Thermal Stratification and Mixing in a Large Pool Induced by Operation of Spargers, Nozzles, and Blowdown Pipes
Ignacio Gallego-Marcos, Walter Villanueva, Pavel Kudinov,
In a Boiling Water Reactor, steam released from primary coolant system is condensed in the pressure suppression pool. Thermal stratification in the pool affects pressure suppression capacity of the pool. Heat and momentum sources generated by the steam condensation define pool behavior. Direct Contact Condensation (DCC) of steam present a challenge for contemporary modeling tools. In previous work, the Effective Heat Source (EHS) and Effective Momentum Source (EMS) models were proposed to simulate development of thermal stratification or mixing induced by steam injection into a large pool of water. These models are computationally efficient and sufficiently accurate in resolving the effect of DCC phenomena on the large scale pool circulation.
In this work, we present the validation of the EHS/EMS models for spargers and mixing nozzles. Validation results with EHS/EMS implemented in GOTHIC and ANSYS Fluent show a good agreement in comparison to the PPOOLEX experiments. The scaling of the PPOOLEX experiments with mixing nozzles was done to preserve prototypical ranges of injection conditions and pool regimes. The experimental results are similar to the pre-test analysis data.
An implementation of the EHS/EMS models for analysis of steam injection into a containment pool was developed. The results of analysis provide a realistic pool behavior. Modeling of direct steam injection showed that without EHS/EMS models the results are severely affected by numerical instabilities.