July 16th,1945, fusion was artificially created for the first time after scientists collectedthe first understanding into the physics of the sun. This is when the sun andother stars seem to produce limitless energy as they constantly transformhydrogen into helium by the process of fusion. Fusion is a thermonuclearprocess which means that the atoms have to be astonishingly hot in order to bestripped of their electrons so they can bounce around freely in a plasma. Starsare able to create these incredibly high temperatures due to the fact that theyare so massive so that the pressures in their cores generates the heat tosqueeze the nuclei together. This ideathat we could potentially create clean, limitless energy was sparked.
More thanten times the energy is made by fusion than fission for each gram of fuel usedmeaning that it would almost completely replace nuclear fission power stationsas well as other forms of energy if an efficient reactor was built. However,for the past 70 years we have tried to recreate the fusion power of stars bymagnetic confinement and by inertial confinement but it currently takes moreenergy to initiate the fusion reaction than the output energy. Although humanshave been successful in producing uncontrolled nuclear fusion reactions whichis mainly used to make the hydrogen bomb, all the tremendous energy from thisuncontrolled reaction is released at once in an immensely destructive manner. However,we have not been able to produce a controlled nuclear fusion reaction where thesame amount of energy is released but over a gradual period of time. Stars areso bright due to their massive release of energy from nuclear fusion as theyconvert hydrogen into helium. It releases a lot of energy due to the largedifference between the mass of the hydrogen nucleus and the helium nucleuswhich is made. The mass of the 4He atom is about 0.
8% less than themass of the four 1H atoms. This lower mass of the fusion products isturned into a considerable amount of energy due to the equation E=mc2. There areseveral requirements needed for nuclear fusion or nucleosynthesis to occur instars. Firstly, a substantial energy barrier of electrostatic forces must beovercome since the nuclei, having had their electrons stripped, will both havea positive charge and will repel one another otherwise. To overcome this, thenuclei can tunnel through coulomb forces by the quantum effect. The coulombbarrier is the smallest for hydrogen’s isotopes compared to 1H whichis why a deuterium-tritium fuel is used in nuclear fusion reactors. Theresulting energy barrier from using D-T is about 0.
1 MeV. One type offusion is Magnetic Confinement Fusion (MCF). This uses magnetic and electricfields to heat and squeeze the hydrogen plasma imitating our sun.
Hundreds ofcubic metres of D-T (deuterium-tritium) at a density of less than a milligram percubic metre are confined by a magnetic field at a few atmospheres pressure andheated to fusion temperature. The power needed to start the reaction will beabout 70 megawatts, with a power yield of about 500 megawatts. The heatproduced by this reaction will heat water to make steam which will then go onto drive electrical turbines to produce electricity.
The secondtype of fusion is Inertial Confinement Fusion (ICF). This uses pulses from superpowered lasers that are focussed very precisely on the surface of a pellet offuel (D-T) which causes an implosion. During the final part of the implosion,the fuel core reaches 100 times the density of lead and ignites at 100,000,000°C. Although fusion can be achieved, the technology of both MCF and ICF has along way to go until there is a net power output.
Although deuterium can befound easily in seawater and is therefore in abundance, tritium is much harderto get with there being an estimated 20kg on Earth and most of it being tuckedaway in nuclear warheads making it very expensive. However, helium-3 may make agood substitute. Although it is very rare on Earth, the Moon may have largequantities of 3He due to being bombarded by it for billions of yearsdue to the Moon’s lack of magnetic field. Therefore, many countries andcompanies have shown interest in mining helium-3 from the Moon’s surface. There wouldbe many advantages to using nuclear fusion as an energy source with the mainone being that it would be a clean energy, producing no greenhouse gases unlikethe burning of fossil fuels and there would be no nuclear waste.
Since there isno chain reaction, there is no risk of what happened at nuclear fissionstations (Chernobyl or Fukushima) where radioactive material was released intothe surrounding area after a meltdown. The fuel would likely be very cheapsince about 1 part in 5000 of the hydrogen in seawater is deuterium which isthe main source of nuclear fusion. As well asthere being many advantages, fusion does not come without its disadvantages.
Its main con is at an economical point of view as billions of either dollars orpounds would have to be invested into research funding with a possibility thatit simply isn’t possible to achieve a net energy output on Earth. This moneycould be spent on different sources of energy such as renewable energy whichhas been proven. Power plants would also be incredibly expensive to build asthey require extremely high temperatures which is hard to contain.