Excitation functions of (n, α) reaction cross-sections for some important isotopes from threshold to 20 MeV
Research highlights
► Excitation functions for 53,42Ca, 57Fe isotopes having no entries in the EXFOR. ► Emphasis on Gilbert Cameron formalism for level density calculations. ► Suitability of Avrigeanu’s alpha potential for the (n, α) reaction cross-sections. ► Supports the ENDF/B-VI data library.
Introduction
The (n, α) reactions cross-section data is of paramount importance from the viewpoint of fusion and advanced fission reactor technology especially for calculations on nuclear transmutation rates, nuclear heating and radiation damage to the materials used in the construction of the core and inner walls of the reactor. Most of the (n, α) reaction cross-section data are available at ∼14 MeV. New nuclear energy system requires significant amount of new nuclear data in extended energy region and improvement of the presently available nuclear data. The present situation of (n, α) reaction cross-section data for the energy region from threshold to ∼20 MeV is still scanty and discrepant because preparing a mono-energetic neutron source for activation experiment in this energy region (except ∼14 MeV) presents some difficulties. Moreover, limitations of the activation technique to the stable products, unsuitable half lives and uncertain decay schemes account for the lack of the data. This lack of experimental data has to be compensated by the development of reliable calculation methods. EMPIRE-II code Herman et al. (2007) has opened up options for calculating cross-sections for various reaction channels. In this paper, we present model based calculations for (n, α) reaction cross-sections on isotopes which have been identified in IAEA nuclear data committee report INDC(SEC) – 95/URSF as priority isotopes for new nuclear energy generating systems.
Section snippets
Calculations
The cross-sections for (n, α) reactions on 42Ca, 50,53Cr, 56,57Fe, 58,62Ni, and 63,65Cu from threshold to ∼20 MeV have been calculated using the computer code EMPIRE-II which is a recent and versatile code for nuclear cross-section calculations. These cross-sections are theoretically calculated using full featured Hauser–Feshbach statistical model with preequilibrium and direct contributions. The nuclear structure input to the calculations like nuclear masses, discrete energy levels and level
Results and discussion
The results of the calculations are plotted in Fig. 1, Fig. 2, Fig. 3, Fig. 4, Fig. 5, Fig. 6, Fig. 7, Fig. 8, Fig. 9. The bell like shape of the excitations curves is typical characteristics of compound nucleus which rises abruptly above the reaction threshold and descends due to the competitive reactions and the increase of the preequilibrium contribution with neutron energy. For 42Ca, 53Cr, and 57Fe isotopes there are no entries in the EXFOR data library. The limitations of the activation
Conclusions
The present study done on the (n, α) reaction cross-sections for the isotopes of interest to nuclear fission and fusion reactors is thus significant in the context of the existing discrepant nuclear database available for these isotopes. The model based calculations of (n, α) reaction cross-sections of the nuclides performed in the present study showed that the Gilbert–Cameron formalism for level density calculations is appropriate in the energy range from threshold to 20 MeV for the studied
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