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A general plan for the repair work at the ITER thermonuclear project has been drawn up - it is necessary to replace 23 km of cooling pipes and build up hundreds of kg of metal at the seams.
It is already known that the defects in the design of individual components revealed during the assembly of the ITER fusion reactor will force the launch of the first reaction to be postponed for months or even years. And although the details of the repair work and their estimates will have to be clarified more than once, the picture of actions is already clear and the ITER team has begun to implement it. The reactor will be repaired and built!
First, the project began preparing heat shields to replace the cooling pipes. In total, the working chamber of the reactor will cover 27 panels, which is 23 km of pipes. The previous technology of welding pipes on the panel led to the appearance of microcracks. This was facilitated by chlorine residues that got into tiny pockets during the welding process, which led to corrosion, as well as metal stress after welding, which ruptured the wounded metal of the pipes.
Now specialists are tearing off pipes from panels and are working on new welding technologies. Even the option of fixing pipes with clamps was considered, but it was discarded as too complicated and unreliable. All cooling pipes for already produced panels will be fabricated and welded anew and most likely some new panels will also be made in reserve. A tender for these works will be placed in early February, so that a contractor can be found in March and start repair work.
With deviations in the geometry of the nine sectors of the vacuum chamber, everything will be more complicated. Each of the sectors was assembled from three parts. This is what led to deviations in the geometry of the sectors after welding three parts into one product. These deviations are different for each sector. For example, in order to bring sector No. 6 (already installed in the reactor shaft) to the required tolerances, approximately 73 kg of metal will have to be built up along the perimeter of the joints. Sector #1(7) will require a build-up of 100 kg of metal, and for the most affected of the three measured sectors of sector #8, as much as 400 kg of metal.
To build up metal at the place of future welds, each sector will have to be freed from the same heat shields and other equipment that will interfere with the work process. To increase the sectors will be placed on special platforms. In this case, sector No. 6 will have to be removed from the mine, which is also a rather complicated operation, because each of the sectors weighs 440 tons (the height of a five-story building and the weight of an Airbus A380, as ITER representatives characterize these products).
The contractor for carrying out restoration work on the sectors of the working chamber will be selected before the beginning of summer. Together with ITER, the state French regulator in the field of nuclear energy will work on this. The technology will be tested on a variety of samples, and after completion of work, all seams will be checked in full by non-destructive testing. The work ahead is quite complex, but quite feasible.
“There is no scandal here,” said ITER Director General Pietro Barabaschi. “Things like that happen. I've seen many similar problems, and much worse..."