Recovering fuel from waste

The nation's permanent nuclear waste repository could be used more efficiently than currently planned, according to ORNL's Emory Collins. He and his colleagues believe it makes sense for the repository to take mainly nuclear fission products, or 5% of the wastes, and turn away the bulk of the waste--spent nuclear fuel. The usable uranium and plutonium in this material could be extracted, chemically treated, and recycled as mixed-oxide (MOX) fuel for nuclear reactors.

When the $60-billion repository at Yucca Mountain, Nevada, begins accepting shipments of waste in 2010, it may fill up soon after it opens for business. By then the Secretary of Energy may have convinced Congress that a new repository is needed or that the current one should be expanded. Collins and his colleagues believe that building an advanced commercial nuclear fuel reprocessing and recycling plant, including a MOX fuel fabrication facility, could extend the life of the repository. "It could receive wastes for hundreds of years rather than fill up when it opens," Collins says.

Here's the vision of Collins, Charles Forsberg, Dennis Benker, Kevin Felker, G. D. "Bill" DelCul, Barry Spencer, Ron Canon, and David Williams, all of ORNL's Nuclear Science and Technology Division, and personnel at four other national laboratories performing research for the Advanced Fuel Cycle Initiative of the Department of Energy's Office of Nuclear Energy.

A 2000-ton-per year commercial reprocessing and recycling plant, including a MOX fuel fabrication facility, is designed, built, and operated. The spent fuel that has cooled for as long as 40 years at power plant sites is transported in government-approved casks to the safeguarded plant. Using the UREX process, the uranium in the spent fuel is separated from radioactive fission products and heat-emitting isotopes of cesium and strontium. The liberated isotopes are shipped in special packages to the waste repository.

At the plant, plutonium and neptunium are separated from the uranium and fission products using an ORNL-developed process that makes neptunium stay with the plutonium, so it cannot easily be diverted for use in a nuclear weapon. The neptunium has a decay daughter, protactinium-233, which emits an easily detected gamma ray that could signal that stolen plutonium is about to be smuggled past plant portals and entrances.

"We showed that a plutonium-neptunium product can be recovered in high yield from light-water-reactor spent fuel," Collins says. "We demonstrated that this product is sufficiently purified of fission products and can be made into MOX fuel for use in a fast reactor or a current commercial power reactor."

The envisioned plant could also make reactor control rods containing "burnable poisons" like americium-241, from long-cooled nuclear waste. When americium-241 absorbs reactor neutrons, it forms plutonium-238, which can be used in MOX fuel.