Metal to powder

The ARIES program alters plutonium so that it can’t be used in nuclear weapons.

By Maureen Lunn | April 22, 2022

Abstracts Aries Opt
Los Alamos, through its ARIES program, is the only place in the United States that can convert plutonium metal into powder. Dennis Duran works with plutonium oxide in a glove box in the Lab’s Plutonium Facility. Los Alamos National Laboratory

In astrology, the Aries zodiac sign—a ram—is associated with strength, bravery, and ambition. A program of the same name at Los Alamos National Laboratory also embodies those characteristics—but in relation to national security.

The purpose of the ARIES (Advanced Recovery and Integrated Extraction System) program is to convert plutonium metal that could be used to make nuclear weapons into plutonium oxide powder. The program supports the Laboratory’s—and the nation’s—nuclear nonproliferation commitments by helping to prevent the spread of weapons-grade nuclear material.

“Not only does weapons-usable plutonium pose a security threat due to proliferation of nuclear weapons, but there are potential environmental, safety, and health consequences if this surplus material is not properly safeguarded and managed,” explains ARIES Program Director Leisa Davenhall.

ARIES dates back to 1998, when the program was mandated by U.S. policy born out of an agreement between United States and Russia. In 2000, each country began working toward the conversion of 34 metric tons of weapons-grade plutonium sourced from Cold War weapons declared no longer necessary for national defense. Despite Russia purportedly suspending the agreement in 2016, the United States has continued its ARIES work in support of its nuclear nonproliferation goals.

Initially, the United States hoped to convert weapons-grade plutonium into fuel for commercial power reactors, but that plan was scrapped when cost estimates skyrocketed. Instead, in 2018, Congress approved a much less expensive “dilute and dispose” plan in which Los Alamos receives surplus nuclear weapon pits (cores) from the Pantex plant near Amarillo, Texas. The pits are disassembled, using a machine called a pit cutter, and the plutonium is placed into a furnace for up to 48 hours. The heat from the furnace turns the plutonium metal into plutonium oxide powder, which is then blended to ensure uniformity.

Next, the plutonium oxide powder is placed in special stainlesssteel cans, which are welded shut for safe interim storage and transport to the Savannah River Site in Aiken, South Carolina. There, it is diluted with other materials and packaged for eventual transport to the Waste Isolation Pilot Plant in Carlsbad, New Mexico, where it will be stored safely and indefinitely in underground salt flats.

“When it comes to producing plutonium oxide, not a lot has changed in the process over the past two decades,” explains Steve McKee, a technical project manager with the ARIES program. “That gives the program a sense of consistency as we continue to inch closer to our goal of 34 metric tons.”

To date, more than a metric ton of weapons-grade plutonium has been safely processed through the ARIES program. In 2022, ARIES program managers hope to produce between 100 and 150 kilograms of oxide. “The process is slow,” McKee says, “but we are making the world safer, one kilogram at a time. ★