Reactions between U–Zr alloys and Fe at 1003 K

Abstract

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–23at.%Zr alloys and Fe at 1003K have been examined. The selected temperature is 5K higher than the eutectic point in the U–Fe binary system. The effect of lanthanide fission products on the liquefaction was evaluated by adding 1at.%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 1003K in diffusion couples pre-annealed at 923K 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 1at.%Ce has little effect on the reaction of U–Zr alloy with Fe.