Inserters refuse to load seed items into fuel slots, and attempts to load them manually cause a game crash. Turns out the fix is that (fuel_category = "chemical") needs to be added to the seed item definition; looks like it became necessary because 0.15 nuclear is a burner variant. For additional fun you can define whether fueling from seeds has any effect on vehicle acceleration or top speed. :)
(I've also done some other messing around with this mod -- sent you a PM on the forums about it.)
