Corrosion performance of Inconel 690 in alkaline media doped with dissolved strontium and cesium species: a study via laser-induced breakdown spectroscopy

In alkaline spent fuel storage environments, the interaction between fission products such as 90 Sr and 137 Cs and structural alloys poses significant challenges for nuclear facility decommissioning. In this study, Inconel 690 specimens were immersed in simulated alkaline media containing stable isotopes of strontium and cesium, and laser-induced breakdown spectroscopy (LIBS) was employed to monitor the accumulation of these elements on the alloy surface. Results indicate that surface contamination peaked after 14 days and stabilized at around day 21. Based on the analysis of surface morphology, elemental distribution, grain size, surface roughness, and oxidation states, a contamination mechanism is proposed: Sr initially deposits on the alloy surface. Over time, Sr continuously accumulates and diffuses into the matrix. At day 21, the Sr signal intensity plateaus, indicating that an equilibrium is reached between Sr enrichment in the oxide layer and that in the substrate, and the diffusion process stabilizes. Cesium, however, exhibits a greater tendency to remain in the near-surface regions.