A laser-based cutting technique is able to reduce hazardous waste leakage by up to 95%, giving it application in the decommissioning of nuclear reactors. Researchers at Lazer Zentrum Hannover (LZH) developed and validated the process, successfully dismantling reactors underwater. In direct dismantling, a reactor’s components are disassembled on site within the cooling water. What makes the method developed by the Underwater Technology Group at LZH so effective is that in laser cutting, the melt from the joint remains attached to the sheet during the cutting process. Laser optics developed by LZH for underwater disassembly of power plant components. Courtesy of LZH. The researchers demonstrated the method at the Hannover Underwater Technology Center of Leibniz University. They cut stainless steel sheets at a depth of 4 m. To achieve this task, the team developed and built laser optics optimized for cutting power plant components underwater. The experiments were conducted with a mobile disk laser from LZH spinoff Laser on Demand GmbH. As part of the validation, the LZH’s Underwater Technology Group along with its partner Orano GmbH elevated the process from laboratory scale to near-industrial conditions, corresponding to Technology Readiness Level 6. In currently used processes that use sawblades or waterjets, materials from the joint and additional abrasives can be transferred into the cooling water, which then must be decontaminated, adding significant cost. Successful test in the Hannover Underwater Technology Center, at a water depth of 4 m, the scientists could successfully cut through stainless steel sheets. Courtesy of LZH. The team optimized its parameters for laser power, gas pressure, and cutting speed, which reduced the weight loss when cutting stainless steel sheets by up to 95%. Correspondingly, less secondary waste passes into the water. Members reported that the method worked with similar levels of effectiveness with zirconium alloys, another common material used in reactor components.