2011:12 Analysis of Barrier Performance: Modelling of Copper corrosion scenarios with and without buffer erosion

The purpose of this project was to develop a numerical modelling capacity to address the corrosion of the copper canister under gradually changing transport conditions caused by buffer erosion and removal of buffer mass. Due to the complexity of this task, such a model cannot be realistic in all respects, but the present effort should address the feasibility of solving numerical and computational problems as well as providing preliminary results that can guide future model development. The present results may also be used to preliminarily assess the performance implications of various assumptions and experimental data.

This report contains a range of modelling results from calculation cases corresponding to various conditions of the buffer such as intact buffer, imposed cavities in a buffer, gradually evolving buffer density with a spatial Februbuffer with low buffer density. The results show that the conditions of buffer with mass loss involving buffer density evolution, supply of groundwater sulphide from fractures (intersecting deposition holes) and local SRB activity all contributes to an uneven corrosion profile on the canister. This is not caused by a true localized corrosion phenomenon but rather by what might be termed as an uneven general corrosion of copper caused by geometrically distributed corrodent supply. The present formulation of SRB activity suggests only a moderate influence on copper corrosion.