Sandia National Laboratories marks completion of new nuclear gravity bomb

Sandia National Laboratories heralded a milestone at the end of May: the first of a new type of nuclear gravity bomb was built ahead of schedule.

The first B61-13 production unit was completed at the Pantex Plant in Texas, but Sandia was responsible for building many of the weapon’s nonnuclear components. Los Alamos National Laboratory was involved in development and testing of the weapon.

“The remarkable speed of the B61-13’s production is a testament to the ingenuity of our scientists and engineers and the urgency we face to fortify deterrence in a volatile new age,” Energy Secretary Chris Wright said in a statement.

While finishing the new bomb a year ahead of schedule was celebrated by Wright, an antinuclear advocate is concerned the effort to modernize U.S. nuclear weapons is fueling a new nuclear arms race.

The B61-13 was completed two years after it was announced. That makes it the most rapidly developed and fielded weapon since the Cold War, according to an Energy Department news release.

The U.S. is not increasing its number of nuclear weapons with the new bombs. Instead, the B61-13s will replace some of the country’s B61-7 gravity bombs, which have a similar yield.

“This is just one little segment of the $2 trillion so-called modernization program that is really a program to keep nuclear weapons forever,” said Jay Coghlan, executive director of nonprofit Nuclear Watch New Mexico. “So what we’re seeing is every warhead in the existing stockpile is being refurbished to extend its service life by decades, and also being given new military capabilities.”

The number of B61-12s — the 13’s immediate predecessor — being produced was reduced so that the overall stockpile number would remain the same. Production on the B61-12 came to an end last year.

“The reason it was possible to move so quickly is the similitude between the two bombs, the B61-12 and the B61-13,” Lysle Serna, a Sandia manager who began working on the prior bomb evolution in 2020, said in a statement.

The bombs have similar safety, security and accuracy features. The main difference between the 12 and the 13 is power. The yield, or amount of energy released when the nuclear weapon is detonated, is higher for the new bombs. The new B61-13s are approximately 300 kilotons. The B61-12’s maximum yield is 50 kilotons. The bomb the United States dropped on Hiroshima was estimated at 15 kilotons.

With the first production unit complete, the B61-13 program will go through design review and work to transition to a full-rate of production.

B61-13 bombs are designed for hardened underground targets.

“It’s the kind of nuclear weapons that would likely be used against the Iranian uranium enrichment plant at Fordo, and that’s the plant that the Israelis are not capable of destroying because it’s buried so deeply underground,” Coghlan said. “Now, I’m not saying that the U.S. is going to use it, but I am saying the B61-13 is being developed and produced to attack that kind of target.”

Production of the B61-13s will cost an estimated $92 million over the next four years, according to a National Nuclear Security Administration budget document.

The remaining nuclear arms control treaty, the New Strategic Arms Reduction Treaty, expires February 2026. It caps strategic warheads at 1,550. Russia and the U.S. first entered it in 2011 and extended it in 2021.

“But that goes away in February, and there’s already strong signs that the U.S. will numerically add to its stockpile,” Coghlan said. He pointed to a report from the Congressional Commission on the Strategic Posture of the United States released in October that concluded the country needs to prepare to address threats from Russia and China.

“These threats are such that the United States and its allies and partners must be ready to deter and defeat both adversaries simultaneously,” the report says.