ORNL has developed an automated metrology system to produce Pu-238 pellets. (Photo: ORNL)
The Department of Energy recently shipped half a kilogram of plutonium oxide pellets from Oak Ridge National Laboratory to Los Alamos National Laboratory, the agency announced July 18, marking the largest such shipment since the DOE restarted domestic plutonium-238 production over a decade ago.
The successful June packaging and delivery represented a milestone, according to the DOE, because it was an order of magnitude greater than previous shipments. NASA needs plutonium oxide pellets to fuel radioisotope thermoelectric generators (RTGs) for deep space missions, and the space agency worked with the DOE to sponsor the installation of equipment to expand ORNL’s packaging capability.
“Bringing this packaging capability online at Oak Ridge National Laboratory demonstrates the Department’s commitment to our partnership with NASA,” said 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.”
The why: RTGs work by converting heat from the radioactive decay of Pu-238 into electricity, and they have powered deep space missions for decades. (The twin Voyager spacecraft, launched in 1977, are still getting power from their RTGs today.)
With the closure of the K-reactor at Savannah River Site in the late 1980s, the United States lost its ability to produce Pu-238 for space exploration, according to the DOE. But over a decade ago, NASA and the DOE agreed to reestablish a domestic supply chain of the isotope to power future space missions. The first NASA mission to use new Pu-238 produced by the DOE was NASA’s Perseverance rover, which landed on Mars in 2021 and is still exploring the planet today. NASA’s upcoming Dragonfly mission will send a robotic rotorcraft to explore Saturn’s moon Titan, powered by a radioisotope power system that NASA and the DOE call a multimission radioisotope thermoelectric generator (MMRTG).
Production and delivery: Today, Pu-238 is produced by irradiating targets in the High Flux Isotope Reactor at ORNL and the Advanced Test Reactor at Idaho National Laboratory. The targets are processed into plutonium oxide at ORNL, which is then shipped to LANL to be manufactured into fuel clads. The fuel clads are then sent to INL, where the fuel is loaded, tested, and ultimately shipped to NASA’s Kennedy Space Center in Florida for launch.
The DOE reports that it is on track to meet its average production target of 1.5 kilograms of plutonium oxide per year by 2026.
