A Mechanism for the Suppression of a Steam Explosion in Real Core Melt and Water Interactions

Abstract

TROI experiments¹⁾ have been performed to reveal unsolved issues of a steam explosion by using real core material at the Korea Atomic Energy Research Institute (KAERI). 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 UO₂, ZrO₂, Zr, and steel. The TEXAS-V simulation for the TROI experiments indicated that a relatively low void fraction seems to have resulted in a strong steam explosion, and the low-voided mixture seems to have been induced by large-sized particles. The particle sizes in the nonexplosive TROI tests were analyzed because the explosive tests do not represent the particles during mixing. The analysis of particle sizes indicated that the debris size reflected the material difference, and the order of the particle size for each melt material was the same as that in the TEXAS-V simulation. The TEXAS-V calculation for the alumina/water system indicated that thermal conductivity is also related to the material effect on the FCI result. A heat loss evaluation using a single-sphere, filmboiling model showed that reliable values for thermal conductivity and particle size provide a reasonable estimation for the FCI result. The steam explosion in corium/water interactions is suppressed by a smaller particle size and an induced larger heat loss during mixing.

KEYWORDS:

• fuel coolant interaction
• steam explosion
• material effect
• TROI experiment
• particle size
• void fraction