It's interesting how you could hand a solution out on a platter and all that will happen is that people will run around yelling 'it isn't perfect'. As if any powersource has a 100% uptime guarantee.

U.S. nuclear power plants typically refuel every 18 to 24 months. The average planned outage time is about a month. We never hear much about how nuclear power plants only have a ~95% planned uptime.

The problem isn't the uptime, it's that the downtime strongly correlates across all instances of wind power and across all instances of solar power in a country: https://gridwatch.templar.co.uk/

So what? It's not as if those baseline powerplants that we have today will all suddenly disappear. They will just have a lower utilization factor. And that's perfectly fine.

Solar, hydro and wind when you have them, nuclear when you don't, gas when you don't have nuclear and coal when you don't have gas. It is really quite simple. And the best bit is that you can have your solar and wind installations up and running before the ink is even dry on the kind of permit and investment required for a nuclear plant and it is much cheaper to boot, as well as decentralized so far more resilient and friendlier to the grid (assuming the grid is well designed in the first place, which isn't always true).

And 'in a country' is the wrong level to be thinking at. You should look at much larger areas than that, and across both longitude and latitude.