<p>Fast neutron and gamma-ray attenuation characteristics of Inconel-600, -601, -625, and − 718 superalloys, stainless steel-304, and lead were studied using MCNPX Monte Carlo code, WinXCom, XMuDat, and Auto-Z_eff computer programs. The µ_m, HVL, MFP, σ_a, σ_e, Z_eff and N_eff, and Σ_T were calculated for ¹⁹²Ir, ¹⁸F, ¹³⁷Cs, and ⁶⁰Co gamma sources and 1&#xa0;MeV fast neutrons. The difference between the MCNPX and calculated results was less than ± 2%. Above and below 511&#xa0;keV photon energy, respectively, Inconel-600 and Inconel-625 have the highest mass attenuation coefficient among Inconel alloys. The thickest HVL and MFP values were achieved for the Inconel-601 superalloy. The σ_a and σ_e values decreased as photon energy increased. The Z_eff values were approximately constant with photon energy increase. The Z_eff of the Inconel-601 was the lowest, while that of Inconel-625 was the highest. In the studied gamma-ray energies, the N_eff value variations were insignificant. The stainless steel-304 material was found to have the highest Σ_T, while Inconel-600 had the highest value between Inconel superalloys. Calculated data indicates that Inconel-600 is the superior candidate for shielding gamma rays among Inconel superalloys.</p>