More than 1,500 scientific experts met in Daejeon, Korea last week to discuss nuclear fusion as a source of energy. This 23rd IAEA Fusion Energy Conference (FEC) brought together the largest group of physicists working in the field to date. "I am convinced that it will be recorded as a landmark conference addressing the environmental problems of our planet," ITER Director-General, Osamu Motojima, said in his opening remarks. "Here in Daejeon we are witnessing the integration of physics and engineering that is necessary for the development of new energy technologies. There is no longer any doubt that fusion energy is an achievable goal. The dream is alive!"
The IAEA FEC, called by some the "Olympics of Fusion Energy," is the most renowned international conference on a fusion scientist's calendar. Held biennially, with scientists, engineers and policymakers attending from all around the globe, experience and future steps are shared. "Thanks to hard work, the world successfully reached the experiment level," IAEA Deputy Director-General Werner Burkart said in his opening speech. "However, we need to go beyond what we have achieved. We have to secure the commercial validity of fusion by 2040-2050 and I believe that we can do so. Fusion energy is the future of humankind."
In his keynote address, Korea's Prime Minister Kim Hwang-Sik stated that "if nuclear fusion energy comes into commercial use, the challenge over energy shortages will be removed. If this happens, governments will be able to save money and make investments in other humanitarian areas." Gyung-Su Lee, Chairman of the International Fusion Research Council, added: "This event clearly opened the ITER era and stirred the passion for fusion energy development."
The European Domestic Agency for ITER, Fusion for Energy
(F4E), has signed a contract for the supply of seven sectors of the ITER vacuum vessel with the European consortium AMW (Ansaldo Nucleare S.p.A, Mangiarotti S.p.A and Walter Tosto S.p.A). The contract, expected to run for six years, is worth almost EUR 300 million—the biggest single work package of Europe's contribution to ITER.
The complexity of the ITER vacuum vessel, its size, the amount of welding required and the degree of precision that is needed to build the component, brand this contract as one of the most important and technologically challenging of the ITER Project. The in-wall shielding bolted inside the vessel's walls will be delivered by India and ports to be welded on the D-shape sectors will be manufactured by Russia and Korea. Two other sectors of the vacuum vessel will be supplied by Korea.
The ITER vacuum vessel is located inside the cryostat of the ITER device and its basic function is to operate as the chamber that hosts the fusion reaction. Within this torus-shaped vessel, plasma particles collide and release energy without touching any of its walls due to the process of magnetic confinement. The vacuum vessel is composed of nine sectors made of thick special grade stainless steel. Each sector is 13 metres high, 6.5 metres wide and 6.3 metres deep. All of the sectors are similar and are built with double-walls containing the bolted-on shielded plates with a pressured interspace which combine to attenuate the thermonuclear flux so as to avoid overheating of the super conducting coils.
The weight of each sector is approximately 500 tonnes and the weight of the entire component, when welded together, will reach an impressive total of 5,000 tonnes (nearly the weight of the Eiffel Tower). The ITER vacuum vessel will be twice as big and sixteen times heavier than in any previous tokamak. Its double-wall structure is designed to provide a high quality vacuum for the plasma as well as the first confinement barrier for tritium, forming an important part of safety of the ITER device. The vacuum vessel will operate at a temperature close to 100 °C and at a nominal water pressure in the inter-space of 11 atmospheres, equivalent to the underwater pressure at 110 metres. The heat of the ITER fusion reactions is removed by the water in the vessel's cooling loops, while the decay heat may also be removed by natural circulation.
The complex doughnut-shape container will be manufactured and put together in segments, following a significant amount of electron beam welding carried out in the largest vacuum chamber in Europe. The ports and segments have to be joined together with unprecedented accuracy for this size of vessel. It is estimated that the total amount of welded joints will add up to approximately 14 km. Europe's proven track record in R&D—with prototypes in ultrasonic testing inspection technology, weld distortion and analysis (including electron beam welding)—and its world class facilities in fabrication technology were essential in undertaking the commitment to provide seven out of the nine sectors of the ITER vacuum vessel.
With the impressions of the IAEA conference in Korea still fresh in his mind, ITER Director-General Osamu Motojima has just arrived in China where he is meeting Minister Wan Gang and Vice Minister Cao Jianlin of the Chinese Ministry of Science and Technology. This trip is part of a series of visits aimed at reinforcing collaboration with the ITER Members.
In September he visited the Indian Domestic Agency in Ahmedabad, followed by a meeting with the US Secretary of Energy, Steven Chu, in Washington. From there, he went on to Madrid to meet with the Spanish Minister for Science and Innovation, Cristina Garmendia. Motojima thanked her for supporting the ITER Project over the first six months of the year when Spain held the presidency of the Council of the European Union, and he reported on the progress made since.
Before heading off to Korea to attend the IAEA meeting, Motojima travelled to Russia, where, at the Kurchatov Institute in Moscow, he met the Chairman of the ITER Council, Academician Yvgeny Velikov, and the Head of the Russian Delegation to the ITER Council, Igor Borovkov. In a special session with the staff of the Domestic Agency located on the premises of the famous Institute, the Director-General presented the current status of the ITER Project.
He continued his world-spanning round trip from Moscow to Japan where he held bilateral talks with Japan's Deputy Minister Moriguchi and Vice-Minister Shimizu before he discussed recent issues with the management of the Domestic Agency at the JAEA Tokyo Office, representatives from Japanese industry and universities. "As the ITER Project seeks unanimous consent in its decision process," Motojima recently stated in an interview, 'close cooperation between the Members is essential."
A recently held meeting of the Integrated Product Team for ITER's toroidal field coils highlighted some of the manufacturing milestones reached for the coil structures and the coils themselves. The Chinese Domestic Agency presented the status of their procurement process for the magnet supports for which the call for tender has been launched.
Three contracts are already in place for the fabrication of a full scale prototype for the radial plates. The toroidal field coils use a conductor with a circular outer section that is contained in grooves in so-called "radial plates." There is one radial plate for each double pancake and the conductor is contained in grooves on each side. The radial plates measure 8.7 m x 13.8 m and weigh 5.5 tonnes each. Different manufacturing routes are utilized so that the Domestic Agencies can select the best solution from both the technical and cost point of view before launching into series production.
The manufacturing routes are:
- hot rolled plates, forgings and powder hipped plates for the raw material;
- narrow gap TIG welding, electron beam welding and laser welding for the assembly of the radial plate segments;
- finish machining either before or after assembly and welding of the segments, eventually with a portal machine along the entire perimeter of the radial plate.
One contract has been placed with the company SIMIC S.p.A. in Italy, the second contract is with the company CNIM in France and the third one is with the company Toshiba in Japan. Regarding the winding for the toroidal field double pancakes, the company Toshiba is completing the optimization of the winding parameters with a dummy conductor and will start the fabrication of a 1/3rd scale double pancake winding in a few weeks. This double pancake winding will then be utilized for a vacuum pressure impregnation trial.
The name may not be familiar, but the picture certainly is: this is the Rion-Antirion Bridge which spans the Gulf of Corinth and connects the Peloponnesus to mainland Greece.
Located in a highly seismic zone and resting on a fragile seabed of clay, sand and silt, this 2.9 km structure is widely considered as an engineering feat. It is designed to withstand wind speeds of more than 250 kilometres per hour, an earthquake of magnitude 7 on the Richter scale and the impact of a 180,000-tonne tanker.
The man who designed the foundation system for the Rion-Antirion Bridge was on the ITER platform last week and will be seen a lot around the Tokamak Pit—the "Seismic Isolation Pit," as it should be referred to—in the coming months. His name is Alain Pecker; he is a veteran "geotechnical engineer" who, for the past 30 years, has worked on "integrating the nature of the geological substratum into the design basis of structures and installations"—several of them nuclear.
Pecker's job, as an expert for the ITER Organization, will be to confirm and refine the geological surveys and sampling that has been conducted on the platform since the site was chosen to host the installation.
As excavation in the Seismic Pit is reaching the bedrock, some 20 metres deep, the expert will have a much better "view" of the pit's rock slopes and of the substratum. "Some 360,000 tonnes will rest on this bottom," says Pecker. "Better make sure you know precisely what it is made of. Surprises are always possible."
Surprises, in the Seismic Pit's substratum, could come in the form of "karsts"—holes large and small that are bored by water erosion in the depths of the limestone bedrock and that the initial surveys could have missed.
Dealing with karsts, however, is routine work for a geotechnical engineer: whatever their size, and provided they are detected, the holes can be injected with concrete.
In order to locate karsts and other possible geological "accidents", like fissures, faults and other anomalies, a systematic survey will be conducted on the 130-by-90-metre zone of the pit's bottom and faces. In order to cover the position of all seismic pads
, drillings will be carried out every 4 to 5 metres and up to 5 metres deep.
A radar survey will also be conducted, providing data for a 3D rendering of the substratum.
This whole process could take two to three months. Then, when the depths have been mapped and the possible "holes" filled, it will be time to pour the "first concrete" of the Tokamak Complex basemat—a major milestone in the history of ITER.
The measurement of the neutron emission stemming from the fusion reaction is a very important diagnostic because it is directly related to measuring the fusion power. A typical neutron counter is the fission chamber. This detector, originally developed as a monitor for fission reactors, has been applied for decades on various large fusion devices like JET in Europe, JT60 in Japan and TFTR in USA.
A micro fission chamber is a ionization chamber, i.e., a small cylinder containing argon gas and a tiny amount of uranium (235U). As a neutron hits the uranium, a fission event will be generated and a pulsed signal triggered which can be translated into the amount of power generated. In ITER, the pencil size monitors will be located inside the vacuum vessel behind the blanket modules.
Recently, the conceptual design review for the ITER micro fission chamber, an effort lead by Luciano Bertalot and Anna Encheva, was concluded successfully with no "category 1" chits (no identified showstoppers). "The stringent quality control on ITER design enforced by the conceptual design review panel makes such events rare and highlights the outstanding teamwork within the ITER Project," a relieved Anna Encheva commented the outcome of the two-day review.
Special thanks to Anna Encheva and Luciano Bertalot for their contribution to this article.
During the 2010 Fusion Energy Conference, held in Daejeon, Korea this week, the Nuclear Fusion Prize was presented to the 2009 and 2010 winners on 11 October 2010.
The prize winner for 2009 is Steve Sabbagh from the Department of Applied Physics and Applied Mathematics, Columbia University, New York (US). He received the award as the lead author of a landmark paper which reports record parameters of beta in a large spherical torus plasma, and presents a thorough investigation of the physics of resistive wall mode (RWM) instability. The paper makes a significant contribution to the critical topic of RWM stabilization.
The recipient of the 2010 award is John Rice, principal research scientist on the Alcator Project at MIT's Plasma Science and Fusion Center, Cambridge, Massachusetts (US), as the lead author of a seminal paper that analyzes results across a range of machines in order to develop a universal scaling that can be used to predict intrinsic rotation. The timeliness of this paper is the anticipated applicability of this scaling to ITER.
The Nuclear Fusion Prize is awarded annually to recognize outstanding work published in the journal