Vaporization at high reduced pressure induced by very rapid power input
Résumé
In case of a reactivity initiated accident, some fuel rods can fail and fragments of hot fuel can be ejected in the coolant, leading to the so-called fuel-coolant interaction. For nuclear power plants, even though this could concern only a very low number of rods having some hypothetical defect, it has to be considered.
Fuel-coolant interaction has been studied from in-pile experiments performed at ambient pressure conditions. Large contact area between tiny fragments and water yields to intense heat transfer and rapid coolant vaporization which produce pressure peaks followed by a relatively large vapour pocket formation. Such events lead to stresses in the surrounding structures that remain to be studied.
In this paper, we propose to study the role of the absolute pressure on the phenomenology. Indeed, at PWR conditions, some key water properties significantly differs from those at ambient conditions, namely the liquid-vapour density ratio and the latent heat.
An experimental study has been performed. It is based on the rapid power deposit of heat within a tank of liquid CO2 at various pressure and subcooling conditions, some of being in similarity with PWR ones. Pressure measurements and video recording of the test are analysed and allow relating the pressure peaks to the heat and mass transfer processes. Intensity of the phenomena observed are correlated with thermohydraulic conditions. A model for pressure peak height and width is developed and validated against the experimental data.
Domaines
Sciences de l'ingénieur [physics]
Origine : Fichiers produits par l'(les) auteur(s)