Marcello Losasso

Status of the Procurement of the European Superconductors for the ITER Magnets

The European share of the ITER magnet superconductors includes the supply of around 20 km of Toroidal Field and 7 km of Poloidal Field conductors. This represents 20% and 11% of the total conductor amounts respectively needed for all ITER Toroidal Field (TF) and Poloidal Field (PF) coils. For TF conductor, around 97 tons of superconducting niobium tin strand and 60 tons of copper wire are needed to be purchased, cabled and inserted within a stainless steel jacket tube to form the Cable-In-Conduit-Conductor (CICC). For PF conductor, about 45 tons of superconducting multifilamentary niobium titanium wire need to be cabled and jacketed. Altogether, Fusion for Energy (F4E) placed 4 supply contracts for the European TF and PF coil conductors (one for copper strand, two for niobium tin strand and a single contract for cabling and jacketing). In addition, the PF conductor procurement is based on a bi-lateral agreement with the Russian Federation Domestic Agency (RF DA) where NbTi cables are supplied by RF DA and their jacketing is provided by F4E. In this article, the procurement strategy and the current procurement status are reported for the European contribution of TF and PF conductors.

Status of the F4E Procurement of the EU ITER TF Coils

The ITER magnetic system includes 18 Toroidal Field (TF) Coils using Nb3Sn cable-in-conduit superconductor. Each TF coil, about 300-t in weight, is made by a Winding Pack (WP) composed by 7 Double Pancakes (DP) modules stacked together, impregnated and inserted in stainless steel coil case. Each DP is made by a Radial Plate (RP), a very large D-shaped stainless steel plate with grooves machined on a spiral path on both sides, in which the insulated conductor is inserted after the heat treatment. The procurement of the TF coils will be carried out by Fusion for Energy (the European Domestic Agency (DA)), responsible for 10 coils (including 1 spare coil) and the Japanese DA, responsible for 9 coils. The conductors will be produced by 6 different DAs, while the coil cases only by the Japanese DA. In July 2008 the Procurement Arrangement was signed between the ITER Organization (IO) and F4E defining the scope, technical and management requirements for the procurement of such coils. F4E has developed a procurement strategy aimed to minimize costs and risks, consisting of subdividing the procurement into three main procurement packages, each foreseeing an initial R&D qualification phase. One procurement package is related to the construction of 72 RP (including 2 prototypes), another to the fabrication of the 10 WP and a third to the cold test and coil-case insertion of 10 WP. So far F4E has signed 5 contracts. In 2009, we placed 2 contracts for the procurement of RP prototypes and 1 contract for the development and qualification of the welding and the Ultrasonic Test technologies for the coil case welding. In 2010 1 contract has been placed for the construction of 10 WP and 1 contract for the engineering optimization of the cold test and coil insertion.

Progress in the F4E Procurement of the EU ITER TF Coils

The ITER magnetic system includes 18 Toroidal Field (TF) Coils constructed using Nb3Sn cable-in-conduit superconductor. Each TF coil comprises a Winding Pack (WP) composed of 7 Double Pancake (DP) modules stacked together, impregnated and inserted into a stainless steel coil case. Fusion for Energy [the European Domestic Agency (DA)] is responsible for the procurement of the ten while the Japanese DA is responsible for remaining nine coils. The conductors are being produced by 6 different DAs, while the coil cases only by the Japanese DA. F4E has implemented a procurement strategy aimed to minimize costs and risks, consisting of subdividing the procurement into three main procurement packages, each foreseeing first an R&D and qualification phase. One procurement package is related to the construction of 72 radial plates (RP), another to the fabrication of the ten WP, and a third to the cold test and coil-case insertion of ten WP. In collaboration with industry, F4E has successfully produced two RP prototypes. Regarding the DP, the construction of the first DP prototype has started. In this paper, we will report on the results achieved so far and the status of each of the procurement packages.

Status of the F4E Procurement of Radial Plate Prototypes for the EU ITER TF Coils

This paper reflects the status of the manufacturing of 2 Radial Plate prototypes for the EU ITER TF Coils. The production of these prototypes will supply valuable information for the manufacturing of the total required number of 70 Radial Plates, in terms of manufacturing technologies, optimization of cost, manufacturing time and risks.

The European Procurement of Cold Test and Case Insertion of the ITER Toroidal Field Coils

The International Thermonuclear Experimental Reactor is an international scientific project with the aim of building a tokamak fusion reactor capable of producing at least 10 times more energy than that spent to sustain the reaction. In a tokamak the fusion reaction is magnetically confined and the toroidal field coil system plays a primary role in this confinement. Fusion for Energy, the European Domestic Agency for ITER, is responsible for the supply of 10 out the 19 toroidal field coils. Their procurement has been subdivided in three main work packages: the production of 70 radial plates (the structural components which will house the conductors), the manufacture of 10 winding packs (the core of the magnet) and cold test and insertion into the coil cases of 10 winding packs. The cold test/insertion work package presents significant technological challenges. These include the cold test of the winding packs 14 m high, 9 m wide and weighing 110 t, the welding and inspection of the 316 LN stainless steel coil case, with welded thicknesses of up to 144 mm accessible only from one side combined with the need to minimize the deformation during the welding process (more than 70 m of weld per coil and up to 90 passes to fill the chamfer) and the resin filling of the coil case after insertion of the winding pack (the total volume to be filled up is about one cubic meter per coil). From 2009 up to mid 2011, F4E has carried out an R&D program in order to investigate the most challenging steps of the manufacturing processes associated to this work package, both to meet the demands of the ITER schedule and to minimize technological risks; in this paper an overview of the results obtained is presented.

He-Inlet of the Toroidal Field Coil: Qualification and Manufacturing Status

In this paper, we will report on the manufacturing of 6 helium inlet mock-ups for the EU ITER TF coils, and on the results of the mock-up tests and other qualification activities carried out in the European industry on this subject.

The Electrical Insulation of Large Superconducting Magnets

The latest generation of fusion devices needs large superconducting magnets that have to withstand operational voltages of tens of kV. Their insulation typically targets a dielectric strength of about 10 times the operational voltages to cope with degradation during operation resulting from the high electromagnetic loads with cyclic components, thermal stresses due to cycles from 293 K to 4 K, and ionizing radiation. Degradation of dielectric strength is further mitigated by applying solid polyimide overlapped layers in the insulation. The level of Lorentz forces, together with the large superconducting coil sizes, makes high-voltage tests impossible to realize under exact operational conditions. The fact that insulation is very difficult or even often practically impossible to repair in case of electrical fault, requires sound insulation design to reach utmost quality. In this paper, we will discuss the build-up of the electrical insulation in large superconducting magnets both from the manufacturing and operational point of view. In particular, the impact of the insulation design and manufacturing choices on the quality will be discussed in depth. We will also discuss the implementation and the application of insulation systems.

Progress on the ITER TF Coil Winding Pack in EU

A principal part of the ITER fusion reactor is the Toroidal Field magnet system which consists of 18 “D” shaped coils. Fusion for Energy, (F4E), the European Domestic Agency for ITER, is responsible for the procurement of 10 such coils. The completed coils, measuring approximately 14 m × 9 m and weighing 300 tons, comprise an outer structural case into which a “winding pack”, itself made up of 7 conductor double pancake and radial plate assemblies, is inserted. The winding packs will be the largest ever built using Nb3Sn conductor and their manufacture, using a wind, react and transfer process, presents significant technological challenges. In particular, the conductor double pancakes must be wound with high accuracy and their change in dimension during heat treatment correctly predicted in order to facilitate the transfer to their associated radial plates. These processes require novel and sophisticated tooling to be constructed on a large scale. The contract for the manufacture of 10 ITER TF Coil Winding pack was awarded in July 2010 by F4E to a consortium of three main partners-Iberdrola IC, ASG Superconductors and Elytt Energy and in this paper we present the progress made to date. Particular reference is made to the design and procurement of major items of tooling, including the winding line, heat treatment furnace and transfer tool, and the steps taken to minimize risk by design are described.