Research on thermal hydraulic characteristics of integrated reactor in natural circulation operation under ocean motions

The modified one-dimensional thermal hydraulic program RELAP5/MOD3.3 was developed to simulate the natural circulation characteristics of an integrated reactor. The ocean motions were realized by adding additional acceleration in the source term of momentum equation. The pressure drop and heat transfer correlations of helically coiled tubes were adopted. The effect of natural circulation characteristics on integrated reactor was studied under rolling, heaving and inclined motions. Simulation results show that the core inlet temperature has no significant change under those three ocean conditions. The average fluctuation value of core mass flow rate is less than the steady-state value and decreases with the increasing rolling angle under the rolling motion. Besides, critical period was observed. In the heaving motion, the average fluctuation value of core mass flow rate is equal to the steady-state value which is different from the rolling motion. The steam equilibrium quality changes slightly in different heaving acceleration. In the inclined condition, the core mass flow rate is decreased with the increasing inclined angle and excessive inclined angle will cause the steam unsuperheated and this may affect the performance of the turbine.