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2015 - 20172
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Subject: Physics × Author: Pandey, Hem Chandra × End date: 2017 ×
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    ThesisItemOpen Access
    Fission cross-sections of important actinides produced in the TH-U fuel cycle
    (G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand), 2017-07) Pandey, Hem Chandra; Agarwal, H.M.
    Accurate measurement of neutron induced fission cross-section data are essential in designing the future fission reactors. In the present work, neutron induced fission cross-sections are calculated for different isotopes of Thorium, Protactinium and Uranium (232Th, 231,232,233Pa, 232,233,234,235,236U) which produces in the Th – U fuel cycle. The calculations were done with EMPIRE 3.1 Nuclear code, which is based on various theoretical model and number of FORTRAN codes, reference input parameter libraries (RIPL) and experimental data library (EXFOR). The comparison of (n, f) reaction cross-sections calculated using the barrier parameters obtained by the analytical barrier formula are more reliable and supported by the experimental and evaluated results. The fission barrier height values of various radionuclides, taken from RIPL-1, RIPL-2 and RIPL-3 produces the experimental and evaluated data poorly for the studied actinides. Thus, it is concluded from the results of the present work that the precise measurement of the barrier heights is very important to predict the fission cross-section data accurately.
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    ThesisItemOpen Access
    Excitation function of nuclear reactions relevant to nuclear technology from threshold to 20 MEV
    (G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand), 2015-07) Pandey, Hem Chandra; Agrawal, H.M.
    The neutron interaction cross-section in the energy range below 20 MeV is of fundamental importance for advanced reactors (fission and fusion), Breeder Reactors and GEN-IV reactors. A theoretical understanding of nuclear phenomenon has reached to a considerable degree of reliability, and nuclear models are used increasingly to supplement and extend the nuclear data base that is required for several applications. More recently, the theoretical understanding of nuclear reactions have been further developed and nuclear reaction models refined to the extent that with appropriate parameterization, nuclear models can be used for inter-and extrapolation and for consistency checks of experimental cross-section data, and for reasonably accurate prediction of “unmeasurable data”. The present work consistes of opting suitable nuclear level density model, optical model potential, pre-equilibrium model and in carrying out Hauser-Feshbach statistical model based calculations of cross-sections (n,p), (n,α) and (n,2n) reactions on rare earth nuclides( Sm, Eu, Gd, Dy and Yb), which are important for neutron shielding, reactor control and storage of spent nuclear fuel. The level density and pre-equilibrium emission plays an important role in determining the cross-sections. Therefore, we have studied the effect of different level density formalism and pre-equilibrium emission on (n,p), (n,α) and (n,2n) reactions using code TALYS-1.4. It is found that the different types of nuclear level density are appropriate for different types of particle emission reactions. Pre-equilibrium contribution dominates in (n,p) and (n,α) reaction whereas in (n,2n) reactions the compound nucleus contribution dominates in all the studied rare earth cases. We have also analyzed the (n,p) and (n,α) reactions cross-sections of long lived target and residual nuclei of Cr, Cu, Fe, Ni and V which are main constituents of structural and blanket materials of fission, fusion reactors with recent code TALYS-1.4. There is a significant contribution of pre-equilibrium emission in (n,p) and (n,α) reactions cross-section as confirmed by double differential cross-section(DDX) at 14 MeV neutron energy. The consistency of calculated results is also checked by experimental data and systematics at 14.7 MeV. It is concluded that the present results contribute substantially to improving the knowledge of the cross-sections by optimizing the input parameters required in model based evaluation of cross-sections at higher energies which are essential to support new nuclear energy systems.