Hydrogen-induced cracking of carbon steel

Carbon steel may be susceptible to hydrogen-induced cracking (Kobayashi et al., 2011). Hydrogen is likely to be produced by radiolysis of groundwater and by water reduction during the corrosion process in reducing conditions. Figure 7.6 shows reduction in area versus applied potential in constant extension rate testing (CERT) for ASTM A216-Grade WCA steel in con­centrated synthetic groundwater at 80°C (176°F) (Ahn and Soo, 1995). This hydrogen-induced cracking can be regarded as a variation of SCC. Recently, the surface opening area resulting from SCC container damage has been assessed for various candidate container metals including carbon steel. Generally, the maximum opening area is approximately 0.1% of the total surface area of the waste package (Gwo et al., 2011). This original

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7.6 Reduction in area versus applied potential in constant extension rate testing (CERT) for ASTM A216-Grade WCA steel in concentrated synthetic groundwater at 80°C (Ahn and Soo, 1995). SCE: standard calomel electrode. Used with permission from Elsevier.

assessment was made with impact stress in the deformed area of the con­tainer as an effect of seismic impact. However, this assessment may be applicable to the normal static case too. The weld residual stress and a weld area can be used instead of impact stress and deformed area from seismicity. The models for estimating opening area due to SCC are described in the following section for stainless steel canisters. This approach is equally appli­cable to the hydrogen-induced cracking of carbon steel.

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