PhD defense of Jordan Bassetti

The jury of my defense is composed of:

• Mrs. SCHMITT Véronique, Reviewer, Director of Research, CNRS, Bordeaux, France
• Mr. D'ESPINOSE DE LACAILLERIE Jean-Baptiste, Reviewer, Professor, ESPCI, Paris, France
• Mrs. RIVENET Murielle, Examiner, University Professor, Centrale Lille Institute, France
• Mr. PETIT Fabrice, Examiner, PhD, BCRC Mons, Belgique
• Mrs. NARDELLO-RATAJ Véronique, Invited member, University Professor, Centrale Lille Institute, France
• Mr. PERRIN Stéphane, Invited member, PhD, CEA Marcoule, France
• Mr. PIERLOT Christel, Thesis supervisor, Associate Professor, Centrale Lille Institute, France
• Mr. POULESQUEN Arnaud, Thesis co-supervisor, PhD, CEA Marcoule, France

Keywords
Formulation, Geopolymers, NMR, Solid Impregnation, Pickering emulsions, Process

Abstract

The operation of nuclear facilities results in the production of various potentially radioactive wastes, including certain non-incinerable organic liquids. A significant portion of these low and intermediate-level wastes currently lacks a definitive treatment and storage solution. Geopolymers, recently studied, are proving to be a promising alternative to conventional silico-calcium cement due to their hardening mechanism based on the polycondensation of aluminosilicate networks, allowing the incorporation of large quantities of oil, except for hydrolyzable fluids. These fluids include TriButyl Phosphate (TBP), used in the PUREX (Plutonium URanium EXtraction) process for the extraction of plutonium and uranium, as well as cutting fluids. A thorough analysis of these fluids, reviewing their chemistry and formulation, led us to select sunflower oil as a representative model of this family. The direct incorporation of this oil into a geopolymer shows a saponification reaction with the alkaline medium, while monitoring by nuclear magnetic resonance (NMR) spectroscopy reveals a hydrolysis rate of 45% after 7 days of immobilization. For TBP, hydrolysis is complete in 20 days with a 10 mol.L-1 NaOH solution, while no hydrolysis is visible after 30 days of immobilization within a geopolymer. Pretreatment methods have been developed for these conventionally untreatable fluids, allowing more efficient storage. The first method involves impregnating the fluids onto functionalized clays, such as CTAB-sepiolite, ensuring effective retention of organic liquids. The second method uses nano-zeolites and nano-silicas to formulate Pickering emulsions, allowing pre-encapsulation of the fluids. Both processes enable the containment of 20% oil without apparent release. This work opens new perspectives for the efficient and sustainable treatment of potentially radioactive hydrolyzable liquid wastes.

After the defense, a get-together party will follow in the Chevreul Institute Hall.