The Nuclear Regulatory Commission (NRC) is amending its security regulations and adding new security requirements pertaining to nuclear power reactors. This rulemaking establishes and updates generically applicable security requirements similar to those previously imposed by Commission orders issued after the terrorist attacks of September 11, 2001. Additionally, this rulemaking adds several new requirements not derived directly from the security order requirements but developed as a result of insights gained from implementation of the security orders, review of site security plans, implementation of the enhanced baseline inspection program, and NRC evaluation of force-on-force exercises. This rulemaking also updates the NRC's security regulatory framework for the licensing of new nuclear power plants. Finally, it resolves three petitions for rulemaking (PRM) that were considered during the development of the final rule.