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The Nuclear Reactor is a multi-Block EU generator added by IndustrialCraft 2, with GregTech and Nuclear Control adding more functionality to it. It is possible to let the Nuclear Reactor generate Steam in the IC2 config file. The nuclear reactor is, especially when GregTech is enabled, not a very expensive machine, but it is tricky to operate and difficult to get significant amounts of EU out of it without exploding.

The Nuclear reactor consist of 2 parts:

The Reactor Chambers can be placed against the sides of the Nuclear Reactor to increase it's inventory space and thus increasing the power. This structure is often referred to as 'core' or 'reactor'. This is only a empty hull though, to render the reactor operational fuel and reactor components need to be placed inside it

Reactor Terminology

To understand how a reactor works and to know how to build one yourself, these terms are important to know

Reactor Tick

Not to be confused with Game Tick (1/20th of a second) Every second, the reactor updates it heat, cell durability and so forth. This update is called a Reactor Tick.


A Reactor produces 2 things, Heat and EU. This heat generation is what makes a reactor tricky. Every Fuel Rod generates heat, depending on type and location of other cells. Other components like Heat vents cool the reactor down again. If the heat value reaches a certain level, a reactor meltdown will happen. The ratio heat produced/heat dissipated determines the reactor type


Every tick, a fuel cell pulses, generating heat and energy. How many pulses it gives is determined by the amount of other fuel cells and reflectors directly around it.


A Cycle is the time it takes for a reactor to fully deplete it's cells. This varies per fuel type:

Fuel Cycle Duration

Uranium Cell
2 hours 47 minutes

Thorium Cell
6 hours 28 minutes

Plutonium Cell
5 hours 34 minutes

Reactor Design

There are a lot of different Reactor designs. These are dividable in 2 main different designs:


A reactor meant to generate EU, trying to be as efficient in it as possible related to time, components and fuel.


This reactor is meant to revitalize Depleted Isotope Cell. To do so the reactor tries to have an as high as possible heat level without exploding.

Power Generating Reactor

This reactor is meant to output as much EU as possible. It can be split up depending on it's heat generation:

Mark I

Mark I reactors generate no excess heat each reactor tick and thus are safe to use continuously for as long as you supply Uranium. Mark Is tend have a low efficiency, but that's the price of a completely safe reactor. Mark Is have two sub-classes: Mark I-I for design that do not rely in outside cooling in anyway and Mark I-O for those that do.

Mark II

Mark II designs produce a small amount of excess heat and will need to be given a cool down period eventually to prevent the hull reaching 85% maximum heat or melting component. A Mark II must complete at least one full cycle before encountering heat problems. The sub-class for Mark IIs denote how many cycles the design can run before reaching critical heat levels. For example Mark II-3 will need a cool down period after running 3 cycles in a row. Mark II s that can run 16 times or more get the special sub-class 'E' (Mark II-E) for almost being a Mark I.

Mark III

Mark III reactors tend to have an emphasis on efficiency at the cost of safety. Mark IIIs are unable to complete a full cycle without going into meltdown and thus need to be shutdown mid-cycle in order to deal with the high amount of excess heat. This can be done manually or by using Redstone. Mark IIIs have the additional condition that they must run at least 10% of a cycle (16 mins 40 secs) before reaching critical heat or losing any components.

Mark IV

Mark IVs still have to run at least 10% of a cycle, just like Mark IIIs. The difference being that Mark IVs are allowed to lose components to overheating, and that must be replaced before the reactor goes critical.

Mark V

Mark Vs are for those who want to squeeze every last scrap of EU from their uranium cells; they cannot run long without needing a cool down period. You'd better have great Redstone timer skills, or you'll never be able to turn your back on these things.

Breeder suffix

This suffix is for designs that also recharges isotope cells. Isotope cells charge up faster when the reactor runs hot, so heat management is important. There are three breeder types: Negative-Breeders slowly lose heat over time and will need heat to be added manually, or they can be left for a safe slow way to recharge isotopes. Equal-Breeders have exactly the same heat generation as they do cooling ability and usually only require a user to boost the reactor's heat level manually at the beginning. Positive-Breeders gain heat over time and will require more precise cool down management for the reactor to remain hot. Reactors whose sole purpose is to recharge cells may not even have a 'Mark' classification and are simply called Breeders instead, with the efficiency/SUC suffix added

To calculate the efficiency, take the number of uranium pulses a design makes per tick and divide it by the number of uranium cells it possesses. The number provided will show the efficiency rating a design has:

Number Rating
Exactly 1 EE
Greater than 1 but less than 2 ED
2 or greater but less than 3 EC
3 or greater but less than 4 EB
4 or greater EA

Breeding Reactor

A reactor purely meant to revitalize Depleted Isotope Cells.The time it takes to revitalize the cell is determined by the Heat. Most breeders have components to increase the maximum hull temperature and try to stay as low as possible below that. Reactor Ticks required to fully revitalize a Depleted Isotope Cell

Heat Ticks
0-2,999 40,000
3,000-5,999 20,000
6,000-8,999 10,000
9000+ 5,000

In order for a Breeder reactor to work the Depleted isotope needs to be placed next to a fuel cell. If more fuel cells are next to it, the Isotope cell charges faster. 2 fuel cells mean the Isotope cell charges twice as fast, 3 fuel cells and the isotope cell charges 3 times as fast. This also counts for double and quad cells, meaning a quad cell will charge 4 times as fast. The varying power Plutonium and Thorium Cells also work different. Plutonium cells are twice as powerful as uranium and thus charge twice as fast, and thorium cells thus twice as slow. The maximum speed is a Depleted Isotope Cell surrounded by 4 Quad Plutonium Cells, being 16 times as fast as the base speed in the table above. Isotope Cells also generate additional heat like normal cells would when placed next to fuel cells, but not EU. Re-enriched energy cells are stable and won't cause any extra heat production. For more detailed information about heat production, see the Heat Production.


Heat Vents

The Heat vent allows for fast cooling, releasing the heat into the air.

  • Heat Vent: The basic vent dissipates 6 heat from itself every second.
  • Reactor Heat vent: This vent moves 5 heat from the reactor vessel to itself and dissipates 5 heat every second. This has the advantage that it can function effectively anywhere in the reactor, not just next to the uranium cell.
  • Advanced Heat Vent: An improvement to a basic heat vent, this component dissipates 12 heat from itself.
  • Component Heat Vent:This vent dissipates 4 heat from each surrounding component.
  • Overclocked Heat Vent:This vent moves 36 heat from the reactor to itself and then dissipates 20 heat from itself. This will cause the component to overheat if steps are not taken to cool this component.
Name Heat dissipated Heat pulled from reactor Maximum heat

Heat Vent
6 0 1000

Reactor Heat Vent
5 5 1000

Advanced Heat Vent
12 0 1000

Overclocked Heat Vent
20 36 1000

Component Heat Vent
4* 0 1000
  • heat dissipated=Amount of heat released every tick.
  • Heat pulled From Reactor=Amount of heat pulled from the reactor. If this is 0 the heat vent can't actually cool down the reactor. In order for this heat vent to work it needs to be placed directy next to a cell. It will take ALL the cells heat. (if this is more that the dissipasion rate the heat vent will melt.
  • maximum heat = maximum heat it can store before smelting.

Heat Exchangers

Heat exchangers do not dissipate heat or actively draw heat from other objects, but they transfer the heat they get from other components like cells transfer around, making it easier for other components to dissipate. Heat exchangers work intelligently, seeking to make every component they interact be equally far from disintegration.

For instance, if a basic heat exchanger (which is destroyed at 2500 heat) was transferring heat from itself to the reactor (which usually is destroyed at 10 000 heat), and the heat exchanger contains 1,250 heat, it gives the reactor 1000 heat (10% of the reactor's capacity) and itself 250 heat (10% of its capacity).

There are four types.

  • Heat Exchanger: These will first exchange up to 12 heat with each surrounding component, and then up to 4 with the reactor itself.
  • Advanced Heat Exchanger: These transfer up to 24 heat with each surrounding component, and then up to 8 with the reactor.
  • Reactor Heat Exchanger: These transfer up to 72 heat with the reactor, but will not move heat to or from nearby components. These will usually be at the same percent capacity as the reactor, so they are useful as a kind of thermometer for your reactor.
  • Component Heat Exchanger]]: These transfer up to 36 heat with each adjacent component, but does not transfer any with the reactor itself.
Name Transfer to adjacent Transfer to core Maximum heat

Heat Exchanger
12 4 2500

Advanced Heat Exchanger
24 8 5000

Reactor Heat Exchanger
0 72 2500

Component Heat Exchanger
24 0 2500

Cooling Cells and Condensators

Cooling Cells and Condensators have the ability to absorb large amounts of heat, but cannot dissipate or transfer it by them selves. If Coolant Cells reaches their maximum heat, they melt, but Condensators way stay at 1 durability, but will be rendered useless. Heat Exchangers do work with Coolant Cells, making it possible to cool them down inside the reactor, allowing for a heat buffer that will automatically cool down once the cycle is finished, while Condensators can only be cooled down by adding either Redstone Dust or Lapis Lazuli. If GregTech is installed Cooling Cells can be cooled down outside the reactor as well inside a Vacuum Freezer. IC2 adds 3 types of coolant cells, and GregTech adds 6 more types. There are 2 types of Condensators added by Industrial Craft

Type Maximum heat before melting

10k Coolant Cell

30k Coolant Cell

60k Coolant Cell

60k Helium Coolant Cell

180k Helium Coolant Cell

360k Helium Coolant Cell

60k NaK Coolantcell

180k NaK Coolantcell

360k NaK Coolantcell


  • Condensators are recharged by crafting them with either Redstone Dust or Lapis Lazuli. The RHS can only be recharged with Redstone, each dust restoring 10,000 heat, and LZH can be recharged with both Redstone, 5,000 heat and Lapis Lazuli, 40,000 heat.
  • While the helium and NaK coolant cells shows the contained heat, water coolant cells and condensators always shows X/10000 durability. The durability here does not stand for heat, but is related to it. The amount of heat per durability varies per cell/condensator.:
Type Heat per durability

10k Coolant Cell

30k Coolant Cell

60k Coolant Cell



Reactor Plating

The only thing reactor platings do is increase the maximum hull temperature and decrease the explosion range in case of a meltdown. They come in 3 types:

Plating Maximum hull temperature Explosion range

Reactor Plating
+1000 -5%

Containment Reactor Plating
+500 -10%

Heat-Capacity Reactor Plating
+1700 -1%
  • if for more that 100% of Reactor Plating is installed, the reactor won't do any explosion damage.
  • though Reactor Plating can be stacked inside the reactor, they have to be unstacked in order to work, a stack of 64 reactor platings will work like a single one.


Though not something you would normally expect in a reactor, in breeding reactors you actually want to heat it up because it increases it's efficienty. That's where you need Heating Cells. Each Heating Cell heats up the surrounding components with 1 heat every tick per cell. They do not wear out. They heat up the components to 1000 heat per cell in the stack, so a stack of 2 cells heats up each surrounding component to maximum heat of 2000 with 2 heat per tick and so forth.

Neutron Reflectors

Fuel cells get a heat and energy output multiplier depending on the surrounding cells. More about this later in this article. Neutron Reflectors give a cell a multipier by bouncing back the pulse it gives. The different Neutron Reflector types only vary on durabilitly.

Type Pulses it can reflect

Neutron Reflector

Thick Neutron Reflector

Iridium Neutron Reflector


The amount of energy produced by a reactor depends on the fuel inside, but also on how this fuel is placed. Tif two cells are placed next to each other they increase each others strength. This is because of pulses. Every tick each cell gives off a pulse to adjacent cells, and each pulde received by a cell multiplies the total heat and energy production of it that tick.

Base values of the fuel types

Fuel Heat produced each tick energy produced each tick cycle duration pulses produced

Uranium Cell
4 5 EU 10,000 ticks 1

Dual Uranium Cell
24 20 EU 10,000 ticks 2

Quad Uranium Cell
96 60 EU 10,000 ticks 4

Depleted Isotope Cell
0 0 EU - 1

Plutonium Cell
8 10 EU 20,000 ticks 1

Double Plutonium Cell
48 40 EU 20,000 ticks 2

Quad Plutonium Cell
192 120 EU 20,000 ticks 4

Thorium Cell
0.8 1,25 EU 20,000 ticks 1

Double Thorium Cell
?? ?? EU 20,000 ticks 2

Quad Thorium Cell
?? ?? EU 20,000 ticks 4
  • Note that thorium cells have a strange way of operating, not being functional all the time, but giving off 4 heat and 5 EU every 5th tick. this is because the game can handle only whole numbers, so instead giving off .8 heat every second, which the game can't handle, it gives 4 heat off every 5 seconds, which can be handled by the game. This also counts for double and quad Thorium Cells.


For every pulse a cell receives it generates another time it's base EU production. For example, a single Uranium Cell generates 5 EU per tick. Placing another uranium cell next to it makes that both uranium cells receive one pulse every tick, making them generate 2 times their base generation every tick, 10 EU/t, or 20 EU/t in total. This makes the reactor twice as efficient as a reactor with the 2 cell separate. This is called Efficiency, the amount of pulses received by a cell per tick. The cells in the double uranium cell in the example setup have thus a efficiently of 2.

However, the heat production grows faster than the energy production. For example, a cell with an efficiency of 2 generates 2 times as much energy, but 3 times as much heat. The heat is calculated with the following formula:

Heat Generated=(0.5*Base Heat*(Efficiency+1))*Efficiency

Neutron Reflectors can be used to bounce the pulse back to the cell. A setup with a Cell next to a neutron Reflector gives the cell a efficiency of 2.

Heat Dangers

If a reactor generates more heat than it dissipates, this doesn't actually mean a meltdown, this only occurs if the hull temperature reaches 100%. The Hull's maximum temperature is 10,000 Heat, but this can be increased by adding Reactor Plating. You don't want to use the hull as buffer though, because nasty things start to happen at low temperatures already.

% of max hull heat Environmental effect
40% Flammable blocks within a 5x5x5 cube have a chance of burning.
50% Water blocks within a 5x5x5 cube (both sources and flowing) will have a chance of evaporating.
70% Entities within a 7x7x7 cube (instead of a 3x3x3 cube) will get hurt from the radiation exposure.
85% Blocks within a 5x5x5 cube have a chance of burning or turning into lava (flowing lava only, no source blocks).
100% What environment? That hole in the ground?

Meltdown Protection

Nuclear Control adds various blocks that can help you prevent a meltdown. The Thermal Monitor shows, when placed on the reactor, the hull temperature. It can also be set up to emit a redstone signal if the hull temperature reaches a certain level. Because the reactor reacts to redstone, it only operates when it receives one, this can be used to make an auto shutdown.

Blast Shield

It is a good idea to shield off your reactor with blocks with a High Blast resistance. Note that Obsidian has been nerfed by IC2, with it's blast resistance being changed to 40, compared to reinforced stone's blast resistance of 150. Fluids, such as water, also had their blast resistance nerfed by the IC2 team.

Good blocks to use as shielding are:

  • Reinforced Stone (and reinforced glass/doors). It's what it was designed for! A three thick layer of reinforced stone will protect against the explosion completely.
  • Hardened Glass A single layer of hardened glass will also completely protect against the explosion.

External links