Two patches of near-neutral-pH stress corrosion cracks (SCC), as developed on a pipeline steel during service, have been characterized. The two patches can be characterized as containing either dense cracks or sparse cracks, based on their spatial separation. Cracks from both patches were categorized as either linked cracks or independent cracks; the former were distinguished by multiple peaks in the depth direction, considered to be a result of crack coalescence, while the latter had a single peak and a smooth depth profile. The linked cracks were usually <500 μm in depth with little increase in depth as the crack length extended beyond ~2 mm. In contrast, the independent cracks exhibited a linear relationship between crack length and crack depth. The linked cracks, although dormant in the depth direction, appeared to be actively corroding in the width direction near the crack root and possibly at the overlapped region between two joined cracks. For the independent cracks, corrosion in the width direction became faster as the crack deepened, implying that the growing cracks were evolving toward a pit. This also suggests that alternative mechanisms (e.g., possibly hydrogen embrittlement, as evidenced in this study) must become operative in the process of rupture following the initial dissolution mechanism for crack initiation and initial growth.

A wide range of alloys have been considered as candidate container materials for the storage and disposal of nuclear waste. The goal of the majority of national nuclear waste management programs is the ultimate disposal of the waste, although, depending upon the strategy being followed, disposal may come only after an extended period of storage. The management strategy depends on the nature of the waste, with intermediate level waste (ILW) generally being stored for a longer period before disposal than is the case for higher activity wastes, such as high-level waste (HLW) from reprocessing activities or spent fuel (SF). This review describes the corrosion issues associated with the storage and disposal of both ILW and HLW/SF. Various factors enter into the decision of which material to select for the container, of which the corrosion behavior in the expected service environment is only one. The corrosion behavior of the container material(s) is closely tied to the nature of the environment to which the containers will be exposed and how that environment changes with time. A general discussion of the corrosion behavior of the materials selected or proposed as container materials is provided, and the specific corrosion issues associated with each class of material highlighted. The classes of material considered for the storage and/or disposal of ILW and HLW/SF include copper, carbon steel and cast iron, stainless steels, titanium alloys, and nickel-based alloys.

The mechanism and kinetics of Cu corrosion in anoxic aqueous chloride solutions containing sulfide (10−3 mol/L) have been investigated electrochemically and under natural corrosion conditions. Under these conditions Cu is thermodynamically unstable in anoxic water, and the anodic growth of a chalcocite (Cu2S)/digenite (Cu1.8S) film is supported by the cathodic reduction of water. Electrochemical experiments at rotating disc electrodes and impedance spectroscopy show that the film growth occurs under SH− transport control as stagnant conditions are approached. At this concentration, film growth can follow two distinct pathways. The initially formed film grows rapidly via an ion (or associated defect) transport process. If this film remains coherent, subsequent film growth/corrosion is extremely slow. If the development of interfacial stresses leads to film fracture, then growth continues and a much thicker nodular deposit is formed. The primary goal of this research is to develop a mixed potential model, which can be used to assess the performance of copper nuclear waste containers in granitic nuclear waste repositories.