Abstracts and Available Papers Presented at the 2002 International RERTR Meeting
BEHAVIOUR OF IRRADIATED URANIUM SILICIDE FUEL
Finlay*, Gerard L. Hofman, Jeffrey Rest, and James L. Snelgrove
Argonne National Laboratory
9700 South Cass Avenue
Argonne, IL 60439
*On assignment from the
Australian Nuclear Science and Technology Organisation
PMB 1 Menai NSW 2234
Irradiated U3Si2 dispersion fuels demonstrate very low
levels of swelling, even at extremely high burn-up. This behaviour is attributed to the stability of fission gas
bubbles that develop during irradiation.
The bubbles remain uniformly distributed throughout the fuel and show no
obvious signs of coalescence. Close
examination of high burn-up samples during the U3Si2
qualification program revealed a bimodal distribution of fission gas
bubbles. Those observations suggested
that an underlying microstructure was responsible for the behaviour. An irradiation induced recrystallisation
model was developed that relied on the presence of sufficient grain boundary
surface to trap and pin fission gas bubbles and prevent coalescence.
However, more recent work has revealed that the U3Si2
becomes amorphous almost instantaneously upon irradiation. Consequently, the recrystallisation model
does not adequately explain the nucleation and growth of fission gas bubbles in
Whilst it appears to work well within the range of measured data, it
cannot be relied on to extrapolate beyond that range since it is not
mechanistically valid. A review of the
mini-plates irradiated in the Oak Ridge Research Reactor from the U3Si2
qualification program has been performed.
This has yielded a new understanding of U3Si2
behaviour under irradiation.