Full-scale numerical study on the flow characteristics and mal-distribution phenomena in SG steam-water separation system of an advanced PWR

The steam-water separation system is of great importance to ensuring the steam quality in a PWR UTSG. In the present work, the full-scale three-dimensional CFD analysis is performed to study the mal-distribution steam flow in the system using ANSYS-FLUENT platform. A full-scale model of newly-designed PWR is established and all the sophisticated structures of 19 swirl-vane separators are modeled. Besides, the porous medium model is adopted to simplify the steam flow inside the dryers because of the complex structure of wave-type vanes. Employing CFD methodologies, detailed flow characteristics in the whole system are captured, especially the velocity fields of steam at inlets of 7 dryer units. The outcomes show that the maximum unit-area mass-flow rate appears at the entrance of #4 dryer which is in the central part of dryers. In addition, the maximum entry velocity is 2.136 m/s, while the velocity is decreased to 1.049 m/s, lower than the critical velocity, with the application of an orifice plate assembly with the perforation in different calibers on the plate. Also, the effect of the separator down-comer on the mal-distribution phenomenon is also analyzed. In general, the current work could be expected to be a basis for the future optimization on moisture separation components in the steam generator.