Transmutation of americium in a medium size sodium cooled fast reactor design

We have performed transient analysis of a medium size sodium cooled reactor loaded with different fractions of americium in the fuel. Unprotected Loss of Flow (ULOF) and Unprotected Transient over Power (UTOP) accidents were simulated in a geometrical model of BN600, using safety parameters obtained with the SERPENT Monte Carlo code.For the reference case of MOX fuel, with 1 wt.% Am concentration at BOL and EOEC, the margin to melt following a design basis condition UTOP is about 100 K for a maximum linear rating of 37 kW/m. Introducing Am, the maximum fuel temperature increases by 50 K per percent Am in the fuel. In order to maintain a margin of 100 K to fuel failure, the linear rating has to be reduced by ∼6% for each percent Am added to the fuel.Hence, an Am concentration of 2–3 wt.% in the fuel would lead to a power penalty of 6–13%, permitting a consumption rate of 1.7–3.4 kg Am/TWhth.