| Among the reactor systems recommended in Generation IV, the Supercritical Water Reactor(SCWR) has been paid more and more attentions in recent years because of its high economical efficiency and safety. Generally, the described service condition for SCWR is25MPa and above500℃. On such a severe condition, Zr-based alloy cladding material suitable for Light Water Reactor(LWR) will be unacceptable. One of the two challenges about SCWR is material, especially for the fuel cladding.High temperature creep tests of Ni-based alloy C276, one of the candidate materials for the fuel cladding, were carried out at600℃-750℃, with stress130MPa-500MPa. The effects of stress and temperature on creep were investigated, the change laws of the steady state creep rate with stress and time to rupture were analysed, the relations between time to rupture and stress were revealed, and the rupture reliability predicted by Monkman-Grant formula and L-M method respectively was compared. Methods of damage mechanics were adopted to calculate and analyze these data. Damage factors calculated by Kachanov’s formula and Norton’s formula based on θ projection method were compared. The results show that C276has prominent creep property and exists two types of primary creep characteristics:Type Ⅰ creep characteristic at650℃,700℃and750℃with low stress and Type Ⅱ at650℃,700℃and750℃with high stress and600℃, respectively. And C276has a consistent linear relationship between the steady state creep rate and the applied stress in the logarithm coordinate system at600℃with low stress and650℃,700℃and750℃, but deviating the linear relationship at600℃with high stress. The damage factors about the material are similar at650℃,700℃and750℃according to Kachanov’s formula. Moreover, the damages calculated by Norton’s formula start at about0.3-0.4of the lifetime, and the damage factors calculated by Kachanov’s formula are relatively conservative. |
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