Steam generators are systems used to to convert water into steam from heat produced in a nuclear reactor core. These devices can measure up to 70 feet in height and weigh as much as 800 tons. each steam generator can contain anywhere from 3,000 to 16,000 tubes, each about three-quarters of an inch in diameter. Inside the steam generators, water is pumped under high pressure, to prevent it from boiling, through tubing passing through the nuclear reactor core. This is referred to as the primary loop. That water flowing through the inside of the tubes then passes through an external heat-exchanger to produce steam in the secondary loop that that is delivered to the turbines to make electricity. The steam is subsequently condensed via cooled water from the ternary loop and returned to the steam generator to be heated once again. The cooling water is itself recirculated to cooling towers where it sheds waste heat before returning to condense more steam. This is the most common way to extract usable energy from a controlled nuclear reaction. In physical chemistry and in engineering, steam refers to vaporized water. ... A Nuclear reactor core is that portion of a nuclear reactor containing the fuel components where the nuclear reactions take place. ... A heat exchanger is a device for transferring heat from one fluid to another, where the fluids are separated by a solid wall so that they never mix. ... WWII era steam turbine used for ship propulsion. ...

These loops also have an important safety role because they constitute one of the primary barriers between the radioactive and non-radioactive sides of the plant as the primary coolant becomes radioactive from its exposure to the core. For this reason, the integrity of the tubing is essential in minimizing the leakage of water between the two sides of the plant. There is the potential that if a tube bursts while a plant is operating, contaminated steam could escape directly to the atmosphere. Thus during scheduled maintenance outages or shutdowns, some or all of the steam generator tubes are inspected by eddy-current inspection. Radioactive decay is the set of various processes by which unstable atomic nuclei (nuclides) emit subatomic particles. ... Eddy-Current testing uses electromagnetic induction to detect flaws in conductive materials, amongst other operations. ...

In other types of reactors, such as the PHWR (CANDU) design, the primary fluid is heavy water. Other designs use a liquid metal in the primary loop such as sodium, although no liquid metal cooled reactors are currently in service. The CANDU reactor is a pressurized-heavy water, natural-uranium power reactor designed in the 1960s by a partnership between Atomic Energy of Canada Limited and the Hydro-Electric Power Commission of Ontario as well as several private industry participants. ... General Name, Symbol, Number sodium, Na, 11 Chemical series alkali metals Group, Period, Block 1, 3, s Appearance silvery white Atomic mass 22. ...

Types

Westinghouse and Combustion Engineering designs have vertical U-tubes with inverted tubes for the primary water. Canadian, Japanese, French, and German PWR suppliers use the vertical configuration as well. Russian VVER reactor designs use horizontal steam generators, which have the tubes mounted horizontally. Babcock and Wilcox plants (e.g., Three Mile Island) have smaller steam generators that force water through the top of the OTSGs (once-through Steam Generators; counter-flow to the feedwater) and out the bottom to be recirculated by the reactor coolant pumps. The horizontal design has proven to be less susceptible to degradation than the vertical U-tube design. Westinghouse could refer to: George Westinghouse Westinghouse Electric Corporation. ... Combustion Engineering was a leading firm in the development of power systems in the United States in the late 20th century. ... Babcock and Wilcox is a power generation and equipment design company. ... Three Mile Island Nuclear Generating Station consists of two nuclear reactors, each with its own containment building and cooling towers. ...

See also

• Steam turbine
• Nuclear power plant
• Power station