Abstract
In nuclear waste repositories, initially unsaturated buffer is subjected to constant heat emitted by waste canister in conjunction with peripheral hydration through water from host rock. The transient hydration process can be potraied as transformation of initial heterogeneity towards homogeneity as final stage. In this context, this paper addresses the key issue of hydro mechanical behaviour of compacted buffer in context of clay microstructure and its evolution under repository relevant loading paths and material heterogeneity. This paper also introduces a unique column experiment facility available at Ruhr Universitat Bochum, Germany. The facility has been designed as a forerunner of field scale testing program to simulate the transient hydration process of compacted buffer as per German reference disposal concept. The device is unique in terms of having proficiency to capture the transient material response under various possible repository relevant loading paths with higher precision level by monitor the key parameters like temperature, total suction, water content and axial & radial swelling pressure at three different sections along the length of compacted soil sample. In general, a larger spectrum of loading paths/scenarios, which may arise in the nuclear repository, can be covered precisely with existing device.
Highlights
In recent years, considerable research has been carried out to evaluate the behavior of compacted clay based buffer material in the frame of coupled thermo-hydromechanical (THM) processes at nuclear waste repositories
The changes in PSD domains in terms of micro to macroporosity fraction are highly sensitive to the involved physico-chemical processes as a function of applied loading paths and sequences, especially in the frame of couple THM processes at nuclear waste repository
Transient hydration process of compacted buffer material under coupled THM processes at nuclear waste repository indicates the transformation of its initial heterogeneity into homogeneity as final state
Summary
Considerable research has been carried out to evaluate the behavior of compacted clay based buffer material in the frame of coupled thermo-hydromechanical (THM) processes at nuclear waste repositories. In this context, initially unsaturated buffer is subjected to radioactive decay heat emitted by waste canister in conjunction with peripheral hydration through water from host rock. Based on the inputs from phenomenological investigations on microstructure evolution, various dual porosity models have been reported such as volume change behavior due to hydration [3,4,5], coupled THM behaviour in frame of nuclear waste repository [6], water retention behaviour [7]. The facility has been designed as a forerunner of field scale testing program to simulate the transient hydration process of compacted buffer as per German reference disposal concept
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