The interaction of iron with molten uranium

The rate of penetration of Armco iron by molten uranium, U-34 at % Fe eutectic and U-77 at % Fe eutectic was investigated in the range of 740 to 1300° C. This was done in an effort to understand the mode of penetration of uranium-base fuels through iron-base claddings. The phenomenon of particular interest was a penetration rate reversal, i.e. decreasing rate with increasing temperature, between 1150 and 1244° C.

Penetration rates at 1150° C were found to be 760 μm/sec in uranium, 690 μm/sec in U-34 at % Fe and 5.5 μm/sec in U-77 at % Fe. At 1244° C these rates changed to 150 μm/sec in uranium, 130 μm/sec in U-34 at % Fe and 5.7 μm/sec in U-77 at % Fe. The study showed that the penetration rate is related to the rate and mode of formation of UFe₂. The rate changes correlate well with the phases of the U-Fe equilibrium diagram.