Urban Nuclear Attack Scenarios Examined

Scientists now have a clearer answer to one of the atomic age's more terrifying questions: How would a nuclear detonation affect a major metropolitan environment?

Physicists have studied the atmospheric effects of nuclear war for decades. In particular, they have looked at how wind could spread deadly, radiated particles, or nuclear fallout. They have also examined how smoke from burning forests and cities might blot out the sun's rays in a possible nuclear winter.

Understanding how nuclear fallout and nuclear winter might play out depends strongly on the field of environmental fluid mechanics, the study of how air and water move. Urban landscapes introduce new complications to an already intricate system.

"It's a very complex physical process," physicist Fernando F. Grinstein told Discovery News. "Blast effects and fallout radiation interact with urban geometries and even specific building materials. We can develop, validate and verify models of individual process with relatively low-level computing and algorithmic resources. However, there are many challenges."

Several of those challenges for predicting blast effects and fallout revolve around the simulated models researchers use to gauge contaminant distribution.

In a March 2009 study published in the Journal of Flow, Turbulence and Combustion, Grinstein, Randy Bos and Thomas Dey of Los Alamos National Laboratory pointed out that previous radiation plume models were based on simplified data designed to gauge the flow of radiated materials over flat terrain. These models tended to predict a cone-shaped fallout zone.

Large metropolitan areas, however, tamper with local wind patterns.

For example, sun-heated parking lots create localized updrafts, drawing in air from surrounding areas. Skyscrapers work like artificial mountains. If a plume of radiated debris were to blow against a tall building, physicists predict that the flow would launch skyward in what they call the fountain effect, resulting in a wider distribution of radiated particles.

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Researcher Adam Wachtor of University of California, Irvine, a project collaborator of Grinstein's, presented his work to improve fallout simulation models on Nov. 22, 2009, at the 62nd Annual American Physical Society's (APS) Division of Fluid Dynamics Meeting. Wachtor incorporated factors such as radiation shielding by tall buildings and the fountain effect.

The study is part of a larger effort among multiple U.S. government agencies and private contractors to help city and emergency planners deal with events that result in the airborne transfer of contaminants -- an area of study University of Missouri physics professor Rob V. Duncan has studied extensively.

Duncan, who worked with the European Organization for Nuclear Research (CERN) and the World Federation of Scientists on terrorism mitigation plans, says the best course of action lies in providing people inside the disaster zone with a survival strategy based on real-time data.

"When a terrible event occurs, most people who are caught up in it will naturally rely on their cell phones and PDAs for helpful information," Duncan said. "(Emergency responders could) use this modality both to communicate with them and to plan the best response based on the position information that is available from their phones."

Duncan says that responders then could use the composite cell phone data to determine survivor locations. The information could be compared with damage and contamination data to determine evacuation routes and medical response.

"Nature favors the prepared mind." Duncan said. "These simulations permit disaster response professionals to carefully think through strategies and consequences well before the actual event occurs."

Robert Lamb is a writer for HowStuffWorks.com.