Tritium, enrichment

The cross section for the 3H(maximum value at only 107 KeV incident deuteron energy. When thick ( 1 mg cm-2 thick deposit of titanium) titanium-tritium targets are used, however, the neutron yield continues to increase even above 200 KV acceleration potential. This is due to increased penetration of the deuteron beam into the tritium enriched layer. Since the penetration of molecular deuterium ions is less than that for monatomic deuterium ions for the same acceleration potential, accelerators using Penning ion sources require extremely clean vacuum systems to minimize build-up of deuteron absorbing deposits on the surface of the target. 

C,2iS- H,3R]mevalonate, Bloxham and Akhtar showed that a tritium atom was lost whereas when [3a- H,26,27- C2]lanosterol was used the tritium was retained. The latter result was also observed by Hornby and Boyd. Presumably NAD is necessary for the oxidation at C-3 to a ketone prior to decarboxylation. Similarly, Miller and Gaylor showed that 4a-methyl-5a-cholest-7-en-3) -ol was oxidized only as far as the 4a-carboxylic acid, with retention of tritium at C-3 but loss from a 4a-C H3 group. In the latter case, the recovered 4a-methyl sterol showed no sign of tritium enrichment due to isotope effects. In banana, alkylation at C-24 seems to precede loss of the 4a-methyl groups. When the rat liver system was inhibited by cholestane-3, 5a,6 -triol, sterols accumulated which retained a methyl group at C-4. Both 4,4-dimethyl- and 4 -methyl-cholest-8-en-3/I-ol Uere isolated, and were shown to be converted into cholesterol under normal conditions. 

The weaponisation-related blocks in the top-level diagram involve such processes as the production of high explosives, tritium, enriched lithium and alpha-emitting radionuclides. The indicators will be largely comprised of equipment, material and environmental signatures. 

Either this synthesis or that shown in Scheme 16 is suitable for the preparation of C6 deuterated or tritated derivatives of L-ascorbic acid reducing 27 with deuterium or tritium enriched gas or with labeled sodium borohydride (51). 

Finally if the steps which lie between chanoclavine-I and proton removal are reversible and if proton abstraction is rate-limiting, the tritium enrichment of unreacted chanoclavine-I, which was observed in the above experiments, is also explained. (Loss of tritium is slower than loss of hydrogen as the result of a primary isotope effect.) So we now have a most satisfying rationale for the steps involved in the formation of the tetracyclic ergot alkaloids from chanoclavine-I. 

In autoradiography, the metal is typically charged with tritium-enriched hydrogen [91, 92]. The diffusible hydrogen is then removed by outgasing, and the... 

Over the years, a variety of fuel types were employed. Originally, natural uranium slugs canned in aluminum were the source of plutonium, while lithium—aluminum alloy target rods provided control and a source of tritium. Later, to permit increased production of tritium, reactivity was recovered by the use of enriched uranium fuel, ranging from 5—93%. 

Boron Bromide. Approximately 30% of BBr produced in the United States is consumed in the manufacture of proprietory pharmaceuticals (qv) (7). BBr is used in the manufacture of isotopicaHy enriched crystalline boron, as a Etiedel-Crafts catalyst in various polymerization, alkylation, and acylation reactions, and in semiconductor doping and etching. Examples of use of BBr as a catalyst include copolymerization of butadiene with olefins (112) polymerization of ethylene and propylene (113), and A/-vinylcarbazole (114) in hydroboration reactions and in tritium labeling of steroids and aryl rings (5). 

Production in Fission of Heavy Elements. Tritium is produced as a minor product of nuclear fission (47). The yield of tritium is one to two atoms in 10,000 fissions of natural uranium, enriched uranium, or a mixture of transuranium nucHdes (see Actinides and transactinides Uranium). 

The benefits of using ionic compounds in microwave-enhanced reactions led us to explore the possibility of using ionic solvents i.e. ionic liquids, as donors for both deuterium and tritium. Whilst D20 is now relatively inexpensive and available at high isotopic enrichment, tritiated water is usually employed, for safety reasons, at low isotopic incorporation (we typically use HTO at 5 or 50 Ci mLT1 specific activity corresponding to 0.2-2% isotopic incorporation). This is a serious limitation when there is a need to provide compounds at high specific activity. 

Groundwater age at each NGMP site has been assessed using multiple tracers. Tritium was analyzed in a 1 L unfiltered unpreserved sample using 70-fold electrolytic enrichment prior to ultra-low level liquid scintillation spectrometry (Morgenstern Taylor 2005). Samples for analysis of CFCs and SF6 (125 ml and 1 L, respectively) were collected in strict... 

Morgenstern, U. Taylor, C.B. 2005. Low-level tritium measurement using electrolytic enrichment and LSC. Proc. Int. Symp. Quality Assurance for Analytical Methods in Isotope Hydrology. International Atomic Energy Agency. 

In a subsequent study, Wacker et al.,80 using isotopically labeled uracils and chromatographic separation of products, report the yields of hydrate and dimer at several doses of ultraviolet light (Table II). The hydrate obtained at low doses was enriched in tritium by 45% (less enrichment at higher doses) it is not clear how this enrichment takes place, although the extra tritium must come from unhydrated uracil. 

As seen in Fig. 3.23, the absorption-desorption curves for H are different from those for D. This phenomena is used in types (3) and (4). By use of this phenomena, the separation of H and D, and enrichment of H and D from mixed gas are possible. The absorption-desorption curve for T (tritium) also differs from those for H and D thus we can separate and enrich H or D or T from the mixed gases by use of the absorption-desorption curves. D and T, which are used in nuclear reactors and nuclear fusion reactors, can be very efficiently separated and enriched by this principle. 

It is desirable to count tritium as methane since four atoms of hydrogen per mole of gas are present. At 10 atm. using the II counter, approximately one mole of water can be counted. The background count rate would be less than 5 c.p.m. in the tritium window. The sensitivity of this method would be about 1 TU without enrichment. 

Since the level of tritium in the atmosphere is presently greater than 10 TU, it is possible to study many physical and chemical processes using this equipment for sample analysis. Since isotopic enrichment is unnecessary for most samples, direct rapid analysis is possible. The equipment is being used presently to analyze water samples from Nevada in a hydrology project. Table IV shows the analytic data. No attempt has yet been made to evaluate these data. What is apparent qualitatively... 

---