Seismic Analysis On Modified Service Water Pumps

Abstract

At one nuclear power plant, the original essential service water pumps were replaced by another set of pumps with higher capacity. The latter were transferred from another “idle” nuclear power plant. Due to some important differences between the civil construction and because of seismic spectra being different as well, the pumps required modification and, subsequently, requalification. The structural and seismic qualification was based on a three dimensional finite element model. Simulations showed that the replacement pumps would suffer from some structural resonances. Several pump components and the interconnections between them were fortified so as to move the potentially hazardous natural frequencies. After having applied the proposed adaptations, the calculated dynamic behavior was checked by means of an experimental modal analysis and by field performance tests. Finally, the replacement pumps including all structural modifications were implemented onsite during the refueling of the plant.