Helium-3, properties, production and application
Helium-3, properties, production and application.
Helium-3, 3He is a rare isotope. He has a promising application in the future as fuel in fusion reactors.
Helium-3 as fuel in a fusion reactor.
The advantages of helium-3 as fuel
Helium-3 is lighter of two stable isotopes of helium. The chemical formula of helium-3 – 3He.
A kernel of helium-3 (Helion) consists of two protons and one neutron, in contrast to helium-4 (4He), consisting of two protons and two neutrons.
The last (4He) is more common: it is, in fact, have 99,99986 % of helium on Earth. For helium-3 (3He) have 0,000137(3) % of helium on Earth.
Helium-3 as a particle refers to the fermions, because it has half-integral spin.
Helium-3 is mainly found in the Earth’s atmosphere, natural gas (0.5%) and in the mantle. The total number of helium-3 in the Earth’s atmosphere is estimated at around 35,000 tons.
On the Sun and giant planets atmospheres of helium-3 is much greater than in the Earth’s atmosphere.
Properties of helium-3:
|Atomic mass and. E. M.||3,0160293191(26)|
|The mass defect, Kev||14 931,2148(24)|
|Specific binding energy (per nucleon), Kev||2 572,681(1)|
|Isotope prevalence, %||0,000137(3)|
|Spin and parity of the nucleus||1/2+|
|The density of liquid 3He at boiling temperature and normal pressure (101 325 PA), g/l||59|
|The density of the 3He gas at normal conditions (T = 273,15 K = 0 °C, P = 101 325 PA), g/l||0,1346|
|The boiling point, To||3,19|
|A critical point To||3,35|
|The latent heat of vaporization, j/mol||26|
|The volume of one gram of 3He in normal conditions (T = 273,15 K = 0 °C, P = 101 325 PA), liters||Of 7.43|
|The superfluid state||at temperatures lower than 2.6 microns and at a pressure of 34 ATM.|
Currently, helium-3 extracted from natural sources.
It is produced in the decay of artificially produced tritium by bombarding neutrons of lithium-6 in a nuclear reactor. This way you can get up to 18 kg of helium-3 per year.
In view of the growing shortage of helium-3 considers economically feasible the production, as getting water in nuclear reactors, separation of the products of heavy-water nuclear reactors, production of tritium and helium-3 in particle accelerators, extraction of natural helium-3 from natural gas or atmosphere.
There is also a modern idea of mining helium-3 on the moon, where it is millions of tons in lunar soil – regolith. Ton of lunar soil (in the thinnest surface layer) contains about 0.01 g of helium-3 and 28 g of helium-4. The prevalence of the isotope helium-3 on the moon (~0,043 %) was significantly higher than in the earth’s atmosphere. In the lunar soil helium-3 has accumulated over many years by the irradiation of the lunar surface solar wind, in which it is contained. To extract helium-3 from lunar soil to be heated to several hundred degrees Celsius.
The use of helium-3:
– for filling gas meters-detectors of neutrons
– in the scientific laboratories to produce ultra-low millikelvin temperatures (about 0.02 K) by dissolution of liquid helium-3 in helium-4,
– as a fusion fuel in a fusion reactor (in the future).
Helium-3 as fuel in a fusion reactor:
Helium-3 is an excellent raw material for the reaction of thermonuclear fusion, unlike nuclear fission reactions. Unfortunately, a thermonuclear reactor based on the helium-3 is the subject of scientific development and its occurrence is not expected in the near future.
A nuclear reaction with helium-3 is as follows:
3He + 3He → 4He + 2p + 12,8 MeV,
3He + D → 4He + p + of 8.35 MeV
where D is deuterium, p – proton.
As a result of this fusion reaction produces a stable isotope of helium-4 (4He), the proton and a large amount of energy. While in the course of a nuclear reaction decay produces neutrons, which penetrate deeply into the surrounding structural materials, making them radioactive and destroy them. As a result, these materials must be periodically (a few years) to bury and replace with new. Protons, which are the result of nuclear fusion involving helium-3, on the contrary, do not penetrate deeply into the surrounding materials and does not induce radioactivity. Therefore, these materials and structures can serve for decades.
In General, the above reaction is accompanied by radiation, but it (the reaction) is 50 times less radioactive than nuclear fusion, e.g. deuterium with tritium.
Nuclear reaction of deuterium with tritium is described as follows:
2H + 3H → 4He + n + 17,6 MeV,
where 2H – deuterium, 3H – tritium, n is neutron.
The disadvantage of the reaction of deuterium with tritium is that tritium itself is highly radioactive. Second, during this reaction there is a strong neutron radiation.
The energy efficiency of helium-3 as fuel in the thermonuclear fusion is very huge. So, 1 ton of helium-3 replaces about 15-20 million tons of oil. Annual demand for helium-3 is around 20-30 tons, and of all mankind – 200 tons.
The advantages of helium-3 as fuel:
it is an ecologically pure thermonuclear fuel, by itself, helium-3 is non-radioactive and storage requires no special precautions
– high energy efficiency,
instead of the neutrons the reactor in the helium-3 emits protons, unlike neutrons are easily captured and can be used for additional power generation, for example, in the MHD generator,
– the kinetic energy of the protons is directly converted into electricity through solid-state transformation
reactor based on helium-3 has lower operating costs than traditional
– in case of failure of reactor depressurization of the active zone, the radioactivity emissions are close to zero.
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