The Potential of Using Chromium Plating to Reduce Ingress of Hydrogen Isotopes in CANDU Reactor Rolled Joints
Bibliographic record
Abstract
Abstract Some recent measurements of hydrogen isotope concentrations in zirconium pressure tubes at the rolled joints in CANDU reactors have been surprisingly high reaching equivalent hydrogen values above the current license limit of 120 μg H/g Zr. These high concentrations have been attributed, in part, to corrosion and concomitant ingress of hydrogen isotopes into the pressure tube. The rolled joint consists of a stainless-steel end fitting into which a zirconium tube is rolled to form a leak-free joint. Chromium plating of the bore of the end fittings is being considered to lessen hydrogen isotope concentrations in the zirconium by reducing galvanic corrosion and by reducing direct contact between the end fitting and the pressure tube. The experiments described in this study were all done dry, without electrolyte present. The benefit of Cr plating under dry conditions was observed to be the same as when an electrolyte is present; hence, ingress of hydrogen isotopes from the end fittings to the pressure tubes is not because of corrosion because corrosion requires an electrolyte. Instead, ingress of hydrogen isotopes happens when hydrogen gas can move between metals when their surface oxides fail under anoxic conditions. The high concentrations are caused by permeation, not corrosion.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 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".