Turku in Finland was the venue for the 2016 DOPAS conference (Full-Scale Demonstration of Plugs and Seals), which was held from 25th to 27th May 2016. More than 100 participants came together to exchange their experience. The focus was on demonstration experiments for plugging and sealing installations for deep geological repositories.
Nagra was well represented with three presentations: Benoit Garitte’s explanation of the «Full-Scale Emplacement» Experiment (FE Experiment) attracted particular attention. His presentation focused on quality assurance for the backfilling and sealing of an emplacement tunnel in the Mont Terri Rock Laboratory with bentonite and concrete.
«Our measurements show that we can emplace granular bentonite material and concrete as planned and that all requirements are fulfilled», Benoit explained. In his presentation, Hanspeter Weber outlined the work steps that are required to obtain granular bentonite material that meets Nagra’s specific requirements. I spoke about the gas-permeable tunnel seal developed at the Grimsel Test Site.
The information presented on sealing structures from the Äspö Hard Rock Laboratory (S), Onkalo (FI) und Josef (CZ) was also very impressive. To meet the strict requirements relating to compressive strength and tightness, concreted abutments with an optimum contact surface with the rock are required. The two waste management organisations SKB and Posiva have developed excavation techniques that produce smooth rock surfaces with remarkable precision. All contributions can be found on the DOPAS website.
The conference was closed with a visit to the repository for low- and intermediate-level waste (VLJ) on the Olkiluoto peninsula. To reach the disposal cavern, where operational waste from the nearby nuclear power plants is disposed of in silos, we walked down the access ramp that passes through the 1.8 million year old host rock to a depth of 60 metres below the surface.
Many thanks to our Finnish colleagues for their warm hospitality and to Johanna Hansen, R&D coordinator of the Finnish waste managment organisation Posiva, for the super organisation of the conference!
Nagra thanks the EU research programme EURATOM (FP7) for the financial contributions to the DOPAS and LUCOEX projects under Grant Agreements 323273 (DOPAS) and 269905 (LUCOEX).
(Main image: Posiva)