atw Vol. 63 (2018) | Issue 5 ı May
RESEARCH AND INNOVATION 330
experiments, only negligible interaction
occurred near the interface
[21] and no indications for spinodal
decomposition were found [26].
UMo phase behaviour
Few experiments have been carried
out so far using heavy ions that
directly target effects in the UMo
kernels. One major finding was the
reduction of the orthorhombic
α-phase of Uranium during irradiation,
i.e. the stabilization of the bcc
γ-phase [8]. This is an imperative
requirement for the fuel. The same
effect was observed in-pile [34],
though quantitative comparisons are
still outstanding.
Ternary alloys like U 8 wt % Mo
1 wt % Pt which originally were
considered to improve irradiation
behaviour showed no improvement
and partially even a destabilisation
of the γ-phase of the fuel and were
therefore discarded, too [32].
Conclusion
Altogether, the experiments very well
demonstrate the applicability of the
approach to use Iodine-127 irradiation
for qualitative and even quantitative
experiments to reliably simulate
numerous in-pile irradiation effects.
Even though the burn-up equivalent
that has been reached up to now
with ions was comparably low
(n < ∼ 6 ∙ 10
20
) for HPRR conditions,
important contributions were made to
the development of UMo fuels.
In the future, improved ion beam
diagnostics will open the door to the
analysis of high-burn-up effects like
the recrystallization of UMo kernels.
The necessary fission density equivalents
can be reached with only a few
days of beam time, depending on the
influence of fission rate/ion flux.
Subsequent fission gas implantation
additionally allows studying gasdriven
effects – first demonstration
experiments were successfully carried
out with Kr ions.
The main advantage of this
technique is its effectiveness: No
additional radioactivity is involved,
the complete cycle from experiment
design over irradiation to post irradiation
examinations can be carried
out in a few weeks. Even though the
method has obvious limitations, it is
well able to minimize the number of
costly and time consuming in-pile
irradiation experiments.
Acknowledgements
The authors would like to thank the
MLL staff for their great support
during our beam-times and also in
the times in-between as well as all
members of the working group
“Hochdichte Kernbrennstoffe”.
The work was supported by a
combined grant (FRM1318) from the
Bundesministerium für Bildung und
Forschung (BMBF) and the Bayerisches
Staatsministerium für Bildung und
Kultus, Wissenschaft und Kunst
(StMBW).
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Publication in preparation.
Research and Innovation
Heavy Ions Irradiation as a Tool to Minimize the Number of In-Pile Tests in UMo Fuel Development ı H. Breitkreutz, J. Shi, R. Jungwirth, T. Zweifel, H.-Y. Chiang and W. Petry
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