Retention of fission product caesium in ZrC-coated fuel particles for high-temperature gas-cooled reactors

The ZrC coating layer isa candidate to replace the SiC coating layer of the Triso-coated fuel particle for high-temperature gas-cooled reactors. To un derstand mechanisms of the goad retention capabilities for fission product caesium of the ZrC Triso-coated fuel particles, the particles after post-ir radiation heating tests were examined individually with X-ray microradiogra phy and the caesium inventories of the fuel kernel and coating layers of ea ch particle were measured with gamma-ray spectrometry. The fractional conte nt of Cs-137 in the fuel kernel was found to be different from particle to particle though Cs-137 was not released from the particles practically. The particles, which showed relatively good retention of Cs-137 in the fuel ke rnels, had radially broken inner pyrolytic carbon layers and deformed fuel kernels. The ZrC layer developed the caesium retention capabilities of the fuel kernel through interaction of ZrC with the fuel kernel. (C) 2000 Elsev ier Science B.V. All rights reserved.