The United States has an arsenal of some 3,800 nuclear weapons, about half of which are deployed, with the rest in storage. The Department of Energy’s National Nuclear Security Agency (NNSA) and the nuclear weapons laboratories it oversees are concerned that the performance of the weapons will degrade over time. Most of the components can be—and are being—replaced with new versions, so the main concern is the behavior of aging plutonium “pits” at the core of all U.S. weapons.

Plutonium essentially doesn’t exist in nature but is produced in nuclear reactors. It was first produced during World War II, and the U.S. government didn’t care about pit aging because it constantly replaced pits with newly built ones as it upgraded its arsenal during the Cold War.  So, no one in the weapons labs knew what the lifetime of a pit was. Instead, the NNSA simply assumed it was 45–60 years.

And during the Cold War, the U.S. produced a lot of pits, tens of thousands. It stopped in 1989 when the production plant was shut down by the FBI and the EPA due to pervasive environmental damage. Los Alamos National Laboratory in New Mexico manufactured 31 pits between 2007 and 2013, but none since. That means virtually all the pits in today’s arsenal were made 30–40 years ago, which would have meant serious problems for the stockpile starting in 2025 if the NNSA’s assumption were correct.

So, what is the lifetime of a pit?

In 2005, Congress tasked JASON, the independent science advisory group, with answering this question. Their groundbreaking 2007 report examined the data the weapons labs had produced and concluded that most weapons system types in the stockpile “have credible minimum [emphasis added] lifetimes in excess of 100 years as regards aging of plutonium.” Moreover, this minimum age would also apply to the remaining types once straightforward adjustments were made. This finding significantly reduced pressure to resume large-scale production of pits for some time.

Last year, Congress—led by Sen. Dianne Feinstein (D–Calif.)—sensibly asked JASON to update its earlier work. Unfortunately, JASON’s new, very brief “letter report" contains zero new information on pit lifetimes.

What went wrong? Did JASON fail to do its job? Or was the group unable to do it?

When asked this question, an NNSA official confirmed that it was a lack of data, not a failure by JASON, that prevented an update on the 2007 estimates. JASON’s report states: “A focused program of experiments, theory, and simulations is required to determine the timescales over which Pu [plutonium] aging may lead to unacceptable degradation in primary performance.”

JASON lays the blame for this failure squarely on the NNSA, declaring that “in general, studies on Pu aging and its impacts on the performance of nuclear-weapon primaries have not been sufficiently prioritized over the past decade.”

It seems entirely possible that this was not an oversight on the part of NNSA but reflects that the agency does not want to know the answer. The NNSA wants to produce new types of warheads, not just refurbish existing ones. That requires the ability to produce new pits in bulk.  If minimum pit lifetimes were 200 years, then there would be no need for new pit production to maintain existing weapons. The cost of pit production would then be entirely attributed to new weapons and the price tag for those would increase substantially, making it less likely that Congress will give NNSA the go-ahead.

Instead of studying pit lifetimes, the NNSA has focused on major upgrades for three existing nuclear weapons, a new uranium processing facility and, notably, one all-new nuclear weapon—the first since the end of the Cold War—that will require production of new plutonium pits.

And, not coincidentally, the Trump administration and many in Congress are pushing a plan to produce at least 80 pits per year by 2030. The rationale they offer is disarmingly simple: if the U.S. has roughly 4,000 nuclear weapons and pits last 100 years, then the NNSA needs to produce 80 pits per year starting in 2030 to be able to replace the entire stockpile by 2080.

But what if plutonium pits last longer than 100 years? Deferring production of new pits would significantly reduce the stress on the NNSA’s infrastructure, already struggling under a workload many times heavier than at any time since the end of the Cold War. It would also save tens of billions of dollars.

However, the all-new warhead, known as the W87-1, would need new plutonium pits. The NNSA estimates the W87-1 will cost $11–16 billion, not including the money needed to produce the new pits, which adds another $14–28 billion.

Moreover, another recent independent study mandated by Congress found that the current timeline and cost estimate for pit production are not realistic. The May 2019 study by the Institute for Defense Analyses concluded that the 80 pits per year goal was “potentially achievable given sufficient time, resources, and management focus, although not on the schedules or budgets currently forecasted…. Put more sharply, eventual success of the strategy  to reconstitute plutonium pit production is far from certain.” (Emphasis added.)

In other words, producing 80 pits per year may be possible, but it will not happen by 2030 and it will cost more than current projections.

This makes an updated estimate on pit lifetime even more important.

Congress should put the NNSA’S feet to the fire. Sen. Feinstein, sponsor of the JASON study, is the ranking member of the Senate committee that oversees the NNSA. She should push the committee to direct the NNSA to undertake the “focused program” that JASON recommends, now. The answer will determine whether the U.S. needs to spend tens of billions of dollars in a rush to produce pits, or whether it can sensibly and safely postpone that decision.