Tritium fusion fuel

Violante, V., Basile, A., and Drioh, E., Composite catalytic membrane reactor analysis for water gas shift reaction in the tritium fusion fuel cycle, Fus. Eng. Design, 217-223, 30, 1995. 

Almost as interesting is the role of lithium s lighter stable isotope, 6Li, in the production of the hydrogen bomb. The crucial tritium is produced by bombarding 6Li with neutrons 6Li + n -> 3H (tritium) + 4He. The radioactive tritium (3H) is a major fusion fuel when reacting with deuterium (2H) in the thermonuclear bomb. Because Li effectively absorbs neutrons it is also useful for neutron-shielding devices. 

Tritium is a very sensitive subject for public acceptance of fusion and will play a central role in the operation of a next-step experimental fusion facility, which will routinely use large amounts of tritium as fuel (e.g., 100 times more in ITER than in present experiments) in a mixture with deuterium. Tritium retention is a regulatory issue since the amount that can potentially be released in an accident sets the limits on plasma operation without removal. Fuel economy has never been an issue in deuterium-fuelled experiments and only recently have the limitations associated with the use of tritium, and its incomplete recovery in experiments in TFTR and in JET, brought the issue of fuel retention under closer scrutiny [56,57]. Table 12.3 provides a list of key quantities related to tritium in existing tokamaks and a next-step device [18,57-59]. 

Even though neutrons carry as much as 80% of the D-T fusion energy, the need to breed tritium limits the fraction of the D-T fusion energy that is convertible to HT heat source to about 30% up to 40% (See references in Refs. 48 and 49). Since they are not required to breed tritium, neutrons originating from alternate fusion fuel cycles can deposit most of their energy in the HT zone. Table VII compares estimates for the fraction of energy liberated in different fusion fuel cycles that could be converted, via neutrons, into HT heat[39,42]. 

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. 

A D—T fusion reactor is expected to have a tritium inventory of a few kilograms. Tritium is a relatively short-Hved (12.36 year half-life) and benign (beta emitter) radioactive material, and represents a radiological ha2ard many orders of magnitude less than does the fuel inventory in a fission reactor. Clearly, however, fusion reactors must be designed to preclude the accidental release of tritium or any other volatile radioactive material. There is no need to have fissile materials present in a fusion reactor, and relatively simple inspection techniques should suffice to prevent any clandestine breeding of fissile materials, eg, for potential weapons diversion. 

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. 

The development of a tritium fuel cycle for fusion reactors is likely to be the focus of tritium chemical research into the twenty-first century. 

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. 

Separation of 6Li from natural abundance (7.4%) feed to synthesize 6LiD (an important component of the fuel used in hydrogen fusion weapons (hydrogen bombs)). This, because the (n,T) cross section for 6Li is much larger than that of 7Li, so production of tritium is much enhanced in the triggering explosion. 

The fission of one mole of uranium-235 produces more energy than the fusion of one mole of deuterium with one mole of tritium. What if you compare the energy that is produced in terms of mass of reactants Calculate a ratio to compare the energy that is produced from fusion and fission, per gram of fuel. What practical consequences arise from your result ... 

This reaction is a fusion reaction. It shows two light nuclei combining to form one heavy nucleus. This reaction fuels the sun. The two hydrogen reactants are atypical because they re rare isotopes of hydrogen, called tritium and deuterium, respectively. 

Fusion energy offers a number of advantages over all other energy sources, including fission. Fusion reactors do not produce air pollutants that contribute to global warming or acid rain. The deuterium fuel they use is available in essentially unlimited supply from seawater, and tritium can be generated on-site as... 

D. We will still be using fossil fuels, oil, gas and coal, but their usage will be curtailed because there will have been a dramatic increase of harnessing of solar energy, wind energy, fusion and fission energy, and other sources. We propose that fusion reactors may become the usable energy source of choice, because of minimum problems of disposal and because of uses of the fissionable products (tritium). These are less of a security risk than fission products (which are plutonium and uranium). 

Next-step D-T burning fusion reactors, such as the International Thermonuclear Experimental Reactor (ITER), will require several kilograms of tritium [1,2]. While most of the tritium will be contained in the fuel process loop, the interaction of the plasma with plasma-facing components (first-wall armour, limiters, and divertors) will lead to accumulation of tritium in the torus. Based on the amounts and distribution of D retention in TFTR and... 

The Li nucleus can absorb a fast (above 3 MeV) neutron to produce a tritium nucleus, an alpha particle, and a slower neutron. A moderated neutron can be absorbed by a Li nucleus to produce a tritium and an alpha. Neutronic calculations indicate that a thick sphere of natural lithium could breed about 1.8 tritium atoms for each tritium atom burned in a fusion reaction (1 ). Structure and portions of the volume left open for fueling or driver beams reduce the 1.8 tritium breeding ratio. If the ratio falls below 1.0, it may be increased by addition of a neutron multiplier such as Be or Pb, and by isotopically enriching the Li in °Li. 

The production of fusion energy would begin, of course, with fuel. In a fusion reactor, the most promising fuels are deuterium and tritium, the heavy isotopes of hydrogen, both of which can be extracted from seawater. Deuterium s potential as a plentiful energy source is easily understood when one considers that a small amount can produce the equivalent of some 300 gallons of gasoline when it is burned off. 

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