A series of Bi50Pb50-xSnx alloys, where x = 0, 16, 20, 25, and 30 wt. %, were prepared to be used as coolants and for heat transfer in fast fission and/or fusion nuclear reactors. For the prepared alloys, measurements were made of their density and melting points. Similarly, high-temperature measurements of the alloys' wetting contact angles on several substrate types were made to clarify their possible application in the design of nuclear reactors. The mass attenuation coefficients〖 μ〗_m (cm2/g) were established experimentally with energy ranges of 121.8 to 1407.24 keV. The neutron macroscopic cross sections ̩Ʃ (cm-1) and mean free path MFP (cm) of the alloys were determined experimentally using three neutron energy ranges (slow neutrons, total slow neutrons, and neutrons with energies > 0.4 eV). The results indicated that there was a substantial agreement between the theoretical calculations which were done with the aid of “WinXCom" and “Phy-X/PSD" software and the practical outcomes. The increase in Sn concentration at the expense of Pb improves the physical characteristics of (Bi-Pb-Sn) alloys, making them suitable for use as coolants in fast nuclear reactors.