Burst and oxidation tests on bare and pre-oxidized claddings
Résumé
A device to test cladding ballooning/burst under steam environment, based on induction heating of
250 mm long rods filled with alumina pellets, has been developed at IRSN. Strain and temperature in
the balloon region are measured online by stereo Digital Image Correlation (3D-DIC) and an Infrared
camera respectively. The hoop creep rate versus cladding temperature can therefore be determined.
Illustrative results obtained on thermal ramp tested M5 rods showed limited influence of the pretransient oxidation on the creep rate.
Ballooned specimens are fast-cooled, dismounted and afterwards high temperature steam oxidized in
a separate resistive furnace, the samples being finally water quenched by dropping them in a water
bath. After very long steam exposure times, spontaneous ruptures without applied load in the
secondary hydriding region have sometimes been observed during quenching. For non-ruptured rods,
four point bending tests are performed usually resulting in rupture in the ballooned region.
Post-test metallographic examinations and hydrogen measurement by hot vacuum extraction have led
to some highlights on the secondary hydriding process. Among others, a thin inner pre-transient
zirconia layer, aiming to simulate the layer formed at high burn-up by pellet-clad interaction, can be
dissolved during the high temperature oxidation phase and therefore doesn't prevent secondary
hydriding.
Domaines
Sciences de l'ingénieur [physics]
Origine : Fichiers produits par l'(les) auteur(s)
Licence : Copyright (Tous droits réservés)
Licence : Copyright (Tous droits réservés)