Passivity of Nuclear Steam Generator Tube Alloy in Lead-Contaminated Crevice Chemistries with Different pH
Bibliographic record
Abstract
Abstract The impacts of lead contamination on the passivity of UNS N06690 alloy were studied using samples passivated in simulated CANDU steam generator (SG) crevice chemistries at 300°C and a pH300°C range from 3.22 to 9.26. X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectrometry (SIMS) analyses indicate that lead entered the anodic films but the level of lead impurities incorporated into the anodic films depended heavily on solution pH. In the alkaline chemistry, the presence of lead contamination promoted the incorporation of hydrogen and calcium. The ingress of lead hindered the dehydration during the passivation. Grazing incidence X-ray diffraction (GIXRD) analysis indicated that the lead incorporation would block the formation of spinel oxides during the passivation. Such an effect was enhanced with increasing pH and was hardly observed in the acidic chemistry. When lead contamination was absent, the anodic films were depleted of chromium in alkaline solution but were enriched with chromium in the acidic solution. The presence of lead contamination could reduce both the Cr-depletion in the alkaline chemistry and the Cr-enrichment in the acidic solution. Finally, an effort was made to outline the possible mechanisms for the lead-induced passivity degradation.
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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 | 0.000 | 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) | 0.005 | 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".