Tritium, 3-decay

Decay products of the principal radionuclides used in tracer technology (see Table 1) are not themselves radioactive. Therefore, the primary decomposition events of isotopes in molecules labeled with only one radionuclide / molecule result in unlabeled impurities at a rate proportional to the half-life of the isotope. Eor and H, impurities arising from the decay process are in relatively small amounts. Eor the shorter half-life isotopes the relative amounts of these impurities caused by primary decomposition are larger, but usually not problematic because they are not radioactive and do not interfere with the application of the tracer compounds. Eor multilabeled tritiated compounds the rate of accumulation of labeled impurities owing to tritium decay can be significant. This increases with the number of radioactive atoms per molecule. 

When the tritium (half-life 12.26 years) decays it is converted to the helium-3 isotope, which, of course, does not form covalent bonds, and so immediately departs, leaving behind the alkynyl cation. When this was done in the presence of benzene, RC CCgHs was isolated. The tritium-decay technique has also been used to generate vinylic and aryl cations. 

Small amounts of tritium were added to the hydrogen growth atmosphere of some crystals. Radiation detectors fabricated from these crystals measure the energy distribution of the electrons created in the tritium decays inside the crystal (Hansen et al., 1982). These studies set a lower limit of the hydrogen concentration at a value between 1014 cm 3 and 1015 cm-3. 

The short half-life of tritium imposes a time limit on the usefulness of tritium dating. However, because tritium decays to... 

Tritium and its decay product, helium, change the structural properties of stainless steels and make them more susceptible to cracking. Tritium embrittlement is an enhanced form of hydrogen embrittlement because of the presence of He from tritium decay which nucleates as nanometer-sized bubbles on dislocations, grain boundaries, and other microstructural defects. Steels with decay helium bubble microstructures are hardened and less able to deform plastically and become more susceptible to embrittlement by hydrogen and its isotopes (1-7). 

Figure 12. Fracture Appearance of Conventionally Forged Type 21-6-9 Steel after Exposure to Tritium Gas (5000 psi, 350°C) and Aged for Helium Build-In from Tritium Decay (a) 253 appm helium and (b) 627 appm helium. Arrows Indicate Direction of Crack Propagation.

D-Glutamic acid was not found in irradiated solutions of free L-glutamic acid, which agrees with the results of Sharpless et al. 83), who found no D-alanine in irradiated L-alanine. However, Evans 14) found that a major loss of L-leucine-4,5-T, methionine-T(G), and phenylalanine-4-T amino acids stored in aqueous solution occurs as a result of racemization. In these cases, it seems likely that the inversion is a result of indirect action brought about by 0-radiation from tritium decay. 

Upper limits on neutrino masses come from laboratory experiments, such as tritium decay and high-energy accelerator experiments, and are (see Review of Particle Physics, Hagiwara et al.(2002))... 

Tritium is hydrogen of mass number 3, having two neutrons and a proton in its nucleus. It is radioactive (half-life 12.4 years) in common with many isotopes having a large neutron-to-proton ratio, tritium decays with emission of an electron (called a beta ray). Such a decay can be represented by the nuclear equation (see also Chap. 27) ... 

This raised the problem of finding the probabilities of the excitations of the many-atomic valine molecule (64 electrons) caused by the j8 decay of a tritium nucleus. Earlier, the influence of the tritium / decay on the electron shell excitations was studied only for the simplest molecules. The most precise calculations were performed for HT by Wolniewicz (1965). However, the considered transitions were only those into the ground and the first excited states of HHe+. A number of selected electron transitions for molecules OHT, NH2T, and CH3T were calculated by Ikuta et al. (1977). A consistent analysis of all the aspects of the influence of ft decay on the electron shell rearrangement for different types of molecules was performed by Kaplan et al., (1982, 1983), who have also calculated the distribution of excitation probabilities and the / spectrum of the tritium-containing valine. 

Tritium is produced in the atmosphere by cosmic-ray spallation of nitrogen (Lai and Peters, 1967). Tritium decays to He with a half-life of... 

For a summary of the present knowledge of laser-induced photoacoustic spectroscopy, as regards theoretical backgrounds, instrumentation and radiochemical applications to particular problems in aquatic actinide chemistry, see Kim et al. (1990). Since there is no other radiochemical application known in the literature, except the measurement of tritium decay by an acoustic sensing technique, the present discussion is limited to application to actinide chemistry, particularly in aquatic systems. The most interesting field of application is and will be the geochemical study of long-lived... 

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). 

The emission of a negative (3-particle leaves the nucleus with one additional positive charge, a neutron is converted to a proton, and the nucleus assumes the next higher atomic number. Negative P-emission is characteristic of a nucleus that has more neutrons than required by its protons for stability. For example, tritium is an unstable isotope of hydrogen ( H), consisting of a proton, an electron, and two neutrons. When an atom of tritium decays, one of the neutrons is converted to a proton, one p-p article and one neutrino are released, and a helium isotope ( He) remains. Tritium is called a soft P-emitter, because its p-particles have relatively low velocities. A hard p-emitter, such diS phosphorus 32 ( P) is more hazardous because its p-p articles carry more kinetic energy however, it is easier to detect. 

Budget methods. Vertical exchange rates and turbulent diffusivities Kz can be calculated from the heat balance or the mass balance of tracers for which transformation rates are known. Assuming horizontal homogeneity, the temporal change of tracer mass below a given depth z must be the sum of the net vertical mass flux through the cross-section at z and all sources and sinks of tracer mass below z. In the case of conservative tracers sources and sinks below z must be mass fluxes across the sediment-water interface. In the case of H, radioactive decay is an additional sink. In the case of He, tritium decay represents a source. If the increase of mass due to all sources and sinks, Sm, is known, the net mass flux can be calculated ... 

Natural attenuation processes are always site-specific, so every site needs to be evaluated individually. The accepted mechanisms for inorganics, including radionuclides, are immobilization and/or biotransformation. For tritium, decay is acceptable. In most of the cases listed in Table 10.2, the attenuation process is only moderately understood. Although recognized as being important. 

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