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1943 Reactor diagram using boron control rods. Control rods are inserted into the core of a nuclear reactor and adjusted in order to control the rate of the nuclear chain reaction and, thereby, the thermal power output of the reactor, the rate of steam production, and the electrical power output of the power station.
A reactor vessel head for a pressurized water reactor. This structure is attached to the top of the reactor vessel body. It contains penetrations to allow the control rod driving mechanism to attach to the control rods in the fuel assembly. The coolant level measurement probe also enters the vessel through the reactor vessel head.
The X-10 Graphite Reactor was the world's second artificial nuclear reactor after Chicago Pile-1 and was the first reactor designed and built for continuous operation. [47] It consisted of a huge block, 24 feet (7.3 m) long on each side, of nuclear graphite cubes, weighing around 1,500 short tons (1,400 t), that acted as a moderator.
Unit 2 was shut down in early January 2012 for routine refueling and replacement of the reactor vessel head. [48] On January 31, 2012, Unit 3 suffered a radioactive leak largely inside the containment shell, with a release to the environment below allowable limits, and the reactor was shut down per standard procedure.
A reactor protection system is designed to immediately terminate the nuclear reaction. By breaking the nuclear chain reaction, the source of heat is eliminated.Other systems can then be used to remove decay heat from the core.
The Reactor Protection System (RPS) is a system, computerized in later BWR models, that is designed to automatically, rapidly, and completely shut down and make safe the Nuclear Steam Supply System (NSSS – the reactor pressure vessel, pumps, and water/steam piping within the containment) if some event occurs that could result in the reactor entering an unsafe operating condition.
The reactor head under inspection. Unit One is an 879 MWe pressurized water reactor supplied by Babcock & Wilcox. The reactor was shut down from 2002 until early 2004 for safety repairs and upgrades. In 2012 the reactor supplied 7101.700 GWh of electricity. [14] In 1973, two more reactors were also ordered from Babcock & Wilcox.
This and the risks posed by liquid sodium in the event of an accident at sea led Admiral Rickover to select the pressurized water reactor (PWR) as the standard U.S. naval reactor type. The S2G was removed from USS Seawolf and replaced by the S2Wa reactor, using components from the spare S2W that was part of the USS Nautilus program.