Validation of the CFX4 CFD code for containment thermal-hydraulics

In order to determine the risk associated with the presence of hydrogen in a nuclear power plant containment during a hypothetical severe accident, thermal hydraulic codes are used. Amongst other codes, NRG uses the commercial computational fluid dynamics code CFX4 for this purpose. Models to describe condensation have been implemented by user coding. This paper describes these models. In addition, an overview is given of validation activities with the CFX4 model. Experimental results from the following sources have been used: the Kuhn condensation model; the PHEBUS test facility; the PANDA test facility; and the TOSQAN, MISTRA, and THAI test facilities within the OECD International Standard Problem 47. The CFX4 model predictions are fairly good. Deviations originate primarily from the applied wall treatment. Several recommendations for further development are therefore proposed.