pyne/pyne — pull request #519 by gidden (2014-08-31 16:43:29+00:00)
Title: fleshes out enrichment mass ratios and adds a swu calculating API

Hi all,

This PR enhances the C and Python enrichment API by:

* expanding the calculable mass ratios (feed to prod, etc.)
* adding a `swu()` helper function

I think the additions themselves are helpful (at least to a certain user =) ), and I've tried to maintain correct style as I went.