Fabien Duval

Institut de Radioprotection et de Sûreté Nucléaire (IRSN) | IRSN

The purpose in this paper is to design finite‐volume schemes on structured grids for the transport of piecewise‐constant functions (typically, indicator functions) with as low diffusion as possible. We first propose an extension of the so‐called Lagrangeprojection algorithm, or downwind scheme with an Ultrabee limiter, for the transport equation in...

This paper deals with the study of dissolution phenomena in corium crust, in a severe accident. In case of an In-Vessel Retention (IVR) strategy, it is expected that the corium pool will be surrounded by an oxide crust, which will be in contact with molten steel from the top, and along the sides. CORDEB experiments have shown that this crust become...

Turbulence is a common feature to all flows that surround us. Despite its ubiquity, particularly in industrial flows, it is very difficult to provide a mathematical framework for the generation of turbulent eddies. Several methods have been proposed which are able to reproduce realistic features for velocity fluctuations, exhibiting proper space- a...

This paper deals with the study of dissolution phenomena in corium crust, in a severe accident. In case of an In-Vessel Retention (IVR) strategy, it is expected that the corium pool will be surrounded by an oxide crust, which will be in contact with molten steel from the top, and along the sides. CORDEB experiments have shown that this crust become...

The risk of dust explosion appears in many industrial situations. In nuclear safety analysis, one of the scenarios is the risk of graphite dust explosion that may occur during decommissioning operations of UNGG reactors [6]. In such a case, the problem is considered as a dispersed two-phase flow with particle size typically ranging from 1 to 100 µm...

Heat transfers in dilute gas-particle mixtures are often modeled using hybrid Euler–Lagrange descriptions, treating the carrier fluid via an Eulerian representation and following each particle in a Lagrangian framework. One of the focal issues in these models is the calculation of the macro-scale heat transfer between the continuous phase and parti...

The risk of dust explosion appears in many industrial situations. In nuclear safety analysis, one of the scenarios is the risk of graphite dust explosion that may occur during decommissioning operations of UNGG reactors [6]. In such a case, the problem is considered as a dispersed two-phase flow with particle size typically ranging from 1 to 100 µm...

In this paper, a macro-scale model is proposed to describe heat transfer in a dilute gas-particle mixture. The continuous phase is described by a filtered Eulerian approach while the dispersed one is represented as Lagrangian particles. The filtered model, which is obtained using an up-scaling methodology, consists of a macroscopic heat transfer mo...

We report the experimental measurements of mass transport induced by a jet impinging a density interface. Using water/salt-water laboratory experiments, we investigate the mechanism of mass entrainment by performing simultaneous velocity and density measurements. We observe that the mass transport leading to the homogenisation of the density is due...

The dynamics of isolated air bubbles crossing the horizontal interface separating two Newtonian immiscible liquids initially at rest are studied both experimentally and computationally. High-speed video imaging is used to obtain a detailed evolution of the various interfaces involved in the system. The size of the bubbles and the viscosity contrast...

2D Molten Core Concrete Interaction (MCCI) experiments involving a homogeneous corium pool configuration have been carried out recently at Argonne National Laboratory in the frame of the OECD/NEA-MCCI1.2.3 cooperative project, and at CEA Cadarache in the frame of CEA-EDF-IRSN VULCANO4.5 programs. The aim of this work is to present the interpretatio...

Bubbly flows appear in a large variety of engineering applications from the petroleum to the nuclear industry. A common model used in these contexts is the so-called drift–flux model where the slip velocity (the difference between the velocities of the gas and of the liquid) is expressed on the basis of empirical correlations. However, depending on...

In the framework of its research programme on severe nuclear reactor accidents, the Institut de Radioprotection et de Sûreté Nucléaire (IRSN) investigates the water flooding of an overheated porous bed, where complex two-phase flows are likely to exist. A better understanding of the flow at the pore level appears to be necessary in order to justify...

This work deals with the design and numerical approximation of an Eulerian mixture model for the simulation of two-phase dispersed flows. In contrast to the more classical two-fluid or Drift-flux models, the influence of the velocity disequilibrium is taken into account through dissipative second-order terms characterized by a Darcy law for the rel...

During a severe nuclear accident, a part of the molten corium resulting from the core degradation may relocate down to the lower plenum of the reactor vessel. The interaction with residual water in the lower plenum leads to a fragmentation of the corium and formation of particles (characteristic length-scale: 1–5 mm). In order to predict the safety...

In the framework of its research programme on severe nuclear reactor accidents, IRSN investigates the water flooding of an overheated porous bed, where complex two-phase flows are likely to exist. The goal is to describe the flow with a general model, covering rods and debris beds regions in the vessel. A better understanding of the flow at the por...

The MCCI code MEDICIS implemented in the reactor accident code system ASTEC-V1 addresses the ex-vessel corium long term behaviour during a severe nuclear reactor accident. The module general features are the lumped parameter approach based on a layer averaged description, the tool flexibility permitting an easy addition of new models. MEDICIS is in...

The assumption of local thermal equilibrium for describing macroscopic heat transfer in a porous medium subjected to a liquid–vapor flow with phase change has been often investigated. Under certain circumstances, this assumption appears to be too restrictive and fails to be valid. In this paper, the method of volume averaging is used to derive a th...

A multi-dimensional three-temperature model for two-phase flow through debris beds is presented. It is implemented in the ICARE/CATHARE code which has been developed by the French Institut de Radioprotection et de Sûreté Nucléaire (IRSN) for the study of severe accident scenarios in PWRs. The model is based on generalized Darcy momentum equations f...

A multi-dimensional three-temperature model for two-phase flow through debris beds is presented. It is implemented in the ICARE/CATHARE code which has been developed by the French Institut de Radioprotection et de Sûreté Nucléaire (IRSN) for the study of severe accident scenarios in PWRs. The model is based on generalized Darcy momentum equations f...

We address the finite element solution of the Cahn-Hilliard/Navier-Stokes model proposed in (2) with artificial boundary conditions. Our aim is to perform simulations focussing on a particular zone of the flow, to be further exploited for upscaling purposes in a two-level physical modelling. To obtain as less as possible perturbating boundary condi...

The WEX and MEDICIS codes are currently part of the integral code ASTEC V1 for the simulation of MCCI phenomena that may evolve during a severe core melt accident in PWR nuclear power plants. WEX represents the traditional modelling approach to the MCCI phenomenology and is limited in flexibility for additional models and model options. MEDICIS has...

Transferts thermiques sur parois rugueuses : modèles de surface effective pour des écoulements laminaires