Development of computationally effective models for simulation of steam injection effects on the pool stratification and mixing

Abstract

Steam injection through blowdown pipes and spargers into a large water pool, also known as Pressure Suppression Pool (PSP), is employed in Boiling Water Reactors (BWRs) to prevent containment overpressure. Thermal stratification in the pool results in an increased pool surface temperature compared to a mixed pool condition, leading to higher containment pressure. Therefore, adequately validated predictive capabilities for modeling of the pool behavior are essential for the safety analysis of containment performance. The thermal behavior of the pool (e.g. thermal stratification or mixing transient) depends on the interplay between the heat and momentum sources induced by direct contact condensation of steam. Computational efficiency of the models for the simulation of the long transients in the large-scale pools is critical, especially for the quantification of uncertainties. The Effective Heat Source (EHS) and Effective Momentum Source (EMS) models have been developed to represent the impact of steam injection on the pool while avoiding the detailed simulation of steam-water interface dynamics, which is a computational challenge in itself. These models are compatible with any Computational Fluid Dynamics (CFD) code using a single-phase solver. In this work we further develop the EHS/EMS models using (i) new EMS model correlation based on the latest results from Separate Effect Test (SEF-POOL) facility; and (ii) Condensation-Induced Turbulence (CIT) model calibrated against integral pool experiments conducted at PANDA, PPOOLEX, SJTU, and HEU facilities under a wide range of steam injection conditions. The good agreement of the global pool behavior and local flow characteristics demonstrates that the proposed models can provide an adequate prediction of the relevant phenomena.