Ever put your finger on the cold wall of your freezer? Then you must have noticed that it remains stuck and that it sometimes hurts to rip it free.
Atoms, molecules, particles are all captured by cold—and the more intense the cold, the more irresistible its holding power. When they come into contact with a very cold surface—say, a couple of Kelvins—even gas molecules turn solid, lose all energy and remain helplessly trapped.
This is why scientists use extreme cold to achieve extreme vacuum: a surface cooled to a very low temperature will eventually "suck in" almost every particle it comes into contact with. In a rather schematic way, this is the principle upon which cryopumps are based.
Cryopumps are essential for optimum plasma performance in ITER. They appear on the scene after mechanical pumps have evacuated most of the air molecules and impurities from the vacuum vessel, and brought the inside pressure to 1/10 000th that of the atmosphere.
The task entrusted to the eight "torus cryopumps" is to further reduce the pressure inside the vessel by another six orders of magnitude—these are conditions that one would encounter in the void of outer space.
Once a plasma has been generated, the cryopumps are back on stage: their job is now to extract the helium ash generated by the deuterium-tritium fusion reaction. "Helium particles are the most difficult to trap," explains Robert Pearce, ITER Vacuum Pumping Section Leader. "Even with surfaces at a temperature of 4.5 Kelvin (minus 268 °C) they retain enough energy to slip away."
One achieves efficient "helium pumping" by coating the cold surfaces of the cryopumps with a porous material that captures the particles in its microscopic mesh. Once caught, they do not have enough energy to escape.
A very fine carbon matrix is the best material for imprisoning helium particles. Regular charcoal was used in JET but it was later found that charcoal from finely ground coconut shells works even better—it has the right density and porosity (read article below). "We could use carbon fibre nanotubes ... but the European Union has bought enough coconuts to last us for the whole duration of ITER operation," says Robert.
Torus cryopumps will also give back part of what they have taken. Deuterium and tritium particles that have been sucked along with the helium ashes will be processed in the tritium plant and fed back to the plasma. "What is quite unique in ITER," says Robert, "is that at any one time, some of the eight torus cryopumps (typically four) will be pumping, while the others will be regenerating, thus keeping the fuel moving in a 600-second cycle."
This cycle of cooling, warming and pumping out the cryopumps is extremely challenging. "It is something that has never been done before," stresses Robert. Torus cryopumps in ITER will have to withstand some 50,000 of these cycles, with huge temperature gradients, and remain absolutely leak-tight.
In a couple of months, specialists from ITER Vacuum Pumping Section and from Forschungszentrum Karlsruhe (Germany) will have finalized the design of a real-size cryopump prototype, and tests could begin as early as a year and a half from now.
All together, the ITER torus cryopumps will deploy 88 square metres of cold surface—the equivalent of an average-size apartment.
Click here to read more...
|Next week, starting on Tuesday, 2 February, the conceptual design review (CDR) of the wall-mounted blanket modules will be held at the Château de Cadarache. This three-day review represents an important milestone for the design of the ITER blanket to help assess that the requirements of the system and its critical interfaces have been properly identified, and the proposed schedule is reasonable and achievable.
The blanket system provides a physical boundary for the plasma and contributes to the thermal and nuclear shielding of the vacuum vessel. The blanket system consists of 440 modular shielding elements known as blanket modules which are attached to the vessel. The modules consist of two major elements, a plasma-facing first wall panel mounted on a shield block actively cooled by water. As the blanket directly faces the hot plasma with a temperature exceeding that found in the core of the sun, it is one of the most critical and technically-challenging components in ITER.
Six ITER Members will contribute to the ITER blanket. Europe, China, Korea, Japan, Russia and the United States have worked closely with the ITER Blanket Section and within the Blanket Integrated Product Team framework, to prepare this review. Presenters from the Domestic Agencies and from the ITER Organization will describe the status of the blanket conceptual design following the recommendations of the 2007 ITER Design Review.
The review panel will be chaired by André Grosman of CEA and consists of independent experts, representatives of the procuring Domestic Agencies, and ITER Organization safety, quality assurance and technical integration representatives. The meeting's organizers are René Raffray (design developer) and Tommi Jokinen (review secretary).
The story of the negotiations that led to the choice of the ITER site and the establishment of the ITER Organization is a complex and fascinating one.
It is a story that has never been written ... the press releases that were issued after each round of negotiations gave only a faint idea of what was really going on between the delegations.
So it was a real privilege for the public of the 7th Inside ITER seminar last Thursday to hear the negotiation story told by three of its participants: Akko Maas, Senior Officer for Central Integration & Engineering; Hiroshi Matsumoto, Head of the Office of the Director-General; and Paul-Henry Tuinder, ITER Legal Advisor.
Recollecting the five years during which the ITER Organization went progressively "from concept to signature" between November 2001 and November 2006, all three speakers shared a common perception: it was harsh, it was often painful and sometimes unfair, but it was definitely worth the pain.
"Strong winds make strong trees," said Paul-Henry Tuinder and all agreed. Nothing resembling ITER had ever been attempted before and no scientific venture had ever had to compose with such political and diplomatic challenges.
By the end of the seminar, one couldn't help but feel "indebted" to the three guests seated at the table, and to all those who had endured the five-year diplomatic ordeal.
They had joined the negotiations as representatives of different nations entrusted with different agendas. Over five years, in a difficult international context, they managed to reach the only goal that mattered: the building of the international collaboration that the fusion community had been waiting for ... for more than 25 years.
RAMI stands for reliability, availability, maintainability and inspectability. It describes a process whose primary purpose is to make sure that all the systems of the ITER machine will be reliable during the operation phase and maintain their performance under operational conditions with the best possible availability. Failure of only one small function might result in the machine being halted for long periods of time and result in high costs for repairs and replacements. It is therefore important that every system undergoes a technical risk analysis to evaluate WHAT can go wrong, WHERE and WHEN, and to recommend spare components, back-up systems, increased frequency maintenance schedules, component standardization, systems design optimization, etc. to reduce the risk level of a main function breakdown to a minimum and to decrease the time to repair to a maximum.
Recently, representatives of the ITER Organization and the Domestic Agencies attended the 5th meeting of the RAMI & Standardization Board which was sponsored by the Chinese Domestic Agency and held in Xi'an, the home of the famous army of terracotta warriors buried more than 2,200 years ago by Qin Shi Huang, first emperor of China. Remote participants joined the meeting from Korea and Cadarache.
One of the goals of this 5th meeting was to review the progress made within the RAMI program. During 2009, ten analyses had been carried out and completed, bringing the total number of analyzed systems to 17. The results of these analyses have been put into optimization of the design and preparation of the testing and maintenance, spare parts policy, and operation procedures. The Board members expressed their opinion that the ITER RAMI approach is particularly effective for the reduction of potential technical risks of ITER subsystems, components, and even of the whole ITER machine. The Board members were very satisfied with the results obtained in 2009 which exceeded objectives. They underlined their support to the ITER RAMI program and agreed with the priorities proposed by the ITER Organization for this year: RAMI analysis of the divertor, blanket, diagnostics for basic plasma control and equipment protection, and access control and radiological monitoring.
The Board expressed appreciation for the considerable standardization activities that have been achieved and especially those related to the low and medium voltage electrical motors which are used to operate many ITER systems. The Board recommended maintaining the standardization of sensors/connectors and electrical distribution components as a high priority.
Finally the board recommended that the ITER Organization develops and maintains, in collaboration with Domestic Agencies, a database gathering all the existing data related to the failure frequency (rate) of components used in fusion devices.
The Board concluded its 5th meeting with a renewed commitment to continue supporting the RAMI and standardization programs at ITER to ensure that ITER meets its operational objectives.
Tests on a machine that mimics a planet's magnetic field show that it may offer "an alternative path to taming nuclear fusion for power generation," the Massachusetts Institute of Technology (MIT) wrote in a press release (see below) this week announcing news published in the latest issue of Nature Physics.
The new results published there come from an experimental fusion reactor at the Plasma Science and Fusion Centre on the MIT campus, inspired by observations from space made by satellites. Called the Levitated Dipole Experiment, or LDX, a joint project of MIT and Columbia University, it uses a half-tonne donut-shaped magnet about the size and shape of a large truck tire, made of superconducting wire coiled inside a stainless steel vessel. This magnet is suspended by a powerful electromagnetic field, and is used to control the motion of the 10-million-degree-hot electrically charged gas, or plasma, contained within its 16-foot-diameter outer chamber.
Our experiment was inspired by observations of planetary magnetospheres made by interplanetary spacecraft," says MIT senior scientist Jay Kesner. "Planets like Earth and Jupiter can accumulate hot ionized matter with their dipole field even at high pressure," says the physicist. A plasma effect known as turbulent inward pinch.
Read the MIT press release here
There are many mansions in the house of the atom and in the course of her professional life Françoise Flament has visited them all. Be it fission or inertial fusion, nuclear testing or installation cleaning and dismantling, magnetic fusion or isotope separation—Françoise has been involved in some of the greatest nuclear research ventures of the past 25 years.
"What attracted me to the nuclear world was its diversity," says ITER's Head of Procurement & Contracts. "I wasn't expecting it when I joined CEA in 1983, and I found that multi-faceted reality totally fascinating."
A Law and Economics major, Françoise was looking for a job with "a proactive legal and business dimension," a job in which rules, regulations and organization would serve a greater purpose. She found it first at SILVA, a CEA project that experimented with laser isotope separation, and then in CEA's Department of Military Applications (DAM) which she joined in 1986.
At DAM, Francoise dealt with procurement, business and financial activities at different levels of the organization. In 1996, an offer to work as Finance and Business Director for a CEA subsidiary that had obtained a contract to cleanup nuclear installations in Hanford, in the American Northwest, provided the opportunity for an international experience.
At Hanford, Françoise was soon put in charge of the project control activities. "Project control," she says, "is a management technique as well as a culture that is ingrained in American companies."
Hanford had provided Françoise with strong experience in project management. In France, the Laser Mégajoule (LMJ) project had just been launched and was eager to use her newly-acquired competence to "modernize project management techniques and reflect on industrial strategy."
"Beyond business and project management, what I love best is building and organizing a team as an efficient task force to support projects ..." She did it at LMJ, where she worked for eight years as Deputy Project Manager, and she's doing it now, at ITER, which she joined in winter of 2007.
The LMJ experience certainly helped to prepare for the challenges of ITER. "Essentially, it is the experience of constructing a large science facility that matters. You have to consider every contract as a project per se, something you approach with a vision."
ITER, however, offers something more—the deep multicultural experience that comes with working with a "task force" composed of eight different nationalities—something, says Françoise "that teaches humility, communication and understanding."
Fusion experts have been asked to give their view on fusion research to the Italian Parliament on Friday, 22 January. According to the announcement on the Senate's webpage, "Fusion could radically change the way in which we produce energy and consequently the way we live."
One year ago the Senate Committees on Scientific Research (chaired by senator Guido Possa) and on Industry (chaired by senator Cesare Cursi) had jointly initiated a Parliamentary inquiry on fusion. On Friday, 22 January, they presented the results and invited on this occasion a number of speakers to highlight the topic from a technical and strategic point of view. There was a general consensus that the inquiry was performed in an excellent and professional way. Francesco Romanelli, Director of JET, comments: "The senate wanted to know where we are in fusion research. They asked me to give a presentation on the progress of fusion from JET to ITER. Overall it is important to underline that the attitude within the Senate Committees is favourable to fusion energy which goes in line with the Italian plans to construct new fission power plants as soon as possible."
There was a "back to school" feeling in the air last Monday at the Manosque International School, as 63 kindergarten children and 15 teachers moved from temporary premises into their brand new classrooms.
"Today is a very important date in our development," said Director Jean-Paul Clément. Construction of the Manosque International School began in the summer of 2008 and the first section of the buildings was inaugurated on 14 September of the following year.
With the opening of the kindergarten facility and its dedicated playground, the installation of the elementary school is now complete. Junior and high school students ("collège" and "lycée")—presently hosted at the nearby Lycée des Iscles—will move this September.
By then, the school's entire campus, including a cultural centre and a sports centre, will be fully operational. While pursuing its educational mission, the Manosque International School will contribute to building, in Director Clément's words, "a new concept of international citizenship."
A new collective noun had to be invented on Friday to describe the meeting between CEA Cadarache and ITER communicators: a gaggle of geese, a swarm of bees, a pod of whales and now a clutch of communicators.
The communication representatives of all CEA institutes get together twice each year to swap information, best practice and to come up with new projects. The most recent meeting was held in the ITER Headquarters and was the perfect opportunity for the ITER Office of Communication to learn about CEA activity and work out ways of collaborating. Thanks to Guy Brunel, Head of Communication at CEA Cadarache, for organizing the event.