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Creep performance of OFP copper for the overpack of repository canisters

Published online by Cambridge University Press:  21 March 2011

Pertti Auerkari ,
Stefan Holmström ,
Jorma Salonen  and
Pertti Nenonen
Pertti Auerkari
Affiliation:
VTT Industrial Systems, PO Box 1704, FI-02044 VTT, Espoo, Finland
Stefan Holmström
Affiliation:
VTT Industrial Systems, PO Box 1704, FI-02044 VTT, Espoo, Finland
Jorma Salonen
Affiliation:
VTT Industrial Systems, PO Box 1704, FI-02044 VTT, Espoo, Finland
Pertti Nenonen
Affiliation:
VTT Industrial Systems, PO Box 1704, FI-02044 VTT, Espoo, Finland
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Abstract

To experimentally assess the long term creep performance of oxygen-free phosphorus- doped (OFP) copper for the overpack of repository canisters, the combination of modestly elevated temperature and multi-axial stress state has been applied for accelerated testing. Multi-axiality was induced by using notched compact tension (CT) specimens, with interrupted testing to periodically inspect for creep damage. Uniaxial creep testing was also conducted to support creep analysis of the CT specimens. After about 10000 h of testing at 150°C/46 MPa (reference stress), the inspected CT specimens showed only marginal creep cavity indications near the notch tip. However, a distinct grain boundary zone with elevated Pcontent was observed to appear and widen during testing, mainly near the notch tip. The significance of the grain boundary zone is not well understood, but indicates stress-enhanced microstructural changes at relatively low temperatures. The predicted isothermal uniaxial creep life at 150°C/46 MPa agreed satisfactorily within a factor of two in time, when obtained independently from converted multi-axial testing results and directly from a creep model based on the available uniaxial data. Although the uncertainties in extended extrapolation remain large, the prediction would suggest safe long term service at leastagainst pure creep failure of intact parent material.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 932: Symposium – Scientific Basis for Nuclear Waste Management XXIX , 2006 , 23.1
Copyright
Copyright © Materials Research Society 2006

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References

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