I have also been thinking about implementation of nuclear reactors in GT6 recently (thanks Chernobyl!) and have done some research. A simplification and gamification of nuclear engineering is not easy, as nuclear reactors are quite complex and there are many different designs. Nuclear reactors can’t just be single blocks someone plops down in the world, they need to be optimization puzzles imo.
The things around reactors, like processing nuclear fuel are obviously easier to design, but there is something that needs to touched on: Radioactivity and nuclear waste. Radioactivity should incentive automation of the processes involving nuclear materials. Therefore radiation should be implemented in a way that items in a players inventory can be radioactive and therefore punish the player, but when they are in chests or machines they should have no effect on the player even if he stands on the machine. Having radioactivity be a more global thing is an option, but I don’t see many benefits to it other than being a reason to implement geiger counters.
Hazard suits should subtract from the radioactivity of an item in the inventory, making lightly radioactive materials completely non-effecting and lessening the impact of heavily radioactive materials. Radiation could be implemented in such a way that the player “absorbs” it, Fallout 4 did it that way, where radiation would reduce the maximum health points. Removing radiation from the player should be difficult, death shouldn’t reset it (maybe lower it a bit). Maybe some hard to fabricate or dungeon-loot “anti-rad”? A natural constant decay on the radiation on the player would probably also be a good idea to make lower radiation much less tedious.
ReactorCraft implements nuclear waste in a good way, as a “pseudo fluid” that can only be pumped with special waste pipes and only be stored in waste drums. RC then goes a step further and turns the waste into items when in the drums, which represent different waste isotopes and decay at different rates. I think GT can skip this last step and just have the pseudo fluid stored, without it EVER decaying. That should be the major disadvantage of nuclear energy in GT6.
So now onto the reactors: The main thing the player needs to control is the power output of the fuel and the reactivity of the fuel. Is the reactivity lower than 1, the power output of the reactor sinks, the chain reaction can’t sustain itself. If it is at 1, the output will be constant and the chain reaction controlled. Higher than one and the output rises, potentially exponentially which means “enjoy your new crater”.
Balancing reactivity should however not be able to be done directly, it should be done indirectly. This is where absorbers and moderators come in. For starters, moderators slow down neutrons allowing them to create more fission, thus increasing reactivity. Absorbers absorb neutrons into their core, lowering the number available neutrons for fission, thus lowering reactivity. Both slowing and absorbing a neutron creates a bit of heat. Different materials have different absorption or moderation properties and GT could go very deep into the topic, transforming materials when they absorb neutrons, have them decay into other stuff, etc…, but a simplification would probably suffice.
So what are these absorbers and moderators? Well control rods that are mechanically inserted or pulled out of the reactor are usually absorbers or moderators. Greg could easily provide a lot of them with different absorbtion or moderation values for many materials using his material system. For example, graphite is a common moderator. As materials also have melting points, some control rod materials may melt in the reactor, making them unable to be removed, which would be a very Greg way of ruining your reactor, potentially even your base when it were moderator rods.
Other than control rods, liquids could be used as absorbers directly around the core, water for example. A dry core would therefore be much more reactive, so keep your pumps running!
But what about temperature? As the temperature of the core increases or decreases, the absorbtion and moderation values of certain materials may also change, boiling water has a much lower absorbtion for example. The reactivity of fuel is also effected depending on the fuel type. And don’t let your fuel rods melt or your liquid fuel core solidify (Ok, the latter may be significantly harder to archive if not going with crazy fuels, but it should still be possible). Changing the water pressure to rise the water density is also an effective way to raise the absorption value, but requires better powered pumps. Water should not be the only coolant possible, heavy water would also be an obvious candidate, which has an even greater absorbtion rate.
But what about the nuclear waste that builds up in the core? Some will decay into the Xenon 135, which is a excellent neutron absorber. Normally it gets “burned up” in the reactor, i.e. when produced by decay, it instantly absorbs a neutron and turns into other waste, never building up big quantities of Xenon. However when running the reactor at a high output for a long time and then shutting it down, the waste will slowly decay into Xenon, which however doesn’t get burned, making starting the reactor up again very hard cought Chernobyl cought which can potentially lead to disaster if handled inappropriately.
So I’ve written a lot of stuff and ideas, but it’s still not a real gameplay concept, I’ll probably organize this mess into something usable this weekend.