Abstracts and Available Papers Presented at the
1998 International RERTR Meeting

Experimental and Calculated Swelling Behavior of U-10Mo
under Low Irradiation Temperatures

J. Rest and G. L. Hofman
Argonne National Laboratory
Argonne, IL USA

I. I. Konovalov and A. A. Maslov
A. A. Bochvar All-Russian Research and Development
Institute of Inorganic Materials
Moscow, Russia

Abstract

SEM micrographs of U-10Mo irradiated at low temperature in the ATR to about 40 at.% burnup show the presence of cavities. We have used a rate-theory-based model to investigate the nucleation and growth of cavities during low-temperature irradiation of uranium-molybdenum alloys in the presence of irradiation-induced interstitial-loop formation and growth. In addition, the evolution of forest dislocations was calculated based on loop growth and simultaneous climb and glide of unfaulted loops. Consolidation of the dislocation structure takes into account capture of interstitial loops and annihilation of adjacent dislocations, as well as loss to grain boundaries. A di-interstitial is assumed to be the nucleus of a dislocation loop. Cavities are nucleated when two gas atoms come together in the presence of at least one vacancy. Cavity growth occurs by the influx of gas atoms and/or vacancies. In turn, the free interstitial concentration, and thus (due to recombination) the free-vacancy concentration, depends on the dislocation density. Bias-driven growth of cavities can lead to substantial swelling of the alloy (void swelling). However, our calculations indicate that the swelling mechanism in the U-10Mo alloy at low irradiation temperatures is gas driven. The calculations also indicate that the observed bubbles must be associated with a subgrain structure. Calculated swelling and bubble-size distribution are compared with irradiation data.