You're probably thinking of U238 vs U235 supply. Most reactors today use U235, which is as rare as platinum (if not more rare!). If we switched to breeder react

You're probably thinking of U238 vs U235 supply. Most reactors today use U235, which is as rare as platinum (if not more rare!). If we switched to breeder reactors that used U238, we wouldn't have this problem of running out of uranium.