Moderator effects on recoil tritium reactions with lithium beta-phenylpropionate

The recoil tritium reactions were studied with lithium beta-phenylpropionate having both the aromatic and aliphatic C-H bonds in the molecule, mainly in terms of the moderator effect on the intramolecular tritium distribution. Recoil tritium atoms were produced by the 6Li(n,alpha)3H reaction. Water molecules were used as the moderator. The tritium activity of the ethylene group represented relative to that of the corresponding ring assumed as a standard (= 100) is 30 in the moderator-free system and is reduced to 13 in the moderated system in which the H2O/beta-PhC2H4CO2Li mole ratio is 328. In the ring, the tritium distribution shows a slight ortho- and para-orientation in the moderator-free system and the selectivity is pronounced when the H2O/beta-PhC2H4CO2Li mole ratio is large. The data show that the aromatic ring tritiation in the moderated system is given by increasing contribution of the reactions of tritium atoms having lower energy than the threshold energy of the ethylene group tritiation.     

Chemical effects on ArF excimer laser irradiated surfaces of single crystalline lithium niobate

Single crystalline lithium niobate was irradiated by ArF excimer laser and the surface morphological changes were observed. It was found that various deffects occured in dependence on the laser beam energy density and the number of pulses. Delayed formation of microcracks was observed, which can be explained by the chemical reaction of LiNbO₃ with atmospheric water.     

Profiling lithium distribution in Sn anode for lithium-ion batteries with neutrons

Measuring the distribution of lithium in high capacity lithium-ion battery (LIB) electrodes is essential to understanding the coulombic losses during the lithiation/delithiation processes that occur while charging and discharging the cell. In this research, two half-cell prototypes were fabricated by electrochemically lithiating Sn foil anodes in 1M LiBF₄ in a 1:1 (wt:wt) ethylene carbonate and dimethyl carbonate solutions at a constant potential of 0.50 and 0.67 V (vs. Li/Li⁺). The neutron depth profiling (NDP) technique was employed to study the Li distributions in the anodes. Li concentration profiles were resolved for the samples lithiated under different conditions for LIB studies. In addition, this paper demonstrated an in situ NDP measurement of an electrochemical cell with a thin window design, which reveals the dynamics of lithium distribution within the Sn anode.     

On the reactivity of recoil tritium with organic compounds

The reactivity of recoil tritium in the T-for-H substitution was studied in mixtures of benzene, hexane, cyclohexane or cyclohexane-d₁₂ with lithium carbonate which were irradiated in a reactor. The relative rates per C–H bond of hexane and cyclohexane to benzene were somewhat less than one third. The H/D isotope effect in cyclohexane was given as 1.14.     

Radiochemical separation of cerium from natural uranium irradiated with thermal neutrons

The extraction of cerium from uranium fission products using different concentrations of di(2-ethylhexyl)-phosphoric acid (DEHPA) and varying concentrations of nitric acid solutions was studied. Cerium was quantitatively stripped from the organic phase with 6N HNO₃ after washing with 0.01N HCl. The gamma-ray spectra were obtained with a Ge(Li) detector and recorded in a 4096-channel pulse-height analyzer.     

Radiochemical separation of99Mo from natural uranium irradiated with thermal neutrons

⁹⁹Mo was separated from uranium and insoluble fission product hydroxides. More than 98% of⁹⁹Mo radioactivity was extracted with bis (2-ethylhexyl)phosphoric acid. The organic phase was washed and⁹⁹Mo was back-extracted from the organic phase with NH₄OH solution. The percent recovery from the organic phase was 91% and the purity of⁹⁹Mo was more than 99%. Pure^99mTc was also extracted from the organic phase with a saline solution. Reversed-phase partition chromatography was used for the purification of⁹⁹Mo from¹³¹I and other fission products (10% HDEHP on kieselguhr bed).¹³¹I and other isotopes were quantitatively eluted with 0.1M H₂SO₄,⁹⁹Mo was eluted using a mixture of 0.5 M HCl and 30% H₂O₂.     

Recovery of uranium from U3O8 irradiated with thermal neutrons

The extraction of uranium with different concentrations of HDEHP in n-hexane from varying concentrations of nitric acid solutions was investigated. Uranium in the organic phase was quantitatively stripped with a solution containing 8M H₂SO₄ and 6M HCl, the partition coefficient was determined by X-ray fluorescence and U. V. spectrophotometry. The assay of⁹⁵Zr,⁹⁵Nb,²³⁹Np and other gamma-emitters was made with a Ge(Li) detector coupled to a 4096 multichannel analyzer.     

Selective dehalogenation and hydrogenation of compounds in adsorption layers with tritium gas

Selective dehalogenation and hydrogenation were observed in treating the corresponding precursors supported on a heterogeneous carrier with tritium gas. This technique was used to obtain tritium-labeled 3′,3,5-triiodothyronine, dihydrofusicoccin terpenoid (DHF), and 3-(piperidine-4-yl)-1,4-dihydroquinazoline-2-on with a molar radioactivity of 0.76, 2.3, and 6.5 PBq/mol, respectively.     

High temperature solid state catalytic isotope exchange with deuterium and tritium

A method for synthesizing tritium- or deuterium-labeled amino acids, peptides and biogenic amines through high temperature solid state catalytic isotope exchange (HSCIE) is proposed. The dependence of the degree of isotope exchange in HSCIE on the structure of the compound, the reactivity of hydrogen at different carbon atoms and the conditions of the process has been examined. If HSCIE is performed in the temperature range of 373 to 413K, the selectivity of isotopic label incorporation comes to 70% or higher. When the tritium label is introduced into peptides, they retain the configuration of asymmetric atoms, even upon the substitution of tritium for hydrogen at the -carbon atoms of the amino acid residues. HSCIE at 453–513K leads to an even distribution of the isotopic label over the organic compound molecule. The results of³H NMR spectroscopy highlighting the distribution of the tritium label in the organic compound molecules are presented. The configuration of asymmetric atoms in amino acids is preserved to a high extent upon 80–90% substitution of isotopes for hydrogen atoms.Presented at the 12th Radiochemical Conference, Marianské Lazné May 7–11, 1990.     

All-electron calculations with plane waves in solid lithium hydride

Calculations of the directional Compton profiles and the anisotropies of Compton scattering are reported, based on the density functional theory in the local density approximation, performed in the plane-wave basis, and using full, unscreened Coulomb potentials for both Li and H atoms. It is shown that converged results can be obtained without employing pseudopotentials, and the Compton profiles obtained are in excellent agreement with experiment. The influence of correlation on Compton profiles in LiH is found to be very weak. Possibilities (and limits) of extending the plane-wave calculations with the full Coulomb potentials to other atoms and substances are discussed. © 1997 John Wiley & Sons, Inc.     

Hydrogen molecules trapped in irradiated solid ethanol

Raman spectroscopy of γ-irradiated solid ethanol at 77 K revealed that trapped H₂ is produced mainly by the H atom abstraction at the alkyl group by H radicals which are dissociated from the alkyl group of ethanol. Comparison of the peak wavenumbers and the band widths of H₂ between the glassy and crystalline phases of ethanol suggests that the trapping sites of H₂ in the glassy phase are smaller in the average size and less homogeneous in the size distribution. The molar ratio between ortho- and para-H₂ trapped in irradiated crystalline ethanol is in rough agreement with the thermodynamic equilibrium between 5–120 K, intimating that the ortho-para conversion is allowed under the existence of an electro-magnetic gradient due to paramagnetic radicals.     

Theoretical study of two possible occupation sites for tritium atoms in lithium titanate

Tritium breeder materials are fundamental to the development of a fusion reactor. One of the materials under investigation is lithium titanate, which has a good thermal stability, high density of lithium and low activation under irradiation, which are the fundamental properties that are demanded from this type of materials. However, there are little data on physical and chemical properties, which are necessary in order to design a material with the best characteristics to be used in a fusion reactor. We present a theoretical investigation on possible occupation sites for tritium atoms in lithium titanate structure using ab initio Hartree–Fock method. Two possible substitutional Li sites were identified for a tritium atom: one in the titanium layer and the other in the lithium layer. This study showed that the tritium released would favorably occupy positions in lithium layers than in titanium layers. Tritium occupying sites in titanium layers would require more energy to release in comparison to lithium layers. An interesting relation is seen between these results and experimental data.     

Enrichment reliability of solid polymer electrolysis for tritium water analysis

We have developed a novel advanced enrichment apparatus for environmental tritium analysis called SPET (Solid Polymer Electrolysis for Tritium Water). It generates no explosive gas, requires no aqueous electrolyte, terminates enrichment rapidly, and the volume reduction is infinite. It has an automatic shutdown system which gives uniform conditions on every run, making the handling and determination of tritium concentrations very easy. The reliability of SPET was studied using environmental concentration standard water and the reproducibility error was found to be within 4%, which is sufficient for environmental measurements.