MYRRHA-FASTEF sub-critical core (30 wt. % Epu): Temperature feedback effects, main reactivity (and power) coefficients at BoL

This work was carried out in the framework of the CDT/FASTEF EU FP7 project: it deals with the preliminary core design of MYRRHA-FASTEF, a 100 MW LBE cooled reactor (working in both criticai and sub-critical modes) that should be able to demonstrate transmutation and associated technology. The present analysis is focused on the sub-critical option: the 30 wt. % Pu (1.65% Am) mass content in the MOX fuel was envisaged. Starting from the definition of a 58 FA core layout, the main reactivity (and power) coefficients were evaluated at BoL by means of the ERANOS deterministic code and JEFF3.1 library. Furthermore, to supply a first guess of the reactivity coefficients' values of the equilibrium care (needed far T2.3 safety analyses), a 78 FA theoretical BoL care was also investigated. Such preliminary coefficients (obtained at BoL) will be soon refined by the evaluations in the "real" shuffled equilibrium care at BoC / EoC. Besides the reactivity coefficients, the insertion of reactivity due to some incidental situations (as core compaction, presence of void in the fissile zone and LBE flooding in the accelerator beam tube) were also investigated. Therefore, it results possible to establish the safety limits of the system and the allowed level of sub-criticality.