Halfway to reality7 March 2018
Ten years after its inception, the international Iter project has passed the halfway mark. Judith Perera reviews the progress.
THE ITER ORGANISATION CELEBRATED ITS 10th anniversary in 2017 after what it described as “a very significant year.” The project, which is being built in Cadarache, southern France by a scientific partnership of 35 countries also passed the halfway mark towards first plasma. It will be the world’s largest experimental tokamak fusion facility. Europe contributes almost half of the construction costs (45.6%), while the other six members – China, India, Japan, South Korea, Russia and the United States – contribute equally to the rest (9.1% each).
All the milestones set by the Iter Council were met in 2017. Preparation for machine assembly has begun and the cryoplant, the twin magnet power conversion buildings, and the cooling tower zone have received their first equipment. In factories on three continents, Iter members continued to manufacture strategic Iter components that were delivered to the site as planned. In the Poloidal Field Coil Winding Facility, Europe began manufacturing the fifth poloidal field coil. Nearby in the Cryostat Workshop, Indian contractors started work on a second cryostat section—the lower cylinder—and continued to advance welding and nondestructive examination testing of the cryostat base.
When the Iter project was formally launched in 2007 the estimated cost was €5bn. Construction began in 2010 but there have been delays. First plasma, originally scheduled for 2018, and the start of deuterium-tritium operation for 2026 were deferred until November 2019 and March 2027, respectively. By 2011, the budget forecast had risen to about €16bn and in May 2016 newly appointed Iter chief Bernard Bigot said the project would be delayed by more than a decade and incur cost overruns of another €4bn, estimating the overall cost to commissioning to be at least €18bn ($22bn).
More than 80% of the cost of Iter is contributed as components manufactured by the partners. Many of these massive components of the Iter machine must be precisely fitted—for example, 17-metre-high magnets with less than a millimetre of tolerance. Each component must be ready on time to fit into the Master Schedule for machine assembly. Members asked for this arrangement for three reasons. First, most of the Iter costs paid by any member are paid to that member’s companies, which means the funding stays in-country. Second, the companies involved build new industrial expertise in major fields—such as electromagnetism, cryogenics, robotics, and materials science. Third, this new expertise leads to innovation and spin-offs in other fields.
Iter meets its milestones
“For the past two years, we have met every agreed project milestone. This has not happened easily,” said Bigot in an end-of-year statement. “A project of this complexity is full of risks; and our schedule to first plasma in 2025 is set with no ‘float’ or contingency. Effective risk management is a daily discipline at Iter.”
Bigot said the design has taken advantage of the best expertise of every member’s scientific and industrial base. “No country could do this alone. We are all learning from each other, for the world’s mutual benefit. Looking ahead, we will need the commitment and support of every member to maintain this performance.”
Plans for 2018 include starting integrated commissioning of an ion source test bed by March. At the PRIMA neutral beam test facility in Padua, Italy, the key technologies of Iter’s powerful heating neutral beam system will be tested and qualified on two test beds. The first of these, SPIDER (for Source for the Production of Ions of Deuterium Extracted from a Radio frequency plasma) will be ready for integrated testing during the first quarter of 2018.
Access to the Tokamak assembly area depends on the maturity of Tokamak Building civil works. The target is to finish the bioshield and the concrete crown by the second quarter of 2018 to allow access for the first components to be installed.
The first toroidal field coil is expected to arrive from Japan in the third quarter of 2018. Weighing 310t each, and measuring 9x17m, the toroidal field coils are among the largest components of the Iter machine. Nine will be produced in Japan and ten in Europe (18 and one spare).
The first vacuum vessel sector, measuring over 14m and weighing 440t, is expected to arrive from Korea in the fourth quarter of 2018. Nine sectors in all, supported by the overhead in-pit assembly tool, will be aligned and welded together in the Tokamak assembly pit. Fifty-three port structures will also be welded into place during the assembly of the vacuum vessel.
The final goal is not just circulating plasma [scheduled for 2025], but fusing deuterium and tritium to create a ‘burning’ plasma that generates significantly more energy than it uses.
Iter’s successor, the Demonstration Fusion Power Reactor, or DEMO, will aim to demonstrate the continuous output of energy, supplying electricity to the grid. According to Eurofusion, DEMO is expected to follow Iter by 2050. Currently in the design stages, DEMO must have linear dimensions about 15% larger than Iter and an about 30% greater plasma density.
Work continues at JET
Meanwhile, the UK’s Culham Centre for Fusion Energy (CCFE) and the Joint European Torus (JET) have continued experimental work as the precursor to Iter, despite growing concerns about how Brexit may affect the project. JET is operated by the CCFE under a contract between the European Commission and the UKAEA. It is used by all European fusion laboratories in the Eurofusion consortium. The peaceful use of nuclear energy within the EU is governed by the 1957 Euratom Treaty. The UK government has said it intends to leave Euratom as part of the Brexit process, but officials have tried to reassure the nuclear industry that the effect will be minimal. “There is political commitment right across the British government to ensure as much continuity as possible for the nuclear industry,” David Wagstaff, deputy director of the Euratom exit at the Department for Business, Energy and Industrial Strategy (BEIS), told delegates at the UK Nuclear Industry Association’s annual conference in London in December. BEIS is working “very closely and collaboratively”, he said, with the Department for Exiting the European Union.
In December, the UK government announced investment of £86m to fund the building and operation of a National Fusion Technology Platform (NaFTeP) at Culham, which is expected to open in 2020. BEIS said the new funding is part of a series of measures to support the development of ‘next-generation nuclear technology’, following publication of the government’s Industrial Strategy white paper in November. NaFTeP comprises two new centres of excellence: Hydrogen-3 Advanced Technology (H3AT), which will research how to process and store tritium, one of the fuels that will power commercial fusion reactors; and Fusion Technology Facilities (FTF), which will carry out thermal, mechanical, hydraulic and electromagnetic tests on prototype components under the conditions experienced inside fusion reactors. NaFTeP will “provide a powerful signal of the UK’s intent to continue its participation in international science collaboration after leaving the European Union”, UKAEA said.
UKAEA said the new facilities will help to secure around £1bn ($1.35bn) in contracts from Iter. So far, 38 UK companies have won contracts totalling more than €500m from Iter. Looking ahead, UKAEA said the facilities will enable development of technology for the first nuclear fusion power plants and put UK industry in a strong position to exploit their commercialisation. H3AT and FTF will work closely with the industrial supply chain to create knowledge to position them for the next phase of Iter procurements in areas including the tritium plant, hot cells, measurement systems, assembly, maintenance and reactor materials, UKAEA said. NaFTeP is expected to create around 100 jobs at Culham and many more in the wider nuclear industry supply chain.
Progress in Korea and China
A number of other fusion projects worldwide announced progress during 2017.
The Korean Superconducting Tokamak Advanced Research (KSTAR), a tokamak nuclear fusion reactor, which achieved 70 seconds in high-performance plasma operation at the end of 2016 at South Korea’s National Fusion Research Institute (NFRI), has now significantly improved the stability of the elongated plasma in the facility. A team of US and Korean researchers, led by physicist Dennis Mueller of the US Department of Energy’s (DOE) Princeton Plasma Physics Laboratory (PPPL), has now sharply improved the stability of the elongated plasma in KSTAR, successfully demonstrating a method to control the vertical instability of the plasma. “As the plasma got taller it moved away from stable operation,” Mueller told the 59th annual meeting of the American Physical Society Division of Plasma Physics in October. “The new correction method stops the plasma from bouncing up and down by stabilizing the vertical centre of the plasma. Control of the vertical instability has allowed for taller plasmas in KSTAR than the original design specifications.” This was achieved using new magnetic sensors developed at KSTAR.
In China, researchers at the Experimental Advanced Superconducting Tokamak (EAST) at the Hefei-based Institute of Plasma Physics announced in July that they had set a world record by achieving 101.2 seconds of steady- state H-mode operation of the tokamak. In 2016, the EAST team achieved over 60 seconds of steady-state long-pulse H-mode discharge of the device. Similar experiments in other countries have created plasmas that lasted longer but were less stable and difficult to control for the purpose of power generation.
In December, the Chinese central government announced it was backing the project for the next-step experimental fusion power station, DEMO, launching a competition among cities in China to host the project. Hefei is hoping to be selected. According to a timetable posted by the Chinese Academy of Sciences, design work on DEMO will continue, and construction will start in 2021. The reactor will be built in parallel with Iter rather than waiting for results from Iter, expected in 2025.
Progress has also been reported from Wendelstein 7-X (W7-X), the world’s largest stellarator, which began operating in 2015 at the Max Planck Institute of Plasma Physics in Greifswald, Germany, and is seen as a competitor to tokamak technology. Stellerators also use magnetic confinement, but are designed differently. The W7-X was intended to show that the earlier weaknesses in the stellarator fusion concept had been addressed. In September, experiments resumed at the reactor after a 15-month break. A recent upgrade means it is now capable of higher heat and longer pulses. The device was also fitted with measuring instruments that allowed scientists to track the turbulence in the plasma. “We shall be able for the first time to check whether the promising predictions of theory for a completely optimised stellarator are correct,” said project head Thomas Klinger.
An alternative fusion technology to the magnetic confinement technology of the tokamak and stellerator is inertial confinement fusion (ICF) which aims to initiate nuclear fusion reactions by heating and compressing a fuel target using a powerful laser. The largest operational ICF experiment is the National Ignition Facility (NIF) in the USA, which typically uses a pellet containing a mixture of deuterium and tritium as the target. A similar large-scale device in France, Laser Mégajoule, was officially inaugurated in October 2014. However, progress is slow.
Hydrogen-boron fusion might be a faster alternative. In December, in a paper in Laser and Particle Beams, Heinrich Hora from the University of New South Wales (UNSW) in Sydney and international colleagues proposed a new design for ICF using a target of hydrogen-boron. “I think this puts our approach ahead of all other fusion energy technologies,” said Hora, an emeritus professor of theoretical physics at UNSW, who predicted in the 1970s that fusing hydrogen and boron might be possible without the need for thermal equilibrium. Hydrogen-boron fusion is achieved using two powerful lasers in rapid bursts, which apply precise non-linear forces to compress the nuclei together and create the fusion reaction.
Hydrogen-boron fusion produces no neutrons and, therefore, no radioactivity in its primary reaction. Dramatic advances in laser technology are close to making the two-laser approach feasible, according to UNSW, and a spate of recent experiments around the world indicate that an ‘avalanche’ fusion reaction could be triggered in the trillionth-of-a-second blast from a petawatt-scale laser pulse, whose fleeting bursts pack a quadrillion watts of power. If scientists could exploit this avalanche, Hora said, a breakthrough in proton-boron fusion was imminent.
An Australian spin-off company, HB11 Energy, holds the patents for Hora’s hydrogen-boron fusion process. “If the next few years of research don’t uncover any major engineering hurdles, we could have prototype reactor within a decade,” said Warren McKenzie, managing director of HB11. “From an engineering perspective, our approach will be a much simpler project because the fuels and waste are safe, the reactor won’t need a heat exchanger and steam turbine generator, and the lasers we need can be bought off the shelf,” he added.