We don't often hear of tritium-tritium operation. Can you explain? The huge database that the European tokamak JET has accumulated, both during the deuterium-tritium campaigns of the 1990s and in more recent operations with an ITER-like beryllium inner wall and tungsten divertor, is of unique value to ITER.   Last week, safety specialists from JET and the ITER Organization met at ITER Headquarters to discuss the sharing of this trove of information, identify and transfer the ITER-relevant data, and strengthen communication between teams at the European machine and the international project. Newsline seized this opportunity to sit with JET exploitation manager Lorne Horton, and Xavier Litaudon—head of the EUROfusion ITER physics department.¹   What's happening at JET these days?   We have been in shutdown since November last year and will remain in shutdown until September, at which time we will be in a configuration to operate in deuterium-tritium. Of course, this doesn't mean that we have been idle: we are busy maintaining and refurbishing equipment, calibrating diagnostics, removing and analyzing samples—asking, for example, how much fuel, how much dust was retained from recent operations?   We are also building the infrastructure to accommodate a shattered pellet injector, currently being manufactured by Oak Ridge National Laboratory (US), which will allow researchers to study disruption mitigation scenarios.   In parallel, we are deeply involved in the analysis of the highly successful 2016 campaign and in preparation for deuterium-deuterium and tritium-tritium operation in 2018, and deuterium-tritium (DT) in 2019-2020.   For the preparation of these challenging experimental campaigns, we have set up a set of analysis and modelling campaigns where all EUROfusion scientists (around 300 involved) are welcomed to work jointly at the Culham site during dedicated weeks.   We don't often hear of tritium-tritium operation. Can you explain?   The mass of the particles plays an important role in the stability and in the energy transport within the plasma. We want to have a deeper understanding of these phenomena before going into nuclear operation with the deuterium-tritium mix.   In a nuclear plasma, deuterium (mass 2) makes up half of the particles and tritium (mass 3) make up the other half, which translates into an average particle mass in the plasma of 2.5.   In order to understand the behaviour of this nuclear plasma you can extrapolate from what you observe in pure deuterium plasmas. This is what fusion research does on a routine basis and what we will also be doing in 2018. But extrapolations lack accuracy. We'll get much more precise data by implementing a pure tritium plasma and interpolating the results from both deuterium and tritium plasmas.   But tritium is expensive ...   Indeed. We will have 60 grams of tritium on site. By recirculating it about a dozen times in our tritium plant, we'll be able to inject a total of approximately one kilogram throughout the whole campaign. But the actual burn, and hence the total consumption, will be tiny.   JET's beryllium-clad inner wall (in green) has many advantages, but it's much less forgiving than the previous carbon wall. Test campaigns run at JET permit scientists to verify the physics models of plasma-wall interaction and modelling tools for ITER. Full-fledged deuterium-tritium operation is set to begin in late 2019. What has changed since JET's last DT campaign in the 1990s?   A quarter century ago, JET was equipped with a carbon wall. In addition, the focus was mainly on achieving maximum fusion power, even if it was transient. Since 2011 JET has operated with an ITER-like wall (tungsten and beryllium plasma-facing components) and has acted as a test bed to verify the physics models of plasma-wall interaction and modelling tools for ITER.   The nature of first wall materials affect plasma performance; the major challenge remains to sustain high fusion performance (10-15 MW of fusion power during 5s) in an ITER-relevant operational mode of operation.   However, the fact that our coils—contrary to those of ITER—are not superconducting still imposes a limitation of approximately 5 to 6 seconds on the duration of plasma pulses.   In 1997, with 20 MW of heating power we obtained 4 MW of steady fusion power during 5 seconds.   In the campaign we are presently planning, we'll have 40 MW of heating power and we are aiming for power levels in the range of 10 to 15 MW for 5 seconds. In terms of fusion energy produced, the difference is considerable.   What will the ITER-like wall change in the context of the DT campaign?   A beryllium-clad inner-wall, like ITER's, has many advantages. But it changes everything relative to previous experiments with a carbon wall. Because beryllium is not as tolerant to high-power long-duration pulses, it makes things more difficult.   But results from our recent campaign make us confident. What we have learned and what we will continue to learn with the upcoming operation will save significant time on the way to ITER's deuterium-tritium operation.   ¹ The Joint European Torus (JET) is the largest tokamak in the world and the only one with deuterium-tritium capability. It is located at Culham, UK and operated by the Culham Centre for Fusion Energy (CCFE) on behalf of its European partners, under the EUROfusion consortium.

What weighs more than 700 small cars, stands taller than the Louvre Pyramid, and can embrace the cross-section of the ITER Headquarters building in its wingspan? The largest tool in ITER's assembly arsenal. This giant yet highly precise piece of technology has passed factory acceptance tests in Korea and is ready to take to the sea. A milestone achieved at Taekyung Heavy Industries (THI) in Changwon in early May brings the ITER Project one step closer to the start of its tokamak assembly phase.   The first vacuum vessel sector sub-assembly tool (SSAT) has demonstrated all functional performance in factory acceptance tests conducted in the presence of observers from the ITER Organization and the Korean Domestic Agency. The tool has now been taken down and packed for shipment to the ITER site—over 800 tonnes of metal plus auxiliary components packed into 90 shipping crates that will ship in five batches.   The first batch, containing lower elements plus all hydraulic activators and accessories, shipped this weekend and is expected to arrive on 30 June.   From their location in one area of the ITER Assembly Building, two identical SSAT tools will support the weight of 440-tonne vacuum vessel sectors within the triangle formed by three large columns, as lateral wings slowly rotate thermal shielding and two 310-tonne toroidal field coils into place. The challenge of the operation—reflected in the careful design and prototyping phase of the tools—is in assembling large and very heavy components to extremely unforgiving tolerances. (More on the tool's hydraulic system and actuators here.)   The first of the twin tools was manufactured in segments by the Korean contractor THI and then assembled completely at the factory for inspection and testing (see the video in this issue). Lessons learned on the realization of the first tool will serve in the fabrication of the second, which has started now in Korea.    In a ceremony held on 11 May the head of the Korean Domestic Agency, Kijung Jung, celebrated the completion of the first tool: "This is a step forward for procurement efforts for ITER in Korea and for the project as a whole. Like all ITER Members, Korea's participation in ITER contributes to our industrial and scientific capabilities and positions our nation to be a future player of consequence in the promising domain of fusion."    The months ahead will be a busy time in the Assembly Hall and adjacent Cleaning Facility at ITER. On the reinforced slab that has been prepared for the SSAT tools, contractors have already embedded anchor bolts onto which the rail base plates will be mounted when access to the Assembly Hall becomes possible in mid-August. A few metres away, in the Cleaning Facility, a large storage area is in the planning stages for the components that will arrive starting late June from Korea. In the shape of a 10-metre tall enclosed "box," the storage unit will protect the SSAT components from ambient dust and the other activities underway in the building. When access is possible for the first assembly operations (mid-September), Taekyung Heavy Industries, as the main contractor, and subcontractor CNIM (France) will proceed by first installing the rail components on the basemat and then moving on to assembly of the structural elements of the tool.   Three months will be necessary, meaning that by the end of the year the first SSAT tool will be standing tall in the Assembly Building.   

For a spectacular flyover of ITER's largest assembly tool, scroll down ... At the Taekyung Heavy Industries facility, in Changwon, Korea, a drone flies over the finalized vacuum vessel sector sub-assembly tool (SSAT), the largest tool in ITER's assembly arsenal (see article).   Click here the view the video.    

They are young, joyful and extremely motivated. The Monaco Fellow Cuvée 2017 has just arrived and is getting settled.  Like their 20 illustrious predecessors these five postdoctoral researchers will be staying at ITER for two years under the sponsorship of the ITER-Monaco Partnership Arrangement, gaining experience and pursuing research in their respective fields of specialization. Ryan Sweeney (US), here since November 2016, works on disruption mitigation.  "Alternative energy research and fusion are part of the ultimate solutions to the ever-growing energy problems of the world and it is great to be able to contribute to that. Being at ITER is for me a fantastic opportunity for professional growth but also for personal development because I'll be able to learn about French language and culture." Di Hu (China), who specializes in disruption-related macroscopic MHD (magnetohydrodynamics), has been an enthusiastic member of the team since October. "It's a great opportunity to get involved and gather experience in my field. And on a more personal level, it's fun to be part of and learn from the international fusion community here at ITER." Toon Weyens (Europe) arrived early this year to work on 3D stability with a good idea of what to expect because he had already spent several months at ITER as part of his PhD. "It is really motivating to contribute to such an outstanding scientific endeavour; but as a community, ITER is also an amazing and inspiring place to be." Aneeqa Khan (Europe) has worked on material erosion/migration and on fuel retention in ITER since joining ITER in December 2016. "This is the biggest fusion project in the world and it's where the action is right now!  The best people in my field are right here and the strong connections with the other fusion institutes in the world make for an atmosphere of excellence." Himank Anand (India) is the last of the Monaco Fellows to take up his post. He works on controlling the shape and position of the plasma and on the heat flux on the vessel wall. "ITER is definitely the best place to be to work on fusion and an excellent place to exchange ideas with the best people in all fusion-related fields."

Standing 3.4 metres tall and weighing eight tonnes, the pre-production ITER cryopump cuts a striking figure as it waits for final assembly in the laboratory of the German company Research Instruments. But it is not its imposing size that makes this pump unique, it is the technology inside. In order to maintain ultra-high vacuum inside the ITER vacuum vessel during operation and to evacuate residual gas from the fusion reaction, a 200-kilogram valve has to move along a 1.8-metre-long shaft and lock in about ten seconds with a precision of 0.1 mm to tighten the all-metal seal that is required for the radiation environment. All this faithfully ... over the more than 30,000 cycles of the machine's lifetime.   The complex pumps have been tailored for the very specific applications and requirements at ITER. All are based on cryopanels, cooled with supercritical helium and coated with activated charcoal as sorbent material. Research and development has shown that charcoal from finely ground coconut shells has the right density and porosity for imprisoning the gas particles in ITER. In total, six cryopumps will be installed around the ITER vacuum vessel. Like a synchronized ballet they will pump and rest in turn, guaranteeing continued gas evacuation during plasma discharges. While four of the six pumps will always be on duty, the other two will be separated from the vacuum vessel and given 10 minutes to regenerate. This is a necessary step, because over the long plasma pulses ITER is designed for (up to 3,000 seconds), the accumulation time of hydrogen to the charcoal-granule absorber panels inside the pumps has to be limited for safety reasons.   During their "regeneration phase," the pumps will be disconnected from the torus vacuum system. The cryopanels inside the pump will be "heated up" (away from their cryogenic operating temperature of 4 K) to 100 K, permitting the release of hydrogen that has been accumulating on the charcoal-granule coating. Then the torus cryopump will be connected to a roughing pump to extract the hydrogen and send it back to the Tritium Plant, where the precious fuel will be recycled. Thus regenerated, the pump will be cooled back down to its cryogenic temperature again and return to join the band of six.     Now in their final stages, the different assemblies that form the pre-production cryopump are taking shape in the factories of the consortium formed by the German firm Research Instruments and the French company Alsyom. (The ITER cryopumps are part of Europe's contribution to ITER.)   This week, the pre-production cryopump will travel to Pro-Beam in Berlin where the pump plug will be welded to the casing, and assembly activities will be completed for the valve unit. Once finalized, the whole assembly will be delivered to the ITER Organization for the installation of the valve control system and vacuum gauges and for final acceptance tests.   

After the success of the first fusion writers' edition of Fusion in Europe last year, the magazine is again looking for ambitious volunteer writers for the 2017 autumn issue. Fusion in Europe is the regular publication of EUROfusion, the European Consortium for the Development of Fusion Energy, which manages European fusion research activitites on behalf of Euratom. Applicants should be enthusiastic and ambitious, with ideas about how to share the promise of fusion with the world. The deadline is 21 June. For more information, please visit this link.

Scientists now have a better understanding of the factors leading to steel degradation and of the ways to improve the design and development of key components, such as the ITER breeding blankets—where tritium fuel will be produced from the interaction of fusion neutrons with lithium. In a unique test facility at the Italian National Agency for New Technologies, Energy and Sustainable Economic Development (ENEA) in Brasimone, candidate steels were exposed to liquid lithium in order to measure degradation (corrosion and/or erosion) over time. Two types of reduced activation ferritic martensitic (RAFM) steels under consideration for fusion applications—EUROFER97 and F82H—were tested at ENEA's LiFus6, built for the IFMIF/EVEDA project (IFMIF will carry out testing and qualification of advanced materials under conditions similar to those of a future fusion power plant/EVEDA is advancing the engineering validation of key IFMIF components and systems). IFMIF/EVEDA is developed jointly by Europe and Japan in the framework of the Broader Approach agreement, which covers fusion R&D activities that are complementary to ITER and the next-stage device DEMO. Read more about the successful LiFus6 test campaign on the European Domestic Agency website. Image: Celebrating at ENEA: IFMIF/EVEDA Project Committee members and representatives of contributing laboratories.