Effect of Grain Dimensions on the Diametral Creep of Zr-2.5Nb Pressure Tubes
Bibliographic record
Abstract
The α grains in hot extruded Zr-2.5Nb pressure tubes are highly elongated in the extrusion direction (tens of microns in length), slightly elongated in the hoop direction (on the order of a few microns), and very thin in the direction of the tube wall (<1 μm). Because diametral creep may limit the operational life of pressure tubes in CANDU reactors, studies to understand the effect of these grain dimensions on creep have been ongoing. In this study, in-service diametral creep measurements from CANDU reactors are correlated with α grain dimensions after accounting for the differences in service conditions (operating time, neutron flux, and temperature). The studied pressure tubes cover a population of Zr-2.5Nb CANDU pressure tubes manufactured since 1974 up to 1995 and therefore include a range of manufacturing processes with a corresponding variation of microstructure properties. The α grain dimensions are measured from the images taken using scanning transmission electron microscopy. A key finding of this study is that the α grain aspect ratio, in the cross section perpendicular to the extrusion direction (with the major axis roughly aligned in the hoop direction and minor axis roughly aligned in the wall direction), is a dominant correlate to explain and predict diametral creep.
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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 | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 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) | 0.007 | 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 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".