Extreme Reactors

Extreme Reactors is a power generation mod built entirely around large multiblock machines that you construct block by block inside your world. It is the modern continuation of the classic Big Reactors, and its whole purpose is turning a radioactive fuel called Yellorium into enormous amounts of Forge Energy to run the rest of your tech setup.

Instead of single machines, you build reactors, turbines, and processing plants out of dozens of parts, then tune them for efficiency. The scale is the appeal: a first reactor can be a humble cube in a cave, while an endgame turbine setup can push tens of millions of Forge Energy per second. One friendly detail sets this mod apart from other nuclear options, since these reactors do not explode or melt down when things go wrong.

This guide walks through the entire mod, from mining your first Yellorite Ore to running an actively cooled reactor feeding a coil-lined turbine. Along the way it covers the confusing bits that trip up new players, like backwards Control Rods, the multi-stage fuel cycle, and why your reactor keeps burning fuel even when the battery is full.

Getting Started with Extreme Reactors

Getting a first reactor running takes a handful of new materials and a small pile of crafted parts. There is a lot to take in at once, and many players describe the first build as intimidating because a reactor has so many intricate pieces. The good news is that a tiny reactor works exactly like a giant one, so you can learn everything on a cheap 3x3x3 cube before scaling up.

Head underground in the Overworld and mine Yellorite Ore, which generates in every Overworld biome up to around Y 32, with a Deepslate variant near bedrock. Smelt the ore in a Furnace to get Yellorium Ingots, the base fuel that powers every reactor. Some modpacks rename or swap Yellorium for uranium, but the two are interchangeable through item tags, so uranium works fine where a pack uses it.

Smelt Coal or Charcoal in a Furnace to produce Graphite Bars. Graphite is the backbone of early reactor construction, going into Casings, Control Rods, and Fuel Rods. You will burn through a lot of it, so smelt a healthy stack before you start crafting parts.

A working reactor needs at minimum a Reactor Casing shell, one Reactor Controller, at least one Fuel Rod with a Control Rod on top, one Solid Access Port for fuel, and one Power Tap to pull energy out. Reactor Casing is crafted from 4 Iron Ingots, 4 Graphite Bars, and 1 Sand, and each craft yields a single Casing, so make plenty.

The Basic Reactor Controller takes 4 Reactor Casings, 2 Yellorium Ingots, 1 Diamond, 1 Redstone Dust, and 1 Comparator. You only ever need one Controller per reactor, and it is the screen you open to run the machine. Reactor Glass is optional and lets you see inside, needing just 1 Casing and 2 Glass per craft.

Build a hollow box where the entire frame is Reactor Casing, filling the walls with either Casing or Glass. Place a vertical stack of Fuel Rods in the interior with a Control Rod capping the very top of each stack, then add the Controller, a Solid Access Port, and a Power Tap onto the outer walls. When the structure is valid, the parts light up along their edges to confirm the reactor formed.

Insert Yellorium Ingots into the Solid Access Port, which draws fuel into the Fuel Rods automatically. Open the Controller and press the on button, then watch the Core Heat and Casing Heat climb as power begins to generate. Extreme Reactors has no pipes of its own, so use cables or item pipes from another tech mod to move the energy into storage.

Reactor Materials and Ores

Beyond Yellorium, Extreme Reactors adds a small family of ores and materials that you unlock as you progress. Knowing where each one comes from saves a lot of wandering, since the three worldgen ores are split across all three dimensions.

Yellorite Ore and Yellorium

Yellorite Ore is your bread and butter, generating throughout the Overworld underground and smelting into Yellorium Ingots. It is common and low, spawning up to about Y 32 with a Deepslate version deeper down, so any standard mining trip will turn up plenty. Yellorium is the fuel every reactor starts on and the material your whole progression builds outward from.

Graphite Bars

Graphite is not mined, but smelted from Coal or Charcoal into Graphite Bars. It doubles as a radiation moderator inside reactors and as a crafting ingredient in most Basic reactor parts. Because nearly every early component wants Graphite, treat it as a staple you keep stocked at all times.

Anglesite and Benitoite

Anglesite Ore generates only in the End, and Benitoite Ore generates only in the Nether, with both dropping their crystal directly when broken. You will not need either for a first reactor, but they become important later for coolants, endgame fuels, and the Energizer. Grab a stack of each when you visit those dimensions so you are not forced back later.

Cyanite Waste

Cyanite is the waste product your reactor creates as it burns Yellorium, and it collects inside the Fuel Rods alongside the fuel. Keeping it out of the core matters, since a reactor clogged with waste performs worse. Do not throw Cyanite away, because it is the key ingredient for reinforced parts, turbine blades, and the entire upgraded fuel cycle.

Building a Basic Reactor

The Basic Reactor is the entry-tier machine, and it can still generate serious power despite its simple parts. Every Basic component is built around iron and Graphite, which keeps it affordable. This section breaks down the parts, the assembly rules, and the one control that confuses almost everyone.

The Core Reactor Parts

The Control Rod is crafted from 4 Reactor Casings, 2 Iron Ingots, 1 Graphite Bar, 1 Redstone Dust, and 1 Piston, and one sits on top of each Fuel Rod column. The Fuel Rod itself uses 4 Iron Ingots, 2 Graphite Bars, 2 Glass, and 1 Yellorium Ingot. Both are one-per-craft recipes, so a tall reactor needs several of each.

The Solid Access Port, built from 4 Casings, 2 Iron Ingots, 1 Wooden Chest, 1 Hopper, and 1 Piston, moves solid Yellorium and Cyanite in or out. The Active Power Tap uses 4 Casings, 4 Redstone Blocks, and 1 Redstone Dust to deliver energy. For manual control of ports, the Extreme Wrench is crafted from 4 Iron Ingots, 1 Green Dye, and 2 Wool.

Assembling the Multiblock

A Basic Reactor can be as small as 3x3x3 and as large as 5x5x5. The outer frame must be solid Reactor Casing, while flat wall faces can be Casing or Glass for visibility. Fuel Rods run in vertical columns inside the hollow interior, and each column must be topped with a Control Rod placed on the same side.

Making the reactor wider improves efficiency because there is more room for cooling around the rods. Making it taller increases raw power output but burns more fuel, since taller columns hold more Fuel Rods. You do not have to fill every interior slot with Fuel Rods, so start with a few and expand as your fuel supply grows.

Control Rods and Insertion

Control Rods use an insertion percentage that feels backwards to most players, and this is the single most common point of confusion. An insertion of 0% means the rod is fully retracted and the reactor burns fuel at maximum rate, while 100% pushes the rod all the way in and nearly shuts the reaction down. In short, lower insertion equals more power and more fuel use.

You can set each rod individually or change them all at once from any Control Rod screen. Raising insertion is a simple way to throttle a reactor that is burning fuel faster than you need. Holding it near the top of the fuel bar keeps consumption low while your machines idle.

Reading the Controller

The Controller screen shows Core Heat, Casing Heat, Fuel Reactivity, and the internal energy buffer. Core Heat is the temperature of the fuel, and higher Core Heat raises fuel usage, so you generally want it lower. Casing Heat is what actually drives energy output, so a hot casing with a cooler core is the efficient sweet spot.

Basic vs Reinforced Reactors

Once you outgrow the Basic tier, Reinforced parts unlock much bigger builds and active cooling. There is no research gate stopping you from jumping straight to Reinforced, since the only real barrier is producing Steel. The table below compares the two tiers on the details that matter most.

The Reinforced Reactor Casing swaps iron for Steel, using 4 Steel Ingots, 4 Graphite Bars, and 1 Iron Block per craft. Steel is not a vanilla material, so you will lean on another mod such as Mekanism to produce it, which is the main reason players stay on Basic parts for a while. A compact 5x5x5 Reinforced reactor sips almost no fuel while still producing plenty of power for a typical base.

The biggest reason to go Reinforced is active cooling, which only the Reinforced tier supports through its Fluid Ports. Active cooling is what unlocks Steam, turbines, and the multi-million energy setups that make this mod famous. Until then, Basic reactors are genuinely good and worth mastering first.

Cooling: Passive and Active

Cooling is the heart of reactor efficiency, and Extreme Reactors offers two very different approaches. How you cool the core decides whether the reactor makes energy directly or produces Steam for a turbine. Getting this right is the difference between an average generator and an incredible one.

Passive Cooling and Moderators

A passively cooled reactor generates Forge Energy directly from Core Heat and needs no external coolant. Filling the empty interior spaces around your Fuel Rods with a moderator like solid blocks or Water improves the reaction, raising output while lowering fuel burn. Even plain Water noticeably boosts efficiency compared to leaving the gaps as air.

The best interior layout uses a checkerboard pattern, alternating Fuel Rods with coolant or moderator blocks. This keeps every rod surrounded by cooling and packs in the most rods without overheating. You can view whether any block works as a coolant in-game by pressing F3 and H together to enable advanced tooltips.

Active Cooling with Fluids

Active cooling requires a Reinforced reactor fitted with Fluid Ports, one pumping coolant in and one pushing vapor out. Instead of making energy directly, the reactor superheats a coolant such as Water into Steam, which you then feed into a turbine. This two-machine loop produces far more total energy than passive cooling ever could.

To run one, add a Reactor Active Fluid Port for Water input and another for Steam output, plus a Fuel Injection Port if you are using a liquid fuel. The Steam travels to a turbine, and the condensed Water it returns can be piped straight back into the reactor. This closed loop means your only ongoing cost is fuel.

Best Liquid Coolants

Water is the starter coolant, but crafted liquid coolants perform far better as reactors scale up. Redfrigium and Tangerium are among the strongest liquid coolants in the mod, and both are produced in the Fluidizer. Tangerium comes from combining 1 Anglesite Crystal with 4 Ender Pearls, while Redfrigium is mixed from Cryomisi and Tangerium together.

Cryomisi, an intermediate coolant, is made by mixing 1 Redstone with 1 Snow Block in the Fluidizer. When you use a liquid coolant, place it in every interior air gap for the best efficiency, since simply dropping a bucket at the top and letting it flow down works poorly. Many solid metal blocks also serve as strong block-form coolants if you prefer not to deal with fluids.

The Fuel Cycle: Reprocessor and Fluidizer

Extreme Reactors hides a deep fuel-upgrade chain behind two more multiblock machines. The Reprocessor turns waste and materials into stronger fuels and coil metals, while the Fluidizer converts solids into fluids and mixes new liquids. The chain looks daunting, but you only need to run it once to stockpile the endgame blocks.

The Reprocessor

The Reprocessor is a fixed 3x3x7 machine whose Casing is crafted from 4 Cyanite Ingots, 4 Iron Ingots, and 1 Water Bucket. It combines a solid waste material with a fluid to output a higher-tier product, and it needs a Controller, Waste Injector, Fluid Injector, Output Port, Power Port, and a Collector on its bottom face. Its first job is turning your Cyanite waste into Blutonium, a much stronger reactor fuel.

That first recipe reprocesses 2 Cyanite Ingots with 1000 units of Water into 1 Blutonium Ingot. Swapping your reactor over to Blutonium noticeably raises power output compared to plain Yellorium, giving your original fuel a valuable second life. From here, the Reprocessor keeps climbing the material ladder into the specialized coil metals.

The Fluidizer

The Fluidizer handles the fluid side of the cycle, built much like a reactor with a hollow interior, a Controller, injectors, a Power Port, and an Output Port. With Solid Injectors it fuses two solids into a fluid, and with Fluid Injectors it mixes two fluids together. This is where you liquefy materials so the Reprocessor can use them as its fluid ingredient.

The Fluidizer also produces Verderium, the mod’s liquid reactor fuel, by combining 2 Yellorium Ingots with 1 Blutonium Ingot into 2000 units of Verderium. Verderium is injected through a reactor’s Fuel Injection Port and is a common feed for large actively cooled reactors. The same machine makes your liquid coolants, tying the whole system together.

Coil Material Progression

The real payoff of the fuel cycle is a chain of coil metals for turbines, each reprocessed from the one before it. Ludicrite comes from Blutonium, Ridiculite from Ludicrite, Inanite from Ridiculite, and Insanite is the top-tier coil material. Each step up produces dramatically more energy when used as a turbine induction coil.

The fluids in that chain come from reactor byproducts you fluidize along the way, such as Magentite from burning Blutonium and Rossinite from burning Verderium. It is a genuine web of dependencies, which is why players recommend making a flowchart the first time through. Since these blocks are only used as coils, a single production run gives you enough to line every turbine you will ever build.

Turbines: Turning Steam into Power

Turbines are the second half of an actively cooled setup, converting the Steam from your reactor into Forge Energy. A spinning rotor drives metal induction coils, and the quality of those coils determines how much energy you extract. This is where the mod’s biggest numbers come from.

Building a Turbine

A turbine is a tall hollow multiblock with a Rotor Bearing on one interior face and a Rotor Shaft running the full length out of it. You add Rotor Blades along the shaft near the bearing, then rings of coil blocks around the bare shaft farther out. A Basic turbine tops out at 5x5x10, while Reinforced turbines reach up to 32 blocks in each dimension by default.

The turbine also needs a Controller, a Power Tap for output, and two Fluid Ports, one taking Steam in and one returning condensed Water out. Turbine Blades and Casings are built with Cyanite, so your reactor waste feeds directly into building the turbine. More blades let the turbine process more Steam, so scale blade count to how much Steam your reactor produces.

Rotor Speed and Flow Rate

Rotors perform best at either 900 or 1800 RPM, and the Controller’s Flow Rate Governor is how you dial in that speed. Raising the flow rate lets more Steam in and spins the rotor faster, while lowering it slows the rotor down. Nudge the flow rate until the RPM settles as close to 1800 as you can get it.

Induction Coils

Induction coils are rings of metal blocks around the shaft that extract energy from the spinning rotor. Engaging the coils draws power but adds drag that slows the rotor, while disengaging them lets it spin freely. Better coil materials pull far more energy for the same rotor speed, which is exactly what the Ludicrite-to-Insanite chain is for.

Swapping a turbine’s coils from a lower tier to a higher one, with nothing else changed, can multiply its output many times over. This is why the fuel cycle is worth the trouble, since the coil metals are the single largest power upgrade in the mod. Line two or more rings of the best coil you have around a well-tuned rotor for the strongest results.

The Energizer: Storing Your Power

The Energizer is the mod’s dedicated energy storage multiblock, essentially a giant battery you build to hold your generated power. It starts at a minimum of 3x3x3 and grows in capacity as you make it larger. Like the other machines, it needs a Controller plus Power Ports set to input and output.

The interior must be filled completely with Energy Cells, which are the expensive part of the build. Each Energy Cell is crafted from an Energy Core, 2 Gold Blocks, 2 Iron Blocks, and 4 Benitoite Crystals. The Energy Core in turn combines 4 Anglesite Crystals, 1 Magentite Block, 2 Redstone Blocks, and 2 Eyes of Ender.

This is where those Nether and End ores finally pay off, since Benitoite and Anglesite both feed the storage chain. A modest Energizer already holds a staggering amount of energy, so most players build one only when a single reactor’s internal buffer stops being enough. It is a late convenience rather than an early necessity.

Ports and Automation

The various ports on a reactor or turbine are how you get materials and power in and out, and how you automate the whole thing. Learning the difference between the port types early prevents a lot of head-scratching. These parts are what turn a manual generator into a hands-off power plant.

Active vs Passive Power Taps

An Active Power Tap always pushes energy out into whatever is connected, needing no extra setup, and it is the recommended choice for most players. A Passive Power Tap does nothing on its own and only releases energy when another mod’s cable actively pulls from it. The passive version is cheaper to craft but requires you to configure the pulling pipe yourself.

Access Ports and the Redstone Port

Solid Access Ports toggle between inlet mode for inserting fuel and outlet mode for ejecting waste, switchable in the port’s screen or with the Extreme Wrench. The Redstone Port is the automation workhorse, reading reactor values like energy stored or Casing Heat and emitting or receiving redstone signals. A common setup pairs two ports so the reactor shuts itself off once the buffer passes a threshold like 95%.

Charging and Computer Ports

The Charging Port lets you charge energy-using items directly from a reactor or turbine by dropping them into its slot. The Reinforced tier also adds a Computer Port for integration with computer mods, allowing scripted control of a reactor’s behavior. These optional ports are the polish that turns a working reactor into a fully managed system.

Tips for Success

Start small and cheap. Players consistently find the first reactor overwhelming because of how many parts it has, so build a tiny 3x3x3 Basic reactor first. Everything you learn on that cube, from the Controller screen to Control Rod insertion, applies identically to a giant Reinforced build later. Treat your first reactor as a training exercise rather than your final power plant.

Remember that insertion is backwards. The most common early mistake is misreading Control Rods, since 0% insertion is maximum burn and 100% is minimum. If your reactor is chewing through Yellorium far too fast, raise the insertion percentage to throttle it down. If it feels weak, lower the insertion to let it run hotter.

Automate the shutoff. Because a reactor burns fuel even at a full buffer, a pair of Redstone Ports set to switch it off near full storage saves a huge amount of Yellorium over time. This single bit of redstone is the difference between a wasteful reactor and an efficient one. Set it up as soon as you have spare Casings.

Hoard your Cyanite. That waste product is not junk, and players who toss it end up regretting it once they reach reinforced parts and turbines. Cyanite feeds the Reprocessor, turbine Casings, and the coil chain, so a full chest of it smooths the entire mid game. Set an outlet Access Port to a dedicated waste chest from day one.

Use the checkerboard and better coolants. Alternating Fuel Rods with coolant in a checkerboard keeps every rod cool and maximizes rod count, and upgrading from Water to Redfrigium or Tangerium makes a large difference as reactors grow. When adding liquid coolant, fill every interior air gap rather than letting a single bucket flow down. Efficiency scales with how carefully you lay out the interior.

Frequently Asked Questions