Tritium, nuclear fusion

The ordinary isotope of hydrogen, H, is known as Protium, the other two isotopes are Deuterium (a proton and a neutron) and Tritium (a protron and two neutrons). Hydrogen is the only element whose isotopes have been given different names. Deuterium and Tritium are both used as fuel in nuclear fusion reactors. One atom of Deuterium is found in about 6000 ordinary hydrogen atoms. 

Helium-3 [14762-55-1], He, has been known as a stable isotope since the middle 1930s and it was suspected that its properties were markedly different from the common isotope, helium-4. The development of nuclear fusion devices in the 1950s yielded workable quantities of pure helium-3 as a decay product from the large tritium inventory implicit in maintaining an arsenal of fusion weapons (see Deuterium AND TRITIUM) Helium-3 is one of the very few stable materials where the only practical source is nuclear transmutation. The chronology of the isolation of the other stable isotopes of the hehum-group gases has been summarized (4). 

Tritium is produced in heavy-water-moderated reactors and sometimes must be separated isotopicaHy from hydrogen and deuterium for disposal. Ultimately, the tritium could be used as fuel in thermonuclear reactors (see Fusionenergy). Nuclear fusion reactions that involve tritium occur at the lowest known temperatures for such reactions. One possible reaction using deuterium produces neutrons that can be used to react with a lithium blanket to breed more tritium. 

It has been claimed that the D-D fusion reaction occurs when D2O is electroly2ed with a metal cathode, preferably palladium, at ambient temperatures. This claim for a cold nuclear fusion reaction that evolves heat has created great interest, and has engendered a voluminous titerature filled with claims for and against. The proponents of cold fusion report the formation of tritium and neutrons by electrolysis of D2O, the expected stigmata of a nuclear reaction. Some workers have even claimed to observe cold fusion by electrolysis of ordinary water (see, for example. Ref. 91). The claim has also been made for the formation of tritium by electrolysis of water (92). On the other hand, there are many experimental results that cast serious doubts on the reahty of cold fusion (93—96). Theoretical calculations indicate that cold fusions of D may indeed occur, but at the vanishingly small rate of 10 events per second (97). As of this writing the cold fusion controversy has not been entirely resolved. 

Nuclear Fusion Reactions. Tritium reacts with deuterium or protons (at sufftciendy high temperatures) to undergo nuclear fusion ... 

The confinement region in which nuclear fusion proceeds is surrounded by a blanket in which the neutrons produced by the fusion reaction are captured to produce tritium. Because of its favorable cross section for neutron capture, lithium is the favored blanket material. Various lithium blanket... 

It IS often stated that unclear fusion tvill produce no radioactive hazard, but this is not correct. The most likely fuels for a fusion reactor would be deuterium and radioactive tritium, which arc isotopes of hydrogen. Tritium is a gas, and in the event of a leak it could easily be released into the surrounding environment. The fusion of deuterium and tritium produces neutrons, which would also make the reactor building itself somewhat radioactive. However, the radioactivity produced in a fusion reactor would be much shorter-lived than that from a fission reactor. Although the thermonuclear weapons (that use nuclear fusion), first developed in the 1950s provided the impetus for tremendous worldwide research into nuclear fusion, the science and technology required to control a fusion reaction and develop a commercial fusion reactor are probably still decades away. 

Deuterium occurs naturally, mixed m with plain hydrogen in the tiny proportion of 0.015 percent in other words, plain hydrogen is the more common isotope by a factor of 6,600. Tritium for fusion energy can be created from another nuclear process involving the interaction of the neutron (in the equation above) with lithium ... 

Another approach to nuclear fusion is shown in Figure 19.6. Tiny glass pellets (about 0.1 nun in diameter) filled with frozen deuterium and tritium serve as a target. The pellets are illuminated by a powerful laser beam, which delivers 1012 kilowatts of power in one nanosecond (10 9 s). The reaction is the same as with magnetic confinement unfortunately, at this point energy breakeven seems many years away. 

As seen in Fig. 3.23, the absorption-desorption curves for H are different from those for D. This phenomena is used in types (3) and (4). By use of this phenomena, the separation of H and D, and enrichment of H and D from mixed gas are possible. The absorption-desorption curve for T (tritium) also differs from those for H and D thus we can separate and enrich H or D or T from the mixed gases by use of the absorption-desorption curves. D and T, which are used in nuclear reactors and nuclear fusion reactors, can be very efficiently separated and enriched by this principle. 

A potential major source of energy for the mid- to late-21st century is nuclear fusion. In todays experimental fusion reactors, deuterium and tritium atoms (both isotopes of hydrogen) fuse to create helium and fast-flying neutrons. The neutrons escape from the reaction chamber, carrying with them vast amounts of kinetic energy. 

In all the nuclear equations we have just written, we have shown that there is no change in the sum of the mass numbers. However, there actually is a small change in mass, and this change is one of the most important properties of nuclear reactions. Consider the nuclear fusion of hydrogen and tritium ... 

In a thermonuclear or hydrogen bomb, a significant fraction of the energy release occurs by nuclear fusion rather than nuclear fission. The hydrogen isotopes, 2H (deuterium, D) and 3H (tritium, T), can be made to fuse, as ... 

The simplest nuclear fusion reaction is the combination of the isotopes of hydrogen (deuterium and tritium) to form the heavier nucleus of helium. 

The gas is also used to fill balloons, in gas discharge lamps, and as an additive in the breathing gases of astronauts and scuba divers. The rarer stable isotope of helium (3He) is produced by the decay of radioactive tritium, and is used in resonance imaging and in the attainment of very low temperatures, about 0.010 kelvin, via a process known as dilution refrigeration. see also Noble Gases Nuclear Fusion. 

Deuterium (2D) and tritium (3T) are heavier isotopes of hydrogen. The former is stable and makes up about 0.015 per cent of all normal hydrogen. Its physical and chemical properties are slightly different from those of the light isotope Tl For example, in the electrolysis of water H is evolved faster and this allows fairly pure D2 to be prepared. Tritium is a radioactive b-emitter with a half-life of 12.35 years, and is made when some elements are bombarded with neutrons. Both isotopes are used for research purposes. They also undergo very exothermic nuclear fusion reactions, which form the basis for thermonuclear weapons (hydrogen bombs) and could possibly be used as a future energy source. 

This process, often called a nuclear fusion, has been found to be self-sustaining if a mixture of deuterium and tritium is detonated by the high temperature produced by a nuclear fission bomb. 

Based on the value of the tritium content in atmospheric hydrogen, tritium has been produced by nuclear fusion in the upper layers of the atmosphere, and does not take part in any atmospheric circulation, but instead remains as elementary hydrogen. ... 

High-temperature hydrogen plasmas, in addition to being a key component in energy projects of the nuclear fusion reaction using deuterium and/or tritium, have also been studied as agents for chemical reactions. 

Many of the papers appearing about uranium hydride in the last few years are concerned with technical problems arising from the possibility of its use for storing tritium as UT3 in connection with nuclear fusion devices. Several papers on these topics can be found in ref (336). From the chemical point of view, perhaps the most interesting study was the demonstration, using He NMR, that the He formed by tritium decay soon forms microscopic gas bubbles rather than being trapped in octahedral interstitial sites. The two situations can be expected to lead to very different relaxation times (337-340). 

Major efforts are now under way to achieve controlled nuclear fusion as a source of energy. One approach is based on the reaction between deuterium and tritium atoms,... 

The rewards of a workable nuclear fusion process would be great. Fusion produces neither the long-lived radioactive nuclides that accompany nuclear fission (although tritium requires care in handling) nor the environmental pollutants released by the burning of fossil fuels. Although deuterium is present in only 1/6000 of the abundance of ordinary hydrogen, its separation from the latter by the electrolysis of water is readily accomplished, and the oceans contain a virtually unlimited quantity of deuterium. 

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