SAS4A/SASSYS-1 is a computer code for thermal, hydraulic, and safety analysis of power and flow transients in liquid-metal-cooled nuclear reactors (LMRs). SAS4A can analyze severe core disruption accidents with coolant boiling and fuel melting and relocation, initiated by a very low probability coincidence of an accident precursor and failure of one or more safety systems. SASSYS-1, originally developed to address loss-of-decay-heat-removal accidents, can perform margin assessment in design basis accident (DBA) analysis and for consequence assessment in beyond-design-basis accident (BDBA) analysis.
More information can be found at https://www.ne.anl.gov/codes/sas4a-sassys-1