Thermal air oxidation of UO2: Joint effect of precursor's nature and particle size distribution

• DOI: 10.1016/j.pnucene.2023.104629
• Publication Date: 2023-03-02T22:39:55Z
• Authors: A. Milena-Pérez; N. Rodríguez-Vill...; S. Fernández-Carr...; A. Núñez
• Keywords: Thermogravimetric analysis; Nuclear fission product; Thermal oxidation; Reaction rate; Nuclear Fuel; Weight change

The rate and extent of the air oxidation UO2 are paramount importance due to its relevance in management spent nuclear fuel at dry storage facilities. In particular, formation U3O8 requires special interest because it could compromise integrity cladding. an attempt reproduce behavior used (in which presence fission products Pu will also influence oxidation), unirradiated was studied this work. is strongly dependent on physical parameters starting material, although some not fully-studied. present study, nature material particle size distribution thermal temperature were evaluated detail. Since follows a complex kinetic mechanism comprising various crystalline phases, composition quantity change influenced by oxidant gas phase, conditions set favor U3O8, practical importance, as well study impact physico-chemical properties raw oxidation. Various powdered sample substrates ranging from synthetic (prepared via ADU route) grinded sieved fragments fresh pellets oxidized same conditions. average O/U atomic ratios samples calculated assuming total conversion data thermogravimetric analysis (TGA). Each weight variation curve characterized discussed terms Oxidation Onset Temperature (OOT), Maximum Reaction (MRT), Rate maximum reaction (RRMRT). Scanning Electron Microscopy (SEM) employed evaluate surface morphology. All thermally exhibit oxides with spallation. Surface morphology materials confirms different samples, while typical pop-corn-like particles. order accomplish better description oxidation, results relative precursors, area size. affects formation, being faster powders than powder coming milled pellets. By comparing origin, effect width proved for first time, slower substrate wider (labelled P3). P3 more similar real irradiated pellet, mechanistic point view, work valuable input security studies facilities fuel.