Gross design and construction errors, and seismic risk studies

The seismic risk estimates and seismic margin assessment for nuclear power plants should consider the potential effects of design and construction errors. These errors generally modify the component responses and fragilities. The concern with design and construction errors is that they may simultaneously affect a large number of systems and structures and negate the possible benefits of redundancy. A methodology for treating the effects of gross errors in seismic PRA and seismic margin studies consist of enumeration and classification of errors, sensitivity studies to identify significant errors, collection of data on errors and incorporation into the margin and risk estimation.