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| By NASA Goddard Laboratory for Atmospheres and Yohkoh Legacy data Archive [Public domain], via Wikimedia Commons |
Fusion is cheap. It is worth SEPTILLIONS of dollars once viable. It's not much of a gamble because we can see it works in the sun. Also Nuclear is still the BEST alternative we have, nuclear waste is NOT dangerous nor is it particularly high in quantity since the 50s (scientists calculated that all waste in the world would fit in a football field). Forget solar. Forget wind. Nuclear and Fusion is the only way.
Fusion power is a form of power generation in which energy is generated by using fusion reactions to produce heat for electricity generation. Fusion reactions fuse two lighter atomic nuclei to form a heavier nucleus, releasing energy. Devices designed to harness this energy are known as fusion reactors.
The fusion reaction normally takes place in a plasma of deuterium and tritium heated to millions of degrees. In stars, gravity contains these fuels. Outside of a star, the most researched way to confine the plasma at these temperatures is to use magnetic fields. The major challenge in realising fusion power is to engineer a system that can confine the plasma long enough at high enough temperature and density.
As a source of power, nuclear fusion has several theoretical advantages over fission. These advantages include reduced radioactivity in operation and as 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 as of 2017, no design has produced more fusion energy than the energy needed to initiate the reaction, meaning all existing designs have a negative energy balance.
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 USA. 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.
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| By Dstrozzi (Own work) [CC BY (2.5)], via Wikimedia Commons |
Mechanism
Fusion reactions occur when two or more atomic nuclei come close enough for long enough that the nuclear force pulling them together exceeds the electrostatic force pushing them apart, fusing them into heavier nuclei. For nuclei lighter than iron-56, the reaction is exothermic, releasing energy. For nuclei heavier than iron-56, the reaction is endothermic, requiring an external source of energy. Hence, nuclei smaller than iron-56 are more likely to fuse while those heavier than iron-56 are more likely to break apart.
The strong force acts only over short distances. The repulsive electrostatic force acts over longer distances. In order to undergo fusion, the fuel atoms need to be given enough energy to approach each other close enough for the strong force to become active. The amount of kinetic energy needed to bring the fuel atoms close enough is known as the "Coulomb barrier". Ways of providing this energy include speeding up atoms in a particle accelerator, or heating them to high temperatures.
Once an atom is heated above its ionization energy, its electrons are stripped away (it is ionized), leaving just the bare nucleus (the ion). The result is a hot cloud of ions and the electrons formerly attached to them. This cloud is known as a plasma. Because the charges are separated, plasmas are electrically conductive and magnetically controllable. Many fusion devices take advantage of this to control the particles as they are heated.
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| By No machine-readable author provided. Webber assumed (based on copyright claims). [Public domain], via Wikimedia Commons |
Power production
Steam turbines It has been proposed that steam turbines be used to convert the heat from the fusion chamber into electricity. The heat is transferred into a working fluid that turns into steam, driving electric generators.
Neutron blankets Deuterium and tritium fusion generates neutrons. This varies by technique (NIF has a record of 3E14 neutrons per second while a typical fusor produces 1E5–1E9 neutrons per second). It has been proposed to use these neutrons as a way to regenerate spent fission fuel or as a way to breed tritium using a breeder blanket consisting of liquid lithium or, as in more recent reactor designs, a helium cooled pebble bed consisting of lithium bearing ceramic pebbles fabricated from materials such as Lithium titanate, lithium orthosilicate or mixtures of these phases.
Direct conversion This is a method where the kinetic energy of a particle is converted into voltage. It was first suggested by Richard F. Post in conjunction with magnetic mirrors, in the late sixties. It has also been suggested for Field-Reversed Configurations. The process takes the plasma, expands it, and converts a large fraction of the random energy of the fusion products into directed motion. The particles are then collected on electrodes at various large electrical potentials. This method has demonstrated an experimental efficiency of 48 percent.
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| Source: ASslides |
Economics
While fusion power is still in early stages of development, substantial sums have been and continue to be invested in research. In the EU almost €10 billion was spent on fusion research up to the end of the 1990s, and the new ITER reactor alone is budgeted at €6.6 billion total for the timeframe between 2008 and 2020.
It is estimated that up to the point of possible implementation of electricity generation by nuclear fusion, R&D will need further promotion totalling around €60–80 billion over a period of 50 years or so (of which €20–30 billion within the EU) based on a report from 2002. Nuclear fusion research receives €750 million (excluding ITER funding) from the European Union, compared with €810 million for sustainable energy research, putting research into fusion power well ahead of that of any single rivaling technology. Indeed, the size of the investments and time frame of the expected results mean that fusion research is almost exclusively publicly funded, while research in other forms of energy can be done by the private sector. In spite of that, a number of start-up companies active in the field of fusion power have managed to attract private money.
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| By Chris Bolin (Own work) [CC BY-SA (3.0)], via Wikimedia Commons |
Advantages
Fusion power would provide more energy for a given weight of fuel than any fuel-consuming energy source currently in use, and the fuel itself (primarily deuterium) exists abundantly in the Earth's ocean: about 1 in 6500 hydrogen atoms in seawater is deuterium. Although this may seem a low proportion (about 0.015%), because nuclear fusion reactions are so much more energetic than chemical combustion and seawater is easier to access and more plentiful than fossil fuels, fusion could potentially supply the world's energy needs for millions of years.
Despite being technically non-renewable, fusion power (like fission power using breeder reactors and reprocessing) has many of the benefits of renewable energy sources (such as being a long-term energy supply and emitting no greenhouse gases or air pollution) as well as some of the benefits of the resource-limited energy sources as hydrocarbons and nuclear fission (without reprocessing). Like these currently dominant energy sources, fusion could provide very high power-generation density and uninterrupted power delivery (because it is not dependent on the weather, unlike wind and solar power).
Another aspect of fusion energy is that the cost of production does not suffer from diseconomies of scale. The cost of water and wind energy, for example, goes up as the optimal locations are developed first, while further generators must be sited in less ideal conditions. With fusion energy the production cost will not increase much even if large numbers of stations are built, because the raw resource (seawater) is abundant and widespread.
Some problems that are expected to be an issue in this century, such as fresh water shortages, can alternatively be regarded as problems of energy supply. For example, in desalination stations, seawater can be purified through distillation or reverse osmosis. Nonetheless, these processes are energy intensive. Even if the first fusion stations are not competitive with alternative sources, fusion could still become competitive if large-scale desalination requires more power than the alternatives are able to provide.
A scenario has been presented of the effect of the commercialization of fusion power on the future of human civilization. ITER and later DEMO are envisioned to bring online the first commercial nuclear fusion energy reactor by 2050. Using this as the starting point and the history of the uptake of nuclear fission reactors as a guide, the scenario depicts a rapid take up of nuclear fusion energy starting after the middle of this century.
Fusion power could be used in interstellar space, where solar energy is not available.
Curiosity is the single most important attribute with which humans are born. More than a simple desire to discover or know things, curiosity is a powerful tool, like a scalpel or a searchlight. Curiosity changes us. It is also a way to effect change, perhaps even on a global level.