[en] Dicyclohexano-18-crown-6 (DC18C6), dissolved in chloroform, 1-octanol, toluene or cyclohexane, was irradiated by ⁶⁰Co γ-rays. Radiolytic destruction of DC18C6, measured by gas chromatography, decreased in the order: chloroform > cyclohexane > 1-octanol > toluene. Distribution coefficients in the solvent extraction of strontium from nitric acid solution were measured. These distribution coefficients were minimally affected by γ-irradiation in toluene solution, but decreased with the absorbed dose in chloroform solution. It was suggested that the distribution coefficient for the liquid-liquid extraction system was influenced by radiolytic products. The effect of radiolytic products on the distribution coefficients was evaluated by considering DC18C6 remaining in the organic phase after irradiation. The distribution coefficient measured for the organic phase with radiolytic products was larger than that without radiolytic products. The radiolytic products were thus shown to contribute to the increase in the distribution coefficient

[en] It has previously shown that the Li isotopes are effectively separated by chemical exchange methods using crown ethers or cryptands. In a liquid-liquid extraction system, the single factor separation factors for the Li isotopes vary largely depending on lithium salts, while almost the same factors have been observed in the chemical exchange reaction between cryptand-lithium complex and methanol solution of lithium halides. The difference between these methods is suggested to arise from the difference in solvation effects between water and ethanol solutions. The solvation effect would be suppressed if a less polar solvent is employed for a lithium salt. Observations are made for LiCl, LiBr and LiI, and results obtained indicate that for all counter anions, separation factors (α's) decrease with increasing ratio of water to methanol. In the case of 100 % methanol solvent, α's are almost the same value (1.04) regardless of the counter anions, while in 100 % water solvent, α's are 1.012, 1.008 and 1.005 for LiI, LiBr and LiCl, respectively. These processes are analyzed on the assumption that the lithium salt dissolves in a paired state or in a completely dissolciated state in 100 % methanol solution and 100 % water solution, respectively. It is suggested that higher separation factor can be attained by using an anion with more electron donating property. One of the candidates is chelating anion which has been investigated for crystalline structure of lithium-salt-crown-ether complex. (Nogami, K.)

[en] Measurements of tritium concentration in various media have been successfully performed by detecting with an ordinary NaI(Tl) scintillation counter the bremsstrahlung emitted from tritium decay. To distinguish meaningful signals from noises emanating mainly from thermoelectrons present in the phototube, differences in rise time were discriminated by means of an electronic circuit, instead of separation by pulse height analysis. This pulse-shape discriminator successfully reduced noise counts below 18 keV in a multichannel analyzer from 100 cpm to 4 cpm, which permitted direct counting of tritiated water as dilute as 1 μCi/ml, without requiring any complicated preparation. (auth.)

[en] Molybdenum isotopes were fractionated in a liquid-liquid extraction system using dicyclohexano-18-crown-6 (DC18C6). The enrichment factors showed a breakdown of the conventional mass-dependent rule. Some unusual and larger isotope effects were observed in the even atomic mass isotopes, ⁹²Mo and ⁹⁴Mo. The unusual features in the present study were not responsible for the field shift effect, which was regarded as a primary factor of the anomalous isotope effect in the recent theory, but were due to an anomaly on the vibrational levels. The largest isotope effect was observed in the isotope pair of ⁹⁴Mo-⁹⁶Mo, it was ε_96,94 = 0.0086 ± 0.0007, its initial aqueous phase was 0.91 M molybdenum chloride, and its organic phase was 0.2 M DC18C6 in chloroform: this was 0.0043 ± 0.0004 in terms of the enrichment factor for unit mass different. (author)

No abstract available

[en] Isotope effects of some elements in chemical exchange reaction were investigated by use of liquid-liquid extraction, liquid membrane or chromatographic separation. Cyclic polyether was used for every method. All polyethers used in a series of the studies were made clear that they distinguished the isotopes not only by their nuclear masses but also by their nuclear sizes and shapes. Chromium isotopes, for example, were recognized to have enrichment factors being proportional to δ< r²> which is a parameter to show field shift or the nuclear size and shape of the isotope. It follows that the chromium isotopes are separated not by their masses but by their field shift effects. Nuclear spin also played a great role to separate odd mass number isotopes from even mass number isotopes in even atomic number elements. Contribution of the nuclear spin (I=3/2) of ⁵³Cr to total enrichment factor, ε_53/52 = -0.00028, for ⁵³Cr to ⁵²Cr was observed to be, ε_spin = -0.0025. (author)

[en] Lithium isotopes were separated effectively using a liquid membrane system composed of benzo-15-crown-5. The separation factor of the system was 1.066 for a ratio isotopic composition in a receiving phase to a source phase. Lithium enriched with ⁶Li accumulated continuously in the receiving phase at a rate of 9.5 mg/hr. The liquid membrane system was shown to work favorably under the conditions such that the difference between the separation factor at the source/membrane interface and that at the receiving/membrane interface is large. (author)

[en] Liquid-liquid extractive separation of lithium isotopes was carried out in order to investigate the fluctuation of separation factors (a) as a function of salt concentrations in an aqueous phase. Two equations for separation factor (a_obs) as a function of the concentration were introduced; one for the diluted region, and another for the concentrated region. In the former solution where hydrated lithium ions are predominant, 1n a_obs = Ac + B, and in the latter where ion-pairs with anions are predominant, 1n a_obs = Dc + E(c - F)^1/3 + G. Some guidelines are derived from the salt-specific constants A, B, D, E, F and G. The heavier isotopes are inclined to be in the more hydrated state in the diluted solution, while the lighter isotopes tend to be in a less hydrated state. In the concentrated solution, heavier isotopes are more likely to be in ion-pair form. Ionic association occurs from the lower concentration in the order of LiI < LiBr < LiCl. The anion having the stronger ionic interaction with the cation has more ability to distinguish the isotope. (author)

[en] Tritium is produced by binary and ternary fission in fast breeder reactors. Moreover, tritium is produced by nuclear reaction of boron and litium with neutron. Some of the produced tritium diffuse from primary coolant to the circumstance through the cover gas or secondary coolant and steam generator, therefore it is necessary to develop the removal techniques of tritium from sodium and to evaluate precisely the circumferential radioactivity. The literature survey of tritium behaviour in liquid metal was carried out in order to develop above mentioned techniques, and examined about these contents. The contents of the report is classified in to following four items. (1) The behaviour of tritium in sodium (2) The behaviour of tritium in lithium (3) Instrumentation, analysis and monitoring of tritium (4) Storage of krypton which affect seriously to the atmospheric radioactivity. (auth.)

[en] The isotopic enriching process of the nickel isotopes by the liquid-liquid extraction using a crown ether of dicyclohexano-18-crown-6 was investigated. The nickel chloride exists simply as the aqua complex in the aqueous phase, not as the chloro complex even in the concentrated salt solution. The extraction reaction is supposed to be, Ni²⁺(6H₂O)+L+2Cl^-=NiLCl₂+6H₂O, where L represents the crown ether, and Ni²⁺(6H₂O) and NiLCl₂ denote the 6 hydrated nickel ion and the crown ether complex of nickel, respectively. The unit mass enrichment factor, ε_u=0.0017-0.0026 was small compared with that of zinc isotopes. The odd/even isotope effect was recognized to be as large as ε_O/E=0.018. The enrichment factor was reviewed at the correlation with the isotope shift of atomic spectra and the hyperfine structure splitting of ⁶¹Ni. (author)