E. Tel

A new empirical formula for 14–15 MeV neutron-induced (n, p) reaction cross sections

In this study, we have suggested a new empirical formula to reproduce the cross sections of the (n, p) reactions at 14–15 MeV for the neutron incident energy. This formula obtained using the asymmetry parameters represents a modification to the original formula of Levkovskii. The resulting modified formulae yielded cross sections, representing smaller χ2 deviations from experimental values, and values much closer to unity as compared with those calculated using Levkovskiis original formula. The results obtained have been discussed and compared with the existing formulae, and found to be well in agreement, when used to correlate the available experimental σ(n, p) data of different nuclei.

PRE-EQUILIBRIUM EMISSION IN DIFFERENTIAL CROSS-SECTION CALCULATIONS AND ANALYSIS OF EXPERIMENTAL DATA FOR 232Th

In this study, neutron-emission spectra produced by (n,xn) reactions on nuclei 232Th have been calculated. Angle-integrated cross-sections in neutron induced reactions on targets 232Th have been calculated at the bombarding energies from 2 MeV to 18 MeV. We have investigated multiple pre-equilibrium matrix element constant from internal transition for 232Th(n,xn) neutron emission spectra. In the calculations, the geometry dependent hybrid model and the cascade exciton model including the effects of pre-equilibrium have been used. Pre-equilibrium direct effects have been examined by using full exciton model. In addition, we have described how multiple pre-equilibrium emissions can be included in the Feshbach–Kerman–Koonin (FKK) fully quantum-mechanical theory. By analyzing (n,xn) reaction on 232Th, with the incident energy from 2 MeV to 18 MeV, the importance of multiple pre-equilibrium emission can be seen clearly. All calculated results have been compared with experimental data. The obtained results have been discussed and compared with the available experimental data and found agreement with each other.

Spallation neutron emission spectra in medium and heavy target nuclei by a proton beam up to 140 MeV energy

In this study, neutron-emission spectra produced by (p,xn) reactions for some spallation neutron target nuclei such as (65)Cu, (204,206,207,208)Pb, (209)Bi, (232)Th and (238)U have been calculated by a proton beam up to 140 MeV. Multiple pre-equilibrium mean free path constants from internal transition for (204,208)Pb (p, xn) neutron emission spectra have been investigated. In the calculations, pre-equilibrium effects were calculated by using new evaluated hybrid model and geometry dependent hybrid model, full exciton model and cascade exciton model. The reaction equilibrium component was calculated by Weisskopf-Ewing model. The obtained results have been discussed and compared with the available experimental data and found agreement with each other.

Effect of different structural materials on neutronic performance of a hybrid reactor

Selection of structural material for a fusion–fission (hybrid) reactor is very important by taking into account of neutronic performance of the blanket. Refractory metals and alloys have much higher operating temperatures and neutron wall load (NWL) capabilities than low activation materials (ferritic/martensitic steels, vanadium alloys and SiC/SiC composites) and austenitic stainless steels. In this study, effect of primary candidate refractory alloys, namely, W-5Re, T111, TZM and Nb–1Zr on neutronic performance of the hybrid reactor was investigated. Neutron transport calculations were conducted with the help of SCALEu20094.3 System by solving the Boltzmann transport equation with code XSDRNPM. Among the investigated structural materials, tantalum had the worst performance due to the fact that it has higher neutron absorption cross section than others. And W-5Re and TZM having similar results showed the best performance.

Application of asymmetry depending empirical formulas for (p,nα) reaction cross-sections at 24.8 and 28.5 MeV incident energies

In this study, we have investigated the asymmetry term effect for the (p,n alpha) reaction cross-sections and we have obtained new coefficients for the (p,n alpha) reactions at 24.8 and 28.5 MeV energies. We have suggested empirical formulas including the new coefficients found by fitting two parameters for proton induced reactions. The coefficients were determined by least-squares fitting method. The obtained cross-section formulas with new coefficients have been discussed and compared with the available experimental data.

The equilibrium and preequilibrium neutron-emission spectra of some structural fusion materials for (n, xn) reactions up to 16 MeV energy

In this study, neutron-emission spectra produced by (n, xn) reactions for some structural fusion materials as 27Al, 51V, 52Cr, 55Mn, and 56Fe have been investigated by a neutron beam up to 16 MeV. Multiple preequilibrium mean-free-path constant from internal transition and the preequilibrium and equilibrium level-density parameters have been investigated for some (n, xn) neutron-emission spectra calculated in this study. Preequilibrium neutron-emission spectra were calculated by using new-evaluated hybrid model and geometry-dependent hybrid model, full-exciton model, and cascade-exciton model. The reaction equilibrium component was calculated by Weisskopf-Ewing model. The obtained results have been discussed and compared with the available experimental data and found agreement with each other.

New calculation method for initial exciton numbers on nucleon induced pre-equilibrium reactions

In this study, we investigate the pre-equilibrium effect by using new evaluated geometry dependent hybrid model for the {sup 208}Pb (p,xn) reaction at 25.5 and 62.9 MeV incident proton energies. We also suggest that the initial neutron and proton exciton numbers for the nucleon induced precompound reactions be calculated from the neutron and proton density by using an effective nucleon-nucleon interaction with Skyrme force. We calculate the initial exciton numbers obtained from SKM* and SLy4 for a proton induced reaction on target nuclei {sup 208}Pb. The obtained results have been investigated and compared with the pre-equilibrium calculations and experimental results.

Investigation of coulomb and pairing effects using new developed empirical formulas for proton-induced reaction cross sections

We have investigated Coulomb and pairing effects by using new empirical formulas including the new coefficients for (p, α) at 17.9 MeV, (p, np) at 22.3 MeV, and (p, nα) at 24.8 and 28.5 MeV energies. A new formula is obtained by adjusting Levkovskii’s original asymmetry parameter formula and also Tel et al. formula for proton-induced reactions. The new coefficients by using least-squares fitting method for the reactions are determined. In addition, the findings of the present study are compared with the available experimental data.

Investigation of neutron and proton distributions of He, Li, and Be isotopes using the new Skyrme-Force parameters

The proton and neutron densities, root-mean-square (rms) radii of proton density and neutron density, and neutron skin thickness of 4–10He, 6–11Li, and 7–12Be isotopes are calculated using Skyrme-Hartree-Fock method with SLy4, SLy5, SLy6, and SLy7 force parameters. The evaluated results are compared with experimental data. Also, the results of halo nuclei (6,8He, 11Li, and 11Be) are compared with the results of other isotopes for selected nuclei having the same neutron configuration.

CALCULATION OF NUCLEAR LEVEL DENSITY PARAMETERS OF SOME LIGHT DEFORMED MEDICAL RADIONUCLIDES USING COLLECTIVE EXCITATION MODES OF OBSERVED NUCLEAR SPECTRA

In this study the nuclear energy level density based on nuclear collective excitation mechanism has been identified in terms of the low-lying collective level bands near the neutron binding energy. Nuclear level density parameters of some light deformed medical radionuclides used widely in medical applications have been calculated by using different collective excitation modes of observed nuclear spectra. The calculated parameters have been used successfully in estimation of the neutron-capture cross section basic data for the production of new medical radionuclides. The investigated radionuclides have been considered in the region of mass number 40<A<100. The method used in the present work assumes equidistance spacing of the collective coupled state bands of the interest radionuclides. The present calculated results have been compared with the compiled values from the literatures for s-wave neutron resonance data.