Nuclear reactor

Supercritical-Water-Cooled Reactor.

Three Mile Island nuclear reactor and power plant

A nuclear reactor is a machine that uses fission to generate heat. There are different designs which use different fuels. Most often, uranium-235 or plutonium-239 are the main components of these fuels.

Most nuclear reactors are power reactors, used to make electricity. In nuclear power plants heat from the fission reactions in the reactor changes water into steam. The steam is then used to power electric turbines which make electricity. Some small power reactors run nuclear submarines. As with other steam engines, the turbines take energy from the movement of the steam.

Some reactors are used for other purposes. Some reactors make neutrons for scientific research and others make radioactive isotopes. Some universities have small nuclear reactors to teach students how reactors work.

The first nuclear reactor was built in 1942 by a team of scientists led by Enrico Fermi.^[1] This was a part of the Manhattan Project which needed the fuel from the reactor to make the atomic bomb.^[1] The first nuclear reactor to make electricity was a small experimental reactor built in Idaho in 1951.^[1] It made just enough electricity for four light globes.^[2]

Nuclear reactors are expensive to build because of the many safety features they need to have.^[1] There is also a problem with the huge amount of radioactive waste from the reactors.^[1] However, they produce electricity cheaply, and do not pollute the air. There have been serious accidents at several nuclear reactors: Windscale (UK) 1957, Mayak (USSR) 1957, Three Mile Island (USA) 1979, Chornobyl (USSR) 1986 and Fukushima (Japan) 2011.^[1] Safety concerns have limited the growth of nuclear power.^[1] There are about 437 reactors around the world which provide about 5% of the world's electricity.^[1]

Nuclear Reactor Media

An example of an induced nuclear fission event. A neutron is absorbed by the nucleus of a uranium-235 atom, which in turn splits into fast-moving lighter elements (fission products) and free neutrons. Though both reactors and nuclear weapons rely on nuclear chain reactions, the rate of reactions in a reactor is much slower than in a bomb.
The Chicago Pile, the first artificial nuclear reactor, built in secrecy at the University of Chicago in 1942 during World War II as part of the US's Manhattan project
Lise Meitner and Otto Hahn in their laboratory
Some of the Chicago Pile Team, including Enrico Fermi and Leó Szilárd
Primary coolant system showing reactor pressure vessel (red), steam generators (purple), pressurizer (blue), and pumps (green) in the three coolant loop Hualong One pressurized water reactor design
NC State's PULSTAR Reactor is a 1 MW pool-type research reactor with 4% enriched, pin-type fuel consisting of UO2 pellets in zircaloy cladding.
Treatment of the interior part of a VVER-1000 reactor frame at Atommash
In thermal nuclear reactors (LWRs in specific), the coolant acts as a moderator that must slow down the neutrons before they can be efficiently absorbed by the fuel.
Diablo Canyon – a PWR
The CANDU Qinshan Nuclear Power Plant