I'm hazarding a guess here.@Reika: Regarding the requirement to have reactors chunkloaded, have you ever had a world that wouldn't load because a reactor wasn't chunkloaded?
I don't quite understand how the reactor can continue to run when the chunk isn't loaded, but regarding the buildup of neutrons, could they be given a finite lifetime? For instance neutron entities should self destruct after 2 seconds? Given their speed they would still cover an area, but couldn't pile up?
I don't think the problem is that a reactor runs when its unloaded, I think its an issue when it (including its various infrastructure) is half-loaded.