How does that translate into costs and build time in the states? I'm guessing longer and much more expensive. There's been multiple large costly nuclear projects that have failed in the construction or retrofit phase (San Onefre).

Nuclear in the US is too risky financially. Most utilities have no appetite for high risk multi billion dollar projects. Unless they are supported and subsidized with guarantees from municipalities.

The last operating nuclear power plant started producing power in 2016. It took 43 years to build. Granted 22 years was paused on purpose since the TVA estimated that the demand for electricity would be too low to justify finishing the project. It also ran over cost but was only 4.7-6 billion in total cost.

Just because these projects are usually unsuccessful in the states doesn't mean it's impossible. It just means it's unlikely and there are other simpler options. If there was a government entity that would push for, subsidize, and support nuclear in a similar manner as solar it would have a chance.