Investigating the Potential for Stress Corrosion Cracking of Copper in Sulfide and Nitrite Environments
Bibliographic record
Abstract
Canada’s proposed nuclear waste disposal method includes sealing used fuel bundles inside copper-coated used fuel containers (UFCs) which are then stored in deep geological repositories (DGRs). The UFCs must maintain integrity until the fuel’s radioactivity decreases to background levels. In this project, copper was tested in sulfide and nitrite (expected in a DGR) environments to further understand copper’s susceptibility to stress corrosion cracking (SCC), a corrosion mechanism characterized by a susceptible material cracking when exposed to a corrosive environment and tensile stress. Electrochemical testing methods, specifically potentiodynamic scans, were used to evaluate the copper and identify active/passive transitions. By varying the applied potential, the resulting current quantitatively described the different corrosion regimes of the material, including the target regions where the copper might be susceptible to SCC. Stressed copper samples were submerged in nitrite solutions and held in these target regions to determine if SCC was achievable. When exposed to aerated sulfide solutions, the copper’s behaviour depended on the sulfide concentration, with a passive film (a pre-requisite for many SCC mechanisms) only forming at the highest concentration. In deaerated conditions, the film formed in all concentrations. This led to the hypothesis that oxygen reduces the concentration of sulfide, and that low sulfide concentrations may form a passive film in low-oxygen environments (expected in a DGR). Future work should focus on determining the conditions required to form this film. In the nitrite solutions, it was observed that various passive films could be formed, depending on the applied potential. A stressed copper sample was immersed in a solution for 24 hours with a high nitrite concentration (beyond any real-world application) and held at a potential suspected to allow SCC. Scanning electron microscopy (SEM) analysis revealed that SCC had occurred. Future work should focus on determining the boundary conditions for SCC in nitrite.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.002 | 0.001 |
| 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 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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 teacher head, 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".