1 FIP/1-4Rb Research, Development and Production of ITER Toroidal - PDF document

1 FIP/1-4Rb Research, Development and Production of ITER Toroidal Field Conductors and Poloidal Field Cables in Russia V.S. Vysotsky, K.A. Shutov, A.V. Taran, I.F. Chensky, L. V. Potanina, D.S. Kaverin, and G.G. Svalov Russian Scientific R&D Cable Institute, 111024, Moscow, Russia E-mail contact of V.S. Vysotsky: vysotsky@ieee.org Abstract . Russian Scientific Research and Development Cable Institute (known by Russian abbreviation as VNIIKP) have been participating in ITER project since 1993 both at the early stage of Research and Development (R&D) and at the following stage of Engineering Design Activity (EDA). Tests of several short samples at Sultan test facility were crowned by successful testing of Toroidal Field and Poloidal Field insert coils performed in Japan in 2001 and 2008 correspondingly. Now VNIIKP is actively implementing the final production and delivery stage. After completion in 2009 of the full technological complex to produce PF cables for both the Russian Federation and European parts and TF conductors for RF part VNIIKP passed all qualification and certification procedure demanded by Procurement Arrangements. Right now the production and delivery of PF cables and TF conductors are in the full steam and going to be concluded in 2015. We are presenting the development of technology; results of R&D accompanied developments and the results of production and delivery of the cables and conductors for magnet system of ITER. 1. Introduction Since 1993 Russian Scientific Research and Development Cable Institute (VNIIKP) has been participating in ITER project. During R&D at EDA stage we developed several types of multi- strand cables and Cable-In-Conduit Conductors (CICC) and tested full size Toroidal Field (TF) and Poloidal Field (PF) insert coils. [1]-[6]. The experience gained during R&D stages permitted eventually to develop the industrial technology complex for regular manufacturing of the TF conductors and PF cables. Some details about technology complex were presented earlier in [7]-[9]. The general technology route for PF cables and TF conductors is as follows: According to the RF Domestic Agency (DA) internal cooperation, the bare NbTi and Nb 3 Sn strands for cables and conductors are produced by Chepetsk Mechanical Plant (ChMP) in Glasov city and then delivered to VNIIKP. Before cabling the NbTi strands have to be coated by nickel and Nb 3 Sn strands have to be coated by chromium. Copper wires used for fabrication of PF and TF dummy cables and in TF cables have to be coated by chromium as well. Then basic wires are moved to the cabling workshop for the five stage cabling. After cabling the PF cables are delivered to International Consortium of Superconductivity (ICAS) facility in Chivasso city in Italy for jacketing to a rectangular jacket. ICAS is the sub- contractor for Fusion for Energy which is European Domestic Agency for ITER. TF cables are delivered to VNIIKP jacketing line located at the Institute for High Energy Physics in Protvino city [7], [9]. When TF conductors are produced and wound in a transport solenoid with 4 m in diameter, they are delivered to NRC “Kurchatov Institute” for final leak test [9]. After leak test the TF conductors are delivered to ASG Company in La Spezia, Italy for production of TF coils. Before we came over to the production stage the heavy qualification procedures have been passed. All technology procedures and processes were verified by independent experts,

2 FIP/1-4Rb described and approved by International organization (IO) of ITER as it is demanded by our Procurement arrangements (PA) [10]. The staff working in sensitive Quality Assurance areas like welding, X-ray check, vacuum check, etc. passed examinations and certifications from independent experts nominated by IO as well. Also 5 dummy PF cables and 2 TF conductors were produced and delivered as part of qualification procedures. Only after all qualifications and certifications were passed, we were allowed to start regular production and delivery of both PF cables and TF conductors in 2011. Besides development of new technologies and production of superconducting cables and conductors we are performing several R&D studies. Particularly, study of Residual Resistance Ratio (RRR) changes during production processes [11], [12], untwisting of cables during their insertion to a jacket [13], [14], study of microstructure of Nb 3 Sn strands after their test at SULTAN test facility [15], etc. In this review we present the current data on the cables and conductors production state. Some results from our R&D are presented as well. 2. Strands coating In accordance with PAs before cabling the NbTi strands have to be coated by nickel and Nb 3 Sn strands have to be coated by chromium. Copper wires used for fabrication of PF and TF dummy cables and in TF cables have to be coated as well. Before this, strands and wires should be cleaned to prepare their surface for high quality coating. The two stage coating technology is described in details in [7], [8]. Two electro-chemical cleaning line has been installed to increase the cleaning efficiency. Entire production capacity permits now to clean up to 45 km of Cu wires and superconducting strands per day. One line for Ni coating (Fig.1 a) and three lines for Cr coating (Fig.1 b) were developed and installed. The linear capacity of Ni-coating line is ~100 m/min; the capacity of a single Cr-coating line is ~30-40 m/min. The tightly adjusted chemical coating processes developed in VNIIKP together with fully qualified verification procedures ensure the required quality of plated strands, i.e. clean surface free of any defects before plating, thickness of layer within 1.5-2.0 µm, good cohesion of plating without any flaking, designed diameter tolerance. Entire technological route has initial, intermediate and final check points for verification and confirmation the quality of strands demanded. The quality of plated strands is shown in Fig. 1. Up to October 2014 about 33 600 km of Ni-coated NbTi strands and about 27 400 km of Cr – coated Nb3Sn strands have been produced. a b Fig.1. a - Ni-plating facility and nickeled NbTi strand; b - Cr-plating facility and chromed Nb3Sn strand We have to note that our coating processes are based on a soft technology, consuming not more than 100 liters of distilled water for a fourteen hours working day, and have no leakages or discharge to a main drain.

3 FIP/1-4Rb 3. Cabling The general cabling route of TF ITER cable is illustrated in Fig.2 as an example. One can see that cables have inner spiral, five stages twisting and stainless steel tape wrapping at the fourth and fifth stages. To complete all these process the spiral production and the cabling workshop have been arranged in VNIIKP. 3.1 Spiral production Both PF and TF cables contain central cooling spirals. The special spiral making machine has been developed to produce long length spirals with diameters from 8 to 14 mm [9]. The photos of the spirals produced are shown in Fig.2. By the October 2014 we have produced in total more than ~45 km of spirals for our own needs, and ~15 km of TF spiral were delivered for USA DA and ICAS teams. Fig.2. General view of the TF five-stage cabling process. Fig.3 Spirals for ITER: PF cable spiral PF cables have similar five stage cabling process but (up) and TF cable spiral (below) without copper strands. 3.2 Cabling machines Our cabling workshop is equipped by two high speed tubular machines for the first and the second stages twisting. Two planetary machines with wrappers for the third and the fourth stages twisting can produce up to 10 km of third stage sub-cables a day and up to 1.5 km of fourth stage sub-cables a day. The final twisting is being performed at the large planetary machine with wrapper that is able to perform final twisting of ~800 m cable during 3-5 days. This machine is equipped with three special multi – rollers compacting calibers to provide exact diameter and the required density of a cable pack before jacketing. The photos of our cabling machines are shown in Fig. 4. 3.3 PF Cabling Status In accordance with agreement between European Union (EU) and Russian Federation, RF produces all NbTi cables for PF1 and PF6 poloidal field coils, while EU performs jacketing of all cables for the coils mentioned. In total VNIIKP has to produce 41 unit lengths of PF cables (including 5 dummy cables) with lengths 414 m and 734 m for both PF6 and PF1 poloidal coils. Right now the production of PF cables in VNIIKP is going in a full steam. Our cabling process has successfully passed all qualification procedures. In Fig. 5 the photo of PF cable sample consisting of 6 sub-cables is shown before final wrapping by stainless steel tape and in Fig.6 PF cables produced and ready for delivery are shown.