Tutorial:Nuclear power

Nuclear power is a major new feature introduced in version 0.15. It requires higher level technology compared to either solar power or steam boiler power, but it offers very high power output in exchange. It's a great solution for middle- to end-game power generation and it works well in combination with other power generation techniques.

This guide is written for people who want to know exactly how nuclear power works, but don't necessarily want all the solutions. It focuses on what you should do and what you should know to get Nuclear up and running, but doesn't tell you what to do or exactly how to solve the problems.

First steps

Technology required: Nuclear power

You can mine uranium ore sooner, but you'll need the nuclear power technology to do anything useful with it.

Uranium ore

To start, you'll need uranium ore. It glows green, so you can't miss it. It tends to form smaller deposits, though, and you may have to search a while to find a good patch.

Like every other ore in the game, you can mine it with a Electric mining drill. Unlike every other ore, however, only the Electric mining drill wii do. You also need to supply sulfuric acid to the drill. The drills conduct excess acid through themselves, so a row of drills can be supplied by acid from a single side.

Mixed ores: If a mining drill covers even a single patch of uranium ore, it will require acid to run at all. The mine will produce mixed ore, as usual.

Ore processing

Once you've got raw uranium ore, you'll need to process it into uranium-235 and uranium-238. You do this in a centrifuge.

In an un-moduled centrifuge, you can process one ore every 13.3 seconds.

Centrifuges produce a combination of U-235 (the light green stuff) and U-238 (the dark green stuff). Every ten ore processed have a chance to become precisely one of these two products. Out of every 10k ore you process, you can expect to get, on average:

Count	Product
7	U-235
993	U-238

That means you can roughly expect to get a single U-235 in one out of every 143 ore. A centrifuge can then be expected to produce U-235 every 1904 seconds. Later on, this won't matter so much. However, when you first start out, this will be an important bottleneck.

Regarding averages: Be aware, random is random. These values are average values. Which means that over the long term, they work out to about these figures. In reality, you'll see long stretches with no U-235 and short stretches with lots of them. Eventually, it won't matter much. But early on, make sure your generation rate is sufficiently high, or you have a sufficient reserve, so you don't find yourself without power when you hit an unlucky stretch.

Fuel

Before you can burn it in a nuclear reactor, you need to create uranium fuel cells. You'll probably be using an assembling machine 2, so these will take 13.3 seconds to create as well. Which is fine because fuel cell creation will very rarely be the bottleneck.

You won't want to automatically convert all U-235 into fuel. Only convert what you need to fill your reactor. You're going to want a big fat stockpile of it when you research kovarex enrichment later on.

Fuel cells are produced in stacks of 10, and to produce one such stack you need 1 U-235, 19 U-238, and 10 iron plate.

Tip: It isn't a bad idea to use a chest and just stick a pile of iron in it rather than belting the iron in. A full chest of iron probably won't run out before you get bots and replace it with a requester.

Each fuel cell has a nominal energy value of 8 GJ, but it's possible to make them go even farther with reactor neighbor bonuses (more on that later).

Nuclear reactor

Once you've got fuel, you'll need to burn it in a nuclear reactor. This is the first step toward turning it into usable energy.

A reactor will produce exactly 40 MW of heat energy. Since a Watt is a Joule per second, this means the reactor will consume one fuel cell every 200 seconds.

Once expended, reactors will produce a "used up uranium fuel cell", which will need to be cleared. Initially, these will simply accumulate in a chest. Eventually, you can reprocess them into U-238.

Working backward: A reactor consumes a fuel cell every 200 seconds and each U-235 gives 10 fuel cells, so every U-235 provides 2000 seconds of reactor power. A centrifuge requires about 1904 seconds to produce a U-235, so you'll need about one processing centrifuges per reactor.

The reactor need input of water (using normal pipes), and produce heat (hot water) that need to be exported using heat pipe (unless a heat exchanger is attached to the reactor)

Heat exchanger

The heat exchanger takes heat and uses it to convert water into steam. It works much like the boiler, but instead of burning fuel, you need to connect it to a heat source. The heat input is marked by a flame when you're placing it.

For simple reactor designs, you can connect it directly to your reactor (which produces heat at points also marked with a flame).

Heat exchangers also require water input, in precisely the way boilers do. They can heat up to 103.09 units/second of water into 500°C steam.

Heat exchangers produce nothing when they are below 500°C. Since they only cool as a consequence of heating water, they will never cool to below that temperature once they've reached it.

Heat exchangers transfer 10 MW of power, so you'll need 4 exchangers to fully consume the power produced by a lone reactor. (Neighbor bonuses can increase this significantly. Again, discussed later.)

Heat pipes

More complex designs will require heat pipes. Heat pipes work much like regular pipes. Like regular pipes, they have limited throughput, which means that shorter pipes are better.

Connect heat pipes point to point, flame to flame, exactly as you would with water pipes. Heat pipes cannot go underground, so if water pipes need to cross them, the water pipe will need to go under. They don't block movement, though, so you can walk right over them.

Throughput on heat pipes is far more limited than regular pipes, in part because there is no analogous "Heat pump". Here are some rough limits on transfer distance:

Power	Distance
40 MW	~140
80 MW	~80
120 MW	~55
160 MW	~45

Past these distances, less than 100% of the power will be transferred. This is because at this distance, the maximum reactor temperature of 1000ºC is insufficient to heat the pipe to beyond 500ºC.

Heat pipe storage: Heat pipes can store quite a bit of heat as well. A single heat pipe can hold as much energy as a tank with 5.1k steam in it, which makes them even more space efficient than tanks for holding energy (though considerably more expensive). Be cautious, however, with transfer efficiencies. It's very easy to lose more power than you store with an inefficient design.

Steam turbine

These are the steam engine's beefy big brother. Using regular fluid pipes, you'll pipe the steam produced by heat exchangers into these turbines.

Perfect matches: The steam turbine is a perfect match for the heat exchanger. The steam engine is a perfect match for the boiler. Although it is possible to get energy out of mismatched systems, it's very wasteful and there's no real reason to do it.

Steam turbines consume up to 60 units of steam/second, so you need roughly two steam turbines for every heat exchanger. At large scales, however, you can use fewer turbines, since exchangers only produce 103.09 steam/second. You'll require a separate pump for every 20 turbines.

Simplest thing that works

At this point, you have all the parts to build your very first reactor:

• A few uranium miners, supplied with sulfuric acid
• 1 Centrifuge, processing uranium ore
• 1 Assembling machine, making uranium fuel cells
• 1 Nuclear reactor
• 4 Heat exchangers, supplied by a single off-shore pump
• 8 Steam turbines

And, of course, assorted, belts, inserters, filter inserters, and other tools for moving things around. This will produce a maximum of 40 MW of power.

Moving forward

Past your simplest reactor, there are some additional nuclear features of which you should be aware.

Neighbor bonus

This is a critical part of how nuclear designs scale, but it's not complicated. Simply put:

Every reactor gets +100% heating power for every active neighboring reactor.

Neighbors have to align completely on each side, so reactors will line up in a nice square grid. When they do, the neighbor bonus is activated. You can see the current bonus by hovering over an active reactor.

The bonus to heating power does not increase the fuel consumption. Rather, it simply increases the heat produced!

This, of course, means you'll need more heat exchangers and steam turbines to turn that heat into electricity.

Configuration	Reactors	Exchangers	Turbines	Power	Power per reactor
Single	1	4	7	40MW	40MW
2x1	2	16	28	160MW	80MW
2x2	4	48	83	480MW	120MW
2x3	6	80	138	800MW	133MW

How to count heat exchangers: Count the number of edges where reactors fully touch. Double that. Add the total number of reactors. Then multiply it all by 4. That's your count of Heat Exchangers. You'll need 1.718 turbines per exchanger (rounded up). Each exchanger will provide up to 10 MW of power.

Always on!

Unlike every other power generation technique, nuclear reactors DO NOT scale down power usage. Nuclear reactors will continue consuming one fuel cell every 200 seconds, regardless of the need.

As the reactor consumes its fuel, it heats up to a maximum temperature of 1000°C. At that point, additional fuel burned is simply wasted.

Turbines do scale their production (and steam consumption) to match demand. Likewise, exchangers won't consume heat if there's nowhere to put the steam.

Turbines and engines: Be aware that steam turbines and steam engines are both the same "class" of energy producer, so they'll need to be scaled all together. This means that in a complete energy system, your coal boilers may be running when the nuclear plant could fully cover the load. And, worse yet, the nuclear power is just being wasted!

Consider using accumulators, switches, and circuit logic to disable the coal boilers when nuclear systems can cover the demand.

The simplest solution to this problem is to just run the nuclear reactors part of the time. You can store steam in tanks. (And check out the "fill gauge"; the steam floats!) Since exchanges produce 120 steam/second and a tank holds 25k steam, a tank will keep 208 seconds worth of heat exchanger.

You can put a tank or two at the end of each heat exchanger and use circuit logic to only insert a fuel into the reactors when they get low. Make sure all exchangers are powered at the same time, or you won't get full neighbor bonuses. If you can't keep it from over-fueling, you can also add extra tanks to lengthen the cycle.

Enrichment

Required technology: Kovarex enrichment process

Kovarex Enrichment allows you to turn some U-238 into U-235, but it's slow and takes a lot of U-235 as catalyst.

Your first few patches of uranium ore will last you a reasonable length of time, but eventually you will start running out of ore and places to put extraneous U-238. Enrichment helps solve both problems.

The enrichment process takes about 67 seconds in an un-moduled centrifuge. It requires 40 U-235 (!) and 5 U-238 and makes 41 U-235 and 2 U-238. In effect, it turns 3 U-238 and turns it into 1 U-235; it just requires an extra 40 U-235 and 2 U-238 along for the ride to act as a catalyst.

All the things!: Before you enrich all the things!, be aware that you do need 19 U-238 for each fuel cell, as well as requiring it for uranium ammo you will want for storing inside biters and their nests. Circuit logic can help you put a limiter on large-scale enrichment operations.

One Centrifuge enriching uranium is sufficient to supply 29 reactors with fuel, assuming plenty of U-238.

Reprocessing fuel

Required technology: Nuclear fuel reprocessing

Reprocessing turns your spent fuel into U-238.

Eventually, you will run out of places to put spent fuel. You can use reprocessing to turn it back into U-238 to use for enrichment, fuel cells, or ammo. Of the 19 U-238 that go into each 10-pack of fuel cells, this returns 6. This significantly reduces the total ore requirement for nuclear fuel.

Weapons

Required technology: Uranium ammo / Atomic bomb

Better bullets / Bigger bombs

With the Nuclear Age comes nuclear weapons. Uranium ammunition is top-tier, especially when you load a tank with it. It mows down biter nests and clears swarms quite quickly. It uses U-238, so you've probably got plenty of it lying around.

On the other side, you can get atomic bombs, which are rockets (shot by a rocket launcher) that do incredible damage. Be aware, they can easily kill you if you fire them anywhere near you, and even at max range, it's advised that you run in the opposite direction. Rather than a single explosion, they do damage in an expanding ring, giving you time to escape. They require a lot of U-235 and blue chips, so they're an expensive weapon.

Version

This guide is compatible with Factorio 0.15.13. Newer versions may, and likely will, change many of the values and mechanics on which this guide depends.

License: CC BY-SA 4.0

As an exception to the above, any or all of this work or adaptations thereof may be used on the official Factorio Wiki.