Vacuum vessel sector
Lift and tilt
The first ITER vacuum vessel sector—as tall as a telephone pole and as heavy as 300 small cars—will soon be suspended several metres above the floor of the Assembly Hall and slowly "upended" mid-air from horizontal to vertical.
Once vertical, the first-of-a-kind component will be transferred across the Hall and docked inside of standing giant #2—one of two V-shaped sector sub-assembly tools anchored to the floor of the Assembly Hall. It will remain there for approximately five months, as other vacuum vessel sub-components (thermal shield panels and two D-shaped toroidal field coils) are rotated toward the sector and attached in order to complete the first "sub-assembly" of the nine-part ITER vacuum vessel.
The first ''upending'' operation is scheduled to take place this month. The 440-tonne vacuum vessel sector #6 will be lifted several metres off the ground and slowly ''tilted'' to vertical.
It has been seven months since the Korean Domestic Agency delivered vacuum vessel sector #6 to the ITER construction team. After final acceptance tests in September, the assembly teams worked to complete a number of installation tasks while the component was horizontal.
One of the main activities was the welding of small, cylindrical attachments called "bosses" to the outer skin of the sector. Because drilling is forbidden in nuclear pressure vessels like ITER's, instrumentation, instrumentation cables, and cable trays must be affixed to the attachments instead of to the vessel wall itself.
Approximately 700 ''bosses'' were welded to the outer skin of the sector in precise locations for the attachment of instrumentation, instrumentation cables, and cable trays. Over the workers' heads are some of the magnetic sensor cases, attached with four ''bosses'' each; elsewhere, we see the routing of cables and instrumention wires.
During this period, for example, assembly contractors installed 120 magnetic sensors*. "A number of steps were involved," says Yunxing Ma, from ITER's In-Vessel Diagnostics Section. "The metal cases containing the magnetic sensors were first welded to the bosses (four per sensor); then, the signal cables were routed and girded. We carried out electrical tests to verify signal continuity, and metrology to measure the as-installed positions of the sensors with respect to the datum." In a later phase, when the sector is in the Tokamak pit, the cables will be connected with the backend signal transmission network in order to link the sensors to the data acquisition system.
Sector #6 is now ready for the next phase in assembly. As a first step, it will be transferred in a horizontal position on its assembly frame to the purpose-built upending tool. Cables from the double overhead crane will descend to connect to the corners of the tool so that the upending frame (and load) can be lifted. As the component is suspended mid-air, cables on one side will be winched to bring vacuum vessel sector #6 to an upright position. Finally, as lift and alignment units are brought in to connect to the sector in its vertical position, the upending tool can be disengaged and lowered back to the floor.
Strong orange lashing lines will help to keep vacuum vessel sector #6 securely attached to its assembly frame during the upcoming lift and upending operations.
The ITER Newsline will have a full report.
* Densely distributed and spanning two full poloidal arrays, these sensors will deliver high-resolution magnetic field measurements across the entire vacuum vessel, providing key data for reconstructing the "magnetic field map"—critical information for plasma operation.
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