I thought fusion reactors got too hot? Or am I thinking fission?
It does get hot but if it is a small enough or quick enough reaction it can be contained.
In a fusion process, two lighter atomic nuclei combine to form a heavier nucleus, and at the same time, they release energy.
This is the same process that powers stars like our Sun. Devices designed to harness this energy are known as fusion reactors.
Fusion processes require fuel and a highly confined environment with a high temperature and pressure, to create a plasma in which fusion can occur.
In stars, the most common fuel is hydrogen, and gravity creates the high temperature and confinement needed for fusion. Fusion reactors generally use hydrogen isotopes such as deuterium and tritium, which react more easily, and create a confined plasma of millions of degrees using inertial methods (laser) or magnetic methods (tokamak and similar), although many other concepts have been attempted.
The major challenges in realising fusion power are to engineer a system that can confine the plasma long enough at high enough temperature and density for a long term reaction to occur and, for the most common reactions, managing neutrons that are released during the reaction, which over time can degrade many common materials used within the reaction chamber.
As a source of power, nuclear fusion is expected to have several theoretical advantages over fission. These include reduced radioactivity in operation and little nuclear waste, ample fuel supplies, and increased safety.
However, controlled fusion has proven to be extremely difficult to produce in a practical and economical manner. Research into fusion reactors began in the 1940s, but to date, no design has produced more fusion power output than the electrical power input; therefore, all existing designs have had a negative power balance.[1]
Over the years, fusion researchers have investigated various confinement concepts.
The early emphasis was on three main systems: z-pinch, stellarator and magnetic mirror.
The current leading designs are the tokamak and inertial confinement (ICF) by laser.
Both designs are being built at very large scales, most notably the ITER tokamak in France, and the National Ignition Facility laser in the United States.
Researchers are also studying other designs that may offer cheaper approaches.
Among these alternatives there is increasing interest in magnetized target fusion and inertial electrostatic confinement.
The difference in mass between the reactants and products is manifested as either the release or absorption of energy.
This difference in mass arises due to the difference in atomic “binding energy” between the atomic nuclei before and after the reaction.
Fusion is the process that powers active or “main sequence” stars, or other high magnitude stars.
A fusion process that produces a nucleus lighter than iron-56 or nickel-62 will generally yield a net energy release.
These elements have the smallest mass per nucleon and the largest binding energy per nucleon, respectively.
Fusion of light elements toward these releases energy (an exothermic process), while a fusion producing nuclei heavier than these elements will result in energy retained by the resulting nucleons, and the resulting reaction is endothermic.
The opposite is true for the reverse process, nuclear fission.
This means that the lighter elements, such as hydrogen and helium, are in general more fusible; while the heavier elements, such as uranium, thorium and plutonium, are more fissionable.
The extreme astrophysical event of a supernova can produce enough energy to fuse nuclei into elements heavier than iron.
In 1920, Arthur Eddington suggested hydrogen-helium fusion could be the primary source of stellar energy.
Quantum tunneling was discovered by Friedrich Hund in 1929, and shortly afterwards Robert Atkinson and Fritz Houtermans used the measured masses of light elements to show that large amounts of energy could be released by fusing small nuclei.
Building on the early experiments in nuclear transmutation by Ernest Rutherford, laboratory fusion of hydrogen isotopes was accomplished by Mark Oliphant in 1932.
In the remainder of that decade, the theory of the main cycle of nuclear fusion in stars were worked out by Hans Bethe.
Research into fusion for military purposes began in the early 1940s as part of the Manhattan Project.
Fusion was accomplished in 1951 with the Greenhouse Item nuclear test.
Nuclear fusion on a large scale in an explosion was first carried out on November 1, 1952, in the Ivy Mike hydrogen bomb test.
Research into developing controlled thermonuclear fusion for civil purposes began in earnest in the 1940s, and it continues to this day.
Containment and stabilization.
Most Fusion reactions are very short term burst.
I’m interested in what they used for fuel.
The fission process often produces free neutrons and gamma photons, and releases a very large amount of energy even by the energetic standards of radioactive decay.
Nuclear fission of heavy elements was discovered on December 17, 1938 by German Otto Hahn and his assistant Fritz Strassmann, and explained theoretically in January 1939 by Lise Meitner and her nephew Otto Robert Frisch.
Frisch named the process by analogy with biological fission of living cells.
For heavy nuclides, it is an exothermic reaction which can release large amounts of energy both as electromagnetic radiation and as kinetic energy of the fragments (heating the bulk material where fission takes place).
In order for fission to produce energy, the total binding energy of the resulting elements must be more negative (greater binding energy) than that of the starting element.
Fission is a form of nuclear transmutation because the resulting fragments are not the same element as the original atom.
The two nuclei produced are most often of comparable but slightly different sizes, typically with a mass ratio of products of about 3 to 2, for common fissile isotopes.[1][2]
Most fissions are binary fissions (producing two charged fragments), but occasionally (2 to 4 times per 1000 events), three positively charged fragments are produced, in a ternary fission.
The smallest of these fragments in ternary processes ranges in size from a proton to an argon nucleus.
Apart from fission induced by a neutron, harnessed and exploited by humans, a natural form of spontaneous radioactive decay (not requiring a neutron) is also referred to as fission, and occurs especially in very high-mass-number isotopes.
Spontaneous fission was discovered in 1940 by Flyorov, Petrzhak and Kurchatov[3] in Moscow, when they decided to confirm that, without bombardment by neutrons, the fission rate of uranium was indeed negligible, as predicted by Niels Bohr; it was not.[3]
The unpredictable composition of the products (which vary in a broad probabilistic and somewhat chaotic manner) distinguishes fission from purely quantum-tunneling processes such as proton emission, alpha decay, and cluster decay, which give the same products each time.
Nuclear fission produces energy for nuclear power and drives the explosion of nuclear weapons.
Both uses are possible because certain substances called nuclear fuels undergo fission when struck by fission neutrons, and in turn emit neutrons when they break apart. This makes a self-sustaining nuclear chain reaction possible, releasing energy at a controlled rate in a nuclear reactor or at a very rapid, uncontrolled rate in a nuclear weapon.
The amount of free energy contained in nuclear fuel is millions of times the amount of free energy contained in a similar mass of chemical fuel such as gasoline, making nuclear fission a very dense source of energy.
The products of nuclear fission, however, are on average far more radioactive than the heavy elements which are normally fissioned as fuel, and remain so for significant amounts of time, giving rise to a nuclear waste problem.
Concerns over nuclear waste accumulation and over the destructive potential of nuclear weapons are a counterbalance to the peaceful desire to use fission as an energy source.
These sort of Farnsworth reactors are terribly inefficient, and they only fuse a very tiny portion of their fuel source. When some of the atoms are fusing, they get very hot in the near vicinity of them, but there are so few that are fusing, the overall temperature of the whole thing does not become that great.
They make good neutron sources, but they use up far more energy than they produce.