Project seeks three-stage outcome for orphan nuclear wastes

In an EPSRC-funded project, researchers at Strathclyde University are developing a new approach to treating so-called “orphan” nuclear wastes.

Orphan wastes are radioactive wastes that cannot be dealt with in existing processing plants, and for which there is no accepted treatment option.

The researchers, led by Dr Joanna Renshaw, are investigating the potential of a three-stage treatment process, in which the waste is first smouldered to burn the carbon.

This would produce a small volume of stable radioactive ash that can be encapsulated in cement, for example, and then placed in a steel or concrete container for future geological disposal.

The radioactive emissions released during the smouldering process – microscopic particles of radionuclides and carbon dioxide gas containing the radioactive element Carbon 14 - would then be trapped using a similar technology to that used in carbon capture and storage.

Bacteria would be used to stimulate the production of carbonate and phosphate minerals, removing the radioactivity from the gases and capturing it in stable rock form.

To reduce the amount of radioactive material requiring disposal, this mineral formation stage could be carried out as part of the encapsulation process, the researchers hope.

In this way the mineral would be used to encapsulate the radioactive ash, or other waste, before it is placed in a container.

The first stage of the research project will focus on demonstrating the feasibility of capturing the radioactive gases as stable carbonate and phosphate minerals.

The researchers initially plan to demonstrate the feasibility of the technique in treating graphite, which makes up the largest volume of orphan waste.