Nuclear Power — Complete Setup Guide

I put off nuclear for three playthroughs. Solar seemed simpler, steam seemed cheaper. Then I built my first 2×2 reactor and watched 480 MW light up from a single fuel cell. I haven't looked back.

Nuclear isn't the cheapest option, but it's the best middle ground for a mid-to-late game factory:

• A 2×2 reactor produces 480 MW in the space of 8 solar panels
• One uranium patch lasts hundreds of real-time hours
• Nuclear UPS impact is far lower than 10,000 solar panels and accumulators
• Scales from 40 MW (single reactor) to multi-GW tileable designs

The nuclear fuel chain has several stages:

10xUranium

→

0.7%Uranium 235

10xUranium

→

99.3%Uranium 238

Each centrifuge processes 10 uranium ore per cycle (12 seconds without modules). At 0.7% enrichment, you'll get about 1 U-235 for every 143 ore processed.

Fuel cells combine the two isotopes:

1xUranium 235

+

19xUranium 238

→

10xUranium fuel cell

Each fuel cell burns for 200 seconds in a reactor. A single reactor uses 0.005 fuel cells per second — about 18 cells per hour.

The 2×2 layout is the gold standard for nuclear power. Four reactors arranged in a square, each touching two neighbors.

Neighbor bonus: Each adjacent reactor adds +100% heat output. A 2×2 gives:

• Corner reactors: +100% (1 neighbor) = 80 MW each
• Center reactors: +300% (2 neighbors) = 160 MW each
• Total: 480 MW from 4 reactors at 72 fuel cells/hour

Component counts for 2×2:

Heat moves through heat pipes similarly to fluids but with two key rules:

1. Max distance: Heat travels about 16 tiles from a reactor before significant dropoff
2. Max load: Each heat pipe segment can carry heat for up to 4 heat exchangers

Design rules:

• Keep heat pipes within 20 tiles of the reactor
• Run double heat pipes for 2+ reactor wide setups
• Place heat exchangers on both sides of the heat pipe
• More heat pipes = more capacity, not more range

For a 2×2 reactor, run a thick heat pipe line (3-5 parallel pipes) from the reactor block to the exchanger array.

The neighbor bonus makes larger setups wildly more efficient. A 2×4 produces 7× the power of four 1×1 reactors but uses the same fuel.

Without Kovarex, you need centrifuge processing to get U-235 — and the 0.7% rate makes expansion painful.

40xUranium 235

+

5xUranium 238

→

41xUranium 235

What this does: Each cycle consumes 5 U-238 and produces 1 net U-235. After bootstrapping with 40 U-235, Kovarex runs indefinitely, producing enough fuel for any size reactor.

Bootstrapping: You need 40 U-235 to start Kovarex. That's about 6,000 uranium ore without productivity modules. Stockpile U-235 while running the reactor manually or supplement with solar/steam.

Each steam tank holds 25,000 units of steam (2.425 GJ). With 200-second fuel burn cycles:

• Buffer size: 20 tanks store enough steam for ~5 minutes at 480 MW full load
• Circuit control: Connect a tank to a decider combinator. Insert fuel when steam < 10,000. This reduces fuel consumption by 50-80%
• Turbine layout: One steam turbine consumes 60 units/s. At max output, 84 turbines consume 5,040 steam/s. 20 tanks provide about 100 seconds of buffer

Not enough water. One offshore pump feeds 12 heat exchangers. A 2×2 needs 4 dedicated offshore pumps. Running multiple exchangers off one pump causes steam starvation.

Heat pipe too long. Past ~16 tiles from the reactor, heat transfer drops significantly. For 2×2 layouts, run heat pipes in parallel (3-5 width) rather than single-file.

Overproducing fuel cells. A 2×2 burns 72 cells per hour. One assembler with speed modules running for 5 minutes produces enough fuel cells for hours of operation. Don't build four assemblers.

Ignoring neighbor bonus. A 2×2 using 4 cells/cycle produces 480 MW. Four standalone reactors produce 160 MW with the same fuel. Touching reactors matters.

For larger bases, use tileable 2×N reactor rows:

• Each additional pair of reactors adds 160 MW
• A 2×8 setup produces 2,240 MW — enough for a full megabase
• Use a dedicated train station for uranium ore delivery
• Multiple centrifuges with Kovarex produce enough U-235 for any scale

Nuclear power is the most space-efficient power source in Factorio. A 2×2 reactor at 480 MW is the ideal first build — big enough to power a megabase but simple enough to build in an afternoon.

Numbers to remember:

• 2×2 = 480 MW, 48 heat exchangers, 84 turbines, 4 pumps
• 72 fuel cells per hour until Kovarex, then effectively infinite
• Heat pipes max out at ~16 tiles — plan your exchanger placement
• 20 steam tanks + circuit control = 80% fuel savings

Related: Main Bus Guide — routing all that nuclear power through your base, Oil Processing Guide — fuel chain before nuclear.