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DOI: 10.1615/ICHMT.2010.RAD-6.490
pages 42-44

Jonathan Gerardin
LEMTA, Faculté des Sciences et Techniques, and IRSN/DPAM/SEMCA/LEMAR, France

Amine Hassini
LEMTA, Faculté des Sciences et Techniques, and IRSN/DPAM/SEMCA/LEMAR, France

Nathalie Seiler

Pascal Boulet
LEMTA (Laboratoire d'Energéetique et de Mécanique Théorique et Appliquée), CNRS UMR 7563 - Université Henri Poincaré, Nancy 1, Faculté des Sciences et Techniques BP 239 - 54506 VANDCEUVRE Cedex


The Loss Of Coolant Accident (LOCA) is one reference problem, investigated for the design of Pressurized Water Reactors (PWR) by the "Institut de radioprotection et de Sûreté Nucléaire" (IRSN) in the frame of its research program on nuclear fuel safety. In case of a break on the primary cooling loop, the core of the reactor would be damaged due to pressure and water losses and then temperature increase, inducing a deformation of the fuel rods. The safety system provides a reflooding of the reactor core by borated water. During the following transient regime a strong evaporation of water is observed carrying a large amount of water droplets, therefore involving a vapor-droplet medium flowing between the hot rods. One safety criterion is to warrant that the rod temperature does not increase above 1204°C. In the whole heat transfer process, radiative transfer cannot be neglected and it has been evaluated as representing the same magnitude order than the other transfer modes (see Peak [1] or Wong and Hochveiter [2] for example). A finer evaluation of the radiative transfer contribution remains necessary and is the focus of the present work. This has been done in a 2D configuration for the moment but should be extended to a realistic 3D geometry, and combined with a global heat and mass transfer simulation using the thermohydraulic Neptune CFD code. It requires the capacity to perform accurate and efficient computations for the radiative transfer part (with reasonable computational cost). Owing to the medium of interest (vapor and droplets in a flow), the transfer has to be considered through an absorbing, anisotropically scattering, emitting, non grey medium. Such problem of radiative transfer in a 2D geometry has been long investigated with various tools, and with different accuracy levels. The problem can be split into two steps : (i) the computation of the radiative properties (which has been done here considering simple additivity of properties for pure water droplets obtained with the Mie theory [3], and absorbing properties for the vapor using a C-k model [4]); (ii) the solution for the radiative transfer equation itself, for which numerous numerical possibilities are available.

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