Accelerator Driven Systems (ADS) represent one of the possible future strategies for Minor Actinides (MA) transmutation. EFIT - European Facility for Industrial Transmutation is a 400 MWth ADS designed in the frame of EUROTRANS project. It is fuelled by MA and Pu embedded in the inert Mg matrix, cooled by lead (673-753 K), and driven by an accelerator, which provides 15 mA current of 800 MeV protons. The subcritical core is divided into three radial zones, which differ in pin diameter or inert matrix percentage. This design flattens the flux distribution and enables to maximize the power density.
The EFIT core is foreseen to operate with closed fuel cycle. Ideally, only the fission products should be replaced during the reprocessing by an external feed. Consequently, the core should recycle its own spent fuel and burn just the feed. The obvious design aim is to enable the operation with MA feed only (without Pu). Production of each TWh_th in the EFIT core corresponds to the 42 kg of actually fissioned MA feed. If the refueling and reprocessing is done in constant periodic manner, the long-term operation of the core converges to an equilibrium cycle. The initial fuel consists of PuO₂ (45%) and MAO₂ (55%) embedded in an MgO matrix and is uranium-free to avoid additional production of Pu. In spite of the MA feed, the Pu will be present also in the equilibrium core, because its burned amount will be compensated by Pu originated from some MA isotopes. However, the Pu vector will differ.
Recently, a numerical tool named equilibrium fuel cycle procedure for fast reactors (EQL3D) was developed in the FAST group of LRS in Paul Scherrer Institute (PSI). The procedure is based on the ERANOS 2.1 code platform and enables the evaluation of open and closed cycle properties in terms of their equilibrium cycle reactivity, fuel composition, breeding gain, and safety-related parameters. The EFIT core was simulated using EQL3D by means of 51 energy-group neutron-flux calculations and hexagonal-z 3D geometry. This geometry enables to define a specific ring-wise reloading pattern within a multi-batch cycle. The equilibrium results were obtained for open and closed cycle. Safety-related parameters were compared for first and equilibrium cycle and for open and closed cycle. As a general conclusion, the EFIT transmutation capability was proved.