The Transition from Used Fuel Container Corrosion Under Oxic Conditions to Corrosion in an Anoxic Environment
Notice bibliographique
Résumé
The internationally accepted plan for nuclear fuel waste disposal is to store used nuclear fuels within a multi barrier system in a deep geological repository (DGR). Similarly, the DGR concept proposed in Canada involves isolating the used nuclear fuel in copper-coated carbon steel vessels surrounded by bentonite clay buffer boxes and gapfill material. The repository environment is anticipated to evolve from early oxic conditions to later anoxic conditions. Likewise, degradation processes of the UFCs should transition from the initial oxygen-driven processes to those governed by the availability of sulfide as oxidant. This transition may involve the conversion of accumulated (hydr)oxide-type corrosion products produced during the oxic phase to copper sulfide compounds. During this conversion, sulfide species could interact with the UFC surface in several ways depending on the type of (hydr)oxide corrosion products present, the nature and concentration of sulfide species, and other factors: Chemical conversion: in this process substitution reactions replace oxy-anions in the corrosion product layers with sulfide anions. This conversion doesn’t involve redox reactions; therefore, until the conversion is complete, the sulfide species would not drive further corrosion of the Cu surface. Over time, the (hydr)oxide corrosion product layer would be replaced by a sulfide layer. Galvanically-coupled process: in this process sulfides react with Cu metal exposed at the base of pores or cracks in the accumulated corrosion product layer, causing the Cu in those locations to oxidize and copper sulfide to form, while simultaneously expelling oxy-anions and causing cupric or cuprous ions to be reduced elsewhere in the corrosion product layer. Although the conservation of charge in these reactions would mean that no net oxidation of the surface would occur, the spatial separation of the sites where copper is oxidized (on the metal surface) and the locations where reduction occurs (in/on the corrosion product layer) would result in further damage to the Cu layer on the UFC surface, possibly localized at the sites where Cu metal is exposed. Eventually the (hydr)oxide corrosion product layer would be replaced by a sulfide layer and any localization should cease. Direct corrosion: in this process, sulfide species react with the Cu exposed at the base of pores or cracks in the accumulated corrosion product layer, causing further corrosion at these locations without the existing (hydr)oxide species being converted (i.e. process a) or galvanically reduced (i.e. process b). These sulfide species would drive further corrosion of the UFC surface, possibly localized at the sites where Cu metal is exposed. Since this process would not contribute to the removal of the (hydr)oxide corrosion product layer, it is possible that localization, if present, could continue. The research work reported here uses electrochemical and surface characterization methods to evaluate the extent to which each of these possible conversion processes take place, and the timescale/rate of conversion of (hydr)oxide layers grown in different ways. Results so far indicate a fairly rapid and quantitative conversion of oxides according to processes a) and/or b), followed by direct corrosion of the Cu surface by sulfide.
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Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,001 |
| Communication savante | 0,001 | 0,001 |
| Science ouverte | 0,000 | 0,001 |
| Intégrité de la recherche | 0,001 | 0,001 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,001 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule source (Gemma direct ou Codex distillé), pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».