We do sometimes do that! The problem is the condenser water is usually in the mid 100Fs which by the time you pump that somewhere it cools even more and then most people don’t like living near power plants so the cost of running the pumps and the piping is generally more than the energy saved. Iceland has a lot of geothermal heat that people are much less opposed to living near vs O&G or nuclear

But how do you get the energy to pump the water up stream

The heat of vaporization is also a huge negative of using water as you need to condense the water and then reboil it which wastes a bunch of energy

On the nuclear side there are also alpha voltaics, beta voltaics and gamma voltaics that take radiation and generate electricity. Alpha rely on alpha particles ionizing usually a gas, Beta voltaics rely on beta particles which are electron or positron emissions and gamma voltaics take photons in the gamma region and use them to excite electrons to generate electricity.

Overall though heating water is significantly easier to do, more efficient, and more robust