Band 2, Heft 4

A Monte Carlo calculation has been performed to evaluate the yields expected from the kinetic theory of hot atom reactions for various combinations of parameters. The calculations here have been performed for the elastic, isotropic model and for an isotropic, pseudoelastic model in which the maximum energy loss is treated as a free parameter. The total hot yield, Y , is given for a pure Compound with sufficient accuracy to be useful by the formula Y = 1 - exp (- I/α ). The hot yield from recoil tritium reaction with A diluted by helium is approximately given by Y A = 1 - exp( -ƒ A I A /α AB ). This formula falls to describe recoil tritium behavior in other inert gases because of changing values of α AB in the reactive chemical range.

Zusammenfassung An den nach ( n, γ ) - und ( n, 2n)-Reaktionen in metallorganischen Verbindungen des Germaniums isolierten chemischen Rückstoßprodukten wurden Isotopie-Effekte beobachtet. Bei der Bestrahlung von Getetraphenyl mit thermischen Neutronen konnten Verschiebungen im 71 Ge/ 77 Ge-Isotopenverhältnis sowohl an der festen (bis zu 9%) als auch an der in Cyclohexan bzw. Benzol gelösten Verbindung (bis zu 8%) gemessen werden; außerdem auch an flüssigem Gie-diphenyl (bis zu 6%). Die beim ( n, 2n )-Prozeß an kristallinem Ge-tetraphenyl gefundenen 69 Ge/ 75 Ge-Isotopenverhältnisse zeigen ebenfalls deutsche Verschiebungen (bis zu 10%). Der Eifekt scheint bei der Bestrahlung im festen Zustand stärker als im flüssigen ausgeprägt zu sein. Die möglichen Ursachen für das Zustandekommen des beobachteten Isotopie-Effektes werden diskutiert.

The yield of organically bound radio-bromine was determined in a wide range of mixtures of benzene, hexane, cyclohexane, tetradecane and bromoform with molecular bromine. The data was analysed by applying the kinetic theory of hot reactions to these liquid systems. After a number of drastic assumptions it was found possible to express the data in terms of two parameters: a) the reactivity integral (/) and b) the collisional energy loss ( α ). The validity of the independently obtained parameters ( α and I ) was checked by the determination - both experimentally and theoretically - of the organic yield of hot reactions in mixtures of bromoform and benzene. The values found for the α ’s indicate that moderating collisions with hydrocarbon involve the whole molecule, whereas with halocarbons the collisions have more of an atom-atom character.

Separation of microamounts of ruthenium from fission product mixtures in 0.2-0.8 M•HNO 3 by extraction with molten naphthols was studied with respect to the composition of individual mixtures and to naphthol amounts. The values of ruthenium distribution ratios depend on the molar ratios naphthol: ferric ions and naphthol: mercuric ions. The radionuclides 106 Ru, 90 Sr, 144 Ce, and 137 CS were used for the test trials.

Reactor Irradiation of natural osmium leads to osmium-194 by second order neutron capture. When converted to osmium tetroxide, millicurie amounts of carrier-free iridium-194 can be recovered repeatedly from the decay of a Single sample of osmium-194 by vacuum distillation. The half-life of pure iridium-194 was found to be 17.4 ± 0.1 hours.

Zirconium is extracted at pn ~ 6 in presence of 10 -3 MH 2 O 2 with a benzene Solution of fatty acids (C 7 - C 9 ; 1M). Niobium is masked by hydrogen peroxide. Coextraction of niobium with zirconium in weighable amounts was observed.

Experiments on the adsorption and Sedimentation of yttrium solutions have been carried out with solutions containing minimal suspended matter. It has been shown that such clean solutions of 'carrierfree' yttrium can be kept in polystyrene vessels, even at pH = 8 or more, with no Sedimentation taking place, and only a small amount of adsorption on to the vessel walls. It has also been shown that addition of 'Analar' water to such solutions converts the yttrium to a centrifugable form. It is suggested that the 'radiocolloidal' properties of yttrium reported in the literature are due to ion exchange adsorption of yttrium ions on to suspended particulate matter and on to surfaces.

The properties of the beta and gamma radiation emitted by the 2.8 hours 190 Re are studied. The possibility is discussed that this activity may be due to an excited State of the nuclide.

Résumé On propose une méthode de routine pour doser successivement la somme des activités 95 Zr- 95 Nb par spectrométrie gamma, puis l’activité du 95 Zr par spectrométrie béta sur scintillateur plastique. Les activités sont déterminées par comparaison á un mélange étalon dont on connaît l’évolution des deux activités. Cette méthode nous dispense de l’emploi de sources étalons des radioéléments purs. On a mesuré la valeur des interférences dues au 95 Nb et 95m Nb au cours du dosage du 95 Zr. La précision et les seuils de détection d’un des éléments dans l’autre sont indiqués. La durée totale de l’opération pour un essai en double est inférieure à, 4 heures.

Zusammenfassung Die Zählraten von Flüssigkeitsszintillator-Probenlösungen mit Metallsalzen sind oft nur kurze Zeit konstant, weil die Aktivität an der Probenflasche adsorbiert wird. Auch bei Verbindungen, in denen die Metall- Nuklide komplex gebunden sind, treten Zählverluste auf. Sie lassen sich vermeiden, wenn man der Probe Träger oder dem Szintillator hochdisperses Sillciumdioxid zusetzt. Trägerzusatz kann nachteilig sein, wenn sich stark farbige oder im Szintillator unlösliche Verbindungen bilden.