It's probably too late for a full-on nuclear rollout. We need to reduce global carbon emissions really quickly, at least 5% (18%) per year starting right now [1,2] if we want a chance of staying below 2° (1.5°). Building nuclear power plants takes years even at the current rate of construction, if were to replace all fossil fuel by nuclear over the next fifteen to twenty years we would definitely run into capacity constraints, for example for manufacturing pressure vessels, or just having enough qualified personnel to build and run the things.
On the other hand, with the same money we could start building ridiculous amounts of wind, solar, and an improved grid and get immediate payoff, without having to wait years of unmitigated emissions for reactors to come online.
But what about the costs of energy storage to provide baseload capacity? And on top of that, if the goal is CO2 reduction, we need to generate 4x more electrical energy to replace fossil fuel chemical reagents and things like fertilizer production with non-fossil fuel sources that are far less 'efficient'. And that is before we start talking about future growth of electrical needs.
It won't be cheap, but neither will be the effects of global warming. The important question is whether it can be done or not, and on that front all signs point to yes.
Regarding storage, there is a tradeoff between an improved grid and storage requirements. It's always windy somewhere, if you have the grid to transport that power to where it's needed, you need much less storage.
> We need to reduce global carbon emissions really quickly...
I've been hearing this argument for at least 15 years now, and it's always followed by the assertion that nuclear plants are slow to build while solar and wind are quick to deploy.
And yet here we are, nothing has changed, the same arguments are repeated, only louder. Germany has shut down half her nuclear fleet, has very slowly built up renewable generation to maybe 30% of electricity production (only possible by abusing her neighbors' grid as a virtual battery), but has scarcely brought down her CO2 emissions, which are still more than twice those of France per capita.
And to think this blunder is celebrated as a success! It's not. If time was really of the essence, we'd do what France did between 1975 and 1985. Nuclear can be built quickly---they already did it, it can be done again.
Your math is off on the current scale of wind and PV and the time it takes to get it anywhere significant. Plus you are forgetting storage and infrastructure costs due to the intermittent nature of these sources and the imposed load factor. See https://jancovici.com/en/energy-transition/renewables/100-re...
The French government thinks they can make this transition and save 50 Billion compared with using nuclear. This blogger thinks it'll cost at least 10x more after doing some napkin math. Who do we believe?
On the other hand, with the same money we could start building ridiculous amounts of wind, solar, and an improved grid and get immediate payoff, without having to wait years of unmitigated emissions for reactors to come online.
[1] http://folk.uio.no/roberan/img/GCB2018/PNG/s00_2018_Mitigati... [2] http://folk.uio.no/roberan/img/GCB2018/PNG/s00_2018_Mitigati...