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In this study, the parameters for underwater laser cutting of 50-mm thick stainless steel, which is typically used in nuclear power structures, are investigated. The focal position of laser beam significantly affects the cutting quality. In particular, in the cutting of the thick sample, change in the focal position determines the kerf width and the roughness of the cut surface. Moreover, the effects of the variation of kerf width and the cut surface characteristics on the focal position of the laser beam are investigated. As the focal position moved to the inside of the material, the upper kerf width increased, but the quality of the cut surface was improved.

A basic study was conducted to investigate the correlation between assist gas pressure and the amount of secondary waste generated during underwater laser cutting for nuclear decommissioning. The assist gas pressure, i.e. the main parameter, was changed from 2 to 15 bar. Cutting quality was evaluated based on the shape of the cutting cross-section and the roughness of the cutting surface. In addition, the weight loss closely related to the generated secondary waste was calculated, and the schlieren method was used to check the gas flow according to the assist gas pressure. Satisfactory cutting quality could be obtained at a minimum assist gas pressure of 10 bar, and the weight loss related to secondary waste was less. When the cutting quality was good, the weight loss was less, and secondary waste generated was minimum.

In this study, the parameters for underwater laser cutting of 50-mm thick stainless steel, which is typically used in nuclear power structures, are investigated. The focal position of laser beam significantly affects the cutting quality. In particular, in the cutting of the thick sample, change in the focal position determines the kerf width and the roughness of the cut surface. Moreover, the effects of the variation of kerf width and the cut surface characteristics on the focal position of the laser beam are investigated. As the focal position moved to the inside of the material, the upper kerf width increased, but the quality of the cut surface was improved.