I found a method for throttling a nuclear plant based on heat demand, so it doesn't waste uranium. You just have to make sure something is consuming steam all the time(I like to attach it to steam demand in science production), have heat exchangers further out than your heat consuming buildings, and then put a circuit on the steam tank to run the reactor when the tank falls below 90% or so. The heat exchangers will stop generating steam when heat gets below 500, which allows the tank to start emptying, which is detected by the circuits so the reactor is given fuel to heat up again. It stops providing fuel when the tanks are full, which means the temperature doesn't go much higher than 600 or 700 so it doesn't waste heat.