Measurement of flow-induced pressure variation in a scale-down SMART model

A scale-down SMART reactor model was constructed to evaluate flow-induced pressure variation under normal operating conditions. The flow rate and number of operating pumps were varied, and pressure fluctuations along the reactor internals surface of the model were measured by pressure transducers. The measured transient pressure was separated into the mean and fluctuating pressure, which was evaluated by analyzing the data of two distinct regions. Specifically, the pressure obtained at frequencies less than 10 Hz was analyzed separately from those obtained at frequencies greater than 10 Hz. In the present study, the mean pressure distribution was dependent on the pressure loss due to the skin friction and changes in the static pressure due to height level differences at the measuring points. The mean pressures were similar, regardless of the location of the operating pump, because the fluid was fully mixed in the upper shell. The normalized mean pressure ratio, excluding the hydrostatic pressure change, kept constant regardless of the flow rate and number of operating pumps. It was observed that the RMS of the fluctuating pressure at frequencies less than 10 Hz did not depend on the measuring points for all of the surfaces of the model. And, periodic pressure fluctuation generated by the inlet region is not reachable to the fuel assembly region because of the structural arrangement of SMART.