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.
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.
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