Thermal mixing in a model cold leg and downcomer at low flow rates. [PWR]

This report describes an experimental program of fluid-mixing experiments performed at atmospheric pressure in a 1/5-scale, transparent model of a cold leg and downcomer typical of Combustion Engineering and Westinghouse Pressurized Water Reactors (PWRs). The test program simulated steady-state conditions thought to be extreme for small break Loss of Coolant Accidents (LOCAs). Analysis of transient and steady-state temperature records indicates that the cold High-Pressure Injection (HPI) coolant water and the hot primary coolant water are well mixed prior to flowing over the reactor vessel wall.