Seismic evaluation of the Department of Energy gaseous diffusion plants

Seismic evaluations of structures have been recently performed at the US Department of Energy (DOE) Paducah and Portsmouth Gaseous Diffusion Plants (GDPs). These evaluations have been performed to satisfy DOE Order 5480.28, Natural Phenomena Hazards Mitigation. The DOE order requires that structures, systems, and components at DOE facilities be evaluated using a graded approach. In order to perform the seismic evaluations, probabilistic and deterministic seismic hazard studies were performed to define the evaluation basis earthquake (EBE). Additionally, to capture current structural configurations, criteria were developed, based on a sampling approach, for experienced structural engineers to use in walkdowns. The seismic evaluations of the structures were performed using three-dimensional dynamic models with the response spectra modal analysis approach. From these analyses, structural capacities (high confidence of low probability of failure) were determined and compared to the EBE level. These evaluations are presently being reviewed by DOE in considering the remaining life of the facilities and to determine if modifications might be necessary