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

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Project background

Liquid waste, known as raffinate, from the Prototype Fast Reactor contains almost half the radioactive waste hazard at the Dounreay site. Originally classified as high level waste, we made the case for the raffinate to be reclassified as an intermediate level waste (ILW) in 2004 as it no longer required active cooling. On this basis, it could be treated as ILW. This would allow the raffinate to be immobilised in cement – lowering environmental risks and reducing the radioactive hazard earlier than planned, resulting in large cost savings.

Key challenges

Following extensive stakeholder consultation, it was decided that the best practicable environmental option was to immobilise the raffinate in cement and package it as ILW. We would have to ensure that this new process for treating the material met strict technical criteria for disposal, by preparing a Letter of Compliance submission for Nirex.

Our approach

We developed a bespoke neutralisation process to enable immobilisation of PFR raffinate in cement. In addition, we reassessed and modified the design of the waste package (a 500 litre drum) to maximise the amount of liquor that could be added to each drum. We ran trials to test our modifications and the results to date have proved positive, including the full scale encapsulation of a PFR raffinate simulant.

All this required us to develop a chemically representative stimulant of PFR raffinate on which to base process and package designs. Furthermore we prepared a letter of Compliance submission for this waste packaging strategy for assessment by Nirex to ensure that strict technical criteria for disposal were being met.

The results

In August 2005, we received a conceptual Letter of Compliance. An interim stage Letter of Compliance submission has been made, and has been received from Nirex.