ITER completes weld inspections on vacuum vessel sector #1 ahead of tokamak pit assembly

Vacuum vessel sector #1 wrapped in lead shielding bags for X-ray radiography of bevel joint weld repairs, ensuring RCC-MR compliance before tokamak pit assembly

(Image courtesy of ITER)

ITER teams repaired bevel joints on vacuum vessel sector #1 to meet RCC-MR nuclear construction code requirements. More than 20 weld passes built deposits tens of millimetres deep across test areas, each verified by X-ray radiography penetrating steel to similar depths. Teams surrounded the sector with lead-filled bags weighing 17 to 24 kilograms. Every person on site wore a passive dosimeter readable after the fact and an active dosimeter for live radiation readouts. Testing ran at night or weekends with the surrounding area cleared.

Since 2024 engineers corrected geometric deviations in bevel joints where the nine vacuum vessel sectors join in the tokamak pit. Restoring joint geometry by filling low regions or grinding excess material set the stage for assembly. The radiographic program proved repair welds met code. Sector #1 is the fifth sector to undergo this radiographic testing process. Two earlier tests confirmed repairs on accessible regions. Held vertically in sub-assembly tooling the final bevel areas opened for inspection and testing proceeded there.

ITER Radiation Safety Coordinator Miguel Dapena-Febrer oversees radio-protection for these tests. Powerful X-ray generators demand nighttime or weekend scheduling under specific conditions to limit exposure. Momentum Construction Manager Thomas Antonini oversaw operations. “All preparations went smoothly and the testing has started successfully,” he said, crediting experience from earlier sectors. The process supports the assembly schedule.

Technology advanced since radiographic work began on the cryostat base in 2016. Gammagraphy took around four hours per film. Current X-ray generators cut that to one hour. In-pit sector module welding will use linear accelerators dropping exposure to as little as 10 minutes, though shielding must scale up for higher output.

Cleared results on sector #1 advance the vertical assembly sequence to tokamak core stacking. With sector modules #7, #6, and #5 installed during 2025 and #8 lowered into the pit on 29 January 2026 as the fourth, each sector clearance keeps global fusion timelines on track.

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