RRFM 2009 Transactions - European Nuclear Society

NEUTRONIC STUDY REGARDING TRANSMUTATION FUEL
RESEARCH AT JULES HOROWITZ REACTOR
T. STUMMER
Atominstitut, Vienna University of Technology
Stadionallee 2, 1020 Wien – Austria
Y. PENELIAU, C. GONNIER
Commissariat à l’énergie atomique, Centre de Cadarache
13108 Saint-Paul-lez-Durance – France
ABSTRACT
In order to estimate the possibilities for transmutation experiments at the Jules
Horowitz Reactor several ideas for neutronic and fuel behaviour studies are
investigated at CEA Cadarache. Naturally an exact replication of the burning of
minor actinides in fast reactors, as expected in most transmutation scenarios, is
impossible, but some key transmutation parameters can be investigated in a MTR
neutron spectrum. In this paper a parametric study regarding fuel damage by He
and fission products in AmUO 2 is presented. By varying flux level, uranium
enrichment and americium content of the sample in the JHR [2] reflector a He
production to fission ratio comparable to reference samples in the core of a SFR [1]
can be achieved. The calculations were done with the depletion code DARWIN2.2
[3] using JEF2.2 data and spectra from a TRIPOLI model of JHR and an ERANOS
model for the SFR respectively.
Introduction
For at least the next decade the availability of the preferred experimental fast reactors for
transmutation studies will be limited and so the most should be made out of the far more
numerous thermal MTRs available. Naturally an exact replication of the burning of minor
actinides in fast reactors, as expected in most envisaged transmutation schemes, is
impossible, but some key transmutation parameters can be accessible in a MTR neutron
spectrum. In order to estimate the possibilities for transmutation research at the Jules
Horowitz Reactor [2] several proposals for neutronic and fuel behaviour studies are currently
investigated at CEA Cadarache. One of proposals concerning the increased He production in
MA fuels and the resulting fuel behaviour is presented here.
Concept
Basically the concept rests on the fact that the main drivers for fuel behaviour at a given
temperature are damage caused by fission products and swelling caused by gas production.
Because fast neutrons carry less than 2.8% of the energy of fission products, the neutron
spectrum has only an indirect impact by the way of different fission and capture rates. So the
key parameters from the neutronic point of view would be the He production to fission ratio
vs. time and the burn up vs. time for a given sample. The actual processes producing the He
and fission to reach those parameters need not necessarily be the same as long as the
different chemical composition does not change the fuel behaviour and the sample is
homogeneous enough. Homogeneous enough in this case means that the isotopes of
interest are homogeneously distributed to each other to well below the mean path length of
fission products (~10 µm). So an inert matrix fuel with identical fuel particles would qualify but
one with distinct Am and U fuel particles would not. By modifying the flux level, enrichment
and small changes in the chemical composition of a sample, the changes induced by a
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