Tritium

Tritium [15086-10-9] the name given to the hydrogen isotope of mass 3, has symbol or more commonly T. Its isotopic mass is 3.0160497 (1). Moletecular tritium [10028-17-8], is analogous to the other hydrogen isotopes. The tritium nucleus is energetically unstable and decays radioactively by the emission of a low-energy P particle. The half-life is relatively short (- 12 yr), and therefore tritium occurs in nature only in equiUbrium with amounts produced by cosmic rays or man-made nuclear devices. 

Tritium was first prepared in the Cavendish Laboratory by Rutherford, OHphant, and Harteck in 1934 (2,3) by the bombardment of deuterophosphoric acid using fast deuterons. The D—D nuclear reaction produced tritium ( D-H D — -H energy), but also produced some He by a 

Tritium is the subject of various reviews (6—8), and a book (9) provides a comprehensive survey of the preparation, properties, and uses of tritium compounds. Selected physical properties for molecular tritium, are given in Table 1. 

Calculated vapor pressure relationships of T2, HT, and DT have been reported (10) (see Deuteriumand tritium,deuterium). An equation for the vapor pressure of soHd tritium in units of kPa, Tin Kelvin, has been given (11)  

The three-phase region of D2—DT—T2 has been studied (12). Relative volatilities for the isotopic system deuterium—deuterium tritide—tritium have been found (13) to be 5—6% below the values predicted for ideal mixtures. 

Tritium (Table 9.1) occurs in the upper atmosphere and is formed naturally by reaction 9.5, involving neutrons arriving from outer space. Tritium (see Section 2.8) was first obtained synthetically by the bombardment of deuterium compounds such as [ND4]2S04 with fast neutrons, but is now prepared from lithium deuteride, LiF or Mg/Li enriched in 3Li (equation 9.6). 

Tritium is radioactive, a weak 3-emitter with h = 12.3 yr. It is used extensively as a tracer, in both chemical and biochemical studies its weak radioactivity, rapid excretion and failure to concentrate in vulnerable organs make it one of the least toxic radioisotopes. 

Tritium is the third hydrogen isotope. It was prepared for the first time in 1934 by Ernest Rutherford. The isotope takes its name from the Greek word tritos, the third. The tritium nuclide is unstable and emits 3-radiation. It is formed during nuclear reactions in the upper atmosphere by a reaction between nitrogen and neutrons in the 

Tritium arrives at the earth s surface in rain and is present as HTO in the hydrological cycle. The natural tritium content is, however, very low, 1 atom T in 10 atoms of hydrogen. The atmospheric testing of nuclear weapons during the 1950s and 1960s made the contents considerably higher. Tritium is itself an important constituent of 

Tritium has some peaceful use for research purposes. Organic compounds can be marked with tritium, which is the basis for a method of studying the course of chemical reactions. 

Tritium was first prepared by nuclear transmutation, defined as the conversion of one element into another by a nuclear process. Rutherford, in addition to all his other contributions to chemistry and physics, was the first to carry out the alchemists dream. In 1919 Rutherford was still working with his alpha particles, this time shooting them into various gases. When he used nitrogen gas, the results indicated 

Tritium is produced in a similar fashion both naturally and artificially. Although the natural concentration of tritium is exceedingly small (10 in about 10 hydrogen atoms), it is produced in the upper atmosphere by the reaction represented in Equation (10.20)  

Here neutrons from cosmic rays bombard the nitrogen of the upper atmosphere, producing carbon-12 and tritium. The tritium makes its way down to the Earths surface as precipitation, probably in the form of compounds such as HTO (water with one regular hydrogen replaced by a tritium atom). Because the half-life of tritium is only 12.3 years, its concentration in the oceans is much less than it is in rainwater. During the early 1950s when atmospheric testing of nuclear weapons was carried out, the concentration of tritium in rainwater reached about 500 atoms/10 atoms. 

Tritium is produced in nuclear reactors by the bombardment of hthium-6 with neutrons [Equation (10.21)]  

Lithium is usually incorporated into a magnesium or aluminum alloy that is placed into a fission reactor where it is bombarded with neutrons. 

As was described in Section 3.2.1., tritium is produced in irradiated nuclear fuel as a product of the ternary fission of and Pu with the comparatively 

In addition, the experimental difficulties involved in the analytical determination of very low concentrations of a pure P emitter of low energy in the presence of a large excess of other P , y—active radionuclides have to be mentioned. Since a direct radiation measurement of the activity in such a mixture is not possible, a sophisticated radiochemical separation has to be performed the details of which will be summarized below. The same problems arise in the determination of the content in irradiated nuclear fuel. On the other hand, both radionuclides show similar chemical and radiation properties so that their determination can be carried out using similar analytical procedures. 

Both and C are pure p emitters without associated y transition, with their beta maximum energies amounting to 0.02 and 0.2 MeV, respectively. This means that their determination requires careful separation from virtually all other radionuclides prior to radiation measurement taking into account that their activity concentrations in irradiated nuclear fuel are small compared to that of the other fission products, only expensive separation procedures will lead to reliable results. Often these procedures are further complicated by the requirement that different chemical forms of the radionuclides have to determined in parallel (e. g. HT— HTO, C02- C0- CH4). In such cases one additionally has to take care that no change from one chemical state to another occurs during the analytical procedure. 

After radiochemical separation, the following radiation measurement techniques can be applied  

Concerning selectivity and detection limits, these three techniques do not exhibit great differences. Therefore, the selection of the counting technique to be applied is usually dictated by pragmatic aspects such as optimum combination with the separation technique applied or the type of counting instrumentation available. 

There exist many reliable reports of tritium production in cold fusion experiments for the Pd/D system [3-5]. However, the amounts of tritium production are always too small 

It is obviously of importance for these studies to have a variety of means available for the incorporation of tritium into organic molecules. This is done using catalytic systems and is where the subject takes on a particular interest to the organometallic chemist. Indeed, the high sensitivity of H NMR makes it an ideal tool for the study of surface catalysis, an area of research which has already been reviewed, or for the mechanistic study of metal catalyzed reactions. Tritiation can be carried out with 

Mantsch, H. H. Saito, H. Smith, I. C. P. Progr. NMR Spectrosc. 1977, 11, 211 E. A. Evans etal, John Wiley, Chichester and New York, 1985. 

Nuclear Magnetic Resonance, Specialist Periodical Reports of the Royal Society of Chemistry London, Vols. 1-11 and onward. 

Progress in NMR Spectroscopy, Emsley, J. W., Feeney, J. and Sutcliffe, L. H., Eds. Pergamon New York, Vols. 1-13 and onward (first volume 1966). 

Many methods have been used to determine the deuterium eontent of hydrogen gas or water. For H2/D2 mixtures mass speetroseopy and thermal eonduetivity ean be used together with gas ehromatography (alumina aetivated with manganese ehloride at 77 K). For heavy water the deuterium eontent ean be determined by density measurements, refraetive index ehange, or infrared speetroseopy. 

The main uses of deuterium are in traeer studies to follow reaetion paths and in kinetie studies to determine isotope effeets. A good diseussion with appropriate referenees is in Comprehensive Inorganic Chemistry, Vol. 1, pp. 99-116. The use of deuterated solvents is widespread in proton nmr studies to avoid interferenee from solvent hydrogen atoms, and deuteriated eompounds are also valuable in struetural studies involving neutron diffraetion teehniques. 

Tritium differs from the other two isotopes of hydrogen in being radioaetive and this immediately indieates its potential uses and its method of deteetion. Tritium oeeurs naturally to the extent of about 1 atom per 10 hydrogen atoms as a result of nuelear reaetions indueed by eosmie rays in the upper atmosphere  

The eoneentration of tritium inereased by over a hundredfold when thermonuelear weapon testing began on Bikini Atoll in Mareh 1954 but has now subsided as a result of the ban on atmospherie weapon testing and the natural radioaetivity of 

Numerous reaetions are available for the artifi-eial produetion of tritium and it is now made on a large seale by neutron irradiation of enriehed Li in a nuelear reaetor  

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Tritium is readily produced in nuclear reactors and is used in the production of the hydrogen bomb. 

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. 

Deuterium is used as a moderator to slow down neutrons. Tritium atoms are also present but in much smaller proportions. Tritium is readily produced in nuclear reactors and is used in the production of the hydrogen (fusion) bomb. It is also used as a radioactive agent in making luminous paints, and as a tracer. 

Melander first sought for a kinetic isotope effect in aromatic nitration he nitrated tritiobenzene, and several other compounds, in mixed acid and found the tritium to be replaced at the same rate as protium (table 6.1). Whilst the result shows only that the hydrogen is not appreciably loosened in the transition state of the rate-determining step, it is most easily understood in terms of the S 2 mechanism with... 

Even isotopes qualify as different substituents at a chirality center The stereo chemistry of biological oxidation of a derivative of ethane that is chiral because of deu terium (D = H) and tritium (T = H) atoms at carbon has been studied and shown to... 

Triton (tritium nucleus) t Wien displacement constant b... 

The italicized symbols d- (for deuterium) and t- (for tritium) are placed after the formula and connected to it by a hyphen. The number of deuterium or tritium atoms is indicated by a subscript to the symbol. 

Isotopically Labeled Compounds. The hydrogen isotopes are given special names H (protium), H or D (deuterium), and H or T (tritium). The superscript designation is preferred because D and T disturb the alphabetical ordering in formulas. 

A few natural isotopes are radioactive. Of the three isotopes of hydrogen, only that of mass 3 (tritium) i.s radioactive. Radioactive isotopes can be examined by other instrumental means than mass spectrometry, but these other means cannot see the nonradioactive isotopes and are not as versatile as a mass Spectrometer. 

A simple example occurs with hydrogen, which occurs naturally as three isotopes (hydrogen, deuterium, tritium), all of atomic number 1 but having atomic masses of 1, 2, and 3 respectively. 

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