Study on Transient Hydraulic Load of Reactor Coolant System under the Condition of Reactor Coolant Pump Rotor Seizure

In order to truly reflect the transient internal flow transition process and hydraulic load impact of the reactor coolant system under accident conditions, a high-precision three-dimensional closed system transient flow calculation method was established for the HPR1000 reactor and its primary system, and the pressure wave oscillation law and transient hydraulic load characteristics of the pipeline of the reactor and primary system during the transition process were obtained. The results show that: in the end of the reactor coolant pump rotor seizure, the flow rate at the reactor coolant pump outlet decreased to 81.3% of that in stable operation. During the transition process of the rotor seizure, the maximum pressure peak value in the system pipeline is located at the inlet section of the reactor coolant pump, which is 16.00 MPa; the minimum pressure valley value is located at the outlet section of the reactor coolant pump, which is 15.01 MPa. Finally, the pressure of each monitoring point in the system tends to the reference pressure of 15.50 MPa. Under the dual influence of the piping layout of reactor coolant system and the rotor seizure accident of reactor coolant pump, the fluid velocity of each section shows obvious uneven distribution, and obvious eddy currents occurs. The variation rule of hydraulic load on each wall of the system is consistent with the variation rule of system pressure pulsation. The maximum load force peak is located at the W3 wall at the first elbow of the transition section, which is 3.163×10⁶ N; the minimum load force valley value is located at the W12 wall of the elbow at the inlet of the reactor pressure vessel, which is 9.125×10⁵ N. This numerical prediction method can provide technical support for the design and safety assessment of the reactor coolant pipeline under the condition of the reactor coolant pump rotor seizure.