Analysis and Modeling of the Laser Bore Joint to Prevent Alignment Failures

The DEMOnstration (DEMO) reactor, the next-generation fusion power plant, requires plasma-facing components (PFC) to be periodically replaced during the reactor lifetime. However, a remote maintenance (RM) is needed due to neutron activation. A relevant RM operation is the replacement of piping supplying around the plasma chamber using a Service Joining System (SJS) for in-bore cutting and welding. Welding operation demands strict alignment requirements obtained with appropriate RM strategy. Therefore, alignment task involves a first phase of positioning during which the new pipes are brought close to their final position by a main system, and in second phase a robot system drives pipes extremity achieving precise coupling. This paper presents the multibody model of Laser Bore Joint (LBJ) of SJS focusing on flexible elements, named bellows, that provide compliance both in axial and radial direction during alignment tasks. The LBJ model is built in Adams environment and a suitable sensors layout is devised to assess the misalignment state in the case of failure in the first alignment phase. The secondary handling device is introduced and its control strategy is implemented in a co-simulation framework with the multibody system. Results underline the feasibility of proposed alignment procedure.