Combined effect of radiation damage and hydrides on the mechanical behavior of Zr and Zry-4

This work aims to define the grade of hardening by irradiation in Zr and Zry-4 with hydrogen, mainly in the form of hydrides and to analyze if they have any effect on the recovery from damage to nuclear reactor components in service. Early brittleness of components like the sheaths of fuel elements is due to the presence of intermetallic phases as well as to damage from the radiation generated by the material. The mechanical behavior of these alloys during the interaction between these two factors is not yet fully understood. The entrance of hydrogen and damage by radiation occur simultaneously in the nucleus of a power reactor. This work analyzed the grade of hardening in zirconium with different grain sizes and with two contents of hydrogen, and in Zry-4 with a low hydrogen content, irradiated with neutrons at room temperature, at doses below where the appearance of inhomogeneities is expected in the deformation. The irradiations were carried out in CNEA's RA1 reactor and the mechanical tests consisted of uniaxial traction. Isochrone was annealed to determine the hardening recovery temperatures for the irradiated and hydrated material. Behavior in accordance with the classic model for disperse barriers was obtained for Zr with hydrogen contents less than 20 ppm and 100 ppm, at doses below 0.0008 dpa (3,6 x 1017 n/cm2): the hardening at room temperature for the hydrogen content up to these doses acts as an additive to the hardening by irradiation. The annealed isochrones show that the recovery from the hardening in material with hydrogen occurs at temperatures above 450oC , close to 100oC above those for the material without hydride. These results suggest a very strong link between the defects created during irradiation and the hydrogen present in the material, which leads to a big reduction in ductility, even at low doses of irradiation (CW)