Study On Fluid-solid Interaction Transient Characteristics Of Nuclear Reactor Coolant Pump Under Shaft-stuck Accident Condition

Reliability is one of the primary factors for the safe operation of nuclear power plants.As the main pressure-bearing equipment and the only power rotating machinery in the reactor coolant system(RCP system),the nuclear main pump is regarded as the "heart" of the first loop,which plays an important role in the safe and reliable operation and the mitigation under accident conditions of the RCP system.To ensure the safety of nuclear power plants to a large extent,it must be ensured that the nuclear main pump could withstand the tests of various extreme accident conditions while meeting normal operation.The Shaft-stuck accident of the main pump is a typical extreme accident condition,which will have a huge impact on the first loop and the nuclear main pump.It will cause irreversible damage to the equipment and the system.In more severe cases,the fuel rods departure from nucleate boiling(DNB)and core burnout would occur,causing large-scale nuclear leakage which brings a catastrophic disaster to human and the environment.Therefore,the research on the hydrodynamic and structural dynamic characteristics of the nuclear main pump under the Shaft-stuck accident has important engineering significance and academic value.This paper takes AP1000 nuclear main pump as the research object,and uses the combination of theoretical analysis,experimental research and Bidirectional fluid-solid interaction calculation to study the hydrodynamic and structural dynamic characteristics of the nuclear main pump.Focusing on the analysis of the four-quadrant transition process of the nuclear main pump under the Shaft-stuck accident,the author explores the relationship between the transient flow and the structure of the nuclear main pump under the accident,which provides a reference for the design and manufacture of the nuclear main pump.The main research content is as follows:1.Aiming at the particularity of Shaft-stuck accident condition,a set of transient test system for Shaft-stuck accident is specially designed and constructed.The model prototype of AP1000 nuclear main pump is used as the research object for simulation under the Shaft-stuck accident condition.The transient laws of the performance parameters such as flow,speed,torque,and head are obtained under different Shaft-stuck degrees.The four-quadrant transition process including normal pump operating condition,special pump operating condition,positive flow braking operating condition and reverse turbine operating condition under the Shaft-stuck accident are mainly analyzed together with the variation law of pressure pulsation during transient transition.2.The fluid-solid interaction model of the nuclear main pump is established,and the hydrodynamic and structural dynamic characteristics of the nuclear main pump under different operating conditions are studied using FSI method.By comparing and analyzing the effects of fluid-solid interaction on the internal flow regularity and external characteristic of the main pump under different operating conditions and the corresponding modal shape of the rotor with and without prestress,the stress and deformation distribution of the main pump rotor is obtained,which provides the basis of subsequent analysis and comparison for the study of the transient characteristics under Shaft-stuck accident.3.Using the three different sets of flow and speed curve under the different Shaft-stuck degrees obtained by the experiment,the corresponding boundary conditions are established by MATLAB software.The Bidirectional fluid-solid interaction calculation for the transient flow of the nuclear main pump Shaft-stuck accident is carried out for the first time,and the reliability is verified by the test results,which reveals the influence on the internal flow mechanism of the nuclear main pump under Shaft-stuck accident conditions with different degrees.4.Based on the transient Bidirectional fluid-solid interaction mathematical model,the rotor dynamics during the transient process under Shaft-stuck accident condition is analyzed.The variation laws of radial load,axial load,stress distribution,transfer transition and transient dynamic stress of the main pump impeller in the Shaft-stuck accident transient process are displayed,providing the reference for the subsequent design,manufacture and test of the nuclear main pump.