Corrosion and Contamination of 316L Stainless Steel in Simulated HNO₃-Based Spent Nuclear Fuel Reprocessing Environments with Cesium and Strontium

Austenitic 316L stainless steel is usually used as the structural material in spent fuel reprocessing facilities. However, the contamination of fission products from spent fuel (especially Cs and Sr) on the surface of facilities will greatly affect its safe decommissioning. In this study, for the first time, with the combination of characterizations of electrochemistry and laser-induced breakdown spectroscopy with two channels, the corrosion and contamination of 316L stainless steel were analyzed in simulated reprocessing environments with HNO₃concentrations of 3, 6, 8, and 12 M HNO₃containing Cs and Sr for 7, 14, 21, 30, and 60 days, respectively. The stability order of the passive film of 316L stainless steel in various environments was 12 M HNO₃> 8 M HNO₃> 3 M HNO₃> 6 M HNO₃. Combined with other characterization methods, a mechanism was proposed. It was found that SrCO₃, in the matrix, was the main contaminant in the initial 7 days in all environments due to a large number of holes. Then, the dissolution of contaminated steel surface led to the decrease of contaminant, and recontamination occurred after the repassivation of steel. These findings have significant implications for the development and selection of decontamination technology for the contaminated facilities made of 316L stainless steel.