Facility One or more building(s) or structure(s), including systems and components, dedicated to common
function (includes operating and non-operating facilities and facilities slated for decontamination and
Graded Approach An approach where the design, evaluation, and construction process for SSCs require
emphasis commensurate with their mission, cost and potential consequences of failure. Accordingly,
performance categories with specified performance goals ranging from low to extremely low probability of
NPH failure are specified in DOE-STD-1020-2002.
Hurricane intensity Hurricane-type storms are events associated with maximum sustained 1- minute wind
speeds in excess of 75 mph. The U.S. National Weather Service uses the Saffir/Simpson scale to rate the
intensity and the damage potential of hurricanes. This scale is divided into 5 numbers, 1 through 5. Larger scale
numbers represent high wind speeds at which considerable damage occurs.
Liquefaction The sudden loss of shear strength and rigidity of saturated, cohesionless soils, due to steady state
ground water flow or vibratory ground motion. The term seismic liquefaction (or cyclic mobility) is used in
this Standard for liquefaction phenomena associated with seismic motions.
Magnitude A measure of the size of an earthquake. It is related to the energy released in the form of seismic
waves. Magnitude means the numerical value on a standardized scale such as, but not limited to, Moment
Magnitude, Surface Wave Magnitude, Body Wave Magnitude, or Richter Magnitude scale.
Model Building Codes Building codes containing design and construction requirements that apply to normal
commercial buildings (e.g., IBC 2000, International Building Code).
Natural Phenomena Hazard (NPH) An act of nature (for example, earthquake, wind, hurricane, tornado,
flood, precipitation, volcanic eruption, lightning strike, or extreme cold or heat) which poses a threat or danger
to workers, the public, or to the environment by potential damage to structures, systems, and components.
One- (Five-) Hundred-Year Flood A flood level which will be equaled or exceeded with a 1.0 (0.2) percent
chance in any given year.
Performance Category (PC) A classification using a graded approach in which structures, systems, or
components in a category are designed to assure similar levels of protection (i.e., meet the same performance
goal) during natural phenomena hazard events. Five performance categories ranging from 0 to 4 in order of
increasing level of protection have been defined in DOE-STD-1021-93, (e.g., PC-1 for building structures with
potential human occupancy; PC-4 for high hazard facilities such as nuclear power plants).
Performance Goal The mean annual probability of exceedance of acceptable behavior limits used as a target
to develop natural phenomena hazard mitigation requirements. Numerical values for performance goals for
each performance category are provided in DOE-STD-1020.
Probable Maximum Flood The flood that may be expected from the most severe combination of critical
meteorological and hydrologic conditions that are reasonably possible in the drainage basin under study.