Nuclear power was added to Factorio in version 0.15 that completely changed the overall strategy for the game. Nuclear power requires a higher level than most other power sources. It also provides a lot more energy than most other power sources. Creating this power source should be a long term goal of any player for the late-game. Here is a quick and easy way to get nuclear power.
Please be very careful when using these power sources. Nuclear reactors do not scale down like other power sources, it will continue to use up fuel so long as it is in use. This can turn them into very expensive energy wasters if you are not careful.
The fuel source
Before you can even think about using a nuclear reactor, you will need to find a way to power it first. The nuclear reactor requires uranium fuel cells to burn as a power source. To get the cells you will first need to mine uranium.
To mine uranium, you will need to research Uranium Processing first. The research needs a steady supply of at least one automation science pack, one logistics science pack, and one chemical science pack for 200 units. Once the research is completed you can create a centrifuge and process uranium into fuel. Next, you will need to mine the ore.
Uranium ore appears as bright green rock formations on the map. It can only be mined by feeding sulfuric acid to an electric mining drill. It takes roughly one unit of acid for each unit of ore mined. Uranium ore cannot be mined by hand.
Once you have some ore you will need to run it through a centrifuge. This will create uranium-235 and uranium-238. Uranium-238 can also be earned back later by using nuclear fuel reprocessing on used uranium fuel cells. Centrifuges can also be used to enrich uranium-235 using the Kovarex enrichment process to get more out of the resource.
Once the uranium has been processed you can turn it into uranium fuel cells. At any assembly machine, you can combine one uranium-235, 19 uranium-238, and 10 iron plates to create 10 fuel cells.
Once you have a steady supply of fuel cells you can start working on your reactor. You can build a reactor with 500 advanced circuits, 500 concrete, 500 copper plates, and 500 steel plates. The reactor alone doesn’t produce energy, instead it produces a large amount of heat. Connect it to a heat exchanger to create steam and generate power from there.
To restate an important point from earlier, reactors will not scale with the amount of power needed. This means it will always use the same amount of fuel regardless of if you need it or not. You should use these devices to power areas that need to remain in use permanently or for very long periods of time. Otherwise, the reactor will use up a fuel cell every 200 seconds and excess energy may be wasted.
To help prevent energy waste, excess power from a reactor can be stored in accumulators and extra steam can be stored in storage tanks. Both are relatively cheap to create and can help you push out more energy in a pinch.
After 200 seconds each fuel cell will be converted into a used up uranium fuel cell. These cells can be run through the centrifuge again to reclaim some of the components used to create them. This is especially useful for reclaiming uranium-235 which is much rarer and more valuable than uranium-238.