Temperature profiles in natural and forced circulation of sodium through a vertical LMFBR blanket test assembly

Pumped circulation tests had been performed over a wide range of high and low flows in an electrically-heated blanket assembly model. In order to compare temperature distributions obtained in pumped tests with those in natural circulation operation a series of steady state natural circulation tests was performed establishing approximately similar low flow rates by heat addition to the test section and heat removal in a bypass air blast cooler. Such a comparison is made in this study. To achieve the desired circulation rates, higher temperature rise levels had to be established than were typical for pumped circulation. For the same flow Reynolds Number the normalized temperature profiles obtained were flatter than those for pumped circulation over a wide range of heat input gradients (1:1 to 4.6:1 max/m,in). 8 refs