From what I have understood from the tutorial your reactor doesn't work as you wrote it (I'm an absolute beginner so it's very likely I'm also wrong ) .
the 4 Edge Uraniums should do 3 pulses and generate 4h/pulse (2 adjectant plates) thus 12h / edge (48 h/sec all edges)
>> If there are 2 adjectant plates then there are not 4 edges but 8 edges so 96 h/s all edges .
and the Center ones 4 pulses, emitting 10 heat/pulse thus 40/center (80 h /sec) >>> OK
all together: 128 h/sec. So much to the heat generation. >>>> 96 + 80 = 176
Now to the Cooling: i've got 6 chambers and 1 reactor (2h / chamber and 1h from reactor => 13h/sec) >> Right
The outward cooling should be: 21 air blocks /chamber and 20 air blocks for the reactor (assuming it works like watermills water calculation and they share blocks) = 146 air blocks (-3 blocks for cable and redstone) = 143 Air / 4 = 35.75 h/sec
>> big error ? I believe the air cooling works only for the reactor not for chambers so only 20 air blocks : -5h/s .
On the Inside we have: 24 Coolant Cells, 12 Heat dispersers and 6 reactor plating. -24h/pulse from coolant, -0.6 from the platings. (I got no idea if heat dispersers do cool themself and how fast they do, thus i leave them out for now).
>> ok
Full Calculation: 128 - 13 - 35.75 - 24.6 = 54.65 h/puls not dealt with.
>> 176 - 13 - 5 - 24.6 = 133.4 h/puls not dealt with
Distributed on all cooling cells this means: 54.65/(24+12) ~ 1.5... Which would mean, each HD and Coolant should accumulate 1.5 heat/pulse and should therefore decrease faster than the Uranium. But they dont go down.... not a bit.
>>133.4 / 44 = 2.69 h/p ? one uranium cell lasts 10 000 s and in this case one coolant/HD lasts 10 000 / 2.69 so 3717 s ( 37% of cycle ) . All components linked absorb heat, not only cooling cell, don't it ?
= Cooling cell 
=Uranium cell 
=nothing(vacuum)
=Plating 
= HD