GT6 nuclear reactors

I’ve been thinking a lot about how nuclear reactors could work in GT6. A lot of mods before have created interesting nuclear reactors so expectations are quite high. However the most interesting, fun, customizable and expandable reactors in modded MC are still the old IC2 reactors.

They provide a perfect optimization puzzle for power, efficiency, material cost and ease of automation with no “best design”, but multiple use cases as normal, breeder or cooling reactors. IC2 Classic stepped things up even further by providing more unique fuels, electric heat vents, steam reactors and a bit of an “crafting system” for them, where you need to breed the best type of fuel additive.

While trying to think of new systems more in the line of ReactorCraft, I wasn’t able to come up with something half as good as IC2s reactors and I doubt there even is, as in-world multiblock designs lack the room limitation and flexibility of a simple inventory.

So why not have GT6 nuclear reactors be a slightly changed IC2 (Classic) reactor?

There are a lot of benefits to this compared to an original in-world multiblock reactor:

  • Generally more server friendly than multiblock variants
  • Smaller, so less chunks need to be loaded for it
  • Breeder reactors and breeding based crafting
  • Familiarity makes learning to use it easier
  • Greater usability of a component heat based system, because component heat can be displayed as a damage bare, which wouldn’t be possible with an in-world solution

Obviously IC2 reactors aren’t entirely fit to GT6, but with some changes and expansions they could be. Having the ability (and need) to place covers on them and configure sides would be the first thing and a obvious addition. Shutting the reactor off would require Redstone Machine Switch, etc. The reactor would also not output electricity anymore, but heat. Heat extraction could be implemented in a number of ways, either just outputting it on the top or on a heat output configured side or with a heat output cover.

Instead of having an entirely separate steam reactor, the reactor is basically a steam reactor from the start. Heat vents should store a liquid or gas and output a hot version of it. The default coolant would just be air, added by a Air Vent cover, producing no hot product, but just outputting the heat directly.

Different coolants would change the properties of the air vents, able to change up how the reactor works entirely. This allows for a lot of design freedom (for the implementation and the user).

Some small new mechanics could also be introduced this way, like moderators. They could double the neutrons passing through them and allow them to pass through. Graphite blocks could act as moderators and water feed heat vents too.

This system would allow many real world reactor designs to be replicated in some way (heavy water, liquid metal, gas-cooled, pebble-bed, molten salt), without special reactor types with their own special mechanics required for them.


Maybe we could make better coolants/fuel sources gated behind different tiers of vents and reactor blocks? So you can start with simpler (dirtier) designs like the light water or the boiler reactor, and then build stronger and safer designs


Yeah i planned to start with distilled water, and then use IC2 Coolant and then use better coolants like molten salt.


While tiered reactors and reactor components fit GT6 perfectly, I think tiering the coolants and fuels isn’t such a great idea, as it would reduce the number of viable reactor designs.

Tiering could however be done in a non-linear way with different fuel and coolant tiering lines, like a water, coolant, salt, gas and liquid metal, with their own progression and the lines all being equally viable (with different use cases ofc). Water to heavy water (maybe even pressurized water and heavy water, but that would need changes to the piping mechanic), mercury to lead to sodium-potassium alloy, etc.


Problem is, fast reactors can’t work with coolants that act as moderators (slow down neutrons) or absorb them, and regular water does both D:
And on the other end, thermal reactors need a moderator to work, and water can be used to help the moderation.

Basically some coolant+fuel combinations wouldn’t work at all anyway IRL


Ofc not all fuel-coolant combinations would or should work well, i.e. be viable. I just want the different reactor types and fuels to be viable, not every combination of them.


Yep, the faster Reactors would require better Coolants to stay Cool, but an early Uranium Reactor could easily run using good old Steam if you dont fill it with too many Rods. As in real Life, you probably dont want Water based Reactors, at least Coolant wise that can end up horrible and also corrosive.

They can emit all the same Power for each Tier to not make it wasteful that way, you just need higher tier coolant for up-scaling the Reactors Main Power Output.

At least that’s what I think for now about it.


Just as a rule of thumb:
thermal reactors need a moderator and only work with odd-numbered isotopes (U235, Pu239, Pu241);
fast reactors only work without a moderator but can use any fuel


Is that a real life thing based on the decay table or is that a gameplay thing you want in?


Real life stuff.
If you need any info on this stuff, please just ask :smiley: I also have a ~10k words long essay on nuclear reactors I wrote two years ago sitting on my computer if you ever feel like reading xD

But seriously, the general concepts (unlike their real life applications) aren’t that complicated. And I’d love to help


Water based reactors are actually not bad at all because water is a moderator and if there is less water, because of heat causing steam bubbles, the moderation effect is lower and the reactivity goes down, causing less heat. This makes water a safer coolant than other coolants.

But yeah, it would be limited to slow neutron reactors, but I don’t see why those shouldn’t be able to scale into the late game, with (pressurized) heavy water, chrome heat vents in a chrome reactor, especially when their fuel is more readily available.

Some ideas for the coolant types:

  • Water/heavy water: Produces steam based on cooled heat. Heat vents act as moderators, moderation based on water-steam ration in the reactor. Neutrons doubled by moderation are useless for breeding. Heat vents have a very high heat transfer rate, but a low heat capacity.

  • Pressurized water/heavy water: Produces super-heated pressurized water based on temperature (can be heat exchanged or turned into steam), heat vents act as moderators with a constant moderation value. Heat vents have a very very high heat transfer rate, but a low heat capacity.

  • Air: Produces heat energy on the top of the reactor based on fuel rod energy. No special properties. Heat vents have a low heat capacity and medium heat transfer rate

  • Gas: Produces heat energy based on the fuel rod energy on the top of the reactor and heated gas based on the cooled heat (can be heat exchanged or directly power a turbine). Heat vents have a medium heat capacity and medium heat transfer rate.

  • Liquid metal: Produces super-heated liquid metal based on fuel rod energy (must be heat exchanged). Heat vents act as component heat vents. Heat vents have a very high heat capacity and medium heat transfer rate. Allows for highest core temperature.

  • Molten salt: Produces hot molten salt (must be heat exchanged) based on fuel rod energy and cooled heat (additive). The hotter the core of the reactor, the less energy and heat adjacent fuel cells produce. Heat vents have a high capacity and high heat transfer rate.

This makes air reactors the most easily usable, especially early game, but definitely the weakest. Gas reactors are a straight upgrade, also directly producing heat, but also super-heated gas.

Liquid metal reactors are best for fast-neutron reactors, breeders, allowing for very high temperatures and being not too hard to cool, but are comparatively bad for energy production.

Water/Pressurized Water reactors are good energy producers, but terrible breeders.

Molten salt are very safe and good energy producers, which are more versatile than water reactors.

Obviously this is not all entirely realistic (“fuel rod energy”, lol, i.e, the IC2 electricity output) and greatly abstracted, but I think going too realistic can very quickly get out of hand (Sorry Xenon). Especially fuels could use some creative liberty to make them more distinct.


I actually really like your suggestion :smiley: for the gas coolant, helium should be the one used as it is being tested by a couple of modern designs =P

Thermal reactors aren’t bad, but they are dirtier (produce radioactive waste). My biggest concern honestly is that I don’t want to see Greg implement a Chernobyl-style light water reactor only because that’s the only type people know about. The new designs are so much cooler!


Another, more experimental, complicated idea for a “coolant”:

  • Molten fuel-salt mixture: Basically turns the heat vents into fuel, emitting heat, energy and neutrons and all, so no cooling with them. This is only possible when non-coolant heat vents are a thing, or cooling would be limited to coolant cells/condensators (if available). Produces hot fuel-salt mixture based on heat, which can be heat exchanged (but a bit of it is lost, so no infinite fuel, but no nuclear waste). Coolant heat vents filled with the fuel-salt mixture also act as a core heat exchanger (averages out percentage-wise), so if they get hot, your core also, if it gets cool, so does your core. Neutron output is lowered with higher temperatures. High heat capacity and no heat transfer/cooling.

This “coolant” is really a liquid fuel. It’s very safe (hot temperatures will make the reactor stop working and no coolant automatically means no fuel) and produces no waste, but cooling it and keeping it efficient is really hard, because it takes away the ability to have a dedicated coolant.

Edit: Would probably be a good idea to just rename the “heat vents” that accept fluids, because they are so mechanically different than heat vents. Something like “Reactor Pipe” or “Reactor Channel”.