Planning for the worst in Washington State: initial response planning for improvised nuclear device explosions.

Since 11 September 2001, improvised nuclear devices have become recognized as an important radiological threat requiring emergency response planning. Although Protective Action Guidance is well established for fixed nuclear facilities, correspondingly well-developed guidance does not exist for nuclear explosions. The Washington State Department of Health has developed preplanned Protective Action Recommendations for improvised nuclear device explosions. These recommendations recognize the need for advice to the public soon after such an event, before significant data are available. They can be used before significant outside support is available locally, and reference observable effects so people can use them if communications were disabled. The recommendations focus on early actions (24-48 h) and place priority on actions to avoid deterministic health effects due to residual fallout. Specific emphasis is placed on determining recommendations for evacuation, as well as the extent of the area for sheltering. The key recommendations developed for an initial public response are: (1) if there is ready access to robust shelter such as an underground basement or interior spaces in a multi-story structure, immediate sheltering in these areas is the best action, regardless of location; (2) if robust shelter is not available, and if fallout is observed in the area, then evacuation is the best general recommendation for locations within 16 km (10 miles) of the explosion; and (3) beyond 16 km (10 miles), the generally recommended protective action is to shelter in the best-protected location which is readily available.