Arrangements for emergency plans are carried out in several emergency planning zones that are roughly circular around the facility. The on-site emergency zone is the area surrounding the facility within the security perimeter. It is the area under the immediate control of the facility or opera­tor. The off-site emergency zone is the area beyond that under the control of the facility operator in which intervention could be needed for emergen­cies resulting in major off-site releases or exposures. The level of planning will vary depending on the distance from the facility.

The off-site emergency zone is usually divided in two subzones. The precautionary action zone is a pre-designated area around the facility where urgent protective action has been pre-planned and will be imple­mented immediately upon declaration of a general emergency, to substan­tially reduce the risk of severe deterministic health effects by taking protective action within this zone before or shortly after a release. The urgent protective action planning zone is a pre-designated area around the 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.

Figure 12.1 shows a conceptual distribution of the emergency planning zones around a nuclear power plant.

12.1 Emergency planning zones.