Part 2.
HOW FALLOUT AND FATALITIES SHIFT WITH THE WINDS
A concerted nuclear attack on the missile silos in the U.S. heartland would generate radioactive dust that travels with prevailing winds. Sébastien Philippe and his colleagues at Princeton University’s Program on Science and Global Security used archived weather data to simulate the paths of the resulting plumes for 48 hours, by when most of the dust settles. Because wind directions change daily, the researchers computed fallout dispersal from an 800-kiloton warhead detonating simultaneously at each of 450 silos on any given day of 2021. The selections below (
A–I) demonstrate the variability of wind directions and, consequently, of the doses of outdoor radiation received over four days of exposure to radioactivity. The scientists further combined these simulations with data on population density and building height to calculate the resulting fatalities. Someone absorbing four grays (equivalent to four joules of radiation energy per kilogram of body weight) would have a 50 percent chance of dying, but people sheltering in bigger buildings would receive smaller doses. Depending on wind directions, a nuclear attack on the missile silos could kill several million people.
Credit: Sébastien Philippe, Svitlana Lavrenchuk and Ivan Stepanov
Fatality Count: For a simulated attack on any day of 2021, the scientists computed the resulting fatalities. The chart shows the impact of variable wind directions on the estimated fatalities after four days of exposure. The estimates range from 340,000 (for an attack on July 1) to 4.6 million (on December 2). The average estimated death toll is 1.4 million. The curve shows the probability (technically, probability density) of the number of fatalities specified on the vertical axis.
Credit: Sébastien Philippe, Svitlana Lavrenchuk and Ivan Stepanov
WHICH LOCATIONS ARE THE RISKIEST?
To calculate the average risk of radiation exposure at any given location in North America from a nuclear attack on the silo fields, Philippe and his co-workers summed the simulated outcomes for any day of 2021 (preceding graphic) and divided by 365. They thereby averaged the impact of shifting winds on radioactive fallout across the continent. This map shows the average outdoor radiation dose across North America after four days of exposure. Communities living closest to the silos could receive several times more than 8 Gy, which scientists regard as lethal. Most inhabitants of Montana, North Dakota, South Dakota, Nebraska and Minnesota would get average doses greater than 1 Gy, causing fatalities from acute radiation syndrome, especially among children. The U.S. population would receive average doses greater than 0.001 Gy per year, which is the current annual limit for exposure to the public.
Credit: Sébastien Philippe, Svitlana Lavrenchuk and Ivan Stepanov
THE WORST-CASE SCENARIOS
Sifting through simulations for each day of 2021, the Princeton researchers computed the worst possible outcome at each location from a concerted nuclear attack on the missile silos. This map shows all the worst-case scenarios across North America. Not all locations would experience the worst outcome from the same attack; which areas would be impacted depends on wind patterns on the day of the attack. Overall, most people in North America live in areas with about a 1 percent chance of receiving an outdoor dose greater than 1 Gy. The chance of getting a lethal dose escalates closer to the silos, with three million at risk of receiving 8 Gy or more. These simulations make no assumptions about access to health care or emergency services. Nor do they include other sources of exposure such as immediate radiation from nuclear explosions.
Credit: Sébastien Philippe, Svitlana Lavrenchuk and Ivan Stepanov
is a scientist at Princeton University's Program on Science and Global Security. He develops methods for monitoring nuclear weapons and models the impact of nuclear explosions.
