Bubbles dynamics under pool scrubbing conditions for iodine compounds trapping applications

Mohamad Farhat (1, 2) , Philippe Nerisson (1) , Maxime Chinaud (2) , Olivier Vauquelin (2) , Laurent Cantrel (1)

1 IRSN/PSN-RES/SEREX/L2EC - Laboratoire d'Expérimentation Environnement et Chimie
2 IUSTI - Institut universitaire des systèmes thermiques industriels

Accident management systems are highly regarded in the designing of nuclear power plants, in order to mitigate as much as possible the radiological consequences of accidents. Wet FCVS is one of these systems that aims to trap fission products in liquid bath by pool scrubbing as well as suppression pool in BWR. Relying on set of bubble dynamics and retention mechanisms, it is essential to characterize the relevant hydrodynamics in pool scrubbing conditions, for the development and assessment of models. Injecting air induces bubble-bubble interactions which provoke, depending on the flow rate, random formation of bubbles affecting their size, shape, and frequency of bubbling. Experimental work is carried out to reveal the impact of these interactions on the formation of bubbles at a submerged orifice. Based on the different bubble's morphologies that have been observed, we first investigated the bubble-bubble interactions and then classified different bubbling regimes depending on the position of bubbles' coalescence. The biggest bubble formed above the orifice, after the coalescence of bubbles, is referred by a globule. On the basis of the morphological description of bubbles throughout our experiments, two approaches in characterizing the bubbles sizes were developed. The first conventional approach is based on the assumption of single bubbling formation and spherical shape of bubbles. Upon this approach, the comparison of characteristic bubble size Vb, which is computed after determining the bubble departure frequency fb, shows a good agreement with literature models. However, this approach is not consistent with flow morphology experimentally observed. Therefore, and through a proposed phenomenological approach, we aimed to characterize experimentally the globule formation frequency fa and its volume Va, by tracking the globules formation through image processing and reconstructing bubble shape with axisymmetric assumption. Experimental work characterizing bubble dynamics in the injection zone for different flow conditions (orifice diameter, injection flowrate, and submergence) is presented. In parallel, decontamination factors (DF) for iodine compounds are experimentally determined, in order to be able in the long term to correlate iodine trapping with hydrodynamics considerations.

Mots clés: Pool scrubbing bubble dynamics aperiodic formation bubble volume; Pool scrubbing; bubble dynamics; aperiodic formation; bubble volume

Domaines: Physique [physics]

Mohamad Farhat, Philippe Nerisson, Maxime Chinaud, Olivier Vauquelin, Laurent Cantrel. Bubbles dynamics under pool scrubbing conditions for iodine compounds trapping applications. ERMSAR2022 -The 10th European Review Meeting on Severe Accident Research, May 2022, Karlsruhe, Germany. ⟨irsn-03897011⟩