Pediatric Terrorism and Disaster Preparedness: A ... - PHE Home

Additional factors must be considered when deciding whether to advise evacuation or
sheltering in place in response to a radiological terrorist incident. Earlier
recommendations by the EPA for evacuation were written for a nuclear power plant
accident in which the release of radioactive material would occur hours after the initial
accident, allowing the population to be evacuated in a plume-free environment. However,
a terrorist attack is more likely to release a plume within minutes rather than hours of the
initiation of the event. Therefore, sheltering is likely to be more protective in response to
a radiological terrorist event. Sheltering should be performed whenever it is more
protective than evacuation.
Sheltering in place for protection from radioactive fallout is also an effective
countermeasure with little negative impact for short periods of time (hours) and may be
done in a fallout shelter, an underground area, or in the middle of a large building. Any
roofed structure would be of some benefit and would protect people from alpha and beta
radiation, because the structure would keep radioactive particles from falling on the skin
and further reduce the chance of inhalation. The degree of protection from gamma
radiation increases with the type of material used in constructing the shelter, from wood,
to masonry, to metal, metal being the most effective. Glass is not very effective in
preventing the penetration of gamma radiation, and windows should be avoided because
of the risk of lacerations from broken glass due to pressure changes or other
consequences of the accident. Sheltering generally reduce exposures to external and
internal contamination by 5 to 10 times. Sheltering is almost always justified if it will
prevent exposures of 0.050 Sv (5 rem). At exposures