Development and validation of the multi-physics DRACCAR code

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Computational predictions concerning ballooning of multiple fuel pin bundles during a loss of coolant accident with a final reflooding phase are now more than ever of interest in the framework of light water reactor nuclear safety. To carry out these studies, two difficulties have to be overcome. First, the modeling has to take into account many coupled phenomena such as heat transfer (heat generation, radiation, convection and conduction), hydraulics (multidimensional 2-phase flow, blockage), mechanics (thermal expansion, creep, embrittlement) and chemistry (oxidation, hydriding). Secondly, there are only a few experimental investigations that can help to validate such complex coupled modeling. Over several years, IRSN has developed the 3D computational tool DRACCAR to investigate rod bundle strain during LOCA transients including prediction of the reflooding phase. DRACCAR code is dedicated to study complex configurations such as the deformation and possible contact between neighboring rods and the associated blockage of thermalhydraulic channels in the ballooned zone of the fuel assembly. Modeling efforts have been devoted to the assessment of the coolability of deformed geometries by coupling the thermo-mechanical behavior of the fuel assembly to the thermalhydraulics. The physical modeling available in the current version of DRACCAR V2.3.1 as well as its flexibility are depicted. As a conclusion, some prospects regarding the development of the future version DRACCAR V3 are provided, in particular accounting for the knowledge acquired through IRSN R&D project PERFROI.

Section: Validation and Applicationmentioning

confidence: 99%

“…In the framework of the European project, NUclear REactor SAFEty simulation platform (NURESAFE SP3) project, apart from IRSN, AREVA (Fargette (2017)) and ENEA (Bascou et al (2015)) used the code to perform some validation work…”

Section: Validation and Applicationmentioning

confidence: 99%

DRACCAR: A multi-physics code for computational analysis of multi-rod ballooning, coolability and fuel relocation during LOCA transients Part one: General modeling description

Glantz

Taurines

Luze

et al. 2018

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“…Validation is as well as verification a continuous process which accompanies code development and evolutions since the start of the DRAC-CAR project. Part of this validation work has been already presented for previous code version (Bascou et al (2015)).…”

Section: Draccar Validation Strategymentioning

confidence: 99%

“…DRACCAR cannot answer to the whole problematic of spent fuel pool accidents involving complex natural convective exchanges within the pool and with the atmosphere of the building. Nevertheless, DRACCAR modeling offers advantages such as its 3D-unstructured grid suitable for non-axisymmetric configurations and its physical models such as zircaloy oxidation in steam and air atmosphere as explained in chapter 7 of OECD/NEA (2015) dedicated to simulation tools and in Bascou et al (2015). The validation of DRACCAR for such application is based on the Sandia Fuel Project (SFP) programme promoted from 2009 to 2013 by OECD/NEA and the U.S.NRC.…”

Section: Spent Fuel Pool Applicationsmentioning

confidence: 99%

DRACCAR: A multi-physics code for computational analysis of multi-rod ballooning, coolability and fuel relocation during LOCA transients. Part Two: Overview of modeling capabilities for LOCA

Glantz

Taurines

Belon

et al. 2018

Self Cite

Computational predictions concerning ballooning of multiple fuel pin bundles during a loss of coolant accident with a final reflooding phase are now more than ever of interest in the framework of light water reactor nuclear safety. To carry out these studies, two difficulties have to be overcome. First, the modeling has to take into account many coupled phenomena such as heat transfer (heat generation, radiation, convection and conduction), hydraulics (multidimensional 2-phase flow, blockage), mechanics (thermal expansion, creep, embrittlement) and chemistry (oxidation, hydriding). Secondly, there are only a few experimental investigations that can help to validate such complex coupled modeling. Over several years, IRSN has developed the 3D computational tool DRACCAR to investigate rod bundle strain during LOCA transients including prediction of the reflooding phase. The DRACCAR code is dedicated to study complex configurations such as the deformation and possible contact between neighboring rods and the associated blockage of thermalhydraulic channels in the ballooned zone of the fuel assembly. To accompany the development of DRACCAR, efforts have been devoted to the validation of the coupling between the thermo-mechanics and thermalhydraulic models -including reflooding -through a comparison to integral experiments dedicated to LOCA. The DRACCAR capabilities and validation status are depicted for the version DRACCAR V2.3.1. DRACCAR provides an interesting insight on LOCA by simulating multi-rod and fluid interaction which cannot be investigated with a classical single rod approach. As a conclusion, some prospects regarding the development and validation of the future version DRACCAR V3 are mentioned. In particular significant evolutions are expected regarding the cladding rupture prediction, the contact simulation and the assessment of the coolability of deformed geometries. These evolutions will be based on the knowledge acquired through the R&D project PERFROI, a project dedicated to LOCA, launched by IRSN in association to other partners and supported by the French National Research Agency (ANR).

“…It is currently coupled to the two phase flow module CESAR of the ASTEC code (Trégourès 2010). The combination of DRACCAR and CESAR codes enable the modelling of various phenomena including heat transfer (HT) within solids and HT to the fluid, material property evolution (growth of an oxidic layer, phase change), contact between structures and cladding integrity (Bascou 2015). To allow the simulation of spent fuel pool draining accidents, some models have been developed (or improved) and main concerns are air oxidation and nitriding, as well as axial radiative HT (to account for very high axial temperature gradients).…”

Section: The Draccar Codementioning

confidence: 99%

Simulation of the OECD/NEA Sandia Fuel Project Phases I & II ignition tests with DRACCAR

Luze

Jacq

Guillard

2018

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An OECD/NEA PWR spent fuel pool experimental program is simulated with the code DRACCAR v2.3.  New code modelings have been developed for radiative heat transfers in the bundle and for zirconium nitrides production.  Air induced flow rates have been correctly reproduced in both storage patterns with the additional hypothesis of oxides swelling.  Fuel clad temperature response for a recently discharged assembly in a uniform pattern is well assessed.  Thermal response for bundles in a 14 pattern still depending on additional hypotheses not fully checked.