Sludge experts aim to tackle safe disposal of nuclear waste

Leeds University has formed a Sludge Centre of Expertise aimed at helping nuclear engineers work out how to dispose of nuclear waste safely and efficiently.

The centre has teamed up with Sellafield Ltd to clean up radioactive waste produced by the UK nuclear industry.

Sludge wastes have built up at nuclear power plans such as Sellafield after years of operation and the experts from Leeds will provide the plant’s nuclear engineers with information on the sludge that needs to be removed.

The sludge is largely derived from corroded fuel rod casings and waste from reprocessed fuel. Open-air facilities can also have dust, dirt and debris mixed in the sludge.

The team will attempt to interpret the behaviour of the sludge wastes that have accumulated at the bottom of water-filled waste storage tanks and cooling ponds using remote monitoring techniques that will allow it to sample the sludge from a distance.

Traditionally, video footage of bell jar tests has been used to determine characteristics of a particular material. This involves putting a glass jar at the bottom of a storage tank and sucking up material. Scientists then try to analyse the sedimentation/settling rate of the material from the video recording in order to determine what they are dealing with.

Prof Simon Briggs, director of the school of process, environmental and materials engineering, told The Engineer: ‘We’re now looking at cheap, robust ultrasonic sensors, which work by Doppler shifting. This involves sending out an ultrasound pulse and seeing how particles move and interact with it.

‘Because they’re moving, the scattered sound is Doppler shifted in some way and the amount of Doppler shift tells you the velocity. From this you can infer characteristics of the material in question,’ explained Briggs.

They will also be investigating the best ways to mobilise and transport the waste to specialist treatment plants, where it can be made safe for long-term storage.

Briggs said: ’New technologies will be further developed as a consequence of understanding what the problems are and they will be used on an as-needs basis.’