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Kudinov P.,KTH Royal Institute of Technology | Davydov M.,Electrogorsk Research and Engineering Center
Nuclear Engineering and Design | Year: 2013

Ex-vessel termination of accident progression in Swedish type Boiling Water Reactors (BWRs) is contingent upon efficacy of melt fragmentation, quenching, solidification and formation of a coolable by natural circulation porous debris bed in a deep pool of water below reactor vessel. When liquid melt reaches the bottom of the pool it can cause formation of agglomerated debris and "cake" regions, which affect hydraulic resistance and thus coolability of the bed. This paper discusses development and validation of conservative-mechanistic and best estimate approaches to quantifying mass fractions of agglomerated debris at given conditions of melt release from the vessel. Fuel-coolant interaction (FCI) code VAPEX-P is used as a computational vehicle for modeling. Experimental data from the DEFOR-A (Debris Bed Formation and Agglomeration) tests with binary oxidic simulant material melt is used for validation of developed methods. The paper discusses the influence of different inherent uncertainties in the prediction of the fraction of agglomerated debris. © 2013 Elsevier B.V. Source


Melikhov V.,Electrogorsk Research and Engineering Center | Melikhov O.,Moscow Power Engineering Institute | Yakush S.,Russian Academy of Sciences | Rtishchev N.,Moscow Power Engineering Institute
Science and Technology of Nuclear Installations | Year: 2011

A specialized module VAPEX-M has been developed and implemented as a part of an integral code, SOCRAT, to enable the modeling of fuel-coolant interactions (FCIs) during severe accidents. The mathematical model and correlations for the main physical processes are described. Results of computational analysis of three experimental series reported in the literature are presented. The calculations were carried out by the combined SOCRAT/VAPEX code and were aimed at validation of the predictive capabilities of the code. The experiments chosen cover a wide range of physical parameters, which enables different aspects of the code to be verified, that is, drag correlations (MAGICO-2000), evaporation rate (QUEOS), fuel fragmentation, and interaction with the coolant in all complexity (FARO). Generally, reasonable agreement between the measured data and calculated results was obtained, which allows one to use the combined SOCRAT/VAPEX code for severe accidents analysis. Copyright © 2011 Vladimir Melikhov et al. Source


Melikhov V.,Electrogorsk Research and Engineering Center | Melikhov O.,Moscow Power Engineering Institute | Parfenov Y.,Moscow Power Engineering Institute | Nerovnov A.,Moscow Power Engineering Institute
Science and Technology of Nuclear Installations | Year: 2011

The horizontal steam generator (SG) is one of specific features of Russian-type pressurized water reactors (VVERs). The main advantages of horizontal steam generator are connected with low steam loads on evaporation surface, simple separation scheme and high circulation ratio. The complex three-dimensional steam-water flows in the steam generator vessel influence significantly the processes of the steam separation, distribution, and deposition of the soluble and nonsoluble impurities and determine the efficiency and reliability of the steam generator operation. The 3D code for simulation of the three-dimensional steam-water flows in the steam generator could be effective tool for design and optimization of the horizontal steam generator. The results of the code calculations are determined mainly by the set of the correlations describing interaction of the steam-water mixture with the inner constructions of the SG and interfacial friction. The results obtained by 3D code STEG with the usage of the different interfacial friction correlations are presented and discussed in the paper. These results are compared with the experimental ones obtained at the experimental test facility PGV-1500 constructed for investigation of the processes in the horizontal steam generator. Copyright © 2011 Vladimir Melikhov et al. Source


Kudinov P.,KTH Royal Institute of Technology | Davydov M.,Electrogorsk Research and Engineering Center
International Congress on Advances in Nuclear Power Plants, ICAPP 2014 | Year: 2014

Ex-vessel severe accident mitigation strategy in Nordic type Boiling Water Reactors (BWRs) imply that melt released into a deep pool of water below reactor vessel will form a coolable by natural circulation porous debris bed. However, if liquid melt is not completely fragmented and quenched when it reaches the bottom of the pool it can cause agglomeration of debris, increasing hydraulic resistance and thus worsening coolability of the bed. In the previous work we have developed and validated an approach to prediction of mass fractions of agglomerated debris using Fuel-Coolant Interaction (FCI) code VAPEX-P. This paper discusses development of a surrogate model (SM) which can predict fraction of agglomerated debris with high computational efficiency. Such model is a must for affordable sensitivity and uncertainty analysis in different accident scenarios. Details of the SM development and verification against full model are provided in the paper. Source


Dombrovsky L.A.,RAS Joint Institute for High Temperatures | Davydov M.V.,Electrogorsk Research and Engineering Center
Computational Thermal Sciences | Year: 2010

This article is concerned with numerical modeling of thermal radiation from the zone of interaction of a melt jet with a water pool. This particular problem is a part of the analysis of complex interaction of the core melt with water in the case of a hypothetical severe accident in light-water nuclear reactors. The energetic contribution of thermal radiation has been studied in some detail in recent articles by the authors. In the present article, we focus on a solution related to possible optical diagnostics of the physical parameters of the process. These diagnostics can be based on comparison of the measured and calculated thermal radiation in the small-scale laboratory experiments. The sensitivity of the numerical data to some important parameters of the computational model is expected to be important to validate and improve the multiphase flow model. The radiation transfer model employed is based on the transport approximation. The numerical procedure includes ray-tracing calculations in the range of water semitransparency with a source function determined using the large-cell radiation model. It is shown that the visible radiation of the interaction zone contains important information on the process parameters, and these parameters might be identified on the basis of the developed computational procedure for the direct problem. © 2010 by Begell House, Inc. Source

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