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ITER NEWSLINE 211
The performance degradation problem that was found in a conductor for ITER's central solenoid last year seems to be solved.
As part of a comprehensive R&D program that was launched following unsatisfactory test results, a new conductor was fabricated; recent tests performed at the SULTAN Test Facility in Switzerland show good results. The new conductor sample was submitted to 10,000 magnetic load cycles and two warm-up / cool-down cycles, mimicking one-sixth of the full operational life of ITER's central solenoid.
"Compared to the tests performed last year, the conductor now shows a level of degradation much closer to that originally anticipated in the design, and the rate of degradation with magnetic cycling is stabilizing," explains Neil Mitchell, head of ITER's Magnet Division.
The tested conductor sample has two new features with respect to previous samples: First, it relies on a different strand manufacturing process, referred to as "internal tin", which has shown good resistance to mechanical bending loads in individual strand tests. Second, it compares two design options: In one, the original cable design is used, with two superconducting strands (copper to non-copper ratio 1:1.0) and one copper strand forming the triplet that is the basis of the cable structure. In the other, three superconducting strands (copper to non-copper ratio 1:1.5) are used. In this three-superconducting strand option, the loads on individual strands are reduced and extra superconducting material is added.
The root cause of the problems observed in the original tests is believed to be the high magnetic loads accumulating on the strands in the cable-in-conduit conductor. To maintain a low level of coupling losses in the pulsed conditions required in a central solenoid designed for a tokamak machine such as ITER, the contact between strands needs to be limited. However, the strands also need to be supported transversally to limit bending under the Lorentz load. If the strands deform too much, it can lead to gradual fracture of the brittle superconducting filaments and degradation in superconducting performance.
Maria van der Hoeven took over as Executive Director of the International Energy Agency (IEA) on 1 September 2011. Previously, Ms. Van der Hoeven served as Minister of Economic Affairs of the Netherlands from February 2007 to October 2010. To many people within the fusion community she is not an unknown name as she played an important role during the Dutch presidency of the Council of the European Union when the ITER site negotiations were at a critical stage. Now—as ITER is under construction—we asked the prominent proponent of fusion about her opinion of the ITER Project and its potential.
Newsline: The 2011 World Energy Outlook was published by your agency last November. What does it tell us about the energy that the next generations will use to heat their homes and prepare their meals?
Maria van der Hoeven: In the future, electricity will become an increasingly important fuel in the residential sector as developing countries switch away from less efficient sources of heating and cooking (such as traditional biomass) and as demand for electrical appliances continues to rise. Currently electricity accounts for about 20 percent of residential energy consumption, but we project that it will rise to 30 percent by 2035. The increasing electrification of our economies will raise new questions about introducing and deploying new technologies, the development and integration of power grids (and increasingly "smart" grids), efficient electricity storage, electricity security in general, and much more. However it will also create more flexibility in terms of energy input fuels and open more of the economy to power-generating technologies, including (potentially) fusion.
What ties exist between IEA and ITER?
To achieve energy security, economic growth and environmental protection, the IEA has encouraged and supported international collaborative research, development and deployment (RDD&D) across the mix of energy technologies since its founding. The IEA thus supports Member governments, non-Member participants and industrial partners to share resources and multiply results.
The IEA Fusion Power Co-ordinating Committee (FPCC) provides a platform for stakeholders to share results of fusion activities worldwide. The ITER project, the International Atomic Energy Agency, the European Commission (EURATOM), the International Tokamaks Physics Activity (ITPA), and the Nuclear Energy Agency (experiments database) are among these participants.
The FPCC also oversees the activities of eight fusion Implementing Agreements, or international collaborative working groups, that examine specific policy and technical aspects of fusion power including:
Our two organizations are also linked by individuals. Three participants from the IEA fusion community have been named to leadership positions for ITER. They include the ITER Director-General Osamu Motojima, the ITER Deputy Director-General Rich Hawryluk, and the Chair of the ITER Council Hideyuki Takatsu.
I personally look forward to increasing the contacts between our organizations, and hope to make a working visit myself to Cadarache in the coming year.
As Minister for Research in the Netherlands you played a vital role in the ITER site negotiations. Despite significant challenges since then, the ITER project is now under construction.
I am pleased to see that the ITER Project has indeed advanced and that steps have been taken recently to address budgetary and management issues. Since taking up my role as Executive Director at the IEA, my priorities have been to establish a strategic vision and implementation plan for this energy agency. Working to leverage the IEA's assets to bolster its impact worldwide—while delivering high quality to Member governments within stringent resource constraints—has been at the heart of my task. I therefore understand the challenges that ITER faces, and I applaud its progress.
"Fusion has the potential to be a game-changer"
During a visit to the German tokamak TEXTOR in 2003 you stated that politicians needed more information about fusion and that they are often not well briefed. From your perspective as Executive Director of the IEA, how can awareness of the potential of clean technologies such as fusion be raised?
The IEA actively supports clean technology deployment through analysis and reporting such as our flagship Energy Technology Perspectives publications, our input to the Clean Energy Ministerial, and other work. We also support the spread of information via the Energy Technology Network and the International Low-Carbon Energy Technology Platform. These products and platforms can help to raise awareness among both policy makers and stakeholders.
Based on IEA projections, our future energy needs will be substantial. Therefore we must continue to support research and development today in order to benefit from new technologies to meet those needs. While fusion technology is not at the deployment stage, the possible contributions of its successful development toward our policy goals are huge. Low-carbon, low risk generation technologies based on abundant resources would be major achievements for our societies. Fusion has the potential—but so far only the potential—to be a game-changer.
Those messages should be clearly communicated to politicians and the public.
In the 2011 World Energy Outlook fusion energy is not mentioned. Does that mean that the IEA doesn't count on the potential of fusion as a future energy source?
Nuclear fusion holds the promise of virtually inexhaustible, safe and emission-free energy. However the successful deployment of this technology still remains a long-term objective which will require sustained research and development efforts. Although significant work is ongoing in this area, IEA projections do not count on fusion reactors becoming available on a commercial basis within the time horizon considered in our World Energy Outlook.
Click here to order the 2011 World Energy Outlook.
After three solid days reviewing the design of one of the most critical elements of the tokamak's power supply system—the switching networks for ITER's coil power supplies and the fast discharge units that will protect the superconducting coils in case of a quench—Chairman Charles Neumeyer from the Princeton Plasma Physics Laboratory looks tired but satisfied. More than 60 participants including experts from Russia, Korea and China had convened at the ITER Headquarters for the meeting. The largest delegation with 17 engineers had flown in from Russia to present their work in person.
"The Russian Domestic Agency's contributions that were presented at this Preliminary Design Review are critical elements of the ITER power supply system," said Neumeyer. "In particular, the high current switches used for the switching network units and fast discharge units are unique, one-of-a-kind components, available only from the Efremov Institute in St. Petersburg, which has mastered this technology over several decades of development."
The switching networks are the "lighters" that start the ITER pulses: they will trigger the pulses in the circuits of the central solenoid and poloidal field coil numbers 1 and 6 for the initiation of the plasma. The fast discharge units are used to protect the superconducting coils in case of a quench (a sudden loss of superconductivity). Large steel resistor banks are inserted in the circuits during such an event to dissipate the energy stored in the coils.
Among them, the discharge units for ITER's powerful toroidal field coils will have to extract 41 GJ of stored energy. An extra building on site with a 50 x 60 metre footprint will accommodate the resistor banks. Finally, large aluminium water-cooled DC busbars connect the power converters to the magnets feeders, for a total length of roughly 10 kilometres including the circuits for the toroidal field and the poloidal field coils, the central solenoid, and the correction coils.
The Switching Network, Fast Discharge Units, DC Busbar & Instrumentation Procurement Arrangement was signed in March 2011 with the Russian Domestic Agency. "The package includes a large variety of components—most of them designed specifically for ITER. A broad R&D program has been carried out in the past years," explains Francesco Milani from the ITER Coil Power Supply Section and technical responsible officer for this package. "This meeting is therefore a key milestone in the procurement process."
The US ITER Project Office (USIPO) exhibited a new display at the recent annual meeting of the American Association for the Advancement of Science in Vancouver, Canada. The theme of the annual conference was "Flattening the World, Building a Global Knowledge Society." Thousands of scientists, science advocates, journalists, families, and students participated in the conference and viewed the exhibits.
The USIPO display featured enhanced digital capability, including plasma simulations in "port" windows, an electronic test-your-fusion-knowledge game, a small hands-on tokamak model, a touch screen for scrolling through project information and photos, and a new video highlighting the most recent US ITER progress and industry contributions. The exhibit was very popular with conference visitors, and offered an array of information on fusion energy, ITER progress, and US contributions to the project.
This Monday, ITER Director-General Osamu Motojima and the Head of the Chinese Domestic Agency Luo Delong signed the Procurement Agreement for the gas injection system that—in some respects—is the mechanical respirator of the ITER machine.
The gas injection system will provide the "initial fill" of the vacuum chamber prior to plasma initiation; it will puff gas into the chamber during the ramp-up phase; it will enable the control of plasma density during the flattop of plasma burn; and it will protect the divertor targets from discharges by injecting impurity gases. It also provide a system for the emergency shutdown of the machine.
The gas injection system will permit the injection of different gases simultaneously: three hydrogenic species; helium; and impurity gases (argon, neon and nitrogen). The required throughput of the system will be 400 Pa m3/ sec at peak—far beyond the fueling capabilities of existing fusion machines, according to So Maruyama, leader of ITER's Fuelling & Wall Conditioning Section. "The real challenge of designing the gas injection system, however, is the tritium compatibility required of all the components and the high magnetic fields that these components will have to face."
Gas arriving from the Tritium Plant will be distributed through a 200-metre-long manifold system that will supply a total of ten gas valve boxes of which four are distributed over the upper port level of the vacuum chamber. Six more gas valve boxes are placed in the lower port level of the chamber near the divertor. Gas injected at the upper port level moves along pipes that end between the blanket modules, where one- to two metre-long slots allow the gas to be uniformly distributed in the plasma chamber.
Extra care must be taken in the region near the divertor, where the ultra-hot plasma is likely to hit the divertor targets on a localized surface with extremely high heat-fluxes. Infrared cameras will be installed to monitor this area closely. In the case of an event, the lower port-level gas valve boxes can then be triggered to inject impurity gas or a gas mixture which will irradiate the heat.
The Chinese Domestic Agency for ITER has obtained ISO9001 certification, an internationally recognized standard for quality management.
At the accreditation ceremony held this week in Beijing, which was attended by ITER Director-General Osamu Motojima, the Vice President of the Chinese People's Political Consultative Conference and Minister of MOST (Ministry of Science and Technology), Wan Gang, commented: "This certification reflects ITER China's careful efforts in the establishment of a quality management system that meets the requirements of international mega-science projects like ITER and is a major milestone in the management and implementation of commitments to the project, in particular procurement packages."
Two other events were held in Chengdu this week: the first ITER China Forum and the Visiting Researcher Training, a three-day event with over 100 participants from domestic universities and institutes. Both events, explained Cao Jianlan, Vice Minister at MOST, are intended to create incentives for fusion: "As a developing country, China is not a front-runner in the development and research on fusion energy. Only with the participation in international mega-science projects like ITER can China strengthen its capabilities and contribute to the ultimate solution to mankind's future energy problems."
Present at both events, Director-General Motojima was delighted to see that ITER had attracted the attention of many departments, universities, and even industries. "In my view, the younger generation is the key to the success of ITER. I hope that more and more young Chinese students will be able to participate in the ITER Project."
ITER will use 100,000 kilometres of low-temperature, helium-cooled superconducting wire to generate the immense toroidal magnetic fields needed to confine the 150-million-degree Celsius plasma inside a tokamak machine. "By next September, US ITER will have its share of that wire ready," says Kevin Chan, a project engineer for the US ITER magnet systems.
The United States is responsible for 8 percent of the toroidal field coil conductor that the huge experimental fusion reactor requires; the rest of the conductor will be supplied by other ITER Members. Eighteen toroidal field magnets will encircle the inside walls of the ten-story-tall tokamak.
The US contribution translates into nine lengths of conductor packed with compacted niobium-tin wire, with each conductor length just under half a mile long. The internal-tin process superconducting wire is being made to ITER Organization specifications at Luvata Waterbury, Inc., in Waterbury, Connecticut, and Oxford Superconducting Technology, in Carteret, New Jersey.
"Before ITER, worldwide production was 20 metric tons of this wire a year," Chan said. "Now, Luvata and Oxford Superconducting Technology each are producing 5 metric tons a month." Between the two companies, nearly 200 jobs were added when the manufacturers were awarded US ITER contracts.
It is Chan's job to ensure that the toroidal field conductor is assembled with high quality, on time, and under cost. The engineer worked in the metals industry for 14 years before joining US ITER 2 years ago.
"When you produce toroidal field strands of wire, there is performance data and you look at what that tells you. The production data indicates trends," Chan explains. "The supplier is continually testing and sending us the data, and my responsibility is to look at the data. I actually watch the results of those tests. I can see, oh, something is changing. Something is not behaving as it should. Why is this? And one looks and tries to understand. That is how we work to optimize the product."
The ITER Organization sets out the testing requirements for every component made for ITER. "What I do," Chan explained, "is verify that each test has been passed. Each of the 1,422 pieces of this strand that make up the nine lengths of conductor has to be tested and must pass."
Chan said that when the finished conductor is delivered, the US ITER's commitment to that part of the project is complete. "It is high-value material, so the delivery is a big deal," he said. "Each conductor length is worth USD 5 million, and there are nine of them."
But making more than four miles' worth of wire is just the beginning of producing the finished conductor. The lengths of wire must be wound on hundreds of small spools and shipped to a cabling facility, New England Wire Technologies in New Hampshire, and later to an external casing, or jacketing, facility at High Performance Magnetics in Tallahassee, Florida. The assembly of the finished conductor is expected to take until 2016.
Assembling the cable in New Hampshire is a five-stage process. Initially, two superconducting strands and one copper strand are twisted together; next, three sets of strands are bound into a bundle; then, five of these bundles are twisted together. The resulting quintuple cord is arranged into a special configuration and becomes the subcable. Finally, to make the finished superconducting cable, six subcables are bound together around a central cooling spiral, which will permit the flow of liquid helium for cooling the wire when the magnet is energized.
The cable is then wound onto spools and sent to Tallahassee for an integration process where the cable lengths will be straightened and inserted into stainless steel tube sleeves, called jackets. These conductors are then wound onto four-metre diameter spools and shipped to France.
At the ITER site, the coil winders will reconfigure the conductors for installation. The conductors will be unwound and shaped into multiple layers called "double pancakes" to support the toroidal field magnets. The 760 metre-long cable will yield "regular double pancakes," and the 415 metre-long pieces will make "side double pancakes."
Each of the 18 toroidal field superconducting coils requires five regular double pancakes and two side double pancakes. In total, the toroidal field coils will weigh more than 6,500 tonnes, and will have a total magnetic energy of 41 gigajoules and a maximum magnetic field of 11.8 tesla.