Development of a blowdown code for the simulation of steam water separation effects (water level problems) on the basis of the nonequilibrium code DRUFAN

The nonequilibrium lumped parameter blowdown code DRUFAN, used to analyse loss-of-coolant accidents, has been extended to calculate the motion of the mixture respectively, water level inside the reactor vessel. Some important features of this mixture level model are: several mixture level tracks may be simulated either in parallel or in series; mixture level tracks may have branchings up, down or to the side; transition of the mixture level from one control volume into another is possible. The first mixture level calculations with DRUFAN were made with Standard Problem 6. The DRUFAN results were in good agreement with the experimental data