Japan Torus-60 | |
---|---|
Device type | Tokamak |
Location | Naka, Ibaraki Prefecture, Japan |
Affiliation | Japan Atomic Energy Agency |
Technical specifications | |
Major radius | 3.4 m (11 ft) |
Minor radius | 1.0 m (3 ft 3 in) |
Plasma volume | 90 m3 |
Magnetic field | 4 T (40,000 G) (toroidal) |
Discharge duration | 65 s |
History | |
Year(s) of operation | 1985–2010 |
Preceded by | JFT-2M |
Succeeded by | JT-60SA |
Related devices | TFTR |
Links | |
Website | www |
Japan Torus-60 Super Advanced | |
---|---|
Device type | Tokamak |
Location | Naka, Ibaraki Prefecture, Japan |
Affiliation | QST + F4E |
Technical specifications | |
Discharge duration | 100 s |
History | |
Date(s) of construction | 2013 - 2020 |
Year(s) of operation | 2023–present |
Preceded by | JT-60U |
Related devices | ITER |
Links | |
Website | www |
JT-60 (short for Japan Torus-60) is a large research tokamak, the flagship of the Japanese National Institute for Quantum Science and Technology's fusion energy directorate. As of 2023 the device is known as JT-60SA and is the largest operational superconducting tokamak in the world, [1] built and operated jointly by the European Union and Japan in Naka, Ibaraki Prefecture. [2] [3] SA stands for super advanced tokamak, including a D-shaped plasma cross-section, superconducting coils, and active feedback control.
As of 2018, [update] JT-60 holds the record for the highest value of the fusion triple product achieved: 1.77×1028 K·s·m−3 = 1.53×1021 keV·s·m−3. [4] [5] To date, JT-60 has the world record for the hottest ion temperature ever achieved (522 million °C); this record defeated the TFTR machine at Princeton in 1996. [6]
JT-60 was first designed in the 1970's during a period of increased interest in nuclear fusion from major world powers. In particular, the US, UK and Japan were motivated by the excellent performance of the Soviet T-3 in 1968 to further advance the field. The Japanese Atomic Energy Research Institute (JAERI), previously dedicated to fission research since 1956, allocated efforts to fusion.
JT-60 began operations on April 8, 1985, [7] and demonstrated performance far below predictions, much like the TFTR and JET that had begun operations shortly prior.
Over the next two decades, JET and JT-60 led the effort to regain the performance originally expected of these machines. JT-60 underwent a major modification during this time, JT-60U (for "upgrade") in March 1991. [8] The change resulted in significant improvements in plasma performance.
The main objective of the JT-60U upgrade was to "investigate energy confinement near the breakeven condition, [a] non-inductive current drive and burning plasma physics with deuterium plasmas." To accomplish this, the poloidal field coils and the vacuum vessel were replaced. Construction began in November 1989 and was completed in March 1991. [9] Operations began in July. [10]
On October 31, 1996, JT-60U successfully achieved extrapolated breakeven with a factor of QDTeq = 1.05 at 2.8 MA. In other words, if the homogenous deuterium fuel was theoretically replaced with a 1:1 mix of deuterium and tritium, the fusion reaction would have created an energy output 1.05 times the energy used to start the reaction. JT-60U was not equipped to utilize tritium, as it would add extensive costs and safety risks.
In February 1997, a modification to the divertor from an open-type shape to a semi-closed W-shape for greater particle and impurity control was started and later completed in May. [11] [12] [13] Experiments simulating the helium exhaust in ITER were promptly performed with the modified divertor, with great success. In 1998, the modification allowed JT-60U to reach an extrapolated fusion energy gain factor of QDTeq = 1.25 at 2.6 MA. [14] [15] [16]
In December 1998, a modification to the vacuum pumping system that began in 1994 was completed. In particular, twelve turbomolecular pumps with oil bearings and four oil sealed rotary vacuum pumps were replaced with magnetically suspended turbomolecular pumps and dry vacuum pumps. The modification reduced the 15-year-old system's consumption of liquid nitrogen by two thirds. [17]
In fiscal year 2003, the plasma discharge duration of JT-60U was successfully extended from 15 s to 65 s. [18]
In 2005, ferritic steel (ferromagnet) tiles were installed in the vacuum vessel to correct the magnetic field structure and hence reduce the loss of fast ions. [19] [20] The JAEA used new parts in the JT-60, having improved its capability to hold the plasma in its powerful toroidal magnetic field.
Sometime in 2007-2008, in order to control plasma pressure at the pedestal region and to evaluate the effect of fuel on the self-organization structure of plasma, a supersonic molecular beam injection (SMBI) system was installed in JT-60U. The system's design was a collaboration between Cadarache, CEA, and JAEA. [21]
JT-60U ended operations on August 29, 2008. [22]
JT-60SA is the successor to JT-60U, operating as a satellite to ITER as described by the Broader Approach Agreement. It is a fully superconducting tokamak with flexible components that can be adjusted to find optimized plasma configurations and address key physics issues. [23] Assembly began in January 2013 and was completed in March 2020. After a major short circuit during integrated commissioning in March 2021 necessitating lengthy repairs, it was declared active on December 1, 2023. The overall cost of its construction is estimated to be around € 560000000, adjusted for inflation. [24]
Weighing roughly 2,600 short tons (2,400 t), [25] JT-60SA's superconducting magnet system includes 18 D-shaped niobium-titanium toroidal field coils, a niobium-tin central solenoid, and 12 equilibrium field coils.
The idea of an advanced tokamak, a tokamak utilizing superconducting coils, traces back to the early 1960's. The idea seemed very promising, but was not without its problems. Around January 1972, engineers at JAERI initiated an effort to further research the idea and try to solve its hurdles. [26] This initiative progressed in parallel with the development of JT-60, [27] and by 1983-84 it was decided that it constituted its own experimental reactor: FER (Fusion Experimental Reactor). [28]
However, the JT-60U upgrade in 1991 demonstrated the significant flexibility of the JT-60 facilities and assembly site, so by January 1993 FER was designated as a modification to JT-60U and renamed JT-60SU (for Super Upgrade). [29]
In January 1996, a paper detailing the superconducting properties of Nb3Al composite wire and its fabrication process was published in the 16th International Cryogenic Engineering/Materials Conference journal. [30] Engineers assessed the potential use of the aluminide in JT-60SU's 18 toroidal coils. [31]
Designs and intentions for the modification varied over the next decade, until February 2007, when the Broader Approach Agreement was signed between Japan and the European Atomic Energy Community. [32] In it, the Satellite Tokamak Program established a clear, defined goal for JT-60SA: act as a small-scale ITER. This way, JT-60SA could give hindsight to engineers assembling and operating the full-scale reactor in the future.
It was planned for JT-60 to be disassembled and then upgraded to JT-60SA by adding niobium-titanium superconducting coils by 2010. [4] [33] It was intended for the JT60SA to be able to run with the same shape plasma as ITER. [33] : 3.1.3 The central solenoid was designed to use niobium-tin (because of the higher (9 T) field). [33] : 3.3.1
Construction of the tokamak officially began on 28 January 2013 with the assembly of the cryostat base, which was shipped from Avilés, Spain over a 75-day long journey. [lower-alpha 1] The event was highly publicized through local and national news, and reporters from 10 media organizations were able to witness it in person. [34]
Assembly of the vacuum vessel began in May 2014. The vacuum vessel was manufactured as ten sectors with varying arcs (20°x1, 30°x2, 40°x7) that had to be installed sequentially. On June 4, 2014 two of ten sectors were installed. In November 2014 seven sectors had been installed. In January 2015 nine sectors had been installed.
Construction was to continue until 2020 with first plasma planned in September 2020. [35] Assembly was completed on March 30, 2020, [36] and in March 2021 it reached its full design toroidal field successfully, with a current of 25.7kA. [37]
This section needs additional citations for verification .(February 2024) |
On March 9, 2021, a coil energization test was being performed on equilibrium field coil no. 1 (EF1) when the coil current rapidly increased, then suddenly flatlined. The reactor was safely shut down over the next few minutes, during which the pressure in the cryostat increased from 10×10−3 Pa to 7000 Pa. Investigations immediately followed.
The incident, which came to be known as the "EF1 feeder incident", was found to be caused by a major short circuit resulting from insufficient insulation of the quench detection wire conductor exit. The formed arc damaged the shells of EF1, causing a helium leak to the cryostat.
In total, 90 locations required repairs and machine sensors needed to be rewired. However, the intricate JT-60SA was designed and assembled with intense precision, meaning access to the machine was sometimes limited. Risks of further delay to plasma operations compounded the issue. [38]
The JT-60SA team was disappointed with the incident, given how close the machine was to operation, but persevered.
Repairs were completed in May 2023 and preparations for operation began. [39]
JT-60SA achieved first plasma on October 23, 2023, making it the largest operational superconducting tokamak in the world as of 2024. [1] The reactor was declared active on December 1, 2023. [40]
(60 stands for JT-60, 60U stands for JT-60U, 60SA stands for JT-60SA) ("60SA I" refers to the initial/integrated research phase of JT-60SA, "60SA II" refers to the extended research phase)
Volume | Current | Major radius | Minor radius | Aspect ratio | Height | Pulse length | Elongation | Triangularity | |
---|---|---|---|---|---|---|---|---|---|
60 | 2.1 MA - 2.6 MA | 3 m | 0.85 m - 0.95 m | 3.52 - 3.15 | 5 s | ||||
60U | 90 m3 | 3 MA | 3.4 m | 1 m | 3.4 | 1.5±0.3 m | 65 s | 1.5±0.3 | |
60SA I | 5.5 MA | 2.97 m | 1.17 m | 2.54 | 2.14 m | 100 s | 1.83 | 0.50 | |
60SA II | 5.5 MA | 2.97 m | 1.18 m | 2.52 | 2.28 m | 100 s | 1.93 | 0.57 |
Material | Baking temp. | One-turn resistance | |
---|---|---|---|
60 | Inconel 625 | 500 °C | > 1.3 mΩ |
60U | Inconel 625 | 300 °C | 0.2 mΩ |
60SA | SS 316L | 200 °C | 16 µΩ |
# | Turns | Material | Coil current | Inductance | Resistance | Time constant | |
---|---|---|---|---|---|---|---|
60 | 18 | 1296 | 52.1 kA | 2.1 H | 84 mΩ | 25 s | |
60U | 18 | 1296 | AgOFCu | 52.1 kA | 2.1 H | 97 mΩ | 21.65 s |
60SA |
A tokamak is a device which uses a powerful magnetic field to confine plasma in the shape of a torus. The tokamak is one of several types of magnetic confinement devices being developed to produce controlled thermonuclear fusion power. As of 2016, it was the leading candidate for a practical fusion reactor. The word "tokamak" is derived from a Russian acronym meaning "toroidal chamber with magnetic coils".
Fusion power is a proposed form of power generation that would generate electricity by using heat from nuclear fusion reactions. In a fusion process, two lighter atomic nuclei combine to form a heavier nucleus, while releasing energy. Devices designed to harness this energy are known as fusion reactors. Research into fusion reactors began in the 1940s, but as of 2024, no device has reached net power, although net positive reactions have been achieved.
This timeline of nuclear fusion is an incomplete chronological summary of significant events in the study and use of nuclear fusion.
ITER is an international nuclear fusion research and engineering megaproject aimed at creating energy through a fusion process similar to that of the Sun. Upon completion of construction of the main reactor and first plasma, planned for late 2025, it will be the world's largest magnetic confinement plasma physics experiment and the largest experimental tokamak nuclear fusion reactor. It is being built next to the Cadarache facility in southern France. ITER will be the largest of more than 100 fusion reactors built since the 1950s, with ten times the plasma volume of any other tokamak operating today.
A reversed-field pinch (RFP) is a device used to produce and contain near-thermonuclear plasmas. It is a toroidal pinch which uses a unique magnetic field configuration as a scheme to magnetically confine a plasma, primarily to study magnetic confinement fusion. Its magnetic geometry is somewhat different from that of the more common tokamak. As one moves out radially, the portion of the magnetic field pointing toroidally reverses its direction, giving rise to the term reversed field. This configuration can be sustained with comparatively lower fields than that of a tokamak of similar power density. One of the disadvantages of this configuration is that it tends to be more susceptible to non-linear effects and turbulence. This makes it a useful system for studying non-ideal (resistive) magnetohydrodynamics. RFPs are also used in studying astrophysical plasmas, which share many common features.
The Large Helical Device (LHD) is a fusion research device located in Toki, Gifu, Japan. It is operated by the National Institute for Fusion Science, and is the world's second-largest superconducting stellarator, after Wendelstein 7-X. The LHD employs a heliotron magnetic field originally developed in Japan.
The T-15 is a Russian nuclear fusion research reactor located at the Kurchatov Institute, which is based on the (Soviet-invented) tokamak design. It was the first industrial prototype fusion reactor to use superconducting magnets to control the plasma. These enormous superconducting magnets confined the plasma the reactor produced, but failed to sustain it for more than just a few seconds. Despite not being immediately applicable, this new technological advancement proved to the USSR that they were on the right path. In the original shape, a toroidal chamber design, it had a major radius of 2.43 m and minor radius 0.7 m.
The Tokamak Fusion Test Reactor (TFTR) was an experimental tokamak built at Princeton Plasma Physics Laboratory (PPPL) circa 1980 and entering service in 1982. TFTR was designed with the explicit goal of reaching scientific breakeven, the point where the heat being released from the fusion reactions in the plasma is equal or greater than the heating being supplied to the plasma by external devices to warm it up.
A fusion energy gain factor, usually expressed with the symbol Q, is the ratio of fusion power produced in a nuclear fusion reactor to the power required to maintain the plasma in steady state. The condition of Q = 1, when the power being released by the fusion reactions is equal to the required heating power, is referred to as breakeven, or in some sources, scientific breakeven.
DEMO, or a demonstration power plant, refers to a proposed class of nuclear fusion experimental reactors that are intended to demonstrate the net production of electric power from nuclear fusion. Most of the ITER partners have plans for their own DEMO-class reactors. With the possible exception of the EU and Japan, there are no plans for international collaboration as there was with ITER.
The Experimental Advanced Superconducting Tokamak (EAST), internal designation HT-7U, is an experimental superconducting tokamak magnetic fusion energy reactor in Hefei, China. The Hefei Institutes of Physical Science is conducting the experiment for the Chinese Academy of Sciences. It has operated since 2006.
HT-7, or Hefei Tokamak-7, is an experimental superconducting tokamak nuclear fusion reactor built in Hefei, China, to investigate the process of developing fusion power. The HT-7 was developed with the assistance of Russia, and was based on the earlier T-7 tokamak reactor. The reactor was built by the Hefei-based Institute of Plasma Physics under the direction of the Chinese Academy of Sciences.
The Plasma Science and Fusion Center (PSFC) at the Massachusetts Institute of Technology (MIT) is a university research center for the study of plasmas, fusion science and technology.
The KSTAR is a magnetic fusion device at the Korea Institute of Fusion Energy in Daejeon, South Korea. It is intended to study aspects of magnetic fusion energy that will be pertinent to the ITER fusion project as part of that country's contribution to the ITER effort. The project was approved in 1995, but construction was delayed by the East Asian financial crisis, which weakened the South Korean economy considerably; however, the project's construction phase was completed on September 14, 2007. The first plasma was achieved in June 2008.
The Japan Atomic Energy Agency is a Japanese atomic energy company. While it inherited the activities of both JNC and JAERI, it also inherited the nickname of JAERI, "Genken" 原研, an abbreviated word for "nuclear research".
Ignitor is the Italian name for a planned tokamak device, developed by ENEA. As of 2022, the device has not been constructed.
SST-1 is a plasma confinement experimental device in the Institute for Plasma Research (IPR), an autonomous research institute under Department of Atomic Energy, India. It belongs to a new generation of tokamaks with the major objective being steady state operation of an advanced configuration plasma. It has been designed as a medium-sized tokamak with superconducting magnets.
The Lockheed Martin Compact Fusion Reactor (CFR) was a fusion power project at Lockheed Martin’s Skunk Works. Its high-beta configuration, which implies that the ratio of plasma pressure to magnetic pressure is greater than or equal to 1, allows a compact design and expedited development. The project was active between 2010 and 2019, after that date there have been no updates and it appears the division has shut down.
SPARC is a tokamak under development by Commonwealth Fusion Systems (CFS) in collaboration with the Massachusetts Institute of Technology (MIT) Plasma Science and Fusion Center (PSFC). Funding has come from Eni, Breakthrough Energy Ventures, Khosla Ventures, Temasek, Equinor, Devonshire Investors, and others.
The construction for the divertor modification from the original open type to the W-shaped semi-closed type for improving the particle control was started on February 1997.
The construction for the divertor modification from the original open type to the W-shaped semi-closed type for improving the particle control was finished in May 1997.
3.1.3 Machine Parameters : A bird's eye view of JT-60SA is shown in Fig. I.3.1-1. Typical parameters of JT-60SA are shown in Table I.3.1-1. The maximum plasma current is 5.5 MA with a relatively low aspect ratio plasma (Rp=3.06 m, A=2.65, κ95=1.76, δ95=0.45) and 3.5 MA for an ITER-shaped plasma (Rp=3.15 m, A=3.1, κ95=1.69, δ95=0.36). Inductive operation with 100s flat top duration will be possible within the total available flux swing of 40 Wb. The heating and current drive system will provide 34 MW of neutral beam injection and 7 MW of ECRF. The divertor target is designed to be water-cooled in order to handle heat fluxes up to15 MW/m2 for long time durations. An annual neutron budget of 4x1021 neutrons is foreseenlots of detail on JT-60SA in section 3
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