A secret US nuclear weapons facility near Las Vegas may soon begin testing live bombs again as global tensions may be pushing countries into a new arms race.
Amid reports that both Russia and China are expanding and updating their nuclear facilities, officials with the US National Nuclear Security Administration (NNSA) say America may soon have no choice but to restart their weapons testing programs.
The US has not conducted a real-world test of a nuclear bomb since 1992. After decades of declining nuclear stockpiles, the nuclear agency sees a real possibility that more countries around the world – including India, Pakistan, and North Korea – are preparing to enter a nuclear arms race.
In the interest of transparency, US officials recently provided a tour of their own secret nuclear lab in Nevada, which from the outside looks like a bunch of harmless factory buildings and an old mining shaft.
Down a long tunnel, officials revealed three major components that researchers will be using to conduct weapons tests without actually setting off a nuclear bomb beneath the surface.
US government officials recently provided a tour of America’s most sensitive nuclear weapons research, conducted in a lab deep underground in Nevada.
On the surface, a mining hoist in the middle of a dry lakebed carries workers to the PULSE underground nuclear lab
These machines are responsible for checking on any decay taking place inside the radioactive cores of America’s aging bombs.
New, top secret devices will also be used at the underground lab later in 2025 to contain microscopic explosions – simulating the blast of an atom bomb.
NNSA invited journalists to the base known as the Principal Underground Laboratory for Subcritical Experimentation (or PULSE) WHEN?
NNSA administrator Jill Hruby’s goal was to allow the public to see what the US is doing with its nuclear stockpile and reveal how nuclear testing still takes place – without actually detonating a weapon of mass destruction.
While the base just looks like a collection of harmless buildings and an old mine shaft above ground, there is a busy facility carved into an ancient lakebed hiding below the surface.
‘This was designed to be a nuclear test location originally,’ said David Funk, who helps oversee work underground.
In fact, after live nuclear testing moved underground in the 1960s, Funk noted that some tunnels inside the PULSE facility were sealed off after one if the government’s last full-scale nuclear detonations in 1990.
Before the 1960s, the military would actually test nuclear explosions above ground, in deserts and at sea.
Although the US is not currently testing live nuclear weapons at PULSE and other nuclear labs, officials revealed that scientists still ensure these bombs are safe and reliable.
The US government previously conducted live nuclear detonations underground in Nevada, but those tests ended in the early 1990s
Currently, scientists use massive supercomputers to simulate the entire process of deploying and setting off a nuclear weapon
To do this, researchers use supercomputers to simulate the explosion of America’s nuclear weapons – taking the process all the way from ‘button to boom.’
Next, highly classified experiments, like the ones carried out at PULSE, conduct real-world testing of smaller explosions to make sure the supercomputers are providing accurate results.
These small-scale detonations are what nuclear researchers call ‘subcritical’ tests, meaning they don’t actually trigger a nuclear reaction.
A runaway chain reaction, where some atoms split apart and other fuse together, is what leads to the immense power of a nuclear bomb.
‘You didn’t need to do nuclear tests to do what you needed to do for the foreseeable future, which is to make sure the nuclear weapons you had worked,’ Kristensen told NPR.
As of 2023, the US Department of Energy reports that America has 3,748 nuclear warheads.
However, the nonpartisan Arms Control Association estimated that the number was significantly higher, putting the total at 5,225 as of January 2025.
Currently, progress on a treaty banning the testing of nuclear weapons has stalled, and there is already evidence that world powers are moving ahead with nuclear rearmament.
The US holds a large lead over other nations in nuclear testing. This atomic test took place on March 23, 1955, at the Nevada Test Site
This undated photo shows the craters created by underground nuclear explosions, which started in the 1960s
Inside the Nevada facility, US officials revealed how all of this testing takes place.
Down a long corridor full of pipes carrying air, water, and power throughout the complex, Funk revealed an empty space freshly dug out of the lakebed for PULSE’s newest ‘toy.’
‘This is where the Scorpius machine is going to reside,’ Funk explained.
The Scorpius machine is a giant X-ray machine, which scientists need to look through the plutonium at the core of nuclear bombs.
Plutonium serves as one of the primary fuels for nuclear weapons because the chemical element is ‘fissionable.’
This means its atom’s nucleus can be easily split by subatomic particles called neutrons, which can lead to violent atomic reactions.
Most of America’s plutonium has been sitting around for decades, leading to fears that the radioactive decay will damage the unused weapons.
Plutonium has five ‘common’ isotopes which have different rates of decay, ranging from just 87 years to over 24,000 years, according to the US Nuclear Regulatory Commission.
Ivan Otero, a nuclear weapons scientist at Lawrence Livermore National Laboratory, explained that, ‘Right now the oldest plutonium samples are about 80 years old.’
‘We need to know whether the helium bubbles or the damage to the lattice have a significant impact on the material response,’ he added.
The $2 billion Scorpius machine takes a series of X-ray images of the plutonium as a shockwave from a non-nuclear explosion passes through it.
This process tests the aging of a bomb’s plutonium core and helps the team to upgrade America’s current nuclear arms, if necessary.
Next, nuclear researchers showed off an area that houses a machine called ‘Zeus.’
The device bombards plutonium with neutrons to see how the metal behaves in a highly radioactive environment – like the core of an atom bomb.
Finally, the tour ended at one of the most top-secret experiments in the US, a project called ‘Cygnus.’
Project director Tim Beller unveiled a small, mini-fridge-sized metal sphere which scientists will use to test a small-scale explosion of plutonium later in 2025.
A small amount of the metal will be placed in the top-secret machine and blown up using chemical explosives.
The blast will only have a tiny fraction of a nuclear bomb’s true power, but the results will continue to help scientists refine America’s weapons safety standards.
Scientists are preparing new experiments that will study the plutonium cores of nuclear weapons at the secretive underground lab
US nuclear officials provided a look inside the facility, which will soon house brand new equipment for nuclear tests
So, if non-nuclear testing can effectively keep track of America’s nuclear weapons safety, why would the country start live experiments with real bombs again?
Experts say the US is walking a very fine line on this topic.
The nation currently has an enormous head start on most of the world when it comes to nuclear arms research.
Jamie Kwong, a fellow at the Nuclear Policy Program at the Carnegie Endowment for International Peace, explained that, ‘The US has a technical advantage locked in by this moratorium on nuclear testing because it undertook so many more tests during the Cold War period.’
However, if nuclear peace treaties continue to break down, several nations may soon catch up if the US decides to avoid real-world nuclear tests.
Project 2025, the controversial conservative plan for the US government published by the Heritage Foundation, suggests that the federal government should be able ‘to conduct nuclear tests in response to adversary nuclear developments if necessary.’
The Heritage Foundation’s Robert Peters said their idea, ‘is not just to start testing for giggles.’
‘If you’re engaged in high-stakes poker with nuclear weapons, I don’t want to box the president out,’ Peters added.
As for the scientists who would be involved in these dangerous experiments, some argue that real-world nuclear tests won’t reveal anything new that supercomputers and small-scale explosion aren’t already showing.
Don Haynes, a nuclear weapons scientist from Los Alamos National Laboratory, said, ‘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.’