Fission product release from ZrC-coated fuel particles during post-irradiation heating at 1800 and 2000 degrees C

The ZrC coating layer is a candidate to replace the SiC coating layer of the Triso-coated fuel particles for high-temperature gas-cooled reactors. Post-irradiation heating tests of the ZrC-Triso coated UO2 particles were performed at 1800 degrees C for 3000 h and at 2000 degrees C for 100 h to study the release behavior of fission products. The fission gas release monitoring and the X-ray microradiography revealed that no through-coating failure occurred during the heating tests. The high cesium retention of the ZrC-Triso coated fuel particles was confirmed up to 1800 degrees C. The diffusion coefficient for cesium in the ZrC layer was more than two orders smaller than that in the SiC layer at 1800 degrees C. The diffusion coefficient for ruthenium in the ZrC layer was almost the same as that for cesium in the SiC layer. (C) 1997 Elsevier Science B.V.