Laboratoire d'accueil : Bureau d'études et d'expertises en accident grave et rejets radioactifs (B2EGR)
Date de début de thèse : octobre 2015
Nom du doctorant : Roberto Caruso
Descriptif du sujet
Water Spray Systems, are widely used to decrease the containment building pressure
and to avoid a fission products leak, in case of Severe Accident in Nuclear Power Plant.
In case of severe accident, hydrogen may be produced and released inside the containment.
Water Spray Systems homogenize the hydrogen distribution and may lead to
“de-inertization” of the mixture through the condensation of steam on water droplets.
If the mixture is opportunely ignited, it may lead to a dangerous regime of combustion:
flame acceleration that could transit to detonation that will challenge and compromise
the containment integrity.
For what concerns the propagation of a hydrogen-air-vapor Flame in presence of water
droplets, the state of art doesn’t allow to quantify clearly in what measures and in what
conditions, the use of Water Spray (WS) can intensify the severity of the explosion.
The purpose of this research work is to establish the fundamental proprieties of the interactions between Hydrogen-Air-Vapor Flame and Water droplets, trough dedicated
Experimental investigations will be conducted in order to make clear the effects of the
WS features variations on the Hydrogen flame propagation by using Advanced Optical
Diagnostics: Schlieren Technique, Tomography and Particle Image Velocimetry.
Experimental Proof can be collected through a new facility, ENAFFEC-2 (ENceinte
d’ACCElération de Flamme, ICARE-Orléans), who can sustain 200°C and 120 bar, highly
instrumented with photomultipliers to follow the propagation of the flame. The apparatus is composed by a vertical pipe 7.65 m high with an internal diameter of 230 mm, equipped with obstacles with different shapes and dimensions. The flow field and the flame shape will be characterized by advanced high speed imaging techniques as well as high speed laser velocimetry.
The perspective of this work is to enhance the knowledge about the effect of the variation of Spray’s features as Droplets Diameter, Droplets Velocity, Density Flux on the flame dynamic to obtain information on how to design efficiently the safety spray system and thereby guarantee the Nuclear Safety.