[count-your-change]

I think what the uranium enrichment so difficult was that it was in the form of a gas that had to be put through nearly endless cycles of a centrifuge to separate the various weights of material.
How the stable nickel isotopes would be obtained I don't know.

[Johnny B.]

HERE is the Wikipedia article on the subject.

There are several methods of enriching specific isotopes, but none of them are something you could do in your kitchen.