Anisotropic thermal creep of pressurized Zr-2.5Nb tubes is demonstrated. Anisotropic deformation of closed end, internally pressurized tubes (axial stress velence transverse stress) is manifest by a change in length. The tests reported were carried out using an argon gas protection system designed to avoid the formation of a thick white oxide on the ends of the specimen near the closure weld and allow accurate length measurements. Tubes with three different combinations of microstructure and texture were tested. The results show that tubes with a predominantly radial texture exhibit a relatively high diametral creep strain, and a negative long term axial creep strain after a positive initial transient strain. Tubes with a predominantly transverse texture exhibit a relatively low diametral creep strain and a positive axial creep strain. The anisotropy demonstrated is qualitatively consistent with that exhibited during irradiation creep, and this supports the use of such tests to help understand the anisotropy of in-reactor creep.
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