Factorio Nuclear Reactors
Factorio Nuclear Reactors are a new power source in Factorio 0.15. For those that have played Factorio, late game setups have included either thousands of steam engines or tens of thousands of solar panels. This ends up taking both significant production and significant game world space. While mass production is part of the game, the space taken by the power system often dwarfs by orders of magnitude the other game activity.
With 2 offshore pumps,20 steam boilers, and 40 steam engines, and a big belt of coal you can get neigh 60 megawatts. As you can see on the left, here, It’s a pretty large setup. It’s enough, generally, for the first stage of the game… upto making all the potions, but it starts getting dicey at that point. You certainly want to also be using coal for smelting as this will not provide that level of power.
Factorio Max 2 Pump Steam Setup
A similar setup with Solar Panels would already be several times larger (and would consume batteries and steel to a much greater extent).
My simple Factorio Nuclear Reactor setup (shown above) provides 40 MW with one Reactor, 160 MW with two, 280 MW with three and 480 MW with four Reactors configured. I recommend shooting for the two reactor setup to start because the bonuses are just so high.
But… I’m jumping ahead of myself. You need to get there from the start of your game. You can’t even mine Uranium until you have a source of Sulfuric Acid.
In the last few attempts at 0.15 Factorio, I’ve found that one trick is to start mining uranium as soon as you have Sulphuric Acid. There is often a patch that will be covered by one or two miners near your spawn and I run that into a chest.
Factorio Uranium Mining Setup
When you get Factorio Nuclear, you’ll have several thousand uranium ore saved up. Factorio Nuclear takes an enormous amount of research with all five non-combat potions. As soon as I get Factorio Nuclear, I make six centrifuges. Make sure you have concrete early on. Each Centrifuge takes 100 cement.
DO NOT setup your fuel rod factory yet. If you did this as soon as possible (I only research logistic chests first), it will be awhile before you are going to deploy your first reactor. For the Koravex process, you’ll want to have 40 U235 on hand. When you get this, put it into your inventory so that it is not used. U235 in excess of 40 can then be used in a fuel rod factory.
Factorio Big Uranium Mining Setup
If you have another, larger patch of uranium to mine (several million in yield) and if you can setup a train with a single tank car (or a very long pipeline) to service it, these six Centrifuges will be enough to run at least 2 reactors until that ore patch runs out. With two reactors you need one fuel rod every 100 seconds and every U235 generates 10 fuel rods. So you need one U235 every 1000 seconds which is roughly 4 per hour. This setup does make more than that from experience.
Looking at my larger mining setup, you can see two trains. With Factorio 0.15, you have Fluid wagons available. I only put one fluid wagon on this train as it has the capacity of about 2 storage tanks and it’s plenty. Any more would even more seriously stress your system. Over the lifetime of this ore patch, I think the train made 3 or 4 trips. Similarly two cargo wagons is more than plenty to keep the 6 centrifuges busy.
It’s also worth noting that this patch will be exhausted before 25 hours of gameplay and it only produced about 100 total U235 by the straight centrifuge method. This is why the Kovarex process is so important. The other result of this mining is about 14k (remaining) U238, and for every 5 of these, the Kovarex process will produce another U235.
Now for your 40 U235 (that you siphoned off into your inventory as soon as you had them, above). After your reactor has been running for some time, and after you’ve siphoned off your 40 U235, but before your Uranium ore patch runs out (by a wide margin … several game hours), research the Kovarex process. The Kovarex process is just as expensive as Factorio Nuclear to begin with, but the payoff here is huge. The Kovarex process is massively more important than fuel recycling. The Kovarex process in this setup will produce 1 U235 every 25 seconds. Fuel recycling will only net you 3 extra U238 every reactor cycle.
Factorio Nuclear Kovarex Setup
In the image to the left, both centrifuges are set to Korvax. The top chest is requesting 200 U238. The Kovarex proces requires 40 U235 and 5 U238 and produces 40 U235 in 50 seconds.
I usually set up the first centrifuge’s inserters and leave the 2nd centrifuge idle. The middle inserter is set to move from the bottom chest to the top if the top has less than 40 U235 in it. The insert below that moves from the bottom chest to the provider chest when there are more than 39 U235 in the top chest. Like all buildings, the centrifuges will take up to double their inputs. When the first is getting to about 60 (it will top out at 80-ish) then I put the inserters pointing at the 2nd Centrifuge.
200 U235 is an embarrassment of riches, but between the two of them, they will consume 10 U238 and produce 2 U235 every 50 seconds. Since each U235 produces 10 fuel rods, This will power upto 80 Factorio Reactors. You can also let your Uranium ore patch run out as it will now be a long time before you require more. You probably don’t need two centrifuges here (unless you have more than 40 reactors running), but it’s compact, cheap and pleasantly symmetrical.
Factorio Nuclear Reactors
Factorio Nuclear Reactors
So you’ve started uranium mining. Awhile ago you got the Factorio Nuclear technology and you’ve refined enough uranium to start. How much? If you can refine an extra 10 U235 above the 40 required for Koravex, that will be 100 fuel rods. Enough for 1 2/3 hours of two reactors operating. A this point in your game, you can probably use the 160 odd megawatts that this will pump out for you. If you have six centrifuges going and filled with incoming ore, then you should be able to operate two reactors while you wait to research and implement Koravex.
Now… below this paragraph, I’m going to insert a large picture that is the setup of the Factorio Nuclear Reactors in my current game. I started operation with 2 reactors and 16 heat exchangers attached to two offshore pumps. Each offshore pump can handle up to 10 heat exchangers. As I added the third reactor, I added 2 heat exchangers to each of the two groups to make 10 and added one extra group of 10. That is what you see.
Factorio Nuclear Setup
If you’re sharp-eyed, you notice that I have storage tanks in the bottom row. They offset the turbines by two squares, but at 3 squares wide, they fit right in. We’ll discuss those in a second.
You’ve probably already read about the Factorio Nuclear Reactor adjacency bonus. Simply put, each reactor squarely lined up with another fueled and active reactor produces a bonus reactor. One reactor by itself is one reactor: 40 MW. Two reactors side-by-side are equivalent to four. That is: each reactor has one adjacent reactor, so each reactor is worth 2 reactors… so 160MW. Above, of the three reactors, one is adjacent to 2, so it’s worth 3 and the other 2 reactors are worth 2 each for a total of 7 or 280 MW. For four reactors in a square (my next upgrade), each reactor has two adjacent (diagonals do not count), so each reactor is worth 3 for a total of 12 or 480 MW.
When I upgrade to a fourth Factorio Nuclear Reactor, I will top that up with 2 more groups of 10 turbines and 2 more offsore pumps.
“Ten?” You Say…
“Ten?” you say, “isn’t that too many?” Yes, but there is a reason. You can store hot steam. A standard storage tank stores 25k steam. The standard turbines will run at 5.8 megawatts while the heat exchangers will only provide 10 megawatts (5 for each turbine).
When your power system is running at less than full tilt, it can fill up the storage tanks. The extra 1.6 megawatts the two turbines on each heat exchanger can handle means 16 extra megawatts per group of 10 for as long as 20 minutes. Not a bad storage system… or thought of another way: not a bad emergency power system!
Lastly, it’s a good idea to cable the storage tanks together and put an alarm on them. It’s good to know when you need more power and you’ll know when the amount of stored steam drops. Ten tanks store 250k. I alarm at 200k — so 5 minutes into my 20 minute overage.
What Does Running Out of Power Look Like?
Factorio Nuclear Reactors heat up to 1000°C. In Factorio (at least for now), they don’t explode, but at 1000°C, you’re probably wasting some power. Wasting anything seems antithetical to most types of Factorio players, but you have few options with Factorio Nuclear Power. At the moment, steam turbines have the same power priority as steam engines, so the only complementary power source is Solar, but even with Solar power, your accumulators are going to make it difficult, if not impossible, to completely effectively run only a base load on Nuclear.
Anywhere above 500°C, heat exchangers will be able produce their 10MW of power. Like the steam engines and boiler, when power is not required, the turbines will use less steam and as steam backs up, the heat exchangers will consume less heat. Unlike the coal-steam system, however, the reactors consume a constant amount of fuel.
Two things come out of this. One is that the reactor and heatpipe system have a “heat capacity.” This is what governs the time it takes for the reactor system to “start up” and this contains some amount of power as heat over 500°C. The other is that monitoring the temperature of the reactor(s) will give you some idea of your power situation. A falling temperature means you’re dipping into your “emergency” power and a rising temperature means you’re using less power than you’re creating.
If your reactor (or, more likely, your furthest away heat exchangers) fall below 500°C, they will stop producing steam. In turn your turbines will spin down. Since they aren’t using power, they should shortly recover when heat from the reactor puts them back over 500°C.
If you took the last section’s advice and used storage tanks, as the turbines stopped, the volume in the tanks were decrease. This can be routed to a map-wide alarm. The advantage here is that you have roughly 15 minutes of peak production to survive that biter invasion and solve the power problem.
The Grand Table of Factorio Nuclear Reactor Numbers
Keep in mind that I slightly over provision each level to keep things symmetric. These are my build numbers:
| Reactors | Effective Reactors | Reactor Power | Emergency Power | Heat Echangers | Turbines | Water Pumps |
| 1 | 1 | 40 | 46.4 | 4 | 8 | 1 |
| 2 | 4 | 160 | 185.6 | 16 | 32 | 2 |
| 3 | 7 | 280 | 348.0 | 30 | 60 | 3 |
| 4 | 12 | 480 | 580.0 | 50 | 100 | 5 |
The optimal number of heat exchangers for 3 reactors is 28 and for 4 reactors 48. I round up to 30 and 50. It looks nice and it has slightly more emergency power, too. I haven’t created a need for more than 4 Factorio Nuclear Reactors yet. If I did, I’d be strongly tempted to create a second separate installation. This has more redundancy and resiliency in the case of attack. Combined, that’s almost a gigawatt of power.
Maybe the grand take-away is that roughly 4 heat exchangers per effective reactor are “correct.” Offshore pumps group those heat exchangers into roughly groups of 10. Weather you take the extra 0.8 megawatts per turbine as extra emergency power based on system heat soak or you have storage tanks for your steam, I think that emergency power is the better use. Those who try to find optimal ratios that use all of this amount are somewhat mistaken. Turbines are cheap, after all.
Happy Factorioing.
Thank you, I just started this game 2 months ago. Fired a rocket. But there is so much more. Trying to figure out the nuclear now and I enjoyed your writing , think it will help understand it a little bit better. Please keep up the good work
Thanks
Rusty