Implementation and validation of downcomer and upper tie plate CCFL correlations in a two-fluid code

At the moment the two-fluid system code APROS has CCFL (Counter Current Flow Limitation) correlations that are designed only for a single pipe or for bundle geometry. In the reactor pressure vessel the downcomer and the upper tie plate of the core are components that call for special CCFL correlations. In the present task the Glaeser CCFL correlations for a downcomer and an upper tie plate have been implemented in the code. The implemented correlations have been validated by calculating several downcomer and upper tie plate test cases of the UPTF (Upper Plenum Test Facility). In the tests the steam flow, the emergency core cooling flows, injection locations and the pressure levels were varied. In the validation the UPTF facility has been modeled with a nodalization, which is normally used in the corresponding calculations. Because the calculation results do not depend merely on the CCFL correlations the new Kutateladze coefficients of the Glaeser correlation had to be specified during the validation. With the selected coefficients, good, slightly conservative results were obtained. In the paper the work done with the correlations and the results of the validation calculations are described.