I'm not sure if nuclear energy is turned into thermal energy using this method, but it definitely makes energy; the reactor fissions a uranium-235 isotope into multiple pieces and controls the energy. The reactor core sits inside a steel pressure vessel, so that water around it remains liquid even at the operating temperature of over 320°C. Steam is formed either above the reactor core or in separate pressure vessels, and this drives the turbine to produce electricity. The steam is then condensed and the water recycled.
