Reactions between U-Zr alloys and Fe at 1003Â K

In metal fuel for fast reactors, liquefaction at the fuel-cladding interface may occur in off-normal events and enhance cladding wastage. To provide the basis for understanding this liquefaction phenomenon, reactions in diffusion couples of U-23 at.%Zr alloys and Fe at 1003 K have been examined. The selected temperature is 5 K higher than the eutectic point in the U-Fe binary system. The effect of lanthanide fission products on the liquefaction was evaluated by adding 1 at.%Ce to some of the U-Zr specimens. The test results indicated that a liquid phase formed in the reaction zone. The phases in the reaction zone were identified based on electron probe microanalysis results and the calculated U-Zr-Fe phase diagram. The reaction zone growth rate decreased with time. The thickness of the reaction zones at 1003 K in diffusion couples pre-annealed at 923 K was less than those in diffusion couples without the pre-anneal. Zirconium in the fuel alloy has little influence on the threshold temperature for the liquefaction onset, and the addition of 1 at.%Ce has little effect on the reaction of U-Zr alloy with Fe.