is this a good breeder?

Looking at the breeding efficiency (bred cells/uran) it doesn't look so good... The best is 8, but that's bitchy and quite micro-intensive.

as far as i know you put 5 lavabuckets in and get an good heat (~9000)

Quote from phaser

I made one with 2.8 eff and low heat gain
http://test.vendaria.net/index…UPPUIIIXPUIPPCPUIPCCPUIPC

If you like explosions go make that one

Dont have to try it i can see it will explode pretty fast by just looking at it

Quote from phaser

well this is way better
http://test.vendaria.net/index…CCPUUPCCPUUPCCCPPCCHCCCCH

Yes, it is better than the one you linked before, but its still no good. The coolant cells will blow in porbably mere minutes, and once they are gone, the reactor platings will go, followed by the HDs and the Nuke perhaps the nuke might blow before the HDs do because of the extreme heat gain you'll experience once the platings are gone.
Sure the hull doesn't get much heat, but that doesn't mean its a good reactor, you have to look at how much heat each individual element inside the reactor receives as well (not to mention that the website you use to make examples shows the actual excess heat, in this link: 197.6)

If you want to make some serious reactors you first of all need to read the tutorial Alblaka posted (if you haven't already), then stop using reactor platings (the completly gray ones) as they in general are useless (note the "in general")

On the topic of what a good breeder is:
If you have no heat surplus e.g. the figure in the bottom right of the simulator says "Heat/Cool Surplus: 0" Then you're at a good start cause that means its a "perfect breeder" and you can then put it at 9k+ heat getting the best out of breeding.

Reactor platings should be changed only nub designs use them and very very rarely someone else uses them. Its a bit useless reactor component.