Natural Analogues and their Use in Building Confidence in Supporting the Long-term Corrosion Behaviour of Copper-coated UFC

The use of analogues for supporting the prediction of the long-term corrosion performance of the UFC in the safety case is discussed. [...] INTRODUCTION A key challenge in long-term management of used nuclear fuel is the justification of predictions of the performance of the system over periods of thousands, tens of thousands, and hundreds of thousands of years. [...] Figure 2 contrasts the timescale of the evolution of the DGR environment and of the expected minimum UFC lifetime with the ages of some of the geological and archaeological analogues described in this report. [...] Thermodynamic stability can be the result of the redox potential and pH of the environment lying within the stability field of the metal or of the accumulation of corrosion products (dissolved metal ions and/or H2) such that the system is in equilibrium. [...] Near surface dissolution (due to surface weathering effects at outcrop) of copper metal and copper oxides, accompanied by the precipitation of secondary malachite, azurite, copper arsenates and complex Cu-chlorides.” The earliest alteration of the copper to Cu2O occurred prior to compaction of the sediments and the deformation of the plates.