In case you were looking for a SWU definition, this PNNL paper has one:
The separative work unit (SWU) is a measure of the work expended during an enrichment process that is a function of the concentrations of the feedstock, the enriched output, and the depleted tailings; and is expressed in units which are so calculated as to be proportional to the total input (energy/machine operation time) and to the mass processed.