Abstracts and Available Papers Presented at the
2004 International RERTR Meeting

A microstructurally-based model for the evolution of irradiation-induced recrystallization in U-Mo monolithic and Al-dispersion fuels

J. Rest
Argonne National Laboratory 9700 S. Cass Ave., Argonne, IL 60439, USA

ABSTRACT
 

In a monolithic U-Mo fuel design, in the absence of substantial interaction product development fuel swelling will be the primary deformation mechanism. Irradiation-induced recrystallization appears to be a general phenomenon in that it has been observed to occur in a variety of nuclear fuel types, e.g. U-x Mo, UO2, and U3O8. The recrystallization process results in sub-micron sized grains that accelerate fission-gas swelling due to the combination of short diffusion distances, increased grain-boundary area per unit volume, and greater intergranular bubble growth rates as compared to that in the grain interior. An expression has been derived for the fission density at which irradiation-induced recrystallization is initiated that is athermal and weakly dependent on fission rate. The initiation of recrystallization is to be distinguished from the subsequent progression and eventual consumption of the original fuel grain. The formulation takes into account the observed microstructural evolution of the fuel, the role of precipitate pinning and fission gas bubbles, the triggering event for recrystallization, as well as the evolution of recrystallization as a function of burnup. The calculated dislocation density, fission gas bubble size distribution, and fission density at which recrystallization first appears are compared to measured quantities.

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