FAST-1.2.1 incorporates code updates for metal fuel, axial relocation, and convergence improvements for the fuel-to-clad gap closure routine. These changes result in near identical run times and code results of FAST-1.2.1 simulations being near identical or identical to FAST-1.2.

FAST 1.2.1 is proudly developed under NQA-1-2017.

The same current FAST license key, FASTProduct.key, will work with FAST-1.2.1 and FAST-1.2.