In the center of a parched lakebed located northwest of Las Vegas, a solitary segment of a bridge stands, its steel girders contorted like strands of pasta. Surrounding this peculiar sight are other anomalies — a colossal bank vault devoid of any banking institution for miles; the entrance to an underground parking facility lacking any subterranean levels; and structures of rebar and concrete that have been violently torn apart, exposing their interiors to the vast desert sky.
Approximately half a mile away, on the morning of May 8, 1953, an Air Force bomber released a Mk-6D nuclear bomb from an altitude of 19,000 feet above the arid ground. The explosion yielded 27 kilotons of TNT, generating a shockwave that distorted the bridge and forced the vault open. This test, designated “Encore,” aimed to assess what, if anything, in the civilian environment could withstand a nuclear detonation (the conclusion appears to be that very little can).
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“The risk is significant,” says Hans Kristensen, director of the Nuclear Information Project at the Federation of American Scientists. The talk of testing comes at a time when nuclear weapons are resurgent: Russia is designing nuclear weapons to attack satellites and obliterate seaports; China is dramatically expanding its nuclear arsenal; and the U.S. is undergoing a major modernization of its nuclear warheads. After years of declining nuclear stockpiles, the world looks poised to begin increasing the number and types of nuclear weapons being deployed.
Going underground
Amid these growing tensions, the U.S. National Nuclear Security Administration, the civilian agency that maintains America’s nuclear stockpile, allowed a small group of journalists to tour a secretive nuclear weapons laboratory beneath the Nevada desert this winter. The effort was part of outgoing NNSA administrator Jill Hruby’s effort to display more transparency about what the U.S. is doing with its nuclear stockpile and why.
“This was designed to be a nuclear test location originally,” Funk explains. In the early 1960s, nuclear tests went underground to protect people and the environment from dangerous radioactive fallout. In fact, somewhere in the maze of tunnels we’re walking through is a sealed shaft from a full-scale nuclear detonation — the Ledoux test in 1990.
The Ledoux test was among the last nuclear weapons the U.S. ever detonated. At the end of the Cold War, politicians wanted to show the nuclear arms race had also ended. In 1990, the Soviet Union conducted its last nuclear test. Two years later, the U.S. announced it would no longer test nuclear weapons. One by one, the world’s nuclear weapons states followed, with the exception of North Korea, whose last test was in 2017.
The decision to halt testing “was very much an attempt to look around and see what we can do to make it clear that we’re not just talking about the end of the Cold War, we’re serious about it,” Kristensen says.
But these tunnels stayed open. The U.S. still needed to ensure that its nuclear weapons were safe and reliable, so nuclear weapons scientists and engineers embarked on a new program to test the nukes without actually setting them off. Kristensen and most experts agree that the program, known as stockpile stewardship, has been effective in staving off new nuclear testing.
The stockpile stewardship program broadly consists of two arms — supercomputers at the nation’s major nuclear weapons labs are used to conduct large-scale digital simulations of nuclear weapons from “button to boom.” Highly classified nuclear experiments, like those that take place at PULSE, supply real-world data that ensures that the simulations are accurate.