REFLET Experiment in OSIRIS: Relaxation under Flux as a Method for Determining Creep Behavior of Zircaloy Assembly Components

A stress relaxation on bent-beam specimen irradiation campaign was performed in the French material testing reactor OSIRIS in order to screen different materials according to their in-flux behavior and to derive constitutive laws that are used to describe the in-reactor behavior of assembly components under axial stress. This paper presents the methodology used, with particular emphasis on the validation of the different hypotheses. The methodology is illustrated with the results obtained on an industrial Zircaloy-4 (Zy-4) alloy used in guide thimbles. As an illustration of the capability of the method, the parameters of simple creep behavior laws are adjusted to the relaxation results. The creep-law predictions are compared to results obtained previously in a creep experiment.