A generic study of phenomena affecting two-phase mixing in BWR suppression pools during passive decay-heat removal

The paper describes some advancements made in the use of two-phase Computational Fluid Dynamics (CFD), sometimes called Computational Multi-Fluid Dynamics (CMFD), techniques in simulating the phenomena occurring in pressure suppression pools in Advanced Boiling Water Reactors which utilise passive containment cooling systems. An interface tracking procedure based on the Level-Set approach has been implemented into a commercial CFD code with the specific purpose of providing a computational environment for the development of suitable models to describe the inter-phase mass and energy transport processes which would take place when a large gas bubble is discharged into a pool. Details of the implementation and validation of the tracking algorithm are described, together with some illustrations of how the method is utilised. The paper also reports on the progress which is being made in the use of Large-Eddy Simulation (LES) to describe turbulent mixing in such plumes. The research efforts are aimed at ultimately combining the approaches to develop a mechanistic tool for fully describing the pool dynamics and steam condensation phenomena