Numerical analysis on the effect of flow rates and jet diameter in rewetting vertical nuclear fuel bundle with jet impingements

Highlights: • CFD analysis of two phase flows for AHWR fuel rod bundle is modeled. • Rewetting behavior with changes in flow rate and changes in jet diameters are analyzed numerically. • Increasing flow rate and jet diameter improved the rewetting performance. • Sputtering causes rewetting temperature to be higher than the initial wall temperature of the nuclear fuel rod. - Abstract: Transient two-phase numerical analysis on the rewetting of vertical nuclear fuel rod bundle has been carried out. In the present investigation, the working domain was framed with single sector (1/6th part) of the Advanced Heavy Water Reactor (AHWR) fuel assembly. The numerical results were validated with experimental data. It was found that the SST turbulence model validates fairly well for predicting the rewetting phenomena. Numerical investigation has been performed with varied range of flow rates (2–4 lpm) and jet diameter (2–4 mm). It was observed that for a particular numerical set of parameter, wet front progresses faster towards radially downward. The wetting delay at any inlet section is negligible. In the position away from the inlet section, the uneven and irregular sputtering of coolant was observed. The vapor accumulation increases resistance between the coolant and the heated surface. The large accumulation of vapor leads to heating up of rod wall temperature. In the respective location point, it was observed that as the flow rate increases the wetting delay and rewetting temperature reduces. The rewetting progresses have been observed more significantly with jet diameter.