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AbstractAbstract
[en] The vapor hydration of inactive surrogates of AVM (Atelier de Vitrification de Marcoule) glasses (simple and complex) has been studied in this thesis work with a special focus on the influence of glass composition. In the first part of the thesis, multiple glass samples were altered at 50 C and 95% RH and the altered samples were characterized using SEM, TEM, XRD, ToFSIMS and SAXS to study the altered (gel) layer. The results show that aluminum plays a key role in glass durability under the given conditions, especially in relative proportions to alkaline-earth elements. When the molar ratio of Al2O3/MgO≤1, the overall vapor hydration rate was accelerated by 10-20 times due to the formation of Mg-rich smectites. In other cases, network-hydrolysis was identified as the rate controlling vapor hydration mechanism for the first six months. Complementary studies on the effect of temperature and relative humidity gave further insights into secondary phase precipitation, behavior of elements in the gel layer and altered layer morphology. These studies show that the predominant vapor hydration mechanism varies with temperature and glass composition as well. In the second part of the thesis, aqueous alteration experiments are discussed in two contexts. First, vapor hydrated glasses immersed in pure water showed that the gel layer did not have a passivating effect against aqueous alteration and that some of the secondary phases formed during vapor hydration are readily soluble. Secondly, comparative structural study of 17O enriched gel layers that were formed during vapor hydration (at 90 C) and aqueous alteration at a very high SA/V ratio using NMR spectroscopy showed for the first time, evidence of recondensation of boron with oxygen from the vapor phase. The results suggest that glass alteration in vapor phase is not equivalent to alteration in aqueous medium at a very high SA/V ratio. (author)
[fr]
L'hydratation en phase vapeur des verres inactif (simples et complexes) du domaine AVM (Atelier de Vitrification de Marcoule) a ete etudiee en se focalisant sur l'influence de la composition du verre. Dans la premiere partie, les echantillons de verre ont ete alteres a 50 C et 95% d'humidite relative, et les couches alterees (gel) ont ete caracterises par SEM, TEM, XRD, ToFSIMS et SAXS. Les resultats montrent que la teneur en aluminium par rapport a celle des alcalino-terreux joue un role cle dans la durabilite du verre. Lorsque le rapport molaire Al2O3/MgO≤1, la vitesse d'hydratation en phase vapeur est augmentee de 10 a 20 fois par la formation des precipites riches en Mg. Dans d'autres cas, l'hydrolyse du reseau vitreux a ete identifiee comme le mecanisme controlant la vitesse d'hydratation en phase vapeur. Des etudes complementaires sur l'effet de la temperature et de l'humidite relative ont montre que le mecanisme predominant d'hydratation en phase vapeur varie en fonction de la temperature et de la composition du verre. Dans la deuxieme partie, des experiences avec des verres hydrates en phase vapeur puis immerges dans de l'eau pure ont montre que le gel n'avait pas d'effet passivant vis-a-vis l'alteration aqueuse et que des phases secondaires formees pendant l'hydratation en phase vapeur pouvaient etre solubles. Deuxiemement, une etude comparative de la structure des gels enrichies en 17O formees lors d'hydratation en phase vapeur (a 90 C) et de l'alteration aqueuse a tres fort S/V par la spectroscopie RMN a montre pour la premiere fois, de la recondensation du bore avec de l'oxygene provenant de la phase vapeur. Les resultats suggerent que l'alteration du verre en phase vapeur n'est pas equivalente a l'alteration en milieu aqueux a tres fort S/V. (auteur)Original Title
Influence de la composition des verres nucleaires type AVM lors de son alteration en phase vapeur
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20 Nov 2019; 347 p; 210 refs.; Available from the INIS Liaison Officer for France, see the INIS website for current contact and E-mail addresses; Sciences des Materiaux
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Report
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Thesis/Dissertation
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