United States Nuclear Regulatory Commission - Protecting People and the Environment

Principles of Evacuation

Figure - Keyhole
Figure 1

Evacuation models implemented for severe accidents generally use the following principles:

  • All people within a specified radius of the incident (usually 2 miles) are evacuated, and;
  • People living downwind from the projected path of plume travel and bordering sectors are also evacuated. This area, the downwind sector and two adjacent sectors, affords protection from potential wind shifts and plume meander. This is known as a "keyhole" because of its appearance. The figure illustrates a keyhole.
Page Last Reviewed/Updated Monday, September 29, 2014