• Andersson, Tom
• Laukkanen, Anssi
• Auerkari, Pertti
• Rantala, Juhani
• Saukkonen, Tapio

Abstract

The research programme on the creep issues of the nuclearwaste disposal canister copper material has continuedwith long-running uniaxial and multiaxial experiments aswell as relaxation testing to support the materialmodelling activities, which produce appropriate materialmodels to be used in the FE analysis, which will be usedto assess the stresses and strains in the criticallocations of the canister.The relaxation testing is ongoing and it has provennecessary to use a servo-mechanical testing machine inorder to generate good quality test data. The initial FEprediction of strain rates calculated by the LCSP creepmodel and a relaxation model suggests a clear difference,but this needs to be verified after a better relaxationmodel is defined based on much more data.The most important result of this year has been theobservation of cracking in the oxide particle zone at thefriction stir weld root in the longest running CT test,which was terminated after 50 000 hours for sectioningand metallographic investigations. The oxide particleshave nucleated creep cavities which have eventually leadto cracking of the oxide particle zone in spite of thelow stress state 8 mm ahead of the notch tip. Thisobservation is in line with the earlier results fromuniaxial creep tests with a radial sample from the weldroot. The weakness only manifests itself in long-termtesting because the cavity nucleation and growth processis a slow process. Because of the low strength of theoxide particle zone welding in air should be avoided andvacuum or inert gas should be used instead.

Topics

• impedance spectroscopy
• experiment
• strength
• copper
• creep
• creep test