An Investigation of the Particle Size Responses for Various Fuel-Coolant Interactions in the TROI Experiments

The TROI tests were analyzed in view of the particle size responses for various types of fuel-coolant interactions. This can provide an understanding about the relationship among the initial conditions, mixing, and explosion. First, several findings from the TROI experiments were considered. The results of the fuel-coolant interactions (FCIs) were dependent on the composition of the corium, the water depth, and the water area in the TROI experiments. Then, the difference between the explosive FCI and nonexplosive FCI was defined by comparing the final particle size. This analysis indicates that the explosive FCI resulted in a large amount of fine particles and a small amount of big particles. With this, the mixing size of the particles to participate in the steam explosion and the fine particle size produced from the steam explosion could be defined in the TROI test. And then, the parametric effects on the particle size were analyzed using the nonexplosive TROI tests. We note that the explosive test results cannot provide information on the mixing process. This analysis on the particle size response indicates that the explosive system includes large-sized particles to participate in the steam explosion, but the nonexplosive system includes less large-sized particles and more fine-sized particles. These particle size responses should be considered during a reactor safety analysis because the particle size will be an important parameter for explaining a steam explosion occurrence or steam explosion strength.