Depending upon the circumstances in an unlikely event of a nuclear power plant radiological emergency, the public may be advised to take protective actions, which may include evacuation and sheltering in place: Photo of a School

Evacuation from an area removes the public from further exposure to radioactive material. To learn more, see Principles of Evacuation.
Sheltering means keeping the population indoors, such as at home, the office, school, or a shopping mall to reduce exposure to radioactive material.

Under most conditions, evacuation is preferred. However, under some conditions, sheltering in place provides protection that is equal to or greater than evacuation, considering weather, competing events, fast-breaking or short-term release, or traffic conditions. Depending on the type of building used, sheltering in place can result in a reduction of radiation dose of up to 80% compared to a dose received outdoors and unsheltered. NUREG-0654/FEMA-REP-1 , Rev. 1, Supplement 3, "Criteria for Preparation and Evaluation of Radiological Emergency Response Plans and Preparedness in Support of Nuclear Power Plants - Criteria for Protective Action Recommendations for Severe Accidents," provides additional information on decisions for protective actions. In June 2005, the NRC issued RIS 2005-08 that endorses guidance written by the Nuclear Energy Institute which details an acceptable range of early-phase protective actions that licensees may use in the event of a nuclear power plant incident.

Potassium Iodide as Supplement. In January 2001, the Commission published a rule change to the NRC emergency planning regulations to include the consideration of the use of potassium iodide. As necessary, KI is to be used to supplement evacuation or sheltering in place, not to take the place of these actions. If taken properly, potassium iodine (KI) will help reduce the dose of radiation to the thyroid gland from radioactive iodide, and reduce the risk of thyroid cancer. For more information, see Use of Potassium Iodide.

Evacuation Studies. The NRC published a study in January 2005 that examined the efficiency and effectiveness of public evacuations of 1,000 or more people in response to natural disasters, technological hazards, and malevolent acts, occurring in the U.S. between January 1, 1990 and January 30, 2003. This study, NUREG/CR-6864, "Identification and Analysis of Factors Affecting Emergency Evacuations," (Volume 1 & Volume 2) identified a universe of 230 evacuation incidents, and a subset of 50 incidents were selected for case study analysis. This study revealed that large-scale evacuations in the U.S., whether pre-planned or ad-hoc, are very effective, successfully save lives, and reduce the potential number of injuries associated with the hazards.

Picture of Evacuation Sign Evacuation Time Estimates. To help plan evacuations, evacuation time estimates are developed for each nuclear power plant site. These estimates are one tool used to assist government authorities to determine the best exit routes and traffic control points. For example, as demonstrated in Figure 1, authorities may decide to recommend evacuation for a small part of the emergency planning zone (the red shaded area in the figure) and recommend sheltering in place for other areas in the zone. Authorities would instruct those sheltering in place to receive additional information and instructions, if needed. The time estimates are used to identify potential traffic congestion and to develop plans for traffic management and use of traffic control personnel during an evacuation.

The NRC updated guidance on how to develop evacuation time estimates in January 2005. NUREG/CR-6863, "Development of Evacuation Time Estimate Studies for Nuclear Power Plants," integrates new technologies in traffic management, computer modeling, and communications systems to identify additional tools useful in the development of new, or updating the existing, evacuation time estimates.

emergency planning zone image showing wind direction and a red shaded area in the figure representing a small part of the emergency planning zone which could be recommended for evacuation

Figure 1