Variation of heat load due to in-vessel debris bed in IVR condition

Abstract

We performed experiments investigating the heat load imposed on the inner reactor vessel wall in the in-vessel retention of core melt condition, varying the debris bed height and configuration. Mass transfer method was adopted to achieve high RaʹH of order ∼1015 with compact test rigs. We tested three types of the debris configurations: cone, flat and skew debris beds. The results showed that Nusselt numbers decreased in both the uppermost and the curved surfaces with the increasing bed height. Due to the friction increased by the debris bed, the natural convective flow in the oxide pool was weakened, which intensified the impairment of the heat transfer. As the rising plume at the center was disturbed by the porous structure of the debris bed, the local average heat transfer of the uppermost surface was weakened at the center. The heat transfer was dramatically decreased at the curved surface where the debris bed was covered.