Experimental Investigation on Debris Bed Quenching With Additional Non-Condensable Gas Injection

Abstract

Severe accidents of light water reactors with core degradation can lead to the formation of a, so-called, debris bed inside the reactor cavity. In the scenario of depleted residual water, the bed can partially melt and interact with the concrete underneath generating noncondensable gases (NCG) at the bottom of the particle bed, which will flow through the debris bed. The impact of additional gas on the quenching process can in principle be considered in thermal-hydraulic system codes such as ATHLET; however, there is still a need for experimental validation of respective models or verification of corresponding simulation results. Therefore, especially for the model validation of COCOMO-3D, which is implemented in ATHLET, a specific extension to the existing experimental database is required. Experimental results of the quenching behavior of a monodispersed particle bed at top-flooding cooling condition with additional NCG injection, utilizing the new built-up test facility FLOAT (flooding facility with gas injection), are presented.