Click here to see the design of this mark 2-7 ec 
. 
(You do not need water around this nuclear reactor.)
Nuclear reactor
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This is highly innefficient though, way too many IHD
http://www.talonfiremage.pwp.blueyonder.co.uk/reactorplanner…1501521s1r11r10
Thats a really good setup for a 3 uranium input. Only needs 2 chambers and can run forever. (note: that's not my design, just one I remember because I used it)
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I don't make reactor designs but, I turned it into a Mark 1-1
http://www.talonfiremage.pwp.blueyonder.co.uk/reactorplanner…1501521s1r11r10
[Erg, I guess not quite Mk I-I, will not run in lava :P]