Scaling pressure and subcooling for countercurrent flow. Quarterly progress report, April 1, 1978--June 30, 1978. [PWR]

Recent results of a continuing program to develop semi-empirical models of lower plenum filling after a gypothetical PWR LOCA are presented. The idealized situation of countercurrent flow in a 1/15 -scale PWR model is specifically addressed here. For saturated water behavior in small-scale facilities, it is shown that the dimensionless J* parameters properly scale the effects of vessel size, injection rate, and (for the first time with steam and water) vessel pressure. Building on previous work, new correlation concepts are proposed to account for the effects of condensation on ECC bypass. Comparison with new data over an increased range of pressures and subcoolings shows that for a given injection rate, the effects of condensation can be accounted solely in terms of thermodynamic ratio rather than pressure or subcooling independently. The data indicate that subsooling has a weaker effect on ECC bypass than was previously believed. The data also reveal a transition in behavior at a thermodynamic ratio near unity; at values below this transition the behavior is close to that of saturated water at all pressures tested. These findings suggest a need for caution when taking credit for the benefits of subcooling on ECC bypass in calculated LOCA transients.