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Engineering Studies and Demonstrations of Repository Designs (ESDRED)

Exploitable results

The two main project participants were able to design, fabricate and demonstrate two sets of equipment needed for the transfer and emplacement of waste canisters weighing respectively 2 and 5.2 tonnes. The two sets of equipment were designed for respective emplacement in horizontal and vertical disposal boreholes with very small annular clearances between the canister and the wall of the disposal boreholes. A desk study was also produced by a third participant to assess the two respective emplacement designs as far as reversibility is concerned. Both emplacement systems were demonstrated in surface facilities using inert waste canisters that were otherwise accurate geometrically and with regard to mass. The horizontal emplacement equipment which was produced can be seen by the public at ANDRA's Technology Centre (ETe) in Saudron, near the Bure URL. The vertical emplacement system produced by DBE-TEC is not on display at the time.
Part of the program consisted first of designing low pH cement formulations and then of preparing several low pH concrete designs suitable for the shotcreting of sealing plugs and for rock support. In both cases shotcreting was used as the reference construction technology. A short plug and a long plug were subsequently constructed in situ underground in two different URL's. The short plug was loaded to failure (i.e. slippage) very quickly and monitored during the entire process. The full scale longer plug was loaded using the swelling pressure created by bentonite blocks which were artificially hydrated, which is a much slower loading process more closely related to what would happen in reality. At time of writing the full scale long plug had not been loaded to failure. Final results will be reported as part of the MoDeRn project which is also being financed by the EC as part of the Seventh Euratom Framework Programme for Nuclear Research and Training. A variety of project reports, describe in detail the process used to develop low pH cements which would meet the project needs. Other reports describe the test plan and the execution related to the construction of the two plugs noted above. The Grimsel testsSite where the long plug is tested and monitored is managed by NAGRA and can be visited at any time by making appropriate arrangements in advance. This long plug has also been employed for a further programme of cross-hole seismic tomography and other types of wireless monitoring (TEM Project) organized by Esdred partners outside of the Esdred programme. It is also a part of the MoDeRn monitoring project.
The Esdred project also focused on training and communication. The project participants wrote articles, presented technical papers at international conferences, held workshops, developed and presented university lectures, and organized some international events in Prague (Czech Republic), in Bure (France), in Landesbergen (Germany), etc. The Esdred partners developed and then presented 17 Masters level lectures to the students of the University Polytehnica of Bucharest, Romania. They also organized two workshops focusing on the R&D related to low pH cements, which attracted an international audience and authors. The "International Technical Conference on Practical Aspects of Deep Radioactive Waste Disposal" (June/08) was organized by Esdred together with the Czech Technical University of Prague (CTU) and RAWRA the Czech national waste management agency and was held in the facilities of the CTU. Nineteen of the thirty seven papers and posters related directly to Esdred, to the national agencies represented in Esdred or to the contractors that had been engaged by the Esdred participants. The results were immensely appreciated by the more than 120 participants hailing from 19 different countries. The proceedings have been posted on the Esdred website and bear the following ISBN # 2-916162-05-4. In October 2008 all of the Esdred Module Leaders made important presentations at the EC's Euradwaste Conference in Luxembourg and during the field trip to Bure which included a demonstration of some of the equipment produced as part of the project. There was also a separate trip and visit for journalists in Bure. Most of the material prepared by the Esdred partners for the public has been placed on the Esdred web site. This includes technical papers, presentations to various groups, posters, videos, annual activity reports, summaries of the proceedings from two Low pH Workshops and the Proceedings from the International Conference held in Prague. The Esdred website address is: www.esdred.info
One project participant was able to successfully design the necessary formulation and thereafter produce 4 tonne 2.3 m OD bentonite rings to be used as an engineered barrier. Other participants demonstrated their capacity to backfill the annular gap between a waste canister and the disposal drift wall using a variety of wet and dry products. The evolution over time and the performance of bentonite based seals, particularly in relation to relative water-gas permeability, was also assessed and is in fact on-going beyond ESDRED. Finally non- intrusive monitoring techniques based on crosshole seismic tomography were also developed and demonstrated. This work is also continuing beyond ESDRED. The various reports produced, most of which are available to the public, will help interested parties: - to design a sand/bentonite mixture which, when compressed into a ring, has petro-chemical characteristics suitable for use as an engineered barrier around waste canisters; - to design a method suitable for placing granular bentonite around waste canisters as a buffer material while obtaining the desired in situ density and other characteristics; - to design and fabricate a mould for producing large EBS rings as well as all the related stripping and handling equipment; - to formulate various wet and dry materials for use as a backfill and to evaluate the related placement options; - to formulate a borehole seal made of moderately compacted sand/bentonite mixtures and to have an understanding of the gas/water permeability of such a seal over time; - to evaluate whether non-intrusive monitoring based on cross-hole seismic tomography is suitable to a particular application and to understand the scope and limits of the technique.
The two participants in this program each successfully produced a machine for emplacing 43 - 45 tonnes waste canisters in horizontal disposal drifts while maintaining a very small annular gap between the canister and the walls of the drift. One machine was based on water cushion technology while the other used air cushions. The latter machine was subsequently modified to demonstrate the emplacement of packages of 4 pre-assembled bentonite rings produced in Module 1, weighing 17 tonnes per package. The air cushion machine is on public display at ANDRA's Technology Centre in Saudron, near the Bure URL in France. At time of writing the water cushion machine is set up underground on the -220 m level at the Äspö URL in Sweden. Design details, test results, as well as recommendations for future enhancements are available in the various project reports which have been designated for public access.

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