So I updated my Direwolf20 pack to the newest version, and found all the mods I added gone. After I added them and loaded up the world, I realized that the ore generation for Big Reactors might be gone. I'm currently running a quarry which would normally have caught Big Reactor ores, but now I'm not so sure. I haven't visited the chunk with the quarry yet, so would there be ore generation at my quarry?
AFAIK it doesn't matter one bit what loads up the area, be it a player or a chunkloader(read quarry). The area has been loaded.
I shall confirm, it doesn't matter if a player or "ghost" player loads the chunks, the results is the same.
However, if the world wasn't ever loaded when you had Big reactors uninstalled, it doesn't matter one bit, game goes on like normal.
Because as far as it's concerned, Big reactors was there, it went to sleep, Big reactors is still there.