Over 75% of nuclear waste produced in the UK is classified as intermediate level waste (ILW) – this is currently encapsulated in specially formulated cement through a mixing process and sealed in steel drums, in preparation for disposal deep underground.

However researchers at the University of Sheffield have shown that turning this kind of waste into glass through a process called vitrification could prove a better method for its long-term storage, transport and eventual disposal.

The technology is already used for storing more toxic high level nuclear waste to reduce both the reactivity and the volume of the waste produced.

Until now, this method has not been considered suitable for ILW because the technology hadn’t been developed to handle large quantities of waste composed from a variety of different materials.

The research programme tested simulated radioactive waste materials – those with the same chemical and physical makeup, but with non-radioactive isotopes – to produce glass and assess its suitability for storing lower grades of nuclear waste.

A key discovery made by the Sheffield team was that the glasses produced for ILW proved to be very resistant to damage by energetic gamma rays, produced from the decay of radioactive materials.

Professor Neil Hyatt who led the work said: “We found that gamma irradiation produced no change in the physical properties of these glasses, and no evidence that the residual radiation caused defects.

“We think this is due to the presence of iron in the glass, which helps heal any defects so they cannot damage the material.”

According to Hyatt, vitrification could offer improved safety and effectiveness for large volumes of nuclear waste that need to be stored securely prior to disposal.

Maxine Perella

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