Walkdown criteria for evaluating seismic margin in nuclear power plants

The goal in performing a seismic margin assessment is to demonstrate that a single and possibly one alternate safe shutdown functional path will survive the seismic margin earthquake. Major emphasis is placed upon the use of systems engineers to define the candidate shutdown paths and existing generic ruggedness data to screen components from requiring detailed analytical evaluations. Experienced engineers are used to conduct a thorough walkdown of the plant. A seismic review team (SRT) is assembled to make initial seismic ruggedness screening decisions and do further screening during the walkdown. Two walkdowns are proposed. The first focuses on selection of the preferred shutdown path(s) and the second focuses on a detailed walkdown of all support systems for the preferred path or paths