nuclear milestone
Photo of a tray of plutonium-238 pellets at Oak Ridge National Laboratory.
Oak Ridge National Lab developed an automated metrology system for production of Pu-238 pellets.

The Department of Energy (DOE) recently shipped 0.5 kilograms of heat source plutonium oxide from Oak Ridge National Laboratory (ORNL) to Los Alamos National Laboratory.

This is the largest shipment of new heat source plutonium oxide since DOE restarted domestic plutonium-238 production over a decade ago and strengthens the nation’s supply chain needed to support future NASA deep space missions that rely on radioisotope power systems, such as the upcoming Dragonfly mission.

Packing up Plutonium

DOE hit a milestone in June in its capacity to package and transport plutonium-238, a key ingredient in radioisotope power systems used in deep space missions from Voyager to the Mars Perseverance rover.

This delivery of heat source plutonium oxide was an order of magnitude greater than previous shipments. It was completed in partnership with NASA, who sponsored the installation of equipment to expand ORNL’s packaging capability.

With this delivery, DOE remains on track to meet its average production target of 1.5 kilograms per year of heat source plutonium oxide by 2026.
“Bringing this packaging capability online at Oak Ridge National Laboratory demonstrates the Department’s commitment to our partnership with NASA,” said Dr. Kathryn Huff, Assistant Secretary for Nuclear Energy. “Together, we are working to ensure that a viable end-to-end capability to produce radioisotope power systems for deep space use exists within the U.S. for decades to come.”

Restoring the U.S. Supply Chain

With the closure of the K-reactor at Savannah River Site in the late 1980s, the United States lost its ability to produce plutonium-238 for space exploration.

Over a decade ago, NASA and DOE agreed to re-establish a robust domestic supply chain of plutonium-238 to ensure a reliable source of fuel for future missions.
Creating the fuel for NASA spacecraft is a complex process. DOE uses the High Flux Isotope Reactor at ORNL and the Advanced Test Reactor at Idaho National Laboratory to produce plutonium-238 by irradiating targets in both reactors.

The targets are processed into heat source plutonium oxide at ORNL, which is then shipped to Los Alamos National Laboratory to be manufactured into fuel clads. From there, the fuel clads are sent to Idaho National Laboratory, where the fuel is loaded, tested, and shipped to NASA’s Kennedy Space Center in Florida for launch.

To Titan, and Beyond

The heat source plutonium oxide will support NASA deep space missions such as Dragonfly, which will send a robotic rotorcraft to explore Saturn’s moon Titan in the coming years. Dragonfly will be powered by a radioisotope power system called a Multi-Mission Radioisotope Thermoelectric Generator, or MMRTG.

Radioisotope power systems convert heat generated by the natural radioactive decay of plutonium-238 into electrical power. These systems have powered more than two dozen U.S. space missions and are capable of producing heat and electricity under the harsh conditions in deep space for decades without any maintenance.

The first NASA mission to use new plutonium-238 produced by DOE was NASA’s Perseverance rover, which landed on Mars in 2021 and continues to explore the surface of the planet today.

DOE and the national labs will continue to scale up heat source plutonium oxide production efforts to meet NASA’s deep space exploration missions for the coming decades.