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2.3.3 Transmutation of minor actinides in fast reactors
2.3.3.1 MOX-fuelled fast reactor
Homogeneous recycling of minor actinides in fast reactor [77]
Np and Am recycling was studied in a large FBR core (see Figure II.14 (a)), for example,
EFR (European Fast Reactor with a 1 500 MWe nominal power rating) type supplied with mixed oxide
fuel. The plutonium isotopic composition in the fuel corresponds to the plutonium vector in a standard
PWR UO 2 fuel irradiated at 33 GWd/tHM.
The parametric study was conducted for 2%, 5% and 10% contents of 237 Np or 241 Am, and for
a 5% content of a mixture with equal proportions of 237 Np and 241 Am.
Multiple recycling of TRU components from reprocessed spent LWR-MOX fuel was
investigated to assess the incineration capabilities of a FBuR [81].
Effects on core reactivity
These effects are roughly equivalent for americium and neptunium. The introduction of
americium and neptunium instead of 238 U causes:
• a reduction of the initial core reactivity due to the high minor actinide capture rate;
• a reduction of the reactivity loss over the cycle due to the transmutation of 237 Np and
241 Am into more fissile isotopes. The effect is more marked for 241 Am because of its partial
transformation into highly fissile 242m Am.
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