A theoretical study of cyclon-effect in PWR downcomer during a LOCA blowdown

The current strategy based on the use of so-called cross-junction, allows partial modeling during blowdown episodes driven by larger-scale (flow features such as helical profile) in downcomers nuclear reactors. However a subtle but significant effect may appear by the combined action of two factors: on the one hand high azimuthal flow, on the other hand the intrinsic curvature of downcomer, and additionally in presence of a two-phases (vapor-liquid) a cyclon-effect can manifest. The present paper is a theoretical analysis of a possible cyclon-effect during blowdown episodes that allows a qualitative estimate of the impact on the calculations.