Investigating the Corrosion Behaviour of Natural Copper as an Analogue to Manufactured Copper
Bibliographic record
Abstract
The safe, long-term disposal of used nuclear fuel is a priority for the on-going use of nuclear power. The international best practice is to dispose of the waste in a deep geologic repository (DGR) using a multi-barrier system. Within this system, the sealed waste container is the critical barrier. In Canada, Sweden and Finland, copper is the chosen material to protect the container against corrosion due to its thermodynamic stability in oxygen free groundwater. To satisfy the regulators, performance assessment models must be developed to demonstrate that the containers will provide the long-term containment. These models are often based on relatively short-term data generated in laboratories, including underground laboratories aiming to simulate DGR conditions. Natural analogues (long-lived Cu deposited in rocks and/or clay) can be used to validate these models, provided that they are representative of similar corrosion issues (i.e., have been exposed to comparable conditions) that were investigated in laboratories. This study involves the characterization of one billion-year-old metallic Cu specimens from various mines in the Keweenaw Peninsula region of Michigan to reveal the material composition and microstructural features and relate them to the electrochemical and corrosion behaviour. Natural Cu specimens retrieved from the Quincy and Adventure Mines are being studied using electrochemical and surface analytical techniques. Present findings reveal that Keweenaw natural Cu exhibits corrosion behaviour different from that of other manufactured Cu material in neutral chloride solution (wrought (SKB) Cu, electrodeposited Cu, cold spray Cu, etc.), with some slight variation in the post-corrosion surface analysis results. Analyses are underway to investigate the factors contributing to the observation of various surface morphologies in the natural Cu specimens after corrosion experiments. Future work will explore the influence of impurities and mineral inclusions on the local reactivity of natural Cu using scanning probe electrochemistry.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".