The purpose of this report is to set forth seismic criteria and design concepts applicable to review analyses and upgrading for selected nuclear power plants, although the principles are applicable generally to older operating plants. At the outset, it is expected that the review process would consist of two general tasks, one pertaining to detailed review of the existing plant in the light of applicable review criteria and the second involving detailed design and analysis studies to develop the desired (and possible) upgrading of the seismic resistance. It is envisioned that the detailed review would encompass inspection of the plant, review of existing documentation (reports, plans, and calculations) as appropriate with identification of those systems which realistically and economically are amenable to upgrading. As a part of this review it may be desirable to carry out a risk analysis to help provide a basis for the decisions that must be made as to the desirability and advantages of carrying out the upgrading.