CFD simulation of thermal stratification and mixing in a Nordic BWR pressure suppression pool

• DOI: 10.1016/j.net.2024.07.045
• Publication Date: 2024-07-23T16:36:57Z
• Authors: Xicheng Wang; Govatsa Acharya; Dmitry Grishchenko; Pavel Kudinov
• Keywords: Boiler blowdown; Thermal Stratification; Overpressure; Boiling water reactor; Steam explosion; Natural circulation; Thermal hydraulics; Corium; Stratification (seeds)

Boiling Water Reactor (BWR) employs the Pressure Suppression Pool (PSP) as a heat sink to prevent overpressure of reactor vessel and containment. Steam can be injected into PSP through spargers in normal accident conditions blowdown pipes case loss coolant (LOCA). There is safety limit on maximum temperature at which such steam injection might cause dynamic loads containment structures. The performance pool affected if thermal stratification developed when hot layer grows rapidly while cold remains inactive. Simulation behavior during realistic scenarios requires validated models that sufficiently address interaction between phenomena, systems operational procedures. Direct modeling water long-term transients computationally expensive due need resolve simultaneously smallest space time scales individual bubbles whole PSP. To enable analysis for practical purposes, Effective Heat source Momentum (EHS/EMS) have been proposed avoid steam-water interface. This paper aims implement mechanistic approaches previously by authors simulation transient mixing phenomena induced Nordic BWR latest version EHS/EMS using 'Unit cell' approach has against integral effect tests applied plant simulations. Several with boundary corresponding postulated sequences were simulated investigate possibility development effects activation different (e.g., pipes, high momentum nozzle) behavior.