text: Scientist releases guide to surviving a nuclear bomb in your city 
   
   By Agence France-Presse 
   
   Tuesday, January 14, 2014 20:51 EDT 
   
   A scientist published a guide Wednesday to help authorities limit deaths from fallout after a city is hit by a nuclear bomb. 
   
   Taking cover in existing buildings is widely accepted as a critical first action after a nuclear blast in a major city. 
   
   But how long people should stay there before moving to better shelter is a more complex question. 
   
   Buildings that are lightweight or lack a basement are more easily penetrated by radioactive dust. 
   
   Writing in a British scientific journal, Michael Dillon of the Lawrence Livermore National Laboratory in California, has now come up with a mathematical model for the “optimal shelter exit time” to minimise radiation risk. 
   
   Based on his calculations, if adequate shelter is 15 minutes away, individuals should remain in their initial, poor-quality shelter no longer than 30 minutes after detonation. 
   
   If, however, the better shelter is only five minutes away, individuals should move there immediately and forego the closer but unsafe buildings altogether, he wrote. 
   
   Reaching adequate shelter rapidly could save between 10,000 and 100,000 individuals from fatal exposure in the event of a single, low-yield detonation, said the study published in Proceedings of the Royal Society A. 
   
   “These methods are intended to assist emergency planning officials in the development of an optimal low-yield nuclear detonation response strategy,” wrote Dillon. 
   
   A low-yield blast is described as 0.1-10 kilotons. 
   
   One kiloton (kT) is an explosive force equivalent to that of 1,000 metric tons of TNT. The US bomb that killed more than 200,000 people in Hiroshima, Japan, in 1945 was about 15 kT. 
   
   More than a fifth of American households lack basements or are considered too lightweight to offer shelter in the fallout phase of the emergency, the study said. 
   
   [Image via Agence France-Presse] ||||| People living within about 20 miles (32 kilometers) of a small-scale nuclear attack have up to half an hour to seek out adequate shelter safely, as long as travel time to that shelter is no more than 15 minutes away, according to a recent report on the optimal escape strategies for small-scale nuclear explosions. 
   
   The threats of catastrophic Cold War-style nuclear bombs have subsided since international agreements like the 1970 Treaty on the Nonproliferation of Nuclear Weapons have taken hold to protect society from the annihilative attacks that flattened Hiroshima and Nagaski, in Japan, during World War II. 
   
   Still, the threat of smaller-scale nuclear attacks with explosive energy orders of magnitude less intense has increased in recent years as the technology to build such weapons has become more prevalent. These smaller-scale detonations may not be strong enough to flatten cities, but they do produce harmful radioactive fallout that residents must avoid to reduce the nauseating effects of radiation poisoning and longer-term risks of cancer. [The Top 10 Largest Explosions Ever] 
   
   The best way to protect against the radioactive dust and ash of nuclear fallout is to seek shelter underground, but more than 20 percent of U.S. households do not have basements, according to a 2009 survey from the U.S. Energy Information Administration. Those people without basements must therefore decide when and how far to travel in search of higher-quality shelter in the event of an attack. 
   
   To help simplify this decision process, Michael Dillon of the Lawrence Livermore National Laboratory in Livermore, Calif., conducted mathematical analyses based on existing data on the threats induced by small-scale nuclear explosions to streamline rules people can abide by to protect themselves from fallout. 
   
   "The principle is trying to figure out the least amount of information you need to make your decisions as fast as possible," Dillon told LiveScience. "In these sorts of situations, you don't have a lot of time, and you need to quickly know what you are looking for to make these decisions." 
   
   The first order of business is to determine the quality of shelter that one has immediate access to at the time of an attack. Underground concrete shelters are best, as they put the largest amount of mass between a person and fallout, but the core of large buildings — such as large offices or schools — can also provide adequate shelter, Dillon said. Thin-walled homes, on the other hand, made of wood or other flimsy materials are considered poor-quality shelters. 
   
   Through his analyses, Dillon determined that people within poor-quality shelters can reduce radiation poisoning by staying within those shelters for only up to 30 minutes after the detonation before seeking out adequate shelter, as long as that shelter is reachable within 15 minutes. However, if adequate shelter is reachable within five minutes, then residents should pick up and go to that shelter immediately after a detonation. 
   
   People do not need to do much to protect themselves against radiation while in transit, since the fallout can largely be rinsed off once a person seeks refuge. The only thing a person really needs, Dillon half-joked, is a good pair of sneakers that allows them to travel quickly, if they are traveling by foot. 
   
   If traveling by car, people must take traffic into consideration when planning their escape strategies, Dillon said, pointing out that his results provide only one piece of a larger response strategy that can become more complicated by unpredictable factors such as traffic flow. 
   
   Dillon is working to assess the distribution of adequate shelters across the United States, and says that his preliminary results suggest that, as a whole, the country is well equipped with adequate shelters within 15 minutes of many households. These analyses are still in the works, however, and are not yet conclusive, he said. 
   
   The complete report is detailed today (Jan. 14) in the journal Proceedings of the Royal Society A. 
   
   Follow Laura Poppick on Twitter. Follow us @livescience, Facebook & Google+. Original article on LiveScience.
target: – Good news: A mathematical model has been created that could help save your life in the event that your city is hit by a nuclear bomb. Scientist Michael Dillon's model, published Tuesday, is about reducing radiation risk from the bomb's fallout, and calculates "optimal shelter exit time." The longstanding advice has been to immediately seek shelter, ideally underground, if a bomb hits. But there is better and worse shelter—the latter being "lightweight" buildings (such as ones made of wood) or ones without basements; the AFP reports more than 20% of US homes fall into the worse category. Here is Dillon's determination for people living within 20 miles of a low-yield nuclear blast, meaning one a bit smaller than Hiroshima: If it would take five minutes or less to reach better shelter (that concrete basement, or the center of a large building, like a big office, reports LiveScience), bypass the more immediate shelter and go there straight away. If better shelter is 15 minutes away, stay in the worse shelter for up to 30 minutes, then head out. As for the transit period, don't waste time worrying about protecting your body from the radiation, he says, which can mostly be rinsed off once you get to your shelter. The findings are actually intended for emergency planning officials, who can make use of the findings when designing "an optimal low-yield nuclear detonation response strategy," writes Dillon, who works at California's Lawrence Livermore National Laboratory.