AUTHIGENIC MINERAL GROWTH AND COPPER CORROSION IN HYDROTHERMAL BENTONITE EXPERIMENTS
The focus of this experimental work is to characterize interaction of bentonite with potential used-fuel waste container materials (i.e. copper). Experiments were performed up to 300°C at 150 – 160 bars for five to six weeks. Bentonite was saturated with a 1,900 ppm K-Ca-Na-Cl-bearing water with Cu-foils. Copper rapidly degrades into chalcocite (CuS2) and minor covellite (CuS) in the presence of H2S. Chalcocite growth and corrosion pit depths were measured for four different experimental runs yielding corrosion rates between 8.8-116 μm/yr depending on duration of experiment, brine composition, and clay type (bentonite vs. Opalinus Clay). Results of this research show that nuclear waste containers act as a substrate for mineral growth in response to corrosion and that Cu clad canisters are a possible engineered barrier system material.