Study of Neutron Nuclear Data Relevant to Incineration of Transuranium Elements

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Nuclear data evaluation system based on adequate nuclear fission models was developed and applied for important actinides in order to provide basic data for the study of incineartion of transuranium nuclides.1.Evaluation of Fission Neutron Spectrum : New evaluation system for fission spectra was developed on the basis of the non-equitemperature Madland-Nix model previously proposed by the author. The special feature of the system is the following : : (a) Systematics of the fragment mass distribution was used to estimate the average fragment nucliders ; (b) Nuclear level density parameters a with inclusion of the shell effects were obatined by using the Ignatyuk model in stead of simple linear approximatio of the type a=A/C(A : mass number, C : adjustable parameter) ; (c) The total energy release of fission was calculated using the mass formula of Tachibana et al. ; (d) The energy dependence of the inverse cross section was taken into consideration ; (e) The total fission probability was decomposed into first-to fourth-chance fission components and the fission spectra from each stage were calculated to form the total spectrum. This system was used to provide evaluated fission spectra for U-233, -235, -238, Pu-239, Np-237, Am-241 etc.Analysis of Energy Dependence of Fission Neutron Multiplicity : The average fission neutron multiplicities for actinides were calculated using the above system. It was found that the results are dependent on the neutron binding energy data used as input.Analysis of Fission Cross Sections : A code was developed to break down the total fission cross section into its constituent (n, f)-, (n, nf)-, ・・・, (n, 4nf)-components. This program was applied in the procedure 1. (e) above.