Numpool Summary Report

Numerical methods for analyzing pressure suppression pools in boiling water reactors are developed. Some of the first experiments performed with the PPOOLEX facility are analysed with computational fluid dynamics (CFD) and Fluid-Structure Interaction (FSI) simulations. PPOOLEX vessel Is a scaled-down model of a boiling water reactor containment with pressurized drywell and wetwell compartments. The compartments are connected with a vent pipe, whose outlet was submerged in a water pool of the wetwell. In the first experiments, air was blown into the drywell of the pressurized PPOOLEX vessel. The experiments and modelling are continued with steam discharges.Simulation of an air discharge was performed by using the Fluent CFD code. The pressurization of the drywell, clearance of the vent pipe and pressurization of the wet well during the first tens of seconds of the experiment are resolved. The bubble dynamics at the outlet of the vent pipe is studied in some detail. The results are compared to measurements in the PPOOLEX experiment.FSI analyses of the POOLEX and PPOOLEX experiments are performed, where the Star-CD CFD code and ABAQUS structural analysis code are coupled with MpCCI software. A linear perturbation method is used for preventing numerical instability which occurs in the pool simulations with explicit FSI coupling. The calculations shows that FSI may have to be accounted for in simulating blowdown in pressure suppression pools.