
 DOESTD102395
5. DEFINITIONS
Annual Flood The maximum instantaneous peak discharge or level of flood in each year of record.
Atmospheric Pressure Change (APC) A wind hazard design parameter consisting of a reduction in
atmospheric pressure generated by a tornado.
Backwater Effect The rise in water surface elevation in an area caused by an obstruction which limits the
water flow from the area.
Basic Wind Speed The wind hazard design parameter used to determine wind pressure on buildings or
other facilities.
Deaggregate Determine the fractional contribution of each magnitudedistance pair to the total seismic
hazard. To accomplish this, a set of magnitude and distance bins are selected and the annual probability of
exceeding selected ground acceleration parameters from each magnitudedistance pair is computed and
divided by the total probability.
Design Basis Flood (DBFL) The peak flood level derived from the mean flood hazard curve in accordance
with the annual probability of hazard exceedance associated with the SSC. The DBFL is used to design or
evaluate SSCs of DOE facilities subjected to flood hazards.
Design/Evaluation Basis Earthquake (DBE) A specification of the mean seismic ground motion at a site;
used for the earthquakeresistant design of structures, systems, and components. The DBE is defined by
ground motion parameters determined from mean seismic hazard curves and a design response spectrum
shape.
Design Basis NPH Event The NPH event used as a basis for the design and/or evaluation of SSCs at
DOE facilities. The design/evaluation basis NPH event is called the design/evaluation basis earthquake
(DBE) for seismic hazards, design basis flood (DBFL) for flood hazards, or recommended basic wind
speed for wind hazards.
Design Response Spectrum A smoothed and broadened response spectrum (compared to a response
spectrum associated with any single actual earthquake) used for design purposes. See also the definition of
response spectrum in this Section.
Deterministic Method A technique which uses single values of parameters to perform an analysis.
Distributions of parameters caused by uncertainty or randomness are not explicitly considered. To account
for uncertainty, several evaluations may be conducted with different parameters.
Earthquake A sudden motion or vibration in the earth caused by the abrupt release of energy in the earth's
crust (lithosphere).
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