The underground laboratory HADES is the pre-eminent instrument available to the EIG EURIDICE for research into the potential for disposing of highly radioactive and /or long-lived waste in deep clay layers. There, in the heart of the Clay foundation in Boom, numerous experiments are being carried out 225 metres down over an area of 200 metres and these experiments are designed to help answer the question whether deep disposal could offer an effective solution in the long term. The two access shafts with their collection systems and auxiliary buildings are the visual testimony to the underground infrastructure.

Between 1997 and 2007, the underground infrastructure was extended. This work on extending the laboratory is part of the PRACLAY project. The construction of the second access shaft was completed at the end of 1999. The digging of the connecting gallery, over a total length of approximately 80 metres and a depth of 225 metres, was completed on 7 March 2002. This connects the second shaft with the already existing section of the underground laboratory. It was the first time that such an operation was carried out in clay at a depth of 225 metres by means of an industrial technique.

In 2007, the PRACLAY gallery was excavated perpandicular to the connecting gallery, using the same excavation technique. This gallery with a total length of 45 m and a diameter of 1,9 m, will be used during 10 years for the HEATER experiment.