Radioactivity of tritium

The second high-temperature study reviewed in Section 2 (Ichimiya and Furuichi, 1968) employed the radioactivity of tritium (3H) as a tool for measuring its uptake and retention in silicon wafers. This study yielded... 

The a-particles set free in radioactive disintegration take up electrons to form helium atoms. The gas is therefore associated with minerals containing a-emitters pitchblende ( U) andmonazite ( Th) are examples. Helium-3, though a stable nuclide, comprises only 1.4 x 10 % of natural helium it is a product of the radioactivity of tritium, itself a result of the action of cosmic rays on deuterium (p. 216) ... 

Alternatively, ore might pre-equilibrate the protein mo rcul. in a D7O buffer, and then dilute into H.-XD to follow the releasi- of exchangeable dfHitenum atoms This can also be done using the radioactivity of tritium-labelled water... 

For example, HT released from a plant is rapidly oxidized to HTO. Tritium water may be incorporated in organic matter as organically bound tritium (OBT) within tissues. The specific radioactivity of tritium in the form of CH3T in the atmosphere is very high, hut the reason is not understood. C may be released to the atmosphere as CO, CO2, CH4, HCHO, and COS. C02 released becomes incorporated into crops via photosynthesis leading to enhanced levels of C in crops. 

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 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. 

There should be specific, saturable binding to the receptor, accompanied by pharmacological characteristics appropriate to the functional effects, demonstrable using a radioactive, eg, tritium or iodine-125, ligand to label the receptor. Radioligand binding assays (1,6) have become a significant means by which to identify and characterize receptors and enzymes (see Immunoassays Radioactive tracers). Isolation of the receptor or expression of the receptor in another cell, eg, an oocyte can be used to confirm the existence of a discrete entity. 

Nuclear Magnetic Resonance. AH three hydrogen isotopes have nuclear spins, I 7 0, and consequently can all be used in nmr spectroscopy (Table 4) (see Magnetic spin resonance). Tritium is an even more favorable nucleus for nmr than is H, which is by far the most widely used nucleus in nmr spectroscopy. The radioactivity of T and the ensuing handling problems are a deterrent to widespread use for nmr. Considerable progress has been made in the appHcations of tritium nmr (23,24). 

Mass Spectrometer. The mass spectrometer is the principal analytical tool of direct process control for the estimation of tritium. Gas samples are taken from several process points and analy2ed rapidly and continually to ensure proper operation of the system. Mass spectrometry is particularly useful in the detection of diatomic hydrogen species such as HD, HT, and DT. Mass spectrometric detection of helium-3 formed by radioactive decay of tritium is still another way to detect low levels of tritium (65). Accelerator mass spectroscopy (ams) has also been used for the detection of tritium and carbon-14 at extremely low levels. The principal appHcation of ams as of this writing has been in archeology and the geosciences, but this technique is expected to faciUtate the use of tritium in biomedical research, various clinical appHcations, and in environmental investigations (66). 

Deuterium [7782-39-0] M 4. Passed over activated charcoal at -195° [Maciver and Tobin J Phys Chem 64 451 I960], Purified by diffusion through nickel [Pratt and Rogers, J Chem Soc, Faraday Trans 192 1589 1976], Always check deuterium for radioactivity to find out the amount of tritium in it (see D2O below). 

This reaction was studied by use of tritium. The phenylalanine was labeled with tritium at the 4-position of the phenyl ring. When the product, tyrosine, was isolated, it retained much of the original radioactivity, even though the 4-position was now substituted by a... 

The radioactive isotope tritium, 3H, is produced in nature in much the same way as 1fC. Its half-life is 12.3 years. Estimate the 3H ratio of the tritium of water in the area to the tritium in a bottle of vine claimed to be 25 years old. 

Table IV presents the results of the determination of polyethylene radioactivity after the decomposition of the active bonds in one-component catalysts by methanol, labeled in different positions. In the case of TiCU (169) and the catalyst Cr -CjHsU/SiCU (8, 140) in the initial state the insertion of tritium of the alcohol hydroxyl group into the polymer corresponds to the expected polarization of the metal-carbon bond determined by the difference in electronegativity of these elements. The decomposition of active bonds in this case seems to follow the scheme (25) (see Section V). But in the case of the chromium oxide catalyst and the catalyst obtained by hydrogen reduction of the supported chromium ir-allyl complexes (ir-allyl ligands being removed from the active center) (140) C14 of the...

All radioactive decay processes follow first-order kinetics. The half-life of the radioactive isotope tritium (3H, or T) is 12.3 years. How much of a 25.0-mg sample of tritium would remain after 10.9 years ... 

Measurement of the amount of tritium in the quenched samples was made by reheating them in a normal hydrogen ambient and measuring the evolved radioactivity. Since the samples contained tritium not only dissolved in the bulk crystal but also attached to the surface, mainly in a thin oxide film, measurements were made with and without removal of the latter by etching with HF, a procedure verified to remove the surface radioactivity. Their final results for the solubility s fell nicely on the Arrhenius line, ... 

The distribution of tritium in compounds 137-150 can be determined by tritium NMR spectroscopy without chemical manipulations115. The structure retention index relationship (SR IR)116 has been used for identification of unknown radioactive peaks and to differentiate by-products from radioimpurities from extraneous sources. 

Mix a small amount of tritium with the H2(g) and detect where the radioactivity appears. 

The radiochemical assays were done as follows At the end of a polymerisation experiment, when the conductivity had become constant, a ten-fold excess of tritiated water was added from a burette (see Figure 1), the cell was warmed rapidly to room temperature, and any polymer which had been precipitated during the polymerisation was allowed to re-dissolve. It was always noted that no hydrolysis occurred until the solutions reached 0 °C. This could be seen from a rapid drop of conductivity to a very low value. The solvent and most of the tritiated water were then distilled out, within about 15 minutes. The polymer was then dissolved in toluene, also run from a burette into the reaction vessel, which was then cut from the vacuum line. The polymer was precipitated in methanol and prepared for the determinations of radioactivity and DP. For the radiochemical assay the polymers were dissolved in toluene, re-precipitated in methanol, dried, weighed, re-dissolved in toluene, and the activity determined. The processes of precipitation and dissolution were repeated until the activity of the polymer became constant, (up to 7 repetitions). It was assumed that when the activity had become constant, all the excess of tritium had been removed. 

Let us assume that the binding constants for Ha+ and Ha are equal now, for a fixed quantity of Ha+ but an increased concentration of Ha. The ultimate impact would be that lesser Ha+ shall be bound. In actual practice, however, the use of Tritium (H3) or Carbon-14 (C14), which helps to render the Ha radioactive, ultimately maintains the equality of these binding constants, namely KHa+ and K[[a. It also confirms that the... 

The comprehensive dedicated research ultimately made it possible to decode the patterns of labelling in almost any type of tritium labelled compound at low isotopic abundance (e.g., 3 x 10 4 to 3 x 10 2 per cent. 3H per site) with the aid of 3H-NMR directly, rapidly, reliably and non-destructive analytical means. Since, 1971, the 3H-NMR spectroscopy, utilizing only millicurie (mCi) quantities of radioactivity, emerged as a most useful analytical tool for the study of tritium labelled compounds. 

The primary tritium KIE (k /l ) and the secondary tritium KIE ( h/ h) were determined in two different experiments carried out in the following way. If Ra is the radioactivity of the original reactant and / ROh is the radioactivity of ROH (ROT) determined at low (<5%) extents of reaction, the primary tritium KIE is given by equation (52). If the radioactivity of the styrene isolated at low extents of reaction, Rs, is also measured, the secondary tritium isotope effect can be calculated from (53). 

Radioactive or stable isotopes of noble gases are also used to determine vertical turbulent diffusion in natural water bodies. For instance, the decay of tritium (3H)— either produced by cosmic rays in the atmosphere or introduced into the hydrosphere by anthropogenic sources—causes the natural stable isotope ratio of helium, 3He/ 4He, to increase. Only if water contacts the atmosphere can the helium ratio be set back to its atmospheric equilibrium value. Thus the combined measurement of the 3H-concentration and the 3He/4He ratio yields information on the so-called water age, that is, the time since the analyzed water was last exposed to the atmosphere (Aeschbach-Hertig et al., 1996). The vertical distribution of water age in lakes and oceans allows us to quantify vertical mixing. 

Figure 7. Surface adsorption of tritium-labeled FMCG at pH 7.8. (O), in solution with no lipid added (Q), in solution with brain lipid added (A), dried sample, no lipid (A), dried sample, with brain lipid. Ordinates, radioactive c.p.m. X 10 2 for two lower curves (circles) and c.p.m. X 10 3 for two upper curves (triangles) abscissa, —log molar concentration of FMCG...

If one assumes, however, that tritium is scavenged in a similar manner as other radioactivity, then immediately following the detonation most of the tritium observed in the present ejecta profiles would have been in the missile ejecta stratum. This supposition is supported by the consistent pattern of tritium distribution with depth on the crater lip and at more distant stations where ejecta was deposited as a thin layer on undisturbed soil materials. 

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