Protection against Malevolent Use of Vehicles at Nuclear Power Plants: Vehicle Barrier System Siting Guidance for Blast Protection: Volume 1, Revision 1 [open pdf - 550KB]
"This manual provides for determining the minimum safe standoff distance between vital safety related equipment and the design basis vehicle bomb threat adopted by the U.S. Nuclear Regulatory Commission. Vital safety related equipment should survive the design basis vehicle bomb attack when the minimum safe standoff distance is provided. Guidance is provided for exposed vital safety related equipment and for equipment housed within vital area barriers."
Defense Technical Information Center (DTIC): http://www.dtic.mil/dtic/