The creep rupture properties of beta-phase Zircaloy-2 cladding in the region 1000-15000C

Accurate creep parameters are essential for the prediction and assessment of fuel cladding behaviour under reactor accident conditions. To resolve uncertainties in the limited data available for beta-phase Zircaloy cladding, an extensive programme of isothermal stress rupture tests have been undertaken for Zircaloy-2 tubes in a non-oxidizing environment at temperatures from 1000 to 15000C. The secondary creep parameters are calculated from an analysis of the strain histories obtained from each test using a novel photo-electronic technique for the continuous monitoring of tube deformation. The resulting creep equation is compared with recent rupture life data for Zircaloy tubes. The analysis also identifies an anomalous primary stage which significantly retards the early stage for low stress tests at 12000C and above and which is found to be extemely sensitive to prior annealing. The influence of this primary component on predictions of cladding behaviour is assessed. (Auth.)