Finite Element Modal Analysis And Research On Modal Test Technology Of Reactor Internals

Comparing to thermal power,nuclear power station has advantages of lower carbon emission,cleaner and lower operation cost,but its safety is widely concerned.According to nuclear safety regulations,nuclear power equipments should pass the test of detection and get verification before coming into commercial use to ensure the safety.Reactor internals like pressurized water reactor metal reflector(or core shroud),control rod guide tube and others,are mainly used to support the core structure,ensure the alignment of the fuel assembly,guide the motion of control rod bundles,and allocate the coolant flowing through the fuel.High-speed coolant in reactor internals may induce vibration when flows around or turns,causing material fatigue damage,connector loosening or fracture and parts wearing,effecting the movement of control rods and leading to shutdown accidents of nuclear power stations.It is a very important task to avoid flow induced vibrations in the design of internals under full conditions of the reactor.Vibration mode tests of pressurized water reactor is very important to test vibration natural frequencies and modes of reactor internals,check data simulation results and provide measured datas in safety evaluation of flow induced vibrations.The successful implementation of vibration mode tests with great difficulty because of the huge structure and overweight of the large-scale nuclear power unit has initiative meanings.In this thesis,a 3D model of one reactor in domestic nuclear power station with internals of metal reflectors,control rod guide tube and instrument conduit support column,etc.was created with Solid Works software.The model was introduced into ANSYS,a computing platform of structural dynamics,to calculate natural frequencies of each component of the first 10 orders and vibration modal parameters after mesh generation,setting performance parameters of materials and constraint conditions getting from vibration mode tests of real components and finalized mesh generation after grid sensitivity analysis.In view of the ultra-large structure of metal reflectors and super-heavy structural elements,a force hammer with maximum impulsive force of 200 k N was developed.In order to get exciting points with good exciting vibration and vibration response,and measuring points of vibration,a SIMO(single input/multi output)vibration modal testing system of internal components with 16-channel synchronous measurements was constructed,and ME’scope,a modal identification software is used.Good effect exciting point and good vibration response measuring points are designed,based on the dynamic numerical results of reactor internals.The lowest natural frequencies and corresponding mode shapes modal parameters were obtained from the vibration mode test of metal reflector,control rod guide tube and instrument conduit support column,first time in china on the manufacturing field.In the metal reflector,56 measuring points of tangential vibration and radial vibration and were arranged.The whole vibration mode distribution were obtained with ME’scope modal identification software,the test showed that the force hammer was enough to excite excited vibrational vibrations.By comparisons of results between the numerical analysis and the experimental model,we found that deviations of the relatively simple structure of the instrument conduit support column,T-shaped support column,and control rod guide tube were limited to 4.4%.The deviation of metal reflector with a complicated structure were limited to 7.3%,except frequencies of the first-order(elliptic bulge on the plane side)and second-order(elliptic bulge on the curved side)of the metal reflective layer,which are mainly caused by inconsistent constraints.The modal parameters obtained through the modal test can be used to guide numerical modal analysis,and verified the finite element model for numerical analysis effectively and ensured the correctness of the finite element model for flow-induced vibration analysis of reactor internals.The methods and results obtained in this thesis will provide important reference for subsequent similar analysis.