The robust budgetary and employment growth Los Alamos National Laboratory has experienced in the past five years as it worked toward ramping up production of nuclear bomb cores is waning and probably will remain at a plateau in the foreseeable future, the lab’s head said Wednesday.

Last year, the lab hired 2,500 workers, the most ever, but that growth is expected to slow from this historic peak, even as the lab works toward manufacturing 30 plutonium pits a year for warheads, lab Director Thom Mason said during an online town hall.

“We are pivoting from what has been pretty rapid growth,” Mason said. “Going forward we’re going to see that growth tapering off.”

The lab employs about 18,000 people, he said. About 15,000 are regular employees and the rest are a mix of contractors, students, fellows and other temporary personnel.

Mason expects employment to stay close to this level, with new hires mainly replacing workers who quit or retire.

Continuing intense employment growth isn’t necessary nor is it practical given Los Alamos’ lack of housing, which contributes to about 60% of lab employees living outside the county, Mason said.

The lab also saw its budget swell to an all-time high of more than $5 billion.

Almost $2 billion of that is for pit operations and modernizing the plutonium facility.

Mason reiterated the need for the lab and Savannah River Site in South Carolina to produce a combined 80 plutonium cores yearly to modernize the U.S. nuclear arsenal as Russia, China and other countries improve their first-strike capabilities and take a more assertive posture.

Dylan Spaulding of the Union of Concerned Scientists asked how much the lab’s production could surge reliably beyond 30 pits if some unforeseen problem required it do so.

Spaulding was echoing concerns of nuclear watchdogs who wondered whether the lab might be pressured to make more pits because Savannah River’s timeline for producing its first pits was extended to the mid-2030s.

Mason replied the lab’s plutonium facility was capable of making much more than 30 pits in a year.

Increasing production by any significant amount would require building another facility, he said, “which is not currently contemplated.”

Mason said people often question whether the increased pace of work is resulting in more worker safety lapses.

He said that’s not the case. It serves the lab better to be safe and avoid incidents that shut down operations, he said, adding disruptions thwart the lab in meeting the goal to produce 30 pits by the late 2020s.

But in an email sent after the meeting, a watchdog group challenged that assertion.

“Mason dismissed serious safety concerns by claiming that ‘safety enables production,’ ” wrote Jay Coghlan, executive director of Nuclear Watch New Mexico. “However, LANL’s track record speaks otherwise. Nuclear safety problems will inevitably increase with expanded plutonium pit production as the last few months have shown with a half dozen nuclear safety incidences.”

During the town hall, Mason insisted the number of safety incidents is not increasing, but rather more are being reported than in the past, including minor ones, to promote greater transparency.

“Overall, we’re seeing positive trends,” Mason said of worker safety.

Several people asked about the lab’s plans to install a third high-voltage transmission line, which would stretch 14 miles from the lab through White Rock Canyon, south across the Caja del Rio area and then east through the Santa Fe National Forest to a substation.

Mason said a third line was needed as a backup energy source and to power supercomputers.

The lab is installing two new supercomputers, one for defense and one for artificial intelligence, he said.

Additional power also will be needed for the next generation of supercomputers in the coming decade, he added.

“In the 21st century, if we don’t maintain a leading-edge capability in high-performance computing, we will not be a relevant research institution,” Mason said.

He said the plateau’s steep terrain and other factors prevent the lab from installing extensive renewable energy components. Instead, the lab is looking to buy wind- and solar-generated power from outside sources, he said, but a new transmission line is needed to get that power up the hill.

When asked about the four traffic cameras the lab is installing on East Jemez Road — mainly as visual devices to discourage speeding and reckless driving — Mason said it was a necessary measure after serious accidents in the area, including a deadly one.

The U.S. Energy Department owns the road, making it a lab site, he said. Although the lab can’t issue speeding tickets, it wants to foster safe driving on a road it oversees, he said.

“The most dangerous thing that employees of Los Alamos lab do is driving to work and going home,” Mason said.

“We do need people to slow down. On our site, I view safe driving as a workplace safety issue.”