Joint European Torus
Encyclopedia
JET, the Joint European Torus, is the largest magnetic confinement plasma physics experiment worldwide currently in operation. Its main purpose is to open the way to future nuclear fusion
experimental tokamak
reactors such as ITER
and :DEMO.
airfield near Culham
, Oxfordshire – RNAS Culham (HMS Hornbill), in the UK: the construction of the buildings which house the project was undertaken by Tarmac Construction, starting in 1978 with the Torus Hall being completed in January 1982. Construction of the experiment itself began immediately after the completion of the Torus Hall, with the first experiments beginning in 1983.
The components for the JET experiment came from manufacturers all over Europe, with these components transported to the site.
Because of the extremely high power requirements for the tokamak
, and the fact that power draw from the main grid is limited, two large flywheel generators were constructed to provide this necessary power. Each 775 ton flywheel can spin up to 225 rpm. One generator provides power for the 32 toroidal field coils, the other for inner poloidal field coils. The outer field coils draw their power from the grid.
with a discriminatory employment system that allowed non-British staff to be employed at more than twice the salaries of their British equivalents. The British staff eventually had this practice declared illegal, and substantial damages were paid at the end of 1999 to UKAEA staff, and later to contractors. This was the immediate cause of the ending of Euratom's operation of the facility.
In December 1999, JET's international contract ended and the United Kingdom Atomic Energy Authority
(UKAEA) then took over managing the safety and operation of the JET facilities on behalf of its European partners. From that time (2000), JET's experimental programme was then co-ordinated by the European Fusion Development Agreement (EFDA
) Close Support Unit.
JET operated throughout 2003, with the year culminating in experiments using small amounts of tritium
. For most of 2004, JET was shut down for a series of major upgrades, increasing its total available heating power to over 40 MW, enabling further studies relevant to the development of ITER
to be undertaken. In late September 2006, the C16 experimental campaign was started, with the objective of studying ITER-like operation scenarios.
In October 2009, a 15-month shutdown period was started, and improvements were made to the tokamak, including replacing carbon
components in the vacuum vessel with tungsten
and beryllium
ones, to bring JET's components more in line with those planned for ITER. Heating power was also increased by 50%, bringing the neutral beam power available to the plasma up to 34MW, and diagnostic and control capabilities were improved. In total, over 86,000 components were changed in the torus during the shutdown.
In mid-May 2011, the shutdown reached its end. The first experimental campaign after the installation of the “ITER-Like Wall” started on 2 September.
facilities to cope with the radioactivity produced by deuterium
-tritium
(D-T) fuel, which is the fuel proposed for the first generation of fusion power plants. Pending construction of ITER
, JET remains the only large fusion reactor with facilities dedicated to handling the radioactivity released from D-T fusion. The power production record-breaking runs from JET and TFTR used 50-50 D-T fuel mixes.
During a full D-T experimental campaign in 1997 JET achieved a world record peak fusion power of 16 MW which equates to a measured gain Q
, of approximately 0.7. Q is the ratio of fusion power produced to input heating power. In order to achieve break-even, a Q value greater than 1 is required. This figure does not include other power requirements for operation, most notably confinement. A commercial fusion reactor would probably need a Q value somewhere between 15 and 22. As of 1998, a higher Q of 1.25 is claimed for the JT-60
tokamak
; however, this was not achieved under real D-T conditions but extrapolated from experiments performed with a pure deuterium (D-D) plasma. Similar extrapolations have not been made for JET, but it is likely that increases in Q over the 1997 measurements could now be achieved if permission to run another full D-T campaign was granted. Work has now begun on ITER
to further develop fusion power.
Nuclear fusion
Nuclear fusion is the process by which two or more atomic nuclei join together, or "fuse", to form a single heavier nucleus. This is usually accompanied by the release or absorption of large quantities of energy...
experimental tokamak
Tokamak
A tokamak is a device using a magnetic field to confine a plasma in the shape of a torus . Achieving a stable plasma equilibrium requires magnetic field lines that move around the torus in a helical shape...
reactors such as ITER
ITER
ITER is an international nuclear fusion research and engineering project, which is currently building the world's largest and most advanced experimental tokamak nuclear fusion reactor at Cadarache in the south of France...
and :DEMO.
Construction
The reactor is situated on a retired NavyRoyal Navy
The Royal Navy is the naval warfare service branch of the British Armed Forces. Founded in the 16th century, it is the oldest service branch and is known as the Senior Service...
airfield near Culham
Culham
Culham is a village and civil parish on the north bank of the River Thames, just over south of Abingdon in Oxfordshire.-Manor:The toponym comes from the Old English Cula's hamm, referring to the village's position in a bend of the Thames...
, Oxfordshire – RNAS Culham (HMS Hornbill), in the UK: the construction of the buildings which house the project was undertaken by Tarmac Construction, starting in 1978 with the Torus Hall being completed in January 1982. Construction of the experiment itself began immediately after the completion of the Torus Hall, with the first experiments beginning in 1983.
The components for the JET experiment came from manufacturers all over Europe, with these components transported to the site.
Because of the extremely high power requirements for the tokamak
Tokamak
A tokamak is a device using a magnetic field to confine a plasma in the shape of a torus . Achieving a stable plasma equilibrium requires magnetic field lines that move around the torus in a helical shape...
, and the fact that power draw from the main grid is limited, two large flywheel generators were constructed to provide this necessary power. Each 775 ton flywheel can spin up to 225 rpm. One generator provides power for the 32 toroidal field coils, the other for inner poloidal field coils. The outer field coils draw their power from the grid.
Operating history
JET was originally set up by EuratomEuropean Atomic Energy Community
The European Atomic Energy Community is an international organisation which is legally distinct from the European Union , but has the same membership, and is governed by the EU's institutions....
with a discriminatory employment system that allowed non-British staff to be employed at more than twice the salaries of their British equivalents. The British staff eventually had this practice declared illegal, and substantial damages were paid at the end of 1999 to UKAEA staff, and later to contractors. This was the immediate cause of the ending of Euratom's operation of the facility.
In December 1999, JET's international contract ended and the United Kingdom Atomic Energy Authority
United Kingdom Atomic Energy Authority
The United Kingdom Atomic Energy Authority is a UK government research organisation responsible for the development of nuclear fusion power. It is an executive non-departmental public body of the Department for Business, Innovation and Skills and was formerly chaired by Lady Barbara Judge CBE...
(UKAEA) then took over managing the safety and operation of the JET facilities on behalf of its European partners. From that time (2000), JET's experimental programme was then co-ordinated by the European Fusion Development Agreement (EFDA
EFDA
The European Union has a strongly coordinated nuclear fusion research programme. At the European level, the so-called is the international legal framework under which member states cooperate in the fields of nuclear fusion research....
) Close Support Unit.
JET operated throughout 2003, with the year culminating in experiments using small amounts of tritium
Tritium
Tritium is a radioactive isotope of hydrogen. The nucleus of tritium contains one proton and two neutrons, whereas the nucleus of protium contains one proton and no neutrons...
. For most of 2004, JET was shut down for a series of major upgrades, increasing its total available heating power to over 40 MW, enabling further studies relevant to the development of ITER
ITER
ITER is an international nuclear fusion research and engineering project, which is currently building the world's largest and most advanced experimental tokamak nuclear fusion reactor at Cadarache in the south of France...
to be undertaken. In late September 2006, the C16 experimental campaign was started, with the objective of studying ITER-like operation scenarios.
In October 2009, a 15-month shutdown period was started, and improvements were made to the tokamak, including replacing carbon
Carbon
Carbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds...
components in the vacuum vessel with tungsten
Tungsten
Tungsten , also known as wolfram , is a chemical element with the chemical symbol W and atomic number 74.A hard, rare metal under standard conditions when uncombined, tungsten is found naturally on Earth only in chemical compounds. It was identified as a new element in 1781, and first isolated as...
and beryllium
Beryllium
Beryllium is the chemical element with the symbol Be and atomic number 4. It is a divalent element which occurs naturally only in combination with other elements in minerals. Notable gemstones which contain beryllium include beryl and chrysoberyl...
ones, to bring JET's components more in line with those planned for ITER. Heating power was also increased by 50%, bringing the neutral beam power available to the plasma up to 34MW, and diagnostic and control capabilities were improved. In total, over 86,000 components were changed in the torus during the shutdown.
In mid-May 2011, the shutdown reached its end. The first experimental campaign after the installation of the “ITER-Like Wall” started on 2 September.
Equipment capability
JET is equipped with remote handlingRemote handling
Remote handling is the synergistic combination of technology and engineering management systems to enable operators to safely, reliably and repeatedly perform manipulation of items without being in personal contact with those items.-Overview:...
facilities to cope with the radioactivity produced by deuterium
Deuterium
Deuterium, also called heavy hydrogen, is one of two stable isotopes of hydrogen. It has a natural abundance in Earth's oceans of about one atom in of hydrogen . Deuterium accounts for approximately 0.0156% of all naturally occurring hydrogen in Earth's oceans, while the most common isotope ...
-tritium
Tritium
Tritium is a radioactive isotope of hydrogen. The nucleus of tritium contains one proton and two neutrons, whereas the nucleus of protium contains one proton and no neutrons...
(D-T) fuel, which is the fuel proposed for the first generation of fusion power plants. Pending construction of ITER
ITER
ITER is an international nuclear fusion research and engineering project, which is currently building the world's largest and most advanced experimental tokamak nuclear fusion reactor at Cadarache in the south of France...
, JET remains the only large fusion reactor with facilities dedicated to handling the radioactivity released from D-T fusion. The power production record-breaking runs from JET and TFTR used 50-50 D-T fuel mixes.
During a full D-T experimental campaign in 1997 JET achieved a world record peak fusion power of 16 MW which equates to a measured gain Q
Fusion energy gain factor
The 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 is referred to as breakeven.In a fusion power reactor a plasma must be...
, of approximately 0.7. Q is the ratio of fusion power produced to input heating power. In order to achieve break-even, a Q value greater than 1 is required. This figure does not include other power requirements for operation, most notably confinement. A commercial fusion reactor would probably need a Q value somewhere between 15 and 22. As of 1998, a higher Q of 1.25 is claimed for the JT-60
JT-60
JT-60 is the flagship of Japan's magnetic fusion program, previously run by the Japan Atomic Energy Research Institute and currently run by the Japan Atomic Energy Agency's Naka Fusion Institute in Ibaraki Prefecture, Japan...
tokamak
Tokamak
A tokamak is a device using a magnetic field to confine a plasma in the shape of a torus . Achieving a stable plasma equilibrium requires magnetic field lines that move around the torus in a helical shape...
; however, this was not achieved under real D-T conditions but extrapolated from experiments performed with a pure deuterium (D-D) plasma. Similar extrapolations have not been made for JET, but it is likely that increases in Q over the 1997 measurements could now be achieved if permission to run another full D-T campaign was granted. Work has now begun on ITER
ITER
ITER is an international nuclear fusion research and engineering project, which is currently building the world's largest and most advanced experimental tokamak nuclear fusion reactor at Cadarache in the south of France...
to further develop fusion power.
Machine information
- Weight of the vacuum vessel: 100 tonnes
- Weight of the toroidal field coils: 384 tonnes
- Weight of the iron core: 2800 tonnes
- Wall material: Primarily carbon fibre composite, berylliumBerylliumBeryllium is the chemical element with the symbol Be and atomic number 4. It is a divalent element which occurs naturally only in combination with other elements in minerals. Notable gemstones which contain beryllium include beryl and chrysoberyl...
coated. - Plasma major radius: 2.96 m
- Plasma minor radius: 2.10 m (vertical), 1.25 m (horizontal)
- Flat top pulse length: 20–60 s
- Toroidal magnetic field (on plasma axis): 3.45 TTesla (unit)The tesla is the SI derived unit of magnetic field B . One tesla is equal to one weber per square meter, and it was defined in 1960 in honour of the inventor, physicist, and electrical engineer Nikola Tesla...
- Plasma current: 3.2 MA (circular plasma), 4.8 MA (D-shape plasma)
- Lifetime of the plasma: 20–60 s
- Auxiliary heating:
- Neutral beam injection heating ≤23 MW
- Radio frequency heating ≤15 MW
- Major diagnostics:
- Visible/infrared video cameraVideo cameraA video camera is a camera used for electronic motion picture acquisition, initially developed by the television industry but now common in other applications as well. The earliest video cameras were those of John Logie Baird, based on the electromechanical Nipkow disk and used by the BBC in...
s - Numerous magnetic coils – provide magnetic field, current and energy measurements
- Thomson scatteringThomson scatteringThomson scattering is the elastic scattering of electromagnetic radiation by a free charged particle, as described by classical electromagnetism. It is just the low-energy limit of Compton scattering: the particle kinetic energy and photon frequency are the same before and after the scattering...
spectroscopy – provides electron temperature and electron density profiles of the plasma - Charge exchange spectroscopy – provides impurity ion temperature, density and rotation profiles
- Interferometers – measure line integrated plasma density
- Electron cyclotron emission antennas – fast, high resolution electron temperature profiles
- Visible/UV/X-rayX-rayX-radiation is a form of electromagnetic radiation. X-rays have a wavelength in the range of 0.01 to 10 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz and energies in the range 120 eV to 120 keV. They are shorter in wavelength than UV rays and longer than gamma...
spectrometerSpectrometerA spectrometer is an instrument used to measure properties of light over a specific portion of the electromagnetic spectrum, typically used in spectroscopic analysis to identify materials. The variable measured is most often the light's intensity but could also, for instance, be the polarization...
s – temperatures and densities - NeutronNeutronThe neutron is a subatomic hadron particle which has the symbol or , no net electric charge and a mass slightly larger than that of a proton. With the exception of hydrogen, nuclei of atoms consist of protons and neutrons, which are therefore collectively referred to as nucleons. The number of...
diagnostics:- Neutron counting: Number of neutrons leaving the plasma relates directly to the fusion power.
- Neutron spectroscopy – Neutron energy relates to the ion velocity distribution and hence the fuel reactivity.
- BolometerBolometerA bolometer is a device for measuring the power of incident electromagnetic radiation via the heating of a material with a temperature-dependent electrical resistance. It was invented in 1878 by the American astronomer Samuel Pierpont Langley...
s – energy loss from the plasma - Various material probes – inserted into the plasma to take direct measurements of flow rates and temperatures
- Soft X-ray cameras to examine MHD properties of plasmas
- Time resolved neutron yield monitor
- Hard X-ray monitors
- Electron Cyclotron Emission Spatial Scanners
- Visible/infrared video camera
External links
- EFDA-JET web site
- Culham Centre for Fusion Energy
- The United Kingdom Atomic Energy Authority
- IAEA's information about JET
- Photos from JET torus hall