IMPLICIT COUPLING OF FLUID-DYNAMIC SYSTEMS - APPLICATION TO MULTIDIMENSIONAL COUNTERCURRENT 2-PHASE FLOW OF WATER AND STEAM

The German ATHLET thermal-hydraulic system code has been coupled with a two:dimensional module simulating the downcomer of a pressurized wat er reactor To be efficient, this coupling had to be implicit in time. The countercurrent two-phase flow of water and steam in the downcomer of a reactor pressure vessel was simulated using this combined code sy stem. The implicit coupling procedure, as well as the results of a pos tcalculation of an experiment of the Upper Plenum Test Facility are de scribed.