Find out how emergencies are classified

The Nuclear Regulatory Commission (NRC) splits nuclear power plant emergencies into four levels. The levels are listed in order of least impactful to most impactful:

  • Level 1: Unusual Event. This alert notifies you if an unplanned event or security threat happens at the power plant. The event does not require emergency action by people or officials outside of the plant.
  • Level 2: Alert. This alert takes place if a safety system incurs damage. A security event may also be a reason for the alert. This event involves risk to site personnel or damage to site equipment.
  • Level 3: Site Area Emergency. This alert occurs if a release of radiation has happened or may happen soon. A Level 3 release occurs within a 100-yard area around the plant. This distance is the federal area allowed for this level of event. The alert can also occur if site employees are assaulted. Another cause is damage done to the equipment needed for public safety.
  • Level 4: General Emergency. This alert is given when a release of radiation has occurred or may occur outside of the site area. The alert can also happen if the plant staff lose physical control of the facility. Protective actions may need to occur in the Protection Action Zones (PAZs).


PG&E notifies local, state, and federal officials during each alert level. The officials take the steps that are included their emergency plans.


Learn more about the NRC. Visit US.NRC.