Natural circulation characteristics of a marine reactor in rolling motion

Abstract A series of single-phase natural circulation tests in a model reactor with rolling motion was performed, in order to investigate the natural circulation characteristics of a marine reactor in a stormy weather. It was found that the loop flow rate in each leg changes cyclically with the rolling angle due to the inertial force of the rolling motion. As the rolling period becomes shorter, both the amplitude of the loop flow rate oscillations becomes larger and the phase lag between the rolling angle and loop flow rate oscillations becomes larger. On the contrary, the core flow rate does not oscillate, though its value changes with the rolling period. Its change correlates well with both the Reynolds number for rolling motion and the Rayleigh number, and it is considered to be caused by the change of the thermal driving head and pressure loss through the loop. In order to simulate core flow rate change with the rolling period, a simple one-dimensional analytical model was proposed. The calculated results agree well with the experimental results, and its verification is demonstrated.