MYRRHA-FASTEF sub-critical core (30 wt. % Epu): chosen approach and preliminary ERANOS results. Some proposals for the T2.2/D2.2 work plan

This work was carried out in the COT/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 report summarizes the presentation done by the author in the COT/WP2 meeting on October 10-14th, 2011, at the SCK-CEN research centre in Moi (B). By working with the 30 wl. % Pu (+ 1.65% Am) mass content in the MOX pellet, a 58 FA BoL care was proposed and characterised at 80 MW power (550 °C as max clad T) by the ERANOS deterministic code. The main results are almost consinstent with the MCNPX ones (obtained by SCK-CEN): the clad T almost respects its constraint at BoL and during the 90 d sub-cycle. The most significant difference is represented by the keff swing during 90 d of irradiation: 1400 pcm (ERANOS) vs. 1700 pcm (MCNPX). Furthermore, the In-to-Out and Mixed shuffle strategies were investigated in a 540 d fuel cycle. To increase the fuel burn up, 6 steps of 90 d were used (instead of 5 x 90 d used in criticai mode). It results that the correspondent equilibrium cores yield almost the same performances. Nevertheless, to sustain the aimed keff (~ 0.965 / 0.95 at BoC / EoC), the equilibrium care should envisage about 72 FA Finally, the first steps of the remaining T2.2 work pian and the timing of the activities (to be performed before the end of the project by the CDT T2.2 partners) is clearly indicated.