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Conference Article: Microstructures of Silicon Carbide and Pyrocarbon Coatings for Fuel Particles for High Temperature Reactors (HTR)
D. Hélary, X. Bourrat, Laboratoire des Composites Thermostructuraux, Pessac, FRANCE; O. Dugne, G. Maveyraud, CEA, Pierrelatte, FRANCE; M. Perez, CEA, Grenoble Cedex, FRANCE; P. Guillermier, AREVA, Lyon Cedex, FRANCEAbstract
The increase of safety of the high temperature reactors (HTR) is based on the quality of the fuel particles. This must pass through a good knowledge of the microstructure of the four-layers TRISO particles designed to retain the uranium and fission products during irradiation or accident conditions. The aim of this work is to characterise exhaustively the micro and nanostructure of each unirradiated layer (silicon carbide and pyrocarbons coatings) by XRD, SEM, TEM, HR-TEM, SAED and Raman spectroscopy. The long term objective of this study is to provide pertinent parameters for fuel performance codes used to better understand the thermomechanical behaviour of the coated particles.
The examined layers are produced according to the ancient elaboration technique by the CEA/Grenoble using simulated particles with ZrO2-Y2O3 kernels. Data on the SiC deposit are obtained: grain size, polytype form, existence of microstructural defects, chemical composition (ratio Si/C and %Cl) etc…. On the PyC layers, a quantitative estimation of the porosity is proposed and the apparent crystallite size Lc are determined. Their degree of isotropy is also analysed at nanometric scale and compared with direct measurements obtained by optical microscopy coupled with a spectrometer (Degree of Anisotropy in Reflectance). The required PyC must be perfectly isotropic to minimise the neutron irradiation effects that can cause cracking of the PyC and the SiC layers.
All the results are compared with those obtained from the ancient fabrication in the literature.
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key words: Gas Cooled Reactor, Nuclear Technology
- Reference:
- Proceedings of the Conference on High Temperature Reactors, Beijing, China, September, 22-24, 2004
- International Atomic Energy Agency, Vienna (Austria)
- HTR-2004, pp:1-12
- International Atomic Energy Agency, Vienna (Austria)