The U.S. defense budget, which the House of Representatives passed this week largely along party lines, includes a provision that could ramp up the required capacity for plutonium pit production at Los Alamos National Laboratory.

The lab is currently the only facility in the nation capable of producing the pits, which serve as the trigger devices for nuclear weapons.

The nation's "nuclear security enterprise" would be required to have the "capability to reliably produce" at least 180 war reserve bomb cores annually by 2050 under a provision in the National Defense Authorization Act.

The requirements in current federal law are lower and shorter-term, requiring the production of 80 pits annually by 2030, with at least 30 produced at Los Alamos.

The bill, passed by the House on Wednesday, now heads to the Senate, where it faces an uncertain path forward: Senate Democrats in mid-July blocked the passage of the defense bill, protesting the ongoing conflict in Iran.

Greg Mello, director of the Los Alamos Study Group — a longtime anti-nuclear weapons organization — raised alarm about the proposed capacity increase, saying it could justify "immense investments" in expanding capacity at Los Alamos.

"Why would someone in Congress think that they should decide nuclear policy six or seven administrations from now in such a gratuitous manner?" Mello said in an interview Friday.

The nuclear security enterprise has planned to eventually manufacture pits both in New Mexico and at the Savannah River Site in South Carolina; the latter has faced delays and is not yet producing the pits.

"As far as we can tell, the purpose of this is to commit the federal government to supporting the expenditure of a large amount of money in both New Mexico and South Carolina for the next quarter-century and beyond," Mello said, adding it could cost "many billions" to carry out this requirement.

All three New Mexico representatives voted against the defense bill, which has become a flashpoint over the war in Iran. Only six Democrats in the House voted for the bill.

Members of New Mexico's congressional delegation didn't immediately respond to requests for comment Friday about the plutonium pit provision.

Although plans long have called for the production of 30 pits per year at LANL, a National Nuclear Security Administration official said earlier this year that could increase to 60.

In 2024, the lab announced it had produced its first “diamond-stamped” pit — one ready to be deployed to the nation’s nuclear stockpile — as part of the new mission. LANL previously produced a small number of pits between 2007 and 2011 as the first site to resume production since the shutdown of Colorado's Rocky Flats in 1989.

The lab is approaching the mission with a newfound urgency, Los Alamos National Laboratory Director Thom Mason said at a town hall last month, driven by geopolitical conflict. In the post-Cold War era, Mason said the nuclear enterprise wasn’t well-equipped for “rapid response.” 

That urgency could mean big dollars for the lab, which already has seen its budget double since 2019. The federal budget for fiscal year 2027 proposed in April showed the Los Alamos lab's share would be nearly $6.8 billion, up from a current $5.1 billion. 

While it's unclear how many diamond-stamped pits the lab has produced since 2024 — Mason said earlier this year the number cannot be disclosed — he said at the town hall LANL was exceeding expectations.

“We’re in the middle of what’s looking to be a very successful year, where we’re ahead in terms of both the production goals and the infrastructure work that we’re doing,” he said.

Earlier this year, a National Nuclear Security Administration official also said the lab had increased its limits on the dose of external and internal radiation a worker can receive in a given year without prior approval.