In this study, the annual and monthly equivalent dose of the operation of the Tehran Research Reactor in a human phantom in the pool and surrounding areas as well as the dome from the fission of radioactive gases (Kr, Xe, Cs, Ar, S, N, C, K, I) and suspended particulates emitted by the pool, were calculated by MCNPX code. The results show that the exposed doses by workers at the top and around the pool, when the limit was of the order of 408 hours and 1836 hours per year or speed of the air in such a way that the activity of gases given off by the pool,  were reduced to 10% and 80% of the reported values explained by FSAR, respectively.