Development of Eutectic Free Cladding Materials for Metallic Fuel

AbstractHistorically, it is well known that U base metallic fuel has a lower eutectic temperature with stainless steel cladding. In the phase diagram for the U-Fe binary system, the eutectic temperature is 998K. The eutectic reaction is a limiting factor for raising reactor operation temperature.For the purpose of development of eutectic-free cladding materials, three kinds of diffusion-couple tests with 10mass%Zr alloy were conducted at a temperature of 1027K for 2250hrs.We selected the following materials: (a) nitrogen charged zirconium foils, (b) vanadium foils of commercial grade, and (c) nitrogen charged ferritic stainless steel (HT-9).The results showed that typical Zr rich layer was observed in all of these materials. Zr rich layer appeared to act as a barrier against inter-diffusion of U, Fe. The barrier provided immunity to the eutectic reaction.Discussion was made on C-14 problems in relation to another desirable thermodynamic characteristics of Zr such as carbon-14 immobilization.EPMA analysis ...