Probably Australia or some African country from the middle of nowhere, they’re the only ones left where you can now still open a new uranium project. Most probably the US and Canada still have the stuff in their soil but I don’t see them doing it, what with Idaho and parts of Colorado becoming more like California.
Uranium mining is not your weak link here -- enrichment and fuel assembly production is. As far as I'm aware, Russia has over 40% of global capacity for this.
