Study on the complete rotational characteristic of coolant pump in the gas-liquid two-phase operating condition

Abstract

One of the most serious accidents of reactor coolant pump was the loss of coolant accident (LOCA) which may happen in any part of component of reactor system or coolant liquid circulation pipe. During the accident, the pump will be in a gas-liquid two-phase mixing operating state. The paper researches the full-flow hydraulic characteristics of forward rotation and reverse rotation of reactor coolant pump in the gas-liquid two-phase operating condition, respectively, in many operating conditions, such as the forward-rotation positive-flow, the forward-rotation negative-flow, the reverse-rotation positive-flow and the reverse-rotation negative-flow, and analyzes the laws of gas volume distribution in the overall fluid area with different gas fractions in different operating conditions using CFX analog computation method. The research finds with different gas fractions, the reactor coolant pump’s torque complete-characteristics curve and head complete-characteristics curve show basically the same changing laws, i.e., the pump’s operating torque was directly proportional to water head, and when the two-phase flow’s gas fraction reaches 0.40, the pump’s safe flow interval was only 0.087Q0, basically losing the ability carrying safe flow to reactor core; in different gas fraction conditions, the homogeneous distribution of gas phase component in the fluid area was mainly related to the operating condition of pump, and when the volume flow rate deviates from the designed operating point, the fluid medium’s gas phase and liquid phase will separate to some extent, and in the same operating condition with different gas fractions, the distribution of gas fractions in the fluid area shows basically the same laws.