Fusion Reactor Mk2 (GregTech 4)

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This article is about Fusion Reactor Mk2 a multi-block structure from GregTech 4 as of version 2.82c. You may be looking for Fusion Reactor from prior versions.

The Fusion Reactor is a multi-block structure added by the GregTech 4 mod. A powerful way to generate EU power by producing Helium Plasma, which is used as fuel in a Plasma Generator. A Fusion Reactor running continuously generates enough Plasma to potentially produce 64,000 EU per tick. The energy consumed by the Reactor and the machines used to produce the resources needed is aproximately 8,396 EU per tick for a net energy output well over 55,000 EU per tick. From GregTech 2.06 onward, all varieties of Fusion Reactor can also be used to produce Iridium Ore (IndustrialCraft 2) and Platinum Dust, although this requires both fuel to be provided and energy from an external source, providing items as output instead of power. It is advised to prepare an area at least 30m square to build the structure.

Planning for a Fusion Reactor[edit]

Before setting up whichever Fusion Reactor your GregTech version contains, it is highly recommended that prior to creating the first block, the player first focuses on preparing for the large task ahead. Simply to make the blocks, a player needs both considerable raw materials and well-developed infrastructure of GregTech machines for refining and processing the necessary ingredients. It is also necessary that the player has an alternative power supply and the technical know-how to automate the process of making fuel for the reactor.

Automation is a critical aspect of operation of the Reactor to sustain fuel output. It is recommended to use methods of automation that are rapid and directly access inventories, such as Factorization Router or ME Import and Export Bus. Many of the recipes involved in making the various pieces of the reactor are complicated and repetitive. An ideal set-up would be to use an ME Auto Crafting in conjunction with an ME Network to store and craft the resources needed to fabricate all the parts necessary for this multi-block structure.

There are 2 ways to produce the resource fuel for a Reactor. The basic recipes are the same, regardless of version, but there are some minor variations in the way the recipes work depending on the reactor version.

  1. Using a Deuterium Cell fused with a Tritium Cell.
    • Advantage: everything can be produced from a starting point of water.
    • Disadvantage: the processing times are very slow [1].
  2. Using a Deuterium Cell fused with an Helium-3 Cell.
    • Advantage: requires fewer machines and the fuel last twice as long.
    • Disadvantage: require a constant source of Endstone Dust.

Reactor Concepts[edit]

A bucket of Plasma generated by the Reactor produces 8,192,000 EU in a Plasma Generator. The Reactor can potentially supply plasma to 32 Plasma Generators. The plasma acts like any other registered liquid under Minecraft Forge, the usual methods of transporting liquids, such as Liquiduct and Tesseract are recommended to store the Reactor's output to a large Iron Tank or a Multi Tank and subsequently supplying the generators.

The Reactor has a warm up delay before it will start the fusion process and so need to be powered by an external source of energy to reach optimal production: 40 to 60 G EU will be consumed, depending on the resource fuel chosen. The Mark 2 Reactor requires a constant source of power to keep in operation, so needs to b connected to the Plasma Generator output ideally via a bank energy cells.

Processing Fuel[edit]

So with your chosen fuel recipe, one can start planning for and making their fuel processing area. This is by far the most important part of setting up your reactor system. Keep this in mind as you continue. The goal here is simple: you need to make fuel at a rate that keeps fusion going. Two kinds, whichever your recipe specifies. You will have achieved success when you are producing at least 1 cell's worth of each type of fuel every 6.4 seconds. Before the Fusion Reactor Mark 2, there used to be only one way of doing this, namely, making a bunch of machines, and adding more and more, potentially creating unnecessarily huge automation complexes. This method still works and has worth. It will always retain the advantage of consuming the least amount of energy.

There does exist a new path for those who prefer to use fewer machines and don't mind sacrificing a smaller chunk of the massive amounts of power they're going to get to do so. People using this path will have to ensure they're providing enough power to the right number of machines and balancing out upgrades properly. Upgrades are now included with the GregTech version that includes the Fusion Reactor Mark 2. It allows IndustrialCraft2 upgrades and additional GregTech 4 specific upgrades to be applied to nearly any GregTech machine - including the Industrial Centrifuge and Industrial Electrolyzer. One applies them by right clicking them onto the desired machine. Be careful as each upgrade applied in this manner is permanent. Upgrading does however greatly reduce the lag footprint of the machines, as each upgrades halves the number of machines required.

Example for overclocking in a Deuterium-Tritium reaction: When adding one overclocker to Centrifuges, you will only need half of them(72 total, not 144), but each will take 20 EU/t, which will reduce the overall energy yield by 720 EU/t (about 1.4%). Using two overclockers will again half the number to 36, but each centrifuge will take 80 EU/t, thus reduce the yield by 2160EU/t (about 4%). Adding one overclocker to each Electrolyzer(16, 32 without overclockers) will reduce the yield by 3840EU/t (about 7%).

Take note that an Overclocker Upgrade increases a GregTech machine's energy needs by 4 times while only doubles its speed (resulting in twice the EU used per operation). To offset the lack of energy if building of external Transformers is not possible or wanted, one can apply Transformer Upgrades (usually one or two) until the machine is able to handle High Voltage. After applying these, one can apply an HV-Transformer Upgrade; the first application brings the machine's maximum voltage to 2048 EU/t and the second application up to 8192 EU/t. One generally needs to pair an Overclocker Upgrade with a stronger powernet, otherwise the possibility exists of modifying machines that will simply not function unless you provide it with massively larger amounts of power (incase the machine needs constant power, like an Electolyzer or Blast Furnace, other machines will just be slowed down).

Once you're producing liquids at the right rate, you may want to consider adding one Liquid Transposer per fuel type, set it to extracting mode, and from here directly pumping your fuels into the Reactor. Generally the Transposer and destination points on the reactor would be connected by Liquiducts or Liquid Tesseracts. One transposer will need to be used per variety of liquid. This has the added benefit of quickly reclaiming a cell and making it available for reuse in the creation of more fuel.

Building the Fusion Reactor Mark 2[edit]

Finally, you've made it through the grueling preparation. That, or you skipped down to this section to peek. Hopefully you can and do make fuel with the best of them and you've got a good grasp on the concepts behind operating this baby. Now you're ready to make the beast of a reactor itself.

The Reactor is a variable multiblock, similar to Alvearys, so the required blocks may change depending on your desired reaction:

The amount of Energy Injectors is dependant from the starting cost of the used recipe, each one has a storage of 10 million EU, so Deuterium-Tritium needs just 4, while the Lithium+Tungsten->Iridium needs 10.

The Reactor is built like the following image shows, the colored wool is to be replaced by the special blocks according to this list or just Advanced Casings.

  • Blue: Fusion Material Injector
  • Red: Fusion Material Extractor
  • Yellow: Fusion Energy Injector
Constructing the Fusion Reactor Mark 2.

Here is an example setup that uses more than the required Material Injectors and Extractors for symmetry reasons as well as 8 Energy Injectors (colored differently):

Expensive Setup

Fusion Reactor Mark 2: Get That Reaction Into Action[edit]

Marvel at your handiwork, and then it's on to business. The first thing to do is attach power to each of the Fusion Energy Injectors at a voltage of up to 2048 EU/p.(In later versions,there is almost no voltage limits as you can hardly reach a voltage of 8192 EU/p or higher) Then right click the Fusion Control Computer and verify that the green power bar at the very bottom has begun to grow. This both confirms that you are receiving power and is a way of verifying that the multiblock was put together properly and formed correctly. It the bar does not grow within a minute or two, ensure that everything was placed properly, the power properly connected, and then, if the power bar still hasn't grown, the multiblock hasn't formed properly. It's just a minor bug; wrench remove a couple of blocks and replace them, and recheck the Fusion Control Computer. Charging should begin then.

Your two fuels need to be routed in to the Fusion Material Injectors at this time. While using liquids piped in directly from a Liquid Transposer emptying the cells it receives is recommended, one may also provide cells, but one will also need to ensure those cells are removed, or else the reaction will halt upon having 64 cells in the output slot. Adequate and responsive automation is key if using cells inside the reactor.

It is important when routing fuel into the Fusion Material Injectors that one type of fuel occupies a Material Injectors in the top and the other one bottom.

From here, you're going to need to set-up your Helium Plasma Output. Liquiducts are highly appropriate for this as you need a liquid pipe with an extraction feature. Attach them to your Fusion Material Extractor and route them according to your design. After doing this, if using Liquiducts, wrench them to Extraction mode and provide a redstone signal, making sure you do not apply a redstone signal to the Fusion Control Computer - this will shut the reactor down. From here, once fusion begins, Helium Plasma will begin to be extracted. All of the circles on the reactor will also glow yellow while the reaction is ongoing.

Once this has begun, take advantage of it and wire a one or two plasma generators to your Fusion Energy Injectors using either 4x Insulated HV Cable or Superconductor Wire. You can use Glass Fibre Cable, but that requires a dedicated HV Transformer at each Generator. Do the same to your fuel processing system, making it self-sufficient. In this case HV-Transformers are recommended, one at each Generator. From there on you might place more MV and LV Transformers or use Transformer Upgrades in all of your machines (Centrifuges would need 2, Electorlyzers 1)

If you planned properly, at this point all you should need to do is watch your reactor and make sure it continues to operate normally. Monitor the amounts of fuels kept on hand over the first few days so you can ensure that your automation is working as planned.Take the time now to pat yourself on the back. You have made one of the hardest multiblock machines in any of the FTB ModPacks, and if you've followed this articles advice in planning. You've done it amazingly well.

If you want to go further with the Mark 2, the only road less traveled is the matter-producing recipes, though these require a significant amount of material, cells, and energy to sustain, making Iridium this way is significantly more efficient than straight from UU. Furthermore, it is possible that there are (as of yet) unknown uses for further adding hardware to the Reactor as shown in the (somewhat hard to read) reactor planner available in the Fusion Control Computer interface.

Fusion Reactor Mark 2: Automation Numbers[edit]

The formula to calculate how many machines you need is as follows:

(items required/production rate)*machine time*(ticks per second/ticks required) = machines

  • Items required: The number of items needed at a time.
  • Production rate: The number of items produced at a time by a machine.
  • Machine time: The number of seconds the machine takes to finish.
  • Ticks per second: Will always be 20.
  • Ticks required: The time required by the fusion reactor. In NEI, it says 128 ticks for both helium plasma recipes.
  • Machines: The total number of machines you need in order to keep up with the demand.

For example, 1 deuterium every 128 ticks. Let's plug that into our equation: Only one deuterium is needed at a time. The industrial centrifuge produces 1 deuterium at a time. And the industrial centrifuge takes 150 seconds to make a deuterium. Our equation is now: (1/1)*150*(20/128) = 23.4375 industrial centrifuges when provided with a steady supply of hydrogen. If we add overclockers, the amount of time required to process is halved, and the amount of energy required to process is quadrupled. By default, industrial centrifuges can use up to 32 eu/tick, or low voltage. With one overclocker, the time is reduced to half, and the energy is increased to a max of 128 eu/tick, or medium voltage. With 2, the energy is increased to high voltage. However, this is a theoretical maximum. The recipe for deuterium only requires 5 eu/tick, not 32. Therefore, we can run one overclocker at LV, 2 at MV, and 3 at HV. Electrolyzers use 120 eu/tick in the recipe for hydrogen, not 128. All of these values will be taken into account for the final values:

Recipe 1, using deuterium and helium-3:

  • 1 deuterium every 128 ticks = (1/1)*150*(20/128) = 23.44 industrial centrifuges (3 with 3 overclockers at hv)
    • 4 hydrogen every 128 tick = (4/4)*38*(20/128) = 5.94 industrial electrolyzers (3 with 1 overclocker at hv)
  • 1 helium-3 every 128 ticks = (1/1)*240*(20/128) = 37.5 industrial centrifuges (5 with 3 overclockers at hv)
    • This also means 16 endstone dust every 128 ticks. (2.5 every second)

Recipe 2, using deuterium and tritium:

  • 1 deuterium every 128 ticks = (1/1)*150*(20/128) = 23.44 industrial centrifuges (3 with 3 overclockers at hv)
    • 4 hydrogen every 128 tick = (4/4)*38*(20/128) = 5.94 industrial electrolyzers (3 with 1 overclocker at hv)
  • 1 tritium every 128 ticks = (1/1)*150*(20/128) = 23.4375 industrial centrifuges (3 with 3 overclockers at hv)
    • 4 deuterium every 128 ticks = (4/1)*150*(20/128) = 93.75 industrial centrifuges (12 with 3 overclockers at hv)
      • 16 hydrogen every 128 ticks = (16/4)*38*(20/128) = 23.75 industrial electrolyzers (12 with 1 overclocker at hv)


  • The Reactor has undergone multiple changes in its lifetime, trending towards providing more and more power at greater and greater cost.


  1. In order to compensate for this, people have been known to create a set-up including over a hundred centrifuges running simultaneously in order to maintain this recipe.