Misnomer: there is no creation of energy going on in this system, or anywhere in the entire universe. Energy is not created or destroyed, it only changes form.
In my explaination, I am just talking about the turbomachinery device called the turbine, not the entire Rankine cycle. Only the component with the blue cone in your picture is called a turbine.
The rest of the simple Rankine cycle components are:
1. Pump (uses a little mechanical work to pre-pressurize the water)
2. Boiler or steam generator (heat addition component), and 3. Turbine
4. Condenser (heat rejection component, either is coupled to nature's water or a cooling tower)
External to the Rankine cycle is the primary coolant loop (colored purple). This is where a coolant (like high pressure liquid water) is in thermal contact with the nuclear material. The nuclear material produces heat from nuclear energy, which transfers through cladding to the primary coolant. The primary coolant then flows to the boiler, and adds heat to the Rankine cycle.
-------Now the turbine itself--------
Turbines are machines which convert the energy of a fluid flow stream into mechanical work done on a shaft. That shaft then powers an electric generator, converting mechanical work into electrical energy. (the generator is not part of the turbine, it is just coupled to it via a shaft)
The turbine is fundamentally no different for a nuclear power plant than for a coal power plant, although the geometry may be different due to design constraints.
A turbine simply involves nozzles capturing high pressure steam, and impinging the turbine blades with it (impulse turbine). Either that, or the nozzles are part or the turbine blades, and they spray high speed steam tangential to the rotation (reactionary turbine).
Condensing of steam into liquid is an UNDESIREABLE phenomena. We want "high quality steam" to exit the turbine, this is why "quality" is the name for vapor mass fraction of a two phase mixture.
The reason we want high quality steam is as follows:
1. Vapor is much less dense than liquid, and less density means higher flow speeds for a given mass flow rate.
2. Droplets of liquid water can be detrimental, as at high speeds, they can erode the metal out of which the blades are made.
So, interestingly enough, it can be an advantage to make an isentropically inefficient turbine. It is still an inefficiency, so you still need to "pay for it". However, by having subtle amounts of entropy generation in the turbine (usually due to friction), it can mean higher quality steam exiting. So the design of a steam turbine is a balancing act of the "lesser of two evils".
The only time when liquid water is desirable in a turbine is when the entire fluid is water, as it is for a hydroturbine.