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The PRACLAY experiment. Exchange meeting n°1: EIG PRACLAY - SCK•CEN - ONDRAF/NIRAS 18/01/01. The objectives of the PRACLAY experiment have been revised. Revision of the objectives (April 2000) Report ‘Methodical and detailed description of the PRACLAY Experiment’ Revision of the design
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The PRACLAY experiment Exchange meeting n°1: EIG PRACLAY - SCK•CEN - ONDRAF/NIRAS 18/01/01
The objectives of the PRACLAY experiment have been revised • Revision of the objectives (April 2000) • Report ‘Methodical and detailed description of the PRACLAYExperiment’ • Revision of the design • longitudinal design (plugs, central tube, ...) • hydration system • thermal load • instrumentation • proposal of additional experiments
The PRACLAY experiment • in-situ verification and confirmation of the present status of scientific and conceptual knowledge; • better understanding of • the disposal system; • the interactions between its different components.
Differences exist with the real disposal concept • Geometry • Influence of the boundary conditions • Thermal load • Hydration process • Instrumentation • The PRACLAY experiment will not reflect exactly the real concept but will give the tools to understand it with a good confidence level
Instrumentation is installed to observe the behaviour of the different components • Instrumentation has to be optimised so that as much meaningful information as possible can be collected from each sensor; • Instrumentation has to be redundant to guarantee that a sufficient fraction will resist at long term; • External devices (instruments, samples, ...) may never alter the demonstration character of the PRACLAY experiment.
Confirm and improve our knowledge of the reference concept • Comparison between • Prediction based on our interpretation of the reality (models) • What we can measure • Agreement=> a certain prediction level is reached=> confirmation of our knowledge • Difference=> some aspects are misunderstood=> improvements are required
The desired output is (1): • Observation of the behaviour of the whole disposal system: • interactions with the main gallery • plugs • central tube (possibility of retrievability) • Characterisation of the disturbed zone (EDZ and TDZ) and its evolution in time • verification of the hypothesis considered in the performance assessment
The desired output is (2): • Verify the hydration process through the backfill material • useful information for the work sequence of the final repository • Study of the THM phenomena occurring inside the backfill material and the possible Geochemical coupling • heat and water transport process • swelling capacity of the backfill
The desired output is (3): • The study of the Geo-Chemistry phenomena • Microbial characterisation • Saline fronts • concentration of chloride • problems of pitting corrosion • Alkaline plume • decrease of the swelling properties • hardening by precipitation of calcium carbonate • Oxydation of Boom clay • Thermal degradation
Additional experiment proposals • Corrosion - Bruno Kursten • Migration - Pierre De Cannière
Localised corrosion of candidate overpack materials on a 1:1 scale • Ring shaped elements • around the central tube - isolated electrically • makes part of the central tube (welding) • Contact with bentonite - Mock-up 1000mg/L Cl- • Characterisation of the chemical composition of the backfill pore-water (anion content, pH, temp., oxygen content, …) • Determination of the corrosion potential Ecorr under realistic conditions
Migration experiment (1) • Radial piezometers outside the middle of the PRACLAY experiment • Aim: • general characterization of the transport properties of the backfill at large scale and under in situ conditions; • models validation; • detection of preferential water paths in the backfill.
Migration experiment (2) • Migration experiment on backfill and Boom Clay samples after a thermal loading (in lab) • In situ migration experiments in Boom Clay after dismantling of the PRACLAY experiment
Current choices forthe PRACLAY experiment • Thermal load: ~240 W/m • 100 °C after 5 years of heating • 30 °C after 1 year of cooling • Lining designed to resist to the mechanical and the thermal load • Backfill material: the same as form OPHELIE • Swelling pressure limit to 2 MPa • Radial hydration from outer