The Pocos de Caldas Project: Natural Analogues of Processes in Radioactive Waste Repository

The safe disposal of radioactive wastes by burial in deep geological formations requires long-term predictions of the future behaviour of the wastes and their engineered repository. Such predictions can be tested by evaluating processes analogous to those which will occur in a repository, which have been long active in the natural geochemical environment. The Pocos de Caldas Project is a comprehensive study of two ore deposits in Minas Gerais, Brazil, aimed at looking at uranium and thorium series radionuclide and rare-earth element mobility, the development and movement of redox fronts, and the nature of natural groundwater colloids. A multidisciplinary team of experts from 27 laboratories carried out a fully integrated study of the geology, geomorphology, hydrogeology, geochemistry, hydrochemistry and geomicrobiology of the two sites for nearly four years. This book contains 20 papers covering the detailed findings, with particular emphasis on their significance for radioactive waste disposal, especially on the use of the data in testing models of radionuclide movement. It should interest economic geologists, geochemists and performance assessment modellers involved in the geological disposal of radioactive wastes.

Table of Contents:
Part 1 The Pocos de Caldas Project - an introduction and summary of its implications for radioactive waste disposal: the regional geology of the Pocos de Caldas alkaline complex - mineralogy and geochemistry of selected nepheline synenites and phonolites; hydrothermal and supergene uranium mineralizaiton at the Osamu Utsumi mine, Pocos de Caldas, Minas Gerais, Brazil; the supergene thorium and rare-earth element deposit at Morro do Ferro, Pocos de Caldas, Minas Gerais, Brazil; origin and growth rates of pitchblende nodules at the Osamu Utsumi mine, Pocos de Caldas, Brazil; isotopic geochemical characterization of selected nepheline syenites and phonolites from the Pocos de Caldas alkaline complex, Minas Gerais, Brazil; geomorphological and hydrogeological features of the Pocos de Caldas caldera analogue study sites; ground waste chemistry and geochemical modelling of water-rock interactions at the Osamu Utsumi mine and the Morro do Ferro analogue study sites, Pocos de Caldas, Minas Gerais, Brazil; natural decay series studies of the redox front system in the Pocos de Caldas uranium mineralization; the interpretation of 238U-234U-230Th-226Ra disequilibria produced by rock water interactions; uranium and thorium isotopes in groundwaters from the Osamu Utsumi mine and Morro do Ferro natural analogue sites, Pocos de Caldas, Brazil; rare-earth elements in groundwaters from the Osamu Utsumi mine and Morro do Ferro analogue study sites, Pocos de Caldas, Brazil; light rare earth elements and natural series radionuclides within the Morro do Ferro; chemical and physical characterization of suspended particles and colloids in waters from the Osamu Utsumi mine and Morro do Ferro analogue study sites, Pocos de Caldas, Brazil; microbiological analysis at the Pocos de Caldas natural analogue study sites; testing models of trace element geochemistry at Pocos de Caldas; movement of the redox front at the Osamu Utsumi uranium mine, Pocos de Caldas, Brazil; geochemical modelling of uranium redistribution in the Osamu Utsumi mine, Pocos de Caldas; redox front geochemistry and weathering - theory with application to the Osamu Utsumi uranium mine, Pocos de Caldas, Brazil; near-field high temperature transport - evidence from the genesis of the Osamu Utsumi uranium mine, Pocos de Caldas alkaline complex, Brazil. Part 2: Natural analogues for the design and performance of radioactive waste forms - a review: natural analogues for predicting the reliability of the engineered barrier system for high-level waste; using data from natural environments to improve models of uranium speciation in groundwaters; a review of the application of natural analogues in performance assessment - improving models of radionuclide transport in groundwaters; a natural analogue of high pH cement pore waters from the Maqarin area of northern Jordan - introduction, results of predictive geochemical calculations.