RRFM 2009 Transactions - European Nuclear Society

consequence, the inter-pin space is minimized which implies to make use of a cladding
material without swelling under irradiation.
Furthermore, the use of SFR reactor to recycle minor actinides (either in heterogeneous or
homogeneous mode) has to be considered from the very beginning of the core design and
assessment of potential MA impact on the SFR safety related parameters.
Figure 1: SFR fuel element and reference core design 3600 MWt (1500 MWe)
The selection of a reference SFR fuel
As far as fuel is concerned, two main options are investigated in France for the design of
large SFR cores.
• Because of the rather short timescale for the prototype, and the important and
satisfactory feedback experience built upon oxide fuels, MOX is considered as the
reference fuel at least for the prototype start-up core. Oxide fuel is also a very serious
fuel candidate for the longer term commercial SFR. Preliminary calculations are
performed to assess the potential merit of a design options such as a Sub-Assembly
(SA) with a tight lattice of large diameter pins, a sodium plenum at the top of the core,
the use of moderator material to further optimize the efficiency of the Doppler reactivity
effect.
• More challenging options (for the long term SFR) also are investigated: core concepts
based on the use of denser and colder ceramic fuels (carbide is currently preferred to
nitride) so as to assess the potential benefit of (1) reduced core volume (with therefore a
higher power density), (2) higher safety margin between the fuel operating temperature
and melting point and (3) better compatibility between coolant and fuel material in
accidental conditions.
Focused on some other key design parameters (such as high breeding capability, ‘intrinsic’
safety, expected performances of the fuel cycle based on pyrometallurgical processes, nonproliferation
issues), several countries (like India, China, Korea, Japan, USA) are
considering the metal fuel for the SFR either as a long term reference or as a challenger to
oxide fuel. In such a context, the merits and drawbacks of the metal fuel option for large SFR
cores are re-assessed in France, and its performances are compared with that of oxide and
carbide fuels.
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