Conference Paper

Improvement of Swarm Rise Region Modelling in SPARC-90 Pool Scrubbing Code

October 2024

Conference: Transactions of the Korean Nuclear Society Autumn Meeting
At: Changwon, Korea

Authors:

Independent Researcher

Pool scrubbing is an important safety measure for mitigating severe accidents in nuclear reactors, including Small Modular Reactors (SMRs). This process involves complex interactions between hydrodynamic, thermal, and chemical processes. As gas bubbles containing fission products move through a water pool, radioactive substances are effectively trapped, preventing their release. However, current pool scrubbing codes such as SPARC-90, BUSCA, and PIAERO have limitations due to simplifying empirical assumptions, which can lead to underestimation of the Decontamination Factor (DF), a measure of the process effectiveness. One major limitation is the inadequate representation of bubble dynamics, where codes use a constant bubble diameter in the swarm rise region, despite the DF depending on the surface area-to-volume ratio of the bubbles. Additionally, factors such as the effective residence time of aerosols and net deposition velocities are also influenced by the size of individual oblate bubbles. To address these limitations, a new bubble size model has been proposed for the rise region, using a mean bubble diameter correlation to calculate the average bubble size at any height along the region. This model has been implemented into the SPARC-90 poolscrubbing code, resulting in a more mechanistic model that can be adopted by other pool scrubbing codes.

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Last Updated: 18 Nov 2024