I think the closest we would have are reactors that are gas cooled, or molten salt reactors that can drive very high temperatures and make use of a Brayton cycle, completely removing the steam and the kettle component out of it and using more of a gas turbine technology to get much higher efficiencies.
There have been prototype reactors like that in the past. I think some of those technologies to really move the bar in terms of efficiency are there. They're more advanced than the reactors we've built before.