Design and manufacture of the Poloidal Field Conductor Insert coil

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Abstract-In this paper we report the main test results obtained on the Poloidal Field Conductor Insert coil (PFI) for the International Thermonuclear Experimental Reactor (ITER), built jointly by the EU and RF ITER parties, recently installed and tested in the CS Model Coil facility, at JAEA-Naka. During the test we (a) verified the DC and AC operating margin of the NbTi Cable-in-Conduit Conductor in conditions representative of the operation of the ITER PF coils, (b) measured the intermediate conductor joint resistance, margin and loss, and (c) measured the AC loss of the conductor and its changes once subjected to a significant number of Lorentz force cycles. We compare the results obtained to expectations from strand and cable characterization, which were studied extensively earlier. We finally discuss the implications for the ITER PF system. Index Terms-Cable-in-conduit conductors, fusion reactors, Nb-Ti superconducting material, superconducting magnets. I. BACKGROUND ON ITER PF CONDUCTORST HE ITER Poloidal Field (PF) conductors have undergone a significant evolution in the past years. In the original ITER design (2001) the Cable-in-Conduit Conductors (CICCs) were optimized to match the current/field levels in each of the six PF coils [1]. Following recent design reviews, a number of modifications have been introduced [2], leading to the conductor designs detailed in Table I, for the envelope of operating conditions in the PF Coils reported in Table II. The main change with respect to the original design is a reduction in the Cu:nonCu ratio of the low field conductors (PF2 to PF5), implying that the Stekly condition of cryogenic stability [3] is no longer respected. Experiments on subsize conductors [4] have suggested that in the planned regime of operation, and for the expected perturbation spectrum, full cryostability (i.e. a copper fraction corresponding to the Stekly limit) is excessive. In fact, for the conditions considered, it is more convenient to design the conductor for larger temperature margin, increasing the fraction of Nb-Ti, while maintaining the copper fraction to the strict minimum demanded for protection. To achieve the operating requirements of Table II, two main conditions must be met. Firstly, the cable performance must be close to the sum of the projected performance of the individual strands, without the occurrence of the premature quenches often seen in large size Nb-Ti conductors and attributed to current non-uniformity [4], [5] (see also later discussion). In practice, we quantify this first condition using the temperature margin above the operating temperature. The design value of the temperature margin is 1.5 K, with a maximum uncertainty of 0.5 K, which results in a minimum acceptable margin of 1 K.Secondly, all AC loss sources in the cable must be controlled, so to limit the temperature increase due to the heating due to the pulsed operation. In particular, the product of the cable demagnetization factor and coupling time constant, , proportional to coupling loss, must be smalle...

Section: The Pf Conductor Insertmentioning

confidence: 99%

Test Results From the PF Conductor Insert Coil and Implications for the ITER PF System

Bessette

Bottura

Devred

et al. 2009

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“…Loop currents in these cases satisfy the equations: (2) The resistances and e.m.f. induced in these cells were calculated in the similar way as for the above large loop model.…”

Section: Inductancesmentioning

confidence: 99%

“…T HE lap-type joints of cable-in-conduit conductors (CICC) have been used in the ITER Toroidal field model coil [1] and the Poloidal field (PF) insert coil [2]. They were recognized as the prospective type of the joints of high current NbTi conductors of the PF coils of the ITER magnet [3].…”

Section: Introductionmentioning

confidence: 99%

Currents Induced in the Lap-Type Joints of Superconducting Cable-in-Conduit Conductors Exposed to the Time-Varying Magnetic Field

Astrov

Егоров

Rodin

et al. 2012

Two models to evaluate the currents induced in the lap-type electrical joints of multistage cable-in-conduit superconductors are developed. The currents are originated from the action of time-varying magnetic field penetrating into the gap between jointed cables. In the low-resistance joints high loop currents can be induced. Reduction of these currents is originated from the short time of fast ramping of the magnetic field which the joints are exposed to. The paper contains description of the models and analytical results obtained.

“…The main objective of this coil is the characterization of long lengths (several tens of meters) of full-size cable-in-conduit conductor (CICC) and joints under operational conditions (current & field) similar to those experienced by the ITER Poloidal Field coils [5].…”

Section: Introductionmentioning

confidence: 99%

“…The cables have been jacketed inside stainless steel square tubes by Ansaldo Superconduttori[5] and shipped to Tesla in mid-2003.…”

mentioning

confidence: 99%

Preparation of the ITER Poloidal Field Conductor Insert (PFCI) Test

Zanino

Егоров²,

Kim³

et al. 2005

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The Poloidal Field Conductor Insert (PFCI) of the International Thermonuclear Experimental Reactor (ITER) has been designed in the EU and is being manufactured at Tesla Engineering, UK, in the frame of a Task Agreement with the ITER International Team. Completion of the PFCI is expected at the beginning of 2005. Then, the coil shall be shipped to JAERI Naka, Japan, and inserted into the bore of the ITER Central Solenoid Model Coil, where it should be tested in 2005 to 2006. The PFCI consists of a NbTi dual-channel conductor, almost identical to the ITER PF1 and PF6 design, 45 m long, with a 50 mm thick square stainless steel jacket, wound in a single-layer solenoid. It should carry up to 50 kA in a field of 6 T, and it will be cooled by supercritical He at 4.5 K and 0.6MPa. An intermediate joint, representative of the ITER PF joints and located at relatively high field, will be an important new item in the test configuration with respect to the previous ITER Insert Coils. The PFCI will be fully instrumented with inductive and resistive heaters, as well as with voltage taps, Hall probes, pick-up coils, temperature sensors, pressure gauges, strain and displacement sensors. The test program will be aimed at DC and pulsed performance assessment of conductor and intermediate joint, AC loss measurement, stability and quench propagation, thermal-hydraulic characterization. Here we give an overview of the preparatory work toward the test, including a review of the coil manufacturing and of the available instrumentation, a discussion of the most likely test program items, and a presentation of the supporting modeling and characterization work performed so far.