That's reasonably efficient right out of the box - you can simply run it from cold until it runs out of Uranium, then wait for it to absolutely cool. Run it a second time, and when Uranium runs out this time, you'll have 8 re-enriched cells to collect.
There is a way to do better with that reactor, which is to use a boiling water detector, (or a reactor temperature control addin of some sort) to regulate it - with your reactor, automatically switching off at the point of water evaporation will allow the reactor to maintain a steady 8000 heat. This will allow you to collect 8 re-enriched cells after only 1 run instead of two (although the run will be as long as the previous run + cooldown, on average you'll get twice as much output per unit time as before). This improves both the efficiency and (more importantly in my opinion) throughput. With a temperature control addin, you could maintain over 9k heat, and get more throughput still. (I use the boiling water detector because my game is vanilla IC2 with no additional anything.)
See my post on making an automatic safety shutoff here How to make a reactor safety shutoff . To make a regulator instead of a shutoff, all you need is a redstone circuit or something like it to regularly try and turn the reactor back on.
There is a still more efficient approach - making a perfect breeder, but that takes a different reactor design.
duncan,, how best should i get an okay amount of eu while breeding? it never works for me.
Personally I create two classes of reactor - breeders and power reactors. Obviously the breeders make some power, and it's worth collecting it, but the problem with breeders is that you want to maintain them at a high temperature where possible. Because of that, it's not as easy to turn them off, so you're going to get the power they make whether you want it or not.
On the other hand there's no problem at all with letting power reactors go cold (or even with building them so they never get hot at all, as I tend to.) So you can switch them on and off whenever you need them.
That's why I avoid making power in breeders.
To be honest, there's no particular need to breed in your first reactor. There's plenty of Uranium to be mined, and the power you get is more than enough to run all your machines at first. It's only when you start looking at mass fabrication, terraforming and teleporting - all of which use incredible amounts of energy - that breeding your Uranium starts to look attractive.
Even then it's mostly for the fun of it. Breeding U cells is fun, but digging Uranium with a mining setup is just as easy to do. (That's why I'm now sitting on a stockpile of 3 stacks of Uranium, which with my current setup could be burnt for around 8 Billion Eu).