Dimitris Drikakis, a fluid dynamics researcher at the University of Nicosia in Cyprus, led the study both to illuminate the ongoing risks of nuclear escalation and to examine how one might have a chance at survival if the unthinkable should come to pass. “People have forgotten the devastating impacts nuclear war can have. But now we’re seeing the discussion starting again, and there’s a debate about the potential for nuclear war in Ukraine,” says Drikakis. “I think this kind of study raises awareness within the wider population that nuclear explosions are not a joke.” His grim research comes just as the Bulletin of the Atomic Scientists announced that it has ticked the Doomsday Clock forward, to 90 seconds until an apocalyptic midnight, citing the increasing nuclear tensions following Russia’s invasion of Ukraine. Scientists and artists developed the metaphorical clock to communicate risks posed by global, human-caused problems including climate change, but the dangers of nuclear war have been a major focus since its inception. Drikakis combed through scientific research on what the aftermath of nuclear weapon use would look like, and he spotted a gap: There’s little knowledge of the effects on humans indoors in the “moderate damage zone” a few miles from the epicenter, far enough away that buildings might not get blown to bits. He and his colleague Ioannis Kokkinakis focused on this area and published their work in the Physics of Fluids journal last week. Since no one’s going around testing nukes on buildings these days, this kind of research employs computer simulations. Drikakis and Kokkinakis simulated the blast effects of a 750-kiloton warhead—like the hundreds of larger bombs in Russia’s arsenal—delivered by an intercontinental ballistic missile, which would detonate about 3 kilometers above a metropolis. They studied how the supersonic shock waves would propagate through a three-room concrete structure situated in the moderate damage zone and assumed that the concrete was strong enough to withstand the 3 to 5 pounds per square inch of pressure from the blast wave. Being in an enclosed space matters because, the researchers find, the blast winds following the initial fireball can be even more dangerous and deadly than the blast itself. These winds push outward behind the shock wave, and anyone facing the brunt of them could be slammed against a wall at high speed. The winds are especially dangerous if a person is near a door or window or in a corridor or an opening to a room. Winds quickly funnel through such areas, throwing people and furniture around—it’s like a storm let loose in a building. (If you are wondering whether you could copy the Indiana Jones move in The Kingdom of the Crystal Skull, surviving a nuclear blast by jumping inside a fridge, Drikakis says that might be possible. But it’s also possible the strong wind would hurl the fridge with Indy inside.) Ferenc Dalnoki-Veress, a scientist-in-residence and nuclear physicist at the Middlebury Institute of International Studies at Monterey, points out that if multiple buildings happen to lie between the structure you’re in and the incoming blast wave, that shadowing effect can lessen the airspeed and forces involved. Those in a basement might avoid the worst blast effects too. “A lot of people have a nihilistic point of view that there’s nothing we can do about it,” but that’s not the case, he says. This shouldn’t be construed as a way to be safe in a nuclear explosion, says Dylan Spaulding, an earth scientist and nuclear expert at the Union of Concerned Scientists. Strong structures made of concrete with metal reinforcement and designed for seismic safety would survive the pressures the team modeled, he says, but those pressures would be enough to destroy most traditional, wood-framed houses and brick structures without reinforcement. And he points out that the blast wave is only part of the story. While it is the main source of danger in a non-nuclear explosion—like the one that rocked Beirut in 2020, which was caused by a large quantity of flammable ammonium nitrate stored at the city’s port—nuclear weapons also throw out ionizing radiation and heat, followed by radioactive fallout. Radiation exposure through the skin or inhalation can have many health effects, including skin burns, organ damage, and cancer. The range of radiation exposure could extend tens of miles from the epicenter, so people who survive the blast could later be felled by the radiation. Drikakis’ example focused on what’s called a “strategic” nuke deployed on an ICBM, but there are also “tactical” nukes, which are dropped by a plane onto a battlefield and which can blow up on the ground. Such explosions play out differently but can be as deadly and destructive, potentially exposing more people to lethal radiation doses, Spaulding says. Humanity’s most destructive weapons have been used in war only once, when the US demolished Hiroshima and Nagasaki, Japan, with two atomic bombs at the end of the Second World War in 1945. Together they killed more than 100,000 Japanese civilians and injured many more. And Spaulding points out that along with experiments conducted at the Nevada Test Site, they offer some of the only real-world evidence about the kinds of structures that can survive an atomic blast, and how well. But last year Russian president Vladimir Putin insinuated that nukes are not off the table in his attack on Ukraine. While NATO leaders have not used such threatening rhetoric, the international organization conducted nuclear exercises in October, simulating dropping B61 nuclear bombs. US president Joe Biden’s Nuclear Posture Review the same month abandoned a “no first use” policy he previously supported. One could imagine nuclear risks in other conflicts too, like the possibility of North Korea using a nuke against South Korea, or Pakistan and India using them against each other. The world’s arsenals add up to about 12,700 warheads, according to an inventory by the Federation of American Scientists. That’s fewer than their peak of around 70,000 near the end of the Cold War, thanks to arms reduction treaties. But some of those pacts have since been dissolved, and the dangers never went away, as the Doomsday Clock’s metaphor illustrates. This is not a game, Drikakis says. The risks of a devastating nuclear strike are all too real, he says: “We have to maintain peace by understanding the risks of not maintaining the peace.”
