The effects of oxygen, carbon dioxide and water vapor on reprocessing silicon carbide inert matrix fuels by corrosion in molten potassium carbonate
Section snippets
Background
Silicon carbide is a promising candidate as the matrix material in inert matrix fuels (IMF) which has been designed to reduce plutonium inventories and the long half-life actinides through transmutation [1], [2], [3], [4], [5]. It is necessary to separate the non-transmuted actinides and non-fissioned Pu from the silicon carbide matrix, because complete transmutation or fission cannot be achieved in a single in-core run. A possible method to separate ceria, a surrogate for plutonium, was
Fabrication of SiC pellet with and without CeO2
The fabrication processes of SiC pellets with and without CeO2 have been described by Shih et al. [7]. β-SiC powders (from Superior Graphite) with 16.9 μm (coarse) and 0.6 μm (fine) nominal particle size were mixed at a 3:2 weight ratio with 10 wt.% of SMP-10 (from Starfire Systems Inc.) and with or without 5 wt.% CeO2 in a ball mill for 1 h. The polymer precursor SMP-10 is an allylhydrido-poly-carbosilane which yields almost stoichiometric amorphous SiC. The mixed powder was uniaxially pressed into
Results and discussion
The fabricated SiC pellets had a uniform relative density at 80% and the same dimension (height: 3 mm, diameter: 12.7 mm). Little size shrinkage was observed after sintering at 1050 °C, since the sintering temperature is too low to allow grain growth or pore elimination [7]. However, the amorphous SiC network generated by the polymer precursor during the curing stage connected the adjacent SiC particles to form a solid compact [10], [11]. The microstructure of the cross-section of a SiC pellet was
Conclusions
The molten salt corrosion method for reprocessing the SiC IMFs was initiated and systematically developed in the early and current work. Various gases which may be more effective than air were applied. The order of the corrosion rates in the CO2, O2 and H2O atmospheres is:
The SiC corrosion rate depends upon the molar percentage of the oxidizers (CO2, O2 and H2O) in the atmosphere. Those observations further reinforced the hypothesis that oxidizing gas diffusion
Acknowledgement
The authors gratefully thank DOE for financial support of this project (E-FC07-06ID14741).
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