Investigation of the Mechanical Behavior of Cast U-2 Wt % Mo for Breeder Reactor Spent Fuel Shipping Cask gamma -Radiation Shielding

摘要

This investigation was conducted to characterize the mechanical behavior of commercial purity heavy section U-2% Mo castings from -40 exp 0 C to 200 exp 0 C and strain rates from 10 exp -4 sec exp -1 to 1 sec exp -1 . The addition of 2% molybdenum to uranium results in formation of a second phase which increases yield strength by approximately a factor of two. Decreasing test temperature produces a gradual increase in yield strength and an abrupt decrease in tensile ductility. This transition in tensile ductility occurs at approximately the same temperature as in unalloyed uranium, and is accompanied by a fracture mechanism transition from microvoid coalescence to cleavage with decreasing test temperature as occurs in unalloyed uranium. The primary effect of increasing tensile strain rate from 10 exp -4 sec exp -1 to 1 sec exp -1 is to increase the ductile-to-brittle transition temperature by approximately 45 exp 0 C. The results of tests which measure the fracture tolerance of flawed samples, however, reveal a gradual decrease in toughness with decreasing test temperature, rather than the abrupt transition observed in smooth bar tensile ductility. These data suggest that U-2% Mo is not inherently notch sensitive over the range of temperatures studied. (ERA citation 07:042460)