CFD-modelling of CCFL phenomena in a PWR hot leg model

The detailed three-dimensional (3-D) information on the transient flow behaviour under countercurrent flow limitation (CCFL) in a pressurized water reactor (PWR) hot leg is an important issue in the reactor safety analysis. It relates to a hypothetical scenario of small break Loss of Coolant Accident (LOCA) in a PWR, and leads to the reflux-condensing mode. During this scenario, a part of the condensate flows back towards the reactor pressure vessel (RPV) in counter current to the steam. In this mode, a CCFL could occur, affecting the core cooling. Deendarlianto et al. (2011a) has already reviewed different applications of CFD codes to simulate the phenomena around the CCFL in a PWR hot leg. They indicated that there is still a lack of knowledge regarding suitable closure models for this application. In some cases empirical correlations originally obtained for one-dimensional codes were used for this multidimensional problem.