Search

The ITER magnet procurement is now well underway. The magnet systems consist of 4 superconducting coil sets (toroidal field (TF), poloidal field (PF), central solenoid (CS) and correction coils (CC)) which use both NbTi and Nb3Sn-based conductors. The magnets sit at the core of the ITER machine and are tightly integrated with each other and the main vacuum vessel. The total weight of the system is about 10000 t, of which about 500 t are Nb3Sn strands and 250 t, NbTi. The reaction of the magnetic forces is a delicate balance that requires tight control of tolerances and the use of high-strength, fatigue-resistance steel forgings. Integration and support of the coils and their supplies, while maintaining the necessary tolerances and clearance gaps, have been completed in steps, the last being the inclusion of the feeder systems. Twenty-one procurement agreements have now been signed with 6 of the ITER Domestic Agencies for all of the magnets together with the supporting feeder subsystems. All of them except one (for the CS coils) are so-called Build to Print agreements where the IO provides the detailed design including full three-dimensional CAD models. The production of the first components is underway (about 175 t of Nb3Sn strand was finished by July 2011) and manufacturing prototypes of TF coil components are being completed. The paper will present a design overview and the manufacturing status. [ABSTRACT FROM PUBLISHER]

The International Thermonuclear Experimental Reactor (ITER) has 60 high-temperature superconducting (HTS) current leads (CL) which have a nominal current of 68, 55 and 10 kA (depending on the type of magnet they have to supply) and provide a total current of 2.7 MA to the magnet system. The HTS module is a key part of CLs. This paper describes the simulation of the critical current in a multi-layer tape model as well as the special soldering technique developed for the HTS stack. In order to validate this technique, a 10 kA pre-prototype HTS module was made and tested in a setup that reproduces ITER conditions at ASIPP. The paper also briefly describes the overheating time test setup and the results. [ABSTRACT FROM PUBLISHER]

The superconducting magnet system of ITER has \sim5,000 tons of cold mass as steel structures to support the gravity and electromagnetic forces. These steel structures need to be maintained at \sim4.4 K during magnet operations. The magnet system has three STR (structure) feeders for distribution, monitoring and control of helium to remove heat loads from these large steel structures during cool down and normal operation. One SHe (supercritical helium) circulation pump for flow rate of \sim2.7 kg/s, in a closed loop is used only for cooling of structures, and these 3 STR feeders are part of this loop. Each STR feeder has 3 main components: SCVB (structure cooling valve box), CFT (cryostat feed through) and ICF (in-cryostat feeder). Unlike the coil feeders, STR feeders do not have bus bars, current leads & SBB (“S”-bend box), and present some difference in the design approach. The SCVB is placed outside the enclosure of the nuclear radiation shield and hence contains elements needing maintenance like valves and instruments required for diagnosis and operation of the cooling paths. Each SCVB has to accommodate about 20 valves within a limited available space. Some SHe lines will have running length of about 50 m from SCVB to coil structures, but the layout is such that the use of expansion joints can be avoided. The details of the design approach and analysis results will be presented in this paper. [ABSTRACT FROM PUBLISHER]

The ITER magnet system is to be operated at about 4.5 K. It has 31 feeders for high-current power supply, helium distribution and instrumentation cable routing. The feeders (except the smaller ones which are for instrumentation only) are 25 to 30 m long for about 40 tons. They have 3 main components: coil terminal box-cum-S-bend box (CTB-SBB), Cryostat feedthrough (CFT) and in-cryostat feeder (ICF). The CTB is the feeder component placed farthest from the coil (about 25 m away from the magnet center) and outside the bio-shield (the nuclear radiation restriction wall) so that it can be easily accessible in case the critical elements placed within it need maintenance: high-temperature superconducting current leads (HTSCL), large number of cryogenic control valves and pressure-release valves for quench protection. This paper explains the cryogenic design that considers these factors and main components. [ABSTRACT FROM PUBLISHER]

ITER has a large superconducting magnet system with about 10,000 tons of cold mass to be maintained at about 4.5 K during magnet operation. This cold mass has to be cooled down from \sim300 to 4.5 K simultaneously and uniformly to avoid high thermal stress. More than 5,000 tons of cold mass corresponds to steel structures to support the gravity and electromagnetic forces. A controlled cool down is necessary to avoid high thermal stress in these materials. The variations of hydraulic impedances and cold masses of different magnet components play a major role in making the cool down non-uniform if appropriate control strategies are absent. A detailed analysis has been done to quantify the factors preventing a uniform cool down. The slowest cooling component will dictate the cool down rate of the whole magnet system. The analysis finds the maximum cool down rates possible for different components and controlled flow rate required for different components to have uniform cool down of all components. Based on this, the cool down rates and duration have been found. This paper will discuss details of these analysis results. [ABSTRACT FROM PUBLISHER]

The ITER Magnet System contains 18 Toroidal Field Coils (TFC). These are large D-shaped coils of about 300 t, 17.5-m height and 9-m width. They consist of a Winding Pack (WP) enclosed in a rigid structural steel case, the Toroidal Field Coil Case (TFCC). The WP is a bonded structure of 7 Double Pancakes (DP), each made up of a radial plate (RP) housing the reacted Nb3Sn cable-in-conduit superconductor (CICC), which operate at 4.5 K in supercritical helium. The conductor carries a current of 68 kA in operation to produce a nominal peak field of 11.8 T. The total stored magnetic energy in the 18 TFCs is 41 GJ. While the Japanese and European Domestic Agencies that are in charge of the procurement of the TFCs are progressing with the manufacturing design and the fabrication trials prior to launch the production of the real coils, the ITER Organization (IO) is completing the development and qualification of the most critical items, e.g. cyanate ester and resin blends for the conductor and WP insulation system, the terminal region, the helium inlet, a charged resin system for the filling of the gap between the WP and the TFCC and the general tolerancing especially at the interfaces between the neighboring systems. This paper presents the final design of the TFCs and the results of the developments carried out in the aforementioned areas in the last 2 years. [ABSTRACT FROM PUBLISHER]

The ITER magnet system consists of 4 sub-systems: 3 sets of 6 Correction Coils (CC), a Central Solenoid (CS), 6 Poloidal Field coils (PF) and 18 Toroidal Field Coils (TFC). The Correction Coil system aims to correct particular asymmetries and reduce error magnetic fields responsible for locked modes which can induce plasma disruptions. During the plasma scenario, thermal shield radiation, eddy current losses in structures, conduction from the TFC casing and AC losses in the NbTi superconductor will decrease the temperature margin of the CC conductor. [ABSTRACT FROM PUBLISHER]

ITER magnets are all designed using superconducting conductors with a high current carrying capability. The Poloidal Field (PF) coils are operated in pulsed mode with maximum operating currents of 48 kA for PF 1 and 6, 55 kA for PF 2,3, and 4 and 52 kA for PF 5. The PF system consists of 6 ring coils, PF1 through PF6, that serve to stabilize the position and control the shape of the plasma in the tokamak. The six PF coils are attached to the outside of the Toroidal Field (TF) coil cases through flexible plates or sliding supports allowing radial displacements. The PF coil positions and sizes have been optimized for the plasma requirements consistent with the constraints imposed by allowing access to the vacuum vessel and by considering pumping ducts to the in-vessel components. [ABSTRACT FROM AUTHOR]

The nuclear radiation levels, magnetic fields and general access restrictions in the ITER Tokamak are such that it is undesirable to place remote control helium supply valves close to the coils. The Coil Terminal Boxes (CTB), which are further away from the coils, are therefore designed for easy access and contain as much as possible the components needing maintenance, such as the cryo-valves. The CTBs also house the electrical cold-warm transitions with the HTS current leads and the NbTi feeder busbars. Also most of the feeder instrumentation is located in the CTB. Based on the functional specification by ITER, ASIPP has manufactured and tested a prototype CTB for the ITER magnet system. This test allowed for the verification of the mechanical design of the cryostat and the thermal shield design. Following a discussion of the ITER CTB design, with particular emphasis on the concepts of flow distribution for the large ITER magnet system, considering safety and maintenance, this paper will also present the results of the prototype CTB development. [ABSTRACT FROM AUTHOR]

In this paper we discuss the predictive analysis performed in support of the test program of the International Thermonuclear Experimental Reactor (ITER) Poloidal Field Conductor Insert (PFCI). A subset of the test program items was considered, with particular emphasis on DC performance and AC losses. The results and implications of the comparison of selected predictions from different laboratories will be presented. [ABSTRACT FROM AUTHOR]