Published online by Cambridge University Press: 10 February 2011
Stress corrosion crack growth in pure copper has been studied with the aim of determining data which may be used in extrapolations to conditions of interest for use of copper as a canister material for long term storage of spent nuclear fuel. The canister should retain its integrity for a time of 100 000 years and the ultimate aim of the project is to show that stress corrosion cracking is not a threat to the canister integrity. The crack growth is studied as a function of applied stress intensity factor and environmental factors such as solute concentration and electrochemical potential. The approach used is to determine crack growth rates under conditions which give low but measurable rates which can then be extrapolated to times and conditions of relevance to canister integrity. The most accurate method of on-line crack growth monitoring, DC potential drop, is unfortunately in conflict with the low resistivity of copper. The results so far indicate that there is a stres.intensity threshold for SCC growth in copper which is not appreciably lower than 30 MPa√m. Additional data are needed to improve the credibility of the threshold value. It is also proposed that crack growth experiments are performed in which the environment is gradually made less aggressive in order to prove that growth stops before environmental conditions of relevance to canister integrity are reached.