Corrosion behaviour of Mg alloys cladding from nuclear reactors fuel in alkaline solutions
Résumé
The reprocessing of spent fuel from the French UNGG (Graphite Gas Natural Uranium) nuclear power plants generates cladding wastes such are Mg-Mn alloys. A storage strategy is to encapsulate these wastes into cement matrix. The main issue is hydrogen evolution as the main consequence of the corrosion of Mg alloys, regardless of concrete radiolysis. In fact Mg acts as an anode in most of galvanic corrosion systems and the hydrogen can be produced either by water reduction or by Anodic Hydrogen Evolution (AHE). In the last case, an increase in the rate of hydrogen production with increasing applied potential is observed. This phenomenon called "Neg-ative Different Effect" (NDE) is in contradiction with the conventional Tafel equation. The corrosion of magnesium may produce Mg$^+$ cations which react quickly with water to produce hydrogen and stable Mg$^{2+}$ cations. The interstitial solution in concrete pores is characterized by a very high pH. To reproduce the pH solution around 13, 0.1M NaOH solutions were prepared and used as electrolytes from electrochemical experiments. Stainless steel, platinum and graphite were used as cathode to investigate basic galvanic coupling as it can be encountered in the real wastes. The purpose of this work was to investigate the galvanic corrosion of Mg alloys in the high pH solutions. The study of Mg corrosion behaviour was carried out using elec-trochemical measurement: ZRA mode. The analysis of the surface and the corrosion products were performed by Raman spectroscopy. The first results showed a galvan-ic corrosion rate more important with stainless steel rather than with graphite.
Origine : Fichiers produits par l'(les) auteur(s)
Loading...