Crack Growth Resistance of Irradiated Zr-2.5Nb Pressure Tube Material at Low Hydrogen Levels
Bibliographic record
Abstract
The primary factors influencing the crack growth resistance of irradiated Zr-2.5Nb pressure tube material at low concentrations of hydrogen/deuterium are reviewed. These factors include the initial characteristics of the material, which have brought about improvements in the toughness, and the operating conditions in reactor. The paper presents an update on the current status of this work using J-R curves. Such curves are determined from curved compact and rising-pressure burst test specimens at 250°C, i.e., the lower end of the operating temperature range. Some of the challenges encountered in assessing the crack growth toughness of this high-strength, thin-walled material are discussed. The role of chlorine, known to be responsible for the presence of Zr-Cl-C particles and preferential decohesion and fissuring, is also highlighted. The results from the curved compact specimens suggest a limiting level of chlorine above which no further significant degradation in crack growth resistance occurs. This level of chlorine is about 3 wt ppm for material having a low concentration of zirconium phosphide (P < 20 wt ppm). Such results require confirmation using burst tests on material with intermediate levels of chlorine and low levels of zirconium phosphide.
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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) | 0.001 | 0.001 |
| 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 | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.110 | 0.002 |
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; both teacher heads agree on what is shown here.
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".