EVALUATION OF FIBER LASER CUTTING AND CRUSHING APPLIED TO THE REMOVAL TECHNOLOGY OF FUEL DEBRIS AND IN-VESSEL STRUCTURES

摘要

Decommissioning of Fukushima Daiichi Nuclear Power Plants (NPPs) is an important problem in Japan. In the decommissioning, remote handling techniques are necessary to remove the fuel debris which is solidified by mixed molten materials composed of fuels and invessel structures. In terms of remote handling, a laser beam can penetrate a narrow gap and it can shoot the substance without reactive force. Moreover, a fiber laser can be operated in continuous wave (CW) mode as well as in pulsed mode. Thus, a laser has been expected as one of the useful decommissioning tools. In this paper, to evaluate the cutting and crushing performances, we performed thick metal cutting and crushing for various materials using a fiber laser system. A continuous wave mode and pulsed mode make it possible to cut a 30 mm thick SS400 steel plate and to crush a 10 mm thick alumina pellet. Moreover, we succeeded to cut a metalceramic mixture materials using high-power fiber laser, in combination with x-y-z tri-axes control system, laser scanner. It is hoped that the outcome of the present study would be of some use to develop remote cutting and crushing technique for the decommissioning of the Fukushima Daiichi NPPs.