The consequences of radiological accidents outside the nuclear sector can be fatal. Therefore, emergency response plans must take into consideration the worst scenarios. This article presents a simulation of an accident in which it was assumed that the assembly of cobalt-60 sources from the irradiator installed at National Institute of Agronomic Research (NIAR) of Tangier was found on the ground. The Monte Carlo GEANT4 code was used to estimate the equivalent dose rate in the organs of an individual presented by an anthropomorphic phantom at different distances, and its variance with decreasing activity, this simulation will allow as to make the best decisions, correct actions, prevent serious radiobiological damage and to prepare the best methods of intervention in the occurrence of this scenario.