Creep fracture of zirconium alloys

Theoretical approaches utilized to predict the lifetime of spent nuclear fuel in interim dry storage assumed that diffusion controlled cavity growth controlled the failure time under these conditions. DCCG, however, fails to account for the fact that the failure time is related to the strain rate in Zircaloys according to the Monkman–Grant relationship. This paper will show that constrained cavity growth, which can account for the Monkman–Grant relationship but was not considered in the spent nuclear fuel lifetime prediction models, is more relevant to failure of spent nuclear fuel in dry storage. Contrary to reports in the past, constant stress creep tests performed in this study on Zircaloy-2 suggest that creep cavity nucleation and/or growth occurs prior to tertiary creep. Constant strain rate creep rupture tests on Zircaloy-2 show strong evidence of extensive cavity nucleation and growth near and at the fracture surface, indicating a creep cavitation failure mechanism under these conditions.