A scoping study on debris bed formation from metallic melt coolant interactions

During a hypothetical severe accident in a light water reactor, the core and internal structures melt down and the molten materials (corium) may fall into a water pool, forming a debris bed from so-called fuel coolant interactions (FCI), whose characteristics are important to corium coolability. The present study is concerned with the characterization of an ex-vessel debris bed forming form the FCI of a metal rich corium jet falling into a water pool in the reactor cavity. Five scoping tests were carried out on the DEFOR-M test facility using metallic Tin melt at different superheats. The molten tin was employed as the simulant of metal (Zr/Fe) rich corium melt. The processes of melt jet fragmentation and debris formation was recorded by high-speed cameras. The contour and volume of the resulting debris bed were measured by a three-dimensional laser scanning system, and the debris particles were sieved for their size distribution. The experimental results revealed the effects of melt superheat and water subcooling on the characteristics of a debris bed, including the bed's configuration and porosity, the particles' morphology and size distribution. A preliminary comparison of debris bed characteristics between metallic melt and oxidic melt was also provided.

Automated summary

This study focuses on the formation and characteristics of debris during a severe accident in a light water reactor, analyzing the debris bed formed by a metal-rich corium jet falling into a water pool. Experimental results show the influence of parameters like superheat and subcooling on the characteristics of the debris bed, including configuration, porosity, particle morphology, and size distribution. Preliminary comparison between metallic and oxidic debris beds was also provided.