The power to reduce nuclear waste worldwide

Nuclear waste

Our process for reducing the volume of nuclear waste will make its storage safer and more cost effective.

Researchers from our University's Faculty of Engineering have shown that mixing plutonium-contaminated waste with blast furnace slag and turning it into glass reduces its volume by 85-95 per cent. The process also effectively locks in the radioactive plutonium, creating a stable end product.

The research, funded by Sellafield Ltd and the Engineering and Physical Sciences Research Council, could also be applicable in treating wastes generated during the eventual clean-up of the damaged Fukushima plant in Japan.

"The overall volume of plutonium- contaminated wastes from operations and decommissioning in the UK could be upwards of 31,000 m3, enough to fill the clock tower of Big Ben seven times over," said lead researcher, Professor Neil Hyatt from the Department of Materials Science and Engineering.

"Our process would reduce this waste volume to fit neatly within the confines of just one Big Ben tower,” he added.

The current treatment method for non-compactable plutonium- contaminated wastes involves cement encapsulation, a process which typically increases the overall volume.

Professor Hyatt said: "If we can reduce the volume of waste that eventually needs to be stored and buried underground, we can reduce the costs considerably. At the same time, our process can stabilise the plutonium in a more corrosion- resistant material, so this should improve the safety case and public acceptability of geological disposal."

Although the ultimate aim for higher activity wastes is geological disposal, no disposal sites have yet been agreed in the UK.

Using cerium as a substitute for plutonium, the Sheffield team mixed representative plutonium contaminated wastes with blast furnace slag, a commonly available by-product from steel production, and heated them to turn the material into glass, a process known as vitrification.

"Cerium is known to behave in similar ways to plutonium so provides a good, but safe, way to develop techniques like this," Professor Hyatt said.

He added: "Our method produces a robust and stable final product, because the thermal treatment destroys all plastics and organic material. This is an advantage because it is difficult to predict with certainty how the degradation of plastic and organic materials affects the movement of plutonium underground."

Professor Hyatt is now working on optimising the process to support full-scale demonstration and plans future investigation of small scale plutonium experiments.