Leading scientists and engineers from the ITER Members' fusion communities assembled at the Cadarache Château this week to review the progress that the project is making in key areas of science and technology. Led by their Chair, Prof Yuanxi Wan of China, and Vice-Chair, Prof Minh Quang Tran of the European Union, the members and experts of the Science and Technology Advisory Committee (STAC) dealt with a series of "Charges," or action topics, which had been issued by the ITER Council at its seventh meeting in November 2010.
These action topics included reviews of the technical content of the project's ongoing cost containment activities, progress on the development of the radiofrequency heating systems and of the in-vessel coil systems, results of analysis of the ITER reference plasma scenarios, and the status of R&D on the ITER Disruption Mitigation System.
The ITER Organization's contribution was led by Director-General Osamu Motojima, who gave a comprehensive presentation reviewing the current status of the project and highlighting significant areas of recent progress. This was followed by a series of detailed presentations by ITER Organization staff responding to the Council's Charges. Two additional issues of particular interest to the STAC members were presented: reports on the progress of the ITER schedule, and the status of R&D on the superconductor under development for the central solenoid.
In its response to ITER management, the STAC encouraged the ITER Organization to pursue measures to deal with the potential delays which have emerged in the construction schedule. The STAC also supported the ITER management's proposals to resolve the cause of unexpected results in recent performance measurements of samples of the central solenoid superconductor.
The STAC also received updates on a variety of issues that had been discussed at earlier meetings, such as design and R&D activities supporting the development of the ITER diagnostic systems, aspects of the ITER Research Plan, the final specification of toroidal field ripple in ITER, and the possibility of using the in-vessel coil systems to control resistive wall modes and correct error fields.
In a series of breakout sessions, STAC members and experts took the opportunity to discuss several of these topics in greater depth with members of the ITER Organization. In the course of these discussions, STAC participants provided valuable feedback on areas where further analysis or R&D could strengthen the basis for performance projections to ITER and reduce uncertainties in meeting system requirements. STAC gave a comprehensive summary of its main recommendations in its response to ITER management on the third day of the meeting.
Further details of these recommendations will be provided in the final report which will be presented to the eighth meeting of the ITER Council in Aomori, Japan, on 14-15 June.
A new technique is on the table for the suppression of runaway electrons - those particles that are accelerated nearly to the speed of light during a plasma disruption and that can cause significant damage to the interior surfaces of the tokamak if left unchecked.
Presented to the ITER Council Science and Technology Advisory Committee this week by Sergei Putvinski, Senior Scientific Officer for Energetic Particle Physics, the new technique proposes to shoot very sharp and dense gas jets into the centre of the plasma to shake out runaway electrons before they build up.
"Runaway electrons build up exponentially during current quench over 20-50 milliseconds (ms)," explains Sergei. "We need a mitigation technique that intervenes in less than 5 ms to prevent this 'avalanche' effect. We need to draw quickly, and shoot continuously," he says with a smile. "Basically, the new technique is like shooting blanks into the ITER plasma."
Called a DMS gun (for Disruption Mitigation System gun), the proposed fast-gas injector consists of small gas tanks that would deliver high-pressure gas jets repetitively into the ITER plasma. Positioned in ports around the ITER torus, these injectors would aim to trigger secondary perturbations in nascent runaway electron currents in order to disperse them before the avalanche multiplies relativistic electrons. This concept for runaway electron suppression was developed collaboratively over the last year between the ITER Organization and scientists at the Princeton Plasma Physics Laboratory.
R&D is in progress to test the scheme in Tore Supra, ASDEX Upgrade and the T-10 Tokamak and results are expected in 2011. If these experiments are successful, then ITER will need fast gas delivery systems: either ultra fast gas valves capable of opening in 1-2 ms, or small, pre-loaded gas cartridges that release gas through a rupture disk. "The ultra-fast valve capable of withstanding the harsh ITER environment is something that does not yet exist, but I am confident that it can be developed," says Sergei.
The new fast-gas technique appears to offer significant advantages over another proposed mitigation strategy for runaway electrons that consists of injecting massive amounts of gas to collide with the runaway electrons and slow them down. "This collisional technique appears to require too much gas," explains Sergei. "Too much for our pumping systems, that's for sure. Such massive amounts of gas would also increase the electromagnetic loads on conducting structures." The new technique, in contrast, could potentially decrease the amount of required gas by a factor of 10, according to calculations and mathematical modelling.
Late May, experiments will begin at Tore Supra with a prototype DMS gun cartridge system that was built to test the rapidity of the release system. Termed the FIRE Experiment, Tore Supra engineers built an assembly of 18 cartridges based on the ITER design. "As a device, we know it works," says Sergei. "We now must test whether it works in runaway electron suppression."
The ITER Tokamak has been designed to test a variety of plasma regimes and operational scenarios. Physicists expect that approximately 3 percent of ITER's plasma shots will quench because of plasma disruptions.
The ITER vacuum vessel and in-vessel components have been designed mechanically to withstand about 3,000 disruptions of the course of their lifetime. However, high energy loads during disruption can reduce life time of plasma-facing components such as divertor targets and first wall panels. Effective disruption mitigation strategies for ITER must be developed within the next three years, prior to full-scale operation.
Some fifteen years from now, when ITER begins burning the actual fusion fuels, helium will play a crucial role: it is helium atoms resulting from the collision of deuterium and tritium nuclei that will keep the fire burning - what scientists call "alpha heating."
For the moment, as ITER buildings are being constructed, the role played by helium is more modest but valuable nonetheless: helium fills the suspended balloon used in the aerial photo surveys of the platform works...
Aerial surveys began in 2003 when CEA-Cadarache was drafting an early bid to host ITER, and have been conducted systematically on the ITER site since 2007.
Surveys provide photographic material for both technical and communication purposes: "We need these views to follow the evolution of the work site," says Bruno Couturier from Agence Iter France, who supervised most of the campaigns.
Photographs taken from the balloon hovering at 70 to 100 metres above ground have great communication value: they give the public a unique perception of the size and spread of the ITER project.
As much as they owe to state-of-the art photo equipment, none of the thousands of high-resolution images that were taken since 2007 could have been produced without a bit - and sometimes a lot - of resourcefulness and ingenuity.
The challenge, even with a theoretically stable tethered balloon, is "to keep the horizon level in the camera's viewfinder," says Cyril Becquart, both the founder of Altivue, the Marseille-based company that Agence Iter France contracted three years ago, and the operator of the balloon.
In order to achieve camera stability and motion, Becquart devised a system of servo-motors, tiny belts and cogwheels that control the camera's support cradle and can adjust both the shooting angle and the zoom's focal length.
A light webcam, attached to the still-camera's viewfinder and connected to the operator's control screen by wireless, provides a clear view of what the camera will be shooting. Becquart radio-controls and operates his camera from the ground as he would a model aircraft.
In three years, Agence Iter France has commissioned some fifteen aerial photography surveys of the platform. Last month, Spie-Batignolles, the company heading the consortium that is constructing the PF Coils Building, began its own campaigns through Altivue.
The new harvest of aerial photographs will add to the old one and form what Bruno Couturier calls "the visual memory of the project," both for the construction professionals and for the general public.
The last time Jooh-Hyun Lee visited the ITER site, some five years ago, the most conspicuous feature on the platform was a flagpole marking the location of the future ITER tokamak.
This Friday, the President of the Korean Institute of Energy Technology Evaluation and Planning (KETEP) was back at ITER to meet Director-General Osamu Motojima, "look at construction progress, and encourage the Korean staff working here."
KETEP is an agency that was established two years ago by the Korean government for the purpose of developing R & D strategies and programs in innovative energy technologies.
President Jooh-Hyun Lee considers fusion as a "realistic energy source for the future" and discussed "concrete ways of supporting ITER" with Director-General Motojima.
When you ask Joëlle Elbez-Uzan why she studied engineering, she replies that she has always liked science. Asking "why" and "how" is what characterized her as a child and nothing has changed since. Passion for science and curiosity about how things work are still important drivers in her daily life.
And her daily life is not made up of peace and quiet because—apart from being the mother of three energetic boys aged 8, 11 and 12—she is also Section Leader of the ITER Safety Design and Integration Section (CIE Directorate).
Joëlle studied engineering in Lille where she specialized in instrumentation and measurement. Work done for one of her projects, a comparative study between all forms of energy, resulted in her supporting nuclear energy. "I was impressed by how controlled and regulated the environment is in which a nuclear plants operate," says Joëlle, "certainly compared to the more traditional energies."
After her studies, Joëlle returned to her native region where she worked for some years in nuclear safety management for a subsidiary of Areva and for SGS Qualitest, travelling both around France and worldwide. She then decided she wanted to broaden her scope and work within a French Installation Nucléaire de Base (INB), so when the CEA Cadarache contacted her in 1996 to work as nuclear safety support for some (and later all) of their installations, she gladly accepted. Among her many responsibilities, she worked on the Jules Horowitz reactor where she was in charge of safety of the design of the installation.
A new chapter in her career began in 2001 when she was asked to write the safety options report for ITER. This report summed up all the potential risks of the ITER machine and their corresponding safety options, and also justified the choice of the Cadarache site from a seismic point of view. Based upon this report, the French Nuclear Authority ASN validated Cadarache as one of the candidates for the ITER project; the next step was for Agence Iter France to develop the nuclear safety plan for ITER, with Joëlle, of course, playing an instrumental role.
In 2009 she joined the ITER Organization as one of the driving forces behind the ITER licensing process and the primary contact with the French nuclear safety authorities. Joëlle currently heads the team responsible for the Public Enquiry and the technical examination with the regulators. The Public Enquiry—a major milestone in the ITER licensing process—is planned to start shortly. As one of the people within the ITER Organization with the best knowledge of every safety aspect of the ITER project, she will also head the newly created Licensing Office within the SQS Department, responsible for the management of nuclear safety issues in view of obtaining the "Decree for Authorization of Creation," the final go-ahead for the operation of the ITER machine.
"An installation like ITER has never been built before, and this is why we've had to go way beyond all known and possible nuclear safety scenarios normally applying to a nuclear installation in order to prove that ITER is safe," explains Joëlle. "We've had to submit extremely thorough and robust studies to the authorities showing the possible safety or environmental impact of an accident at ITER under pessimistic conditions. This has been a long process, but the ITER Organization is fully committed to making sure that all safety concerns are taken into account into the design."
Their names are Neils, Sander, Gonzalo, Carla and Marta, and they have two things in common. First, they had the occasion to visit the ITER worksite with their schools this week. Second, they are part of schools that have been coming, every year, since the beginning of the project.
On 9 May, 20 students from the Polytechnical University of Catalunya visited the worksite and received a technical presentation of the ITER project to complement the 45 hours of coursework that they had accomplished on fusion during the semester.
The following day, a group of younger students ranging in age from 15 to 17 arrived from Gertrudis College in the Netherlands for a visit of the ITER site as well as the Tore Supra fusion facility at CEA.
Akko Maas, Senior Officer of the ITER Organization and a former student of Gertrudis College, enjoyed giving the youngsters a general explanation of the scientific and technical challenges of ITER.
According to the teachers of both establishments, these yearly visits are one of the best ways to keep track of the reality of construction progress.
See you next year, then!