An experimental investigation of multidimensional quenching of a simulated core debris bed

Abstract

Quenching by bottom flooding of a particulate bed simulating core debris has been experimentally studied in this work. In the experiments 6.4 mm diameter apriori oxidized stainless steel particles were placed in a basket up to a height of 28 cm from the bottom. These particles were topped with a 27 cm deep layer of 4.8 mm diameter particles. An annular passage 1.45 cm in width existed between the basket containing the particles and the test chamber. Fresh Zircaloy was distributed uniformly in the central portion of the particulate bed. The initial average temperature of the particles varied from 889 to 979°C. During flooding, though the system pressure varied, the pressure difference across the particulate layer was held constant. The experiments were carried out to determine the effect on the quenching process of the magnitude of the pressure difference across the particulate bed, the amount of Zircaloy, and the initial temperature distribution. From experiments it is found that increased pressure drop across the bed increases the multidimensional effects and reduces the quenching time. The presence of Zircaloy leads to increased local temperatures and delays complete quenching of the particulate layer. The initial temperature distribution can affect the shape of the quench front, the hydrogen production rate and the total time to quench.