Community Research and Development Information Service - CORDIS


Long-Term Performance of Candidate Materials for HLW/Spent Fuel Disposal Containers, Final Contract

Project ID: FIKW-CT-2000-00004
Funded under: FP5-EAECTP C


In-depth corrosion studies were performed on preselected container materials such as steels, nickel-base alloys, Ti99.8-Pd and Cu-base materials in rock salt, granite and clay environments. The objectives of the studies were: to determine the influence of essential parameters on corrosion, to gain a better understanding of corrosion mechanisms, and to provide more accurate data for modelling the corrosion of the containers over hundred of years. To achieve these objectives, a combination of long-term immersion experiments, electrochemical studies, and stress corrosion cracking studies were performed.
The results in salt brines (T=150°C) confirm previous findings that the passively corroded alloy Ti99.8-Pd has an excellent resistance to general and localized corrosion, and, therefore, it is the strongest candidate for the realization of the corrosion resistant container concept. The TStE355 carbon steel is subject to general corrosion and its corrosion rate implies corrosion allowances acceptable for thick-walled containers. EB and TIG welding decrease the corrosion resistance of the carbon steel in MgCl2-rich brine, but this problem can be solved by a thermal stress relief treatment of the welds. However, by use of carbon steel containers it must be taken into account that the corrosion of carbon steel in brines, especially in MgCl2-rich brine, results in high amounts of H2 in the repository. If it cannot be tolerated, the steel containers can be corrosion protected by Ti99.8-Pd (best material) or Cu-base materials (resistant to pitting corrosion, reasonable corrosion rates). However, the investigation of material pairs indicates that by failure of the corrosion protection materials and presence of MgCl2-rich brine and gamma radiation (10 Gy/h) galvanic corrosion occurs which results in a significant increase in the corrosion rate of the less noble carbon steel and in a decrease in the corrosion rate of the more noble Cu-base materials.

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