Pump-placed stowing with saline concrete provides reinforcement at the Morsleben nuclear-waste repository

Twenty-four former rock-salt chambers at the Morsleben nuclear-waste repository have now been reinforced with saline concrete using the thick-slurry pump-placed stowing technique in order to prevent the risk for mining collapse. This filling operation, which is being carried out in the central part of the repository at depths of between 370 and 460 m, commenced in 2003. The saline concrete is delivered from a surface pumping installation to the placement point via a 1,600 metre-long pipeline. Initial teething problems, which mainly affected pumping performance and involved the escape of excess concrete solution from the stowing cavities into the mine workings, have now been overcome. The pump-stowing system is at present achieving an average delivery rate of over 11,000 m3/month and escapes of concrete solution have practically stopped. A total of 490,000 m3 of cavity space had been filled by September 2007. It is expected that the stowing operation in the central section will be completed in early 2010. This part of the mine will then have attained the long-term stability rating required for the Morsleben decommissioning and filling operation to be sanctioned in accordance with the planning approval arrangements laid down under the Nuclear Licensing Procedural Ordinance. (orig.)