The underground research laboratory (URL) HADES in Mol, including the PRACLAY expansion, is the most important facility in Belgium for the in-situ testing of deep geological disposal concepts for radioactive waste. The PRACLAY gallery is an addition to the HADES facility in the Boom Clay and is located at a depth of 224 meters. Construction of the URL began with the sinking of the first access shaft from 1980 to 1982. PRACLAY is currently operated by the Economic Interest Grouping EURIDICE.
To sink the first access shaft through the water-bearing sands of the overburden a sub-ground freezing technique was used. The freezing led to an unexpectedly strong swelling of the clay and thus to high stresses in the host rock. These stresses, in turn, resulted in pronounced creeping and loosening of the clay during the excavation of the shaft station and the subsequent research gallery.
After more than 30 years of continuous and reliable operation the Shaft 1 hoisting system needs refurbishment to ensure continued safe operation in compliance with Belgian regulations. The original hoisting system had been constructed in part and in line with the relatively low hoisting demands associated with a URL from refurbished equipment. As a result of the previously mentioned mechanical stresses related to the original shaft construction technique the geometry of the shaft has not remained ideally straight, introducing challenges to the refurbishment. EURIDICE commissioned DBE TECHNOLOGY GmbH to develop a concept for the refurbishment of the hoisting system. In response DBE TECHNOLOGY developed a refurbishment concept that includes two alternatives for the surface installations of the hoisting system and three design variants for the shaft internals. In its report to EURIDICE, DBE TECHNOLOGY GmbH compared the options in view of their economical, technical and operational feasibility to support EURIDICE's decisions related to the realisation of the shaft and hoisting system's refurbishment.