Modelling of Zircaloy-4 degradation in oxygen and nitrogen mixtures at high temperature
type: Dataset
contact point: Organization
  fn: CCSD
keyword: thermogravimetrie
keyword: infoeu-reposemanticsdoctoralthesis
keyword: thermogravimetric-analysis
keyword: corrosion-sous-air
keyword: nucleation-growth
keyword: modele-cinetique
keyword: methode-des-decrochements
keyword: zircaloy-4
keyword: germination-croissance
keyword: jumps-method
keyword: mampels-mode
keyword: solid---gas-reaction
keyword: modele-de-mampel
keyword: reaction-solide-gaz
keyword: air-corrosion
keyword: theses
keyword: kinetic-modelling
keyword: spiotherengineering-sciences-physicsother
landing page: https://theses.hal.science/tel-00949122
description: Zircaloy-4 claddings provide the first containment of UO2 fuel in Pressurised Water Reactors. It has been demonstrated that the fuel assemblies cladding could be exposed to air at high temperature in several accidental situations. When mixed to oxygen at high temperature, the nitrogen, usually used as an inert gas, causes the accelerated corrosion of the cladding.The kinetic curves obtained by thermogravimetry reveal two stages: a pre-transition and a post-transition one. In the post-transition stage, the kinetic rate increases with time. Images obtained by optical microscopy of a sample in the post-transition stage reveal the presence of corroded zones characterized by a porous scale with zirconium nitride precipitates at metal - oxide interface. Corrosion of Zy4 plates at 850°C under mixed oxygen - nitrogen atmospheres has been studied during the post-transition stage. A sequence of three reactions is proposed to explain the mechanism of nitrogen-enhanced corrosion. The accelerating effect of nitrogen in the corrosion scale can therefore be described on the basis of an autocatalytic effect of the zirconium nitride precipitates. Then, it is demonstrated that the steady-state approximation as well as the existence of an elementary step controlling the growth process are valid during the post-transition stage. The rate-determining step is identified as the external interface reaction step of the oxidation of the zirconium nitride precipitates. Finally, a nucleation and growth model used for thermal reactions in powders is used to describe both the nucleation and the growth of the attacked regions.
identifier: NNT: 2013EMSE0725
issued: 2026-05-06T07:56:34.376917
language: fr
modified: 2026-05-06T07:56:34.376922

test_moissonnage_selune
type: Agent

Modelling of Zircaloy-4 degradation in oxygen and nitrogen mixtures at high temperature
type: Distribution
access URL: https://theses.hal.science/tel-00949122
format: HTML
issued: 2026-05-06T07:56:34.379587
modified: 2026-05-06T07:56:34.339568