The UK Has Switched Its Fusion Reactor, A Step Closer To LIMITLESS Energy
22 July 2018
UK-based Tokamak Energy has heated a plasma of hydrogen to 27 million degrees Fahrenheit (15 million degrees Celsius) in a new reactor for the first time — hotter than the core of the sun.
The company, which is named after the vacuum chamber that contains the fusion reaction inside powerful magnetic fields, says the plasma test is a milestone on its quest to be the first in the world to produce commercial electricity from fusion power, possibly by 2030.
The successful test – the highest plasma temperature achieved so far by Tokamak Energy – means the reactor will now be prepared next year for a test of an even hotter plasma, of more than 180 million degrees F (100 million degrees C).
Nuclear fusion is essentially the same process that gives birth to stars. It involves hydrogen atoms moving at high temperatures and high pressures crashing into each other to form helium.
The collision generates enormous amounts of energy, which can theoretically be used as a clean source of unlimited electricity. A single spoonful of hydrogen atoms can produce as much energy as 28 tons of coal without the nasty side effects made by nuclear fission as can be seen in Chernobyl and Fukushima.
There are, of course, a few requirements for nuclear fusion. For one thing, it requires special types of hydrogen isotopes called tritium and deuterium. For another, fusion reactors need to be as hot as 100 million degrees Kelvin, around the same temperature found at the core of the hottest stars in the universe.
Tokamak Energy believes that a spherical tokamak much smaller than its ITER counterpart will be able to provide enough heat from the fusion reactor to generate electricity economically. The key to this, says CEO Carling, is the strength of the magnetic fields keeping the plasma in place. “If you look at fusion power in tokamaks, the energy is proportional to the plasma volume, but it also varies according to the fourth power of the magnetic flux – so if you can run with very high magnetic flux, then that will have a much bigger effect on the fusion power than making the machine bigger.”
Two factors will enable Tokamak Energy to reach its goal quickly, he says. One is the smaller scale of the machines, compared to ITER’s. The other, crucially, is private sector funding. To date, the company has raised more than £22m from a variety of sources, including venture capitalists and more mainstream institutional investors such as pension funds, Carling says.
What's a Stellarator?
A stellarator is a device used to confine hot plasma with magnetic fields in order to sustain a controlled nuclear fusion reaction. The name refers to the possibility of harnessing the power source of the sun, a stellar object. It is one of the earliest fusion power devices, along with the z-pinch and magnetic mirror.
The stellarator was invented by Lyman Spitzer of Princeton University in 1951, and much of its early development was carried out by his team at what became the Princeton Plasma Physics Laboratory (PPPL). The basic concept is to lay out the magnetic fields so that particles circulating around the long axis of the machine follow twisting paths, which cancels out instabilities seen in purely toroidal machines. This would keep the fuel confined long enough to allow it to be heated to the point where fusion would take place.
The first Model A started operation in 1953 and proved the basic layout worked. Larger models followed, but these demonstrated poor performance, suffering from a problem known as pump-out that caused them to lose plasma at rates far worse than theoretical predictions. By the early 1960s, any hope of quickly producing a commercial machine faded, and attention turned to studying the fundamental theory of high-energy plasmas. By the mid-1960s, Spitzer was convinced that the stellarator was matching the Bohm diffusion rate, which suggested it would never be a practical fusion device.
The release of information on the USSR's tokamak design in 1969 led to the Model C stellarator being converted to the Symmetrical Tokamak, as a much higher-performance concept. Large-scale work on the stellarator concept ended as the tokamak got most of the attention. The tokamak ultimately proved to have similar problems to the stellarators, but for different reasons. Since the 1990s, this has led to renewed interest in the stellarator design.
New methods of construction have increased the quality and power of the magnetic fields, improving performance.
A number of new devices have been built to test these concepts. Major examples include Wendelstein 7-X in Germany, the Helically Symmetric Experiment (HSX) in the USA, and the Large Helical Device in Japan.
What's Nuclear Fusion?
In nuclear physics, nuclear fusion is a reaction in which two or more atomic nuclei come close enough to form one or more different atomic nuclei and subatomic particles (neutrons or protons). The difference in mass between the reactants and products is manifested as the release of large amounts 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.
|Written by: Linda Wallers|