DETERIORATION OF ZRC-COATED FUEL PARTICLE CAUSED BY FAILURE OF PYROLYTIC CARBON LAYER

The ZrC coating layer is a candidate to replace the SiC coating layer of the Triso-coated fuel particles for high-temperature gas-cooled rea ctors. To understand the behavior of the ZrC-Triso-coated fuel particl es at 1800 to 2000 degrees C, a ceramographic examination and an elect ron probe microanalysis were performed on the ZrC-Triso-coated fuel pa rticles after the post-irradiation heating tests and a thermodynamic a nalysis of the Zr-C-U-O system was carried out. Based on the results o f the examination and analyses, a mechanism of the deterioration of th e ZrC-Triso-coated fuel particles was proposed. The deterioration of t he ZrC-Triso-coated fuel particles observed at 1800 to 2000 degrees C was caused by the failure of the inner pyrolytic carbon layer. (C) 199 8 Elsevier Science B.V.