Characterization of Copper Coatings at the Closure Weld Zone for Canada’s Used Nuclear Fuel Containers
Bibliographic record
Abstract
Copper-coated steel vessels are the current design of used fuel containers (UFCs) intended for the indefinite underground storage of Canada’s spent nuclear fuel. A 3 mm-thick corrosion resistant copper coating on 41 mm-thick structural mild steel core is fabricated using a combination of electrodeposition (ED) and cold spray (CS) technologies. The UFCs will be exposed to corrosive environments transitioning from aerobic to anoxic, and temperatures and pressures up to 100 °C and 45 MPa, respectively. This study focuses on examining the microstructure, hardness, and early-stage corrosion behavior of the copper coating on a UFC prototype section, in the region of the steel closure weld zone where electrodeposited and cold sprayed copper converge. This region exhibits the most complex microstructure due to the different fabrication processes. Moreover, as the closure weld zone will undergo local annealing to restore the ductility of cold-sprayed copper, the effects of annealing at 350 °C and 600 °C were also evaluated. Microstructural characterization, primarily using electron backscatter diffraction (EBSD), was conducted on both types of copper coatings. By coupling EBSD with high-speed nanoindentation mapping, the local variations in microstructure and hardness in CS copper were investigated, and relative contributions of work hardening and grain boundary hardening were determined. For the first time, a recrystallized layer (ED-RX) was identified at the interface between ED and CS copper, formed due to CS processing induced recrystallization in the top surface of ED copper. Immersion corrosion tests conducted in naturally aerated, neutral pH, 3 mol/L NaCl solution for one week revealed distinct localized corrosion morphologies depending on the fabrication process. ED copper, which is highly textured, exhibited a corrosion morphology strongly dependent on grain orientation, while the ED-RX layer showed more uniform corrosion due to its random grain orientations. In contrast, as-deposited CS copper experienced more severe corrosion at splat interfaces, which became more uniform after annealing. The findings of this study show that the microstructure of copper coatings is highly sensitive to the fabrication processes and significantly influences their mechanical and early-stage corrosion properties. This research will contribute to the selection of final manufacturing processes for Canada’s long-term nuclear waste containers.
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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 | 0.001 | 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".