Good news from the icy front: On 11 March a team from Oak Ridge National Laboratory (ORNL) led by Larry Baylor, Steve Meitner and Steve Combs successfully produced the first deuterium ice using a twin-screw extruder. This new prototype extruder is 1/5 the size of the device that will be required for ITER, which will be capable of injecting an infinite number of pellets into the ITER plasma. It is the first step towards a pellet injector feeding particles deep inside the plasma.
The pellet injection system has two main experimental objectives: deep plasma fuelling to control plasma density and burn, and pacing of the edge instabilities called ELMs. The ITER pellet injection system is based on the gas gun technology originally developed in the US and continuous screw extruder technology originally developed in Russia. The new twin screw system developed at Oak Ridge will be capable of producing ice at a throughput of more than 100 Pa m3/sec.
Cylindrical pellets are cut from the different species of ice ribbons (hydrogen, deuterium, tritium, impurities or their mixture) by the sharp edge of thin wall tubes. Then a short pulse of propellant gas (hydrogen or deuterium up to 30 bar), accelerates each pellet up to 300 m/s. For the plasma density and burn control, pellet injection (~90 mm3 and 16 pellets per second maximum) from the high field side (inner wall) is provided by a dedicated flight tube. For the ELM control, smaller pellets at high frequency (~30 mm3, up to 40 pellets per second) are delivered through a low field side (outer wall) flight tube.
Two pellet injectors will be installed as the start-up machine configuration for hydrogen operation. There will be a provision to upgrade the system to a six injector configuration for DT plasma operation. The next step will be developing a pneumatic gas gun capable of accelerating the pellets to a speed of 300 m/s to allow it to penetrate deep into the plasma and — in a further step - to mate it with the extruder to form the pellet injector.
Experts from IO, Europe, Korea, the Russian Federation and India responsible for the procurement of the ITER Vacuum Vessel have met in Cadarache to assess progress since the previous Vacuum Vessel procurement meeting in Korea this January. The main issue of this meeting was preparation for the Vacuum Vessel Procurement Arrangement (VV PA).
The Vacuum Vessel Procurement Arrangement signature is scheduled for June this year. "The preparation for the VV PA is progressing. Nevertheless keeping the schedule for this signature in June remains a challenge with regards to conformity assessment by the Agreed Notified Body (the ANB will perform the conformity assessment of the design and fabrication for pressure equipment ) and definitions of the design and interfaces," Kimihiro Ioki, IO Responsible Officer for the VV and Head of the Vessel Division, commented on the outcome of the three day meeting. The impacts of the ELM control coils, the blanket manifolds and the VV electromagnetic load updates on the VV PA are not fully known at this moment.
In preparation for the VV PA, the IO delivered a Vacuum Vessel 3D CAD model to the Members on 22 February and the Domestic Agencies generated 2D drawings for the VV technical specification. "This is an important achievement towards the VV PA. Cooperation between IO and Members is essential for the preparation of the Procurement Arrangement," Kimihiro Ioki emphasized. Furthermore, RCC-MR has been selected as the VV design and construction code.
Europe will supply seven vessel sectors and Korea two sectors and the equatorial/lower ports including Neutral Beam Liners and VV supports. The Russian Federation will supply the upper ports and India delivers the in-wall shielding for the vacuum vessel.
Safety is one of the most important topics for the ITER project and thousands of words have been written about it, including many by Susana Reyes. One of the nine Spaniards working at ITER at the moment, Susana comes from Madrid, where she studied industrial engineering at the Polytechnic, specialising in nuclear engineering. After two years at Lawrence Livermore National Laboratory in the United States as a graduate student doing her PhD she was offered a job in fusion safety.
To start with this was work on the "other" sort of fusion — inertial fusion using lasers, but she later transferred into the ITER community working on the Test Blanket Module and finally in 2006 she crossed the Atlantic to come back from the States to Cadarache to take up her current post in the Environment, Safety and Health Section of the Project Office.
Her task is to carry out accident analysis for ITER "reference events" — postulated incidents or accidents that could lead to potential radioactive releases - to demonstrate that the full range of events has been examined and that their consequences are acceptable for the workers, the public and the environment. This is a key part of the enormous document submitted to the French nuclear regulators at the beginning of this year, the Preliminary Safety Report (Rapport Préliminaire de Sûreté, RPrS)
It's comforting to note that "even in the very unlikely event of a worst-case scenario, the maximum accident dose to the most exposed individual would be below the natural background radiation dose received by that same individual over a year."
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On 13 March, a first kick-off meeting of the Financial Audit Board took place at the Château de Cadarache. According to the ITER Agreement, the Audit Board is to check the annual accounts of the ITER Organization. The board is formed by independant representatives from each ITER Member. The on site audit will be carried out between 21 and 25 April this year, the outcome will then be presented to the ITER Council in June.
It is happening and you can see it: the roadworks in preparation for ITER have started. Along the road between Cadarache and Vinon-sur-Verdon the works for burying the grey water pipeline have started.
The world's largest fusion experiment of the stellarator type is taking shape at the Greifswald branch of Max Planck Institute of Plasma Physics (IPP), Germany. The first milestone in the assembly of Wendelstein 7-X has been reached on schedule with the completion of the first two half-modules of the large-scale experiment: two-tenths of the inner core of the device are now ready and are being assembled. Industrial production of the components for Wendelstein 7-X is almost complete. Construction of the complex device will take about another six years.
Read the full article here.
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