SEALEX in-situ experiments-performance tests of repository seals: experimental observations and modelling

Institute for Radiation Protection and Nuclear safety (IRSN), France

^a Corresponding author: nadia.mokni@irsn.fr

Abstract

The paper describes observations and numerical analysis of SEALEX performance tests installed in Tournemire Underground Research Laboratory (URL). One of the objectives of the large scale in-situ tests is to investigate the impact of technological gaps on the long term performance of bentonite based seals. The swelling cores consist of pre-compacted blocks of a natural sodic Wyoming bentonite (MX80 type) mixed with quartz sand in a ratio of 70/30 (in dry mass) with different geometries (monolithic disks or four jointed disks). Several technological gaps exist within the in situ tests: Gaps between the blocks and annular gap with variable width between the bentonite-based core and the host rock. All the tests are extensively instrumented for monitoring the main Hydro-Mechanical (HM) variables. Comparison of the experimental results showed that the presence of technological gaps constituted new hydration sources (annular gaps) and flow paths (gaps between the blocks) that changed the saturation kinetics. A coupled HM formulation that incorporates the relevant processes involved in the problem under consideration has been adopted to analyse the effect of the annular technological gap on dry density homogenization of the bentonite based core as hydration progresses. Technological gaps were demonstrated to have an impact on dry density distribution.