Crevice corrosion of nickel-based alloys considered as engineering barriers of geological repositories

Abstract

Nickel-based alloys are considered among other candidate materials as engineering barriers of geological repositories due to their excellent corrosion resistance. These alloys possess unique advantages: they may be used in saturated and unsaturated repositories, hosted by practically any rock type, while also compatible with any (or no) backfill, and have minimal impact in other barriers. Alloy-22 (UNS N06022) has been the most studied of this class of alloys for its potential application in the proposed repositories (namely Yucca Mountain, USA). Crevice corrosion is however an important and often unintended degradation process that may limit the waste container lifetime if a nickel-based alloy is selected. Alloy susceptibility to crevice corrosion is influenced by environmental and metallurgical variables. This review gives an account of the current knowledge regarding crevice corrosion of nickel-based alloys as candidate materials for the corrosion-resistant layer of high-level nuclear waste containers. Although there is a significant amount of research supporting the use of nickel-based alloys for this application, the effect of the different variables on crevice corrosion resistance is described. Special focus is given to the current criterion for crevice corrosion occurrence in repository environments, recent works and criticisms. The presently established criterion appears robust for ruling out crevice corrosion in saturated repositories; however, the development of a less conservative criterion for crevice corrosion occurrence is necessary to use these alloys in unsaturated repositories.

Reliable electrochemical phase diagrams of magnetic transition metals and related compounds from high-throughput ab initio calculations

“…Numerous mTM alloys and compounds have been applied broadly and frequently throughout history. Various conventional mTMbased structural alloys (e.g., Fe and Ni alloys) are widely used in many low-and high-temperature fields, including civilian tools, construction frameworks, biocompatible alloys, [1][2][3] gas turbines, [4][5][6] and nuclear-power equipment, [7][8][9] owing to their excellent mechanical properties, environmental benignity, and oxidation and corrosion resistances. Superior mechanical properties are also present in mTM-based high-entropy alloys, [10][11][12] and their corrosion resistance is under intensive investigation due to its importance.…”

Eu3+ Luminescence in High Charge Mica: An In Situ Probe for the Encapsulation of Radioactive Waste in Geological Repositories

“…1 Isolation of the HLW in deep geological repositories (DGR), through a multi-barrier concept, is currently the most accepted approach adopted by Governments to ensure long-term safety, considering that storage periods range from 500 to 10 6 years. 2 DGR consist of a series of engineered and natural barriers linked, with the purpose of retarding or retaining the radionuclides in the event of a possible leak to the biosphere. In the nuclear waste retention strategy, bentonites, swelling clays composed by an 85% of montmorillonite, have been chosen as part of the engineered barrier system (EBS) as the ideal backfill material in DGR to be used around containers, to seal the tunnel and boreholes.…”

Robust Metallic Actuators Based on Nanoporous Gold Rapidly Dealloyed from Gold–Nickel Precursors

“…First, dealloying is a kinetic competition between surface diffusion of more noble elements and dissolution of less noble elements at the dealloying front, [ 17b ] while chloride‐containing electrolyte can facilitate both surface diffusion of Au [ 17b,32 ] and dissolution of Ni. [ 33 ] The strong non‐oxidation HCl acid prevents surface passivation. Second, the standard electrode potential of Ni 2+ /Ni (‐0.257 V vs SHE) is much smaller than Ag + /Ag (0.799 V vs SHE), which leads to a low critical dealloying potential for Au 25 Ni 75 (≈0.6 V vs SHE), only 50% for Au 25 Ag 75 (≈1.2 V vs SHE).…”