Millions of data points, one successful lift

Following the latest major lift operation that lasted nearly 30 hours and mobilized more than 100 people, tokamak sector module #1-the sixth of the nine modules to enter the tokamak pit-landed safely on the afternoon of Tuesday 28 July. The lift marked a double assembly milestone for ITER: two-thirds of the plasma chamber is now in place and the last of the Korean-manufactured vacuum vessel sectors has been installed.

"From the initial preparation of the sector module to the successful transfer to the tokamak pit, everything was carefully planned and executed," says Mathieu Demeyere, the principal construction manager who supervised the operation for ITER. "Thanks to the efforts of the many different teams involved in the process, we've achieved a notable milestone."

Sector module lifts at ITER are remarkable exercises in coordination as four shifts of crane operators, spotters, metrology experts, safety experts, supervisors, and engineers seamlessly perform their roles to ensure the operation goes smoothly. One of the key teams in this process works at the control desk to monitor the structural behaviour of the sector module during the critical periods when it is first lifted from the sector sub-assembly tool and when it descends the last 500 millimetres to its final position.

Each sector module is composed of a vacuum vessel sector, two toroidal field coils, thermal shields, and auxiliary components, with lifting equipment and stabilizing beams attached for the lift operation. Because the main components have different centres of gravity and are lifted progressively, there is a transition when the suspended mass is not aligned with the crane's lifting point and the load distribution changes. This creates a risk of undesired movements and components coming into contact.

To monitor this, the control desk uses dozens of specialized sensors and compares live readings with data from previous lifts and predicted values derived using finite element calculations. If there is unexpected behaviour, the lift is stopped, the issue is analyzed, and necessary corrections are applied.

"Many of the most important things happening during a sector module lift cannot be seen with the eye," explains Jordi Utges, a mechanical engineer for ITER contractor Arial Industries who has worked the control desk for the lifts of all six sector modules now in the tokamak pit. "This is why we must concentrate on the most critical values for each moment of the lift. Someone must always be watching the numbers."

These numbers are generated by strain gauges that are used to calculate the forces acting on the components, load cells on the lashing or bracing elements, laser sensors that measure clearances between elements, inclination sensors that measure tilting, and load pins that measure the forces on connected loads. The devices are so precise that even small details, such as the flexibility of the glue used to attach a strain gauge, are considered in advance to ensure the data is accurate.

The sensors record data ten times a second, which results in millions of data points for the control desk team to decipher during the operation. In charge of wrangling this information with proprietary software and customized dashboards is Alessandro Vaccaro, an ITER assembly engineer who brings a background in graphic design and information technology to his work at the control desk.

"We've made the data friendly," says Vaccaro. "A dashboard isn't just about displaying information; it has to present the right information in a way the operator can understand instantly. We've learned that improving data quality is more useful than increasing data quantity."

For the most recent lift, the control desk began work in May by overseeing the installation of the sensors on the components and establishing baseline readings. After preparing data predictions and checklists, they installed their first control table at the base of the sector sub-assembly tool the week before the lift. From there, they monitored the sector module during the pre-lift operations and the crucial first movements on the morning of Monday 27 July.

After this first phase, spotters and metrologists surveyed the sector module as it moved through the Assembly Hall to the tokamak pit. Meanwhile, the control desk moved to the tokamak pit to oversee the load distribution and watch for potential clashes as the sector module landed.

With the transfer of sector module #1 now complete, it joins the five others- #4, #5, #6, #7 and #8 -that are already in the tokamak pit. A seventh sector module is expected to be transferred before the end of the year.