Depleted uranium catalyst could cut nuclear waste

Scientists have developed a catalyst based on depleted uranium that could help cut stockpiles of nuclear waste and reduce the burden of its storage.

depleted uranium
Depleted Uranium Hexafluoride Cylinders (Credit: US Department of Energy)

Depleted uranium (DU) is one of the primary by-products of generating nuclear energy, and as one of the oldest nuclear powers, the UK has found itself with a significant nuclear waste problem. Finding non-military uses for depleted uranium has proved difficult, with costs for the resulting storage of the nuclear waste spiralling as its volume grows.

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Researchers from Sussex University, alongside colleagues from Université de Toulouse and Humboldt-Universität zu Berlin, have come up with a solution that could help address the problems associated with DU. They found that an organometallic molecule based on depleted uranium could catalyse the addition of a molecule of hydrogen to the carbon-carbon double bond in ethylene (an alkene) to create ethane (an alkane), which in turn can be used to create a number of useful compounds including ethanol. The work is published in the Journal of the American Chemical Society

"The ability to convert alkenes into alkanes is an important chemical reaction that means we may be able to take simple molecules and upgrade them into valuable commodity chemicals, like hydrogenated oils and petrochemicals which can be used as an energy source,” said Professor Richard Layfield from Sussex University.

"The fact that we can use depleted uranium to do this provides proof that we don't need to be afraid of it as it might actually be very useful for us."

Due to its extremely high density, DU does already have some niche civilian uses, including as counterweights in aircraft and radiography equipment. DU ammunitions have been widely used by the US, UK and Russian militaries, but numerous governments, humanitarian organisations and international bodies have called for a moratorium on their use. A catalyst that uses DU to create commodity chemicals could be an important new outlet for the material.

"The key to the reactivity were two fused pentagonal rings of carbon, known as pentalene, which help the uranium to inject electrons into ethylene and activate it towards addition of hydrogen,” said Sussex’s Professor Geoff Cloke.

"Nobody has thought to use DU in this way before. While converting ethylene into ethane is nothing new, the use or uranium is a key milestone.”