Ah, so it just happens that Reactor only accepts 1 fuel, but since it's in the same class as burners like the boiler (which accepts more than 1) then it wouldn't make sense to do that for the reactor. Gotcha, thanks!

I guess I assumed anything that accepts some type of input could be shift-right-clickable. Feature request then?

Actually it looks like you can't even shift-right click a reactor into a requestor box which is weird. (the items I had copied were just the last things I was able shift-right click from)

If you shift-right click on a reactor, then shift-left click into a requester box, it asks for the contents of the INGREDIENTS for a fuel cell (iron plate, u-235, u-238) instead of a fuel cell.