Captain of Industry – Fast Breeder Reactors and You!

How to use the fast breeder reactor.

The Basics

A fast breeder reactor is the endgame of nuclear power. It can use liquefied molten uranium core fuel and produces only fission products, which given time can decay into harmless materials and be recycled. Core fuel is expensive to produce, but the reactor itself can be used to enrich cheap and easy blanket fuel into more core fuel, meaning that once the reactor has been filled with core fuel once you should never need to make more provided you keep it supplied with blanket fuel and reprocess everything correctly.

“Blanket fuel” and “Core Fuel” are the inputs. “Depleted Core Fuel” and “Enriched Blanket Fuel” the outputs. They are all molten liquids, which can be carried with pipes but cannot be stored in storages or carried by trucks, so all the loops for processing must be built close to each other. Keeping the loop going requires a constant input of steel, acid, salt and molten glass, as well as the requisite supply of fresh water and steam reprocessing, as well as a block of steam turbines to make the power. The reactor can self-regulate if it is provided with processing power.

Establishing the Recycling Loops

There are two output loops that need to be handled. Depleted core fuel is handled in a nuclear reprocessing plant. It requires acid and steel, as well as an input of molten glass. Using a whole blast furnace just for this is a bit overkill, but since molten transports have to be flat the only other option is relocating your glass production to near the reactor. You only need one of these plants, it has the capacity to handle two reactors worth of output and then a bit more, but you’ll need a second if you want to reprocess old depleted fuel or MOX casks into blanket fuel, that’ll come later.

For each ten units of depleted core fuel, the reprocessor outputs eight units of core fuel and two units of fission products. So you get four units back for consuming five units of core fuel, you only need to replace one out of five.

The second loop is done in an enrichment plant. It takes in enriched blanket fuel in 15 unit batches and outputs three core fuel and 12 blanket fuel. There’s no external ingredients required for this.

The way the ratios work out, recycling the two outputs gives back the same amount of core fuel you started with, consumes some blanket fuel and produces some fission products. So once you have created the first small batch of core fuel, which requires a lot of processing steps, you can use the reactor itself to make all you need from the much easier to make blanket fuel, most of the complex steps in the nuclear chain become unneeded unless you want to start up another reactor.

Creating the Starter Core Fuel

The reactor produces its own core fuel but you will need to make a bit to get started. It is produced in a chemical plant from 20% enriched uranium and salt. You make 20% uranium by processing 4% uranium in an enrichment plant with more Hydrogen Fluoride, you can use a loop back and sorter to accomplish this.

Use a pipe balancer to make sure that the core fuel coming back from the two recycling loops is given priority over new core fuel otherwise the loop might back up.

Once the system is running you can pause this plant but be ready to use it to start up again. The only reason you’d need to is if you ran out of blanket fuel, this would cause the reactor to consume its core fuel and stop.

Creating Input Blanket Fuel

Blanket fuel recycles through the loops but it diminishes as it’s converted to core fuel, so you’ll need a constant input of new blanket fuel. There are two sources, each of which has two possible recipies.

Using a Nuclear Reprocessing Facilty, you can make blanket fuel from either spent fuel or spent MOX, giving you a way to reuse the wastes from your older reactors. These can be belted in from the waste facilities where they are stored. There’s no chance of backup as they’re used in the same amounts, so feel free to share a belt for these. As before the byproduct is fission products, and you’ll need inputs of salt, acid and molten glass (but surprisingly not steel, I guess since the waste comes in as a barrel the plant is just reusing the same barrel for the fission products). You will want to start out this way to get rid of your hazardous waste. It makes three a minute.

The second way is in a chemical plant, in which you combine either depleted uranium (which you probably have a lot of sitting around) or new yellowcake. A Chemical Plant II makes three a minute with no waste products, only requiring a supply of salt (also three a minute).

All blanket fuel formulas create three per minute, which is enough to keep up with a fully-loaded recycling loop and replace all the blanket fuel it consumes. As before use pipe balancers to make sure the recycled blanket fuel has priority over the new or else the loop could back up.

One reactor won’t fully load the recycling loops, so only one of these methods is needed at a time, but I recommend first using up your hazardous spent fuel and MOX first to free up the storage, then switching to your depleted uranium stockpile and then back to yellowcake. Using up the waste you generated on the earlier reactors might take you a century or more.

Superheated Steam – Power Generation and More

The FBR generates superheated steam, which has double the energy content of regular high steam.

To optimally use the steam, you should build a shaft with two super turbines, two high-pressure II, two low-pressure II, and four large generators all plumbed in series. That will consume 96 superheated steam and give back 96 depleted steam, and completely occupy the 72 MW torque limit of a single shaft, which yields 60 MW of electricity. Four such shafts deliver 240 MW. One large cooling tower can recover the steam from one shaft, so you’ll want four of those as well.

If you recycle all the steam you’ll need 24 new water per level per minute to make it up as the cooling tower can only recover 75%, that is 96 at full speed. If you send the depleted steam to a bank of vacuum desalinators instead of cooling towers you can consume all the steam of a full output power plant and get a net gain of 37.5% extra fresh water, but that will require 16 desalinators, using 64 workers and 6.4 MW of power and a lot of space. If instead you feed 12 superheated steam to two desalinators you’ll net all the water you need to make up for the loss plus a surplus of 36 per minute, using only 800 KW and 8 workers. Keep in mind that if you use all your steam for power you’ll have none for desalination, so your reactor could run dry if you’re at the redline unless you use a pipe balancer to ensure that the desalination gets priority. Most of the groundwater aquifers can support 96 water a minute (that’s two pumps) sustainably if you don’t use it for anything else, more than that they’ll deplete over time.

The hydrogen reformer also includes a new method of splitting water using superheated steam to make hydrogen and oxygen that uses less energy than electrolysis. Tapping into your superheated steam for these processes will mean you can’t fully use all of it for power generation. It’s far more flexible to use power to make superheated steam in electric boilers, but that incurs a small loss.

Also, superheated steam isn’t compatible with the oil refining process, so if you had been tapping your old reactor for your refinery’s steam you’ll need to either tap in after the super pressure turbine or use an electric boiler instead.

Helena Stamatina
About Helena Stamatina 3020 Articles
I love two things in life, games and sports. Although sports were my earliest interest, it was video games that got me completely addicted (in a good way). My first game was Crash Bandicoot (PS1) from the legendary studio Naughty Dog back in 1996. I turned my passion for gaming into a job back in 2019 when I transformed my geek blog (Re-actor) into the gaming website it is today.


  1. The simpler you keep things, the less chance of failure.
    Firstly, ignore depleted uranium. Just dump it, use it to expand your island. It isnt even radioactive.
    Second, dont try messing around with diverting superheated steam. Just build 4 racks, each of 2 SH turbs, 2 HP II turbs, 2 LP II turbs, and 4 large generators. Pipe the waste to 4 large towers, send the water back to input (prioritising over new water using a balancer). If you need SH steam to run desalinators to provide feedwater, use electric boilers. A boiler eats 9.6MW and can run two thermal desalinators (144 H2O/min). The reactor generates 288MW. Power is no longer an issue when this thing is running.
    Thirdly, the production. The ‘primer’ plant needs one CP2 and one enrichment plant, you can draw the inputs from your existing nuclear plant 2 (HF gas and enriched uranium 4), a bit of salt from evaporating seawater/brine (I always build my nuclear setups near my gold refineries, so have plenty of brine handy). The ‘raw’ plant needs only a CP2 set to yellowcake (from existing nuke 2 setup) and salt (as above) to blanket feul. You should also build a reprocessor next to your nuke plant 2 reprocessor and use it to turn waste mox into blanket feul, feed both blanket feuls into the breeder reactor. The ‘recycling’ part consists of one enricher (enriched blanket feul from reactor to blanket+core feul), and one reprocessor (spent core feul to core feul). You probably need another blast furnace for molten glass if it is not built near your existing 2 reprocessors, but by this stage a blast furnace is nothing, and one small truck can easily feed it you dont need to worry about belts.
    4th, the setup. All 3 core feul producers can simply be linked up and fed into the reactor. You dont need to worry about priority, as you simply pause the enriched uranium 20 loop once the reactor is running. For the blanket feul inputs, run all 3 inputs to a balancer and prioritise the enricher input over the CP2 and the mox reprocessor – these 2 inputs can freely back up with no worries.

    If your nuke plant 2 setup has 2 uranium>yellowcake settling plants and yellowcake/reprocessed 1> enriched 4 enrichers, you can happily run both the nuke plant 2 and the breeder plant forever with this setup, all you need is uranium and a supply of rock, steel, coal, glassmix, acid, and seawater, and just dump the resulting slag and depleted uranium.

  2. Super nice guide thanks!

    May i ask if the Nuclear Power plant II is supposed to keep working once the FBR is already at its last stage (feeding itself)?

    Or are the old nuclear plants are supposed to be unbuilt?


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