In reprocessing spent nuclear fuel, it is necessary to shear fuel pins to dissolve fuel pellets. In fast reactor fuel, the fuel pins are covered with a hexagonal wrapper tube, and a disassembly device is required to remove the wrapper tube from the fuel assembly and separate only the fuel pins for the following shearing stage. The disassembly technologies as laser cutting or mechanical cutting using cutting-off wheel (CW) have been conventionally studied, but some problems such as damage of fuel pins and the CW have been pointed out.In order to solve these problems, cutting tests based on the latest knowledge were carried out using the fiber laser and the CW for the work pieces partially simulated the shape and materials of the fuel assembly. Cutting tests using the fiber laser were carried out as parameters of cutting speed, output, focal length, and assist gas pressure. The CW tests were carried out as parameters of CW type, peripheral speed, and feed speed. And in the CW tests, damage reduction of the CW was examined by monitoring motor current of the CW. In the fiber laser, the effects of various parameters on cutting performance were investigated, and the selection of optimum cutting conditions and locations to reduce thermal damage on fuel pin damage, the disassembling time, and the applicability of high power laser to the disassembly of various fast reactor fuel assemblies were evaluated. For the CW, a CW with cubic boron nitride (CBN) outer blade was selected as the cutting tool. In addition, the selection of the optimum cutting conditions, the durability to disassemble one or more fuel assemblies with one CW, the operation procedure to reduce CW damage by feed speed control by feedback of motor current, and the effect of the CW side surface with outer blade on grinding resistance were verified. The applicability to the disassembly of fast reactor fuel assemblies was evaluated by fundamental tests using fiber laser and the CBN CW.In order to investigate the effect of the disassembly operation continuity and fuel assembly shape on disassembling, an engineering scale test equipment using the CBN CW was produced experimentally, and cutting tests were carried out. Problems in handling and procedure of fuel assembly assumed in the real machine disassembly machine were extracted. Regarding the structure and operation method of the fuel assembly, the following were examined: Control of feed speed with changes in the thickness of the wrapper tube, improvement measures to prevent damage due to CW pinching at the cutting of the final surface of the wrapper tube, and support structure (knock bar) without falling off after cutting&nbsp; fuel pins.The results of disassembly technologies of fuel assembly will be utilized for the plant, equipment and operation planning in the reprocessing of the fast reactor fuel.

Feasibility Study of Disassembly Technologies of Fast Reactor Fuel Assembly

Paper Proceedings: https://asmedigitalcollection.asme.org/ICONE/ICONE28/volume/85246

2021 28th International Conference on Nuclear Engineering (ICONE28)

Supporting the need among researchers worldwide for additional online and multimedia content, ASME now offers the ASME Conference Video Collection. This platform will collect and provide long-term access to conference presentation videos, encompassing all technology areas within ASME's technical conference and events program. About 30,000-40,000 engineers across all mechanical engineering and related disciplines participate in ASME conferences each year. This includes authors of approximately 6,000 to 8,000 technical papers published by ASME, the majority of whom also submit video presentations for our virtual conferences. The video collection will be available as an add-on to existing product packages or as a separate subscription.