From the point of view of a reactor component reactors are quite simple. Every second a reactor will tick all the IReactorComponents in it via #processChamber, first for the heat run then for the power. The only reason it is split is so MOX can react to the heat a reactor has reliably rather than depending on the components before and after it changing the reactor's total heat.
Uranium (and MOX) calculate the amount of heat from the pulsable components around them (ie components that #acceptUraniumPulse returns true for) during the heat phase. You look around using IReactor#getItemAt(int, int) remembering you get given the stack's coordinates, if it falls outside the reactor's chambers you'll get null, if the slot is valid but empty you'll probably get ItemStack#EMPTY. They then look around surrounding components that return true for #canStoreHeat, attempting to balance their heat output via #alterHeat. Any spare heat is given to the reactor via IReactor#addHeat. For the non-heat run they will call their own #acceptUraniumPulse where they'll add a 1 to the reactor's output using IReactor#addOutput. Then they'll call the same method on the components around them. They'll apply the damage to themselves once this is complete, and turn into depleted forms if they run out fully.
IReactors are meant to be very relaxed about if they're given invalid slot positions, they'll just give you a clearly invalid stack which you should check for before using the result rather than being careful about which slots you ask about. #acceptUraniumPulse depends on how you want to implement it, but for Uranium Cells they avoid changing the reactor heat in the method itself and do it within #processChamber instead. The result is very much for whether you received the pulse or not for other components gauging whether to increase heat or not.
As for uranium ore, you should be fine to change the model rather than anything more drastic if you're just making it glow in the dark. If you want redstone ore style particle effects then that probably won't be enough, but it definitely depends on what you're trying to do.