It's the same process either way, and the first few percent are the hardest (as it's super dilute so you need to handle a lot of material). It's much easier to

It's the same process either way, and the first few percent are the hardest (as it's super dilute so you need to handle a lot of material). It's much easier to go from 20% to 90%, than it is to get to 20%. https://en.wikipedia.org/wiki/Separative_work_units https://en.wikipedia.org/wiki/Separative_work_units