THE TRIGGERABILITY AND EXPLOSION POTENTIALS OF REACTOR CORE MELT AT FUEL COOLANT INTERACTIONS

摘要

The Test for Real cOrium Interaction with water (TROI) experiments have been performed to reveal unsolved issues of a steam explosion using real core material at the Korea Atomic Energy Research Institute. One of the findings from the TROI experiments is that the results of a fuel coolant interaction (FCI) are strongly dependent on the composition of corium, which is composed of UO_2, ZrO_2, Zr, and steel. The TROI tests were analyzed in view of a particle size response for various types of fuel coolant explosions. This can provide an understanding about the relationship between an initial condition, the mixing, and the explosion. The particle size distribution data from the TROI tests and a single-particle film boiling model were used for all these analyses. The difference between a quenched FCI and an explosive FCI was defined by comparing the final particle size. This analysis indicates that an explosive FCI resulted in a large amount of fine particles and in a small amount of large-sized particles. With this, the mixing size of the particles that participate in the steam explosion and the fine-particle size produced from a steam explosion can be defined in the TROI test. The particle size distributions of the quenched TROI tests were then considered. We note that the explosive test results cannot provide information on the mixing process. This analysis on the particle size indicates that a self-triggered system includes large-sized particles to participate in a steam explosion, but a non-self-triggered system includes smaller-sized particles and more fine-sized particles. Finally, the explosion potentials of the quenched TROI tests were compared to each other. Thus, the single-particle film boiling model based on the particle size distribution provides the explanation for the explosion behaviors of a variety of melts.