Assessing shallow cracking in copper pipes under various conditions

The corrosion in two ex-service copper pipes removed from the shutdown National Research Universal (NRU) reactor after 40 years of irradiation was investigated, focusing on localized corrosion. One pipe was exposed to humid air with a temperature of around 40 °C and a gamma radiation dose rate of 0.015 Gy/h, while the other sample was remote from the reactor and almost non-irradiated. Nanoscale analysis revealed shallow cracking and nitrogen at the crack tips of both the irradiated and non-irradiated cross-sections. However, the low-dose irradiation caused propagation of the pre-existing cracks observed in all Cu piping and did not initiate these defects. This research shows that stress corrosion cracking is unlikely to be enhanced in a defect-free electrodeposited copper under low-dose irradiation, similar to that expected for used fuel containers in Canada, in a deep geological repository.