The thermodynamic process used by thermal power plants to convert the heat generated in a reactor into useful work, such as electricity generation. Most power plants use the Rankine cycle. A pressurized working fluid, usually water, is heated above the boiling point in the reactor. The steam expands in the turbine, causing the turbine to spin. Behind the turbine, the liquid is cooled, condensed and, after compression, goes back into the reactor. The waste heat is released to the atmosphere or to a water reservoir. The efficiency of this heat-to-power conversion is about 30 to 40 per cent.