Effects by Sea Wave on Thermal Hydraulics of Marine Reactor System

Abstract

This paper describes the experiments of the first Japanese nuclear ship ‘Mutsu’, to investigate the effects of sea wave on the thermal hydraulics of marine reactor system while cruising through various sea conditions. The experimental data were analyzed in time-domain by RETRAN-02/GRAV code. This code was modified so as to simulate the ship motion effect on reactor thermal hydraulics. The data were also analyzed in frequency domain by Blackman Turkey method for the calculation of the spectrum and response function. The experiments involving ship maneuvering were performed by cruising on different wave heights, as well as wave directions in the northern Pacific ocean. From the experiments, vertical acceleration due to ship motion was found to induce direct variation of water levels in the SGs and the pressurizer. The water level variations were largest in the head wave, but smallest in the following wave. On the other hand, the following wave caused greater variation of the reactor power when the feed back control for the shaft revolution speed was used. Mechanism of response of water levels and reactor power with respect to the external forces are discussed. The response function (gain or phase shift) of reactor power to steam flow variation by the wave during cruising at rough sea condition was found to be roughly that without the work of control rod.