Well first of all I would argue all in cost for a whole countries power needs, based on current fission is still competitive. If you build a large number of plants you can get a very good stable energy supply.

With renewables you need a great deal more transportation of power, you need a gigantic deal of storage of power to be truly independent.

I would still go with nuclear even if its more expensive in terms of dispatch energy cost. Because as we have seen, you can have pretty long period where both wind and solar are at 5% capacity, and you better have a backup that can last weeks if you have no fossil backup.

All that said however, I think just saying 'regulation'. Doesn't capture the problem. I think the more accurate description of the problem is 'innovation'. After a golden period of the 50/60 innovation slowed down dramatically in the 70s and came to essentially a dead stop and since then we have barley improved other then some marginal gains on old designs.

Not only way most state research money removed all over the world, the current state of the art was embedded in regulation and even if somebody would be willing to put up the capital to research a new reactor making it commercial was essentially impossible. Specially in the US, one of the few places where state independent nuclear might have had some chance, regulation were essentially defined in a way that only water cooled reactors could ever be legal.

In Europe all nations other then France turned on nuclear pretty hard and while some plants were built, actual innovative designs were not ready to be commercial and mood turned against nuclear and most projects were canceled.

France did build a lot of nuclear but overall they were not really innovative, the just scaled the production of existing technology. This is great of course and gave France green energy. However even there as time went on nuclear was seen as a legacy, just waiting to be finally replaced.

So nuclear today is still low mostly temperature, and this requires specially gas turbines. The kind of turbines that are no longer used in modern gas and coal plants. As coal and gas used better turbines and scaled their production nuclear was unable to take advantage of those better steam turbines. And because no high temperature nuclear power existed, there also wasn't much effort put into turbines required for such high temperature reactors.

So today building a PWR you have a couple of big issues. The 'Pressure' in PWR requires you to build a hugely expensive reactor with gigantic heat exchanges that need to be contained in a huge secure building that needs to be able to contain a hydrogen explosion (and that doesn't actually work as you could see at Fukushima). Second, you need a hugely expensive very large, not very efficient steam turbine that today is only used for nuclear, and thus is even more expensive then historical was.

Third, because of the scale of these projects, in addition to the nuclear bit, they are simple gigantic public civil engineering projects that suffer from all the same problems that huge civil engineering projects suffer from.

Now had we innovated and moved to what is now called 'GenIV' reactors many of these things could be solved. First I would say, the term 'GenIV' is really a bad term because some reactors we now call 'GenIV' have been in development of some kind since the very beginning and have no iterative evolution with the Gen1-Gen3. The 'Gen' here refers to commercialization not research.

So how would these reactors potentially solve many of the issues. First, you can massively decrease the size of both your reactor, heat exchanger and your steam turbine. All of this results in a massive improvement in capital cost and therefore also the scale civil engineering project. In addition the increase of safety of these of these plants, should have a significant effect on the required operation cost. The more efficient fuel burn of most of these reactors, also leads to improved operation because refueling is required far less often and can mostly be done online, improving the utilization.

So if you combine those advantages, I would consider all in these plants would make a hell of a lot more sense. And the reason they don't exist is partly regulatory but but those regulations and maybe more importantly the regulatory environment are reflection of the the overall turn against nuclear most of Western society has made. Some of the regulation we have today are over the top or unnecessary, but changing these would not instantly impact the price of the next PWR we build.

A nuclear regulatory agency and a country need to actually WANT nuclear innovation. As an example of such a process, look at what Canada did once they sold CANDU. They actually said, we want to innovated and be part of the next generation of nuclear and they changed their regulatory process and environment to reflect that.

https://nuclearsafety.gc.ca/eng/reactors/power-plants/pre-li...

Something like this could have happened already 40-50 years ago and in a much larger market like the US. But that was not the direction the government went in. In the US, there is clear pre-and-post Nuclear Regulatory Commission (1974) where before new reactors happened all the time, essentially no progress happened. That is not just the fault of the NRC, but also the broader changes in the state and society reflected in those changes.

In my opinion we should go back to building nuclear, for a country like mine, Switzerland, I do not see the extra cost of a nuclear plant as the big problem. We should be able to have energy independence with years worth of energy stored. Renewables are not great here, neither solar nor wind is really well suited to the situation. And if you really want to go 100% the storage requirements are very scary. The capital cost of nuclear can be paid off over literally the next 80-100 years while the plant is in operation.

I think the example of France shows that we could have had green energy for the last 40 years, and that Frances big mistake was to go away from nuclear (they actually started depending on gas). France was one of the few shining lights, and built amazing projects like Superphénix (https://en.wikipedia.org/wiki/Superph%C3%A9nix) but instead of building more, they were killed politically.

I predict in 100 years, nuclear fission will be what powers most of society. All in, from first principle, a very high energy density fuel will simply win the race in the long term. Its only a matter of building the right reactor, and turbine (or figure out aneutornic fusion).