No abstract available

No abstract available

No abstract available

[en] A method for accurate measurement of the fission rate in the samples irradiated by neutrons from the T(p,n)³ He and D(d,n)³ He reactions is described. The method is based on the measurements of the fission rate in two fission chambers placed in the vicinity of the sample and Monte-Carlo calculations of fission rates in the sample and in the chambers' fissionable layers. The Monte-Carlo calculations employ a neutron source procedure taking into account most of the factors influencing on the neutron spectra characteristics in conditions of a real experiment. An experimental procedure developed for testing the proposed method is discussed. The performance of the method is demonstrated by the results obtained in the measurements of the total delayed neutron yields from neutron induced fission of ²³⁷Np and ²³⁵U. (author)

[en] The Delayed Neutron Working Group was established in April 1997 within the Nuclear Data Subcommittee of JNDC. It has two principal missions. One is to coordinate the Japanese activities toward the WPEC/Subgroup-6 efforts, and the other is to recommend the delayed neutron data for JENDL-3.3. The final report of Subgroup-6, which in one of the subgroups of the NEA International Evaluation Cooperation (WPEC) and is in charge of the delayed neutron data, is to be completed in 1999. Here in Japan, JENDL-3.3 is planned to be released in early 2000. Delayed Neutron Working Group is, then, going to finalize its activity by the end of the fiscal year 1999 after recommending appropriate sets of data as coherently as possible with the of Subgroup-6 efforts. (author)

[en] A least squares analysis of fission neutron standard fields has been performed using the latest dosimetry cross sections. Discrepant nuclear data are identified and adjusted spectra for ²⁵²Cf spontaneous fission and ²³⁵U thermal fission fields are presented

[en] The symmetric and asymmetric fission of the ⁵⁶ Ni and ⁴⁸ Cr rotating nuclei has been studied within the generalized liquid-drop model including the nuclear proximity energy. The selected shape sequence allows the rapid formation of a neck while keeping spherical ends. The potential barrier is a scission barrier standing at large deformations which hinders the fission process even at very high spins. Hyper-deformed minima appear at the foot of the fission barrier for sufficiently high angular momenta. These quasi-molecular configurations might correspond to some experimentally observed resonances at high angular momenta while, for lower spins, the fission barriers are sufficiently high and wide to allow fusion-fission phenomena

[en] The decay of radioactive nuclei which emit clusters like C, O, Ne, Mg and Si has been studied in the fission valley which leads a nucleus towards two touching nuclei before crossing the barrier. The energy has been calculated within a liquid drop model taking into account the proximity effects. The microscopic correlations has been introduced empirically to reproduce the experimental Q-values. The partial half-lives obtained within the WKB barrier penetration probability are in good agreement with the experimental data for all the clusters. The C, O, Ne, Mg and Si emission looks like a very asymmetric spontaneous fission through quasi-molecular shapes formed at the early stage of the tunneling process

[en] Fission and total level densities modelling approach was developed. Neutron-induced fission cross section data for incident energies from 10 keV up to emissive fission threshold were employed to extract level density and fission barrier parameters. In particular, fission barrier parameters (inner barrier height, outer barrier height, curvatures) were extracted for altogether 49 isotopes of Th, Pa, U, Np, Pu, Am, Cm, Bk, and Cf. The adopted level density modelling approach and fission barrier parametrization was supported by calculations of fission cross section data above the emissive fission threshold, up to 20 MeV neutron incident energy. (author)

[en] Review of works on nuclei decay, conducting in the Institute of Nuclear Physics of National Nuclear Center of Republic of Kazakstan is cited. It is noted, that on the first stages especial attention has been paid to study of integral and differential cross sections of nuclei decay. Beginning from the 1970 experimental information about mass-power distributions of nuclei fragments from Xe up to 103 is accumulated. Careful analysis of these data permitted essentially to extend knowledge about aspects of studied reaction. At last time works on study of low-energy fission within intermediate fields of nuclei A∼215-226 decay, as well as fission of wide class of nuclei, generated under fragmentation of ²³⁸ U with energy ∼0,5-1,9 GeV/nucleon on lead target are started