VALIDATION OF NUMERICAL MODELS FOR SEISMIC ANALYSIS OF SUBMERGED COMPONENTS IN ADVANCED REACTORS

Analytical solutions have and are being used for designing submerged components in different engineering disciplines, including naval, mechanical, nuclear, and civil. However, the solutions cannot be applied to complex structural shapes and boundary conditions or multiple directions of moderate-to-severe dynamic excitation such as earthquake shaking. Seismic design of submerged reactor internals is critical in advanced reactors. As advanced reactor designs move towards standardization of equipment to reduce associated costs, design and risk assessment calculations will have to rely on the use of verified and validated numerical models that are capable of capturing the interaction of internals with the surrounding fluid (fluid-structure interaction: FSI) over a wide range of three-component earthquake shaking. Physical data that could be used for validating such numerical models are not available. An experimental program was performed on a 6 degree-of-freedom earthquake simulator at the University at Buffalo to generate data for supporting validation of numerical models for FSI in commercial finite element codes. A scale model of a base-supported reactor vessel and simplified representations of reactor vessel internals (RVIs) were tested to generate hydrodynamic response histories for a range of seismic inputs. Added mass, added damping and coupling effects (between submerged components) were investigated and strain and acceleration response histories for the submerged components were generated. The effects of seismic (base) isolation on the dynamic responses of RVIs were investigated using numerically generated input motions simulating a virtual isolation system. This paper describes the experimental program and presents a validation study performed in the finite element package, LS-DYNA.