Passivation of Al2O3-based refractories by air-plasma-sprayed coatings of Y2O3 to suppress reaction with gaseous Cs

A simple way to use a commercial Al 2 O 3 -based refractory in a sintering furnace was developed for the head-end system in pyroprocessing. The key was to suppress the intrinsic chemical reactivity of the mullite phase in a refractory with gaseous Cs released from spent fuel in a sintering furnace. Owing to the excellent thermodynamic and thermal stability of Y 2 O 3 , it was deposited on commercial refractories as air-plasma-sprayed coatings. The coated samples maintained their physical integrity without severe delamination after repeated heat treatment at 1450 °C for 12 h in an atmosphere of Ar and 4% H 2 . The chemical reactivity of the coated samples was also confirmed to be satisfactory through a reaction experiment using Cs 2 CO 3 powder. In addition, the coated surfaces were resistant against accidental contamination owing to the formation of non-Cs-reactive yttrium silicate rather than Cs-reactive mullite.