Atmospheric Stability Inside Containments with a Heated Layer of Liquid on the Floor

A simple boundary condition has been derived which allows prediction of the stability of an enclosed atmosphere above a heated liquid. The correctness of the condition has been shown by experiments with various vapor-gas systems. Application to nuclear reactor containments under hypothetical accident conditions demonstrates the presence of a stirred atmosphere for sodium-cooled reactors. In case of water-cooled reactors, the containment atmosphere will be stirred when large amounts of fission products are present in the sump water in the concrete cavities located in the lower part of the containment building.