Behind the Scenes at a U.S. Factory Building New Nuclear Bombs

The workers who make pits face these risks every day

The U.S. is ramping up construction of new “plutonium pits” for nuclear weapons

Scientific American, BY SARAH SCOLES 1 Dec 23 [excellent illustrations]

This article is part of “The New Nuclear Age,” a special report on a $1.5-trillion effort to remake the American nuclear arsenal.

Within every American nuclear weapon sits a bowling-ball-size sphere of the strangest element on the planet. This sphere, called a plutonium pit, is the bomb’s central core. It’s surrounded by conventional explosives. When those explosives blow, the plutonium is compressed, and its atoms begin to split, releasing radiation and heating the material around it. The reaction ignites the sequence of events that makes nuclear weapons nuclear.

In early nuclear bombs, like the ones the U.S. dropped on Japan in World War II, the fission of plutonium or uranium and the fatal energy released were the end of the story. In modern weapons, plutonium fission ignites a second, more powerful stage in which hydrogen atoms undergo nuclear fusion, releasing even more energy. The U.S. hasn’t made these pits in a significant way since the late 1980s.

But that is changing. The country is modernizing its nuclear arsenal, making upgrades to old weapons and building new ones. The effort includes updated missiles, a new weapon design, alterations to existing designs and new pits. To accomplish the last item, the National Nuclear Security Administration has enacted a controversial plan to produce 50 new pits a year at the Savannah River Site in South Carolina and 30 pits a year at Los Alamos National Laboratory in New Mexico, the birthplace of the bomb. The first pits will be designed for a weapon called W87-1, which will tip the new intercontinental ballistic missile, called Sentinel. After that the complex will produce pits for other bomb designs.

Not everyone believes this work is necessary. Pit production foments controversy because it’s costly and potentially risky and because the existing pits might still work for a while. The physics of plutonium is complex, and no one knows when the original pits will expire. The details of how the pits are made and how they work are among America’s most closely guarded secrets. Yet in June 2023 Los Alamos officials invited a group of journalists to tour the facility for the first time in years.

We were there as the lab and the broader National Nuclear Security Administration Complex were embarking on a charm offensive to support the new plutonium work. They have to win over the tax-paying public and recruit some 2,500 new employees for the job. Some of those workers must do high-hazard work that requires expertise the country has largely let slip since the last days of the cold war. ………………………………………………………………………………………………………………..

…………………..The plutonium used for weapons exists only because people made it.

……………………………………………….. …….Plutonium’s genesis was repeated in reactors for decades. In fact, scientists made so much that no new plutonium is required for the new pits at Savannah River and Los Alamos—the current supply can be repurposed, reshaped, reborn.

None of those actions, though, will be simple because plutonium is not simple……………………………………………………………………………………….. Its most famous trick, of course, is its propensity for radioactive decay, through which it transforms itself out of existence.

This tendency is also what makes it so dangerous. Inhaled plutonium decays in the body, releasing alpha particles (helium nuclei) that can wreak havoc. The isotope plutonium 238, used as a heat and power source but not in weapons, exhibits other strange behaviors. “If you spill it in the laboratory, it will move around on its own,” Martz says. The oomph from a plutonium atom’s decay sends it shooting across a surface. “It can get everywhere,” he adds.

Plutonium’s strangeness comes from its arrangement of electrons……………………………………………………………………………………………………………………………………………………………………..

In the excitement of these early scientific discoveries, the point of the work would sometimes get lost: it was all in the service of creating a deadly superweapon. In 1945 the U.S. dropped a uranium fission bomb on Hiroshima and then sent a plutonium bomb—essentially a pit encased in explosives—to devastate Nagasaki. The bombs killed tens of thousands of people immediately and more after the fact. As Manhattan Project physicist I. I. Rabi had feared, according to a quotation in the 2005 book American Prometheus, “the culmination of three centuries of physics” was a weapon of mass destruction.

Soon after the war, production of plutonium pits migrated to a facility outside Boulder, Colo. Called Rocky Flats, it could churn out thousands of pits a year—a level of productivity perhaps enabled by its violation of environmental regulations, which in 1989 resulted in a federal raid and then a permanent shutdown. “The public wasn’t considered at the time,” says Bob Webster, deputy director of weapons at Los Alamos. ………………………………………………………………………………………………………………………………….

How aging affects a pit is the subject of contention, but some things are certain: As the plutonium atoms in a pit decay, their products damage the crystal structure of the plutonium that remains, creating voids and defects. These decays also contaminate the pit with helium, americium, uranium and neptunium, among other things. In 50 years a kilogram of plutonium will amass around 0.2 liter of helium. As pits change, their performance and safety in any conditions—including just sitting on a shelf—become questionable.

Scientists still don’t know the lifetime of a plutonium pit. …………………………………………………….. The National Nuclear Security Administration’s own studies have suggested the pits will last at least 150 years but also that their degradation could result in surprise defects. And scientists may never know exactly what those defects do or how they would affect an explosion because the ostensible point of nuclear weapons is to never use them.

So far restarting American pit production is proving challenging. Los Alamos’s efforts are at least a year behind schedule, and Savannah River’s are more like five years delayed.

The Defense Nuclear Facilities Safety Board and other critics have claimed that PF-4 isn’t resilient enough against the kind of earthquake geologists now know could occur in Los Alamos. Such significant shaking and the fires it could cause, the board alleged at a hearing last year, could result in plutonium contamination that reaches the public.

……………………… Other safety concerns have come up recently, though. In May the National Nuclear Security Administration released an investigation about four 2021 incidents: one criticality safety violation, one breach that resulted in skin contamination for three workers, and two flooding events that sent water toward fissionable materials. The agency determined that the contractor that manages Los Alamos had violated safety, procedural, management and quality-assurance rules.

………………………………………………………………………………………….. On the tour, we are forbidden from setting our notebooks down lest potential contamination stick to them. Should we drop them, a radiological control technician—who has been following us the whole time and scans our hands and feet for radioactivity anytime we leave a room—would measure each page before returning them.

…………………… In some rooms, radioactive waste is packaged and waiting to go to a storage facility, with the dosage one might receive from standing near it written on the ground. We are never allowed to forget that this is a dangerous place.

The workers who make pits face these risks every day………………………………………………………………………………

All of this effort and investment is being made in the hopes that the pits never serve their active purpose. The U.S., like all nuclear nations, stockpiles weapons in a delicate game of deterrence, the idea being that the existence of our equally or more capable weapons will stop others from using theirs. In this strategy, the pits’ true purpose is to sit idly as a threat. But for the strategy to work, the country must be willing to follow through on that threat.

……………………………………. The fear people feel when confronted with plutonium has degraded over time. But the atomic age is renewing, and we will all have to grapple afresh with the coiled terror of these powerful weapons. https://www.scientificamerican.com/article/behind-the-scenes-at-a-u-s-factory-building-new-nuclear-bombs/