Thermodynamic evaluation of the quaternary U-Pu-Zr-Fe system - assessment of cladding temperature limits of metallic fuel in a fast reactor

The quaternary U-Pu-Zr-Fe system was assessed using thermodynamic and phase diagram data in order to evaluate fuel-cladding chemical interactions (FCC I) of metallic fuel in a fast reactor. The Gibbs energy of mixing for solut ion phases and the Gibbs energy of formation of compounds in the binary sub -systems were calculated using an optimization procedure. The use of such d ata in optimizing the binary sub-systems enabled appropriate calculations f or the thermodynamic properties of the systems, which were also important w hen extrapolating to higher-order systems. Isotherms of ternary sub-systems were calculated by using the optimized parameters of the binary subsystems . Based on the phase relation data measured in regions of the ternary syste ms, the isotherms were then modified by adding ternary interaction paramete rs. The calculation results agreed well with the experimental data points. Finally, the quaternary system was assessed. The phase relationship observe d experimentally in the diffusion couple of U-Pu-Zr-Fe was in reasonable ag reement with the calculated phase diagrams. (C) 2001 Elsevier Science B.V. All rights reserved.