Nuclear power station

A **nuclear power plant** or **station** uses a nuclear reactor to generate heat which is used to generate steam that drives a steam turbine connected to a generator that produces electricity.

The reactor uses material like uranium235 or plutonium239 to create nuclear fission, releasing kinetic energy, gamma radiation, and free neutrons. A portion of these neutrons may be absorbed by other fissile atoms and trigger further fission events, which release more neutrons, and so on. This is known as a nuclear chain reaction and this generates heat energy. A nuclear reactor coolant — usually water with salt — is circulated past the reactor core to absorb the heat that it generates. The heat is carried away from the reactor and is then used to generate steam. This then drives a steam turbine that turns an alternator which generates electricity.

Current attempts to create nuclear fusion are:

* In the National Ignition Facility (NIF) in the USA, laser fusion machine is housed in a ten-story building the size of three football fields. 192 giant laser beams are fired down a long tunnel and hit an array of mirrors that focus each beam onto a pinhead-size target, consisting of deuterium and tritium (two isotopes of hydrogen). This totals 500 trillion watts of laser power, scorching the pellet target to 100 million degrees, much hotter than the center of the sun. The pellet is vaporized, which unleashes a shock wave that collapses the pellet and unleashes the power of fusion. In a 2021 breakthrough, the lasers produced 10 quadrillion watts of power - about 70 percent of the amount of power it took to generate the laser beams. For the first time in any fusion research facility, the output was 70 percent of the laser energy delivered to the target as fusion energy, and this exceeded the energy delivered to the capsule that contains the fuel by more than five times. Ignition was achieved on August 8, 2021.
* The International Thermonuclear Experimental Reactor (ITER) in Europe uses huge magnetic fields to contain and compress hot hydrogen gas. Then an electrical current is sent surging through the gas, heating it. The combination of squeezing the gas with the magnetic field and sending a current surging through it causes the gas to heat up to 270 million degrees Fahrenheit. It will generate 500 megawatts of energy, which is ten times the amount of energy originally going into the reactor.
* The ARC fusion reactor (affordable, robust, compact) is developed by the Massachusetts Institute of Technology (MIT) Plasma Science and Fusion Center (PSFC). The ARC has a conventional advanced tokamak layout with high-temperature superconductor magnets.
* The Joint European Torus (JET) is an operational magnetically confined plasma physics experiment, located in the UK. Based on a tokamak design, it hopes to reach a *scientific breakeven* where the "fusion energy gain factor" or *Q* =1.0.

A problem with fusion is with the magnetic field. Gravity is attractive and can compress gas evenly into a star, but electromagnetism is both attractive and repulsive, so gases bulge out in complex ways when compressed, making the magnetic confinement for controlled fusion exceedingly difficult. One way of solving this is via a *Tokamak*, which drives hot plasma around in a magnetically confined torus, with an internal current. When completed, ITER will become the world's largest tokamak. *Stellarators* create a twisted plasma using external magnets, while tokamaks do so using a current induced in the plasma. A modern variation uses a solid superconducting torus that is magnetically levitated inside the reactor chamber.

#### News

* 13 December 2022: Fusion ignition has been achieved. This means that the energy output is more than the energy input for the first time.
* 11 August 2023: Ignition for the second time generates more energy than the first.
* 23 October 2023: Japan's JT-60SA achieves “first plasma”, the biggest tokamak to create and contain a super-hot plasma

See also:

Nuclear reactor

Fusion Power