"The physical security of nuclear power plants and their vulnerability to deliberate acts of terrorism was elevated to a national security issue following the attacks of September 11, 2001. Congress subsequently enacted new nuclear plant security requirements and has repeatedly focused attention on regulation and enforcement by the Nuclear Regulatory Commission (NRC). More than a decade after the 9/11 attacks, security at nuclear plants remains an important concern. The Energy Policy Act of 2005 (EPACT05, P.L. [Public Law] 109-58) imposed specific criteria for NRC to consider in revising the 'Design Basis Threat' (DBT), which specifies the maximum severity of potential attacks that a nuclear plant's security force must be capable of repelling. In response to the legislative mandate, NRC revised the DBT (10 C.F.R. Part 73.1) on April 18, 2007. Among other changes, the revisions expanded the assumed capabilities of adversaries to operate as one or more teams and attack from multiple entry points."
CRS Report for Congress, RL34331