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Steam condensing jet oscillation and breakup in a BWR pressure suppression system


Overview: Safety Relief Valves (SRVs) are utilized also in certain PWR containment systems, e.g. the Korean NPP. Steam discharge from the Pressurizer through the SRVs is routed into the In-Containment Refueling Water Storage Tank (IRWST) where it is condensed. Following BWR practice, the discharge points are fitted with quenchers (multi-hole discharge devices) to reduce the effects of the violent condensation of steam and the amplitude of pressure oscillations and corresponding loads in the IRWST pool.

The challenge: Full-scale quencher tests are rather expensive. So, there is a strong incentive to develop and validate (using published test data at smaller scales) computational techniques capable of providing the answer in a relatively short time. The phenomena of interest are the condensation of the multiple jets emerging from the quencher at high speed (under compressible conditions with possibility of shocking), their interactions, the pressure oscillations they are producing, as well as the overall pool behavior.

TransAT Solution: TransAT can be used to study the global circulation patterns in the pool that affect the flow conditions around the quenchers (upper image). The sonic or near-sonic steam jets from the quencher holes can be modeled using a variety of techniques such as interface tracking or the mixture model and LES for turbulence (results shown in panels 2&3). Compressibility effects and the pressure oscillations produced by the condensing jets can be computed, including the capturing of shocks. The compressible high-speed model capable to capture shocks in TransAT is implemented within the multiphase flow context, which is a rather unique feature.

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Dr Chidu Narayanan
ASCOMP Switzerland
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