Looks very similar to this one which is the best one of its kind if i remember correctly (cost wise) However it is a shame you arent using some of the iridium reflector designs
http://prnt.sc/849249
If you are looking for good nuclear design take a look at this forum thread in IC2 forum i did a while ago. Lots of nice designs for both regular, mox, 5x5x5, mox 5x5x5 and mark 5 reactors (using nuclear control) as well as a guide for how to build them.
http://forum.industrial-craft.net/index.php?page=Thread&threadID=11729
Once i get into the nuclear age i will probably try out a few of my high output high efficiency iridium reflector designs like (there are those with higher efficiency also but lower output)
Uranium:
2303230C0A120D0C0A03230C0D0C0D0C0D12230C0D0C0D0C0D0C0D0C0D0C0D0C0D0C0D0C0D0C0D0C0D0C0D0C0D140A140D120D120A12
http://prntscr.com/845im0
Eu/t: 240 (672-976)
Efficiency: 12 (33,6-48,6) [Meu/fuel rod]
Cost: 512 coal, 793 copper, 4 diamond, 84 gold, 4 iridium reinforced plate, 558 iron, 20 lapis lazuli, 44 redstone, 132 rubber, 655 tin, 8 uranium fuel
By: Blackpalt
Or
Thorium
1523230D140A0C0A12231C1C0C0D0C0D0C0D231C1C230C0D0C0D0C231C230C0D0C0D0C0D0C230C0D0C0D0C0D120A120D0C0A120D0C0A
http://prntscr.com/845f21
Eu/t: 136 (532-782)
Efficiency: 6,8 (26,6-39,1) [Meu/fuel rod]
Cost: 1 advanced alloy, 1024 coal, 994,33 copper, 5 diamond, 60 gold, 8 iridium reinforced plate, 522,5 iron, 16 lapiz lazuli, 1 lead, 34 redstone, 102 rubber, 20 thorium, 1155 tin
By: Blackpalt
Both can be run in both regular and 5x5x5 mode. Especially the thorium one is very well suited for 5x5x5 as it produces little power but a lot of heat (which is energy for 5x5x5 reactors). The uranium reactor especially in 5x5x5 mode should produce a crazy amount of power with the boost to fluid reactors. For instance the uranium reactor produces 1344 heat/s (and 1 l/s of hot coolant = 40 superheated steam/s) with the new x4 boost in infitech should mean you can produce 1344*4X40= 215040 l superheated steam/s with one of these reactors. That means with a 140% turbines (quite many) you would produce (215040+215040/2)*140%/20=22549.2 EU/tick. Quite a significant amount of power from just one 5x5x5 reactor
I might also do some of the crazy mark 5 reactors with nuclear control but ive found them to be a bit unsafe in the long run. They usually blow up at some point due to some chunkloading problem or something similar so i will probably stay with nice and safe mark 1 reactors like those above