Evolution of structural reliability methodology as applied in major nuclear risk assessments

The evolution of the handling of structure and mechanical component reliability in the seismic portions of five major nuclear risk assessments is reviewed. Three of these risk assessments are complete and published (the Reactor Safety Study, the Clinch River Breeder Reactor Plant Safety Study, and the Diable Canyon License Application Amendment 52), while the last two are still in progress (the Oyster Creek Probabilistic Safety analysis and the Seismic Safety Margins Research Program). The approaches and conclusions (to the extent available) are summarized and compared, demonstrating important advances in the sophistication of performing structural reliability analyses over a span of about eight years of major risk assessment effort. (orig.)