Simulation of RD-14M Flow Stability in TRACE

Abstract

The figure-of-eight loop design is susceptible to out-of-phase flow oscillations when two-phase flow is present if the loops involved are isolated. This is prevented in some CANDU designs by installing an interconnect pipe between the two outlet headers in the loop. However, the ability of computer thermalhydraulic models to predict figure-of-eight oscillations is important because such codes are relied upon to demonstrate stability even for newer CANDUs with interconnects. The RD-14M test loop is a full height but scaled test facility that is used extensively for computer code validation, and experiments have been performed to evaluate this flow instability along with header interconnect designs. A TRACE model of the RD-14M test loop was adapted to simulate these experiments. The simulations could qualitatively reproduce the flow instability, showing their potential for simulating these events, but were more stable compared to the experiments and were sensitive to the nature of the perturbation.