In Chihuahua, an important source of environmental radioactivity is found in the Sierra Peña Blanca, in the center of the state. The site comprises about 70% of uranium reserves in Mexico. The uranium of Peña Blanca was explored and partially exploited in the '80s. Due to the closure of operations, the extracted and unprocessed ore (hundreds of tons) was confined to rocky stacks, exposed to weathering. Subject to leaching, this uranium is transported from the mountains to Laguna del Cuervo. The mineral exposed in the repository and the uranium transport by surface water and recent sediments must be studied, to assess the effects on the environment, with radiometric and materials science techniques in conventional laboratories and synchrotron light. This work presents the study of sediment and pore water samples at various points along the lagoon, and the values of the activity ratio of the 234U/238U isotopes and the sediment-water distribution coefficient of these isotopes, obtained by applying uranium liquid scintillation alpha spectrometry, gamma-ray spectrometry, scanning electron microscopy and X-ray diffraction methods.

Using the GEANT4 Monte Carlo simulation software, the efficiency of the HPGe extended range detector of the Environmental Radiological Surveillance Laboratory of CIMAV was modeled. A 137Cs certified point source was employed to determine the experimental gamma efficiency in the desired geometry for the energy of 662 keV. The resulting value was compared with the theoretical efficiency obtained by the Monte Carlo simulation. The results of the simulation were consistent with the experimental one. The same method was applied to calculate the theoretical efficiency in the same detector for borosilicate filters in an extended geometry. The energy then was 477 keV, of the gamma quanta from 7Be, to determine its concentration in air. This efficiency value was applied for air sampling in the city of Chihuahua.