## 3 Results and Discussion
for all the alloys. At 1 MeV, the Zeq reached its maximum, varying between 27.31 and 45.96 for the Nimocast-75 and MAR-302 alloys, respectively. Above 1.5 MeV, the Zeq gradually reduced due to the dominancy of the PP interaction inside the studied alloys. Based on these factors, it can be concluded that the MAR-247 and MAR-302 alloys possess the most desirable shielding characteristics among the investigated alloys, while the Inconel-625 and Inconel-718 alloys possess the least effective shielding ability. The desirable attenuation ability of the MAR-247 and MAR-302 alloys is related to their chemical composition, which contains heavy elements with good shielding characteristics such as tungsten (W), tantalum (Ta), and hafnium (Hf). The less effective shielding characteristics of Inconel-625 and Inconel-718 are also due to their chemical composition, which mainly consists of nickel (Ni) and chromium (Cr). The energy absorption and exposure buildup factors (EABF and EBF) were calculated according to [30]. The variation of the buildup factors EABF and EBF versus the gamma-ray energy at some penetration depths (PD) between 0.5 and 40 mfp is shown in Figures 6a-f and 7a-f. The lowest EABF and EBF values for the selected alloys were obtained at the lowest tested photon energy. The energy of gamma photons is completely absorbed during the PE interaction. Thus, photons cannot contaminate inside the selected alloys, which reduces the buildup factors. At middle energies where the CS interaction is prevalent, the calculated values of EABF and EBF for all the selected alloys increase as energy increases. As a result of the CS interaction, a secondary photon can be produced and accumulated inside the selected alloys. Thus, the buildup factors greatly increase in the CS interaction region. Past this region, the values of the buildup factors begin to slowly decrease with the increase of photon energy, above 1.5 MeV more specifically. This decrease is due to the photons that have enough energy to create electron-positron pairs with low kinetic energy. For energies greater than 8 MeV, the values of EABF and EBF quickly increased with increasing energy, especially at high penetration depths (PD > 20). Figures 6 and 7 show that the highest values of EABF and EBF were obtained for the MAR-302 alloy, while the lowest values were obtained for the WI-51 alloy. Figure 6: Variation of the energy absorption buildup factor versus the gamma-ray energy at various penetration depths.for the investigated alloys: (**a**) MAR-247, (**b**) MAR-302, (**c**) Inconel-625, (**d**) Inconel-718, (**e**) Nimocast-75, (**f**) WI-51. The variation of buildup factors with the penetration depth (PD) for the selected alloys is presented in Figure 8 at some fixed gamma-ray energies (0.015, 1, and 15 MeV). At around 0.015 MeV, for all the selected alloys, the values slowly increased with the increase in the PD. At 1 MeV, where CS is prevalent, EBF and EABF steadily increased with the increase in PD, especially at high PD (\(\geq\)20 mfp). Additionally, at high energies, the values quickly increased with the penetration depth, especially for PD \(\geq\)20. Figure 8: Variation of the buildup factors versus the penetration depth of the studied alloys at some fixed energies: (**a**) 0.015 MeV, (**b**) 1 MeV, (**c**) 15 MeV. Figure 3.0 Variation of the exposure buildup factor (EBF) versus the incident gamma-ray energy at various penetration depths for the investigated alloys: (**a**) MAR-247, (**b**) MAR-302, (**c**) Inconel-625, (**d**) Inconel-718, (**e**) Nimocast-75, (**f**) WI-51. Furthermore, the ability of the selected alloys to attenuate fast neutrons was evaluated. The effective removal cross-section \(\sum_{\mathrm{R}}\) (cm\({}^{2}\cdot\)g\({}^{-1}\)) for fast neutrons was calculated according to Equations (5) and (6) [35]  
Figure 3.1  
Figure 3.2  
Figure 9 illustrates the \(\sum_{\mathrm{R}}\) of fast neutrons for the selected alloys.