Electrical infrastructure taking shape
On either side of the Tokamak Complex, construction is advancing on electrical buildings that will play key roles in distributing and safeguarding power to the ITER site while also establishing standards for future fusion plant infrastructure.
“The scope of the electrical infrastructure can sometimes be underestimated, but it’s crucial because the power supply needs to be guaranteed to protect equipment and meet nuclear safety functions,” says Mariano Bennati, an electrical engineering officer with the department that is overseeing the design, Engineering Services. “It’s a good challenge because it’s not just designing the technical aspects of the buildings and equipment, it’s also designing the way the buildings and equipment will be qualified so the site can be authorized to operate by the French nuclear regulator ASNR.”
Electrical power arrives at the ITER site via a 400 kV cable from the French national grid. It then passes through transformers and is divided into two electrical systems: the steady state electrical network (SSEN) for ITER’s conventional systems and facilities, and the pulsed power electrical network (PPEN) that will power the tokamak’s superconducting magnets and heating systems.
The Electrical Engineering Division is currently overseeing the construction of four buildings and associated structures that are essential for the SSEN system:
* Emergency Power Supply buildings 44 and 45 are categorized as “SIC” (safety important components) because they will back up electricity to infrastructure that can impact nuclear safety such as the cooling water system, the central safety system, and radwaste treatment and storage. These buildings will be stocked with hundreds of batteries that can provide instantaneous electricity through the uninterruptable power supply (UPS) so the installation remains safe if there is a sudden loss of the main power supply. In such a situation, the batteries would act as an electrical bridge until emergency generators kick in.
* Emergency Power Supply buildings 46 and 47 are categorized as “IP” (investment protection). The electrical loads protected by these buildings are not related to nuclear safety, but any loss of power would impact the project and possibly create long out-of-service periods.
* Load centres and switch gears. Along with the buildings, the Division is also overseeing the construction of load centres LC1 and LC2, which are centralized electrical distribution points, and two medium voltage switch gears (MV4 and MV5) that transform power from 22 kV to 6.6 kV so it can be used by the different facilities. There are also two other load centres—LC15 and LC16—that can supply emergency power to the most critical systems as backup.
Each building, load centre, and switch gear is redundant—creating the Train A and Train B electrical systems—in case any part of the infrastructure fails. They have been set up in a mirror arrangement, with one pair of buildings located on the north side of the Tokamak Complex and the other pair located to the south.
Advancements made in this area will be a valuable asset for other fusion projects with comparable infrastructure, as it is one of the first times nuclear qualification and manufacturing are being done for electrical equipment such as the medium voltage switchgear, dry type transformers, and cast resin low-voltage busbars.
The four buildings and associated infrastructure are the responsibility of Fusion for Energy, the European Domestic Agency for ITER. Ansaldo Nucleare and Monsud have been contracted for the electrical systems and the buildings. Construction began in 2020 and is scheduled to be finished by 2028.