Small but mighty

“Extremely small and extremely important.” That’s just one of the ways Los Alamos National Laboratory’s Detonator Manufacturing Office leader Jim Shipley describes the detonators that the Lab builds. Los Alamos is the only place in the country that manufactures detonators for nuclear weapons.

Because different weapons use different types of detonators, Los Alamos currently manufactures seven different types of detonators simultaneously. Five of these types were designed at Los Alamos, and the other two were designed by scientists at Lawrence Livermore National Laboratory.

In 2023, the Lab delivered more than 3,000 detonators to the National Nuclear Security Administration, which oversees all aspects of nuclear weapon design, maintenance, and production. “The detonators are built in lots of a few hundred and it typically takes about a year to build a full lot of detonators,” Shipley says.

After building a lot, the team pulls a certain number of detonators out to test them. “The tests ensure they meet the specifications, which are highly exacting as we are a production agency building parts for the nation’s nuclear stockpile,” Shipley says.

Shipley describes the products his division makes as “crucial.”

“Without detonators, you don’t have a nuclear weapon that will operate,” he says. “It’s a key thing that has to work. Not that it’s more important than any other component in the weapons system, but you must have detonators for the system to work.”

A nuclear weapon detonates in a carefully choreographed sequence in which detonators trigger the high explosives surrounding the plutonium pit at the core of the weapon. The resulting explosion causes the pit to compress and implode, initiating a nuclear reaction.

The first step of this process begins when an electrical charge or a laser (depending on the type of detonator) within the detonator produces a shockwave that triggers a small amount of included explosive material. This detonator explosive then triggers the larger quantity of high explosives surrounding the pit.

“The way detonators work is fascinating,” says Shipley. “The physics is so complex, and the timescales are so short.”

The Lab is exploring the merits of using detonators that use optical energy instead of electricity to set off the internal explosion. By using radiation at a specific wavelength, an optical detonator removes the hazard posed by electrical initiation and reduces the risk of accidental detonation.

However they are initiated, the detonators, the explosives inside them, and the explosives surrounding the pit must all work together to ensure a successful nuclear reaction. Because of this, the scientists who design and produce detonators work closely with the scientists who design and produce explosives. Conveniently, those scientists work at Los Alamos as well, which makes collaborating easier for everyone involved, according to Margo Greenfield, High Explosives Sciences and Technology group leader.

“We collaborate closely with the Detonator Production team,” Greenfield says. “We provide the explosive, we conduct studies of how the detonators and the explosives are aging, and we work together to solve problems.”

One way detonator and explosive aging are assessed is through a process called  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. During destructive surveillance, weapons are disassembled and detonators are removed, examined, and tested by initiating a detonation and analyzing the result.

Shipley says many people are surprised to learn how tiny yet powerful the detonators are. “We work on such very small things, but we have a very large sense of pride,” Shipley says. “The employees in Detonator Production are invested in the national security mission. We are proud of our contributions manufacturing this small but essential part.” ★