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

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Project background

Up to 175,000 cubic metres of solid low level waste (LLW) is expected to arise during the environmental restoration of the Dounreay site. Managing this waste effectively is a key part of the site restoration programme. 

The key focus is the WRACS facility, which x-rays drums of solid LLW, assesses the activity content, compacts them to about a fifth of their size and then loads them into half height ISO containers for storage. 

Key challenges

WRACS was built as a fully-integrated facility for inspecting, supercompacting and loading LLW into containers, ready for future disposal.  The plant was also designed to reduce LLW holdings on the site, and prove that our management of solid LLW meets quality standards and follows best practice.  We had to devise a reliable system that integrates the various stages of waste processing. It also needed to allow treatment of LLW as a ‘quality product’ and limit radiation exposure to operators. 

Our approach

Built to industry standards, WRACS is fitted with specialist handling and monitoring equipment. It uses a standard production-line concept, with full-size drums loaded at one end and the compacted ‘pucks’ offloaded at the other. Each drum has its own unique barcode to allow it to be tracked. The process begins with each drum being loaded onto the system and passed through a barcode reader which registers the drum on the system. It is then on to the first process – the Real Time Radiography x-ray system. This allows operators to view contents within a drum and ensure there are no anomalies. All records of drum images are stored electronically against the drum barcode. 

The drums are then passed through the Segmented Gamma Scanner, to measure the beta gamma-emitting radionuclides and compare them with the consignment paperwork. 

The Alpha Assay System is extremely sensitive and can detect alpha activity, even at very low levels. It is isolated from normal background radiation by 1.8-metre thick concrete walls.  The alpha activity of each drum is measured and compared with the consignment paperwork. 

The penultimate stage of the process is the supercompactor which safely reduces the volume of the drums. The scale of the volume reduction varies, but on average is a 5:1 reduction.  This machine vertically compresses the steel drums with a 2,000-tonne force using a mould to retain the drum in a ‘puck’ shape. Once compacted, the ‘pucks’ are transferred to a half height ISO container via a remotely operated puck grab which allows them to be lifted and then loaded into the container.  Once the container is full, it is sealed and transferred to a monitoring and inspection area before being moved to the interim waste store on the site. 

The SGS and Alpha Assay systems are tested with a calibration drum each working day to ensure that they are operating within their design parameters.

The results

WRACS has become an effective addition to the suite of modern waste management facilities at Dounreay.  The facility is capable of handling over 150 drums a week, and has already processed over 40,000 drums since opening.

WRACS is essential in reducing the volume of solid LLW on site, and operates an effective and efficient system to prepare the waste for long-term management. And thanks to the mechanised production-line process, plant operators are exposed to minimal radiation.