Analysis of shear mock-up tests in a canister-clay system for spent nuclear fuel isolation

Abstract

The aim of this paper is to simulate a canister-buffer mock-up test using the finite element computer code CODE_BRIGHT. The response of a copper canister put inside clay barriers that undergo hydration and swelling till complete saturation was investigated. Although the copper is very stiff and resistant and will be emplaced in a clay volume, shear deformations occurring in the clay barrier may have an impact on the canister. A Mock-up test was carried out in a steel cell at a scale of about 1:10 for assessing the consequences of a shear zone for a copper rod that was surrounded by compacted bentonite as a clay barrier. The challenge problem is to perform the simulation of the mock-up tests under the different shear rates that was carried out by Borgesson (1968). The results might contribute to a better understanding of the real shearing response of the system and validate the constitutive models used for the simulations.For this purpose, the mock-up test was simulated with CODE_BRIGHT in hydro-mechanical couplings in three dimensions. For the model validation, the results of the simulations were compared with the test measurements. The constitutive model used for the copper simulation was a viscoplastic model developed by Bodner and Partom. For the bentonite simulation, a viscoplastic model for unsaturated soils based on the Desai and Perzyna theory, using an elliptical yield surface corresponding to the modified Cam-Clay model, was used.