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AbstractAbstract
[en] 226Ra's presence in natural and industrial environments pose sanitary and environmental concerns, which needs to predict and model the radionuclide fate over time. It's mobility is governed by surface interactions (sorption) and solid solution formation (coprecipitation or incorporation) with mineral phases of its surrounding environment, so we focused on studying the interactions between 226Ra and the main natural sulfate phases (gypsum, celestine and barite) which may play a key role in reducing radium's mobility. The study of 226Ra's interactions with gypsum via sorption/desorption and solid solution formation experiments have shown that pure gypsum is unlikely to play any significant role in reducing radium's mobility with a low distribution coefficient of (8,8 ± 1,5).10-4. The same study ran with celestine have shown that the solid solutions Sr1-xRaxSO4 formed during the experiment exist for x values ranging from 1,6.10-4 to 6,5.10-2, with a distribution coefficient of about 212. Interpretation of the experimental data through different solid solution approaches suggests that other mechanisms than simple exchange between Sr and Ra may occur. Investigating the impurities' role in radium's concentration in solution show that even if they don't seem to play any role in our experiments, they may play a key role in natural environments. Field samples' study from a mining site via sequential leaching shows that in natural environment where sulfate phases presence has not been detected, radium's mobility is mainly controlled by its sorption onto clay minerals and oxides, but it can also be controlled by other hydrated sulfates phases than barite and celestine
[fr]
Les enjeux environnementaux et sanitaires lies a la mobilite de 226Ra present dans de nombreux aquiferes naturels et en contexte industriel (minier, petrolier, agricole) passent par la prediction et la modelisation du comportement du radionucleide au cours du temps. Sa mobilite etant essentiellement gouvernee par des interactions de surface (adsorption), ou par la formation de solutions solides (co-precipitation ou incorporation) avec les phases minerales presentes dans son environnement, nous nous sommes interesses aux principaux sulfates d'alcalino-terreux naturels que sont le gypse (CaSO4.2H2O(s)), la celestine (SrSO4(s)) et la barytine (BaSO4(s)) et qui sont susceptibles de jouer un role dans la reduction de la mobilite du radioisotope. L'etude des interactions entre 226Ra et le gypse a travers des experiences de sorption/desorption et formation de solutions solides (coprecipitation et incorporation) a permis de mettre en evidence que le gypse pur n'est pas une phase minerale pouvant exercer une retention sur le radioelement, avec un coefficient de distribution du radium dans le solide evalue a (8,8 ± 1,5).10-4. Au contraire, la meme etude menee avec la celestine a permis de former des solutions solides Sr1-xRaxSO4 pour un domaine minimum de x compris entre 1,6.10-4 et 6,5.10-2, avec un coefficient de distribution defini dans la celestine d'environ 212. L'interpretation des donnees selon differents formalismes de solutions solides suggere que des mecanismes plus complexes que la seule substitution de Sr par Ra son mis en jeu. L'etude de l'influence des impuretes sur la capacite d'incorporation de 226Ra a montre que si elle est negligeable dans nos experiences, elle peut s'averer jouer un role majeur en contexte naturel. L'etude d'echantillons de sites miniers en exploitation par in situ recovery (ISR) a permis de montrer a travers des tests de lixiviation selectives et sequentielles que si le radium est essentiellement lie aux argiles et aux oxydes dans les echantillons ou la presence de sulfates n'a pas ete detectee, il peut toutefois etre retenu par des phases sulfatees hydratees autres que la celestine et la barytineOriginal Title
Interactions entre 226Ra et les mineraux sulfates (gypse, celestine et barytine) presents en environnement minier
Primary Subject
Source
28 Nov 2013; 174 p; 70 refs.; Available from the INIS Liaison Officer for France, see the 'INIS contacts' section of the INIS website for current contact and E-mail addresses: http://www.iaea.org/inis/Contacts/; Also available from Service Commun de Documentation, Boulevard Francois Mitterrand, 91000 Evry-Courcouronnes (France); Geochimie
Record Type
Report
Literature Type
Thesis/Dissertation
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Country of publication
ALKALINE EARTH ISOTOPES, ALKALINE EARTH METAL COMPOUNDS, ALPHA DECAY RADIOISOTOPES, BARIUM COMPOUNDS, CALCIUM COMPOUNDS, CARBON 14 DECAY RADIOISOTOPES, DISPERSIONS, DISSOLUTION, ENVIRONMENTAL TRANSPORT, EVEN-EVEN NUCLEI, HEAVY ION DECAY RADIOISOTOPES, HEAVY NUCLEI, HOMOGENEOUS MIXTURES, ISOTOPES, MASS TRANSFER, MINERALS, MIXTURES, NUCLEI, OXYGEN COMPOUNDS, PRECIPITATION, RADIOISOTOPES, RADIUM ISOTOPES, SEPARATION PROCESSES, SOLUTIONS, SORPTION, STRONTIUM COMPOUNDS, SULFATE MINERALS, SULFATES, SULFUR COMPOUNDS, YEARS LIVING RADIOISOTOPES
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