Weapons surveillance

Because the United States does not detonate its nuclear weapons to ensure reliability, weapons must be surveilled—inspected inside and out to ensure they will work. Surveillance is a critical part of the Stockpile Stewardship Program, which—through nonnuclear experiments and computer simulations—gives scientists the confidence they need to ensure the safety, security, and effectiveness of the nuclear weapons in the U.S. stockpile.

“All U.S. weapon components are surveilled using both nondestructive and destructive techniques,” explains Sheldon Larson, Los Alamos Weapons Systems Surveillance group leader. “That begins with disassembling each weapon at the Pantex Plant near Amarillo, Texas.”

Nondestructive techniques leave the weapon fully functional and ready to go back into the stockpile, if needed. These techniques involve everything from visually inspecting the exterior of each component to using advanced imaging systems to examine the interior. A great deal can be learned from nondestructive techniques, such as how a weapon is aging and whether it has obvious defects.

“We think of it as a health checkup,” says Los Alamos surveillance engineer Miguel Santiago Cordoba.

From there, a down-selection process happens, and a small number of weapons are chosen for further testing, which involves destructive techniques. Some questions can be answered only by cracking open a weapon—and all of its parts and pieces. Destructive surveillance offers a more complete picture of a weapon’s health, but with the caveat that those components cannot return to the stockpile.

“We can’t destructively surveil all the weapons in the stockpile,” Cordoba explains. Not only would it be impractical to destroy and then rebuild the entire stockpile, but it would also be costly. Instead, destructively surveilling a small sample of weapons allows scientists and engineers to extrapolate the reliability of the larger population of weapons. “This sampling is enough to detect a 10 percent defect in the stockpile with 90 percent probability within two years,” Cordoba says.

“At Los Alamos, we surveil detonators and pits of nuclear weapons,” Larson says. Los Alamos has been a detonator production facility since the closure of the Mound Plant in 2003, in addition to its designation as a pit production facility. Whichever institution produces a specific weapon component is typically also the institution that performs the destructive surveillance. “Surveillance spans the nuclear weapon enterprise,” Larson explains. “It involves all of the National Nuclear Security Administration’s sites and all of the weapons systems. It’s a very interactive and collaborative partnership.”

Surveillance is also an ever-changing field because technology is advancing at a rapid pace. The surveillance tools and techniques available now were impossible at the time these parts were made, back in the Cold War. “We are always looking to improve our technologies,” Larson says. “For example, now we can see inside components in 3D, something we couldn’t do back when these pits were originally made. We have a lot of tools in our toolbox now, and we have to know when to use what.”

Surveillance is a complicated task, especially when anomalies are detected. There isn’t a one-size-fits-all approach to test and mitigate an anomaly. New techniques, methods, and assessments are constantly being added to the surveillance repertoire as new situations are observed—the aging nuclear enterprise is not without surprises.

Even those who have been working in surveillance for more than 25 years, such as Patrick Rodriguez, a seasoned surveillance engineer, say they still learn something new every day. “We are at the intersection of many sciences, involved with everyone at all different levels with all different needs.” By this, Rodriguez is referring to the physicists and engineers who rely on surveillance data, the technicians and technologists who help acquire that data, and the managers and directors who use the interpretation of that data to guarantee the stockpile.

The culmination of annual surveillance (along with weapon simulations and subcritical experiments, which round out the Stockpile Stewardship Program) is the Annual Assessment Letter—a letter to the president from the directors of Los Alamos, Sandia, and Livermore national laboratories that certifies the safety and reliability of all the weapons in the stockpile. Making that guarantee takes the ingenuity, dedication, and critical thinking of many people across the Laboratory.