Upper limits to americium concentration in large sized sodium-cooled fast reactors loaded with metallic fuel

Abstract

Transient analysis of a large sized sodium-cooled reactor loaded with metallic fuel modified by different fractions of americium have been performed. Unprotected loss-of-offsite power, unprotected loss-of-flow and unprotected transient-over-power accidents were simulated with the SAS4A/SASSYS code based on the geometrical model of an IFR1For acronyms and abbreviations, see the Nomenclature at the end of the paper.1 with power rating of 2500MWth, using safety parameters obtained with the SERPENT Monte Carlo code. The Ti-modified austenitic D9 steel, having higher creep rupture strength, was considered as the cladding and structural material apart from the ferritic/martensitic HT9 steel.For the reference case of U–12Pu–1Am–10Zr fuel at EOEC, the margin to fuel melt during a design basis condition UTOP is about 50K for a maximum linear rating of 30kW/m. In order to maintain a margin of 50K to fuel failure, the linear power rating has to be reduced by ∼3% and 6% for 2wt.% and 3wt.% Am introduction into the fuel respectively.Hence, an Am concentration of 2–3wt.% in the fuel would lead to a power penalty of 3–6%, permitting a consumption rate of 3.0–5.1kgAm/TWhth. This consumption rate is significantly higher than the one previously obtained for oxide fuelled SFRs.