Evolution of Process-Zone-Based Hybrid Model for Resistance to Crack Initiation Due to Hydrided Region Overloads in CANDU Pressure Tubes
Bibliographic record
Abstract
Abstract Zr-2.5%Nb pressure tubes in CANDU nuclear reactors are susceptible to formation of hydrides. Canadian nuclear standards require evaluations of in-service flaws in pressure tubes for potential crack initiation due to hydrided region overload events that occur when the applied stress exceeds the hydride formation stress. Dual process-zone approach to hydride-assisted crack initiation was adapted by the authors to establish a closed-form functional framework for modeling the resistance of pressure tube material to overload crack initiation. In this process-zone-based framework, the overload resistance during pressure transients is correlated with the material resistance to initiation of delayed hydride cracking under constant applied pressure during sustained reactor operation and varies with flaw geometry and hydride formation conditions. Over the years, three versions of a hybrid predictive model have been developed on the basis of this modeling framework, with each subsequent version incorporating the effects of additional factors affecting the overload resistance. The most recent version included the beneficial effect of temperature, with the overload resistance predicted to increase with temperature at an increasing rate that depends on flaw geometry and hydride formation conditions. Notably, all three versions are probabilistic models that are directly suitable for use in probabilistic evaluations of pressure tube flaws.
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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 | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.002 | 0.001 |
| 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".