Power Plants Essays - Nuclear Technology, Energy Conversion

Power Plants Essays - Nuclear Technology, Energy Conversion Power Plants An electrical power plant has a nuclear reactor to produce electricity. A nuclear reactor produces heat through nuclear fission in which atomic muclei break apart releasing large amounts of energy. In the core of the reactor, a self-sustaining nuclear reaction takes place. The power level of an operating reactor is monitored by a variety of thermal, flow, and nuclear instruments. Power output is controlled by inserting or removing from the core a group of netron-absorbing control rods. The position of these rods determines the power level at which the chain reaction is just self-sustaining. In the pressurized water reactor, the water collant operates at a pressure 150 atmospheres. It is pumped through the reactor core, where it is heated to about 620oF. The superheated water is pumped through a steam generator where, through heat exchangers, a secondary loop of water is heated and converted to steam. The steam drives turbine generators, is condensed back to water, and pumped back to the steam generator. The secondary loop is isolated from the reactor core water and, therefore is not radioactive. A third stream of water from a cooling tower is used to condense the steam. The reactor pressure vessels are 49 feet high and 16.4 feet in diameter, with walls 10 in. thick.The core houses some 82 metric tons of uranium oxide contained in the corrosion-resistant tubes. Finally generators produce electricity which is delivered to a power grid by transmission lines. During operation, and even after shutdown, this large 1000 megawatt power reactor contains billions of curies of radioactivity. Radiation emitted from the reactor during operation and from the fission products after shutdown is absorbed in thick concrete shields around the reactor and primary collant system. Other safety features include emergency core colling systems to prevent core overheating in the event of malfunction of the main collant system and, a large steel and concrete containment building to retain any radioactive elements that might escape in the even of a leak.