Suplemento de la Revista Mexicana de Física

Experimental Modeling and Synchrotron Light analysis of uranium transport by surface water in sediments of Peña Blanca-Laguna del Cuervo, Chihuahua.

Victoria Perez Reyes — 2024-09-10

Peña Blanca, located 50 km to the north of Chihuahua's city, hosts about 70% of the natural U deposits in Mexico, which contains the uranophane mineral. Uranium could be present in the environmental matrices of rock and soil; it could be redistributed naturally or anthropogenically in the environment. The adverse health effects of uranium are mainly ascribed to its chemistry, causing damage to the kidneys. The main goal of this work is to model the transport of U minerals by leaching at Peña Blanca-Laguna del Cuervo area using sediment columns. XDR, SEM, Alpha Spectrometry, and X-Ray Absorption Fine Structure techniques were applied to identify favored processes. It was possible to correctly reproduce the granulometric sequence of the topography from the Peña Blanca's deposits to the alluvial fans in Laguna del Cuervo. The mineralogical composition of the sediments corresponds to the erosion of felsic volcanic rocks. Activity concentrations of the effluent solutions and the fine fractions of the sediments could be explained from the properties of the grain and its distribution. Through X-Ray Absorption Near Edge Structure (XANES) study of silt and (fine silt + clay) sediment fractions, the U(VI) oxidation state was verified, referable to the adsorption of uranyl ions.

Application of the nuclear tracks methodology for the validation of atomic force microscope probe tips

B. E. Zendejas-Leal — 2024-08-06

Atomic force microscopy (AFM) is a well-established technique for studying materials at nanoscale dimensions. The resolution of this instrument strongly relies on the sharpness of its tip, which can become compromised through wear and breakage, often due to contamination at the AFM tip apex. To evaluate the condition of both new and used tips, scanning electron microscopy (SEM) inspection is commonly employed. However, SEM services may not always be readily available or in high demand. In this study, we present an AFM tip calibration device that utilizes a pattern of etched tracks on CR-39 material. To construct this device, you will require a radioactive alpha particle source, typically Americium-241, as well as a controlled temperature bath set at 60 degrees Celsius, which contains a 6.25 M KOH solution. This endeavor serves as another intriguing and practical application of the nuclear tracks methodology.

Interpretation of X‐ray Absorption Spectra by synchrotron radiation of the uranium mineral species transported by the main stream “El Tigre”, in Peña Blanca, Chihuahua, Mexico

Cristina Hernandez Herrera — 2024-08-19

The state of Chihuahua, Mexico, has several uranium deposits. The most important is the Peña Blanca deposit at north of the Chihuahua City. After an intensive exploration in the 80’s, the mineral extracted and unprocessed was confined in rock stacks exposed to weathering. To characterize the transport of uranium by surface water in the form of particles or dissolved, a sampling was carried out in the bed of the stream “El Tigre”. Nine sediment samples were collected near the Nopal 1 mine, and separated into coarse sand, fine sand, silt, and fine silt + clay fractions. The activity concentration of the uranium series isotopes was determined by gamma spectrometry, applied to the different fractions of each sample. The fine silt + clay and fine sand fractions were analyzed by X-ray diffraction in the 2 most active samples, Nopal 1 and Nopal 2. The phases are quartz, calcite, montmorillonite, sanidine, orthoclase, albite, kaolinite and magnetite. Particles of d < 100 μm (P1-Bulk) were extracted from the fine sand fraction of Nopal 1 with the help of ultraviolet light fluorescence; uranium and silicates were confirmed in them by SEM-EDS. P1-Bulk sample was subjected to X-ray absorption spectroscopy measurements on the U L3-edge, as well as to the samples fine silt + clay fraction of the Nopal 1 (P1-Clay) and Nopal 2 (P1-Silt). The X-ray absorption near edge (XANES) region analyzed indicates the presence of hexavalent uranium in the three samples. The fit of the Extended X-ray absorption fine structure (EXAFS) spectrum of the P1-Bulk sample indicates that it is α-uranophane. This result is consistent with the reports of the area.

Study of Gross alpha beta radioactivity content in commercial water brands by liquid scintillation

C. P. Zepeda — 2024-09-22

This study presents the Gross alpha beta radioactivity in bottled water from twenty different commercial brands. In Mexico, the official Mexican standard NOM-127-SSA1-2021 establishes the values of 0.5 and 1.0 Bq/L as limits for Gross alpha and beta radioactivity in drinking water. The analysis was carried out with the liquid scintillation method, making a concentration of 10 to obtain a minimum detectable concentration of 0.25 and 0.5 Bq/L respectively. The results obtained indicate that in all cases the bottled waters comply with the applicable standard, which in turn indicates that the effective annual dose would be less than 0.1 mSv, since this limit was calculated based on this premise, indicating that the radiological risk for the consumer is negligible according to this norm.