The National Nuclear Security Administration on Monday formalized a decision to immobilize some 350 kilograms of plutonium used in a Japanese research facility into glass-like cylinders at the Savannah River Site rather than sending the material to the Waste Isolation Pilot Plant.
The semiautonomous Department of Energy nuclear weapons agency put the official stamp on the policy Monday in an amended record of decision published in the Federal Register.
The 350 kilograms of plutonium was used as fuel in Japan’s Fast Critical Assembly. The last of that material was shipped to the Savannah River Site from Japan in 2016 and was originally part of a 6 metric-ton surplus tranche that the National Nuclear Security Administration (NNSA) said that same year would be mixed with concrete like grout at Savannah River and buried deep underground at the Waste Isolation Pilot Plant (WIPP) near Carlsbad, N.M., as part of what is now known as the Surplus Plutonium Disposition Program, or dilute and dispose.
Unlike the rest of the six metric tons of surplus, most of the Fast Critical Assembly fuel is encased in steel cladding that would have to be removed before the plutonium inside could be converted into an oxide that WIPP can accept.
That process, it turns out, is too expensive for NNSA’s taste, leading the agency to instead designate the fuel assemblies for dissolution in Savannah River Site’s H-Canyon Processing Facility, after which they’ll be turned into glasslike cylinders at the site’s Defense Waste Processing Facility — essentially the same thing that happens to liquid waste leftover at the South Carolina site from Cold War-era plutonium production.
“Because of the high cost to install and operate a decladding and oxide conversion process, NNSA initiated an evaluation of alternative processing technologies,” the agency wrote Monday in the Federal Register. “Based on these feasibility and process technology studies, NNSA determined that electrolytic dissolution could be performed at [Savannah River Site] at a substantially lower cost than the mechanical decladding and oxidation process.”
Once Savannah River Site turns the Fast Critical Assembly fuel into glass, the NNSA will store the resulting cylinders on site until the U.S. builds a geological repository such as the perennially unbuilt Yucca Mountain in Nye County, Nev., which the Joe Biden administration has said it will not to build.
