Transmutation of americium in a large sized sodium-cooled fast reactor loaded with nitride fuel

We have performed the transient analysis of a large sized sodium-cooled reactor loaded with nitride fuel modified by different fractions of americium. Unprotected loss-of-offsite power, unprotected loss-of-flow and unprotected transient-over-power accidents were considered as the postulated transient and simulated with the SAS4A/SASSYS code based on the geometrical model of a BN1200 type sodium-cooled fast reactor (SFR) with the rated power of 2900 MWth. Safety parameters used in the transient simulation model were obtained from the SERPENT Monte Carlo calculations.If 100 K margin to fuel melting was maintained, 2 wt.% and 6 wt.% Am content could be permitted for the nitride fuel loaded BN1200 operating with the maximum linear power rating of 37 kW/m and 33 kW/m respectively, providing Am transmutation rates of 3.9 kg/TW hth and 13.7 kg/TW hth. These transmutation rates are more than 6 times higher than the ones previously reported for oxide fuel loaded BN600 operating with the maximum linear power ratings of 37 kW/m and metallic fuel loaded Integral Fast Reactor (IFR) operating with the maximum linear power rating of 33 kW/m respectively, being their reference cases with permitting 1 wt.% Am content.

► Introduction of Am leads to impacts on core safety parameters.
► Transient analysis was performed for UTOP, ULOF and ULOOP transients.
► UTOP transient is more critical than ULOF and ULOOP transients.
► 1 wt.% additional Am introduction leads to 3% power penalty.
► Nitride fuel loaded SFRs provide the highest Am transmutation efficiency.