Ask a Scientist: New Plutonium Pits for Nuclear Weapons Are Not Needed

June 12, 2025 | 9:39 am
photo of a gloved hand holding a plutonium pit, which appears to be a gray metallic discUS Department of Energy
Abby Figueroa
Editorial Director

The United States is planning a $1.7 trillion overhaul of its entire nuclear arsenal, designing new warheads and investing in new bombers, missiles, and submarines to carry them. The new warheads, in turn, are driving demand for new plutonium “pits”—the bomb cores that begin the chain reaction in every US thermonuclear weapon.

According to a new report by Dylan Spaulding, senior scientist at the Union of Concerned Scientists and an expert on nuclear materials, this plan is not only expensive and technically unnecessary, but also hazardous and politically destabilizing. We asked him to dig into the details.


AAS: Why are new plutonium pits unnecessary?

DYLAN SPAULDING: One of the most frequently cited reasons for resuming pit production is that our existing weapons are aging. That’s true, but the plutonium within them is nowhere near the end of its life, nor does it appear to degrade as dramatically as some fear, according to the available science. In addition, most weapons in the US nuclear stockpile have undergone refurbishment relatively recently, replacing components that do age, to ensure their ongoing reliability.  

That said, the new pits being proposed aren’t even intended to refresh the nuclear weapons we already have. Instead, they are expected to go into new nuclear warheads—the first newly designed and built nuclear weapons that the United States will introduce since the end of the Cold War. What’s more, the United States has thousands of pits sitting in storage from weapons that have been retired from the nuclear arsenal, and at least some of those should be suitable for reuse.

If the United States were to continue its practice of refurbishment rather than building new warheads or, better yet, work towards reducing the size of its arsenal, there would be no rationale at all for making new plutonium pits.

AAS: What are the risks or impacts of this plan?

DYLAN SPAULDING: Past plutonium pit production left behind a legacy of irreversible contamination at Hanford Nuclear Site in Washington and Rocky Flats in Colorado. Much has been learned about how to work with plutonium more safely, but this work always carries risks, particularly to workers in the event of accidents. The plutonium facility at the Los Alamos National Laboratory in New Mexico was shut down for three years because of safety violations, and minor accidents continue to occur regularly there, including small fires, flooding within gloveboxes, and exposure of workers to plutonium.

Communities near the two proposed production sites (Los Alamos and the Savannah River Site in South Carolina) are justifiably worried about their potential exposure in the event of an accident and as a result of contamination from decades-old waste that isn’t yet remediated.

As far as new pit production goes, the Department of Energy is trying to rush this program forward to meet an arbitrary and unnecessary deadline imposed by Congress. The processes to fabricate new pits are inherently dangerous, using dangerous materials, and the workforce that will be responsible for carrying out pit production lacks experience and will be relying on new equipment and protocols. When you add time pressure, that’s a very dangerous combination.

AAS: The production process creates radioactive waste. What will be done with it?

DYLAN SPAULDING: The United States only has one place to dispose of its radioactive waste and that is the Waste Isolation Pilot Plant (WIPP) in southern New Mexico. Much of the waste from plutonium pit production will be sealed in drums and interred in tunnels deep underground there. That facility faced a multi-year shutdown as a result of two accidents in 2014, and it’s not clear that it will have the required capacity, nor that the state will agree to extend its license indefinitely. As its name suggests, it was meant to be a pilot project, not the nation’s only long-term waste storage site. Right now, there is no choice but to rely on it, which creates a sort of Achilles’ heel for the entire US nuclear weapons production program. The national labs are beginning to create a whole new waste stream that they may not be able to manage.

AAS: You say the plan would actually decrease national security—in what way?

DYLAN SPAULDING: One of the newly proposed warheads, called the W87-1, is intended to go on a new intercontinental ballistic missile (ICBM) called Sentinel. These silo-based missiles are on hair-trigger alert, meaning they can be launched at a moment’s notice upon warning of any incoming threat. Indeed, if they are targeted, they must be launched to avoid being destroyed because their positions are well known. The US president has the sole authority to order such a launch and has only about 10 minutes to decide whether to do so if a potential attack is detected. This risks starting a nuclear war by mistake.

If this country’s ICBMs were attacked, hundreds of millions of people in the United States could be at risk from the subsequent fallout, as shown by research conducted at Princeton. Rather than perpetuating this unstable and dangerous status quo, the United States could simply decide to retire its ICBMs and avoid the costly refurbishment of their silos and command structure and the building of new warheads.  

Even without its land-based missiles, the United States has secure options for nuclear retaliation. US submarines at sea cumulatively carry roughly 5,000 times the destructive force of the Hiroshima bomb. Submarines and bombers also allow more decision time before launching an attack, bombers can be recalled, and submarines are not targetable in the way land-based missile silos are—meaning they don’t increase the risk of a mistaken launch. Given that, it’s hard to fathom why US strategists feel they should maintain land-based missiles at a cost of well over $200 billion just to produce them.

AAS: What should the United States be doing instead to improve safety and security?

DYLAN SPAULDING: At UCS, we say introducing new weapons and new delivery systems (new bombers, ICBMs, and nuclear-capable submarines) is ultimately destabilizing and encourages the same kind of Cold War thinking that leads potential adversaries to respond in kind in an unwinnable arms race.

It was President Reagan and Russian President Gorbachev who said, “A nuclear war cannot be won and must never be fought.” Neither can an arms race. The Cold War demonstrated that more weapons do not create more security. Instead, they heighten risk and discourage arms control agreements and nonproliferation efforts in regions where countries may wish to acquire their own nuclear weapons.

A better approach would be for the United States to exercise restraint and work towards further arms reductions rather than doubling down on its dependency on the nuclear arsenal for perceived security. Not only could this avoid the better part of a multi-trillion-dollar modernization program, but it would reassure the world that the United States has learned the lesson from the Cold War that such competition “cannot be won.”