ABSTRACT
Producing electrical power using nuclear reactors is similar to using coal, oil, or natural gas. But rather than burning fossil fuel, nuclear Ÿssion heats the water. Depending on the design, water is circulated through the top of the reactor or through separate steam generators. ˜e heated water is used to turn steam turbines coupled to electrical generators that produce electricity. ˜e temperatures and pressures are much lower than in fossil-Ÿred boilers. In a boiling water reactor (BWR), they are about 285°C (550°F) and 7.6 MPa (1100 psi), and in a pressurized water reactor (PWR), about 315°C (600°F) and 16 MPa (2250 psi). When using pulverized coal as a fuel, the steam conditions in a supercritical unit can reach around 600°C (1100°F) and 30 MPa (4360 psi). ˜e nuclear steam is at lower temperatures and pressures, so the nuclear steam turbines require larger blades to extract the same energy for a given megawatt rating. For e²ciency reasons, the blade tips are close to Mach 1, causing the nuclear turbines to run at lower revolutions per minute (rpm). ˜ese are sometimes called half speed machines which operate at 1500 or 1800 rpm for 50 or 60 Hz electrical frequency, respectively. ˜is aµects the physical size of the turbines and components like bearings and the conŸguration of the turbine rotors. With lower temperatures and wet steam, care has to be taken to prevent erosion and impingement damage in the steam path. Erosion/corrosion is particularly important for steam piping safety.
