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ITER NEWSLINE 248
The ITER Organization and the Spanish company Equipos Nucleares S.A. (ENSA) signed the contract for the welding of the ITER machine's nine vacuum vessel sectors and 54 port structures on Friday, 30 November 2012.
In addition to on-site welding and testing operations, the contract—which is worth EUR 74.5 million—includes the development of specialized welding and testing tools. More than 150 people, including highly skilled welding and testing personnel, are expected to be involved in the task to complete the field joint welding and testing on the ITER site over a time-span of four years.
ITER's vacuum vessel is a torus-shaped, double-walled structure made out of 60-mm-thick, ITER-grade austenitic stainless steel. The vacuum vessel will be manufactured in nine sectors (two by Korea and seven by Europe) and delivered to the ITER site. The nine vacuum vessel sectors will be sub-assembled with thermal shielding and toroidal field magnet coils before being positioned in the machine pit by crane.
Each vacuum vessel sector must be aligned and welded to the other sectors using a Narrow Gap TIG (Tungsten Inert Gas) welding process. Welding will proceed by triplets: three sectors will be welded together to form a triplet; three triplets will then be aligned and welded together quasi-simultaneously.
The nine sectors will be connected via inner and outer splice plates. These will be custom machined to accommodate dimensional differences between the vacuum vessel sectors and to facilitate their relative alignment. The splice plates will also allow access between the sectors prior to welding in order to first connect the joints between the silver-coated thermal shields that surround each vacuum vessel sector.
The nominal width of the splice plates is 160 mm on the inner shell and 100 mm on the outer shell.
In the ITER machine, because the thermal shielding completely restricts access to the outer shell of the vacuum vessel during assembly, it will only be possible to access and weld these joints from one side, whereas normally such welding would be performed from both sides.
Access is so difficult that narrow welding torches will have to be developed. Robots will deploy the torches in areas where man-access is not possible.
It is estimated that welding operations for the ITER vacuum vessel will require the manpower of 150 specialists working in two daily shifts over a period of four years. At the end of welding operations—in addition to non-destructive examination technologies such as radiography and ultrasound performed by ENSA and its sub-contractors—the ITER Organization will perform vacuum leak testing and pressure testing. All welding and testing work will be independently monitored and approved on behalf of the French Nuclear Regulator by an Agreed Notified Body.
The work on the vacuum vessel and the ports will be done in accordance with RCC-MR (Design and Construction Rules for Mechanical Components of Nuclear Installations, 2007) and the ITER Vacuum Handbook.
ENSA is an industrial manufacturer with vast experience in the nuclear power sector. "We are very proud that the ITER Organization has awarded us this contract," said the ENSA Managing Director Rafael Triviño on the occasion of the contract signature. "We are grateful for this confidence placed in us and we are very pleased to have the opportunity to participate in this challenging and highly technological project that we hope will be followed by other significant collaboration opportunities in the field of nuclear fusion."
For ITER Director-General Osamu Motojima, the signing of the welding contract was a "landmark," representing as it does the first contract signed for the assembly of the ITER Tokamak.
For the electronic version of the ITER Press Release press here.
KSTAR (Korea Superconducting Tokamak Advanced Research), a tokamak in operation since 2008 in Daejeon, South Korea.
The KSTAR and ITER control systems share some key similarities (e.g., EPICS as middleware for tokamak control and operation), making KSTAR a natural fit for evaluating and validating ITER CODAC technologies.
Operating under a Memorandum of Understanding between ITER and KSTAR, signed in 2010, the KSTAR control team has implemented a duplication of the fuel control system and a part of the plasma control system using CODAC technologies (standardized hardware and CODAC Core System) over the past 24 months. On 26 July, a first test was successfully executed by injecting deuterium gas into the vacuum vessel based on pre-configured waveforms from the plasma control system.
The project was successfully concluded on 21 November with a demonstration of the real-time feedback control of the KSTAR plasma density, with ITER Organization CODAC staff joining the demonstration.
The algorithm used for calculating the density from the microwave interferometer diagnostic (sampled at 10 kHz) and computing the control command was implemented on a computer using ATCA form factor, the CODAC standard real-time operating system (RedHat Linux with MRG-R) and the MARTe real-time framework originally developed at JET.
The control demand was transferred over CODAC real-time network (10 Gbps Ethernet) to the fuel controller at 10 kHz and finally applied to the piezo control valve at 10 kHz. The plot shows the key measured signal and applied commands, such as required plasma density, piezo valve command and the resulting measured plasma density. The feedback loop was switched on at 1.2 sec and switched off at 5.0 sec.
The resulting performance is in excellent agreement with KSTAR native control system, confirming that the technologies adopted or being considered for ITER CODAC are delivering excellent performance in the real-life environment of an operational tokamak.
"ITER—Step into the power of future," was the subject of a conference held on 20 November at the Russian Domestic Agency within the framework of the 55th Scientific Conference of the Moscow Physical and Technical Institute (MPhTI).
In his introductory speech, Academician Evgeny Velikhov, president of the Kurchatov Institute and former Chair of the ITER Council, said, "ITER is the basic technological platform that can become the foundation for other projects." He shared the recent news of the signature of the official decree permitting the construction of thermonuclear facility—a major event for the project.
Young scientist and technicians were the focus of one session, whose discussions centred on the involvement of young people in the ITER project and the stimulation and the technological renewal of available training programs.
Answering the question about practical training of young specialists, Anatoly Krasilnikov, head of the Russian Domestic Agency, reported that "it is planned to pursue training in order to prepare Russian specialists for work at the ITER Organization."
Discussion participants noted the necessity of organizing targeted finance to support training of the qualified personnel in Russia and to stimulate their employment. They also supported the idea of sending young scientists to leading foreign scientific centres for further training. "Russia shall participate in the ITER project not only by investing equipment, but also by delegating qualified specialists," he noted.
The most important tasks ahead are to enhance the prestige of work done for the ITER Project, to sufficiently modernize the material basis necessary to perform thermonuclear research in Russia, and to develop a targeted program in order to train Russian personnel for ITER and for fusion.
What can you do with a neutron? In a conventional fission reactor, relatively slow neutrons ("thermal neutrons") split heavy nuclei such as enriched uranium to generate large amounts of energy, on the order of 200 MeV per reaction. In a fusion reactor, the fusion of deuterium and tritium nuclei generates very fast and very energetic neutrons that impact and heat the plasma-facing wall.
If the two nuclear processes could be combined in a hybrid fusion-fission reactor, the fast fusion neutrons could be used to split fertile material such as thorium, natural uranium or spent nuclear fuel contained in the reactor's wall.
The idea of such hybrid reactors has been around for more than fifty years but remained largely unexplored until recently, when the steady state production of fusion neutrons entered the realm of the possible with ITER.
One ardent advocate of fusion-fission hybrids is Academician Evgeny Velikhov, whom ITER Director-General Osamu Motojima introduced at last Wednesday's Inside ITER conference as the "Godfather of ITER."
Velikhov, who made the first proposition of an ITER-like device in 1975, considers that "nuclear power is absolutely necessary to fulfil mankind's goals of development." He acknowledges, however, that nuclear power is presently "in very bad shape" because of a strained relationship with public opinion. Would another major accident occur, he considers, it would be the end of the nuclear industry worldwide.
Pure nuclear fusion of the type that ITER hopes to pave the way to is, of course, a beautiful option . But it will be some time before the first kilowatts of "fusion electricity" can be fed to the grid. And time is running short to provide for mankind's growing needs...
"We need a nuclear power Renaissance," advocates the man without whom ITER would not exist. For reasons he developed in his presentation, the key to this Renaissance in his opinion lies in hybrid, "vital-risk free" fusion-fission reactors.
Academician Velikhov goes as far as to dub this new avenue of research and development "Green Nuclear Power."
A hybrid reactor would have a fusion reactor at its core providing an intense neutron flux that, instead of just heating the water circulating in the plasma-facing wall, would generate high energy fission reactions in the "fertile" material contained in the surrounding blanket (43 MeV in the case of uranium 238; 25 MeV in that of thorium 232).
Velikhov's favoured solution is that of the Molten Salt Hybrid Tokamak (MSHT), in which fertile material would circulate in the blanket modules in the form of liquefied uranium or thorium salt at a temperature in the range of 500 °C.
MSHT's attractions are many: the fusion core does not need to achieve Q≥10 to perform; fast fusion neutrons could be used to partially transmute long-lived radioactive waste from fission reactors into less harmful, short lived waste that is easier to dispose of; and, last but not least, contrary to a conventional fission reactor a MSHT device would be sub-critical—neutrons would not be provided by the chain reaction but by an external source (the fusion core).
MSHTs would eliminate what Academician Velikhov calls "vital risks" such as those posed by conventional fission reactors. "Ordinary risks," he claims, "are manageable in terms of acceptance by public opinion."
In the discussion that followed the presentation, some argued that the circulation of molten-salt in the blanket would be quite difficult to design and manufacture. True, he agreed, but in "pure fusion" as with hybrids, challenges abound and no one can bet on which could be operational first.
Click here to view Academician Velikhov's presentation.
The technical specifications for six systems were contained in two Procurement Arrangements. Included was the diagnostic engineering of two upper and one equatorial port and diagnostics that will monitor, amongst other things, the plasma electron density, electron temperature and divertor surface temperature.
One of the diagnostics is based on the principles of interferometry and will use a 10.6-micrometer CO2 laser to probe the plasma and determine the average number of particles per unit volume. Another will use the electron cyclotron emission from the plasma filtered at various magnetic fields in a way akin to that used in medicine's magnetic resonance imaging. This will report the temperature at precise positions deep inside the hot ITER plasma—a plasma easily in the region of 200 million degrees Celsius. A third system will use the infrared emission from the divertor, or lower area in the vacuum chamber, to determine the temperature of the surface. This is similar to the way in which heat loss from buildings is measured. The divertor surfaces have to handle high heat loads from the plasma and need to be kept well below the melting point of the plasma-facing material, e.g., tungsten.
All of the systems will provide measurements that are used to control the plasma. This is an important aspect of optimizing the ITER performance and achieving good quality and long plasma discharges.
The Memorandum of Understanding describes the general principles of how both the ITER Organization and European Domestic Agency, F4E, will cooperate in the purchase of the diagnostic port plug support structures from a common manufacturer. This cooperation will extend to all diagnostic port plugs over the coming months. "This is an important step that aims to reduce the cost to the overall project by bulk ordering of components," explained Dr. Filhol, ITER Department Head at the European Domestic Agency. These port plug structures represent the frames that hold all the diagnostic components that will be used to extract the signals from the plasma through carefully designed labyrinths.
The Eleventh ITER Council meeting at ITER Headquarters last week was an excellent opportunity to sign all the documents. "Moving these Procurement Arrangements forward represents an important milestone in maintaining the project schedule," says Ned Sauthoff, head of the US ITER Project Office.
The eighth meeting of the ITER Council Test Blanket Module (TBM) Program Committee took place in Cadarache on 5-6 November to discuss the program's status and to define the short-term steps that need to be performed in order to keep to the present baseline schedule for the TBM Program.
The TBM Program Committee meets twice a year to govern the implementation of TBMs and associated systems in ITER and to report to the ITER Council. Several items are discussed at each meeting such as the status of the TBM-related activities within the ITER Organization, those with the ITER Members, and the status of corresponding milestones.
Following the endorsement of the generic TBM Arrangement by the ITER Council at its last meeting in June 2012, this eighth meeting focused on the steps that need to be performed within the next few months. The upcoming year will be an important one for the TBM program: the final version of the Preliminary Safety Report for each Test Blanket System (TBS) must be prepared by May 2013, and preparations and negotiations on each of the six specific TBM Arrangements are planned before the end of 2013.
Concerning the specific TBM Arrangements, participants stressed that an estimated six months will be necessary between the reception of the first draft by the ITER Organization and the official signature. Therefore, most draft documents are expected to be received by the ITER Organization by mid-2013.
The TBM Program Committee also discussed the report on the activities of the Test Blanket Program Working Group (TBP-WG) on radwaste that had been established in May 2012 and charged with the elaboration of a potential strategy for radwaste management. The Chair of the Working Group reported on the meetings held within the last few months with Agence ITER France (AIF), the official entity in charge of the future ITER radwaste management on behalf of the Host state France. Some issues have been identified and discussions will continue in the next few months to develop management options. The TBM-PC suggested an evaluation of the feasibility of transporting irradiated materials for Post Irradiation Examination (PIE).
The outcome of the eighth meeting of the Test Blanket Module (TBM) Program Committee was reported to the ITER Council last week.