A Simple Evaluation Method of the Molten Fuel Amount in a Premixing Region of Fuel-Coolant Interactions

概要

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A simplified method to evaluate the premixing molten core mass is proposed, based on the molten jet breakup length and settling/cooling dynamics of the particles generated from the jet surface. The present method was applied to KROTOS experiments at JRC Ispra with alumina and corium melts, as well as to a prototypic geometry for an ex-vessel fuel-coolant interaction during a PWR severe accident. The calculation on the KROTOS showed that the corium melt makes a premixture containing much less fraction of molten droplets than alumina, giving an explanation on the experimental fact that corium is hard to make a steam explosion. The calculation with PWR ex-vessel conditions showed that the particle mass in the premixing region tends to increase much slower than the total molten core ejected to the water pool, and that the molten mass in the premixing region is 6.5 t when 100 t of the core was ejected at 20 s after the start of the melt ejection. Sensitivities on the assumed molten core particle size, the void fraction and the jet breakup length were examined in the PWR case. A larger particle diameter caused less total premixing particles but more molten particles. A larger void fraction or a shorter jet breakup length changed the total premixing mass but did not significantly change the molten part.
社団法人日本原子力学会の論文
2002-01-25