The fluid reactor, also known as the pressure vessel reactor, is an alternative use of the existing EU reactor. Instead of directly outputting EU, it outputs HU in the form of Hot Coolant. When set up correctly, it is more efficient than a standard reactor.
In order to build a basic fluid reactor, you will need to somehow acquire the following, at a minimum:
- A 'complete' EU reactor set (1x Nuclear Reactor + 6x Reactor Chamber)
- 1x Reactor Access Hatch
- 1x Reactor Redstone Port
- 1x Reactor Fluid Port
- 95x Reactor Pressure Vessel
You can swap out Pressure Vessel blocks for additional interface blocks, as your setup demands.
Building the fluid reactor multiblock is simple: it's a 5x5x5 cube, with a 3x3x3 hollow center in which the EU reactor set is placed. You only need a total of 3 interface blocks (hatches and ports), as shown above, unless you're getting fancy.
Technically, the only necessary blocks are a redstone port to turn your reactor on and a fluid port to input/output coolant/hot coolant. If you don't mind not being able to change your components or monitor the interior without breaking the multiblock, it is completely feasible (if considerably more expensive) to construct a fluid reactor shell using a single redstone port and 97 fluid ports, no access hatch or normal pressure vessel blocks, for the absolute maximum fluid transfer rate. (Source: 6 and 6a from this IC2 forum post)
The fluid reactor uses all the same components as the EU reactor (in the sense of fuel cells, heat vents, etc.) in its internal inventory. However, it also has two 10,000 mB liquid tanks, seen on either side of the GUI: Coolant on the left (blue side), Hot Coolant on the right (red side). You can add or remove the appropriate liquid via fluid cells, using the inventory slots above and below the tanks (or using fluid transfer systems from other mods, connected to the fluid ports). Instead of an EU reading at the bottom, the fluid reactor indicates HU/t (heat units per tick). As you place more heat vents and fuel rods inside of the reactor, that reading will rise - but not as simply as in the EU reactor's case.
Say you ignore coolant entirely and toss in a Fuel Rod (Uranium) and a Heat Vent next to each other inside the reactor. When you turn it on, the core temperature will rise, and your HU/t will remain at 0. Uh oh! The heat vent is working fine - but it's moving heat to the shell of the core reactor, instead of into the surrounding air like the EU reactor, and you didn't provide any coolant to deal with the problem. However, core temperature cannot be cooled (once heated) by simply applying coolant; you need Reactor Heat Vents (etc.) to transfer the core heat to the casing of the internal regular reactor, and coolant to absorb that transferred heat.
In short, to maintain a fluid reactor, you need:
- fuel rods to generate heat,
- heat vents to push that heat around and eventually into coolant, and
- a sustainable source of coolant to absorb and eject all the face-melting heat your neutron-reflected quad fuel rods produce.
Note: A fluid reactor's power generation (HU/t) is not dependent on the fuel rods, but rather the amount of heat vents, unlike its older partner. To be more specific, unmanaged cell heat in the EU reactor would simply make you overheat faster but not reduce your power output; in the fluid reactor, unmanaged cell heat gets stored in the core and not output. The fluid reactor's power output is essentially measured in hot coolant: if you're not producing that, you're not producing power. (Although if you're heating your core, technically you're banking up power to output later. Or you're about to be testing how good your protective shielding is. HAYO!)
If a fluid reactor has Coolant (and it certainly should, if you're actually using it), operating the reactor will turn that into Hot Coolant. This should then be pumped into a Liquid Heat Exchanger (likely several, depending on how fast your reactor produces it), which will produce HU and output plain old coolant, which then goes right back into the reactor to complete the loop.
The heat the exchanger produces is generally used in one of two ways: powering a Stirling Generator to directly generate EU, or heating a Steam Generator to generate either steam or superheated steam. Out of all the ways to generate power, superheated steam is the best; with the correct setup, it can produce significantly more power than a standard EU reactor!
The fluid reactor is inherently safe! This may or may not be a good thing, depending on just how HAYO you are.
In order to function, the fluid reactor needs its 5x5x5 outer shell completely intact. At 85% core heat, that shell will start melting into lava source blocks - and when it does, your reactor will turn off, since it is no longer a complete fluid reactor. It is important to note that even though the reactor won't gain any extra heat, it won't lose any, either, unless you do something to remove it - and so your casing will continue to melt (judging by past observations, only the standard pressure vessel blocks will, not any of the interfaces). And of course anyone within the 7x7x7 area will be damaged by radiation ticks, since the core heat is also > 70%.
In order to make a fluid reactor actually explode (without standing next to it and playing with Heat-Capacity Reactor Plating, anyway), you'd need to take your heat from < 85% to 100% in a single reactor tick, which would mean producing over 1500 HU/t at just the right (wrong) time.
But you wouldn't really want to do that, would you? At least not in your own reactor.