| The structural material to contain the target material, used in transmutation of spent nuclear fuel, may develop residual stress due to different forming processes. Nondestructive neutron diffraction (ND) and positron annihilation spectroscopy (PAS) techniques have been utilized to characterize residual stress in martensitic Alloys EP-823 and HT-9, subjected to cold-reduction, plastic deformation and welding. The ND measurements revealed tensile residual stresses on the top and bottom surfaces of the cold-worked specimens. The residual stress was enhanced in cylindrical specimens with increased plastic-deformation. Post-weld-thermal-treatment was beneficial to reduce internal stresses in welded specimens. The line-shape-parameters (S, W and T) obtained from the PAS spectrum were related to the residual stress developed in cold-worked and plastically deformed specimens. The dislocation density determined by transmission electron microscopy was enhanced at higher cold-reduction levels. Fractographic evaluations by scanning electron microscopy revealed ductile failures in cylindrical specimens. |
