Investigation On Characteristics Of Natural Circulation Under Rolling Condition

Thermal-hydraulic characteristics of either ship-based reactor or floating nuclear power plant are influenced by the ocean conditions such as inclination and rolling,especially when primary loop operates in the mode of natural circulation.Based on system code RETRAN-02,the conservative equations were modified so that the influences of typical ocean conditions were incorporated in order to analyze the effects of rolling motion on natural circulation.The model for some experimental loop was set up and the modified code was validated through the comparison of the simulation results against the experimental results for single phase natural circulation under inclination or rolling motion conditions.For the loop,both inclination and rolling motion may change the elevation difference and rolling motion may also introduce additional pressure drop for the natural circulation.Thus,the study on the influence of inclination on the characteristics of the natural circulation was conducted at first.The ways in which the change of elevation difference may influence the mass flow rate of the natural circulation were concluded by means of numerical simulation and theoretical analysis.The case study was performed for a selected combination of thermal-hydraulic and rolling motion conditions.The mechanism of the effects of rolling motion condition on the natural circulation was analyzed.The separate effects of thermal-hydraulic parameters,such as heating power of heated section and the local coefficient at the inlet of the test section etc.,were numerically simulated and analyzed under the same rolling motion condition.Furthermore,the influences of the amplitude,period and maximum angular acceleration on the variation of the mass flow rate were studied in terms of additional pressure drop,elevational pressure drop and phase difference.Moreover,the study on the shift of the axis of the rolling motion was also performed.The influence of rolling axis position was explored by comparing flow rate under rolling and pitching condition.For the characteristics of the natural circulation in two-phase flow,the comparisons were made at different heating power under either normal or typical rolling motion conditions.The parametric study was carried out afterwards.It was found that the influence of gravitational pressure drop was more dominant than the additional pressure drop in terms of flow rate fluctuation in the span of the study.When the rolling period was short enough,the phase difference between flow rate and rolling angle had significant influence on the amplitude of the flow rate fluctuation.The amplitude of the flow fluctuation decreased with the decrease of rolling period when the maximum angular acceleration remained the same.The change of the heating power in the test section or the shift of the rolling axis position parallel had little influence on the additional pressure drop in the range of cases investigated.Intermittent flashing and saturated boiling might be intensified and the complicated instability phenomenon might occur under rolling condition.