Development on fabrication and inspection techniques for the ZrC-coated fuel particle as an advanced high temperature gas cooled reactor fuel

Fuels for very high temperature gas cooled reactor (VHTR) are being developed to realize long-term operation using the advanced type of coated fuel particle which has the layer replaced the conventional silicon carbide (SiC) to zirconium carbide (ZrC). The VHTR aims at higher outlet coolant temperature than conventional HTR, 950degC and higher and demands high quality fuels that can be used under higher temperatures and high burn up conditions. ZrC is expected as a material which can keep its soundness under such severe conditions, because ZrC is characterized by the high melting point, the thermodynamic stability, the wear resistance, the good compatibility with structural metals, etc. This article describes the large scale ZrC coating process developed using the zirconium bromide method as well as inspection methods for the ZrC-coated layer thickness and density. (T. Tanaka)