Study of Hydrogen Evolution for the Outlet Rolled Joint of Candu Reactor Pressure Tube Under Operation Thermal Cycle
Bibliographic record
Abstract
Abstract Hydrogen is presented in CANDU reactor pressure tubes component as initial protium from manufacturing as well as deuterium ingress from heavy coolant occurring during operation. Ingress is more prominent at the rolled joint connection at each end of the pressure tube such that concentration gradients cause inboard diffusion of the hydrogen. High hydrogen concentration could reduce ductility and toughness of material via delayed hydride cracking (DHC) in nuclear reactor components such as pressure tubes. A finite element-based diffusion model, accounting for the ingress and redistribution interaction of protium and deuterium interaction, was developed to study the hydrogen evolution and redistribution at outlet rolled joint region of the pressure tube. To more precisely capture the hydrogen evolution by change in temperature for the reactor thermal cycle, temperature profiles calculated by thermal-hydraulic code, along with reactor startup/shutdown history was applied. This diffusion model predicts both protium and deuterium distributions in good agreement with measurements. The modelling results shows the temperature circumferential gradient is an important factor in redistributing the hydrogen concentration in the pressure tube. Sensitivity to input parameters (such as Terminal Solid Solubility (TSS), diffusivity) is seen to affect ratchetting responses of hydride accumulation at the top of the pressure tube. Modelling results also reveal that protium redistribution causes local increase in protium concentration.
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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 | 0.000 | 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 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".