Three-dimensional Monte Carlo calculation of gas production in structural material of APEX reactor for some evaluated data files

► We calculated the effects of ENDF libraries on gas production rates in structural material. ► We used the MCNPX-2.5.0 Monte Carlo code for three-dimensional calculations. ► The most prominent contributions to gas production rates are from Fe-56 and Fe-54 isotopes. ► Proton production was found greatest for JENDL-4.0 library with 409.69 appm/30 FPY. ► The helium limit of 500 appm is reached at 50 cm for all selected libraries.