Unlike other components of a closed fuel cycle, the feedstock to the recy­cling facility has a great deal of variation whether its origin is SNF, or other high — or low-level wastes (legacy defense, medical, industrial, etc.). In addi­tion, the final product and/or waste form needs to meet very tight product specifications or waste acceptance criteria. Failure to do so results at best in materials that need to be reprocessed, or at worst in an orphan waste form with no disposition path. The need to design a robust process that can accommodate variations in the feed and tight product and waste specifica­tions requires bracketing the acceptable feed compositions and testing the process at a wide range of conditions. It is unfeasible to do so experimen­tally, as not all possible feed combinations can be reproduced and it is prohibitively costly. The use of models to design flowsheets allows the design of a facility for a wide range of feed compositions and an optimized process that ensures product and waste specifications are meet.