MHI Completes Four TF Coils for ITER

May 24, 2021 12:23 JST

Source: Mitsubishi Heavy Industries, Ltd.

- Four of the total five TF coils ordered (excluding the spare) are being shipped to the project site.
- MHI has demonstrated high technical capabilities with the TF coil structure and winding, contributing to the development of fusion technology.

TOKYO, May 24, 2021 - (JCN Newswire) - Mitsubishi Heavy Industries, Ltd. (MHI) has completed manufacture of four toroidal field (TF) coils (of a total of five, including one spare) ordered by the National Institutes for Quantum and Radiological Science and Technology (QST) for the ITER, an experimental fusion reactor, currently under construction in Saint-Paul-les-Durance in southern France. The completed TF coils will be shipped to southern France from Kobe, and installed on site by the ITER Organization, with operations to commence in 2025.

Completed fourth unit

MHI completed the world's first TF coil for ITER in January 2020, holding a ceremony at its Futami Plant to mark the achievement. This first coil, and the second unit completed in March 2020, are currently in the process of being installed in the experimental reactor in southern France. The third coil, completed in November 2020, has arrived at the site and testing has been completed.

To produce a nuclear fusion reaction in the reactor, the fuel of deuterium and tritium needs to be held in a magnetic field in a high-temperature, high-density (plasma) state. Accordingly, the TF coils that are the core components of ITER require high precision manufacturing to secure the plasma with a high degree of accuracy, and sufficient thickness to withstand the strong magnetic field of tens of thousands of tons. In addition to handling the final assembly process for five of the total 19 TF coils in ITER, MHI manufactured the structure and winding used in the TF coils, achieving a level of precision within 0.01% for these massive superconducting coils, which are 16.5 meters high and 9 meters wide, with a gross weight of 300 tonnes.
In addition to the completion of the four TF coils for ITER, MHI is also working on manufacturing other core components, including the divertor(1)1 and equatorial EC launcher(2). By drawing on its accumulated knowledge to provide mass production technologies for components with a high degree of manufacturing difficulty, and actively supporting the ITER project to develop technology that will be vital to the stable development of the world, MHI continues to contribute to enhancing the reliability of fusion technology.

Project Background
The ITER Project is an international megaproject aimed at demonstrating, both scientifically and technologically, the realization of fusion energy(3). Seven parties are participating: Japan, the EU, the U.S., Russia, South Korea, China, and India. Construction of ITER is underway in Saint-Paul-les-Durance, France, with a target operational startup date of 2025. Japan is playing a major role in developing and manufacturing the core components of ITER, including the TF coils. QST, as the ITER Japan domestic agency for the ITER Project designated by Japanese Government, is in charge of procuring these components.

ITER's superconducting TF coils are D-shaped and approximately 16.5m in height, 9m wide, and weigh some 300 tonnes. Eighteen TF coils will encompass the vacuum vessel container and generate a powerful magnetic field (maximum of 12 tesla) to confine high-temperature, high-density plasma within the vessel. The ITER Project requires a total of 19 TF coils (including one spare). Nine are being made in Japan (including the spare) and 10 in Europe. The inboard coil structures for all 19 TF coils will be manufactured at MHI's Futami Plant.

Mitsubishi Electric Corporation is in charge of producing the niobium-tin (Nb3Sn) superconducting winding packs for five TF coils (including the four completed coils), with the outboard coil structures being manufactured in South Korea, and final assembly performed at the Futami Plant.

Significance of This Latest Achievement
A highly precise, strong magnetic field (12 tesla) is required to confine plasma inside ITER, necessitating the development of unprecedentedly large superconducting coils that use niobium-tin conductors. To maintain superconductivity, the coils must be able to function in cryogenic temperatures of minus 269degC, which required the development of special stainless steel structural materials capable of withstanding such low temperatures, along with all requisite manufacturing technology. Not only was there no precedent for coils of this unsurpassed scale, the dimensional tolerances of the windings and coils required a high precision of within 0.01%.

QST commenced R&D for the TF coil manufacturing technology in 2005, and MHI began their manufacture in 2012. Working in collaboration, QST and MHI developed high-precision technology for winding niobium-tin conductors, and also developed durable structural materials made from a special stainless steel capable of withstanding cryogenic temperatures.

Further, to determine the conditions to suppress deformations caused by welding, parameter tests were conducted, and the welds verified using both miniature and full-scale specimens, which formed the basis for the fundamental technologies suited to the material's properties, including advanced welding procedures and machining techniques. Ultimately, MHI was able to meet the stringent requirements demanded for ITER.

Future Schedule
MHI plans to complete manufacture of the remaining TF coil (spare coil) of the total five coils in 2022.

(1) A device to remove impurities in the core plasma, as well as inhibit high heat load and particle loading.
(2) A device to inject high-frequency electromagnetic waves to heat the plasma.
(3) Fusion is the energy source that enables the sun to keep shining. The ultimate goal is achieving fusion on Earth. Fusion reactions fuse light atomic nuclei (deuterium and tritium) in a plasma environment into the heavier element of helium. Fusion reactions emit zero carbon dioxide, and their source of fuel can be extracted from seawater in virtually unlimited quantities (lithium from which tritium is derived, and deuterium). Fusion energy is expected to provide fundamental solutions to many of the world's energy and environmental problems.

About MHI Group

Mitsubishi Heavy Industries (MHI) Group is one of the world's leading industrial groups, spanning energy, logistics & infrastructure, industrial machinery, aerospace and defense. MHI Group combines cutting-edge technology with deep experience to deliver innovative, integrated solutions that help to realize a carbon neutral world, improve the quality of life and ensure a safer world. For more information, please visit www.mhi.com or follow our insights and stories on www.spectra.mhi.com.

Source: Mitsubishi Heavy Industries, Ltd.
Sectors: Construct, Engineering