How to Survive a Nuclear Attack

"The direct effects will be survivable beyond a few miles except for the fallout plume, which could extend farther depending on wind, rain and the detonation yield," Dr. Michael May, an expert on nuclear arms at Stanford University says in an email interview.

There are three different damage zones that form during a nuclear blast, says Brooke Buddemeier, a health physicist at the Lawrence Livermore National Laboratory in California, in an email. Using a 10-kiloton nuclear blast, which is about the size of the bombs the United States dropped on Hiroshima and Nagasaki during World War II, as an example, the deadliest of these zones, the severe damage zone, will extend outward in a 0.5-mile (0.8-kilometer) radius from ground zero. In this zone, most buildings will be destroyed, and chances for survival are minimal.

The moderate damage zone extends from radius of 0.5 mile (0.8 kilometer) to 1 mile (1.6 kilometers). In this zone, buildings will experience major damage. For humans, early medical attention can significantly reduce the number of casualties.

The light damage zone extends in a 1- to 3-mile (1.6- to 4.8-kilometer) radius. A person's chances for surviving a blast in this zone are very high, especially if they are in a shelter (more on those in a minute). "Most injuries in the light damage zone are relatively minor, and most people in this area would be uninjured," Buddemeier says.

In 2007, the Preventative Defense Project at both Harvard and Stanford universities, held a workshop on what would happen during and after a nuclear blast. May, along with Ashton Carter and Dr. William J. Perry, both of whom served as U.S. secretaries of defense, summarized the workshop's findings in a report titled "The Day After: Action in the 24 Hours Following a Nuclear Blast in an American City." The portrait they paint is bleak. The group looked at what would happen if a 10-kiloton uranium bomb detonated in a major U.S. city without advance warning.

A ground burst would obliterate a city's downtown, while just outside that area, people wounded by fire, flying debris and intense radiation would more than likely die. A "plume of radioactive debris" would spread over a wide area, depending on wind and weather conditions.

"Those people who were relatively close to the detonation point, or who did not shelter themselves from the radiation (which would be most intense on the Day After and then subside with time) would receive large but varying doses of radiation," May and his co-authors write. "If the dose was intense (more than 400 rems), they would get sick and die; if strong but moderate (50 to 400 rems), they would get sick but probably recover; if moderate (below 50 rems), they would not notice the effect immediately but would have a greater chance of contracting cancer over their lifetime than if they had received no dose."

Most people within the blast area wouldn't survive, the report states. The majority of buildings would be destroyed or severely damaged. Things don't get much better away from the blast. About 5 miles (8 kilometers) out, people could be bombarded with fatal doses of radiation on the first day (depending on the prevailing winds) if they were not in a shelter.

"Within the first mile or so, little can be done," May says. "Beyond that, protective structures will help. How much depends on the structure. The chances of survival increase with distance. Chances depend on the yield and altitude of the detonation and other details such as whether the location is shielded by hills, etc."

Just how far you need to be from ground zero to survive a nuclear blast depends on many variables, such as the power generated by the blast, weather conditions and geological features, among other things. Yet, one thing is for certain: Buildings can, and do, shield people from radiation. "Beyond the immediate destruction and fire zone, sheltering in place is recommended both for fallout protection and to keep roads clear for responders," May says. "It's going to be very hard for parents, but if your kids are in school beyond the destruction and fire zone, don't go pick them up right away!"

"Any structure can help reduce your exposure to fallout radiation," adds Livermore's Buddemeier. "Though, if you have a few minutes to get into a more robust structure, that would provide more protection and further reduce your exposure."

Buddemeier also says that while a bit of ionizing radiation can penetrate buildings, the walls of most common urban buildings can reduce exposures by a factor of 10 or more. He says an adequate shelter could be a basement, particularly against a wall; multistory brick or concrete structures; office buildings (central core or underground sections); multistory shopping malls (away from the roof or periphery); and tunnels, subways and other underground areas.

The U.S. Federal Emergency Management Agency recommends, if possible, finding an underground shelter "such as a home or office building basement." In short, the more concrete, bricks, books and earth that you can put between yourself and radioactive fallout, the better your survivability rate. In addition, FEMA says if a nuke detonates:

Hawaii's Emergency Management Agency issued a bone-chilling set of guidelines in the event North Korea targets the state. Among other things, the agency called on residents to heed warning sirens. "If you're indoors stay indoors well away from the windows," the guidelines read. "If you are outdoors, seek immediate shelter in a building, preferably a concrete structure ... DO NOT look at the flash of light."

Still, despite the horrific nature of a nuclear detonation, Hawaii's Emergency Management Agency assumes that tens of thousands, based on the size of a North Korean nuclear weapon, will survive. "Survival is very likely," the agency's Toby Clairmont said in an email interview. "We estimate that over 90 percent of the people on Oahu would survive a 15-kiloton weapon detonated in the urban Honolulu area. Those who survive will need to shelter for up to 14 days to avoid exposure to radioactive fallout."

Or, if you're like Dan Judson, create your own prepper's cave. "Most people have nowhere to run, so sheltering in place is the only option," he says. "A house is relatively easy to fortify — plywood is surprisingly strong, and instructions can be found online. A basement, if you have one, is a good Alamo, though I really wouldn't want to live in ours for a long period of time. Also, a basement hideout can quickly become a trap. Remember, everyone at the Alamo died."