CFD and FEM modeling of blowdown of gas into pressure suppression pool
Timo Pättikangas, Antti Timperi, Qais Saifi,
Computational Fluid Dynamics (CFD) and Finite Element Methods (FEM) used for modelling pressure suppression pool during a postulated Large-Break Loss-Of-Coolant-Accident (LB-LOCA) are summarized. The CFD methods used for the simulation of the early stage of the LB-LOCA are applied to a sector model of a BWR. Fluid-Structure Interaction (FSI) calculations are performed for the PPOOLEX test facility and a sector model of BWR. Acoustic FEM method is applied to a model of BWR containment.
FSI calculations using explicit and implicit two-way coupling of Star-CCM+ and Abaqus codes are performed. The implicit simulations enabled the use of fairly large time steps, even when the ratio of structure density to fluid density was decreased such that the explicit solution became severely unstable. Simulations of the early non-condensable phase for a realistic BWR containment showed stable calculations also with explicit coupling when compressible water was assumed.
Simulations of a boiling water reactor (BWR) containment with an acoustic FSI FEM model were performed. The BWR containment with 16 vent pipes was loaded stochastically through the pipes. Different statistical cases were considered for applying the loads. A normal distribution curve with the mean value and standard deviation was developed for each varied parameter. The results from different statistical cases were compared.
The CFD model for Large Interfaces in two-phase calculations is reviewed and the use of the model for large gas bubbles in pressure suppression pool is discussed. The early stage of LB-LOCA is calculated with a 90° sector model of BWR containment.
Condensation pool, pressure suppression pool, BWR, CFD, fluid-structure interaction, FSI, chugging, LOCA