UKAEA ^{A World Leader in Decommissioning & Waste Management.}

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Project background

As part of our decommissioning strategy at Winfrith, we committed to minimising the amount of low level waste (LLW) despatched from the site, and maximising the amount of material decontaminated before being treated as conventional waste.

In the UK, LLW is routinely compacted and transported for long term disposal at the Drigg facility in Cumbria. Much of the waste produced at Winfrith had only surface contamination, which could be removed to allow the waste to be disposed as exempt or recycled material.

As well as reducing the costs of transporting and disposing LLW, this would be a more environmentally responsible way of managing the waste created from decommissioning.

Key challenges

Our key aim was to maximise the amount of LLW decontaminated and disposed through conventional waste streams. To do this, we needed to establish a waste characterisation process to identify the characteristics and radioactive content of the waste. We also had to establish a protocol for dealing with and managing the wastes, ensuring it complies with the acceptance criteria for either despatch to Drigg or as free release.

Our approach

Initially, the waste is characterised and sorted into parts that can be cleaned and parts that must be treated as LLW.

We then reduce the size of material to be cleaned, using plasma-cutting techniques to make the material a suitable size for waste treatment. It is then passed through the Winfrith Abrasive Cleaning Machine (WACM). The WACM fires iron shot at the contaminated material — removing the surface paint and contamination, leaving behind ‘clean’ metal. It filters the surface contamination and dust into a waste drum, which is then disposed of as LLW.

We then monitor the treated material to confirm that it is free from contamination — storing it until we can prove that all traces of contamination have been removed. Once it is clean, the material can be disposed of as conventional waste and recycled or sold as scrap metal.

The WACM has a dedicated ventilation system and a separate filter system that continually cleans the iron shot fired at the material before it is reused, minimising waste from the treatment process.

The results

We processed the first active material in early 2002, and cleaned over 200 tonnes of material in the first three years of operation. This saved Winfrith some £1 million in sending LLW to Drigg. On average it takes 15 minutes for material to pass through the WACM, and approximately 99% of the process output is clean material for recycling.

The WACM can be operated on a continuous basis, allowing ‘nose to tail throughputs’. Additionally, it not only cleans the waste items but also continuously cleans the blast media — preventing contamination build-up.