The Nuclear Regulatory Commission has established four classifications to describe a nuclear emergency. The Emergency Classification Levels are listed below:
NOTIFICATION OF UNUSUAL EVENT
Events are in progress or have occurred which indicate a potential degradation of the level of safety of the plant or indicate a security threat to facility protection has been initiated. No releases of radioactive material requiring offsite response or monitoring are expected unless further degradation of safety systems occurs.
Events are in progress or have occurred which involve an actual or potential substantial degradation of the level of safety of the plant or a security event that involves probable life threatening risk to site personnel or damage to site equipment because of Hostile Action. Any releases are expected to be limited to small fractions of the Environmental Protection Agency Protective Action Guide.
SITE AREA EMERGENCY
Events are in progress or have occurred which involve actual or likely major failures of plant functions needed for protection of the public or hostile action that results in intentional damage or malicious acts; 1) toward site personnel or equipment that could lead to the likely failure of or; 2) that prevent effective access to, equipment needed for the protection of the public. Any releases are not expected to result in exposure levels which exceed Environmental Protection Agency Protective Action Guide exposure levels beyond the site boundary.
Events are in progress or have occurred which involve actual or imminent substantial core degradation or melting with potential for loss of containment integrity or hostile action that results in an actual loss of physical control of the facility. Releases can be reasonably expected to exceed Environmental Protection Agency Protective Action Guide exposure levels offsite for more than the immediate site area.