Thank you for this mod. This is the way factorio should have been made, in order to be educational as well.
However I have some comments and suggestions to make towards improving realism.

1. In reality, reactors that use 5% enriched fuels (as in 1 U-235 + 19 U-238) burn about that much of the uranium fuel.
   So I suggest to change the reprocessing recipe to return, say, 18 or 19 U-238, consider that 1 U-235 is burned and thus the energy content is a nicer 8 TJ/cell.
2. I don't understand how the silly "neighbour effect" affects the energy content of a cell. I propose to get rid of it:
   data.raw.reactor["nuclear-reactor"].neighbour_bonus = 0
   and increase the power output to compensate for that, say:
   data.raw.reactor["nuclear-reactor"].consumption = "80MW"
3. Finally, the public notion that reactors are uncontrollable can be corrected with this:
   data.raw.reactor["nuclear-reactor"].scale_energy_usage = true
   Edit: Scratch this, I saw you have done this already.

I am also annoyed by the required number of steam turbines in vanilla.
All in all, the land footprint of the entire nuclear plant should be about 300 times smaller than the equivalent solar plant.

Hi!

Glad to see others are enjoying this mod after I published it, which I'd originally made only for my own use.

As to your suggestions:

As to point 1, my goal was not to completely reproduce the behavior of real reactors, but only to make things more in line with realistic magnitude. For example, making it take millions of times less uranium than coal to power a base rather then mere thousands.

For example, if we were trying to be realistic, then the fuel cells are far too small even with this mod, as the assumed amounts would not realistically be able to achieve sustained criticality with a single fuel cell at all, and likely not even if their energy content were increased x10 and the recipe produce a single cell per craft.

However, glossing over this sort of nuance is well within the limits established by other elements of the game, which are comparably simplified.

(That being said, the idea of a mod which changed the recipe of a fuel cell to require 100 U-235 and 1,900 U-238 and produce cells which each last 2 real-world years at full power has occurred to me. If I make such a mod I'll post a link here.)

However, in this particular case, I think the base game's extremely high burn-up ratio of LEU fuel cells can be realistically justified by assuming they are a futuristically sophisticated traveling wave reactor. In that case, most of the U-238 would be transmuted into Pu-239 and burned over the course of its service life. If you want to reprocess the residual Pu-239 that would be left in such a depleted cell, then I recommend combining this mod with Plutonium Breeding.

As to point 2, when I made this mod back in 1.1, which was the first mod I made, I missed that this was possible. If I had known, I might have done it, since while larger plants can generally be more efficient, the difference between the least and most thermally efficient plants is not even 2x, much less the 4x you can get in the base game. But then again maybe not, since the original goal wasn't to substantially change how the game works, even if I wouldn't have done it that way. But now, I've done much more modding, and I'll think about it.

Removing neighbor bonus and adjusting values to compensate was added in 1.3.0.

Also I went ahead and implemented the idea of larger fuel cells, which I've called "nuclear cores", that have 100x the material cost and energy content of fuel cells, as a configuration option for this mod in 1.4.0.

You made strong points all around.
Regarding the amount of fuel required to achieve criticality, again you are right, and it has also been bothering me.
Perhaps a good solution for this would be to incorporate a large amount of fuel in the initial construction recipe of the reactor.

Since your reply suggests that you missed it, I'll repeat that I have in fact implemented an option in this mod which replaces fuel cells with complete cores, which are 100x more expensive and have a service life of 2.2 effective full power years. (My numbers above are off by 10x, because when typing that post I forgot to include the fact that the base fuel cell recipe produces 10 cells. The correct numbers for a 100x more expensive core is 10 U-235 and 190 U-238 for 1 core.)

I believe that the mechanics of this option are, if not realistically, then at least plausibly consistent with real-world efforts to create high burn-up fuel assembly designs for naval nuclear propulsion reactors using LEU. I'm still assuming a futuristically sophisticated fuel assembly design, since that analysis still assumes 20% enrichment to achieve its goals, but it passes my sense for plausibility in the broad strokes.

Once I again, I thought about it some more and ended up implementing it lol.

As of 1.5.0, the nuclear core option also increases enrichment requirements to match those of the real-world proposals mentioned here.

Brillliant :)