High fidelity model of pipe bundle coupling mechanism in nuclear fusion plant remote maintenance

Periodically maintenance of Plasma-Facing Components (PFCs) are one of the critical issues in DEMOnstration (DEMO) reactor. The harsh environment of a fusion reactor dictates remote maintenance, which requires the development of new strategies and technologies. Indeed, a Service Joining System (SJS) for in-bore cutting and welding has been designed for PFC replacements. Therefore, strict alignment requirements between welding surfaces must be ensured. The alignment task involves a first phase of positioning during which the new pipes are brought close to their final position, and in the second phase a robot system ensures precise pipe coupling. This paper presents the high-fidelity model of the Laser Bore Joint (LBJ), focusing on the pipe bundle coupling mechanism. The flexible elements of the LBJ have been described using both analytical and Finite Element Analysis (FEA). The bellow stress-strain diagram has been obtained, which shows the effect of its anelasticity when the alignment force increases. Furthermore, the Lumped Parameter Model (LPM) of the bellow and their use in the LBJ multibody model are presented. Finally, the contact parameters and two different cuff designs of the LBJ are analyzed. The simulation results are shown and discussed.