In the nuclear industry, pool scrubbing is one of the retention mechanisms capable of reducing the release of fission products during a severe nuclear accident. It relies on a set of physical and chemical processes that are governed by the behavior of bubbles. The efficiency of this filtration process will depend on the different flow conditions and hydrodynamic parameters. Experimental work has been carried out, for which an optical measurement technique has been implemented in order to characterize different parameters related to bubble hydrodynamics such as frequency, shape, bubble volume and void fraction. Two approaches to characterize bubble formation are implemented. A classical approach has been conducted, based on the assumptions usually considered in the main models of the literature, namely a unique regime of bubbles and a spherical shape. The comparison of the bubble characteristics (volume and diameter), which are obtained after determining the frequency of bubble detachment shows good agreement with these models. However, the comparison with the observed bubble morphology (coalescence, non-sphericity) shows the limits of these assumptions. This led us to introduce, via a more phenomenological approach, the concept of globule, i.e. a structure of larger volume, generated after coalescence of several bubbles in the injection zone. This approach appears more relevant for further studies. These volumes are generally higher than those predicted by the usual approaches, highlighting the limits of existing models for high Weber numbers. This phenomenological approach is confirmed by comparing the flow rate calculated experimentally (thanks to the determined volumes and frequencies of the globules formed) with the actual flow rate injected. In the long term, this will make it possible to improve the modelling of such phenomena, in particular in the ASTEC calculation code developed by the IRSN to simulate a serious nuclear accident and its consequences.