Tritium

Melting tungsten for a good cause

Over the past two years ITER physicists and engineers, along with many scientific colleagues within the fusion research community, have been working to establish the design and physics basis for a modified divertor—the component located at the bottom of the huge ITER vacuum vessel responsible for exhausting most of the heat and all of the particles which will continuously flow out of ITER’s fusion plasmas.  Our current Baseline begins plasma operations with divertor targets armoured with carbon fibre composite (CFC) material in the regions that will be subject to the highest heat flux densities. After the initial years of ITER exploitation, in which only hydrogen or helium will be used as plasma fuel producing no nuclear activation, this divertor is to be replaced. The replacement—a variant of the first component but fully armoured with tungsten—would be the heat and particle flux exhaust workhorse once the nuclear phase, using deuterium and then deuterium/tritium fuel, begins. In 2011 the ITER Organization proposed to eliminate the first divertor and instead go for the full-tungsten („full-W”) version right from the start. This makes more operational sense and has the potential for substantial cost savings. By June 2013, the design was at a sufficiently advanced stage and we were confident that the necessary tungsten high heat flux handling technology was mature enough to invite external experts to examine our progress during the full-W divertor Final Design Review.  But making a choice to begin operations with tungsten in the most severely loaded regions of the divertor is not just a question of having a design ready to build.  Tungsten, a refractory metal with high melting temperature (3400 Celsius), is a much more difficult material than carbon when it comes Czytaj dalej...

First design review within Test Blanket Module program

Last week the ITER project—and the worldwide fusion community—celebrated yet another premiere: the first conceptual design review within the Test Blanket Module (TBM) program, a key technology development paving the way to fusion power. It was not yet the turn of the tritium-breeding test modules to be assessed, but that of the components required for hosting them. During its operational phase, ITER will draw upon the global (civil) inventory of tritium, currently estimated at 20 kilos. But future fusion power stations would have to create their own supply of tritium. Part of ITER’s mission is to test different tritium breeding concepts proposed and developed by the Members … concepts that will enable future fusion reactors to produce their fuel within the machine (tritium self-sufficiency) and at the same time extract the heat produced by the fusion reaction and convert it into electricity. While six different tritium breeding concepts—the Test Blanket Modules—are currently in their pre-conceptual design phase, a group of experts lead by ITER Senior Engineer Guenter Janeschitz last week concluded the first design check of the modules’ frames and housings, as well as the dummy modules that will be needed to substitute for the actual TBM sets in order to close and seal the port plugs in the case of delayed delivery or in case replacement is required. Mario Merola, in charge of ITER’s in-vessel components, called the design review „a significant step forward toward the goal of testing tritium breeding technology.” The current strategy foresees that the dummy TBM sets and the frames shall be made of water-cooled 316-L(N) steel (ITER grade), a special metal that guarantees reduced activation when exposed to neutrons, no ferromagnetic effects and adequate mechanical Czytaj dalej...

In dealing with the press, openness is key

On 22 and 23 April, the ITER Organization welcomed 19 science journalists from the European Union’s Science Journalist Association (EUSJA). This was the result of an initiative taken jointly by the Russian journalist Viola Egikova, vice-president of EUSJA, and ITER Communication to present ITER and the project’s underlying fusion science and technology to a group of selected science journalists. The two-day program included a visit of the worksite and presentations by several ITER scientists and engineers on status of the project, plasma physics, the chemistry of tritium, etc. Interviews were also organized at the requests of the journalists. As Head of Communications, I believe it is essential to work with the press and to handle their requests as swiftly as possible, as there is still a huge information gap and major communication needs relative to ITER and fusion. In my opinion, the aim is not so much the information that you deliver but the openness and the dialogue that you establish (or make visible) … and  the respect for journalistic work. „Indeed, I was pleased to see the openness of the ITER Communication team,” said Amanda Verdonck, a free-lance Dutch journalist who participated in the EUSJA visit. „But I was really impressed by the scale of the project and the sophisticated scientific knowledge that has gone into the machine. And I will be further impressed to see all this functioning! Like your videoconference system — quite impressive to me!” Czytaj dalej...

Green light for ITER’s blanket design

After three days and 29 presentations, a comprehensive design review with probably the largest participation in the history of the ITER project was completed last week. More than 80 experts from the ITER Organization, Domestic Agencies and industry attended the Final Design Review of the ITER blanket system. „The development and validation of the final design of the blanket system is a major achievement on our way to deuterium-tritium operation—the main goal of the ITER project,” Blanket Integrated Product Team Leader (BIPT) and Section Leader Rene Raffray concluded at the end of the meeting, obviously relieved at the success of this tremendous endeavour. „We are looking at a first-of-a-kind fusion blanket which will operate in a first-of-a-kind fusion experimental reactor.” The ITER blanket system provides the physical boundary for the plasma and contributes to the thermal and nuclear shielding of the vacuum vessel and the external machine components such as the superconducting magnets operating in the range of 4 Kelvin (-269°C). Directly facing the ultra-hot plasma and having to cope with large electromagnetic forces, while interacting with major systems and other components, the blanket is arguably the most critical and technically challenging component in ITER. The blanket consists of 440 individual modules covering a surface of 600 m2, with more than 180 design variants depending on the segments’ position inside the vacuum vessel and their functionality. Each module consists of a shield block and first wall, together measuring 1 x 1.5 metres and weighing up to 4.5 tons—dimensions  that not only demand sophisticated remote handling in view of maintenance requirements during deuterium-tritium operation, but also an approach to attaching the modules which is far from trivi Czytaj dalej...

Fusion draws on Japanese traditions

The Japanese people have a long history of creating ceramics of great beauty and elegance. Now they are putting their skills towards the search for materials for future fusion plants — in this case not crafting elegant forms, but elegant solutions: ceramics are nearly impervious to tritium. In a colloquium delivered at JET last week, Assistant Professor Takumi Chikada from the University of Tokyo outlined promising progress in research into the ceramic coating, erbium oxide, which may prove to be a vital coating for use in tritium-carrying pipework. „Without solving this problem it will be impossible to operate a fusion reactor,” he stated. Because of its very small size, tritium tends to permeate through materials readily — an undesirable characteristic in a tritium processing plant, where tritium would be exposed to a large surface area as it passes through cooling, ducting and processing pipework.Assistant Professor Chikada’s results showed that a layer of erbium oxide only tens of microns thick on a steel surface could reduce permeation of tritium by 100 000 times. Erbium oxide was originally chosen as an insulation coating because it has a high thermodynamic stability and is resistant to liquid lithium-lead — a proposed blanket material for fusion plants, which is corrosive to many materials. Read more on the EFDA website. Czytaj dalej...

DivSOL wagon rolls EAST

With the EAST tokamak in the middle of an extended maintenance period—during which the ASIPP team in Hefei, China will take the audacious step of installing an ITER-like, full tungsten divertor in the upper part of the vacuum vessel by the end of this year—what better place to hold the latest in the series of regular meetings of the International Tokamak Physics Activity (ITPA) Topical Group on Divertor and Scrape-Off Layer physics. Known in ITPA circles as the DivSOL TG, this group focuses on issues of importance to ITER in the area of heat and particle exhaust from the tokamak plasma and the unavoidable plasma-surface interactions which occur at the plasma-materials boundary.  Plasma and materials physicists work together within DivSOL to address a host of questions, from movement of material by the plasma and tritium trapping in surfaces, to turbulent transport of heat in the plasma boundary and plasma-facing component lifetime under intense heat fluxes. In common with all ITPA groups, DivSOL is reactive to urgent ITER physics R&D issues and works to find answers to specific requests. One such example is the flurry of activity stimulated by the ITER Organization proposal in autumn 2011 to eliminate one of the two divertors planned for the first years of ITER operation, up to achievement of burning plasmas. The idea is to go the whole way with a single unit in which tungsten (chemical symbol W) would be the only material intercepting the majority of the tokamak heat exhaust. A single divertor would be a major cost saving to the project, but it is a calculated risk: W is a harder material to work with from the plasma point of view than the carbon fibre composite in originally planned first divertor. Finding out just how much of a risk, and making sure that a workable design with qualified technology Czytaj dalej...

ITPA DivSOL wagon rolls EAST

With the EAST tokamak in the middle of an extended maintenance period—during which the ASIPP team in Hefei, China will take the audacious step of installing an ITER-like, full tungsten divertor in the upper part of the vacuum vessel by the end of this year—what better place to hold the latest in the series of regular meetings of the International Tokamak Physics Activity (ITPA) Topical Group on Divertor and Scrape-Off Layer physics. Known in ITPA circles as the DivSOL TG, this group focuses on issues of importance to ITER in the area of heat and particle exhaust from the tokamak plasma and the unavoidable plasma-surface interactions which occur at the plasma-materials boundary.  Plasma and materials physicists work together within DivSOL to address a host of questions, from movement of material by the plasma and tritium trapping in surfaces, to turbulent transport of heat in the plasma boundary and plasma-facing component lifetime under intense heat fluxes. In common with all ITPA groups, DivSOL is reactive to urgent ITER physics R&D issues and works to find answers to specific requests. One such example is the flurry of activity stimulated by the ITER Organization proposal in autumn 2011 to eliminate one of the two divertors planned for the first years of ITER operation, up to achievement of burning plasmas. The idea is to go the whole way with a single unit in which tungsten (chemical symbol W) would be the only material intercepting the majority of the tokamak heat exhaust. A single divertor would be a major cost saving to the project, but it is a calculated risk: W is a harder material to work with from the plasma point of view than the carbon fibre composite in originally planned first divertor. Finding out just how much of a risk, and making sure that a workable design with qualified technology Czytaj dalej...

The Sun never sets on the CODAC empire

Every year in February, when almond trees begin to bloom in Provence, the ITER CODAC team releases a new version of the CODAC Core System. The 2013 edition (CODAC Core System v 4.0) is more robust, comes with a better operator interface, offers more features, and supports plant systems that need „fast control,” for example plasma control systems that have to react within a strictly defined period of time. „Version 3.0 did it okay,” says ITER Control System Division Head Anders Wallander. „Version 4.0 does it better.” CODAC (Control, Data Access and Communication) can be described as a software conductor that orchestrates the dialogue between the hundred-odd ITER plant systems …”the system of systems that makes one entity of everything” … the lingua franca that allows the magnets, blanket, tritium plant, cryostat and diagnostics to exchange signals and share information. Working for the ITER project here and abroad, 55 organizations (Domestic Agencies, fusion labs, contractors) are presently using the CODAC Core System. An infrastructure has been set up to distribute the software to these and future organizations and to keep track of versions used. Training and user support is also provided. The software package has recently demonstrated its efficiency on the Korean tokamak KSTAR and celebrated its „First Plasma,” so to speak, last June at the Frascati Tokamak Upgrade (FTU) project in Italy.  „The ITER CODAC system is truly becoming a world language,” says Anders. CODAC is already implemented and deployed to monitor the power consumption on the ITER site, providing the „power people” with a global view and data with which to charge the different contractors operating on site. „With these pilot applicatio Czytaj dalej...

Romanelli sees JET as "main risk mitigation" for ITER

On the afternoon last year when the European tokamak JET attempted first plasma after an 18-month shutdown, Associate Leader Francesco Romanelli remained in his first-floor office. „I wasn’t expecting the machine to perform so faultlessly on its first attempt,” he later explained. „Besides, things had a way of going wrong when I entered the room, so maybe it was better after all.” That anecdote and others were related by Romanelli at last week’s Inside ITER seminar, during which he gave a first-hand overview of the ITER-like wall campaign that has been running at JET since that first (very successful) day back in August 2011. Three thousand installable items and 16,000 tiles had been replaced in the machine (non-metal carbon tiles were replaced by the metals beryllium and tungsten) to equip JET with the same materials mix chosen for ITER. Romanelli reported in detail on the experimental results so far: demonstration of low fuel retention, tungsten divertor successfully tested, observations related to the dynamics of disruptions … „Overall, the operation of the ITER-like wall has been easier than expected, giving us the confidence that the fusion community is making the right choice for ITER. We see JET as the main risk mitigation measure in support of ITER.” The European Fusion Development Agreement is already looking ahead to other roles for JET—developing plasma scenarios in ITER-relevant configurations and testing the compatibility of the wall with the use of tritium. „JET can provide unique input in a number of technical and operational areas.” David Campbell, director of ITER’s Plasma Operation Directorate, agrees: „The crucial ITER-like wall experiment will give us insight—ahead of ITER operation—as to ho Czytaj dalej...

First four levels of Tokamak Complex now defined

The heart of the ITER facility will be the Tokamak Complex, comprising the Tokamak Building, the Diagnostic Building, and the Tritium Plant. The seven-storey Complex measuring 118 by 80 metres and towering 57 metres above the platform will contain more than 30 different plant systems including cooling systems and electrical power supplies, all having physical as well as functional interfaces. As you can tell from the configuration drawing there won’t be much extra room for manoeuvring. The house is pretty busy! In order to make sure that all the necessary pipes, ducts, structures, cable trays and penetrations are correctly defined before the pouring of the concrete, a Building Integration Task Force was created in April last year to go through the building floor by floor. All the required documentation has now been delivered for the basement level (B2), the lower level (B1) and the equatorial level (L1) according to the agreed schedule with the European Domestic Agency Fusion for Energy and the Architect Engineer ENGAGE. The upper level (L2) has also been reviewed and the data files will be handed over by the end of this month. The configuration for each level was reviewed in compliance with the safety files and the installation and assembly feasibility of the systems and components. The design also respects the requirements on the civil works such as radiation shielding, fire protection and sectorization, and confinement leak tightness. For the Level B2 slab, the detailed design of the rebar arrangement will be completed by F4E’s designer Engage by December followed by the review of all the embedded steel plates that will be cast into the concrete to support the heavy loads. About 55,000 such plates have been identified and tagged in the floors, walls and ceilings of the Tokamak Complex. The revi Czytaj dalej...

Tore Supra ready to go WEST

On the other side of the CEA fence, in Cadarache, sits a large tokamak which played an important role in the definition of ITER. Tore Supra, a CEA-Euratom device which began operating in 1988, was the first tokamak to successfully implement superconducting magnets and actively-cooled plasma-facing components. Over the past twenty-four years, Tore Supra has explored the physics of long-duration plasma pulses, reaching a record of 6.5 minutes in December 2003. In 2000-2002, Tore Supra was equipped with a new carbon-carbon fibre (CFC) „limiter” — the equivalent of the divertor in ITER — capable of withstanding an ITER-relevant heat load of 10 MW per square metre. This project, named CIEL for Composants Internes Et Limiteurs, demonstrated that, while CFC performs very well in terms of power handling and compatibility with the plasma, its use results in substantial erosion caused by the physico-chemical reactions between the carbon of the limiter and the hydrogen (deuterium) in the plasma. Further experiments in JET have confirmed these observations. Now, there are not many options when it comes to choosing the material of a divertor. Fifty years of experience in tokamak technology have narrowed them to two: it’s either CFC or tungsten, their respective advantages or disadvantages depending on the plasma regimes they are exposed to. (More here). In ITER, it was originally planned to begin operations with a CFC divertor and replace it with a tungsten one before the start of nuclear operation (deuterium + tritium) in 2026. After years of discussions, panels and reviews, a new plan was established and ITER is now considering doing without the first-phase CFC divertor. Indeed, substantial cost reductions would be achieved by installing a tungsten divertor right from the start and o Czytaj dalej...

One more step towards the final green light

On 29 July, a new milestone was reached in the licensing process of ITER. A little more than one month after being notified that our proposals on the Tokamak’s operational conditions and design fulfilled the French safety requirements, we have now received from the Autorité de Sûreté Nucléaire (ASN)  the draft of the Décret d’Autorisation de Création — the final green light from the French Authorities to create our installation. We are currently analyzing this draft and we will soon send back our comments to ASN. Then, a discussion will be organized with a college of ASN experts and at long last the final decree will be published — hopefully before the end of the year. This is a lengthy, complex, demanding — sometimes frustrating… — process. But I must say it is also a very good process. ITER is the first fusion installation that will receive a full nuclear licence. And this is very important, not only for us here at ITER but for the whole worldwide fusion community. We have always claimed that fusion is safe and in the past two years, we went through an exceptionally strict and challenging process to demonstrate that it is indeed. Now an independent body of experts, with a deserved reputation for being among the „toughest” in the world, is in the process of validating our claim. And again, this is a first: no fusion installation, not even JET or TFTR which, at one point implemented deuterium + tritium fusion, went through this process. Twenty-seven years have passed since President Reagan and Secretary Gorbatchev met in Geneva and laid the ground for the project of an international experimental fusion reactor „for the benefit of all mankind”. We all feel a deep satisfaction in seeing these 27 years of hard work and dedication now converging into a Czytaj dalej...