I wonder whether you could detect the increased efficiency well before reaching break even (that wouldn't prove that you can reach break even of course)?
Really, if your not asking for money just a location that's a fairly easy sell. If it doesn't work at all that's no real cost to them. If it almost works that's a cheap neutron source that's easy to turn on and off which is valuable. And if it actually works that's one of those world changing things people are willing to support.