Nuclear power plants represent a vital segment of the U.S. infrastructure that must be safeguarded from terrorists in the aftermath of the September 11th attacks. An area of particular concern involves vehicle bombs detonated near facility buildings or explosive charges carried into the plant by saboteurs. In order to determine the vulnerability of a nuclear power plant to scenarios involving terrorist explosives, it is necessary to define blast fragility functions for plant components and structures. A fragility function is a plot of component kill probability versus blast overpressure as seen in Fig. 1. Developing the best possible fragility functions will require a careful assessment of existing component vulnerability data as well as some reduced/full-scale testing to expand the database.