Inhibitors for Reducing Hydrogen Ingress During Corrosion of Zirconium Alloys
Bibliographic record
Abstract
Zirconium alloys, used in manufacturing nuclear core components, particularly fuel cladding (in most reactor types) and pressure tubes in CANDU® (Canada Deuterium Uranium) reactors, are usually subject to aqueous corrosion and hydrogen uptake during service. The build up of hydrogen concentration during operation can be a life-limiting factor for these components. In order to slow down the rate of hydrogen uptake and to prolong the operating life of these critical reactor components, a remedial action was targeted. A comprehensive experimental program has been carried out to identify potential inhibiting agents to be introduced into the environment of the corrosion process. The inhibiting agents were expected to intervene in the corrosion reactions to reduce the hydrogen uptake rate. Screening experiments were conducted in short-term exposures (up to 30 days) of coupons from several zirconium alloys, such as Zircaloy-2, Zircaloy-4 and Zr-2.5 weight % Nb, in high temperature (340°C) aqueous out-reactor environments simulating the CANDU heat transport coolant with various chemical compound additives. Several additives of nitrogen-containing compounds appeared to reduce hydrogen ingress significantly; up to 90 % reduction was observed. The beneficial effect of the presence of nitrogen on hydrogen uptake in these exposures might be related to its role in the production of ammonia from hydrogen liberated by the zirconium corrosion reactions. The ammonia generation mechanism has been proposed in the Ceramics literature as a means of increasing the yield of cubic zirconia during the hydrothermal oxidation of Zr in the presence of calcium nitrate. The formation of ammonia is associated with a significant reduction in the hydrogen available for pickup by the alloy. This hypothesis was confirmed in our experiments by the detection of ammonia in the post-exposure solutions. For all tested solutions with nitrogen-containing additives, ammonia was detected in the post-exposure solutions, while no ammonia was found in the post-exposure control solution or other solutions with non-nitrogen additives such as boric acid. Results from post-exposure analyses, oxide characterization, and a preliminary investigation into radiolysis implications are presented.
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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) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.004 | 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".