ITER In-Vessel Coils Research Articles

Low-Resistance Joint for the ITER In-Vessel Coils

Low-Resistance Joint for the ITER In-Vessel Coils

Research and development of copper joint for ITER In-Vessel Coils

The ITER In-Vessel Coils (IVCs) are crucial components of the Tokamak fusion reactor. They are located within the vacuum vessel (VV) behind the blanket shield modules and are responsible for compensating for fast perturbations of the plasma. There are a total of 176 joints used to connect the IVCs, feeders and feedthrough. The joint structure consists of a central copper conductor, a mineral (MgO) insulation layer, and an outer stainless-steel jacket. Given the inaccessibility of the IVCs once the blanket modules are installed, the highest level of quality is required for the joints. One key item is the welding of the copper conductor which has to be done inside the VV. To address the high thermal conductivity of copper conductor and the challenging constraints working inside the VV, a preheating method by the arc of the welding head has been developed. Macro- and micro-structure examination were performed on the welding cross sections, and tensile tests were carried out to check the strength of the copper joint, which demonstrated that arc preheating does not have a significant impact on the heat-affected zone. After more than 40 welding attempts and several design updates, the copper joint has been successfully developed and can be repeatedly and successfully welded.

Compaction technology development for ITER In-vessel coil joints

Two types of ITER In-vessel coils (IVCs) are installed inside the vacuum vessel inner wall, behind blanket shield modules (BSMs), and near the plasma, namely: edge localized mode (ELM) and vertical stabilization (VS) coils. Overall, 27 ELM coils are distributed around the vacuum vessel inner wall, while one VS coil each is mounted above and below the plasma. Moreover, 176 IVC joints are used for joining the IVC coils, feeders, and feedthroughs, while 144 and 32 joints are used for joining the 27 ELM and two VS coils, respectively.The joints, which constitute a stainless steel (SS) sleeve, MgO insulation, and copper tube, show comparable performance to that of the conductor and can thus withstand severe conditions. Furthermore, the minimum available space for joint manufacturing is limited to 60 mm, which is a major obstacle. In joint manufacturing, two adjacent copper conductors are first welded via tungsten inert gas (TIG) welding, then the MgO insulation and sleeve will be applied. To maintain the insulation performance, the MgO insulation and SS sleeve should be compacted. Since compaction is one of the most important processes for joint manufacturing, this paper elucidates the development of compaction technology for IVC joints.

Final Design of ITER In-Vessel Coils and Manufacturing of In-Vessel Coil Conductor

Following a decision made at the ITER Council in November 2013, two types of in-vessel coils (IVCs), namely, edge-localized mode (ELM) coils to mitigate ELMs and vertical stability (VS) coils to provide vertical stabilization of the plasma, have been incorporated in the ITER baseline design. The in-vessel environment is severe, characterized by large transient electromagnetic fields, high radiation flux, and high temperature. To withstand this environment and provide the required functionality, a “mineral insulated conductor” (MIC) technology has been selected for the IVC conductor. It consists of an axially water-cooled copper conductor surrounded by magnesium oxide insulation and a stainless steel jacket. A major advantage of the coil design is the choice of the same conductor material and dimensions for both VS and ELM coils, long conductor length which eliminates the need for any internal joints, and Cu welding for the joints between coils and feeders. In situ winding of the VS coils is asking for the development of a creative solution for the unspooling, straightening, precise winding tools, bending, forming, and metrology processes in a tight and congested environment. Mock-ups for design verification and manufacturing feasibility have been produced, in particular, for the bracket manufacture and to perform thermal and mechanical fatigue testing on an ELM control coil winding pack assembly. Installation trials of a half-size ELM control coil have been performed to verify the feasibility of the assembly procedure. This article will give an overview of the IVC design status and the progress of ITER IVC conductor manufacturing.

Feasibility Study of ITER In-Vessel Coils Bracket Manufacture and Integration

Feasibility study of ITER In-vessel coils bracket manufacture and integration had been developed in Institute of Plasma Physics, Chinese Academy of Sciences. The ITER In-Vessel Coil system is comprised of Edge-Localized Mode (ELM) and Vertical Stabilization (VS) coils. The ELM coils are used to mitigate the Edge Localized Modes and the VS coils are used to provide Vertical Stabilization of the plasma. Designed bracket for IVC coils is a kind of building block type three or four stacked components with arcuate groove matching with round conductor. This paper describes structure design, manufacture and integration process of the ELM and VS bracket. R&D of bracket weld and assembly sequence optimization are carried out to determine the welding and assembly process. At last, three brackets are integrated in ASIPP.

Fatigue behavior testing and evaluation of ITER In-vessel mock-up coil under combined thermal and electromagnetic loads

ITER In-vessel coils (IVCs) are the components to be installed in the vacuum vessel for plasma positions compensation controlling. Every coil will be wound continuously and clamped through the welded Inconel 625 brackets. The coils are planned to be bolted to the rails which are welded to the vacuum vessel wall behind the blanket shield modules. The operation condition is severe for the IVC coils, combined with high radiation, high temperature, as well as the high thermal and electromagnetic loads. To make sure the safe operation, tests have been done on the mock-up coil to check its fatigue properties under the combined thermal and mechanical loads before the finalization of the design. The integrity of the mock-up coil has been evaluated after the fatigue cycling tests. In this paper, the details are presented on the test procedures and the measurement results are summarized.

The ITER In-Vessel Coils – design finalization and challenges

ITER In-Vessel Coils (IVCs), resistive magnets to be installed in close proximity to ITER plasma to compensate fast perturbations of the plasma itself, have undergone a comprehensive revision of their requirements and operational loads, leading to design modifications and R&D activities. An update of the plasma operating scenarios has been done and the maximum currents during transient plasma events have been assessed considering actual operating currents and the surrounding vacuum vessel support structure leading to more representative load cases. The main IVC component modifications are the conductor material and the winding pack support structure. Phase 1 of the conductor procurement involving two suppliers has been completed and the supplier selection for the main production is ongoing. Additional modifications include the joints, where Cu brazing has been replaced by welding, and the conductors are not brazed to the winding pack bracket but clamped. Bracket mockups for the coils have been completed identifying welding parameters and corresponding non-destructive examination (NDE), while different designs of electrical insulating breaks (IB) using Alumina have been tested against pressures up to 80 bars on top of the electrical characterization. A summary of the key challenges experienced towards design finalization is presented.

Research on Nondestructive Examination of Bracket Welds of ITER In-Vessel Coils (IVC)

The ITER in-vessel coils are comprised of edge-localized mode (ELM) and vertical stabilization (VS) coils. There are 27 ELM coils and 2 VS coils. All the ELM and VS coils are supported by the clamped brackets bolted to the rails which are welded to the vacuum vessel wall. The in-vessel environment is severe, characterized by large transient electromagnetic fields, high radiation flux, and high temperature. Therefore, an appropriate nondestructive examination approach should be established and qualified. The difficulty in the development of the bracket weld nondestructive examination is the complex structure which brings space limit and various reflect echoes. Phased array ultrasonic test (PAUT) was studied and developed for nondestructive examination. In order to obtain the appropriate test parameters, CIVA simulation software was utilized to visualize the acoustic field distribution and coverage. The sensitivity of the PAUT method was also demonstrated by using machined defect provided by ITER Organization. Experiment results shows that all of reference defects can be detected with peak amplitude higher than 80% of FSH for both first leg and second leg.

Progress on the design development and prototype manufacturing of the ITER In-vessel coils

Abstracrt ITER is incorporating two types of In-Vessel Coils (IVCs): ELM Coils to mitigate Edge Localized Modes and VS Coils to provide a reliable Vertical Stabilization of the plasma. Strong coupling with the plasma is required in order that the ELM and VS Coils can meet their performance requirements. Accordingly, the IVCs are mounted on the Vacuum Vessel (VV) inner wall, in close proximity to the plasma, just behind the Blanket Shield Modules (BSM). Due to high radiation environment, mineral insulated copper conductors enclosed in a stainless steel jacket have been selected. The reference design and prototype work provided a good basis for the development of radiation resistant conductor capable of operating within the harsh conditions in ITER vacuum chamber. However, this effort identified shortcomings in achieving satisfactory manufacturing solution, and most significantly, difficulties in brazing the brackets onto the ELM coil conductor. Since this process has not proven successful, alternative designs are under development and prototyping. Prototype manufacturing on the alternative designs has been completed at ICAS, Italy and ASIPP, China. The aim was to eliminate the need for internal coil joints, to prove the principle of longer conductor length manufacturing, and to perform bending and welding trials on two different conductor cross-sections: circular and square. The procurement of the IVCs and their conductors will be done via direct call for tender from the ITER Organization. This paper will give an overview of the alternative design and prototype manufacturing of the ITER In-Vessel coils.

Overview of the EAST in-vessel components upgrade

In-vessel components of the EAST superconducting tokamak upgraded from full carbon plasma facing material (PFM) to carbon PFM for upper and lower divertor, and molybdenum PFM for other surface in 2011. Carbon tiles were mechanical connected to CuCrZr heat sink can handle heat flux ∼3MW/m2. EAST was planned to update plasma heating power to 36MW. After that heat flux to divertor will be up to 10MW/m2 for steady state operation and 15MW/m2 for transient. Upgrading divertor accommodate high performance plasma operation requirement is necessary. Tungsten PFM with ITER-like monoblock and flat tungsten technology was developed for EAST upper divertor to handle the high heat flux. To meet tungsten divertor pumping requirement an in-vessel cryo-pump was designed to install in upper divertor area.Type-I edge localized mode (ELM) was observed during EAST plasma operation in 2012. Resonant Magnetic Perturbation (RMP) coils with ITER in vessel coils like insulation technology were developed for the ELM mitigation. Vertical Stability (VS) control coils are also upgrade to ITER-like insulation technology, and coils locations were optimized to obtain more effective instability control.

Manufacture of mineral-insulated conductor for ITER prototype ELM and VS coil

An ITER Organization (IO) Task Agreement (TA) “Final Design and Prototyping of the ITER In-Vessel Coils (IVC) and Feeders” is almost finished by Institute of Plasma Physics, Chinese Academy of Sciences (ASIPP). ITER IVCs consist of edge-localized mode (ELM) and vertical stabilization (VS) coils. One prototype Mid-ELM coil complete with 19 brackets brazed with the conductors and one prototype 120° section of upper VS coil with structural components brazed to the conductors have been fabricated. Compaction method is developed successfully for the mineral-insulated conductor (MIC) manufacture. Approximate 110m Inconel 625 jacket MICs for Mid-ELM prototype coil and 80m stainless steel 316L jacket MICs for VS prototype coil were manufactured. Most of the copper tubes used for the MICs fabrication failed the ultrasonic testing (UT), but the jacket tubes have good passing rate. Manufacture processes and inspection for the MICs are presented in this paper.

R&D Activities on ITER In-Vessel Coil SSMI Conductor Fabrication

A Task Agreement (TA) “Final Design and Prototyping of the ITER In-Vessel Coils (IVCs) and Feeders” was signed and in implementation between ITER Organization and China Domestic Agency (CNDA) and Institute of Plasma Physics, Chinese Academy of Sciences (ASIPP) to advance the design of the ITER IVCs toward final design review readiness including manufacture of prototype ELM and VS coils. Based on many fruitful research results, Princeton Plasma Physics Laboratory (PPPL) is also involved into this TA and in charge of most analysis works, specifications, and electrical breakdown tests of the mineral insulated conductor during irradiation. ITER IVCs consist of Edge-Localized Mode (ELM) and Vertical Stabilization (VS) coils. Structure of Stainless Steel Jacketed Mineral Insulated Conductor (SSMIC) using Magnesium Oxide (MgO) as insulation is being developed for the IVCs manufacture. Different from the industrial products, to ensure the high purity MgO and reach as high as possible insulation performance, ASIPP has developed the compaction method for the scaled-up SSMI Conductor fabrication. After some R&D processes, final dimension ELM and VS SSMI conductor are fabricated. R&D works for SSMIC manufacture are presented in this paper.

Manufacture of EAST VS In-Vessel Coil

In the ongoing latest update round of EAST (Experimental Advanced Superconducting Tokamak), two sets of two single-turn Vertical Stabilization (VS) coils were manufactured and installed symmetrically above and below the mid-plane in the vacuum vessel of EAST. The Stainless Steel Mineral Insulated Conductor (SSMIC) developed for ITER In-Vessel Coils (IVCs) in Institute of Plasma Physics, Chinese Academy of Science (ASIPP) was used for the EAST VS coils manufacture. Each turn poloidal field VS coil includes three internal joints in the vacuum vessel. The middle joint connects two pieces of conductor which together form an R2.3m arc segment inside the vacuum vessel. The other two joints connect the arc segment with the two feeders near the port along the toroidal direction to bear lower electromagnetic loads during operation. Main processes and tests include material performances checking, conductor fabrication, joint connection and testing, coil forming, insulation performances measurement were described herein.

Investigation and analysis on ITER in-vessel coils’ raw-materials

The ITER in-vessel coils (IVCs) consist of 27 coils edge localized modes (ELM) and 2 coils vertical stabilization (VS) which are all mounted on the vacuum vessel wall behind the shield modules. The IVCs design and manufacturing work is being conducted in between Institute of Plasma Physics Chinese Academy of Sciences (ASIPP) and Princeton Plasma Physics Laboratory (PPPL). Because the position of ELM and VS coils is close and face to the plasma, the IVCs must undergo a severe environment, such as the high dose of radiation and high operation temperature, thus the conventional electrical insulation materials cannot be used. And the technology of “Stainless Steel Jacketed Mineral Insulated Conductor” (SSMIC) is deemed as the best choice to provide the necessary radiation resistance and compatibility strength in ITER's vacuum vessel. While mineral insulated conductor technology is not new, and is similar to the mineral insulated cable used in industrial. Some difficulties still need to be solved, such as searching for the proper raw-materials to make sure that the conductor have the properties of high current carrying capability, the necessary radiation resistance, the proper strength, at the same time, it must be come true in manufacture technology. This paper described the analysis of the materials for VS and ELM coil conductor.

Update on Design of the ITER In-Vessel Coils

The ITER project baseline now includes two sets of in-vessel coils, one to mitigate the effects of Edge Localized Modes (ELMs) and another to provide vertical stabilization (VS). The in-vessel location presents special challenges in terms of nuclear radiation and temperature, and requires the use of mineral-insulated conductors. An update to the preliminary design based on this conductor technology is presented for both coil designs. Results from an on-going R&D program consisting of conductor development, welding and brazing process development, electrical testing and mechanical testing in order to demonstrate manufacturability of this style of conductor are presented. Plans for two prototype coils, one of each type, are presented.

Design of the ITER In-Vessel Coils

The ITER project is considering the inclusion of two sets of in-vessel coils, one to mitigate the effect of Edge Localized Modes (ELMs) and another to provide vertical stabilization (VS). The in-vessel location (behind the blanket shield modules, mounted to the vacuum vessel inner wall) presents special challenges in terms of nuclear radiation (˜3000 MGy) and temperature (100 °C vessel during operations, 200 °C during bakeout). Mineral insulated conductors are well suited to this environment but are not commercially available in the large cross section required. An R&D program is underway to demonstrate the production of mineral insulated (MgO or Spinel) hollow copper conductor with stainless steel jacketing needed for these coils. A preliminary design based on this conductor technology has been developed and is presented herein.

Three-dimensional neutronic analysis of the ITER in-vessel coils

A complete neutronic analysis has been performed for the design of the in-vessel coil systems using the MCNP5 Monte Carlo Code in a full 3-D geometry. A detailed geometry of ELM and VS coils based on the latest design specifications has been integrated into the latest version of 40° sector of ITER MCNP model. Nuclear heating and helium production in the coils, absorbed dose in the insulator, dpa and transmutation of copper-alloy and neutron fluxes have been calculated. Neutron spectra have been used as input for an activation analysis performed with FISPACT inventory code for safety analysis and waste classification. The impact of the gaps between blanket modules and of the manifolds on the nuclear parameters has been evaluated as well as the effect on vacuum vessel reweldability. Different options for the conductor and the insulator have been examined.

Design of the ITER In-Vessel Coils

Design of the ITER In-Vessel Coils

04/01155 Characteristics of oxygen-blown gasification for combustible waste in a fixed-bed gasifier: Na, J. I. et al. Applied Energy, 2003, 75, (3–4), 275–285

In the ongoing latest update round of EAST (Experimental Advanced Superconducting Tokamak), two sets of two single-turn Vertical Stabilization (VS) coils were manufactured and installed symmetrically above and below the mid-plane in the vacuum vessel of EAST. The Stainless Steel Mineral Insulated Conductor (SSMIC) developed for ITER In-Vessel Coils (IVCs) in Institute of Plasma Physics, Chinese Academy of Science (ASIPP) was used for the EAST VS coils manufacture. Each turn poloidal field VS coil includes three internal joints in the vacuum vessel. The middle joint connects two pieces of conductor which together form an R2.3 m arc segment inside the vacuum vessel. The other two joints connect the arc segment with the two feeders near the port along the toroidal direction to bear lower electromagnetic loads during operation. Main processes and tests include material performances checking, conductor fabrication, joint connection and testing, coil forming, insulation performances measurement were described herein.

Felony probation: Problems and prospects : by Dean J. Champion Praeger Publishers (One Madison Avenue, New York, New York 10010), 1988, 192 pp., hardcover—$39.95

In the ongoing latest update round of EAST (Experimental Advanced Superconducting Tokamak), two sets of two single-turn Vertical Stabilization (VS) coils were manufactured and installed symmetrically above and below the mid-plane in the vacuum vessel of EAST. The Stainless Steel Mineral Insulated Conductor (SSMIC) developed for ITER In-Vessel Coils (IVCs) in Institute of Plasma Physics, Chinese Academy of Science (ASIPP) was used for the EAST VS coils manufacture. Each turn poloidal field VS coil includes three internal joints in the vacuum vessel. The middle joint connects two pieces of conductor which together form an R2.3 m arc segment inside the vacuum vessel. The other two joints connect the arc segment with the two feeders near the port along the toroidal direction to bear lower electromagnetic loads during operation. Main processes and tests include material performances checking, conductor fabrication, joint connection and testing, coil forming, insulation performances measurement were described herein.