Engineered Barrier Emplacement Experiments in Opalinus Clay: “EB” Experiment. As-built of dismantling operation. PEBS Deliverable D2.1-4.

Abstract

The Engineered Barrier Emplacement Experiment in Opalinus Clay “EB” Experiment aimed the demonstration of a new concept for the construction of HLW repositories in horizontal drifts, in competent clay formations. The principle of the new construction method was based on the combined use of a lower bed made of compacted bentonite blocks, and an upper buffer made of granular bentonite material (GBM). The project consisted on a real scale isothermal simulation of this construction method in the Opalinus Clay formation at the Mont Terri underground laboratory in Switzerland. A steel dummy canister, with the same dimensions and weight as the Spanish reference canister, was placed on top of a bed of bentonite blocks, and then the upper part of the drift was buffered with the GBM made of bentonite pellets (Figure 1). The drift was sealed with a concrete plug having a concrete retaining wall between the plug and the GBM. Since the end of the test installation the evolution of the different hydro-mechanical parameters were being monitored, both in the barrier and the rock (especially in the EDZ). Relative humidity and temperature in the rock and in the bentonite buffer, rock displacement, pore pressure and total pressure were registered by means of different types of sensors. Due to the short amount of free water available in this formation, an artificial hydration system was installed to accelerate the hydration process in the bentonite.This document describes the dismantling and sampling activities carried out. It also shows the results of the dry density and water content obtained in the on site analyses carried out by AITEMIN and in the laboratory ones by the CIEMAT team. In section 2, it starts with a brief chronological description of all the activities that have been carried to accomplish the whole operation. Section 3 describes the dismantling of the concrete plug, the retaining wall and the bentonite removal including the methodology applied and the resources and tools that were used. It also explains the operation to support the canister and to dismantle the data acquisition system. Section 4 is completely dedicated to the sampling and analysis operation. It describes the different sampling procedures applied depending on the different materials to be sampled, the samples that were taken for the analyses on site and the ones that were taken for the partner organizations. It also explains the analysis procedures carried out in the on-site laboratory, and the obtained results. The document finishes with the conclusions and the used references.