In severe accidents of nuclear power plants such as the Fukushima Daiichi Unit 1 accident, aerosol containing massive amount of Fission Products (FP) could be created. Pool scrubbing is an effect of capturing these FP inside the water during the flow of aerosol. Such a situation may occur at the vent of containment vessel in the BWR as well as the heat-transfer-tube disrupted accident of steam generator in the PWR. The amount of FP released into the atmosphere could be reduced by the effect of pool scrubbing. Hence, the removal of aerosol by pool scrubbing is expected to evaluate the source terms stated below.
Although the importance of pool scrubbing has been recognized, the study for its mechanisms from the viewpoint of particle-bubble and two phase flow had not been carried out intensively. Furthermore, lack of experimental data for various conditions should be improved. Such a state leads to prevent us from analyzing the efficiency of pool scrubbing when advancing the model and testing the validation of it.
The aim of this study is to clarify the transfer of aerosol and bubble experimentally. The data from the experiment evaluates the influence of each parameter to remove the FP. The analysis code presently used adopts the model for the velocity which affect the particle to go out from the bubble. Each of them are written as (i) centrifugal deposition velocity, (ii) gravitational velocity, (iii) incoming vapor velocity, (iv) Brownian diffusion velocity. We choose our parameter which correspond to each of the velocities. Remarking that the experiment also include conditions e.g. the temperature stratification, the types of particle and gas, which is not been described in the manual. Based on the experimental result, our goal is to test validation and improve the model appropriate to the severe accidents predictive code such as the MELCOR by reflecting the study of flow mechanism and the effect of various conditions. To the end, this paper focuses on the rotation and its movement of aerosol particles inside the bubble.
This study focuses on the behavior of a single air bubble including aerosol by visualizing the inner flow of bubble containing particle. As a result for visualization of a single rising bubble, we were able to take a film of an area inside the particle where information of particle movement is seen. We also succeed in observing a clockwise rotation flow inside bubble just above the nozzle. As to avoid the refraction between air-water, we also made an experiment against rising oil droplets. From the series of experiment, the growth of upward flow from desorption to the stationary rising mode was been seen inside the droplet. As the flow grew, a top-to-bottom rotation was seen as it was mentioned in previous models.