Evaluating Corrosion Behaviour of Copper Under Deliquescent Drying/Wetting Cycles in Humid Air Condition
Bibliographic record
Abstract
Most nuclear safety agencies around the world agree that deep geological repositories (DGRs) constructed hundreds of meters below ground in stable host rock formations are viable solutions to safely isolate used nuclear fuel. In Canada, the DGR design involves storing used nuclear fuel in sealed copper coated used fuel containers (UFC) surrounded by highly compacted bentonite blocks (HCB) ~500 m underground. Shortly after emplacement, heat generated by radioactive decay of the used fuel will warm the UFC and its surroundings, desiccating the HCB and decreasing moisture on the container surface. As water vapour is driven from the UFC surface, the presence of minor amounts of dissolved salts may cause droplet formation prior to complete evaporation, during which deposits of salts may be left behind on the UFC. Later, as conditions evolve and the relative humidity increases and the temperature decreases, condensation of liquid water on the UFC surfaces will produce droplets again, due to the deliquescence of minor salt deposits. In either the wetting or the drying scenario, secondary spreading and spatial separation of anodic and cathodic reactions and consequent non-uniform corrosion could be possible, due to the droplet geometry. To investigate this scenario, the quartz crystal microbalance (QCM) technique is being used. The QCM initially consists of a quartz plate, covered by gold electrodes on both sides where a layer of copper is deposited on the crystal by using magnetron sputtering. In this technique, the change in the resonance frequency of a vibrating quartz crystal is correlated to its mass change due to the corrosion process. To investigate the effect of salts and their deliquescence behaviours, different salts (NaCl, CaCl2, and MgCl2) and CR10-E simulated groundwater were loaded on the copper surface using an inkjet printer, and then corrosion tests were performed at different temperatures and relative humidity (RH) values. In parallel, a set of long-term vapour-phase corrosion tests was performed on wrought and cold-sprayed copper coupons at 75 °C and different RH values. As part of the post-experiment analysis, the corrosion products were analyzed using a suite of surface analysis techniques, including optical microscopy, Raman spectroscopy, and scanning electron microscopy (SEM). The results from QCM experiments at RH values below salts deliquescence point showed a low mass change that could correlate with less corrosion in comparison to the experiments at RH values above salts deliquescence point. It’s worth noting that even at RH values below the deliquescence point of the salts, a trace of corrosion was observed which could be indicative of the presence of monolayers of water on the surface. The results obtained from NaCl and CR10-E exposure conditions showed higher mass change and therefore higher corrosion in comparison to CaCl2 and MgCl2 salts. As for the long-term vapour-phase corrosion tests, Raman spectroscopy confirmed the presence of CuO and Cu2O on the surface as corrosion products. Further surface characterizations and mass loss measurements are underway to determine the extent of corrosion on the copper coupons.
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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 | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 0.001 |
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".