1.2. SAS4A/SASSYS‑1 Version 5

In the time since the development of Version 3, several modeling additions and enhancements have been made to meet U.S. Department of Energy programmatic needs. Significant among these are

• Detailed sub-channel models for whole-core analyses to resolve intra-assembly temperature and flow distributions [1‑9]

• 3D visualization capabilities for sub-channel results.

• Extended decay-heat models to support long-term transients and complex, actinide-bearing fuels.

• Support for coupling with external CFD simulations to resolve flow distribution and thermal stratification effects.

• Treatment of axial expansion feedback from assembly duct walls

• Support for spatial kinetics (requires DIF3D-K)

• Extension of the control-system model to include sinusoidal functions that can be used to represent seismic oscillation effects.

• Addition for heavy liquid-metal coolants (lead and lead-bismuth eutectic)

• Support for user-defined coolant properties

• Detailed steam-generator model updates

• Several bug fixes and other enhancements

In addition to the above, a major restructuring of the code has been completed to adapt all source files to free-form source format and new model developments are being implemented using modern object-oriented practices.