Analyzing and modelling natural circulation phenomena in a CANDU 6

This paper discusses multi-channel flow phenomena and presents theories to explain them and models to predict their consequences in a Candu 6. A multi-channel linear model was developed to predict the heat transport system conditions under which the two-phase coolant flow is oscillatory. It is postulated that vapour in the reverse-flowing outlet feeder results from entrainment of vapour bubbles in the outlet header due to oscillatory flow in the header and feeders. It is further postulated that these bubbles in the header are supplied by the forward-flowing feeders which are located in the same feeder bank as the reverse-flowing outlet feeder. A model was developed to compute the flow and void fraction in the reverse-flowing feeder and the connected channel