http://lmgtfy.com/?q=gregtech fuision reactor
First one that comes up. Now if you excuse me that was so hard I have to go retire now =D
JK hope that helps.
The first one that comes up is about the old fusion design - so no, this doesn't help at all. (and it's spelled wrong)
To answer the question:
The main recipe is deuterium + tritium cells which produces 1 helium plasma cell. The process takes 128 ticks and the cell can be turned into 8192k EU in a plasma generator, so this gives you 64000 EU/t. (requires 31.25 plasma generators)
However the fusion process requires 4096 EU/t to keep the reactor heated up, so you effectively get 59904 EU/t.
Let's look at the fuel production:
You will need 1 tritium and 1 deuterium every 128 ticks = 6.4 seconds. 1 tritium needs 4 deuterium in a centrifuge and 1 deuterium needs 4 hydrogen cells in a centrifuge. Each process takes 150 seconds so you'll need a lot of centrifuges to keep up with the reactor!
How many?
144 !!
24 centrifuges for deuterium to tritium (150 seconds / 24 = 6.25 seconds) for which you'll need 24*4=96 centrifuges turning hydrogen into deuterium.
another 24 centrifuges turning hydrogen into deuterium for the reactor itself
so:
120 centrifuges for hydrogen to deuterium and
24 centrifuges for deuterium to tritium
Now we also need to create all that hydrogen.
To make it short: you need 30 electrolyzers for that. (5*4 hydrogen / 6.4 seconds ~ 30*4 hydrogen /38 seconds)
so assuming you are not using overclocked machines:
144 centrifuges * 5 EU/t + 30 electrolyzers * 120 EU/t =4320 EU/t for fuel production.
This results in a total EU gain of 55584 EU/t. (a little bit more than that, because we have a very small fuel overproduction)