Study of the alteration products of a natural uraninite by Raman spectroscopy

Abstract Uraninite is a mineral considered as an analogue of the spent fuel, and the study of its alteration products has been used to predict the secondary phases produced during the fuel storage under specific environmental conditions. In this work, we study by Raman spectroscopy the alteration by weathering of the primary uraninite from the uranium deposit of Sierra Albarrana. The identification of the different secondary phases is based on the analysis of the symmetrical stretching vibration of the uranyl group (UO 2 2+ ), which allows the identification of individual uranyl phases and can be used as a fingerprint. Additionally, we show in this work a new approach to perform a semi-quantitative analysis of these uranium minerals by means of Raman spectroscopy. From this analysis we found the next sequence of alteration products: rutherfordine in contact with the uraninite core, then a mixture of uranyl silicates: soddyite, uranophane alpha and kasolite. Soddyite prevails in the inner part while uranophane alpha predominates in the outer part of the sample, and kasolite appears intermittently (1.0–3.3 mm; 4.6–7.1 mm and 8.8–10 mm).