The emergency plans for facilities with the highest radiological risk (such as nuclear power reactors) define two emergency planning areas:
ON-SITE AREA
This is the area surrounding the facility within the security perimeter, fence or other designated property marker. It can also be the controlled area around a radiation source or contaminated area. It is the area under the immediate control of the facility or operator. For transport emergencies or emergencies involving uncontrolled sources or localised contamination, there may not be an on-site area defined at the onset of the emergency.
OFF-SITE AREA
This is the area beyond the on-site area. For facilities with the potential for emergencies resulting in major off-site releases or exposure, the level of planning will vary depending on the distance from the facility. For these facilities, three emergency planning zones can be defined:
Precautionary action zone (PAZ): 3- 5 km from the radiation source
This is a predefined area around a facility, where urgent protective action has been planned and will be implemented immediately upon declaration of a general emergency. The goal is to substantially reduce the risk of severe deterministic health effects by taking protective action within this zone before or shortly after a release.
Urgent protective action planning zone (UPZ): 25 km from the radiation source
This is a predefined area around a facility where preparations are made to promptly implement urgent protective action based on environmental monitoring data and assessment of facility conditions, the goal being to avert doses specified in international standards.
Food restriction planning radius (FRR): 300 km from the radiation source
This is the area where preparations are made for effective implementation of protective actions to reduce the risk of stochastic health effects from the ingestion of contaminated locally grown food. In general, protective actions such as relocation, food restrictions and agricultural countermeasures will be based on environmental monitoring and food sampling.
These zones should be roughly circular areas around the facility, with their boundaries defined by local landmarks (eg roads or rivers) to allow easy identification during response. It is important to note that these zones do not stop at national borders.
The size of the zones can be determined by an analysis of the potential consequences: the generic zone sizes as stated above are based on previous studies (Method for Developing Arrangements for Response to a Nuclear or Radiological Emergency, EPR-METHOD (2003), IAEA, VIENNA, 2003, ISBN 92–0–111503–2).