On the subject of steam from reactors, I'm confused about how you would siphon off the steam to use elsewhere in Tekkit. Reading from the Atomic Science Wiki about the Steam Funnel it states that they are only capable of piping steam vertically not horizontally. What does that mean? Well I was able to make a subtle change to the design of a fusion reactor I'd recently built, first in creative then in survival. Here's the original design:
As you can see I had three tiers of turbines. To test the output of this, I attached three empty RECs and used the multimeter to measure the throughput into them. Each REC was being charged with about 43 ~ 45 MJ/tick. After reading this thread and the wiki mentioned above I made the following change when I implemented this:
A ring of steam funnels erm... funneling the steam up from the lower tiers so I was able to create large turbines instead. The output increased to 50 ~ 55 MJ/tick for each REC with this arrangement. I suspect it's more about the fact I have a few missing turbines in the first design than any capturing of lost steam via funnels. This isn't by far the best design. It's merely the first I came up with.
All in all I'd have to agree that the lifetime of the fuel seems a bit off. When I first fired this baby up I made 4 stacks of Deuterium cells and that barely lasted maybe 2 hours? I'm unsure of the exact time but it wasn't very long. Yes, cells are inexpensive to make, but has anyone successfully managed to build a auto crafting solution? I haven't ventured into that realm just yet.
Things just need to be better balanced IMHO. I have a bank of 36 magmatic engines that output a totaled 144 MJ/t that is contained in a room about 24 x 16 x 12. It's generously spaced so I can walk around them and requires me to move the lava source pump in the nether about once every two weeks or so. I'm able to flip the switch and leave this setup running (via chunk loaders) virtually indefinitely with no fear of meltdown or explosion.
By comparison my Fusion reactor setup above is 11 x 11 x 6 (just the reactor / turbines portion not the cabling) and produces ~150 MJ/t yet a stack of fuel only lasts about 30 - 45 minutes.