Coolability of a DEBRIS Bed: Quenching Experiments

Abstract

In case of a severe accident, continuous unavailability of cooling water to the core will result in over heating and subsequent melt down of the fuel elements which would eventually result in the loss of fuel integrity. Under such conditions a porous structure made of heat generating particles of different sizes and shapes may be formed. The presence of decay heat in such a debris bed poses a critical threat to the reactor pressure vessel. To avoid any damage to the reactor pressure vessel the removal of decay heat from the debris bed is of great importance. The debris bed needs to be quenched by the water either flooding from top or flooding from the bottom before the continuous cooling is established. In order to investigate the quenching behaviour of debris bed by means of experiment, the non-nuclear test facility “DEBRIS” has been established at IKE. Experimental investigations of quenching behaviour for a preheated debris bed, at various initial bed temperatures, are carried out at IKE. In the new quenching tests, the cooling down behaviour of superheated polydispersed particles bed from stainless steel spheres at different thermo-hydraulic conditions has been investigated. Then, IKE’s MEWA-2D code has been applied to the DEBRIS quenching experiments in order to promote better understanding of the experimental results as well as to verify its applicability on the quenching process.