Available data on two alloys from the EBR-II driver fuel development program have been utilized in the construction and validation of mechanistic models aimed at elucidating swelling mechanisms in high density uranium alloys. Swelling predictions are made under ATR conditions for U-10Mo fuels, currently under irradiation in the ATR, and for U-10Zr.

The results of pressurized tube experiments designed to investigate the creep behavior of two precipitation hardened alloys (M813 and PE16) of the Fe-Cr-Ni system are presented. Data are reported covering temperatures from 400°C to 750°C, for accumulated fluences to 16 x 1022 n/cm2, E > 0.1 MeV. This corresponds to five years of testing in EBR-II. Both alloys show greater swelling and creep resistance than 316 CW. A peak in the creep temperature dependence of M813 and PE16 was found that corresponds to the peak swelling temperature. The in-reactor creep resistance is rapidly lost for irradiation temperatures greater than 675°C in both alloys. The results support micromechanisms of irradiation creep which are theoretically linked to the swelling phenomena.