ITER blanket technology approved

Apr 25, 2013
The ITER machine with its 440 blanket modules.

( —The design of the ITER blanket system, a crucial technology on the way to fusion power, has been approved and is now ready to proceed to the manufacturing stage. "The development and validation of the final design of the ITER blanket and first wall technology is a major achievement on our way to deuterium-tritium operation—the main goal of the ITER project," says Rene Raffray, in charge of the blanket for the ITER Organization. "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 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 - operation, but also an approach to attaching the modules which is far from trivial when considering the enormous electromagnetic forces.

The first wall is made out of shaped "fingers." These fingers are individually attached to a poloidal beam, the structural backbone of each first wall panel through which the will be distributed.

Each module consists of a shield block and first wall, together measuring 1 x 1.5 metres and weighing up to 4.5 tons.

Depending on their position inside the vacuum vessel, these panels are subject to different heat fluxes. Two different kinds of panels have been developed: a normal heat flux panel designed for heat fluxes of up to 2 MW/m2 and an enhanced heat flux panel designed for heat fluxes of up to 4.7 MW/m2.

The enhanced heat flux panels are located in areas of the with greater plasma-wall interaction and they make use of the hyper-vapotron technology, which is similar to that used for the divertor dome elements. All panels are designed for up to 15,000 full power cycles and are planned to be replaced at least once during ITER's lifetime. A sophisticated R&D program is currently under way in Japan for the development of remote handling tools to dismantle and precisely re-position the panels.

The ITER blanket system provides the physical boundary for the plasma.

Due to the high heat deposition expected during plasma operation—the blanket is designed to take a maximum thermal load of 736 MW—ITER will be the first fusion device with an actively cooled blanket. The cooling water is fed to and from the shield blocks through manifolds and branch pipes.

Furthermore, the modules have to provide passage for the multiple plasma diagnostic technologies, for the viewing systems, and for the plasma heating systems.

Because of its low plasma-contamination properties, beryllium has been chosen as the element to cover the first wall. Other materials used for the blanket system are CuCrZr for the heat sink, ITER-grade steel 316L(N)-IG for the steel structure, Inconel 818 for the bolts and cartridges, an aluminium-bronze alloy for the pads that will buffer the electromechanical loads acting on the segments, and alumina for the insulating layer.

The procurement of the 440 shield blocks is equally shared between China and Korea.The first wall panels will be manufactured by Europe (50%), Russia (40%) and China (10%). Russia will, in addition, provide the flexible supports, the key pads and the electrical straps.

The preparation of the Procurement Arrangements will now be launched leading to the fabrication hand-over starting at the end of this year. The assembly of the ITER blanket system is scheduled for the second assembly phase of the ITER machine starting in May 2021 and lasting until August 2022.

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User comments : 7

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1.8 / 5 (5) Apr 25, 2013
Excellent progress.
The only bit they didn't mention is the lithium titanate breeder blanket sections- to produce the tritium for all those 15,000 tests.
Also I've not seen an explanation why the Princeton deliberate lithium 'contamination' of the plasma, which they found greatly improved containment, has not carried forward into ITER's design:-
not rated yet Apr 25, 2013
"the hyper-vapotron technology".

Never heard of it before, but localized controlled vaporization/vapor quenching seems an ingenious energy transfer technology, reminding of heat pipes in simplicity. Too bad you get bubbles, they are always wear and tear (cf cavitation).

@ENS: I thought the breeder technology was a later test development. First priority would be understanding the measurements, then the reactor.

I wonder if and when they will test the necessary fissile breeder neutron technology? At a guess it would be the next generation prototype technology development, even if they develop the necessary automatic remote handling now.
5 / 5 (2) Apr 25, 2013

It would be the height of irony if someone came up with a much simpler and cheaper controlled fusion device before this behemoth is ever finished.

not rated yet Apr 25, 2013

It would be the height of irony if someone came up with a much simpler and cheaper controlled fusion device before this behemoth is ever finished.

Search for "General Fusion". Fusion created by a symmetrical shock-wave powered by steam pistons, contained in a liquid lead and lithium blanket.
1 / 5 (4) Apr 25, 2013
It would be the height of irony if someone came up with a much simpler and cheaper controlled fusion device before this behemoth is ever finished.

multiple colliding-beams is to be much more promising.
1 / 5 (1) Apr 26, 2013
I hope they capture and recycled the significant wasted energy from the cooling systems for other uses. Heck , it could cut millions in running costs of the whole complex.
1 / 5 (4) Apr 26, 2013
In the real thing the cooling system will be the power output to turn the turbines.
Just like any reactor power plant.
'ITER' will just dump the heat locally 'DEMO' should send it to the grid.

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