Activation tritium

The introduction of tritium into molecules is most commonly achieved by reductive methods, including catalytic reduction by tritium gas, PH2], of olefins, catalytic reductive replacement of halogen (Cl, Br, or I) by H2, and metal pH] hydride reduction of carbonyl compounds, eg, ketones (qv) and some esters, to tritium-labeled alcohols (5). The use of tritium-labeled building blocks, eg, pH] methyl iodide and pH]-acetic anhydride, is an alternative route to the preparation of high specific activity, tritium-labeled compounds. The use of these techniques for the synthesis of radiolabeled receptor ligands, ie, dmgs and dmg analogues, has been described ia detail ia the Hterature (6,7). 

The conversion of high specific activity tritium-labeled fatty acids to n-alkanes one carbon unit shorter has been demonstrated in the American cockroach (26) and in the termite Zootermopsis angusticollis (27) in vivo, and in microsomal preparations from the termite (27). Most of the activity in the termite was located in the microsomal fraction and was stimulated two-fold by the addition of ascorbate. 

Benzodiazepines with reasonably high specific activity have been also tritium-la-belled165 using adsorbed tritium or activated tritium. These methods166,167 are fast and do not require one to synthesize the precursors. In the AcT (activated tritium) method the substrate to be labelled, spread on different catalyst supports (such as silica-alumina 980-25 containing 0.5% Ru, 1% Ni or 1% V alumina catalyst Al-3945, 1% Ni, 1% Pd or 5% Pd silica, 1% Ni and carbon, 4.6% Pd the metal catalysts were activated by heating to 600-700 °C in hydrogen or on untreated silica-alumina), has been reacted... 

H]-(168) labelled with activated tritium with substrate dispersed on multipore filter crude yield — 23 mCi purified yield — 2 mCi specific activity 562 mCi mmol-1... 

The total yearly production of neutron-activation tritium in the PWR coolant is 400 Ci, as shown in Table 8.10. Another source of tritium in the coolant is fission-product tritium that diffuses through the fuel cladding and escapes through pin-hold penetrations through the cladding. Estimates of the amount of fission-product tritium reaching the coolant in LWRs with zircaloy fuel range from 0.2 to 1 percent of the total fission-production tritium produced within the fuel. 

Tritium collection. Tritium in air is usually in the form of water vapor and less commonly in the elemental or organic-bound forms. It is generated in nature by cosmic-ray interactions, and at nuclear reactors and tritium-production facilities by ternary fission and neutron activation. Tritium as HT tends to oxidize to water vapor in air. Conversion to and from organic-bound tritium occurs in biota (NCRP 1979). 

The EPA s proposed drinking water standards for beta and photon emitters are limited to exposure of 4 mRem EDE/year (EDE, effective dose equivalent). Levels of strontium and tritium are determined by this method. The strontium method [15] covers the measurement of total strontium, including °Sr and Sr. Interferences from calcium and other radionuclides are removed by one or more precipitations of the strontium carrier as strontium nitrate. Barium and radium are removed as chromate. The daughter of °Sr is removed by a hydroxide precipitation step, and the separated combined Sr and Sr are counted for beta-particle activity. Tritium is determined by liquid scintillation counting after distillation [16]. 

OtherApphca.tlons. Many appHcations of adsorption involving radioactive compounds simply parallel similar appHcations involving the same compounds in nonradio active forms, eg, radioactive carbon-14, or deuterium- or tritium-containing versions of CO2, H2O, hydrocarbons. For example, molecular sieve 2eohtes are commonly employed for these separations, just as for the corresponding nonradio active uses. 

Eor products having relatively low specific activity, such as some compounds labeled with and which are synthesized on the scale of several millimoles, classical organic chemical separation methods may be utilized, including extraction, precipitation, and crystallization. Eor separation of complex mixtures and for products having high specific activity, such as those labeled with tritium, etc, chromatographic methods utilizing paper, thin... 

Other methods of sensitive detection of radiotracers have been developed more recently. Eourier transform nmr can be used to detect (nuclear spin 1/2), which has an efficiency of detection - 20% greater than that of H. This technique is useful for ascertaining the position and distribution of tritium in the labeled compound (14). Eield-desorption mass spectrometry (fdms) and other mass spectral techniques can be appHed to detection of nanogram quantities of radiolabeled tracers, and are weU suited for determining the specific activity of these compounds (15). 

Tritium has also been observed in meteorites and material recovered from sateUites (see also Extraterrestrial materials). The tritium activity in meteorites can be reasonably well explained by the interaction of cosmic-ray particles and meteoritic material. The tritium contents of recovered sateUite materials have not in general agreed with predictions based on cosmic-ray exposure. Eor observations higher than those predicted (Discoverer XVII and sateUites), a theory of exposure to incident tritium flux in solar flares has been proposed. Eor observations lower than predicted (Sputnik 4), the suggested explanation is a diffusive loss of tritium during heating up on reentry. 

Concentration by gas chromatography has also been demonstrated. Elution chromatography has been used on an activated alumina column to resolve the molecular species H2, HT, and T2, thereby indicating a technique for separation or concentration of tritium (54). This method was extended (55) to include deuterium components. The technique was first demonstrated in 1964 using macro quantities of all six hydrogen molecular species (56). 

Personnel are protected in working with tritium primarily by containment of all active material. Containment devices such as process lines and storage media are normally placed in well-ventilated secondary enclosures (hoods or process rooms). The ventilating air is monitored and released through tall stacks environmental tritium is limited to safe levels by atmospheric dilution of the stack effluent. Tritium can be efficiently removed from air streams by catalytic oxidation followed by water adsorption on a microporous soHd absorbent (80) (see Absorption). 

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). 

Use tite half-life of tritium given in Problem 53 to calculate the activity in curies of 1.00 mL of 3H2 at STP. 

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...

The constant half-life of a nuclide is used to determine the ages of archaeological artifacts. In isotopic dating, we measure the activity of the radioactive isotopes that they contain. Isotopes used for dating objects include uranium-238, potassium-40, and tritium. However, the most important example is radiocarbon dating, which uses the decay of carbon-14, for which the half-life is 5730 a. 

The age of a bottle of wine was determined by monitoring the tritium level in the wine. The activity of the tritium is determined to be 9.1 % that of a sample of fresh grape juice from the same region in which the wine was bottled. How old is the wine ... 

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