"R" In the numeric designation signifies that the 2004 standard was reaffirmed (recertified) as an American National Standard in 2010. No changes can be made to a standard during reaffirmation.
This standard provides: (i) criteria for selecting the Seismic Design Category (SDC) for nuclear facility structures, systems, and components (SSCs) to achieve earthquake safety and (ii) criteria and guidelines for selecting Limit States for these SSCs to govern their seismic design. The Limit States are selected to ensure the desired safety performance in an earthquake. The Seismic Design Categories (SDCs) used in this standard are not the same as the SDCs referred to in the International Building Code (IBC).