MHI completed the world's first TF coil for ITER in
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
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.
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
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.
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