A test program on a reactor core material originating from the bottom end of a VVER absorber element is being carried out in aim to characterize the changes in mechanical properties and the occurrence of irradiation assisted stress corrosion cracking in PWR environments by laboratory tests. The mechanical and microstructural properties of the absorber bottom end material have changed due to neutron exposure. However, the material's response to neutron irradiation differs from the usual response of austenitic stainless steels. Yield strength, tensile strength, and dislocation loop density are all lower than expected. An enhancing effect of Ti-carbide precipitations on the defect density is another new finding of interest. High defect density close to the Ti-carbides is presumed to result from the stress/strain field caused by the precipitations.
