A thermogravimetric comparative study of the high temperature steam oxidation of bare and pre-oxidized Zircaloy-4, M5Framatome and Optimized ZIRLO™

Christian Duriez (1) , H Richez (2) , C Eymery (3) , Severine Guilbert (1)

1 IRSN/PSN-RES/SEREX/LE2M - Laboratoire d'Expérimentation en Mécanique et Matériaux
2 INSA Rennes - Institut National des Sciences Appliquées - Rennes
3 AMU SCI - Aix-Marseille Université - Faculté des Sciences

For LOCA analysis, high temperature oxidation kinetics in steam of Zircaloy-4 and the two Nb-bearing alloys used in French Pressurized Water Reactors (PWRs), M5Framatome1 and Optimized ZIRLO™ 2 , have been studied with the thermogravimetric technique, in the 900-1200°C temperature range. A specific test protocol for fast heating of the specimens in a high steam flow rate has been used. For as-received claddings, at 1100°C and above, oxidation kinetics is comparable and close to parabolic for the 3 alloys. Below 1100°C, significant deviation from the parabolic kinetic regime is observed and M5 Framatome oxidizes slower than Zircaloy-4 and Optimized ZIRLO. The influence of pre-oxidation, simulating corrosion in normal reactor operation, has been investigated for Zircaloy-4 and M5Framatome. A strong protective effect is observed below 1200°C, while at 1200°C the pre-oxidation layer appears to be much less protective, possibly because of the monoclinic to tetragonal zirconia transformation.

Domaines: Sciences de l'ingénieur [physics]

Christian Duriez, H Richez, C Eymery, Severine Guilbert. A thermogravimetric comparative study of the high temperature steam oxidation of bare and pre-oxidized Zircaloy-4, M5Framatome and Optimized ZIRLO™. 2024. ⟨irsn-04500986⟩