While nuclear energy leaves no carbon footprint, it does leave a legacy of hazardous waste – spent nuclear fuel.
Most countries store it, intending to bury it deep underground, but this is leading to lots of material, with storage times estimated at 300,000 years. However, there are ways to clean up and reuse most of that spent fuel.
“If you start with 500kg of nuclear waste, 480kg of that is uranium and 5kg is plutonium. These can be separated using current technology, refabricated as a mixed oxide fuel and reused.
"This leaves 15kg of waste that now only needs to be stored for 10,000 years. But the difference between 300,000 years and 10,000 years is like throwing an egg off a 30 storey building or a one storey building – the result is the same.”
Within that remaining 15kg of waste is about 450g of very hazardous elements – the minor actinides americium, neptunium and curium. These elements can be used as fuel in new generation nuclear reactors and used up completely.
The remaining waste would only need to be stored for 300 years, which is a timeframe engineers can work with. The problem is separating those actinides from the rest of the waste.
“There are about 4-5kg of different lanthanides in that remaining waste, which are very similar chemically to the minor actinides. But if they were put into the new generation nuclear reactors, they would close the reactor down completely.
"So the problem is how to separate the dangerous actinides from the more abundant lanthanides in this waste – and that's what we've done.”
Laurence and his colleagues have designed a family of molecules that selectively bind to the actinides, pulling them out of the waste with incredible specificity.
While some of the details of how this happens need to be worked out before the industry can consider adopting the technology, it's moving in a direction that could make nuclear power generation a much more amenable and almost non-polluting process for use worldwide.