Experimental Study of Aerosol Behavior During Pool Scrubbing: Part 2 — Decontamination of Aerosol Particle in Two Phase Flow

In order to decrease the leakage and diffusion of Fission Products (FPs) in a severe accident (SA) of nuclear power plants, BWR have a suppression chamber filled with water to decontaminate the polluted air from the reactor vessel when emergency ventilation is done. It’s called pool scrubbing having a function of decontamination effect that transfer particles from gas to liquid phase by blowing gas containing FP into water. decontamination factor (DF) which is an index of decontamination performance evaluation of pool scrubbing is predicted and calculated by using a flow model in the existing analysis model such as MELCOR code. Evaluation of the DF by pool scrubbing is important in analyzing SA progress of nuclear power plants. For this reason, validation of flow model and decontamination model is important. It is necessary to validate whether the analysis result of each model matches the actual phenomenon. Despite of these needs, generic experimental data on gas-liquid two phase flow including aerosol is insufficient in confirming the validity of existing model. Therefore, the aim of this study is to investigate aerosol behavior in air jet and its relation to bubbly flow structure during pool scrubbing. This is to obtain the flow structure when air - aerosol released to the pool part and are obtained. Transition behavior of particles from the gas phase into the liquid phase was observed by high-speed camera. In addition, the effect of aerosol on void fraction in the pool was measured by wire mesh sensor from the nozzle exit to the water surface ware also observed. Ejecting air-aerosol from the nozzle to the pool part at various flow rates, visualization of bubble diameter, bubble aspect ratio, void fraction and the gas phase velocity were done by using image processing and a wire-mesh sensor. From these results, we compared the parameters by the presence or absence of aerosol. DF is also compared with the model used in the MELCOR code.