Qualification Phase of Key Technologies for ITER Correction Coils

The ITER Magnet system [1] consists of four main coils sub-systems: 18 Toroidal Field Coils (TF-coil), a Central Solenoid (CS), 6 Poloidal Field Coils (PF-coil) and 18 Correction Coils (EFCC). The main contract of the EFCCs supply is awarded to the Institute of Plasma Physics Chinese Academy of Sciences (ASIPP) by the Chinese Domestic Agency (CNDA). According to the pre-qualification program, ASIPP is implementing the procurement phase to qualify and validate key technologies and manufacturing methods. The Correction coils qualification activities are conducted within the framework of the procurement arrangement set up between the ITER Organization and CNDA. The paper describes the CC development including first results of the coils winding qualification trials and, qualification of a S-Glass fiber-polyimide based insulation system The CC casing assembly process and the first results of the welding trials are reported. The weld qualification, according to ASTM for 316LN austenitic steel is reported in terms of fracture toughness, fatigue crack growth, and tensile property at 4 K. The Vacuum Pressure Impregnation of CC short mock-up, with low viscosity bisphenol-F (DGEBF) epoxy resin, aims to optimization of the curing and insulation mechanical properties.

I. Introduction

The system of 18 ITER Error Field superconducting Correction Coils (EFCC) [2] installed outside the tokamak Vacuum Vessel is now undergoing its procurement phase. The fabrication contract for those EFCC coils is placed by the CNDA with the main supplier, the Institute ASIPP This procurement includes a development scheme in order to guarantee manufacturability, quality and performances targets by the end of 2012. This paper describes the qualification trial tests and procedures that every EFCC items shall follow, according to standards to proceed with the manufacturing procurement of tooling equipment and coils. Fig. 1.

Cutaway view of the internal structure of Bottom EFCC winding pack.

Table I Main ITER Correction Coils Features

Parameter	Description
Dimensions	BCC/TCC: 7 m x 2.7 m; SCC: 8 m x 7 m
Nominal current	10 kA at 4K
Coil case material	20 mm thick 316LN stainless steel
Cable in conduit Conductor	NbTi Cable in conduit Conductor, with 300 NbTi strands, strand diameter 0.73 mm, 2.2 mm thick SS 316L jacket, 19.2 mm x 19.2 mm, 35% void fraction
Turn insulation	1.2 mm thick multi-layer interleaved Polyimide/S-glass glass fiber (2 layers)
Ground insulation	4 mm thick interleaved Polyimide/S-glass fiber (4 layers)
Winding pack cross section	32 turns BCC/TCC : 196 × 103 mm2, 20 turns SCC: 91×116 mm2