Success Story

Improved safety analysis tool for advanced nuclear reactors

Argonne’s SAS4A/SASSYS-1 safety analysis code system is a simulation tool that can perform deterministic transient safety analyses of anticipated operational events, as well as design-basis and beyond-design-basis accidents for advanced nuclear reactors. The original code development was for sodium-cooled fast reactors, and sodium boiling can be modeled. However, basic core thermal-hydraulics and systems analysis features are applicable to other liquid-metal cooled reactor concepts.

As evidenced by the licensee list above, SAS4A/SASSYS-1 is a globally deployed national asset, encompassing decades of Argonne specific research and development.


  • Safety analysis of fast reactors
  • Simulations for operational, design-basis and beyond-design-basis events
  • Passive heat removal and natural circulation flow predictions
  • Severe accident modeling with sodium boiling, fuel melting and pin failure