So you want to be a Nuclear Engineer (Reactor Guide)
So, you want to be a Nuclear Engineer? You saw that big funny cube in the far off section of Engie and decided that today is the day you figure out its dirty little secrets?
Alright. I shall teach you.
The Nuclear Reactor is one of the more powerful engines available to Engineering (The second most, in fact, after the Supermatter). The manner of its operation is dead simple.
Boil Water.
Yep, just like in real life - the primary purpose of the Nuclear Reactor is to generate heat, heat which heats up water vapor, which then goes through a Turbine that turns said heat into electricity.
But how does it make heat?
Also simple - Neutron Radiation, but we'll get into that. First - Construction.
The Nuclear Reactor is a 7x7 Grid of "Slots", into which can be placed Rods. These Rods have various properties depending on the material from which they are made, and the type of rod they are.
Generally speaking ALL Rods have the following set of
Characteristics
Interactivity
The % Odds that a rod will "interact" with a Neutron that impacts it
Reflectivity
The & Odds that any interacting Neutron will be reflected back the way it came, rather than absorbed as heat
Conductivity
How well the Rod conducts heat to its neighboring rods, and the Reactor itself
Radioactivity
The power AND frequency of Neutron emission
Stimulated Emission
The % Odds that any given interaction will result in the emission of an additional Neutron
Neutron Radioactivity
A secondary, additive Radioactivity stat that always emits "High Speed" Neutrons (discussed later)
Stimulated Neutron Emission
As Stimulated Emission, but for High Speed neutrons
All Materials that can be made into rods have values in all of these fields - though most materials are arbitrarily limited to only be used for certain rod types. All materials that are radioactive, for example, can only ever be made into Fuel rods and no other type. Materials that aren't radioactive can never be made into a Fuel rod.
There are FOUR types of
Rods
Gas Channel Rod - This Rod increases the maximum volumetric Flow rate of the Reactor (IE, it makes the pump stronger), and serves as a direct point of contact for any gas flowing through the Reactor; IE it is a point of "exit" for any heat generated within the reactor. Gas Channel Rods HALVE the "Interactivity" of the material.
Heat Exchanger - This Rod DOUBLES the Conductivity of the Material it is made from, making it much easier to "move" or "balance" heat between all the rods the exchanger touches. Heat Exchangers TENTH the "Interactivity" of the material.
Fuel Rod - This Rod has no special characteristics beyond being the only type that radioactive materials can be made from, it exists purely to allow the radioactivity of the material to generate neutrons.
Control Rod - This Rod DOUBLES the "Interactivity" of the material it is made from, and can be manually Raised/Lowered via the Reactor's UI to modulate (That means "Control/Adjust within some range of values) the Control Rod's interactivity further (between 0% and 100% of the rod's maximum interactivity).
A full list of every material and their values can be found in the in-game Guidebook!
Neutrons
Now that we know what the types of rods are, let's cover the meat and potatoes of the Reactor - Neutrons. What is a Neutron? Well, I won't be giving an atomic physics lesson - so for this purpose just consider it as some kind of particle or projectile which carries some amount of Energy. Any Neutron which manages to leave the reactor entirely will produce a "burst" of Radiation around the reactor which is typically powerful but very short lived.
When a Fuel Rod emits Neutrons, it will generate a random number of them within a small range (1-2 or 2-3, depending on whether it is "Normal" Radioactivity or Neutron Radioactivity - yes the terms are confusing, no I did not decide what terms to use. Blame the actual irl scientists) and launch each of them in 1 of 8 directions around the rod (the Reactor is a 2-dimensional grid). Up/Down, Left/Right, and each Diagonal.
Each Neutron has a "Speed", which generally indicates the amount of energy it has and affects how likely it is to interact with a Rod and how much heat the Rod will gain whenever it Interacts at all. Normal radioactivity tends to produce "low" speed neutrons, and Neutron radioactivity produces High speed neutrons. Some materials, like Plutonium, have both normal and Neutron radioactivity, making them extremely radioactive and unstable since they roll to emit neutrons twice as often and of course emit a higher number of higher speed neutrons.
Rods, as established, have some % chance of Interacting with a Neutron. This chance is rolled any time a Neutron passes over the slot a Rod is in. If the Rod does interact, the Neutron can do a vast number of things depending on its Speed. Neutron Speed is a relatively small number - 1, 2, 3, 4, etc. (I believe 3 is the current cap; though there is no code-reason it cannot be higher). Whenever a Neutron rolls to interact with a Rod, it will lose 1 Speed and the Rod will gain an amount of heat (I do not know or have the specific number, nor does it particularly matter). If its speed becomes 0, it will be absorbed/deleted and the Rod will gain further heat. If the Rod is also Radioactive, then it rolls against the Stimulated Emissions stats of the Rod to see if additional neutrons are generated and if they are it will gain even more heat.
When a Neutron is Speed 1 on interaction, it will also roll against the Rod's Reflectivity to see if it is instead bounced back the way it came rather than absorbed - in which case its speed won't change.
When a Neutron's speed is higher than one, all Interaction will do is reduce its speed by 1, heat up the rod, and it will continue on its merry way as if nothing else happened. Thus it is important that you really fill out all of a Reactor's slots and keep the fuel rods relatively centralized to maximize heat gain and minimize "waste" Radiation.
The last thing to note is that any time a Fuel Rod rolls for Stimulated Emission, its radioactivity level will drop and it's "Spent" level will rise (which is just a value telling you how much of the "Fuel" inside the rod has been used up). Stimulated Neutron Emission will instead lower Neutron Radioactivity and raise the normal Radioactivity level instead, giving such rods dramatically more lifetime.
Reactor Setup
So Neutrons are basically angry bouncy balls and the Reactor is a big angry ballpit of death. But how does one actually set up a Reactor that doesn't explode, doesn't sterilize engineering, and actually generates power?
Glad you asked! There are NUMEROUS ways to set up a reactor depending on what exactly your goal is. You can try and emphasize pure heat generation, you can try to maximize safety, you can even try to do special things like Tritium or Frezon production (an advanced topic not covered by this guide), or maximize "waste" radiation for the purposes of Rad Collectors outside the reactor to further boost its power gains.
For the purposes of this guide, I will show you THREE different setups - a "Basic" Setup that is safe, powerful, and easy to use; an "Advanced" Setup which requires more micromanagement but has significantly higher power gains; and a "Fun" setup for making the reactor explode as quickly as possible for those interested in using it to Antag (it's not actually a round-ending explosion! Just... very deadly)
Piping
But first... piping. Dread it. Run from it. Atmospherics arrives all the same. Thankfully the Reactor and its sister machine, the Turbine, both operate VERY simply and easily and so piping them is exceptionally easy. For basic setups, you can in fact quite literally just pipe directly from input to output on each machine (Reactor out -> Turbine in; Turbine out -> Reactor in) and all you need beyond that is some way to get gas into the actual pipes. Though such a basic setup won't work for higher power applications, and has absolutely 0 safety nets if something goes wrong. For safety, you may want to combine the pipes into a single loop and add a Filter for removing select gases; or even an emergency venting valve. I'll offer no specific piping here because every station that has reactor puts the machines in different spots and has differently shaped rooms - you'll have to flex those muscles yourself!
Legend
For the purposes of the following setups, I will use abstract diagrams - because I am way too lazy to set up a dev env just to get screenshots. So here I will provide a legend that informs you of which icons in the diagram correspond to which rods, along with in-game screenshots of what those actually look like when slotted into the reactor.
Control Rods
Gas Channels
Heat Exchangers
Fuel Rods
Use these images to decode the diagrams I am about to show!
Basic Reactor, "Arachne"
This is the Arachne. Named so for its resemblance to a spider's eyes, it is a basic setup often used as a roundstart Prefab on ss13 versions of the game. We, however, will have to build it ourselves using frankly gratuitous amounts of steel and employing Tactical Hardware Expropriation for Further Tasking (T.H.E.F.T.) to acquire Plasma and Uranium from the SMES room for additional fuel rods. With steel parts and Cerenkite- and sufficient amounts of water vapor in the pipe- this reactor can very safely produce around 8MW of power in the Turbine. This makes it an excellent starter setup for getting the reactor rolling and getting income for Cargo to afford better materials and additional turbines (or turbine parts once funky rebases) and a better reactor. It requires little management- just make sure you insert the fuel rods last and set the control rod level to 20% to start with, lowering it to 0 only once the steel rods inside the reactor have mostly balanced out the heat and the Turbine is actually producing 8MW or more.
The main drawback of course is that Cerenkite sucks and takes forever to expend, so you'll spend a loooooong time (nearly an entire hour) waiting for the rods expend enough to be worth recycling. Worse still, when constructed out of Steel parts the Arachne simply cannot handle the heat of the better fuel rods (plutonium, uranium, bananium); demanding that it be upgraded to Brass Channels/Exchangers and Plasteel Controls - and even then you need to keep the insertion level relatively high and micromanage it to ensure random chance doesn't cause a runaway meltdown.
Advanced Reactor, "Bismuth"
This is the Bismuth, an Advanced Reactor design which requires alot more doing to make work than the Arachne - but rewards you with faster Cerenkite expenditure, and a far superior heat exchange rate allowing for extremely high outputs even with very angry fuels.
"But it has HALF as many rods! How could it POSSIBLY output more power?!"
Ah, herein lies the most important lesson with the Reactor - the Reactor isn't about making heat. It's about using it. Anyone can inject a can of plasma into the Reactor's coolant line and generate enough heat to trick a nearby station's sensors into thinking a new star was born - it takes a true master to actually get that heat out of the reactor and into a Turbine for electrical production. Thus - what matters more is not the total raw potential output of your rods, but how well you can move heat out of the reactor
Thus - the Bismuth, named so for its square-ish, iridescent pattern and how easily it melts down. Operating a Bismuth requires technical skill, knowing exactly how much plasma to use to truly juice the fuel rods, micromanaging control rod levels to prevent runaway meltdown while still allowing for powerful neutron generation, and of course removing and replacing rods with on-hand extras if things get too hot (as well as utilizing more advanced piping to make sure the tritium output doesn't explode or otherwise fuck everything).
Like the Arachne, it can function with cerenkite and steel parts- but only just barely. To truly get the most out of a Bismuth, you'll want to upgrade to Plutonium (or bananium) and Brass (or gold) parts; depending on how competent your salvs have been. Chances are cargo is giving 100% of their gold/silver to science - so you may have to Strategically Transfer Equipment to Alternate Location (S.T.E.A.L.) 120 or so for maximum performance.
The true danger of Bismuth is that it relies on plasma injection to get to higher power outputs - this is the cost of utilizing the maximum possible number of exchangers and channels on every Fuel Rod while still also having control rods at all (no control setups exist, but are exceedingly dangerous when used with anything more powerful than Cerenkite and have a nasty habit of sterilizing engi). Bismuth, if you are not careful, can also result in Engi sterilization - so do make sure its got at least 1 layer of Reinforced uranium walls in the room if you want to get the absolute most out of it.
Bismuth's greatest advantage is that plasma-injection generates far more neutrons per-rod than a normal, non-plasma setup might; Meaning the rods will Expend significantly faster, thereby allowing for much faster Plutonium production while also maintaining higher output over that duration (IE you won't need to spin down the turbine or PTP; you can just add more plasma as time goes on until the rods are completely spent). This will allow you to upgrade to Plutonium rods much earlier, especially since it only needs 4 of them rather than Arachne's 8.
The Demon Core, "Lucifer"
This is the Demon Core, named after an infamous fissile incident which claimed the lives of several scientists in their simultaneous discovery of just how incredibly dangerous nuclear fission can be. The Lucifer operates on one simple principle - Maximize the Runaway Reaction. Neutrons leaving the reactor generate rads and not heat, that's WASTEFUL. DISGRACEFUL. THIS Setup captures the absolute maximum possible amount of neutrons, while still balancing that heat and ensuring it can be extracted from the reactor. No controls between the fuels - that would REDUCE neutron output. PATHETIC. No, instead we want BOHRUM controls, DIAMOND controls even! MAXIMIZE Neutron REFLECTION. MORE NEUTRONS = MORE POWER. MOAR. MOOOAAAAAR
In all seriousness, the Lucifer can be used in a legitimate context. It is extremely resource efficient, since bohrums are the most reflective control after Diamond (which is, for practical purposes, inaccessible at the current most). Since it prioritizes neutron reflection, it also generates way more neutrons per rod than any other kind of setup even without plasma- which can generate immense heat and expend the rods very very quickly. Like the bismuth, it is exceptionally prone to melting down and ironically the way to mitigate this is to LOWER the control rods and let neutrons out of the reactor (possibly sterilizing engi) - and, of course, to remove the fuel rods entirely.
But, if you perhaps SEEK the meltdown... simply don't. Feed it plasma... let it grow HOTTER. Reactor Meltdown is deadly but distinctly NOT round ending. It simply produces an absolute metric FUCKLOAD of heat which is likely to cause the Turbine to explode as well. This will damage Engi immensely, but not beyond all repair - the round ends only if engi is incompetent or command are cowards. But, just in case, do make sure to ahelp before doing a Lucifer DAGD