Effect of rolling motions on the single and two-phase pressure drop in annulus channel with helical-finned heater for floating nuclear reactor

Abstract

Interest in utilizing nuclear power in the maritime environment has been growing. However, the limited availability of research on floating nuclear power plants poses challenges to support the design and safety evaluation process. To address this gap, experimental platforms were developed in Seoul National University to conduct thermal–hydraulic experiments under simulated rolling conditions. To replicate pressurized water reactor conditions, a compact experimental loop using refrigerant R134a as a simulant fluid was designed and mounted on the rolling platform. An annulus geometry test-section was utilized, to imitate the rod-centered subchannel of the reactor core. In this study helical-finned heater rod was used representing one of the potential fuel rod geometries for tight lattice cores. During the experiments, motion-driven flow fluctuations were constrained within ±1 % range to neglect the flow fluctuation effect on pressure drop. The experimental results confirmed that pressure drop is affected by motion conditions. Under inclined conditions, the pressure drop decreased, primarily due to the reduction in elevation between the test-section inlet and outlet. On the other hand, under rolling conditions, the pressure drop fluctuated, driven mainly by oscillations in acceleration, including both gravitational and centrifugal components. Furthermore, the range of pressure drop fluctuations was found to exceed what could be attributed solely to acceleration fluctuations. This additional increase was estimated to result from frictional pressure drop fluctuation occurring under the rolling conditions.