Guillaume Barba Rossa
article posted 29 Jan 2016
Guillaume Barba Rossa is a graduate of Ecole polytechnique Paris,
working in the field of fluid mechanics and heat transfers. He worked as a research intern at the University of
Nottingham on modelling and simulating long term carbon capture in deep saline aquifers for the European
PANACEA project. He is now a PhD candidate at the French Atomic Energy and Alternative Energies
Commission and his research is concerned with the understanding and simulation of High-Level-Waste
vitrification in cold crucibles with direct electromagnetic induction.
The Transport and settling of platinum-group-metal particles in glass melts
Guillaume Barba Rossa*, Emilien Sauvage
CEA, DEN, DTCD, SCDV, LDPV, F-30207 Bagnols-sur-Cèze, France
Our work is linked with the development of models and numerical simulations of High-Level-Waste (HLW) vitrification processes. Platinum-Group-Metals
(PGM) are found in the vitrification process of nuclear waste as fission products. During the melting, the glass generally shows a homogeneous liquid phase
seeded with non-soluble heavy platinum-group-metal particles mainly made of palladium and ruthenium dioxide.
Previous studies reported spatial discrepancies of the local volume fraction of particles in the melt because of particles settling with time. This migration
of particles towards less agitated bottom parts of the crucible impacts the dynamical, electrical and thermal state of the melt because of concentration-dependent
electrical conductivity and viscosity of the suspension. A theoretical one-fluid transport model is derived with little hypothesis, with particular attention payed
to the hindered settling term.
The resulting unsteady transport equation has shown to account for observed volume fraction profiles in seeded glass heat treated at different temperatures
and for different time horizons. These experiments have been carried out with a HLW glass simulant and we measured PGM particles local concentration using Laser
Induced Breakdown Spectroscopy. We investigate both isothermal and non-isothermal settling and special attention is given to the temperature dependence of Stokes
terminal settling velocity and particles' diffusivity due to temperature dependent glass viscosity. The model can easily be coupled with existing 3D thermo-hydraulic
numerical codes, thus enhancing the precision of heat flux predictions between the melt and the crucible. The full model will eventually help designing crucibles
taking into account PGM transport in the melt.