Size and radial origin of fragments formed while heating a 83 GWd/t$_U$ PWR fuel up to 1200 °C
Résumé
When submitted to heating tests reaching 1200 °C, pellet long fuel samples generally exhibit cracking
after the test, nonetheless, the fuel keeps its original shape and most of the fragments remain inside
the cladding section [1].
However, after having been submitted to a 1200 °C, 20 °C/s, heating test with a surrounding pressure
close to 0.1 MPa, in the Merarg LECA-STAR CEA device, a UO$_2$ section, with a local average burn-up of
83 GWd/t$_U$, was found fragmented, with most of the fragments outside of the cladding and in the
crucible used for the test. These fragments exhibited a wide range of sizes.
Detailed examinations on a sibling sample had been previously conducted. They are partly reported
in [2].
Using these previous results as a reference for the fuel microstructure and composition along the
pellet radius, a detailed examination of thirty three of these fragments was conducted using the
EPMA. The purpose of these detailed examinations was to determine the radial origin of each one of
these fragments and to evaluate whether there was, or not, a link between the size of these
fragments and their initial location within the pellet.
The result of this study was that all the millimetric fragments visible on the polished surface of the
sample came from areas that had shown, at the end of the irradiation, an especially low fission gas
bubble formation rate, when compared to the rest of the pellet. On the contrary, very small
fragments formed in all areas where many fission gas bubbles had been seen at the surface of a
polished cross section.
Domaines
Matériaux
Origine : Fichiers produits par l'(les) auteur(s)
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