I'm using BigReactors 0.3.0A as found in the Agrarian Skies modpack. I've noticed that the reactor runs itself out of fuel when I disconnect from my server overnight but nothing that is powered by the reactor gets or uses any of the power it may have been generating. The yellorium isn't super hard to get, especially in this pack but it is rather annoying to have to deal with refueling it every time I'm gone for more than a few hours.

This is intentional. Constructing a control system from redstone, rednet or ComputerCraft/OpenComputers is part of the challenge.