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In reactor shielding designs, deep-penetration shielding issues, and direct photon heating, photon transport physics is crucial. In the Reactor Monte Carlo (RMC) code, a state-of-the-art photon transport capacity is implemented in this research. For criticality and fixed-source calculations, pure photon and coupled neutron-photon transport are now simulated for four photon-atomic interactions, including Rayleigh scattering, Compton scattering, Photoelectric effect, and Pair production, as well as three major processes of the secondary photons generation (Atomic relaxation, Electron-positron annihilation, and Bremsstrahlung by electrons and positrons). In order to properly balance energy release and deposition during neutron-induced photon production, the yield of photons by neutrons is scaled by a correction factor to account for the delayed gamma radiation, and the effective multiplication factor k e f f is used in an uncritical system. Using an Automatic Library Generator (ALG) code, a new database for photon transport is processed with the ENDF/B evaluated nuclear data library. Numerous cases, such as a point source in an infinite geometry, a photon beam source in a cylinder geometry, and a fuel assembly in the VERA benchmark, are verified against the Monte Carlo (MC) code OpenMC. Despite some notable differences in the comparison of the photon flux at certain energy ranges, which are caused by differences in the database and also the physics implementation, the results of the energy and spatial distributions of photon flux, and the photon heating show generally good agreement and relative errors are nearly within a triple statistical standard deviation. RMC now offers advanced photon transport capacity for reaction core and shielding applications. • The principle types of photon interactions and secondary photon processes were implemented in RMC. • The methods were verified against OpenMC and great agreements were achieved. • A new photon-atomic database in HDF5 format processed with an Automatic Library Generator (ALG). • Precise correction for the delayed gammas and k e f f correction for uncritical system for the photon heating. [ABSTRACT FROM AUTHOR]