At Cadarache in southern France, an international research project has been working since 2007 to build a nuclear fusion reactor known as the ITER (International Thermonuclear Experimental Reactor). The long-term objective of the project is to use energy from the fusion of hydrogen atoms to generate electricity. For the fusion of hydrogen, the fuel (hydrogen) will be heated in the ITER reactor to a temperature of 150 million degrees Celsius. This process creates plasma, which cannot be permitted to come into contact with other components.
The ITER reactor utilises the Tokamak principle, whereby a circular type of fusion reactor encloses the plasma in a vacuum by means of superimposed magnetic fields. After its anticipated completion in 2025, the ITER will be the largest Tokamak fusion reactor in the world, with a plasma radius of 6.2 m, a plasma volume of 840 m³, and a fusion energy output of 500 MW. This requires an enormously complex machine with a total weight of 23000 t and over 10 million components.
ITB GmbH works in partnership with CADFEM GmbH and the ITER Organization to perform various calculations in the fields of thermals and structural mechanics.
Tolerance analyses
The magnet system of the ITER reactor is constructed from components of enormous size and weight. An important component of the magnet system is the so-called 18 D-shaped magnetic coils (toroidal field coils). Each of these 18 magnetic coils weighs 310 t, is 9 m long, and is 16.5 m high. At the same time, the positioning of the magnetic coils is subject to tolerances of just a few millimeters.
In order to calculate the loads applied to the various connecting elements between the individual coils, a finite element model was created of the major components of the entire ITER reactor and optimized by ITB GmbH for purposes of the calculation. Using this model, tolerance analyses were carried out by our companies to investigate the influence of deviations from the reference geometry on the load of the connecting components.
The journey of the magnetic coils from delivery to installation in the ITER reactor
Special tools are required to work with magnetic coils of this magnitude. Two of these tools are the so-called up-ending tool and the sub-sector-assembly tool. The up‑ending tool is used to upend the magnetic coils from a horizontal transport position into their final vertical position. In order to ensure that the magnetic coils are not damaged by this movement, a corresponding FE model was created and used to determine and evaluate the stresses on the magnetic coils and up-ending tool during erection.
The sub-sector-assembly tool is used to position two upended magnetic coils relative to one another, and to connect them together using further components, before the sector consisting of two magnetic coils and other components is transported to its final position in the machine. FEM calculations for the sub-sector-assembly tool were used to investigate various scenarios to determine the effect of deviations from the reference situation in position or geometry could have on the positioning of components relative to one another, and to their stresses.
Durability analyses for individual components during routine operation of the ITER reactor
For the various connecting elements between the individual magnetic coils, local tension and expansion states were determined by means of submodels and, based on these results, durability analyses of these components were carried out.
The views and opinions expressed herein do not necessarily reflect those of the ITER organization.
