Analysis of Nitride or Silicide Layers on Single or Duplex Coated U-Mo Powder

The interaction layer formation between the U-Mo particle and Al matrix has been considered one of the most challenging issues in the development of U-Mo/Al dispersion fuel. The use of larger-than-usual size U-Mo powder (200∼500μm) can be an acceptable option to mitigate the interaction problem. One of the remedies to the interaction problem is the small amount of Si addition to the Al matrix. Recent irradiation tests have shown that the use of Al-(2-5wt%)Si matrices retard the growth of interaction layers effectively during irradiation. Because the interaction formation also degrades the thermal properties of the dispersion fuel, it is necessary to minimize the interaction layer growth. Recently, KAERI proposed silicide or nitride-coated U-Mo fuel for a minimization of the interaction layer growth. In this study, nitride and silicide duplex coating, as well as a single coating was performed. In addition, to observe the formation of the coating layers, SEM, EDX, and XRD analyses were performed. The silicide coating layer was formed on the surface of U-7wt% Mo particles with a thickness of about 7-8μm and the nitride coating layer has a thickness of about 1-2μm. The results of the annealing tests showed that nitride coating was more effective than silicide coating in suppressing the formation of interaction layers. Nitride coating layer inhibits the formation of the silicide coating layer and the silicide coating layer interpenetrates the inner side of the particle for nitride coating