Effect of eccentricity on radial force and cavitation characteristics in the reactor coolant pump

Abstract

Nuclear reactor coolant pump as one of the most critical equipment is the only one rotating equipment in first loop system of nuclear power plant. Due to the asymmetric structure of the pump body, especially the existence of outlet segment lead to a certain of radial force, the magnitude of radial force directly affects the work stability of the reactor coolant pump. The nuclear reactor coolant pump could stability work under those transient complex conditions is an important index of its performance. To study the cavitation characteristics and radial force of reactor coolant pump on transient cavitation, a prototype pump and those exhibiting different gravity center offsets are analyzed numerically with CFD software ANSYS CFX by employing RNG k-? model and two-fluid two-phase flow model. Through the experiment-combined simulation, the variations of cavitation characteristics and radial force of the reactor coolant pump under different eccentricities are characterized. As revealed from the results, the flow characteristics of the internal flow field of the nuclear main pump change after the axis is offset by different distance. The influence of eccentricity on the cavitation of the nuclear main pump is mainly manifested at the impeller inlet from cavitation inception severe cavitation. When the eccentricity is 5 mm, the cavitation performance is improved. The effect of eccentricity on the radial force of impeller is reflected in the variation of force direction. Compared with other plans, the radial force is superior in transient cavitation under the eccentricity of 5 mm.