Radial Hydride Precipitation in Fuel Cladding During Back-End Cooling Transient Under Decreasing Pressure
Résumé
During spent fuel assembly transportation or dry cask storage, filling
gas and fission gas release pressurize the fuel rods contained in the cask. These
rods are heated by fuel assembly residual power resulting in internal pressurization
stress increase in the rods. During the subsequent cooling associated to removal of
rods from the transportation cask or during the decrease of residual power after a
long storage period, the cladding hoop stress is expected to decrease. Concomitant
cladding temperature and stress decrease may influence the morphology of precipitated
hydrides in corroded claddings. Radial hydride precipitation has a detrimental
role on the mechanical resistance of the cladding and is promoted by large
hoop stresses during the cooling of the cladding. There is, consequently, a need to
predict the radial hydride precipitation in corroded cladding tubes during dry storage
or transportation cooling transients. Existing models usually address the radial
hydride precipitation conditions under constant stress leading to over-estimated
radial hydride content within the cladding.
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