Near-IR Laser Ablation of Simulated Radiologically Contaminated Oxides on Carbon Steel Feeder Pipes

Abstract

Removing radioactive oxide layers is a strategy for minimizing the volumes of radio-contaminated metallic wastes produced during reactor decommissioning. Laser ablation oxide removal offers the advantages of remote operation, waste minimization, and avoiding worker radiation exposure. In this project, simulated oxides were produced on carbon steel by varying the solution pH, ionic strength, and applying γ-radiation. The oxides were removed via ablation using a 1064 nm ytterbium fiber laser. The corroded samples were analyzed before and after laser cleaning using optical microscopy, scanning electron microscopy, Raman spectroscopy, and energy-dispersive X-ray spectroscopy. The oxides consisted of a magnetite sublayer with overlying Fe^III oxide islands with total thickness up to 200 μm. After optimizing the laser scanning parameters, complete oxide removal was achieved with an irradiance of 200 MW/cm². The particle collection efficiency using a 0.3 mm layer of glass fiber HEPA filter paper was 98%. The results show that laser ablation using an ytterbium fiber laser and oxide collection using HEPA filter media is a feasible technique for removal of radio‐contaminated iron oxides from reactor component metal surfaces.