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Reddit
reddit.com › r/feedthebeast › making the largest fission reactor from mekanism
r/feedthebeast on Reddit: Making the largest fission reactor from Mekanism
March 9, 2021 -

so I built the largest fission reactor that reaches the maximum burn rate of 1400mb/tick and thought of sharing it so that if anyone else wanted to build it they know the materials that are needed and how it may look like. I just wanna make it clear that my setup is not the best at being cost-effective, this is very much late game:

Materials for 18x18x18 fission reactor (ignore the dirt):

Material for 18x18x18 boiler(ignore dirt):

Materials for 3 17x17x17 industrial turbines:

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Now that the fission reactor, boiler and turbines are built, a lot of sodium needs to be produced so that it can fill the 583,200,000 mB that the reactor needs and also fill the buffer tubes with 1,930,414,584 mB of sodium. So to do so, I built 24 thermal towers running at a production rate of 1000mB/tick (now this is probably overkill but was honestly too lazy to do the math):

24 thermal evaporation towers, each tower being 4x4x18(ender tank is for transporting brine but quantum entanglaporter works just as good. Also sink is for filling the towers with water, you can use mekanism pumps with speed upgrades)

The reactor will also hold up to 7,000,000 mb of fissile fuel.

Finally, make sure to have a buffer between your fission reactor and boiler because, at 1400 mB/tick, the heated sodium from the fission reactor surpasses the capacity for the boiler so it will get stored in the tubes, this is the buffer i used:

9 fission ports connected to 9 boiler ports

Hope this helps, if you have any questions feel free to ask :D

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YouTube
youtube.com › watch
How To Make And Fuel A Max Size Mekanism Fission Reactor | ATM 10 | Ep 11 - YouTube
I hope you treasure the wisdom bestowed unto you -------Links 🚨Twitch: https://www.twitch.tv/foogly-------
Published   December 16, 2024
Discussions

Mekanism Fission Reactor Max Size Problems - Mods Discussion - Minecraft Mods - Mapping and Modding: Java Edition - Minecraft Forum - Minecraft Forum
Hy everybody!! I need a bit of help with the fission reactor of the Mekanism. I've tried to make the max sixe (that in a wiki they say that is 18x18x18) But ... More on minecraftforum.net
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what is the max size extreme reactor and how do i go about to build it?
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🌐 r/allthemods
7
2
October 31, 2025
Fission reactor at maximum size
My reactor is no where near this size but MA made it really easy to produce the required materials for my reactor More on reddit.com
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20
122
July 26, 2025
Max Fission Reactor
I can run a 16*16*18 reactor at 1000mb/tick easily using 3 turbines and a boiler. I pipe in the water with integrated dynamics since the output is up to the integer limit. More on reddit.com
🌐 r/allthemods
21
7
October 10, 2023
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Mekanism Wiki
wiki.aidancbrady.com › wiki › Fission_Reactor
Fission Reactor - Official Mekanism Wiki
Note: You must have Mekanism: Generators installed to have the fission reactor in your game. Without generators, there is no way to obtain polonium using only base Mekanism. ... The structure must be a cuboid of minimum outside size 3x4x3 (along X, Y and Z), up to 18x18x18.
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YouTube
youtube.com › watch
Creating The Largest Mekanism Industrial Turbine and Fission Reactor. - YouTube
In this video we step through how to create the Mekanism Induction Matrix to store crazy amounts of power. To do this we setup the Evaporation Chambers to cr...
Published   April 15, 2023
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Mekanism Wiki
wiki.aidancbrady.com › wiki › Fission_Reactor_Tutorial
Fission Reactor Tutorial - Official Mekanism Wiki
It reaches its maximum at about 1400 mB/t where it reaches the maximum operating temperature of 1200 K. For example with a 5x18x5 reactor (75 fuel assemblies), the boiler's heated coolant tank size must be about twice the size of the reactor's coolant tank (5*18*5 * 100,000 = 45,000,000 mB).
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Minecraft Forum
minecraftforum.net › home › minecraft forum › mapping and modding: java edition › minecraft mods › mods discussion › mekanism fission reactor max size problems
Mekanism Fission Reactor Max Size Problems - Mods Discussion - Minecraft Mods - Mapping and Modding: Java Edition - Minecraft Forum - Minecraft Forum
Hy everybody!! I need a bit of help with the fission reactor of the Mekanism. I've tried to make the max sixe (that in a wiki they say that is 18x18x18) But it doesn't work. I've put the 4 port and the logic adapter and on top of each of 98 rods I've put the control rod but it still not working...
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YouTube
youtube.com › watch
ATM10 EP46 Max Size Mekanism Reactors - YouTube
Go big or go home, right?!Looking for a server? Try here, and get 25% off the *lifetime* of the service! https://www.creeperhost.net/partner/direwolf20
Published   February 7, 2025
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Feed The Beast Wiki
ftb.fandom.com › wiki › Fusion_Reactor_(Mekanism)
Fusion Reactor (Mekanism) - Official Feed The Beast Wiki
Since Mekanism v10, players in ... of D-T fuel into a water-cooled reactor, it produces enough steam to require using six maximum-size ......
Find elsewhere
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Feed The Beast Wiki
ftb.fandom.com › wiki › Fission_Reactor_(Mekanism)
Fission Reactor (Mekanism) - Official Feed The Beast Wiki
June 26, 2026 - The reactor is a hollow cuboid of up to 18 x 18 x 18 blocks made of Fission Reactor Casing. The sides (not edges) of the structure can be replaced by Reactor Glass or Fission Reactor Ports.
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YouTube
youtube.com › watch
Direwolf20 1.16 Ep - 45 Max Size Fission Reactor - YouTube
Direwolf20's 1.16 FTB Pack, we need somemore power, so how about the biggest Mekanisim Fission reactor you can build? Seems reasonable.Intro Song: Memorable ...
Published   February 11, 2021
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YouTube
youtube.com › watch
Ultimate Mekanism FISSION REACTOR Guide | 18x18 Max & Self-Sustaining (ATM10) - YouTube
Hey everyone, in this video I will show you how to set up the MAXIMUM EFFICIENCY Fission Reactor from Mekanism in All The Mods 10. This will be a complete gu...
Published   September 12, 2025
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Reddit
reddit.com › r/allthemods › fission reactor at maximum size
r/allthemods on Reddit: Fission reactor at maximum size
July 26, 2025 -

Something about fission reactors

One reactor, one boiler, three turbines, using the entangled mod to bypass the transfer rate, everything would be perfect, if only it didn't require over 1 million buckets of sodium and 2,000 mB/t of fissile fuel.

The real problem is always generating fuel, but setting the reactor at 750 mB/t already gives me enough polonium to fuel my SPS. In fact, I already have so much atimaterium that I'll leave it at about 200 mB/t for a while. There simply isn't enough fissile fuel production to keep up, not to mention having to generate so much sulfur, fluorite, and uranium.

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SiriusMC Wiki
wiki.siriusmc.net › books › modpack-guides-and-tutorials › page › mekanism-fission-reactor-guide-stoneblock-4
Mekanism Fission Reactor Guide | Stoneblock 4
One Reactor Glass window has been placed on each of the four sides for visibility, with the minimum 4 Fission Reactor Ports. There are many spaces for Fission Reactor Logic Adapters. ... 18x18x18 is the maximum possible Fission Reactor size.
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MineSchematic
mineschematic.com › home › redstone › mekanism fission reactor
Mekanism Fission Reactor - Minecraft Schematic | MineSchematic | MineSchematic
February 17, 2026 - At maximum size (18×18×18), the reactor supports multiple fuel assemblies with a burn rate of up to 1 mB/t per assembly, scaling total heat output linearly. The reactor produces heat only, requiring active cooling with water or sodium to prevent ...
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Mekanism Wiki
wiki.aidancbrady.com › wiki › Fusion_Reactor
Fusion Reactor - Official Mekanism Wiki
While it may be tempting to water cool the fusion reactor, the amount of steam produced quickly spirals out of control. Unless one is willing to build tens of max-size industrial turbines, it is best to keep the reactor running dry.
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GitHub
github.com › wrightcameron › mekansimRatioCalculator
GitHub - wrightcameron/mekansimRatioCalculator: Commandline tool for calculating optimal ratios for turbines and fission reactors within Minecraft mod Mekanism. · GitHub
Commandline tool for calculating optimal ratios for turbines and fission reactors within Minecraft mod Mekanism. - wrightcameron/mekansimRatioCalculator
Author   wrightcameron
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All The Guides
allthemods.github.io › alltheguides › atm9 › extremereactors
Extreme Reactors - All The Guides
FunshineX has made a very detailed video going over all the different sizes of reactors, efficiencies, placement of moderators, and turbine setups.