Corrosion behavior of Alloy 690 and Alloy 693 in simulated nuclear high level waste medium

Nickel based alloys are candidate materials for the storage of high level waste (HLW) generated from reprocessing of spent nuclear fuel. In the present investigation Alloy 690 and Alloy 693 are assessed by potentiodynamic anodic polarization technique for their corrosion behavior in 3 M HNO3, 3 M HNO3 containing simulated HLW and in chloride medium. Both the alloys were found to possess good corrosion resistance in both the media at ambient condition. Microstructural examination was carried out by SEM for both the alloys after electrolytic etching. Compositional analysis of the passive film formed on the alloys in 3 M HNO3 and 3 M HNO3 with HLW was carried out by XPS. The surface of Alloy 690 and Alloy 693, both consists of a thin layer of oxide of Ni, Cr, and Fe under passivation in both the media. The results of investigation are presented in the paper.

► Alloy 690 & Alloy 693, both possess good corrosion resistance in simulated HLW.
► SEM & EDS confirms the presence of Cr rich precipitates for both the alloys.
► Passive film stability of Alloy 690 was found to be higher than Alloy 693.
► Both alloys possess few micro pits even at a concentration of 100 ppm Cl- ion.