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Enhancing Nuclear Safety


Research

Theses in progress

Flame propagation analysis in presence of water droplets


Host laboratory:Severe Accidents and Radioactive Release Study & Analysis Section (B2EGR)

Beginning of the thesis: October 2015

Student name: Roberto Caruso


Subject description

Water Spray Systems, are widely used to decrease the containment building pressureand 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 experiments.

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.

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​Severe Accidents and Radioactive Release Study & Analysis Section (B2EGR)

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