Political imperative drives research partners
Saturday, 17 November 2007
Clive Cookson
THE world gained a new international organisation last month. Iter - which stands for International Thermonuclear Energy Reactor and also means "the way" in Latin - was formally established on October 24, with a mission that could hardly be more long-range or more ambitious. Iter aims to demonstrate that nuclear fusion can be a clean and affordable energy source for the late 21st century.
Fusion research has always been a forward-thinking activity, and its practitioners have long had to face quips along the lines of "fusion is the power of the future - and always will be".
The first attempts to generate energy from fusion (combining light atomic nuclei to form a heavier one) were made in the early 1950s. The sun and stars -- and the H-bomb -- depend on fusion, and the idea of taming the reaction to generate power on Earth was irresistible.
Unfortunately the technical and engineering challenges turned out to be far greater than the first fusion enthusiasts had anticipated. And there was no great political imperative to develop fusion power during the late 20th century, while gas, oil and coal supplies were plentiful and relatively cheap and no one was worrying about the impact on the global climate of burning them.
After 30 years of slow but perceptible progress with national and regional fusion experiments, the first proposal to set up Iter as an international project was made in 1985 by Mikhail Gorbachev, the Soviet leader, to President Ronald Reagan of the US.
The following 22 years have been taken up with protracted negotiations between the potential Iter partners, together with detailed design work on the doughnut-shaped "tokamak" reactor.
The negotiating breakthrough came in June 2005 when the seven Iter partners -- China, the European Union, India, Japan, South Korea, Russia and the US-agreed to locate Iter at Cadarache in the south of France.
So Iter now has a site, a formal organisation (headed by Kaname Ikeda of Japan), a schedule with building due to start in 2009 and finish in 2016, and an estimated budget of €5.0bn for construction and a further €5.0bn for commissioning and operations over 20 years. Iter builds on its partners' experience of running smaller tokamaks such as JT-60 in Japan, TFTR in the US and Europe's JET in the UK.
In a tokamak, the fuel -- a mixture of deuterium and tritium, two isotopes of hydrogen -- is heated to temperatures above 100m°C, forming an electrically charged "plasma" that is even hotter than the sun. Superconducting magnets around the tokamak generate a strong magnetic field to stop the plasma touching the walls of the reaction vessel, which would instantly stop the fusion reaction.
The process can also be stopped within seconds by turning off the external fuel supply, which means that a fusion power plant can be shut down safely and quickly with no possibility of a runaway nuclear reaction. Advocates of fusion power say it is far safer than today's fission-based nuclear plants -- and far cleaner because it produces only minimal amounts of radioactive by-products. In its linear dimensions, Iter will be more than twice the size of the largest existing tokamaks, JET and JT-60, with a reactor vessel 10 metres high. Its volume will be 10 times greater.
JET (at Culham near Oxford) is the only reactor yet to have produced a significant amount of fusion energy: 16 megawatts in short bursts up to a second. But this was less than the electrical energy input required to heat up the plasma.
Iter aims to generate a "burning plasma" in which the fusion reaction sustains itself for 10 minutes and produces 500 megawatts -- as much as a small power station. But it will not generate electricity for a power grid. That will be a job for its successor, Demo, which will be the first plant to demonstrate the large-scale production of electric power by fusion.
If all goes well, Demo could come into operation by about 2035, generating electricity continuously on a large scale. It would lead fusion into the industrial era and open the way towards the first commercial fusion plants -- possibly around 2050. Although the world has put most of its fusion eggs into the Iter basket, tokamaks are not the only potential route to fusion power. Some experts believe a spiral shaped reactor called a stellarator would be a better vessel in which to contain the plasma with a magnetic field.
A different approach is not to use magnetic confinement at all but to initiate nuclear fusion by focusing ultra-powerful lasers on to the deuterium-tritium fuel. Governments have committed relatively modest funding to develop alternatives to the tokamak, but it is inconceivable in today's political and financial climate that another project could be funded on anything like the scale of Iter.
THE world gained a new international organisation last month. Iter - which stands for International Thermonuclear Energy Reactor and also means "the way" in Latin - was formally established on October 24, with a mission that could hardly be more long-range or more ambitious. Iter aims to demonstrate that nuclear fusion can be a clean and affordable energy source for the late 21st century.
Fusion research has always been a forward-thinking activity, and its practitioners have long had to face quips along the lines of "fusion is the power of the future - and always will be".
The first attempts to generate energy from fusion (combining light atomic nuclei to form a heavier one) were made in the early 1950s. The sun and stars -- and the H-bomb -- depend on fusion, and the idea of taming the reaction to generate power on Earth was irresistible.
Unfortunately the technical and engineering challenges turned out to be far greater than the first fusion enthusiasts had anticipated. And there was no great political imperative to develop fusion power during the late 20th century, while gas, oil and coal supplies were plentiful and relatively cheap and no one was worrying about the impact on the global climate of burning them.
After 30 years of slow but perceptible progress with national and regional fusion experiments, the first proposal to set up Iter as an international project was made in 1985 by Mikhail Gorbachev, the Soviet leader, to President Ronald Reagan of the US.
The following 22 years have been taken up with protracted negotiations between the potential Iter partners, together with detailed design work on the doughnut-shaped "tokamak" reactor.
The negotiating breakthrough came in June 2005 when the seven Iter partners -- China, the European Union, India, Japan, South Korea, Russia and the US-agreed to locate Iter at Cadarache in the south of France.
So Iter now has a site, a formal organisation (headed by Kaname Ikeda of Japan), a schedule with building due to start in 2009 and finish in 2016, and an estimated budget of €5.0bn for construction and a further €5.0bn for commissioning and operations over 20 years. Iter builds on its partners' experience of running smaller tokamaks such as JT-60 in Japan, TFTR in the US and Europe's JET in the UK.
In a tokamak, the fuel -- a mixture of deuterium and tritium, two isotopes of hydrogen -- is heated to temperatures above 100m°C, forming an electrically charged "plasma" that is even hotter than the sun. Superconducting magnets around the tokamak generate a strong magnetic field to stop the plasma touching the walls of the reaction vessel, which would instantly stop the fusion reaction.
The process can also be stopped within seconds by turning off the external fuel supply, which means that a fusion power plant can be shut down safely and quickly with no possibility of a runaway nuclear reaction. Advocates of fusion power say it is far safer than today's fission-based nuclear plants -- and far cleaner because it produces only minimal amounts of radioactive by-products. In its linear dimensions, Iter will be more than twice the size of the largest existing tokamaks, JET and JT-60, with a reactor vessel 10 metres high. Its volume will be 10 times greater.
JET (at Culham near Oxford) is the only reactor yet to have produced a significant amount of fusion energy: 16 megawatts in short bursts up to a second. But this was less than the electrical energy input required to heat up the plasma.
Iter aims to generate a "burning plasma" in which the fusion reaction sustains itself for 10 minutes and produces 500 megawatts -- as much as a small power station. But it will not generate electricity for a power grid. That will be a job for its successor, Demo, which will be the first plant to demonstrate the large-scale production of electric power by fusion.
If all goes well, Demo could come into operation by about 2035, generating electricity continuously on a large scale. It would lead fusion into the industrial era and open the way towards the first commercial fusion plants -- possibly around 2050. Although the world has put most of its fusion eggs into the Iter basket, tokamaks are not the only potential route to fusion power. Some experts believe a spiral shaped reactor called a stellarator would be a better vessel in which to contain the plasma with a magnetic field.
A different approach is not to use magnetic confinement at all but to initiate nuclear fusion by focusing ultra-powerful lasers on to the deuterium-tritium fuel. Governments have committed relatively modest funding to develop alternatives to the tokamak, but it is inconceivable in today's political and financial climate that another project could be funded on anything like the scale of Iter.