The EL Berrocal Project: Geological Characterisation and Radionuclide Migration Studies in a Fractured Granitic Environm
- PDF / 597,567 Bytes
- 8 Pages / 414.72 x 648 pts Page_size
- 14 Downloads / 193 Views
THE EL BERROCAL PROJECT: GEOLOGICAL CHARACTERISATION AND RADIONUCLIDE MIGRATION STUDIES IN A FRACTURED GRANITIC ENVIRONMENT W.M. MILLERI, L. P1tREZ DEL VILLAR2, P. GOMEZ2, M. IVANOVICH3, B. DE LA CRUZ2, P. RIVAS2, P. HERNIAN4, J. CARRERA5, J. GUIMERA5, D. HOLMES6, S. AVOGADRO7, J.-M. FERNANDEZ8, J. BRUNO9 (1)Intera Information Technologies Ltd., Melton Mowbray, UK; (2)Centro de Investigaciones Energ6ticas, Medioambientales y Tecnol6gias (CIEMAT), Madrid, Spain; (3) AEA Technology, Analytical Services Group, Harwell, UK; (4)Empresa Nacional de Residuos Radioactivos, SA (ENRESA), Madrid, Spain; (5) Centro Intemacional de M6todos Num6ricos en Ingenierfa, Universidad Polit6cnica de Catalufia, Barcelona, Spain; (6) British Geological Survey, Keyworth, UK; (7) JRC, Environment Institute, Ispra, Italy; (8)Commissariat Ar'Energie Atomique, Cadarache, France; (9)Intera Information Technologies SL, Cerdanyola, Spain
ABSTRACT El Berrocal is an abandoned uranium mine in a mineralised quartz vein hosted by a Hercynian granite in central Spain. This mine is the focus of an international project to characterise and model natural elemental migration in a fractured-rock environment as an aid to understanding and predicting processes that may occur in a geological repository for radioactive wastes. Uranium in the mineralised quartz vein has been shown to have originated from the orthomagmatic uraninite in the granite with the elemental removal and migration occurring predominately by hydrothermal fluids. Mobilisation of uranium from the mineralised quartz vein and from granite adjacent to hydraulically-active fractures away from the vein occurred over the geologically-recent past and in the present-day. The most recent mobilisation is evidenced by dissolution features seen in SEM photomicrographs; mineral growth and sorption signatures identified by enhanced uranium concentrations on the surfaces of preexisting minerals; and measured disequilibrium in the uranium series for whole rock close to fracture walls. Present-day groundwaters in the studied area are young meteoric waters. They are generally calcium-sulphate enriched, oxidising and mildly acidic near the surface, becoming more bicarbonate-rich with near neutral pH in the deeper zones, except around the mineralised vein where the waters are acid (pH around 3) due to oxidisation of the sulphide minerals. No deep, chemically-reducing groundwaters have yet been identified in the El Berrocal boreholes.
INTRODUCTION The El Berrocal Project is an exercise in geological characterisation and has the overall aim of understanding and modelling the past and present-day migration processes that control the distribution of naturally occurring radionuclides within a fractured granitic environment, using an approach that fully integrates the structural, hydrogeological, lithogeochemical and hydrogeochemical features of the site. The objectives of the Project are broadly focussed on those processes which have relevance to safety assessments for radioactive waste disposal. However, El Berroc
Data Loading...
