Background: Reactor internals are important equipments in the reactor coolant system

its structure design needs high reliability in the entire lifetime.Reactor internals have occurred breakdown and the damage event due to flow induced vibrations in the domestic and foreign nuclear power plants

which make immediate influence on reactor safe operation and economic efficiency.Purpose: In this work

the dynamic response of reactor internals-vortex suppression plate and secondary core support structure（SCSS） under the loading from pump induced vibrations and flow induced vibrations are studied.Methods: Based on the finite element model of SCSS

Spectrum analysis and the harmonious analysis are performed

in order to get the response of the structure under flow induced vibrations.Then

the high fatigue of the structure is assessed according to the ASME B&PV Code.Results: The results indicate that alternate stresses of all the components satisfy the limiting value in the correlative requirements.Conclusions: The structure of SCSS could bear the vibration induced from the flow and the pump

and the method used in this article provides the reference for other reactor internals structure analysis like this.