Sadly it does not work at all without other mods
The problem lies in that the heat production increases with reactor temperature. So its either a zero temperature mark 1 reactor (which is not really a mox design) or it is a mark 5+ reactor. From my knowledge you can't run mark 5 reactors with only ic2 exp.
The only way iv'e gotten it to work is using on/off regulation on the reactor with nuclear control and then it still only works with a very specific type of design.
The design that works is the indirect cooling design where the fuel rods does not connect to the cooling directly in any way. You instead pull heat from the reactor and make sure that all the heat that is pulled can be cooled off. you then cycle the reactor on and off while to make sure the reactor does not overheat while you let the cooling do its work.
In any of the direct cooling designs where heat is pulled from the fuel rods, as the reactor starts producing more heat, it will pull more than the components can handle untill either the reactor cools down or the components break.
From my knowledge im the only one so far that has posted working 5x5 mox designs as none of the old designs work to my knowledge. My reactor has run in survival for about 1½ cycles now which is about 15-20 hours in game time so its extremly stable. However the only gain from these types of reactor is that the efficiency is increased, the output is actually lower than regular reactors. my mox can output 750 eu/tick at the most at an efficiency of about 100. If i made a similar mox reactor of the same size it would produce something along the lines of 800-1200 eu/tick and this design would be easily automated with ic2 only and would not require a complicated steam setup. (non 5x5 designs)
As it is right now i would use the old style reactors as they produce a lot more power and it is A LOT cheaper, althought it is at a lot lower efficiency. However considering the only thing getting spent is uranium 238 im not really that concerned with efficiency in mox reactors.