A provision put into the military spending bill recently signed by President Joe Biden bars Los Alamos National Laboratory from expanding its ability to convert plutonium into radioactive powder until the lab certifies it can produce 30 nuclear bomb cores, or pits, per year.

That restriction will delay for years a plan to have the lab take in 34 metric tons of Cold War plutonium pits from the Pantex Plant in Texas, convert them to oxidized powder, then ship it to the Savannah River site in South Carolina, where it would be diluted for eventual disposal at an underground site in southeastern New Mexico.

The plan drew opposition from activists, some state leaders and many residents because the plutonium would be trucked back and forth across a dozen states — with radioactive materials going through Santa Fe and Los Alamos counties twice.

“It’s the best news I’ve heard,” said Santa Fe County Commissioner Anna Hansen, a staunch opponent of the dilute-and-dispose plan.

The U.S. Energy Department’s nuclear security agency released the 412-page plan a year ago, describing the need to “downblend” the plutonium leftover from the Cold War so the radioactivity would be low enough to be accepted at the Waste Isolation Pilot Plant near Carlsbad.

WIPP opened a quarter-century ago with the aim of taking transuranic waste, made up mostly of irradiated gloves, clothing, equipment, soil and other items.

The plan called for expanding the lab’s ARIES operation (the acronym stands for Advanced Recovery and Integrated Extraction System), which now oxidizes plutonium on a small scale. Boosting the quantity would require installing more glove boxes — the sealed compartments that allow workers to handle radioactive materials — and other equipment to the plutonium facility. The additions would expand the facility to 6,800 feet from 5,200 feet.

The new law is putting those proposed changes on hold until the lab can certify its ability to make 30 bowling ball-sized pits a year. Current estimates for reaching that production volume is between 2028 and 2030.

National Nuclear Security Administration officials said Thursday they needed more time to answer questions about the new law and when the lab might achieve the required certification.

According to the law: “Until the date on which the [NNSA] Administrator certifies to the congressional defense committees that the base capability to produce not less than 30 war reserve plutonium pits per year has been established at Los Alamos National Laboratory, the Administrator may not ... carry out a project to expand the pit disassembly and processing capability of the spaces occupied by ARIES or ... otherwise expand such spaces.”

Critics have expressed concerns about a steady stream of plutonium coming into the region and have bashed federal agencies’ efforts to sidestep WIPP’s restrictions, saying even diluted plutonium shouldn’t be allowed there.

Cindy Weehler, who co-chairs the watchdog group 285 ALL, said she had mixed feelings about the dilute-and-dispose plans being delayed, arguing it’s “kicking it down the road.”

“What we’re thinking is, of course this is good,” Weehler said. “But as we talk to them and listen to them in meetings — DOE and WIPP officials — they still talk about excavating 19 [storage] panels ... and operating WIPP through 2083. Those two things tell me that they are fully on board for all of this waste, just not yet.”

A panel is a chamber for embedding containers of nuclear waste in salt caverns roughly 2,150 feet underground. New state regulations require disposal of legacy waste to take priority over new waste generated by pit operations.

Weehler said she’s glad the state imposed conditions on WIPP’s hazardous waste permit to require more emphasis on cleaning up Los Alamos’ waste from the Cold War. That’s especially needed for the stuff still stored in open areas on the site, she added.

But there’s nothing to permanently stop the old plutonium pits at Pantex from being turned into oxidized powder at the lab in the future and hauled through the Santa Fe area, Weehler said.

The idea of doing away with surplus plutonium began after the Cold War. In 2000, the U.S. and Russia agreed to each eliminate 34 metric tons of plutonium so it could no longer be used in nuclear weapons.

Russia reportedly later withdrew from the pact, but the U.S. decided to stick to its commitment.

The Energy Department originally sought to build a Savannah River facility that could turn Cold War plutonium into a mixed oxide fuel for commercial nuclear plants.

But after billions of dollars in cost overruns and years of delays, the Trump administration scrapped the project in 2018 and decided to go with diluting and disposing of the waste.

The lab is now the only site with an ARIES program, though the law doesn’t prevent a similar operation from being established elsewhere, said Don Hancock, director of nuclear waste safety for the nonprofit Southwest Research and Information Center.

In any case, it will take at least several years for the federal government to reliably certify the 30-pit-per-year capability, giving residents who live along the trucking routes a reprieve from the dilute-and-dispose plan, Hancock said.

“That’s good news for people ... who oppose that dangerous activity,” Hancock said.