Electromagnetic and mechanical analyses of the ITER electron cyclotron Upper launcher steering M4 mirrors for the vertical displacement event

• Published in: Fusion engineering and design 2020-10, Vol.159, p.111941, Article 111941
• Main Authors: Mas Sánchez, Avelino, Chavan, René, Goodman, Timothy, Santos Silva, Phillip, Vagnoni, Matteo
• Format: Article
• Language: English
• Subjects: Bending moments; Cyclotrons; Design analysis; Electromagnetic analysis; ITER; Launchers; Loads (forces); Mechanical analysis; Millimeter waves; Nuclear power plants; Steering; Steering mirrors; Structural integrity; Upper launcher; Wave power; Waveguides
• ISSN: 0920-3796; 1873-7196
• DOI: 10.1016/j.fusengdes.2020.111941

•An analysis strategy was developed to evaluate the mechanical integrity of the M4 mirrors against the loads occurring during the VDEIII scenario.•The analyses show that most of the current density, and therefore the volumetric forces are induced in the reflecting surfaces.•The simulations of the M4 mirrors produces categorized stresses lower than the allowable limits defined in the ASME code.•Additional analyses covering all the rest of applicable load combinations shall be carried out to fully validate the design of the M4 mirrors. The mm-wave power exiting the eight In-Vessel waveguides inside the ITER Electron Cyclotron Upper Launcher is reflected by three fixed mirror sets and finally aimed by two independent steering mirrors to specific plasma locations. A design solution for both Upper and Lower Steering M4 Mirrors capable to withstand the loads taking place during normal operation was already proposed. This design is now assessed against the Vertical Displacement Event Category III (VDEIII) linear decay (36 ms) scenario, which was identified as one of the most stringent load combinations for the steering M4 mirrors. This paper reports the analyses performed to quantify the mechanical loads induced in the steering M4 mirrors during the VDEIII scenario as well as the structural integrity assessment to validate the design against these loads. The transient electromagnetic simulations show that the highest forces are induced in the reflecting surfaces, which produce a bending moment that tends to rotate upwards the mirrors. The comparison between the categorized stresses obtained from the transient mechanical analyses and the allowable design limits according to the ASME code shows that the design of the steering M4 mirrors is widely capable of withstanding the expected loads taking place during the VDEIII scenario.