Be advised, this thread is now OUTDATED. Please refer to the NEW GUIDE!
Note: This IS goddamn complicated. Do not ask for "Pls make youtube tut", because i doubt you will want to watch a 1-hour video tutorial either. If you are not capable of comprehending the complexity of this system, don't worry, but pay a visit to the Nuclear Engineering section of this forum. You will probably find a design matching your personal requirements in there and don't need to bother understanding the mechanics, at all.
1. Your best friend: the Nuclear Reactor
The first thing you should keep in mind while thinking about Reactors: They're expensive. Reeeeeeeaaaaally expensive. In redo, they can convert Uranium into ridicolous amounts of energy.
A reactor consists of a main unit, the "Nuclear Reactor" and up to 6 "Reactor Chambers". A Reactor by itself merely consists of an 6by3 grid for installations. Each Reactor chamber placed adjacent to the original Reactor will provide some cooling, more hull integrity and a new column to place stuff in. This means, with full "upgrades", you will get a 6by9 Reactor.
To get the Reactor into producing energy, you will need 2 essential parts, no reasonable Reactor gan run without: Uranium Cells and Coolant Cells.
Uranium Cells are, trivially, the part producing the energy. Each uranium cell lasts quite long, 200000 ticks to be exact. This is approximately a length of 160 minutes, in effect 8 full Minecraft Days. However, as every knows, Nuclear Fission generates vast amounts of HEAT, as well. To absorb this heat, a basic and cheap component is the Coolant Cell. As well, there are one-use coolants, Heat derivators and additional Reactor Plating. We'll come back at this destinctive components later on.
To regulate your reactor (remotely, or even automatically), it has an additional function: If you apply redstone to the Reactor (or any adjacent block, f.e. chambers), all Uranium cells will be locked, instantly stopping to pulse. The remaining reactor components will procede as normal and usually cause a slow cooldown.
To set up a new reactor, you will not only need the hardware, but as well a good idea of the mechanisms to create something profitable. What is profitable? That depends on the requirements you want for the reactor.
1. Efficiency - A single uranium cell can result in 1-5kk EU, depending on the reactor's efficiency
2. Safety - 100% safe reactors are hard to design. Sometimes you will want to sacrifice safety for another attribute instead
3. Cooldowns - One can design a reactor which is capable of running non-stop. Other reactor designs tend to heat up and will need some cooldown periods in between.
4. Breeder - It's possible to enrich uranium to gain more uranium cells from one chunk of uranium ore. You need a special reactor for this, though...
5. Hungry - "Hungry" Reactors need additional ressources to keep running. For example they tend to burn through Coolant Cells (which need to be replaced) or use one-use coolants.
Generally, you won't be able to construct "Teh ULTIMATRON 5000 super-efficient, no-risk, never-cooldown-ned, breeding-integrated, never-hungry Reactor". It is, with a lot of planning, possible to create a reactor fullfilling one or two attributes to their max, but that's it.
Now, after covering the basics, let's move on to the actual mechanisms behind it:
2. Nuclear Fission, How to (don't)
For simplicitys sake, we will work with a "heat"-based system. Heat is a basic value, representing the (duh) heat of the reactor. Generally, heat is bad. Heat will affect the surrounding of the reactor, damp water, set fires and even (if too hot) smelt solid materials into lava. You don't want to have a fully-overheating reactor either, it will tend up to suddenly vanish... with a loud bang.
On the other hand, Breed-Reactors work more efficiently when heated up to certain degrees. We'll cover this in the seperate Breeder-Section.
Generally, you can assume a reactor to explode when reaching 10000 heat. This is not related to degree or any known measurement of Earth, but just the well-known MCHI (MineCraft Heat Index), commonly referred to as "heat" (Hydro-Eating, Annoying Temper).
Quite every (cooling) component of the reactor can store 10000 heat. How it does obtain and how it does work with this heat depends on the component.
Let's first answer the question: How does a reactor even heat up?
By Nuclear Fission done in and between uranium cells.
Due to the laws of block-ish physics, uranium reacts extremely linear and can be accustomed for in advance:
A single uranium cell will "pulse" once. Pulses mean energy and heat production. Generally, all uranium cells will pulse at once every few moments (to be exact, once every second), which is called the "Reactor Pulse/Tick".
Each pulse will produce 100 EU, spread over 1 second (20 ticks), resulting in 5 EU/t.
The heat generated by each pulse is, for unknown, quantum-physic-based (balance) reasons, dependant on the amount of coolant elements surrounding the Uranium Cell:
4 (fully surrounded): 1 heat @ each element
3 : 2 heat @ each Element
2 : 4 heat @ each Element
1 : 10 heat @ Element
0 : 10 heat @ Reactor Hull
As you can see, fully surrounding Cells with Coolant Systems (which are consisting of Coolant Cells, Reactor Plating and Heat Derivators) is generally something advised. However there is an important aspect AGAINST this:
Uranium cells "interact". For each adjacent uranium cell, the original cell will pulse another time. This does NOT reduce the cells longlivity. Effectively, this means a single cell will produce 1kk EU. If you place another cell into the same reactor, but distant of the first cell, the Reactor will produce 2kk EU.
If you place both cells next to each other, however, the Reactor will produce 4kk EU.
The problem of this behavior:
1. More pulses mean more energy generation, but as well more heat, too.
2. If you surround a cell with further Uranium, you trivially don't surround it with Coolants, thus the derivation of heat becomes more difficult.
This effect is called "Reactor Efficiency".
In best case, you surround an uranium cell by 4 other cells. In this case, the middle cell will pulse 5tuble, causing the maximum 5kk output. In worst case the cell is isolated and will only produce 1kk total. The higher the efficiency, the better... as long as the heat doesn't melt your reactor, that is.
But how do we create a good reactor if they will just overheat? By using:
3. Coolant Systems, A must-ave for Nuclear Engineers (and inhabitants of deserts)
There are 4 Coolant Systems the reactor can make use of.
1. Coolant Cells
A coolant cell can, as most components store 10000 heat. Next to this important function, it does cool itself down by 1 heat per reactor pulse.
2. Reactor Plating
Reactor Plating serves multiple functions:
It can store 10000 heat and will (though 10 times slower then a coolant cell), cool itself down as well.
More important, it can transport heat to adjacent components. If a reactor plating is heated up by something, it will instantly divert the heat among all surrounding coolant systems. Even to other platings (which will again divert the heat, however, NOT to other platings anymore).
Additionally, each piece of plating will increase the Reactor Hull's integrity, causing it to to take more heat before melting.
3. Heat Derivatos
These are important, highly-advanced and expensive gadgets for advanced Nuclear Engineers and can as any components store up to 10000 heat without melting.
HD's posess a unmeltable, highly-intelligent Circuit to measure, recognize and rate the heat of itself, surrounding components and the Reactor itself.
Thus, it will, each pulse, check all nearby components and attempt to balance their heat levels, by either absorbing or emitting up to 6 heat per pulse. As well, it will absorb (or emit) up to 25 heat from/into the Reactor Hull.
4. Lastly, the most underestimated Coolant System: The reactor itself
Folloring the basic laws of heat distribution, a rector will emit heat to it's surrounding. Each cubic meter (block) of air surrounding the reactor in a 3by3 sphere, will provide 1/4th of cooling. As well, water will provide a full point of cooling each. As well, the Reactor itself can vent 1 heat per pulse into the world by itself. Additionally Reactor Chambers possess intern heat vents, each chamber emitting additional 2 heat per pulse.
The sum of all these fators is called "Outward cooling".
Next to these Coolant Systems, there are "One-Use" Coolants, which can be used to ensure a reactor stays cooled even with moderate heat generation.
The most basic way of cooling a rector, trivially, is pouring fresh cold water in. Thus, if the reactor is heated up enough (>=4000), putting a bucket of water into the system will evaporate the water, resulting in a loss of 500 heat.
As well, one could fill the reactor with ice, which will instantly melt once the reactor is hotter then 200 heat (quite always) and will reduce it's heat by 200.
Whereas Water clearly is more effective, Ice can be stacked, whereas buckets would need to be refilled constantly. Your choice.