A combination of the two: Renewables and SMRs.

Nuclear is great but there's a very small amount of uranium 235 (what is used to instantiate the chain). that's the biggest issue, I think the relative abundance is 0.5 - 0.9% compared to uranium 238 98 or 99 percent.

Even the efficiency is like 33% where wind is 40 - 60% (depending on on shore or offshore) and solar is 20%. The main appeal here isn't about optimization, even at the lower efficiency it produces a fuck ton of energy. 92 reactors produce the entire energy generation supply of 17%. There is approximately a thousand gas plants to produce the 40% of US energy generation, and we are talking about combined cycle level efficiencies (60%). If we doubled our nuclear power plant fleet to 200 nuclear reactors, we would generate more energy then the current leader in energy generation. Nuclear power plants produce a shit ton of energy.

The main reason to go with renewables, long term, is it doesnt use limited resources, and that there is still a lot of R&D that can't be known theoretically, but through trial and error. With wind turbines, for example, there is so much mechanical failure as a result of the torque being generated by the wind, I wouldn't be surprised if the turbine just breaks off from the base of the windmill.

PV cells also have a lot of R&D going for them, not mechanically, but electrically. The PV cells we commonly use they are generally inefficient because once light passes through the PV cell theres more energy that could be used. There are techniques to combat this issue by stacking multiple solar cells and running it through a wire, but that technique also costs more money.

SMRs I would consider are also the future due to lower upfront cost and maintenance costs, its easily commercializable compared to nuclear power plants (which are designed from scratch).

Wind and solar. Pop up, pop down. Nuclear needs entrenched infrastructure. The future is always renewables.

Hey, I'm in the biz. "Either or" isn't a thing. We need a completely diversified grid. Mostly nuclear would be ideal with a big chunk coming from solar/wind/hydro. Even fossil fuels have a place in certain applications.

It depends on a lot of factors, which is part of why the question is divisive. To oversimplify:

On one hand, when done optimally, nuclear provides huge amounts of power extremely cleanly and safely - even compared to renewables. There is also a number of options that could allow for significantly reduced costs and significantly increased flexibility such as SMRs, or other reactor technologies. On the other hand, nuclear has a mountain of roadblocks in front of it including antinuclear sentiment, policy blocks (particularly stemming from that sentient), and a lack of know-how increasing cost and slowing both building of reactors and development of new technologies. This means it could be amazing in the long term, particularly in regions that are suboptimal for renewables, and for industries requiring large amounts of power 24/7, but it can't do much in the short-term.

Renewables meanwhile, are cheap, fast and easy to build and easy to expand to the point where until ideal conditions, even individuals can afford to install and run their own electrical infrastructure. As such, its amazing to quickly reduce prices, reduce emissions, and reduce dependence on governments. On the other hand, most renewable options lack flexibility. Solar only runs half the day, and the further you are from the equator, the lower the efficacy. Wind takes up huge amounts of space. Hydro requires damable rivers and space to avoid destroying ecosystems. There's lots of options, but they also have large limits. As technology improves these will limits will be reduced (such as improving battery technology) but they are still present.

Ultimately, this means that where available, renewables are nearly always best in the short term. Long term, it gets messier, since it depends on what we invest in now, which technologies end up going somewhere versus being dead ends, and how the world changes in general. Most predict a mixed approach would be best, both to address the variety of global needs, and to spread risk. All that said, global warming is, at this point, a short-term problem. We can't afford to focus on the long-term anymore, which is why there is so much focus on renewables. We need to be replacing and expanding infrastructure yesterday so we don't have time to wait for nuclear, and debatably, can't afford to be investing in an energy technology that won't pay off for decades when that could be further invested in renewables.

My understanding is the best answer is 'all of the above.' Nuclear is big and expensive, and just as expensive to expand, and has ongoing input costs like skilled staff, water, fuel, etc. but produces very steady, controllable power, and can do so for decades in a well designed and maintained system. Solar and wind, on the other hand, are very easily scaled down to smaller budgets, but generate intermittent power. It can be very useful to have the nuclear as a backup for moments of high demand and low solar/wind output, but very efficient to mostly use renewables because they don't have much of an ongoing input cost.

Both are needed for a healthy power structure.

Wind, solar even with batteries have low innertia (actually no innertia at all by themselves). If you want to resist turbulences on the power network without free innertia resistance by turbines (nuclear, gas, hydro), you need expensive equipment to generate that innertia other ways, and it can get quite expensive.

Hydro would be great but it's highly seasonal.

Wind & solar for sure. Nuclear fission is great right now, but fissile material is a finite resource. It will, like oil, eventually become too expensive to extract.

So the planet's been using solar and wind for millions of years and it seems to have worked okay.

Nuclear was probably the best choice in the 1970’s; France made the best choice. But we’ve seen over and over again the problems are getting worse rather than better. Paperwork and process ever more unwieldy. Construction taking longer and longer. Radioactive waste building up with no permanent disposal. By far the highest cost power generation, and the difference is getting wider.

Much of the posts about how great it will be this time is just astroturfing by those trying to profit. No, “small modular reactors”, didn’t solve the cost, construction, or process issues, but only raised the cost of generation. No, thorium isn’t the silver bullet and really doesn’t exist yet.

I guess saying both is out?

Radioactive nuclear waste

It depends on your definition of "long term". If we're talking centuries, millenia, then wind and solar seems the clear winner with current and predicted available technology for the simple fact that they produce no waste.

Nuclear energy produces nuclear waste. Currently, our best/only plan to dispose of that waste is to bury it in a hole and hope nobody ever finds it or a natural disaster ever disturbs it.

Wind and solar.... don't. So, barring some unforeseen technological breakthrough that allows us to reuse or recycle nuclear waste, probably wind and solar.

It seems like battery+solar is the cheapest worldwide as of recently.

I am not familiar with UK conditions. Scandinavian winters remain a problem for solar.

If the area has good and reliable access to the sun or strong winds, solar and wind will be cheaper.

If it doesn't, nuclear is there to have your back.

Also, you can put a nuclear power plant on a ship (like Russia and China do) and deliver nuclear power to coastal areas while the proper infrastructure is (re-)built.

There is no universal best way to produce power, you need to mix and match to make a good grid.

Its to bad we did not go nuclear as much as possible before the millenium. Some blame protestors but I blame a lack of standardization. I think france basically showed how it should be done. Given that Im glad my state has a lot of nuclear power now. However wind and solar are just plain old faster to build out and utilize asap and storage is not the issue it was yester years. Thed multi decade length of a standard nuclear plant makes them kinda a no go and we never really solved waste storage decently. Now maybe the mini reactors or such may make sense. By that I mean nuclear is not going away I think we will just use it differently.

when you say "long-run" is it human life expectancy long or heat-death of the universe long?

Nuclear is great for investors, data centers, and the military. The amount of energy it produces allows for more energy intensive operations and research, gives a lot more energy for everyone to play with, but they can also now import nuclear material for "energy" reasons.

Best course of action if you believe these things are good. Bad if you think people should be able to produce their own energy, and don't need that much energy to prosper.