Magnesium potassium phosphate cement: a promising binder for the conditioning of aluminum-magnesium alloys waste

Abstract

International audienceThe reprocessing of spent fuel designed for natural uranium – graphite – gas reactors has produced somewaste with aluminum alloys, which need to be stabilized and solidified before their final disposal. Portlandcement is extensively used for the conditioning of low-level and intermediate-level radioactive waste;however, its high alkalinity is a serious obstacle to aluminum stabilization, as it is oxidized by the mixingsolution, with production of dihydrogen. This work investigates a new solution consisting in usingmagnesium potassium phosphate cement (MKPC) instead of Portland cement (PC). Gas chromatographyand electrochemical impedance spectroscopy (EIS) are used to monitor the corrosion of pure aluminum and aluminum-magnesium alloys containing 2 to 4.5 wt.% of Mg in MKPC mortar. EIS provides qualitativeinformation about the corrosion, but also makes it possible to assess the corrosion current using anequivalent electrical circuit linked to the kinetic parameters of the postulated corrosion mechanism. It isshown that the corrosion current of the alloys, regardless of their composition, is reduced by about twoorders of magnitude in MKPC mortar as compared to Portland cement mortar. This result opens up newprospects for increasing the incorporation rate of reactive Al metal in a cementitious matrix