Adsorption desorption behaviour of CO2 and H2O on_ hO2powders

Niels Palmans, Marc Verwerft, Beatriz Acevedo Muñoz, Rémi Delville

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    Abstract

    Thorium dioxide has recently regained interest as an alternative to uranium-based fuels due to its less long-lived transuranium element production or its higher natural abundance, among others. Though, ThO2 pellet production faces many challenges such as reaching high theoretical densities. This can be improved by sintering the pellets, but this treatment is altered by many factors. In fact, a release of adsorbed gases was observed which can negatively change the grain growth. This thesis presents a systematic study on the adsorption of CO2 and H 2O on two types of ThO2 powders reproducing storage conditions, one derived from thorium oxalate (ThO_OX) and one from a novel 2-step alkali precipitation route (ThO_TSA). Both materials were characterized by means of N 2 adsorption isotherm at 77K, SEM and TEM. Moreover, CO2 and H 2O desorption was experimentally studied by TGA coupled to mass spectrometry. Surface analysis indicates that both materials are non-rigid aggregates with mesoporosity attributed to interparticular cavities which agrees with the SEM and TEM images. However, SEM/TEM also shows that the particle shapes differ significantly, being plate-like for ThO_Ox, and sphere-like for ThO_TSA. The powders retained CO2 adsorbed well above 600°C, and it seems the adsorbed water has a significant effect on the CO2 adsorption. ThO_TSA reached the saturation point earlier than ThO_Ox, suggesting a lower gas adsorption capacity. Therefore, the 2- step alkali precipitation route is recommended for long ThO2 powder storage periods.
    Original languageEnglish
    QualificationMaster of Science
    Awarding Institution
    • Uhasselt - Hasselt University
    Supervisors/Advisors
    • Schreurs, Sonja, Supervisor, External person
    • Delville, Rémi, SCK CEN Mentor
    • Acevedo Muñoz, Beatriz, SCK CEN Mentor
    Date of Award8 Jun 2020
    Publisher
    StatePublished - 19 Jun 2020

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