ZIRNOX

The ZIRNOX GCR (gas-cooled reactor) is a nuclear reactor that is generally the first reactor that the majority of players will be able to construct in a world due to its low cost and minimal supporting components. Unlike the RBMK and the PWR, the ZIRNOX is a single, fully assembled machine with a fixed capacity that cannot be extended or modified in a modular fashion like other reactors. As such, it is generally much safer to use and simpler to set up as the player cannot make mistakes in constructing the reactor itself. As well as this, it has a very low power output and very simple operation that only requires a small amount of resources and planning to make completely sustainable. Because of all of these factors, it is generally seen as the best reactor for new players to operate despite its low power output and high fuel consumption.

After construction, the ZIRNOX only requires relatively cheap and reusable zirconium fuel rods to house fuel as well as a small amount of CO₂ and water to fill it's internal tanks. Due to its low power output, it is possible to run the reactor entirely off of cheap single block steam turbines (causing minimal losses in efficiency) and a single steam condenser on lower power fuels. This makes the reactor even simpler to construct as it requires very little infrastructure to cool and spent fuel can be easily removed with a conveyor extractor and routed into a spent fuel processing chain. In addition to this, it can run well on natural uranium fuel, bypassing the need for an expensive uranium processing chain and making it work very well as a breeding reactor.

It is possible to run the ZIRNOX on more powerful fuels, but its power output will always be limited by the maximum allowed pressure and temperature of the reactor, meaning that it has a hard cap to the amount of power that it can produce and amount of fuel it can breed. As such, most players will quickly move onto stronger, more efficient reactors after they exceed the power production capabilities of the ZIRNOX with it being relegated to the role of fuel breeding for isotopes such as Plutonium-239 and Plutonium-238 or Uranium-233 or for the direct breeding of things such as tritium or thorium fuel. Many of the isotopes that the ZIRNOX produces are useful for nuclear weapons or for fuels that can be used in a PWR or RBMK, meaning that it is usually best to continue using the ZIRNOX as a dedicated breeding reactor to supply stronger reactors with fissile material.

Crafting

The ZIRNOX can be made in an assembly machine with the following recipe:

4

8

16

4

GUI and Operation

The GUI for the ZIRNOX reactor can be accessed by interacting with the machine at any point and shows all needed information about the reactor's operation and all controls necessary for its operation.

Fuel Rod Assembly. Contains the fuel rods that react to produce heat within the reactor. Fuel rods with greater amounts of other fuel rods near them will react faster than rods with lesser amounts of other fuel rods near them, meaning that fuel rods placed in the center of a full reactor will deplete faster than fuel rods around the edges. This property does not apply to breeding rods.
Control Rod Button. Extends or retracts the reactor's control rods which disables or enables the reactor entirely. Functionally an of/off button.
Temperature Gauge. Displays the reactors current temperature visually as well as in numerical form when hovered over. Temperatures at or above 800°C will cause the reactor to immediately melt down, also indicated by the temperature gauge dial reaching the end of its display.
Pressure Gauge. Displays the reactor's current pressure in the same way the temperature gauge displays temperature. Pressures at or above 32 BAR will cause the reactor to immediately melt down, also indicated by the pressure gauge dial reaching the end of its display.
Pressure Relief Valve. Allows for 1,000 mB of CO₂ to be vented out of the reactor to reduce pressure.
CO₂ Gauge. Quantity of CO₂ present in the reactor out of 16,000 mB. Most fuels operate with maximum efficiency with 14000 mB CO₂.
Steam Gauge. Quantity of super dense steam present in the reactor out of 8,000mb.
Water Gauge. Quantity of water present in the reactor out of 32,000 mB.
CO₂ Input. Allows CO₂ to be input into the reactor through fluid containers.
Water Input. Allows water to be input into the reactor through fluid containers.

Fuel Reprocessing

See: Guide: Recycling Depleted Fuel for more information

Depleted ZIRNOX fuel can either be removed manually from the GUI or the reactor or automatically by any kind of item extracting block, yielding a spent nuclear fuel rod. The spent fuel can then be extracted from the fuel rod, yielding two pieces of hot spent fuel and the original ZIRNOX rod assembly. This hot fuel then must be cooled down in a spent fuel pool drum before it can be processed into its constituent isotopes in a PUREX. Spent ZIRNOX fuels can provide a variety of very useful and progression necessary isotopes with technetium being one of the most important as it is essential for the production of technetium steel, a material that is useful for creating powerful machinery and tools. All uranium fuels aside from natural uranium, MOX, plutonium, and ZFB MOX fuel will yield technetium when their depleted products are processed, meaning that a variety of arrangements of fuels can yield useful products.

Depleted fuel and fuel rods are highly radioactive and also pyrophoric, meaning that contact with them without strong protection can result in rapid injury and/or death. As such, it is recommended to set up an autonomous handling chain to deal with the waste with conveyor belts and auto crafters, though a good hazmat suit, a pair of tungsten reachers, a decontaminator, and some fast crafting may work well enough in a pinch.

Meltdown

If either the temperature gauge or the pressure gauge reaches their maximum value, the reactor will violently explode, destroying blocks around it and spewing highly radioactive debris in a wide area that must be picked up manually and either destroyed or processed back into resources so that they do not further contaminate the environment. In addition to this, it will spew radioactive gasses in a wide area and spread radiation into surrounding chunks. The destroyed reactor itself will constantly emit radioactive gas until it is removed, meaning that the reactor must eventually be destroyed to fully clean up the meltdown event.

Fallout can be useful for obtaining rare isotopes but its uses are so limited and it produces so little that it isn't worth it to leave a melted down reactor to obtain infinite fallout.

Zirnox Efficiency Table

All tables were created using a setup with three (3) Industrial Steam Turbines, and with only a single type of fuel, to mimic a fully automated Zirnox.

The energy produced by a Zirnox can be higher with mixed fuel types, but will be more risky to automate.

If a cell is missing, it means that the reactor will not be stable with that amount of CO₂ and will eventually meltdown. The highlighted cell shows the optimal power output.

Peak ZIRNOX Power Generation
Fuel	kHE/s generated per 1000 mB of CO₂
	4	5	6	7	8	9	10	11	12	13	14	15	16
Natural Uranium	133.28	142.8	152.32	161.84	166.6	171.36	176.12	180.88	185.64	185.64	190.40	176.12	166.60
Uranium Fuel			214.20	228.48	238.00	247.52	257.04	266.56	271.32	276.08	280.84	266.56	257.04
Thorium Fuel		176.12	185.64	195.16	204.68	214.2	218.96	223.72	228.48	233.24	238.00	228.48	214.20
MOX Fuel						323.68	337.96	347.48	361.76	371.28	376.04	361.76
Plutonium Fuel					285.60	295.12	309.4	318.92	328.44	333.20	342.72	323.68	309.40
Uranium-233									433.16
Uranium-235							366.52	380.80	390.32	399.84	414.12
ZFB Fuel	147.56	161.84	171.36	180.88	185.64	195.16	199.92	204.68	209.44	209.44	214.20	204.68	190.40
LES Fuel	See Meltdown for more information.

Pros and Cons

Pros

Very cheap to construct all of the necessary infrastructure to run.
Incredibly simple to operate.
Can rapidly yield many useful isotopes from common materials.
Runs on such low power that single block turbines and steam condensers can be used to construct a cooling loop.
Can run on cheap unenriched fuels.

Neutral

Outputs dense steam which lowers the amount of cooling infrastructure needed but increases the number of turbines required.

Cons

Incredibly low power output, maxing out below 700 kHE/s.
Rapidly depletes fuel, consuming many times more units of fuel materials per unit of power produced than equivalently powerful RBMKs or PWRs.
Very few options for powerful fuels.
Cannot be used to breed bismuth but can be used to irradiate items.

Trivia

The ZIRNOX is inspired by the British Magnox GCR, which functions effectively the same way.
- The only difference being that the Magnox used a Magnesium-Aluminum fuel rod cladding and the ZIRNOX uses a Zirconium-Beryllium cladding, hence the names.
Its usefulness for breeding weapons grade and reactor grade fuels is also accurate to real life Magnox reactors.
It is often called the CIRNOX as a reference to Cirno from the Touhou project