© 2025 WLRH All Rights Reserved
Play Live Radio
Next Up:
0:00
0:00
0:00 0:00
Available On Air Stations

How the U.S. determines whether its nuclear weapons still work properly

STEVE INSKEEP, HOST:

The United States maintains an arsenal of thousands of nuclear weapons, but it hasn't tested one in decades. Instead, the U.S. is using simulations and experiments to see if the nukes still work. NPR's Geoff Brumfiel got a peek into the testing program in the desert outside Las Vegas.

(SOUNDBITE OF CAR DRIVING BY)

GEOFF BRUMFIEL, BYLINE: I'm standing out here on the Nevada national security site, used to be the test site. And in the 1950s, this is where they actually tested nuclear weapons out in the open.

(SOUNDBITE OF ARCHIVED RECORDING)

UNIDENTIFIED PERSON: Four, three, two, one.

(SOUNDBITE OF EXPLOSION)

BRUMFIEL: And there's all sorts of debris out here. You can see bent steel girders, blasted concrete. All these years later, it's still here.

(SOUNDBITE OF CAR DRIVING BY)

BRUMFIEL: Also lingering for years, the invisible fallout from these tests. Radioactive elements found their way into the water, the air, even the baby teeth of children living down wind at the time. That's part of the reason why in 1963, the U.S. and other nuclear powers signed a treaty to move nuclear weapons testing to tunnels deep underground. And that's where we're headed. We step into an old mining elevator...

(SOUNDBITE OF BEEPING MACHINERY)

DAVID FUNK: Watch your step getting onto the cage.

(SOUNDBITE OF CAGE CLOSING)

BRUMFIEL: ...And drop into pitch blackness. My ears pop as we descend nearly 1,000 feet to one of America's most secretive scientific laboratories. NPR was among a handful of news outlets allowed inside, and we were the only ones allowed to record the sounds of the lab deep underground.

(SOUNDBITE OF METAL BANGING)

BRUMFIEL: There's a long corridor that's been carved out of an ancient lake bed. Pipes along the walls carry air, water and power. Workers in hard hats are everywhere. David Funk, who oversees work underground leads us in.

How long have we had tunnels down here?

FUNK: Oh, so the tunnels were first built - well, these were dug in the '80s.

BRUMFIEL: So this would have been a test shaft, potentially?

FUNK: Yeah. This was designed to be nuclear test location originally, and now we do only subcritical experiments in this location.

BRUMFIEL: Subcritical experiments. That means experiments that simulate conditions inside a nuclear weapon without triggering a nuclear chain reaction. That runaway chain reaction is what gives a nuke its incredible power. These tunnels were originally built to contain nuclear explosions. Then in 1992, the U.S. officially stopped all testing. The Cold War had ended, and the thinking was, nuclear testing could end, too. It would make the world safer. But fast-forward to today, and nuclear weapons are back on the front pages. Same goes for nuclear testing. China, Russia and America are all upgrading their test sites. And that's why we're here to see what U.S. scientists are up to underground. Speaking of which, why do they still work down here?

FUNK: We do this because it is secure - right? - so we can control the environment. And we also are concerned about a potential breach of the vessel. And so we want to do it in an environment that's controlled, and we don't lose any of the plutonium into the environment.

BRUMFIEL: If something goes wrong.

FUNK: If something goes wrong, yeah.

BRUMFIEL: We arrive at our first stop - a long, empty corridor that's just been dug out for a new experiment.

FUNK: So this is where the Scorpius machine is going to reside.

BRUMFIEL: The Scorpius machine. It kind of feels like you're in a James Bond movie. Funk explains it's actually a giant X-ray machine.

FUNK: You guys are familiar with chest X-rays, right?

BRUMFIEL: Scorpius is going to work in the same way. It'll create extremely high-powered X-rays.

FUNK: And the reason is, we need higher energy X-rays to be able to look through plutonium.

BRUMFIEL: Plutonium from America's nuclear weapons. Much of it was made decades ago, and it's getting old. The X-rays are used to take a look inside to see how well the plutonium would work if detonated. Scorpius will cost $2 billion to build down here. We walk deeper into the tunnel network. Some of the floors are still rocky. They've just been dug.

(SOUNDBITE OF MACHINERY BEEPING)

BRUMFIEL: Next stop, an experiment that simulates a nuclear weapon. It's called Cygnus, and it's arguably the most secretive scientific project in the U.S. government.

FUNK: As reminder, we are going into no cellphones - any Bluetooth devices, smart watches, smart rings, if you have them, they need to go in the locker over here.

BRUMFIEL: Cygnus is a smaller version of Scorpius. It fires X-rays of plutonium that's inside a spherical steel container about the size of a mini fridge.

TIM BELLER: Watch your step entering.

BRUMFIEL: Tim Beller is directing the next test, code named Nob Hill.

BELLER: So that is the Nob Hill vessel. That's the actual vessel that we will use. That's a 3-footer.

BRUMFIEL: In a few months, inside this vessel, scientists will blow up a tiny quantity of plutonium using chemical explosives. It's designed to simulate a nuclear detonation. But again, this test will be subcritical. The U.S. government says there will not be a runaway nuclear chain reaction.

BELLER: Whatever rules they set, I ensure they happen here in Nevada.

BRUMFIEL: Globally, some arms control experts worry the rules might soon change. A treaty to permanently ban nuclear testing is stalled. Russia is developing new kinds of nukes, and China is dramatically increasing the size of its nuclear arsenal. Both countries are upgrading their nuclear test sites, just like the U.S. Don Haynes is a nuclear weapon scientist from Los Alamos National Laboratory, which built the first bomb in 1945. He says, there's no immediate need for the U.S. to test a nuclear weapon these days.

DON HAYNES: I think the question is more about, well, you know, if we return to testing, others might, who would gain more marginal benefits?

BRUMFIEL: Before nuclear testing ended in the '90s, China conducted just 45 tests. Many experts believe that they, more than anyone else, could learn a lot if nuclear testing were to resume. The U.S., by contrast, conducted more than 1,000 nuclear tests. Scientists like Haynes could conduct one more, a system test of an entire weapon, but right now...

HAYNES: Our assessment is that there are no system questions that would be answered by a test that would be worth the expense and the effort and the time.

BRUMFIEL: Still, he adds, the decision whether or not to test is above his pay grade. Ultimately, it'll be up to the politicians and the generals to choose whether America should detonate another nuclear weapon in these tunnels. From beneath the Nevada desert, Geoff Brumfiel, NPR News.

(SOUNDBITE OF SLEEPING AT LAST SONG, "SATURN") Transcript provided by NPR, Copyright NPR.

NPR transcripts are created on a rush deadline by an NPR contractor. This text may not be in its final form and may be updated or revised in the future. Accuracy and availability may vary. The authoritative record of NPR’s programming is the audio record.

Geoff Brumfiel
Geoff Brumfiel works as a senior editor and correspondent on NPR's science desk. His editing duties include science and space, while his reporting focuses on the intersection of science and national security.
Related Stories