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Comment by cortesoft | Hacker News Reader

To be efficient with nuclear, though, you need steam buffers... nuclear power can’t stop burning fuel once it starts, so unless unless you are spending all the power as you generate it, you need to store it. Burn a unit of fuel, store all the steam, and then don’t put more fuel in the reactor until the steam level goes below a threshold, then repeat.

This is especially true because you want to have a group of four reactors together for maximum efficiency, which generates a crazy amount of power. You spend more time not generating more heat and just living off the steam storage than you do burning fuel.

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Ok, but it isn't worth it. Yes, you get more "power value" out of nuclear fuel if you ration it. But even if you overbuild your power by 2x your current target load and let the extra go to 'waste', your ore reserves will still likely give you many hundreds of hours of power.

I've tried and made many buffered, circuit-controlled, meticulously fine-tuned power plants that are optimized for fuel conservation and they always have some hitch or edge case where they act erratically, or the steam is not balancing, or the reactors cooled down too much, or... (Or you're lategame and you outscaled it too far and need to eke the UPS back.) And is the moment when you're under siege and losing losing power really the best time to be debugging that 30-combinator fuel-optimizing circuit network you picked up off reddit and randomly modified until it seemed to work? Right.

A challenge: calculate how many hours the total amount of ore you are willing to mine will last you. If you maximize efficiency through productivity modules -- even gradually -- I bet it will be hundreds if not thousands of hours.

So you make a trade: a small fixed increased cost in fully automating and maximizing nuclear fuel production in exchange for the benefit of vastly reducing the complexity of construction and operation of your primary power production facility. No tanks, no circuits, no buffering -- instead, full automation and productivity for fuel production and 100% power all the time. Give yourself a(n automated) backup chest or two of fuel nearby for days (calculate it!) of time to deal with fuel production problems. Would you even have that much time if you burned all the coal in the same area?

I would take a trade like that every day.

>meticulously fine-tuned

On what planet is a bang-bang controller considered a fine-tuned control system in an automation game? The only simpler system is proportional.

The point of doing it isn't necessarily for some maximum efficiency, but because it is the only problem in the entire game that could even ask the player to make a control system, which is a very fun thing to do.

If you build a controller for a single nuclear reactor, a bang-bang controller is indeed pretty simple once you know how to build an SR latch.

Scaling that to multiple reactors becomes complex because you can no longer control reactors independently and still get adjacency bonuses from them operating together. Further, there are complexities from emergent behavior that you have to control for. Steam turbines, like steam engines, auto scale steam consumption to power demand. The problem is they don’t do it uniformly. If you have 2 turbines attached to 2 tanks and you only need 1, the game might consume all of 1 tank first, leaving you with the 50% burst capacity. It becomes a big problem with day/night cycles and solar/accumulators in the grid.

I never tried to balance this, but I suppose it’s possible by building a circuit to link together all tanks and shut off their flow when one‘s storage deviates too much from the average. This sounds really complex to me and not worth it.

I’ve explained to the best of my understanding of the game engine’s behavior, but I know that fluid mechanics is also inaccurate and complex to design for. There’s a known issue with flow behaving asymmetrically. One reason is because the game updates state in a certain order, so water and steam flow with a bias for certain directions (n, s, e, w).

Also, thanks for teaching me a term from control theory (1)

(1) https://en.m.wikipedia.org/wiki/Bang–bang_control

Ah individual control of a large array of reactors is trickier. I think the bang-bang controller with keeping all reactors synchronized has good legs, but it stops scaling well at some point. If the buffers become the limitation and you don’t want to run all of the reactors synchronized then a PID controller would be a good pick. The output value would choose how far up the row of reactors you enable. If you could force max load on will, then loop tuning is a possibility.

To maintain the simultaneous reactor bonus, you would want to keep the fueling cycle synchronized and just adjust which reactors are enabled each cycle. This can be done with a clock that has a period of one fuel cycle.

One interesting thing is that due to the nature of reactors, you will have higher efficiency in running more reactors if your buffer does not run out. It might be possible to eek out a little more efficiency if you fall back to a bang-bang controller in low load scenarios (making sure the threshold and number of reactors used won’t overfill the buffer, which is practically unlikely in low load scenarios). I would have to experiment with this a bit more to see if it’s reasonable to capture more efficiency.

All of this is practically orthogonal to the standard players perception of efficiency, but I find it fun.

https://en.wikipedia.org/wiki/PID_controller

https://github.com/quchen/articles/blob/factorio/factorio/ci...

Fascinating write up! Thank you for sharing!

I mean, it's a game, though. A lot of the things I do when I play games "isn't worth it." But I have a lot of fun, anyway. :)

> A challenge: calculate how many hours the total amount of ore you are willing to mine will last you. If you maximize efficiency through productivity modules -- even gradually -- I bet it will be hundreds if not thousands of hours.

What do you mean "hours"? It'll last multiple real-time years.

Reactors don’t top out in efficiency at 4. I went from a 2x2 to a 2x7. My 2x4 power plant was buffered and would create flow problems when half of my buffers drained before the other half. When I scaled to 2x7, I dropped all but one tank to let me monitor when my reactors were above 500C.

My biggest learning with nuclear is that if I’m producing too much power for my factory, I’d rather grow my factory to meet my power supply than to make a more sophisticated power plant. Your mileage may vary.

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