The Fusion Reactor is the largest and most expensive multiblock machine currently produced by GregTech Intergalactical. It can be either GregTech's most powerful means of generating EU, or a means to produce some of the most expensive materials by combining some more common materials. This page will be separated based on the individual components of the reactor.
The Fusion Reactor was completely re-designed in version 2.90g. The older version was considerably smaller, but could only produce about half as much energy.
Note: The Fusion Reactor is very expensive, particularly in Chrome. Over 500 Chrome is required to construct a Fusion Reactor. If you intend on building one, the generally accepted "best" way to do so is to have a large array of Industrial Centrifuges processing Redstone Dust.

1. The Hull

"The Hull" is the main body of the Fusion Reactor. It consists primarily of Fusion Coils and Advanced Machine Casings. The idea is that the materials are heated to such high temperatures that they fuse together to create a new element. The number of Advanced Machine Casings varies depending on what other blocks you add to the Reactor (for an example you're able to add a total of 16 Fusion Energy Injectors to the hull for maximum energy storage within the machine, that will be covered further down).

The maximum number of Advanced Machine Casings you will need for a working Fusion Reactor is 120 (creating a machine that can only process Tritium and Deuterium), and the minimum number that you would need is 79 (although there will be many other redundant blocks in the structure). You will need a total of 32 Fusion Coils as well (this number is static). The other blocks in the structure replace some of the Advanced Machine Casings.

Type of Block	Minimum Number	Maximum Number
Advanced Machine Casing	79	120
Fusion Coil	32	32
Fusion Control Computer	1	1
Energy Injector	4	16
Material Injector	2	16
Material Extractor	1	16
	Total blocks:	160

The idea of this is that you have a lot of different options in where you put the other blocks in the reactor.

Maximum Advanced Machine Casings Build:

Note: 1 Material Injector is hidden on the underside of the hull.

Minimum Advanced Machine Casings Build:

Note: 8 Material Injectors are hidden on the underside of the hull.

1a. Advanced Machine Casings

As a reminder the recipe for creating Advanced Machine Casings is the following (and again you need a minimum of 79 and a maximum of 120):

Recipe:
5x Chrome Plates
2x Data Orbs
1x Highly Advanced Machine Block


The placement for the Advanced Machine Casings is based on 3 layers, the top and bottom being the same. They are positioned in the following way:

Top And Bottom Layers

Middle Layer

1b. Fusion Coils

Recipe:
4x Energy Flow Circuits
1x Superconductor
2x Nichrome Heating Coils
1x Iridium Neutron Reflector


Iridium Neutron Reflectors can be used in conventional IndustrialCraft2 Nuclear Reactors, where they function as Neutron Reflectors, with an infinite lifespan. However, they are also used in the recipe for Fusion Coils. The idea of an Iridium Neutron Reflector is to catch neutrons that are emitted when the fusion of materials occurs to prevent them from interfering or causing any other deficits to the reactions (at least in real life, this may not specifically be happening in the Minecraft world). These are created with the following:

Recipe:
8x Thick Neutron Reflectors
1x Iridium Plate (the implosion compressor type)

Note that this does use annoyingly large amounts of Copper and Iridium.

If you've noticed from the placement of the Advanced Machine Casings above there is a hole going along the center of the machine walls. This is where the Fusion Coils go.
The Fusion Coils take the same shape as the first and top layer of the Advanced Machine Casings:


And these are placed in the center of the machine (where they actually fit if you look at the outline of the Advanced Machine Casings:


The point is that you want to have a ring of 32 Fusion Coils, encased by the other 128 blocks in the reactor hull.

2. Fusion Control Computer

"FUUUUUUU-SION, HAH!"
The Fusion Control Computer is the control block of the reactor, and it defines the existence of the reactor. Only one Fusion Control Computer is needed, and can be used, for the Fusion Reactor (add more than one and the reactor won't work).


Recipe:
6x Energy Flow Circuits
2x GregTech Computer Cubes
1x Fusion Coil


The Fusion Control Computer does a few things. Let's take a look at what happens when you access the terminal via right clicking.


The bottom bar with the lightning bolt is the total amount of EU stored in the reactor, and fills as the energy stored fills up (if the machine is complete). The main screen shows the possible set up for the machine. Finally up top on the right if you click the NEI (Not Enough Items) button, you can see all 4 recipes and their requirements.

The Fusion Control Computer can be placed in any one of the below four locations, shown in green.

3. Fusion Energy Injectors

"Stores 10kk EU for the Fusion Reactor"
Now that we have the Hull and Fusion Control Computer hooked up, it's time to supply our Fusion Reactor with power using Fusion Energy Injectors.

Recipe:
4x Superconductors
4x Energy Flow Circuits
1x Supercondensator


Max EU/p IN:
8192

Accepted upgrades:

Minecraft Joules (MJ)

Steam

Every reaction the reactor can carry out has both a startup cost and a running cost, and these Injectors allow you to supply that energy. Each Fusion Energy Injector stores 10 million EU, and is used to transfer energy into the reactor. Up to 16 of these can be installed, allowing for a total capacity of up to 160 million EU. Different reactions have different startup costs, and thus require different numbers of (fully charged) Energy Injectors to carry out.

Reaction	Product	Startup Energy	Minimum Injectors
Deuterium - Tritium	Helium Plasma	40,000,000	4
Deuterium - Helium-3	Helium Plasma	60,000,000	6
Wolframium - Lithium	Iridium Ore	100,000,000	10
Wolframium - Beryllium	Platinum Dust	100,000,000	10

You can place up to 16 of these on the Hull in any of the following locations, shown in blue:

4. Fusion Material Injectors

"To inject your fusable Liquids into the Coils"
Now that our Fusion Reactor has power, it's time to put in our materials to process.

Recipe:
4x Pumps (or Pump Modules)
1x Chest
3x Energy Flow Circuits
1x Highly Advanced Machine Block


Because every reaction the Fusion Reactor can carry out has two inputs, in order to carry out a reaction you must install two Material Injectors, one on top of the ring, and the other directly below on the bottom of the ring.
Fusion Material Injectors can be placed above and below the ring in any of the following locations, shown in red. However, as the Fusion Reactor can only carry out one reaction at a time, installing more than one pair of Material Injectors is pointless.

5. Fusion Material Extractors

"Extracts your fused Materials out of the Coils"
Finally, the last step would be adding something to extract the materials that have been made.

Recipe:
4x Pumps (or Pump Modules)
1x Chest
3x Energy Flow Circuits
1x Highly Advanced Machine Block


You can place up to 16 of these as well, but as the reactor can only carry out one reaction at a time, only one Extractor is needed. The yellow blocks in this image show the possible locations for them:

6. Final Notes/Recipes

Now that you have your Fusion Reactor all set up (and the pictures at the top in the Advanced Machine Casing make more sense) it's time to start processing materials. The first thing you may want to do is to go for Helium Plasma from one of the two recipes to power your Reactor for the more powerful recipes.
As mentioned earlier, each reaction requires a large amount of energy to start; that energy must be stored in the Fusion Energy Injectors for the reaction to begin. Once the reaction has started, you must continue to supply EU to the reactor, albeit at a considerably lower rate. Remember though, if the reaction stops (either due to insufficient materials or insufficient energy), the reactor will need to consume its full startup energy again to continue. To compensate for this, it is recommended that you build up a large stockpile of whatever materials you plan on fusing, before connecting the Reactor.

Input 1	Input 2	Output	Required Starting EU	Running EU/t	Time (ticks)	Time (seconds)	Total EU Per Reaction
Tritium	Deuterium	Helium Plasma	40,000,000	4,096	128	6.4	524,288
Helium-3	Deuterium	Helium Plasma	60,000,000	2,048	128	6.4	262,144
Wolframium	Lithium	Iridium Ore	100,000,000	32,768	512	25.6	16,777,216
Wolframium	Beryllium	Platinum Dust	100,000,000	32,768	512	25.6	16,777,216

One Fusion Reactor can create enough Helium Plasma to fuel 31.5 Plasma Generators, for a total of approximately 64,000 EU/t.
However, the infrastructure (Industrial Centrifuges and Industrial Electrolyzers) required to make the Deuterium - Tritium reaction self-sustaining consumes approximately 14,000EU/t, making the overall energy output of such a reactor roughly 46,000EU/t.