Margins from dynamic FEM analysis of cracked pipe under seismic loading for the DOE new production reactor

This paper presents a comparison of fracture predictions using typical LBB analyses (peak stresses from response-spectrum analysis) with dynamic nonlinear cracked-pipe time-history calculations for seismic loading on the postulated DOE New Production Heavy-Water Reactor. The results showed that the fracture would not be instantaneous, and moreover there was a margin of more than five on the failure load from the typical LBB analysis and the nonlinear cracked-pipe time-history analysis. This margin occurs due to the plasticity not allowing the peak elastically calculated loads to be developed, and the short time duration of the high amplitude loads. Hence, significant margins can be realized from such an analysis procedure, which are well above the applied safety margins on load in LBB regulatory procedures