Chemistry of Waterside Oxide Layers on Pressure Tubes
Bibliographic record
Abstract
Abstract The pressure tubes that contain the fuel bundles and the primary coolant within the core of a CANDU heavy-water reactor are fabricated from a Zr-2.5Nb alloy with a complex microstructure. During reactor operation the pressure-tube interior surface is slowly oxidized by heavy water and a fraction of the deuterium that is released through this process enters the underlying alloy and can reduce its fracture toughness. Considerable variability in deuterium ingress has been observed among the pressure tubes within a single reactor as well as between different reactors. These differences are thought to be due not only to metallurgical variables, such as alloy microstructure and composition, but also to variations in the primary coolant chemistry, including pH and dissolved impurities. In the present study, a combination of surface analytical methods has been employed to characterize the microchemistry and oxidation history of the waterside oxide layers grown on two pressure tubes that were removed from different CANDU reactors. The presence of varying concentrations of iron, manganese and uranium, derived mainly from corrosion of feeder pipes and fuel failures, has been found throughout the oxide layers. An increase in the oxidation rate of one pressure tube later in life could be correlated with evidence of greater open porosity, provided by the depth distributions of impurities, extending deep within the oxide layer.
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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) | 0.001 | 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 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".