Experiments for a core catcher concept based on water addition from below

Abstract

A core catcher concept is proposed to be integrated into a new PWR design based on the standard German PWR. The core catcher achieves coolability by spreading and fragmentation of the ex-vessel core-melt based on the process of water inlet from the bottom through the melt. To ge more detailed information on the very important process of water penetrating into the melt, simulant experiments have been conducted using a transparent plastic and a solder melt representing the oxidic and metallic part of the core-melt. It appears from the results that fragmentation of the melts can be achieved by proper selection of water supply pressure and water feed cross-section. The important part of the transient medium scale experiments with thermite melts, conducted since mid 1993, is to get information on the process of evaporation of water by water ingression in hot melts from below and to investigate whether there is a possibility of strong melt-water interactions, or even steam explosions. The experimental set-up represents a section of the core catcher. A thermite melt is located on the catcher plate with water supply from the bottom. After ignition of the melt, the upper sacrificial layer is eroded until water penetrates into the melt from the bottom through the holes in the supporting plate and fragmentation and simultaneous solidification of the melt occurs. The experiments, up to now, show that flooding and early coolability of the melt by water addition from the bottom are achieved. These experiments serve also as pretests for the COMET-H experiments with sustained heating planned to be conducted in the BETA-facility at the beginning of next year.