A computational investigation is undertaken into the role of buoyancy in a PWR boron dilution transient following a postulated Small Break Loss of Coolant Accident (SB-LOCA). In the scenario envisaged there is flow of de-borated and relatively high temperature water from a single cold leg into the downcomer; flow rates are typical of natural circulation conditions. The study focuses upon the development of boron concentration distributions in the downcomer and adopts a 3D-unsteady formulation of the mean flow equations in combination with the standard high-Reynolds-number k-ε turbulence model. It is found that the Richardson number (Ri = Gr/Re2) is the most important group parameterizing the course of a concentration transient. At Ri values characterizing a ‘baseline’ scenario the results indicate that there is a stable, circumferentially-uniform, descent through the downcomer of a stratified region of low-borated fluid. Qualitatively the same behaviour is found at higher Richardson number, although at Ri values of approximately one-fifth the baseline level there is evidence of large-scale mixing and a consequent absence of concentration stratification.
- Nuclear Engineering Division
Parameterization of Buoyancy Effects in Generic PWR Boron Dilution Scenarios
Galindo-Garci´a, IF, Cotton, MA, & Axcell, BP. "Parameterization of Buoyancy Effects in Generic PWR Boron Dilution Scenarios." Proceedings of the 14th International Conference on Nuclear Engineering. Volume 4: Computational Fluid Dynamics, Neutronics Methods and Coupled Codes; Student Paper Competition. Miami, Florida, USA. July 17–20, 2006. pp. 225-234. ASME. https://doi.org/10.1115/ICONE14-89480
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