The RB experimental reactor has operated at Vinca Institute of Nuclear Sciences since the end of April 1958. In this paper, neutron and gamma-ray spectra and corresponding dose quantities near the reactor, calculated by using the MCNP code, are compared to the measured values during the Third International Intercomparison Experiment on Nuclear Accident Dosimetry carried out at the RB reactor in 1973. Discrepancies in the correlation declared power of the reactor-dose rates are found. Good agreements are obtained between measured and calculated neutron and gamma-ray spectra, and corresponding absorbed doses in air, but only after the reactor declared power is multiplied by a correction factor, determined in this study.