Looks like something like that will have to be the way to go. I've been trying to get a circular design to work, but one of the absorbers towards the center always ends up getting a spike of heat and melting. That's with only the output coming from a single preheater, too. With the way ReactorCraft neutron physics work, I guess that's not really a surprise. With poor enough luck, a single absorber could end up absorbing neutrons from fusion events coming from three of four quadrants simultaneously.
I was hoping to avoid having to put boilers before the absorbers if at all possible, really only because it seems unrealistic. I've broken down now, though, and the following design seems to work acceptably:
Water transportation is achieved with Extra Utilities transport pipes, with a transfer node on each pump (each has 32 speed upgrades and one stacks upgrade). This system seems to provide enough throughput to keep the boilers happy, without crippling the server any.
In the bottom left we've got a dozen neutron irradiation chambers for tritium production. These are, of course, supposed to be used in fission reactors, but if we don't mind losing a bit of efficiency we can make a reactor that only requires an input of deuterium to run, which is worth it in my opinion. Deuterium is piped in the top and tritium out of the bottom, which goes directly into the hydrogen preheater.
Note: you can use fluiducts (etc) to pipe deuterium and tritium into your preheater, but the multiblock will only form with RotaryCraft fluid pipes in the sides and magnetic containment pipes in the top. You can remove these afterwards and use an alternate pipe of your choice instead. Fluiducts even work to transport 150,000,000 degree fusion plasma, though you'd probably need to use a turtle to replace the pipes in your injectors. You'll also still need to build at least one fission reactor to generate enough tritium to get your fusion reactor started, but you don't have to run it indefinitely if you don't care to.
At the top there we've got our standard setup of turbines; there are 24 of them in the screenshot, but I'm sure this thing could power many more, I'm just not bothering because this is in a creative world. I was also considering recycling the steam, but I'm not sure if it's actually worth it to bother when the pump setup produces enough to run this thing anyway.
You'll also notice the huge steel square around the whole setup; this is only there to capture neutrons should an absorber melt (worst case these'll end up accumulating at the edge of a loaded chunk, then drop your server down to 0.03 TPS when someone loads the chunk with 300,000 accumulated neutrons in it), and if you've got a non-melty enough design it isn't really necessary.
On to power usage:
- our pump setup takes 67MW (torque/speed doesn't really matter here, just total power)
- the solenoid magnet engine takes 8MW (256 rad/s @ 32768 Nm)
- the heat ray for the hydrogen preheater takes 2MW (only total power matters)
- the Van de Graaff to keep the magnetic containment pipes from melting takes 1MW (only total power matters, again; this can use less, but it won't establish an arc with less than 1MW and will be a hazard to nearby living entities, including you)
- the two Van de Graaffs I have magnetizing the solenoid magnets, one in two opposite corners, are taking 16kW each (yes, you can run them off two steam engines - I actually recommend leaving the power supply to these very low, because raising it will never establish a sustained arc like with most other things a Van de Graff will interact with, so you really want )
