In response to the national policy of low carbon emissions, the vigorous development of nuclear energy technology is a necessity, and the safe and effective disposal of high-level radioactive waste liquid generated from nuclear energy development is crucial to public safety. Vitrification technology for nuclear waste is relatively mature in the current nuclear industry, and this technology has evolved through four generations: the pot method, the calcination + induction metal melter method, the Joule-heated ceramic melter method, and the cold crucible method. Fiber lasers exhibit core advantages including high electro-optical conversion efficiency, high beam quality, high system stability, and low maintenance cost. Using a laser as a heat source enables operations such as rapid heating, melting, holding at constant temperature, and annealing, which undoubtedly simplifies many steps in traditional vitrification. Moreover, heating with a fiber laser allows flexible responses to special circumstances during the nuclear waste vitrification process; for example, the laser can be remotely shut off at any time to add glass feed material, and the laser irradiation area can be freely controlled. This study aims to investigate the use of a high-power fiber laser as a replacement for conventional heat sources to achieve vitrification of high-level radioactive waste liquid via laser sintering of zirconium-containing borosilicate glass. Compared to conventional sintering methods, laser sintering can achieve higher temperatures, faster sintering rates, higher mechanical strength of the glass material, and lower energy consumption, and it allows free control of the local sintering temperature.

In the experiment, a laser vitrification method was adopted. A high-power fiber laser was utilized to generate a high-quality and highly directional laser beam. The laser energy was then delivered through the built-in lens of the laser output head to irradiate the glass vitrified form, thereby achieving the vitrification of high-level radioactive waste liquid.

The following results were obtained. X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses revealed that the laser-sintered borosilicate glass maintained a complete and smooth glassy phase when the mass fraction of zirconium dioxide (ZrO₂) was in the range of 0%-8%. When the ZrO₂ mass fraction reached 9%, zirconium precipitated in the form of zirconium silicate (ZrSiO₄) (Fig.4 and Fig.5). Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy analyses showed that melting ZrO₂ into the borosilicate glass network consumed free oxygen, and the degree of network connectivity within the glass gradually increased with the amount of ZrO₂ incorporated into the glass network (Fig.6~Fig.8 and Table 3). The density of the laser-vitrified product also increased with the amount of melted ZrO₂, reaching a maximum density of 2.803 g/cm³ (Fig.9).

The results show that it is feasible to use a laser to replace conventional heat sources for the vitrification of high-level radioactive waste. The prepared glass exhibits a glassy phase. Furthermore, the trends in glass microstructure and composition changes observed in the laser-prepared glass are essentially consistent with those obtained by conventional heating methods, verifying the application potential of lasers in the field of vitrification. The results of this study provide a reference for the application of fiber lasers in the field of nuclear waste vitrification.