva; Gustav Amberg


Bulletin of The Polish Academy of Sciences-technical Sciences | 2007

Parallel adaptive computation of some time-dependent materials-related microstructural problems

Minh Do-Quang; Walter Villanueva; Irina Singer-Loginova; Gustav Amberg


Nuclear Engineering and Design | 2013

Agglomeration and size distribution of debris in DEFOR-A experiments with Bi2O3–WO3 corium simulant melt

Pavel Kudinov; Aram Karbojian; Chi Thanh Tran; Walter Villanueva

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Pavel Kudinov

Royal Institute of Technology

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Marti Jeltsov

Royal Institute of Technology

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Hua Li

Royal Institute of Technology

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Kaspar Kööp

Royal Institute of Technology

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Chi Thanh Tran

Royal Institute of Technology

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Dmitry Grishchenko

Royal Institute of Technology

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Aram Karbojian

Royal Institute of Technology

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Gustav Amberg

Royal Institute of Technology

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Andrei Goronovski

Royal Institute of Technology

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