Cycle-Wise Process-Zone Model for Evaluation of DHC Initiation Under Flaw-Tip Hydride Ratcheting Conditions With Creep
Bibliographic record
Abstract
Abstract A key structural integrity concern with in-service flaws in Zr-2.5Nb pressure tubes in CANDU reactors is their susceptibility to delayed hydride cracking (DHC) initiation, particularly for debris fretting flaws under flaw-tip hydride ratcheting conditions. Hydride ratcheting conditions refer to situations when flaw-tip hydrides do not completely dissolve at normal operating temperature, and accumulation of flaw-tip hydrides occurs with each reactor heat-up/cool-down cycle. A cycle-wise process-zone model was developed as an extension to the process-zone model in CSA N285.8. The model is able to predict whether DHC initiation occurs or not during a specific reactor heat-up and cool-down cycle. The development of the cycle-wise process-zone model was driven by the need to include flaw-tip stress relaxation due to creep in evaluation of DHC initiation. The model explicitly accounts for the decrease in process-zone stress due to flaw-tip hydride accumulation with reactor cool-down cycles and due to creep induced flaw-tip stress relaxation during reactor normal operation, which enables proper inclusion of the beneficial effect of creep induced stress relaxation on DHC initiation. This paper presents the cycle-wise process-zone model for evaluation of DHC initiation under flaw-tip hydride ratcheting conditions with creep, focusing on validation of the model for prediction of DHC initiation against laboratory tests on un-irradiated pressure tube specimens under an applied load and thermal cycles with a long hold at the peak temperature that simulates the creep effect under the normal operating conditions. The validation of the cycle-wise process-zone model supports taking credit for creep induced flaw-tip stress relaxation in flaw evaluation for pressure tubes in CANDU reactors.
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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) | 0.000 | 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".