High-Power Laser Delivery in Nuclear Environment Using Radiation-Hardened Fibers via Controlled Chlorine and Hydroxyl Content.

The metallic cladding of spent nuclear fuel rods in nuclear power plants can be safely and efficiently cut using fiber lasers. Therefore, it is of great importance to develop silica fibers capable of transmitting high-power laser in high-radiation environments. However, inherent hydroxyl (OH) and chlorine (Cl) impurities in silica fibers adversely affect their radiation resistance. To fabricate silica fibers with high radiation resistance, this study prepared a series of glass samples with varying Cl/OH content using the Vapor Axial Deposition (VAD) method. The effects of radiation on the optical properties of the samples with different impurity concentrations, along with the underlying mechanisms, were investigated using absorption spectroscopy, photoluminescence spectroscopy, electron paramagnetic resonance (EPR), and photothermal absorption microscopy. Passive delivery fibers with a core diameter of 100 μm were fabricated using the rod-in-tube method. The influence of OH and Cl impurities on the fiber attenuation, laser delivery performance, and temperature rise coefficient was studied. The results indicate that the radiation resistance of medium-OH, Cl-free fibers is far superior to that of low-OH, high-Cl fibers. This research provides a reference for applying high power laser technology in high-radiation scenarios.