[en] Krypton and xenon isotopes, produced in the thermal neutron fission of ²³⁵U, were investigated by electromagnetic separation of chemically pure noble gases emanating from a uranium oxide-barium stearate target and introduced into an on-line mass-separator, the SOLIS. The separated isotopes were beta counted and the transfer function and half lives of the separated isotope and its precursor in the target were calculated. Two new isotopes ⁹³Kr and ¹⁴³Xe were detected and characterized by their half lives (0.2 + 0.02 and 0.3 + 0.03 sec, respectively). In gamma ray measurements, the prominent gamma peaks of ⁹³Kr and ⁹³Rb were identified and their relative intensities calculated. Relative, independent fission yields of the heavy isotopes of Kr and Xe were obtained by analyzing the beta decay curves obtained at similar operating conditions. For the lighter isotopes, e.g. ⁸⁷Kr, ¹³⁹Xe, absolute yields were obtained by calculating the ratio of cumulative yields of the halogen precursor to the independent yield of the noble gas, from curves describing the growth of beta activity as a function of irradiation time. The fission yields obtained in this work are systematically higher than those predicted by the ''normal'' Gaussian distribution suggested by Wahl. Since both Kr and Xe have even numbers of protons, it was suggested that the high yields are due to preservation of proton pairs in the fission of the even Z nucleus. Comparison of other published fission yields with the ''normal'' distribution showed an average enhancement of 22(+-7)% in the yields of even Z nuclei with a corresponding decrease in the yields of odd Z nuclei. (H.K.)

No abstract available

No abstract available

No abstract available

No abstract available

[en] A method for the exact determination of uranium in liquid and solid samples containing various main elements with Z <= 29 is described. The method is based on simultaneous measurements of the excited LX fluorescent energies of uranium and the backscattered energies of the iodine target used for excitation. ULsub(α)/ULsub(γ) and ULsub(ν)/IKsub(αsub(incoh))/U% peak intensities were found to be linearly dependent in samples of different chemical composition. Twenty eight liquid and solid samples of various matrices containing uranium in the range 0.3-30% were determined and a calibration line based on these measurements was obtained. Several samples containing different U concentrations were checked by this method and the average deviation of the calculated results from the known content is +- 12.5%. The X-rays were excited using a 10 mCi ²⁴¹Am/I source-target assembly and measured with a 25 mm² Si(Li) detector. (author)

[en] A method has been developed for the direct determination of uranium in carbonate solutions by X-ray fluorescence. Uranium, in the concentration range 0.2-50 ppm, is first absorbed as the carbonate complex on an anion exchange resin and then determined by X-ray fluorescence. A sensitivity corresponding to 20 ppb in 250 ml solution and a precision of +-6.5% was obtained. The sensitivity was 100-fold greater than that obtained by the direct determination in solution by X-ray fluorescence. (author)

No abstract available

[en] An analysis of the distribution of independent yields in neutron induced fission of ²³³U and ²³⁵U revealed a constant enhancement of products with an even number of protons, relative to those with an odd number. This odd-even effect in the proton pairing, related to calculated ''normal'' yields of elements in fission, constitutes a sawtooth structure with an amplitude of (22plus-or-minus7) % for both ²³³U and ²³⁵U thermal neutron induced fission. The residual neutron pairing effect evident after the emission of prompt neutrons, while it is insignificant (< 3%) in the light mass peaks, is partly preserved in the heavy mass peaks of both ²³⁵U and ²³³U thermal neutron fission products. Its average magnitude is about (8plus-or-minus5) % relative to the ''normal'' distribution of isotonic yields. In the fission of ²³⁵U with fission spectrum neutrons, the proton pairing effect drops to (8plus-or-minus4) %. The odd-even effect is discussed in view of the various mass splits, the excitation energy and potential energy surfaces in the descent from the saddle to the scission configuration

No abstract available