THEORETICAL BASIS FOR THE UCHIDA CORRELATION FOR CONDENSATION IN-REACTOR CONTAINMENTS

Correlations of data presented by Uchida et al. (1965) have been used extensively in the nuclear industry to predict condensation rates insi de containment structures, where non-condensable gas effects are impor tant. This work presents a theoretical basis for the form of the Uchid a correlation. The good performance of this correlation is found to be an artifact of the method used to perform that and subsequent experim ents. In the experiments, the initial inventory of non-condensable gas remained constant as the steam mass fraction was increased, so that t he bulk non-condensable gas density remained constant. The theory pres ented here shows that the Uchida correlation can produce substantial e rror at other bulk gas densities, raising concern in situations in whi ch non-condensable gas may be sequestered in subvolumes of a containme nt and for subatmospheric containments.