Diseño de un contenedor para el almacenamiento de fuentes de cobalto-60 en desuso mediante simulaciones de Monte Carlo en la planta de irradiación gamma del Servicio Geológico Colombiano

Abstract

The Colombian Geological Survey, attached to the Ministry of Mines and Energy, possesses twelve Cobalt-60 sources acquired in 1993 that have reached the end of their service life and are currently stored temporarily at the Gamma Irradiation Plant. Since the reactivation of this plant is planned, it is necessary to remove the sources. Therefore, the Survey seeks to establish a computational process for managing disused radioactive sources, in the absence of repatriation options. This undergraduate thesis aims to design and optimize a shielding container through Monte Carlo simulations, minimizing the absorbed doses for both the shielding and occupationally exposed workers. The methodology included five phases: training in the simulation tool, review of national and international regulations, analysis of relevant physical processes, validation of the tool, and finally, implementation of the container model. Among the most relevant results is the analysis of Cobalt-60 behavior and the comparison between different simulation models using discrete and generic sources, showing physical equivalence and computational differences. During the validation process, the consistency of the Linear Attenuation Law was demonstrated between monoenergetic beams and equivalent bi-energetic beams (1.17 MeV + 1.33 MeV), with percentage errors compared to NIST data of 0.8 % in lead and 0.73 % in aluminum. Finally, the model allowed for the adaptation of the Linear Attenuation Law to a cylindrical coordinate system, achieving shielding thicknesses with uncertainties below 20 %, within the limits accepted by radiological protection standards. This enables the proposal of a safe container design tailored to the specific needs for the removal of the sources.